Article

Mechanism of B-cell receptor-induced phosphorylation and activation of phospholipase C-γ2

Laboratory of Cell Signaling, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA.
Molecular and Cellular Biology (Impact Factor: 5.04). 12/2004; 24(22):9986-99. DOI: 10.1128/MCB.24.22.9986-9999.2004
Source: PubMed

ABSTRACT Phospholipase C-gamma2 (PLC-gamma2) plays an important role in B-cell signaling. Phosphorylation of various tyrosine residues of PLC-gamma2 has been implicated in regulation of its lipase activity. With the use of antibodies specific for each of the putative phosphorylation sites, we have now shown that PLC-gamma2 is phosphorylated on Y753, Y759, and Y1217 in response to engagement of the B-cell receptor in Ramos cells, as well as in murine splenic B cells. In cells stimulated maximally via this receptor, the extent of phosphorylation of Y1217 was three times that of Y753 or of Y759. Stimulation of Jurkat T cells or platelets via their immunoreceptors also elicited phosphorylation of Y753 and Y759 but not that of Y1217. A basal level of phosphorylation of Y753 was apparent in unstimulated lymphocytes. The extent of phosphorylation of Y753 and Y759, but not that of Y1217, correlated with the lipase activity of PLC-gamma2. Examination of the effects of various pharmacological inhibitors and of RNA interference in Ramos cells suggested that Btk is largely, but not completely, responsible for phosphorylation of Y753 and Y759, whereas phosphorylation of Y1217 is independent of Btk. Finally, phosphorylation of Y1217 and that of Y753 and Y759 occurred on different PLC-gamma2 molecules.

Download full-text

Full-text

Available from: Yeun Ju Kim, Jul 09, 2014
0 Followers
 · 
89 Views
  • Source
    • "The close juxtaposition of PDK1 with Akt stimulates threonine 308 phosphorylation and activation of Akt kinase function that is then stabilized by phosphorylation of serine 473 by mTorc2 [30]. The close juxtaposition of Syk, Btk, and PLCγ2 at the B cell plasma membrane allows Syk and Btk to phosphorylate PLCγ2 and induce its enzymatic activation (Figure 1(c)) [31]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Chronic lymphocytic leukaemia (CLL) is an incurable malignancy of mature B cells. CLL is important clinically in Western countries because of its commonality and because of the significant morbidity and mortality associated with the progressive form of this incurable disease. The B cell receptor (BCR) expressed on the malignant cells in CLL contributes to disease pathogenesis by providing signals for survival and proliferation, and the signal transduction pathway initiated by engagement of this receptor is now the target of several therapeutic strategies. The purpose of this review is to outline current understanding of the BCR signal cascade in normal B cells and then question whether this understanding applies to CLL cells. In particular, this review studies the phenomenon of anergy in CLL cells, and whether certain adaptations allow the cells to overcome anergy and allow full BCR signaling to take place. Finally, this review analyzes how BCR signals can be therapeutically targeted for the treatment of CLL.
    07/2014; 2014:208928. DOI:10.1155/2014/208928
  • Source
    • "Targeted deletion of Plcγ2 but not Plcγ1 in mice results in an in vivo osteopetrotic phenotype [68], suggesting that PLCγ2 is the critical isoform for sRANKL-induced osteoclastogenesis. PLCγ2 has four tyrosine phosphorylation sites (Tyr753, Tyr759, Tyr1197, Tyr1217) [73-75]. In separate experiments the mutation of all four of these tyrosines had a dramatic effect on PLCγ2 activation as measured by intracellular calcium mobilization in B cells [73]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Cherubism is a rare bone dysplasia that is characterized by symmetrical bone resorption limited to the jaws. Bone lesions are filled with soft fibrous giant cell-rich tissue that can expand and cause severe facial deformity. The disorder typically begins in children at ages of 2-5 years and the bone resorption and facial swelling continues until puberty; in most cases the lesions regress spontaneously thereafter. Most patients with cherubism have germline mutations in the gene encoding SH3BP2, an adapter protein involved in adaptive and innate immune response signaling. A mouse model carrying a Pro416Arg mutation in SH3BP2 develops osteopenia and expansile lytic lesions in bone and some soft tissue organs. In this review we discuss the genetics of cherubism, the biological functions of SH3BP2 and the analysis of the mouse model. The data suggest that the underlying cause for cherubism is a systemic autoinflammatory response to physiologic challenges despite the localized appearance of bone resorption and fibrous expansion to the jaws in humans.
    Orphanet Journal of Rare Diseases 05/2012; 7 Suppl 1(Suppl 1):S5. DOI:10.1186/1750-1172-7-S1-S5 · 3.96 Impact Factor
  • Source
    • "The involvement of multiple SFKs in a signal transduction pathway is not without precedent — lymphocyte (T-and B-cell) activation serves as an example (Huang and Wang, 2004; Quintana et al., 2005; Randriamampita and Trautmann, 2004; Saijo et al., 2003; Gauld and Cambier, 2004; Kim et al., 2004; Kurosaki, 1999). An outstanding question concerns which, if any, SFK(s) interacts with PLCγ. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Egg activation at fertilization in deuterostomes requires a rise in intracellular Ca(2+), which is released from the egg's endoplasmic reticulum. In sea urchins, a Src Family Kinase (SpSFK1) is necessary for the PLCgamma-mediated signaling event that initiates this Ca(2+) release (Giusti, A.F., O'Neill, F.J., Yamasu, K., Foltz, K.R. and Jaffe, L.A., 2003. Function of a sea urchin egg Src family kinase in initiating Ca2+ release at fertilization. Dev. Biol. 256, 367-378.). Annotation of the Strongylocentrotus purpuratus genome sequence led to the identification of additional, predicted SFKs (Bradham, C.A., Foltz, D.R., Beane, W.S., Amone, M.I., Rizzo, F., Coffman, J.A., Mushegian, A., Goel, M., Morales, J., Geneviere, A.M., Lapraz, F., Robertson, A.J., Kelkar, H., Loza-Coll, M., Townley, I.K., Raisch, M., Roux, M.M., Lepage, T., Gache, C., McClay, D.R., Manning, G., 2006. The sea urchin kinome: a first look. Dev. Biol. 300, 180-193.; Roux, M.M., Townley, I.K., Raisch, M., Reade, A., Bradham, C., Humphreys, G., Gunaratne, H.J., Killian, C.E., Moy, G., Su, Y.H., Ettensohn, C.A., Wilt, F., Vacquier, V.D., Burke, R.D., Wessel, G. and Foltz, K.R., 2006. A functional genomic and proteomic perspective of sea urchin calcium signaling and egg activation. Dev. Biol. 300, 416-433.). Here, we describe the cloning and characterization of these 4 additional SFKs and test their function during the initial Ca(2+) release at fertilization using the dominant-interfering microinjection method coupled with Ca(2+) recording. While two of the new SFKs (SpFrk and SpSFK3) are necessary for Ca(2+) release, SpSFK5 appears dispensable for early egg to embryo transition events. Interestingly, SpSFK7 may be involved in preventing precocious release of Ca(2+). Binding studies indicate that only SpSFK1 is capable of direct interaction with PLCgamma. Immunolocalization studies suggest that one or more SpSFK and PLCgamma are localized to the egg cortex and at the site of sperm-egg interaction. Collectively, these data indicate that more than one SFK is involved in the Ca(2+) release pathway at fertilization.
    Developmental Biology 02/2009; 327(2):465-77. DOI:10.1016/j.ydbio.2008.12.032 · 3.64 Impact Factor
Show more