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Immunity, Vol. 10, 701–711, June, 1999, Copyright 1999 by Cell Press
Biochemical Association of CD45 with the T Cell
Receptor Complex: Regulation by CD45 Isoform
and during T Cell Activation
corrected upon reconstitution with CD45 (Trowbridge
and Thomas, 1994), it is likely that the predominant sub-
strates of CD45 in vivo would be involved in enhancing
TCR signaling cascades upon dephosphorylation. Sub-
strates that fulfill this requirement are the src family
David Leitenberg,*
†
Yvan Boutin,*
Dan Dan Lu,* and Kim Bottomly*
‡
*Section of Immunobiology
†
Department of Laboratory Medicine
Yale University School of Medicine
New Haven, Connecticut 06510 kinases lck and fyn, which are negatively regulated by
phosphorylationof thetyrosine atthe carboxylterminus.
Dephosphorylation at this site causes an increase in
kinase activity and frees the SH2 domain to interactSummary with other signaling molecules. CD45 regulation of lck
phosphorylation in vivo is supported by a number ofCD45 is the predominant transmembrane tyrosine
phosphatase in lymphocytes and is required for the independent studies demonstrating CD45 association
with lck (Schraven et al., 1991; Guttinger et al., 1992;efficient induction of T cell receptor signaling and acti-
vation. However, the regulation of CD45 activity and Koretzky et al., 1993), increased basal tyrosine phos-
phorylation of lck at the regulatory carboxy-terminal ty-substrate specificity are poorly understood. In the
present study, we demonstrate a basal biochemical rosine in CD45-negative cells (Ostergaard et al., 1989;
Burns et al., 1994), and decreased lck kinase activity inassociation of CD45 with the T cell receptor complex
that is regulated in part by CD45 isoform expression. a CD45-negative antigen-dependent T cell cloned line
(McFarland et al., 1993). In addition, cells transfectedFurther, maintenance of CD45/TCR association is dif-
ferentially regulated following TCR ligation with pep- with a constitutively active EGF-lck chimera were able
to reconstitute TCR signaling in a CD45-negative celltide: a partial agonist peptide induces CD45/TCR dis-
sociationwhile anagonist peptidepromotes sustained line (Duplay et al., 1996). The regulation of lck kinase
activity by CD45 in vivo appears complex, however,association in a CD4-dependent manner. These data
suggest that T cell receptor signaling pathways may since there are several examples of CD45-negative T
cells that actually have unchanged or increased lck ki-be modulated by altering access of CD45 to TCR-
associated substrates involved in T cell activation. nase activity (Ostergaard et al., 1989; Burns et al., 1994)
apparently due to dephosphorylation of a positive regu-
latory tyrosine at position 394 (D’Oro et al., 1996). Thus,
Introduction although it is clear that lck is a substrate for CD45 that
can enhance T cell signaling, it is uncertain if this is
Thetransmembrane tyrosinephosphataseCD45 iscom- directly related to lck kinase activity rather than CD45
posed of a large heavily glycosylated extracellular por- maintaining lck in an “open” configuration that enables
tion, which can exist as at least eight different isoforms interaction of the SH2 domain of lck with other phospho-
generated by alternative RNA splicing of exons encod- tyrosine-containing molecules (Sieh et al., 1993). Re-
ing the ectodomain, and a cytoplasmic portion with pro- gardless of the precise mechanism by which CD45 regu-
tein tyrosine phosphatase activity, which is required to lates TCR signal transduction, it is likely that regulation
generate efficient TCR signal transduction (reviewed in of the associations of CD45 with molecules involved in
Trowbridge and Thomas, 1994). In CD4
1
T lymphocytes, TCR signaling will have an impact on CD45 activity.
the expression of different isoforms of CD45 is regulated We hypothesized that different ectodomain isoforms
during thymic development (Lefrancois and Goodman, of CD45 may regulate substrate access to the tyrosine
1987; Hathcock et al., 1992), as well as during the gener- phosphatase domains by targeting CD45 to distinct ar-
ation and maturation of an immune response in the pe- eas in the membrane where it can associate with other
riphery (Akbar et al., 1988; Bottomly et al., 1989; Lee et molecules important in T cell signal transduction, alter-
al., 1990) and in different effector cell subsets (Luqman ing their phosphorylation status and modifying the TCR
et al., 1991; Rogers et al., 1992). The regulated pattern signal transduction pathway. In support of this hypothe-
of CD45 isoform expression suggests that the ectodo- sis, we and others have utilized CD45-negative T lines
main of CD45 may influence the activity of the cyto- transfected with individual isoforms of CD45 and shown
plasmic phosphatase domains. thatcells thatexpress the lowmolecular weightisoforms
In vitro studies have identified several potential sub- (e.g., CD45Null, aka CD45RO) of CD45 are more sensi-
strates for the CD45 tyrosine phosphatase that are in- tive to T cell receptor signaling than cells that express
volved in the signaling cascade following T cell receptor high molecular weight CD45 isoforms (e.g., CD45ABC)
ligation, including the src family tyrosine kinases lck and as measured by IL-2 production (Novak et al., 1994;
fyn, as well as TCR zchains and the ZAP 70 tyrosine McKenney et al., 1995; Leitenberg et al., 1996). We have
kinase (Mustelin et al., 1989, 1992, 1995; Furukawa et further shownthat the increased responsiveness to anti-
al., 1994). Since T cells from CD45-deficient mice and gen signaling correlates with the ability of individual low
CD45-negative T cell lines demonstrate profoundly im- molecular weight CD45 isoforms to associate with the
paired T cell activation and development that can be CD4/Tcellreceptor complexcompared tocells express-
ing high molecular weight isoforms (CD45ABC) in fluo-
‡
To whom correspondence should be addressed (e-mail: kim.
bottomly@yale.edu).
rescence colocalization studies (Leitenberg et al., 1996).
Immunity
702
Figure 1. Low Molecular Weight CD45 Iso-
form-SpecificAssociation with the CD4/TCell
Receptor Complex Is Independent of CD4
CD4 or TCR was induced to cap on BW cells
transfected with CD45RO using biotinylated
antibodies and an avidin-phycoerythrin con-
jugate. Association with CD45 was detected
using fluorescein-labeled anti-CD45. Dual-
color fluorescent analysis was done using the
ACAS 570 video laser cyometer. (A) indicates
representative pseudocolor images of capped
and cocapped cells with gradations in color
indicating changes in fluorescent intensity.
The arrows indicate the regions on the cell
where capping occurred. (B) represents an
average and standard deviation of the fluo-
rescent colocalization data in three indepen-
dent experiments in which CD3/TCR or CD4
was induced to cap in cells bearing CD45RO
or CD45ABC. In each experiment, a minimum
of 100 capped cells were counted, and the
percent of cells with CD45 colocalization was
determined.
However, it was unclear from the fluorescent localiza- of this hypothesis, the regulation of CD45/TCR associa-
tion following stimulation with specific antigen was al-tion experiments whether the association of the CD4/
TCR complex with CD45 was primarily dependent on tered dependingonthe potencyof theTCRligand. These
experiments utilized a previously described model systemthe TCR or CD4 since cap induction with anti-TCR or
anti-CD4 antibodies causes visible association of both in which transgenic CD4
1
T cells specific for a peptide
of moth cytochrome C (MCC) were stimulated with anCD3 and CD4 in addition to CD45 in a trimolecular com-
plex of all three molecules. Furthermore, it was unclear agonist peptideor avariant peptidethat actsas apartial
agonist (Boutin et al., 1997; Tao et al., 1997). Interest-if CD45 association with the CD4/TCR complex was
dependent on cell activation that may be a byproduct ingly, when cells were stimulated with antigen-present-
ing cells (APCs) pulsed with the variant peptide, theof cap induction or if there is a basal association of low
molecular weight CD45 with CD4/TCR in a macromolec- association of CD45 with the TCR complex was dis-
rupted, while cells stimulated with the agonist peptideular complex on resting T cells.
In the present study, we can demonstrate a basal maintained CD45/TCR association. These data provide
additional evidence that association of CD45 with thebiochemical association of CD45 with the TCR complex
that is independent of CD4 expression and is regulated TCR may be an important regulatory mechanism before
and during T cell activation.in part by the ectodomain of CD45. The basal association
of CD45 with the TCR is also detected in resting, primary
CD4
1
T cells isolated from the peripheral lymphoid or- Results
gans of mice. As noted above, the experiments in CD45
transfected cell lines suggested that association of Biochemical Association of CD45 with TCR
Complex Is Independent of CD4CD45 with the TCR is correlated with enhanced T cell
activation and IL-2 production; thus, the regulation of We have previously shown that low molecular weight
isoforms of CD45 are associated with the CD4/T cellCD45 association with the TCR may be an important
control mechanism formodifying TCR-generated signal- receptor complex in fluorescence colocalization studies
and that this was regulated by the variable ectodomaining cascades during priming of naive Tcells. In support
Regulation of CD45 Association with the TCR
703
of CD45 (Leitenberg et al., 1996). In order to determine
ifthis associationwasprimarily dependenton CD4orthe
TCR, we performed similar fluorescence “cocapping”
studies in which we assessed the ability of CD45 to
associate with CD4 in cells that lack CD3 and the ability
of CD45 to associate with CD3 in cells that do not ex-
press CD4. Figure 1 illustrates representative cocapping
data in which cells expressing CD45RO were induced to
cap using biotinylated anti-TCR or anti-CD4 antibodies
followed by avidin-PE, and the association of CD45 in
the cap was assessed using anti-CD45-FITC antibodies.
In Figure 1B, a summary of these data from three inde-
pendent experiments indicates no significant difference
in CD45RO association with the TCR in CD4
1
or CD4
2
clones. In contrast, when CD3
1
and CD3
2
clones of the
CD45ROtransfectants wereassessedfor CD45associa-
tion with CD4, there was a marked decrease in CD45/
CD4 association in the absence of CD3. These data
demonstrate that CD45 association with the CD4/TCR
complex seems to primarily depend on the presence of
the TCR since cells that do not express CD4 maintain
CD45RO association with CD3, while in the absence of
CD3 the association of CD45 with CD4 is diminished.
In order to confirm these findings and to determine if
CD45/TCR association was present on resting cells (in
the absence of TCR cross-linking to induce cap for-
mation),coimmunoprecipitation experiments were done
in which the TCR or CD4 was precipitated and the
presence of CD45 in the immunoprecipitate was as-
sessed by Western blotting. (Figure 2). In Figure 2A, the
Figure 2. Coimmunoprecipitation of CD45 with the T Cell Receptor
TCR was precipitated in cells expressing CD45ABC or
Complex
CD45RO with and without CD4. Regardless of whether
(A) Lysates of 10
7
BW5147 cells expressing either CD45RO (RO) or
the cells express CD4, CD45 is readily detected follow-
CD45ABC (A) or CD45-negative cells (-) were immunoprecipitated
with anti-TCR antibody (H57). After immunoprecipitation, the sam-
ing TCR immunoprecipitation. Although both CD45RO
ples were split and either applied to an 8% nonreducing SDS-PAGE
and CD45ABC are coimmunoprecipitated, it appears
and blotted with anti-CD45 or onto a 12% reducing gel and blotted
that more CD45RO is associated with the TCR than
with anti-z.
CD45ABC even though there is a similar amount of TCR
(B) CD45RO
1
cells were immunprecipitated with either anti-TCRb
zchain immunoprecipitated in each cell line, and each
(H57) or anti-CD4 (GK1.5-coupled sepharose). After immunoprecipi-
cell line contains equivalent levels of CD45 by Western
tation, the samples were split as above and either blotted for CD45
and CD4 after separation on an 8% nonreducing gel or zon a 12%
Blot of cell lysate (see Figure 3) and by cell surface
reducing gel.
expression (data not shown). Precipitation and blotting
specificity controls include CD45-negative cells and T
cell receptor–negative cells that express CD45. Neither CD45 (CD45RO) preferentially associate with the T cell
shows evidence for nonspecific bands or nonspecific receptor compared to higher molecular weight isoforms
association of CD45 during immunoprecipitation. Figure (CD45ABC). A more precise quantitation of the relative
2B demonstrates a similar experiment comparing the amounts of CD45RO versus CD45ABC associated with
abilityof anti-TCRand anti-CD4to coimmunoprecipitate the TCR following TCR immunoprecipitation was done
CD45. As in Figure 2A, CD45 is specifically coimmuno- by densitometric analysis by normalizing the amount of
precipitated with the T cell receptor but is not readily CD45 in the immunoprecipitate to the total amount of
detectableby Westernblot followinganti-CD4 precipita- CD45 in each cell line from a whole cell lysate detected
tion. In total, these data provide biochemical evidence in the same blot (Figure 3). Different dilutions of lysate
that there is a stable complex of CD45 and the TCR that and immunoprecipitate were used to ensure that the
is independent of the presence of CD4. In addition, this chemiluminescence signal in the Western blot had not
complex is present in the absence of prior T cell activa- plateaued, and a representative experiment is shown in
tion and is independent of CD4 or CD3 cross-linking that Figure 3A. In an average of three independent experi-
was necessary to induce capping in the fluorescence ments, there was approximately 3- to 4-fold more
colocalization experiments (Figure 1). CD45RO associated with the TCR compared to CD45ABC
(Figure 3B).
CD45 Isoform Regulation of Association
with the TCR Complex Organization of the CD45/TCR Complex
in Resting Primary CD4
1
T CellsSimilarly to the cocapping data (Figure 1; Leitenberg
et al., 1996), the immunoprecipitation experiments in The data presented above indicate the presence of a
preexisting complex of CD45 with the TCR in cell linesFigure 2 indicate that low molecular weight isoforms of
Immunity
704
Figure 4. CD45 Association with the TCR Complex in Primary CD4
1
T Cells
CD4
1
T cells were purified by negative selection from spleen and
lymph nodes of 8-week-old mice. (A) 10 310
6
cells per group were
lysed and immunoprecipitated with 5 mg of either CD45, TCR, or
CD4 antibodies and then assessed for the presence of CD45 or lck
upon Western blot following separation by 7% nonreducing SDS-
PAGE. The arrows indicate the presence of CD45B and CD45RO
isoforms. (B) 20 310
6
cells were immunoprecipitated with either
anti-CD45 or TCRb, and the immune complexes were serially diluted
1:2 and analyzed for the presence of CD45 on a 7% nonreducing
gel or TCRaand TCRzon a 12% reducing gel. The asterisk indicates
Figure 3. Quantification of CD45RO versus CD45ABC Coimmuno- the presence of an intact antibody band shadow that is sometimes
precipitated with the T Cell Receptor Complex visible using the avidin-horseradish peroxidase conjugate to de-
The T cell receptor was immunoprecipitated with anti-TCR as above velop the Western blot.
from 2 310
7
cells expressing CD45ABC or CD45RO. Whole cell
lysatefrom 10
6
cellequivalents was setasideprior to immunoprecip-
itation. (A) Different dilutions of immunoprecipitate or whole cell
cells in the Western blots shown in the following experi-
lysate were separated on a 5% nonreducing gel and blotted with
ments was determined in comparison with a ladder of
anti-CD45. (B) The average and standard deviation of normalized
CD45 isoforms obtained from the CD45-transfected cell
densitometric data from three independent immunoprecipitation ex-
lines described previously and by immunoprecipitation
periments is represented. The amount of CD45 immunoprecipitated
with the T cell receptor was normalized to the amount of CD45 in
with CD45B-specific antibodies (data not shown). As
the whole cell lysate from 2.5 310
5
cell equivalents for each cell line.
shown in Figure 4A, both CD45B and CD45RO isoforms
are readily detected following TCR precipitation, and,
as in Figure 2, immunoprecipitation with anti-CD4 failed
to coprecipitatesignificant amounts ofCD45. As showntransfected with individual CD45 isoforms and that this
correlates with enhanced T cellactivation (Novak et al., in the bottom panel of Figure 4A, the same blot was
also examined for the presence of lck as a control for1994; Leitenberg et al., 1996). In order to confirm these
findings in primary CD4
1
T cells and to investigate the CD4 immunoprecipitation. Of note is the significant
amount of lck found coimmunoprecipitated with CD45stoichiometry of CD45/TCR association in cells that ex-
press wild-type levels of CD45, CD3/TCR, and CD4, in addition to the lck associated with CD4. In addition, a
small amount of lck is also found coimmunoprecipitatedsimilar coimmunoprecipitation experiments were per-
formed using purified CD4
1
T cells from the spleen and with CD3/TCR.
In order to determine the relative percent of CD45lymph node of cytochrome C–specific T cell receptor
transgenic mice. In the mouse, naive CD4 T cells pre- associated withthe TCR andthe amountof TCR associ-
atedwith CD45,a semiquantitativeimmunoprecipitationdominantly express a mixture of two isoforms of CD45:
CD45B (variable exon 5 only expressed) and CD45RO experiment was performed (Figure 4B). Lysates from
primaryCD4
1
Tcells wereimmunopreciptated withanti-(variable exon 4, 5, and 6 not expressed) (Rogers et al.,
1992). The identity of these isoforms in primary CD4
1
bodies to the TCR or CD45. Serial 2-fold dilutions of
Regulation of CD45 Association with the TCR
705
the resulting immunoprecipitate were then analyzed by
Western blot to compare the total amount of TCRaor
TCRzwith the amount associated with CD45. The con-
verse experiment is also shown in which the total
amount of CD45 is compared to the amount coimmuno-
precipitatedwith theTCR complex.In both cases,signif-
icant association between CD45 and the TCR complex
are detected, and CD45 immunoprecipitation coimmu-
noprecipitates similar levels of both TCRaand the z
chain. Comparisons between the dilutions of the total
amount of CD45 and TCR to the amounts of coprecipi-
tated CD45 and the TCR present in a complex suggest
that approximately 10%–30% of the TCR and CD45 are
coassociated.
Differential Regulation of CD45/TCR Association
following T Cell Activation with Agonist
or Altered Peptide Ligands
The above data demonstrate the presence of a basal
complex of CD45 with the TCR in resting primary CD4
1
T cells. Our previous experiments correlating antigen
responsiveness with CD45/TCR association predict that
this association is required to initiate and maintain effi-
cient signal transduction in naive T cells and that disrup-
tion of CD45/TCR association would result in diminished
T cell activation. Previous work from our laboratory has
characterized the pattern of early signaling events in
naive T cells following stimulation with an agonist and
partial agonist peptide of moth cytochrome C. In this
system, stimulation with the agonist peptide results in
a sustained pattern of early signaling events (Ca
2
1
mobi-
lization, zphosphosphorylation), while stimulation with
a partial agonist peptide induces a diminished and tran-
sient pattern of early signaling events (Boutin et al.,
1997). We hypothesized that during stimulation with the
partial agonist peptide, CD45/TCR association may be
disrupted, resulting in a diminished or abbreviated sig-
naling cascade. This hypothesis was tested by immuno-
Figure 5. Differential Regulation of CD45/TCR Association during
precipitating the TCR complex following stimulation of
Agonist and Partial-Agonist Stimulation
naive MCC-specific CD4 T cells with agonist peptide
(A) CD4
1
T cells (20 310
6
) were purified from MCC-specific TCR
(pMCC) or partial agonist peptide-pulsed antigen-pre-
transgenic mice and stimulated for 5 min with APC pulsed with 20
senting cells and examining the immunoprecipitate for
mM of either pMCC (agonist), K99R (partial agonist),or pBSA (control
CD45. As shown in Figure 5A, TCR/CD45 association is
peptide). The cells were then assessed for CD45/TCR association
modestly enhanced following stimulation with agonist
following TCRbimmunoprecipitation and separation by nonreduc-
peptide(compared tostimulation witha controlI-E bind-
ing 7% SDS-PAGE as described in Figure 4. The middle panel is a
ing peptide, pBSA, which does not interact with the
blot for TCRa/bfrom the same gel to control for equal amounts of
MCC-specific TCR) but is substantially diminished after
immunoprecipitated TCR in each lane, and the bottom panel shows
equivalent amounts of immunoprecipitated TCR zchain are also
stimulation with the partial agonist, K99R. In all cases,
present from 20% of the sample separated on a 12% reducing gel.
equal amounts of TCR were immunoprecipitated, as
(B)The average change inTCR-associatedCD45RO following stimu-
shown by Western blot for TCR a/band TCR-associated
lation with the pMCC or K99R peptides compared to baseline levels
zchain. Average densitometric quantitation of these re-
seen with control peptide (pBSA). The amount of CD45 coimmuno-
sults from four independent experiments indicates a
precipitated with the TCR was assessed by densitometric scanning
consistent 40%–60% loss of CD45/TCR association fol-
and normalized to the amount of TCR a/bfrom the same gel for
each sample. The data shown are the average and standard devia-
lowing stimulation with the partial agonist peptide com-
tion from four independent experiments.
paredto unstimulatedcontrols, whileCD45/TCR associ-
(C) Purified CD4
1
T cells were stimulated with APC only (-) or APC
ation is maintained and enhanced following agonist
pulsed with either pMCC or K99R for the indicated periods of time
peptide stimulation (Figure 5B). In order to examine the
and then assessed for CD45/TCR association as in (A). Control lanes
kinetics of CD45/TCR dissociation, a similar experiment
marked APC contain APC only and are immunoprecipitated with
was performed in which the TCR complex was immuno-
anti-TCRb, and control lane C contains APC and T cells and is
precipitated at various time points following peptide
immunoprecipitated with a control antibody (anti-CD8). As in Figure
4, the asterisk indicates the presence of the antibody band.
stimulation. As shown in Figure 5C, CD45 dissociation
from the TCR occurs approximately 5 min after partial
agonist stimulation, while CD45/TCR association is sta-
bly maintained following agonist peptide stimulation for
Immunity
706
Figure 6. CD4 Cytoplasmic Tail Is Required
to Maintain CD45/TCR Stimulation following
Stimulation with Agonist Peptide
(A)Purified CD4
1
,CD8
2
Tcells from CD4wild-
type and CD4 dcyt mice were immunoprecip-
itated with anti-TCRb, anti-CD45, and anti-
CD4as described in Figure4.The presence of
associated CD45, lck, and TCR components
was detected by Western blot as described
in Figure 4.
(B)Purified CD4
1
,CD8
2
Tcells from CD4wild-
type and CD4 dcyt mice were stimulated with
APC pulsed with the control peptide (pBSA)
or agonist peptide (pMCC) for 5 min as de-
scribed in Figure 5. The cells were lysed and
assessed for the presence of coimmuno-
precipitated TCR and CD45 as described in
Figure 4.
(C) Average densitometric data of CD45RO
coimmunoprecipitated with the TCR follow-
ing agonist peptide stimulation in T cells from
CD4 wild-type or CD4 dcyt mice. The amount
of CD45RO is normalized to the amount of
TCR a/bfound in the same sample as de-
scribed in Figure 5. The results are the aver-
age of three independent experiments.
at least 15 min. These data suggest that variant peptide transgene. As expected, cells expressing the dcyt CD4
transgene did not have CD4-associated lck and alsosignaling can alterthe composition of the TCRcomplex,
promoting the dissociation of CD45, which in turn may lost TCR-associated lck indicating the requirement for
CD4-lck interaction in order to detect lck associationdownmodulateTCR signalingcausing atransient signal-
ing phenotype. Alternatively, the incomplete signaling with the TCR in resting T cells. Interestingly, this is in
contrast to the association of lck with CD45, which wascascade induced by the partial agonist peptide may
result in the destabilization of the CD45/TCR complex. only modestly affected in cells expressing the mutant
CD4 transgene. This is in agreement with previous data
in cell lines in which detection of CD45-associated lckCD4 Cytoplasmic Tail Is Required for Maintaining
CD45/TCR Association following Agonist was independent of the presence of CD4 (Ross et al.,
1994). As shown in Western blots of the whole cell ly-Peptide Stimulation
As indicated above, we have shown that TCR/CD45 sates, there are equal levels of CD45, TCR, and lck from
wild-type CD4 T cells or CD4 dcyt T cells. Of note isassociation does not require the expression of CD4.
However, CD4 signaling may be involved in maintaining the consistent finding shown in Figures 6A and 6B that
CD45/TCR association is modestly enhanced in T cellsthe stability of this interaction following T cell stimula-
tion. Since partial agonist signaling has been associated from the CD4 dcyt mice. This may indicate that some
CD45 is sequestered from the TCR complex in CD4
1
withfailure torecruitCD4 tothe TCRcomplex(Madrenas
et al., 1997), we hypothesized that CD4/TCR association cells.
When MCC-specific T cells from the CD4 dcyt micemay be required to maintain the CD45/TCR association
seen after agonist peptide signaling. In order to investi- were stimulated with agonist peptide (pMCC), CD45/
TCR association was diminished (Figures 6B and 6C).gate this possibility, MCC-specific TCR transgenic T
cells from wild-type mice or CD4 knockout mice recon- Figure 6C shows average densitometry data from three
independent experiments indicating that inthe absencestituted with a CD4 transgene encoding for the trans-
membrane and ectodomain of CD4 (CD4 dcyt) were of the cytoplasmic tail of CD4 agonist peptide destabi-
lizes the CD45/TCR complex. This is in contrast to thestimulatedwith agonistpeptide asdescribed inFigure 5.
Prior to this experiment, it was important to confirm results obtained with cells expressing wild-type CD4 in
which CD45/TCR association is augmented followingin resting, primary CD4 T cells that the association of
CD45 with the TCR was independent of CD4. When stimulation with agonist peptide and only is diminished
following stimulation with the partial agonist peptide,purified CD8
2
T cells are isolated from CD4-deficient
mice (data not shown) or CD4-deficient mice reconstitu- K99R. These data suggest that CD4-associated lck may
be necessary to maintain the association of CD45 withted with a mutant CD4 transgene that does not encode
for the cytoplasmic tail of CD4 (CD4dcyt), CD45associa- the TCR following peptide stimulation.
If lck was important in stabilizing the TCR/CD45 asso-tion with the TCR complex is not diminished (Figure 6A).
Also in agreement with Figures 2B and 4A, immunopre- ciation, wehypothesized thatTCR-associated lckwould
bedifferentially regulatedby agonist and variant peptidecipitation with CD4 antibodies fails to efficiently coim-
munoprecipitate CD45 in primary, resting CD4
1
T cells. signaling. To test this prediction, we examined the sta-
bility of the TCR/lck association following agonist orAs a control for these experiments, the ability to copre-
cipitatelck withCD4, CD45, andtheTCR wasalsoexam- altered peptide ligand stimulation (Figures 7A and 7B).
In these experiments, cells were stimulated with theined in cells expressing wild-type CD4 or the CD4dcyt
Regulation of CD45 Association with the TCR
707
lck from these cells (bottom panel of Figure 7A) shows
thatboth theagonist and K99R peptides induce a similar
level of serine/threonine phosphorylation as shown by
the peptide-specific induction of a slower mobility form
of lck (p60). Densitometric analysis from four indepen-
dent experiments is shown in Figure 7B, indicating that
CD45/lck association is diminished by approximately
50% following K99R stimulation. These data indicate
that in addition to CD45, the basal association of lck
with the TCR complex is differentially regulated by pep-
tides of different avidities for the TCR. The dissociation
of lck and CD45 from the TCR in these experiments also
correlates with different patterns of ztyrosinephosphor-
ylation (Figure 7A, second panel). Consistent with our
previously published data pMCC induces phosphoryla-
tion of a saturated form of phosphoz(p23), in contrast
to the altered peptide K99R that primarily induces p21 z
phosphorylation(Boutin etal., 1997).These experiments
suggest that in addition to the different patterns of tyro-
sine phosphorylation induced by agonist and altered
peptide ligands there is a change in the macromolecular
composition of the TCR signaling complex.
Discussion
Inthe presentreport, weprovideevidence thatthe trans-
membrane tyrosine phosphatase CD45 is basally asso-
ciated with the CD3/TCR complex and that this associa-
tion is correllated with enhanced T cell activation. One
possible model for how CD45 association with the TCR
enhances TCR signaling pathways would be by increas-
ing lck activity upon recruitment to the TCR complex
following recognition of antigen. This in turn would pro-
mote full phosphorylation of the ITAM motifs of the
CD3/zcomponents and facilitate the recruitment and
activation of the ZAP70 tyrosine kinase. In addition,
CD45 may maintain lck in an “open” configuration pro-
Figure 7. Differential Regulation of TCR-Associated lck by Agonist
moting lck interaction and recruitment of a variety of
and Altered Peptide Ligand Stimulation
adapter proteins and other signaling molecules into a
(A) Purified CD4
1
,CD8
2
T cells from MCC-specific TCR transgenic
large macromolecular complex that further facilitates T
mice were stimulated with APC pulsed with 20 mM of the control
cell activation and IL-2 production independently of lck
peptide (pBSA), agonist peptide (pMCC), or altered peptide ligand
kinase activity (Collins and Burakoff, 1993; Sieh et al.,
(K99R) for 5 min as described in Figure 5. The cells were lysed and
1993;Xu andLittman, 1993). Thus, the presence of CD45
assessed for the presence of coimmunoprecipitated TCR and lck
as described in Figures 4 and 5. The bottom panel is a Western blot
in a preformed complex with the TCR would precommit
of total lck from whole cell lysates from 5 310
5
cells separated by
the T cell to respond optimally when exposed to src
a nonreducing 7% SDS-PAGE. Phosphorylated zchain was immu-
family kinases, while the absence of CD45 from the TCR
noprecipitated with anti-TCRbfrom lysates from the same experi-
complex would precommit that cell to respond subopti-
ment and detected with anti-phosphotyrosine monoclonal antibody
mally or alternatively through src family kinase-indepen-
after separation by 12% SDS-PAGE (second panel). The same blot
was stripped and reprobed for total zprotein (third panel).
dent signaling pathways.
(B) Average densitometric data of lck coimmunoprecipitated with
We currently know very little regarding the biochemi-
the TCR following peptide stimulation in T cells from four indepen-
cal basis for the basal association of CD45 with the TCR.
dent experiments. The data are normalized to the amount of TCR
It is clear from coimmunoprecipitation experiments and
a/bfor each sample as described in Figure 5.
fluorescence colocalization data that the ectodomain of
CD45 can regulate the efficiency of association with the
TCR in that high molecular weight CD45 isoforms do not
indicated peptides and the TCR immunoprecipitated associate well with the TCR compared to low molecular
and the presence of associated lck was detected by weight CD45 isoforms. Since the high molecular weight
Western blot. Indeed, similarly to CD45/TCR associa- CD45isoforms containthe samebasepeptide sequence
tion, we found that stimulation with the partial agonist as thelow molecularweight isoforms,it seemslikely that
peptide, K99R, disrupted the basal association of lck the failure of the high molecular weight CD45 isoforms
with the TCR. This was in contrast to stimulation with to associate with the TCR is due to steric and static
the agonist peptide in which TCR/lck association is
maintained. Interestingly, Western blot analysis of total interference from the additional protein encoded in the
Immunity
708
variable exons anddue tothe extensive additionalglyco- apparent contradiction to the topological model of T cell
activation proposed by Shaw and Dustin (1997), whosylation. Electron microscopicimaging ofpurified solu-
ble CD45 ectodomains reveals that the CD45ABC iso- theorized that molecules like CD45 that extend greater
than 15–20 nm from the cell surface would be excludedform exhibits an extended rodlike structure and is
predicted to extend 61 nm above the cell surface com- from the TCR/APC contact zone. This model assumes
thatCD45 extendsperpendicularly fromthe cellsurface.pared to the CD45RO isoforms, which are predicted to
extend approximately 28 nm (McCall et al., 1992). This It is possible that CD45 (especially smaller isoforms of
CD45) are sufficiently bent laterally to allow for inclusionextra length of the CD45ABC isoform may simply pre-
vent a default association that occurs more readily with in the APC/TCR contact region. In agreement with our
observations of sustained CD45/TCR association fol-the low molecular weight CD45RO isoform. The large
size and heavily glycosylated nature of CD45 has been lowing agonist peptide stimulation are fluorescent im-
aging studies from Sperling et al. (1998) and Kupferpredicted on theoretical grounds to be an impediment
to T cell activation by sterically interfering with APC and colleagues (A. Kupfer, personal communication),
demonstrating the presence of CD45 in the TCR/APCinteraction (Shaw and Dustin, 1997). Our data suggest
thatin addition to the difficulties postulated tooccur due contactzone cap.Thus, itappears that despite the theo-
retical constraints of the large size of CD45, it is ableto expression of high molecular weight CD45 isoforms
during TCR-APC contact, there is also a difference in to cluster with the TCR during APC contact following
stimulation with a strong agonist peptide.lateralassociation ofCD45/TCR secondary tothesize of
the CD45 isoform.Thus, cellsthat expresslow molecular Although it is clear from our previously published data
that there is a different pattern of tyrosinephosphoryla-weight CD45 isoforms have the dual advantage of less
interference during TCR/APC contact and aTCR signal- tion following agonist or APL stimulation (Boutin et al.,
1997), we do not have sufficient data to conclude thating complex poised to respond with higher efficiency.
It should be noted that although it is clear that the this is directly due to failure of CD45 to stably associate
with the TCR. In fact, we have reason to believe that aectodomain of CD45 can regulate association with the
TCR, it remains uncertain if the cytoplasmic or trans- transient signaling pattern does not always correllate
with lack of stable CD45/TCR association. Using T cellsmembrane domains of CD45 are also involved in pro-
moting and stabilizing this interaction with the T cell isolated from CD4 mutant mice, we have previously
found that stimulation with a strong agonist peptidereceptor complex. This seems quite likely in view of
CD45 interaction with lck that may act as a bridge with induces a sustainedsignaling pattern (Leitenberg et al.,
1998). However, in the data shown in Figure 6, CD45/other components of the TCR signaling complex. Simi-
larlyto CD45/TCRassociation, CD45/lckassociationoc- TCR association is destabilized in this situation. This
suggests that in the presence of a sufficiently strongcurs independently of the expression of CD4, and the
precise mechanism for this association remains uncer- TCR signal, a sustained signaling pattern can be main-
tained in the absence of CD45/TCR association. This istain. One possibility is that it is mediated by an adapter
protein known as CD45-associated protein (CD45-AP), similar tootherdata fromour labusing CD45transfected
cell lines in which we were able to stimulate cells thatwhich requires the transmembrane domain of CD45 for
detection in coimmunoprecipitation experiments (McFar- expressed high or low molecular weight CD45 isoforms
equally well following stimulation with immobilized anti-land and Thomas, 1995). In the absence of CD45-AP,
CD45-lck association is partially diminished but remains CD3 and only saw CD45-specific affects following stim-
ulation with a weaker signal such as peptide. We sug-detectable, suggesting that both the transmembrane
and the cytoplasmic domain of CD45 may be involved in gest that the presence of CD45 with the TCR complex
can act to facilitate T cell activation following modestmediating association with lck (McFarlandand Thomas,
1995; Matsuda et al., 1998). This may be an important or weak signals to the TCR but that CD45 association
with the TCR is not required during strong signaling.mechanism forstabilizing andregulating CD45/TCR as-
sociation as discussed below. The mechanism for how CD45 is dissociated from this
complex remains unclear but may be a byproduct ofRegardless of the mechanism of CD45/TCR associa-
tion, it seems likely, however, that control of this associ- the incomplete activation program induced by partial
agonist peptides and failure to form a stable complexation will be an important regulatory point before and
during T cell activation. In the present manuscript, we with CD4-associated lck. For example, incomplete
phosphorylation of the CD3/zITAM motifs may preventprovide evidencethat CD45/TCRassociationis differen-
tially regulated by agonist and partial agonist signaling CD4-lck from stably associating with the TCR via SH2
domain-dependent interactions that may also stabilizeof resting,primary CD4
1
T cells. Using a well character-
ized model system for naive T cell activation by agonist CD45-TCR association since CD45 also can associate
with lck. This additional stabilization of CD45 with theand partial agonist peptides(which inducesustained or
transient activation patterns respectively), we show that TCR complex may be necessary since TCR ligation has
recently been shown to induce partitioning into lipidstimulation with the partial agonist peptide promotes
dissociation of CD45 from the TCR complex within 5 enriched membrane microdomains following activation
(“rafts”) (Montixi et al., 1998; Xavier et al., 1998; Zhangminafter activation.This roughlycorrelates withthetime
course of dephosphorylation of the saturated isoform et al., 1998). CD45 is thought to be largely naturally
excluded from these domains (Rodgers and Rose, 1996;of phosphozand with the duration of calcium transients
generated by the partial agonist (Boutin et al., 1997). In Xavier et al., 1998). In addition to components of the
TCR complex partioning into distinct membrane micro-contrast, following stimulation with the agonist peptide,
CD45/TCR association remains relatively stable for at domains, TCR signaling may also differentially affect
cytoskeletal associations of the TCR, CD4, and CD45least 15 min following stimulation. These data are in
Regulation of CD45 Association with the TCR
709
by labeling with either biotinylated anti-CD4 (GK1.5) or clonotypic
that could also disrupt basal associations present in
anti-TCR(3D3). The cellswerethen washed and labeledwithfluores-
restingT cells.Thus, inorder to promotesustained asso-
cein conjugated pan-specific anti-CD45 (PharMingen). Control cells
ciation with the TCR, additional activation-dependent
(labeledwith PE or FITCalone)werealways prepared simultaneously
interactions may be required to stablize CD45 associa-
for each cell line to set compensation parameters. Fluorescence
tion with the TCR/CD4/lck complex.
localization was determined using a scanning video laser cytometer
(ACAS 570, Meridien Instruments) equipped with a 200 mW argon
Our data examining CD45/TCR association following
laser. For each experimental group, 100 capped cells were counted,
activation in T cells expressing mutant CD4 that cannot
and the percent of capped cells with associated CD45 was deter-
associate with lck suggest that the presence of lck in the
mined.
TCR complex is critical to stabilize CD45 association. In
these experiments, CD45/TCR association was dimin-
Peptides
ished following stimulation with the agonist peptide sim-
Moth cytochrome c (81–103): pMCC, VFAGLKKANERADLIAYLKQ
ilarly to that seen following stimulation with the partial
ATK; K99R, VFAGLKKANERADLIAYLRQATK; and pBSA (141–154),
GKYLYEIARRHPYF peptides were synthesized by the W. M. Keck
agonist peptide. This is in contrast to the increase in
Foundation Biotechnology Resource Laboratory. All peptides were
CD45/TCR association seen following agonist peptide
high-pressure liquid chromatography purified prior to use.
stimulation in cells expressing wild-type CD4. These
data indicate that the cytoplasmic tail of CD4 and poten-
Preparation of APC and CD4
1
T Cells
tially CD4-associated lck are required to stabilize the
T cell depleted APC were prepared by antibody-mediated comple-
interaction of CD45 with the TCR complex following
ment lysis of 5R splenocytes as previously described (Leitenberg
activation. Consistent with this idea is our observation
et al., 1998). CD4
1
,CD8
2
T cells from lymph nodes and spleens
of transgenic mice were isolated using immunomagnetic negative
that the basal TCR/lck association, in addition to CD45,
selection as previously described (Leitenberg et al., 1998) using
is also diminished following stimulation with an altered
antibodies against CD8, CD32/CD16, B220, and MHC class II fol-
peptide ligand. In summary, our data demonstrate a
lowed by incubation with anti-mouse and -rat Ig-coated magnetic
basal association of CD45 with the TCR complex prior
beads (Perspective Diagnostics). Purity of the recovered Va11
1
,
to T cell activation and indicate that regulation of this
CD4
1
T cells (or Va11
1
, CD4
2
CD8
2
T cells in CD4
2
/
2
mice) was
association before and during T cell activation may be
usually 85%–95% as determined by staining with anti-CD4 and anti-
Va11 mAb.
a mechanism to differentially affect T cell signaling
pathways.
T Cell Activation
T-depleted splenocytes from B10.A (5R) mice were pulsed with 20
Experimental Procedures mMof the indicatedpeptidefor 2–4 hrat378C in Hank’sbalancedsalt
solutionsupplemented with 5%FCS. The pulsed antigen-presenting
Antibodies cells were washed once and mixed 1:1 with purifed MCC-specific
The following monoclonal antibodies were used in this study: M1/ T cells in microcentrifuge tubes, quickly pelleted, and incubated at
9.3.4. HL.2, pan-specific anti-CD45 (TIB122, ATCC), anti-CD4 378C for the indicated times and then lysed in ice-cold lysis buffer.
(GK1.5), anti-TCRb(H57), and an anti-clonotypic antibody for the
D10 TCR (3D3) (Kaye et al., 1983). All antibodies were purified from Immunoprecipitation and Western Blotting
culture supernatants on protein G columns and dialyzed against Coimmunoprecipitation of CD45 with CD3/TCR was done using a
PBS before use. For some experiments, purified anti-TCRb(H57), 1% Brij 96/97 (Sigma) lysis buffer (20 mM Tris-Cl [pH 7.5], 150 mM
anti-TCRa(H28), anti-CD45 (30-F11), and anti-CD4 (GK1.5) were NaCl, 1 mM MgCl
2
, and 1 mM EGTA) supplemented with protease
purchased from PharMingen. and phosphatase inhibitors (10 mg/ml leupeptin, 10 mg/ml aprotinin,
1 mM PMSF,1 mM Na
3
VO
4
, and 50 mM NaF). Cells were lysed for
Cell Lines 30 min on ice and the detergent soluble material separated by cen-
A CD45-negative mutant of the BW5147 AKR thymoma was trans- trifugationfor 15 minatapproximately 14,000 3g.Immunoprecipita-
fected with individual CD45 isoform cDNAs encoding CD45RO and tion was done using 5 mg of the indicated monoclonal antibody
CD45ABC as described previously (Novak et al., 1994). These cells followed by Protein Gsepharose(PharmaciaBiotech, Uppsala, Swe-
have also been transfected with CD4 and the T cell receptor from den) for an additional 1 hr. In some experiments, directly conjugated
the D10.G4.1 Th2 cell clone. T cell receptor–negative revertants of GK1.5-sepharose was used to immunoprecipitate CD4.
CD45ABC and CD45RO clones were generated by repetitive cell Standard Western blot analysis was done following SDS poly-
sorting using a FACStar flow cytometer. All cell lines were routinely acrylamide electrophoresis and transfer onto nitrocellulose paper
monitored by flow cytometry to ensure stable expression of CD45, (Schleicher and Schuell, Keene, NH). CD45 was detected using a
CD4, and CD3. When necessary, the cells are sorted so that the biotinylated anti-CD45 antibody (M1/9.3.4. HL.2 or 30-F11) that is
different clones maintain similar expression levels of the transfected pan-specific for all isoforms followed by avidin-coupled horseradish
genes. peroxidase. The zchain of the T cell receptor and lck were detected
using rabbit polyclonal antisera prepared in our laboratory (Boutin
Mice et al., 1997) followed by protein A coupled horseradish peroxidase
B10.A (5R) (5R) mice were obtained from The Jackson Laboratory. (Sigma). TCRawas detected with the H28 monoclonal antibody
The AND TCR transgenic mice in which CD4
1
T cells express a TCR (PharMingen). CD4 was detected using biotinylated anti-CD4
specific for the carboxyl terminus of pigeon cytochrome c have (GK1.5). Determination of phosphorylated zinduction was done fol-
been previously described (Kaye et al., 1989) and are bred in our lowing H57 immunoprecipitation as described above except 1%
facilities and maintained as heterozygotes on B10.BR background. NP-40 is used in the lysis buffer and the 4G10 anti-phosphotyrosine
The CD4
2
/
2
and CD4
2
/
2
dcyt mice were generously provided by D. monoclonal antibody (UBI) was used in the Western blot. All of
Littman (New York University) and were backcrossed 5–6 times onto the immunoblots were developed with the ECL chemiluminescent
a B10.BR background and crossed with the AND T cell receptor detection system.
transgenic mice (Leitenberg et al., 1998). All mice used in these
studies were 6 to 10 weeks old. Acknowledgments
Fluorescence Colocalization
Colocalization of CD45 with CD4 and CD3/TCR was assayed by We thank Dan Littman for generously providing the CD4-deficient
and CD4 dcyt. mice, Jonathan Kaye for originally providing thecocapping as described previously (Leitenberg et al., 1996). In brief,
cells transfected with individual CD45 isoforms were induced to cap MCC-specific AND transgenic mice, and Stephanie Constant for
Immunity
710
critically reviewing the manuscript. D. L. is supported in part by an Luqman, M., Johnson,P., Trowbridge, I.S.,and Bottomly, K. (1991).
Differential expression of the alternatively spliced exons of murine
Arthritis Investigator Award. CD45 in Th1 and Th2 cloned lines. Eur. J. Immunol. 21, 17–22.
Received November 30, 1998; revised May 3, 1999. Madrenas, J., Chau, L.A., Smith, J., Bluestone, J.A., and Germain,
R.N. (1997). The efficiency of CD4 recruitment to ligand-engaged
References TCR controls the agonist/partial agonist properties of peptide-MHC
molecule ligands. J. Exp. Med. 185, 219–229.
Akbar, A.M., Terry, L., Timms, A., Beverley, P.C.L., and Janossy, G. Matsuda, A., Motoya, S., Kimura, S., McInnis, R., Maizel, A.L., and
(1988). Loss of CD45R and gain of UCHL1 reactivity is a feature of Takeda, A. (1998). Disruption of lymphocyte function and signaling
primed T cells. J. Immunol. 140, 2171–2178. in CD45-associated protein-null mice. J. Exp. Med. 187, 1863–1870.
Bottomly, K., Luqman, M., Greenbaum, L., Carding, S., West, J., McCall, M.N., Shotton, D.M., and Barclay, A.N. (1992). Expression
Pasqualini, T., and Murphy, D.B. (1989). A monoclonal antibody to of soluble isoforms of rat CD45. Analysis by electron microscopy
murine CD45R distinguishes CD4T cell populations that produce and use in epitope mapping of anti-CD45R monoclonal antibodies.
different lymphokines. Eur. J. Immunol. 19, 617–623. Immunology 76, 310–317.
Boutin, Y., Leitenberg, D., Tao, X., and Bottomly, K. (1997). Distinct McFarland, E.D., and Thomas, M.L. (1995). CD45 protein-tyrosine
biochemicalsignals characterize agonistandaltered peptide ligand- phosphatase associates with the WW domain-containing protein,
induced differentiation of naive CD4 T cells into Th1 and Th2 sub- CD45AP, through the transmembrane region. J. Biol. Chem. 270,
sets. J. Immunol. 159, 5802–5809. 28103–28107.
Burns, C.M., Sakaguchi, K., Appella, E., and Ashwell, J.D. (1994). McFarland, E.D.C., Hurley, T.M., Pingel, J.T., Sefton, B.M., Shaw,
CD45 regulation of tyrosine phosphorylation and enzyme activity of A., and Thomas, M.L. (1993). Correlation between src family member
src family kinases. J. Biol. Chem. 269, 13594–13600. regulation by the protein-tyrosine-phosphatase CD45 and trans-
membrane signaling through the T-cell receptor. Proc. Natl. Acad.
Collins, T., and Burakoff, S. (1993). Tyrosine kinase activity of CD4- Sci. USA 90, 1402–1406.
associated p56lck may not be required for CD4-dependent T-cell
activation. Proc. Natl. Acad. Sci. USA 90, 11885–11889. McKenney, D.W., Onodera, H., Gorman, L., Mimura, T., and
Rothstein, D.M. (1995). Distinct isoforms of CD45 protein tyrosine
D’Oro, U., Sakaguchi, K., Appella, E., and Ashwell, J.D. (1996). Muta- phosphatase differentially regulate interleukin 2 secretion and acti-
tional analysis of lck in CD45-negative T cells: dominant role of vation signal pathways involving vav in T cells. J. Biol. Chem. 270,
tyrosine 394 phosphorylation in kinase activity. Mol. Cell. Biol. 16,24949–24954.
4996–5003. Montixi, C., Langlet, C., Bernard, A.-M., Thimonier, J., Dubois, C.,
Duplay, P., Alcover, A., Fargeas, C., Sekaly, R.P., and Branton, P.E. Wurbel, M.-A., Chauven, J.-P., Pierres, M., and He, H.-T. (1998).
(1996). An activated epidermal growth factor receptor/lck chimera Engagement of T cell receptor triggers its recruitment to low-density
restores early T cell receptor-mediated calcium response in a CD45- detergent-insoluble membrane domains. EMBO J. 17, 5334–5348.
deficient T cell line. J. Biol. Chem. 271, 17896–17902. Mustelin, T., Coggeshall, K.M., and Altman, A. (1989). Rapid activa-
Furukawa, T., Itoh, M., Krueger, N.X., Streuli, M., and Saito, H. (1994). tion of the T-cell tyrosine protein kinase pp56
lck
by the CD45 phos-
Specific interaction of the CD45 protein tyrosine phosphatase with photyrosine phosphatase. Proc. Natl. Acad. Sci. USA 86,6302–6306.
tyrosine-phosphorylated CD3 zchain. Proc. Natl. Acad. Sci. USA Mustelin, T., Pessa-Morikawa, T., Autero, M., Grassmann, M., An-
91, 10928–10929. dersson, L.C., Gahmber, C.G., and Burn, P. (1992). Regulation of
Guttinger,M., Gassmann, M.,Amrein,K.J., and Burn, P.(1992). CD45 the p59
fyn
protein tyrosine kinase by the CD45 phosphotyrosine
phosphotyrosine phosphatase and p56
lck
protein tyrosine kinase: a phosphatase. Eur. J. Immunol. 22, 1173–1178.
functional complex crucial in T cell signal transduction. Int.Immunol. Mustelin, T., Williams, S., Tailor, P., Couture, C., Zenner, G., Burn,
4, 1325–1330. P., Ashwell, J.D., and Altman, A. (1995). Regulation of the p70
ZAP
Hathcock, K.S., Laszlo, G., Dickler, H.B., Sharrow, S.O., Johnson, tyrosine protein kinase in T cells by the CD45 phosphotyrosine
P., Trowbridge, I.S., and Hodes, R.J. (1992). Expression of variable phosphatase. Eur. J. Immunol. 25, 942–946.
exon A-,B-, and C-specific CD45 determinants on peripheral and Novak, T., Farber, D., Cheol Hong, S., Johnson, P., and Bottomly,
thymic T cell populations. J. Immunol. 148, 19–28. K. (1994). Isoforms of the transmembrane tyrosine phosphatase
Kaye, J., Porcelli, S., Tite, J., Jones, B., and Janeway, C.A. (1983). CD45 differentially affect T cell recognition. Immunity 1, 109–119.
Both a monoclonal antibody and antisera specific for determinants Ostergaard, H.L., Shackelford, D.A., Hurley, T.R., Johnson, P., Hy-
unique to individual cloned helper T cell lines can substitute for man, R., Sefton, B.M., and Trowbridge, I.S. (1989). Expression of
antigen and antigen presenting cells in the activation of T cells. J. CD45 alters phosphorylation of the lck-encoded tyrosine kinase
Exp. Med. 158, 836–856. in murine lymphoma T-cell lines. Proc. Natl. Acad. Sci. USA 86,
Kaye, J., Hsa, M.-L., Sauron, M.-E., Jameson, S.C., Gasciogne, N., 8959–8963.
and Hendrik, S.M. (1989). Selective development of CD4
1
T cells in Rodgers, W., and Rose, J.K. (1996). Exclusion of CD45 inhibits activ-
transgenic mice express a class II MHC restricted antigen receptor. ity of p56lck associated with glycolipid-enriched membrane do-
Nature 341, 746–749. mains. J. Cell. Biol. 135, 1515–1523.
Koretzky, G.A., Kohmetscher, M., and Ross, S. (1993). CD45-associ- Rogers, P.R., Pilapil, S., Hayakawa, K., Romain, P.L., and Parker,
ated kinase activity requires lck but not T cell receptor expression D.C. (1992). CD45 Alternative exon expression in murine and human
in the Jurkat T cell line. J. Biol. Chem. 268, 8958–8964. CD41T cell subsets. J. Immunol. 148, 4054–4065.
Lee, W.T., Yin, X.M., and Vitetta, E.S. (1990). Functional and ontoge- Ross, S.E., Schraven, B., Goldman, F.D., Crabtree, J., and Koretzky,
netic analysis of murine CD45Rhi and CD45Rlo CD41T cells. J. G.A. (1994). The association between CD45 and lck does not require
Immunol. 144, 3288–3295. CD4 or CD8 and is independent of T cell receptor stimulation. Bio-
chem. Biophys. Res. Commun. 198, 88–96.Lefrancois, L., and Goodman, T. (1987). Developmental sequence
of T200 antigen modifications in murine T cells. J. Immunol. 139,Schraven, B., Kirchgessner, H., Gaber, B., Samstag, Y., and Meuer,
3718–3724. S. (1991). A functional complex is formed between the protein tyro-
sinephosphatase CD45, theproteintyrosine kinase p56
lck
,and pp32,
Leitenberg, D., Novak, T., Farber, D., Smith, B., and Bottomly, K. a possible common substrate. Eur. J. Immunol. 21, 2469–2477.
(1996). The extracellular domain of CD45 controls association with
the CD4 T cell receptor complex and the response to antigen-spe- Shaw, A.S., and Dustin, M.L. (1997). Making the T cell receptor go
cific stimulation. J. Exp. Med. 183, 249–259. the distance: a topological view of T cell activation. Immunity 6,
361–369.
Leitenberg, D., Boutin, Y., Constant, S., and Bottomly, K. (1998).
CD4 regulation of T cell receptor signaling and T cell differentiation Sieh, M., Bolen, J.B., and Weiss, A. (1993). CD45 specifically modu-
following stimulation with peptides of different affinites for the T cell lates binding of Lck to a phosphopeptide encompassing the nega-
tive regulatory tyrosine of lck. EMBO J. 12, 315–321.receptor. J. Immunol. 161, 1194–1203.
Regulation of CD45 Association with the TCR
711
Sperling, A., Sedy, J., Manjunath, N., Kupfer, A., Ardman, B., and
Burkhardt, J. (1998). TCR signaling induces selective exclusion of
CD43 from the T cell-antigen-presenting cell contact site. J. Immu-
nol. 161, 6459–6462.
Tao, X., Grant, C., Constant, S., and Bottomly, K. (1997). Induction
of IL-4-producing CD41T cells by antigenic peptides altered for
TCR binding. J. Immunol. 158, 4237–4244.
Trowbridge, I.S., and Thomas, M.L. (1994). CD45: an emerging role
as a protein tyrosine phosphatase required for lymphocyte activa-
tion and development. Annu. Rev. Immunol. 12, 85–116.
Xavier, R., Brennan, T., Li, Q., McCormack, C., and Seed, B. (1998).
Membrane compartmentation is required for efficient T cell activa-
tion. Immunity 8, 723–732.
Xu, H., and Littman, D.R. (1993). A kinase-independent function of
lckin potentiating antigen-specific Tcellactivation.Cell 74, 633–644.
Zhang, W., Trible, R.P., and Samelson, L.E. (1998). LAT palmitoyla-
tion: its essential role in membrane microdomain targeting and tyro-
sine phosphorylation during T cell activation. Immunity 9, 239–246.
