EphB6-null mutation results in compromised T cell function

Laboratory of Immunology, Centre de Recherché, Notre Dame Hospital, Centre Hospitalier de l'Université de Montréal, Pavilion DeSève, 1560 Sherbrooke Street East, Montréal, Quebec H2L 4M1, Canada.
Journal of Clinical Investigation (Impact Factor: 13.22). 01/2005; 114(12):1762-73. DOI: 10.1172/JCI21846
Source: PubMed


So far, there is very limited knowledge about the role of Eph kinases, the largest family of receptor tyrosine kinases, in the immune system. Here, using EphB6(-/-) mice, we demonstrated that in vitro and in vivo T cell responses such as lymphokine secretion, proliferation, and the development of delayed-type skin hypersensitivity and experimental autoimmune encephalitis in EphB6(-/-) mice were compromised. On the other hand, humoral immune responses, such as serum levels of different Ig isotypes and IgG response to tetanus toxoid, were normal in these mice. Mechanistically, we showed that EphB6 migrated to the aggregated TCRs and rafts after TCR activation. Further downstream, in the absence of EphB6, ZAP-70 activation, LAT phosphorylation, the association of PLCgamma1 with SLP-76, and p44/42 MAPK activation were diminished. Thus, we have shown that EphB6 is pivotal in T cell function.

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    • "Cytosolic and nuclear extracts of these cells were prepared with NE-PER nuclear and cytoplasmic extraction kit (Pierce Biotechnology, Rockford , IL) according to the manufacturer's instructions. Various proteins in these extracts were detected by immunoblotting, as described previously [15]. The following antibodies (Abs) were deployed for immunoblotting: rabbit Abs against histone H3 and Ran (Santa Cruz Biotechnology, Santa Cruz, CA); rabbit Abs against c-Jun, c-Fos and monoclonal antibody (mAb) against b-actin (Cell Signalling, Beverly, MA). "
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    ABSTRACT: Ran (Ras-related nuclear protein), a Ras family GTPase, is involved in multiple cellular functions, including the regulation of DNA replication, cell cycle progression, nuclear structure formation, RNA processing-exportation, and nuclear protein importation. Ran(+/-) embryonic stem (ES) cells were produced in an attempt to generate Ran null mutant mice. Even after an extremely large number of blastocyst injections, no Ran(+/-) chimeric mice could be generated. Ran(+/-) ES cell-derived fibroblasts showed reduced Ran protein expression, and manifested augmented nuclear abundance of AP-1 factors (c-Jun and c-Fos) upon cytokine stimulation. Our experiments demonstrated that intracellular Ran protein levels controlled the nuclear presence of certain transcription factors, such as c-Fos and c-Jun.
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    • "EphA10 is a recently described Eph receptor in humans [25] and there is not previous work on its functional roles. By contrast, EphB6 has been only associated with T lymphocytes [26], in which it seems to be involved in cell signalling [8] [19] [20] [27]. Thus, although not previously described in B lymphocytes, this molecule could be also involved in B-cell activation and, as it will be later discussed, Eph B6 emerges from the current results as a good molecular marker for CLL prognosis. "
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    ABSTRACT: Increasing information relates some Eph receptors and their ligands, ephrins (EFN), with the immune system. Herein, we found that normal B-cells from peripheral blood (PB) and lymph nodes (LN) showed a differential expression of certain Eph/EFN members, some of them being modulated upon in vitro stimulation including EFNA1, EFNA4, EphB6 and EphA10. In contrast, PB CLL B-cells showed a more heterogeneous Eph/EFN profile than their normal PB B-cell counterparts, expressing Eph/EFN members frequently found within the LN and activated B-cells, specially EFNA4, EphB6 and EphA10. Two of them, EphB6 and EFNA4 were further related with the clinical course of CLL patients. EphB6 expression correlated with a high content of ZAP-70 mRNA and a poor prognosis. High serum levels of a soluble EFNA4 isoform positively correlated with increasing peripheral blood lymphocyte counts and lymphadenopathy. These findings suggest that Eph/EFN might be relevant in normal B-cell biology and could represent new potential prognostic markers and therapeutic targets for CLL.
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    • "EphrinB1 activates EphB receptors to generate adhesive or repulsive signals through the modulation of integrin activation and actin cytoskelton rearrangement. In the immunological sphere, various types of ephrinB and EphB receptors have been detected in immune cells (31), and the activation of EphB receptors might be involved in the regulation of the immune system (12, 21, 25, 27, 29 ). In fact, we demonstrate here using an eph- rinB1/Fc fusion protein that ephrinB1 itself has no chemotactic activity but effectively stimulates the SDF-1-dependent migration of PBLs in a dose-dependent manner (Fig. 3A ). "
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