PKC eta directs induction of IRF-4 expression and Ig kappa gene rearrangement in pre-BCR signaling pathway.
Pre-B cell receptor (pre-BCR) signals promote pre-B cell differentiation, in which the adaptor protein B-cell linker (BLNK) plays a crucial role. However, the molecular pathways downstream of BLNK are currently unclear. Utilizing pre-B leukemia cell lines (BKO84 and others) derived from BLNK-deficient mice as in vitro models of the pre-B cell differentiation, we have demonstrated that reconstitution of BLNK as well as an active form of protein kinase C (PKC)eta induces the differentiation events, such as pre-BCR down-regulation and kappa gene rearrangement. Here we show that the same events are induced by cross-linking of pre-BCR with anti-mu antibody in these pre-B cell lines, as well as in ex vivo pre-B cells from BLNK-deficient mice, suggesting a function of BLNK as an internal cross-linker of pre-BCR. Anti-mu treatment of BKO84 cells up-regulated membrane recruitment of PKC eta and the expression of IRF-4, a transcription factor known to promote light chain gene rearrangements. Anti-mu induction of surface kappa chain on BKO84 cells was blocked by reagents that inhibit phospholipase C or PKC. Enforced expression of the active PKC eta in BKO84 cells resulted in up-regulation of IRF-4 expression. Conversely, siRNA-mediated silencing of PKC eta expression strikingly attenuated the anti-mu-induced IRF-4 expression and kappa gene rearrangement, which were restored by PKC eta reconstitution. Finally, enforced expression of IRF-4, but not of BLNK, in the PKC eta-silenced BKO84 cells resulted in kappa gene rearrangement. These results indicate that PKC eta directs the induction of IRF-4 expression downstream of BLNK in the pre-BCR signaling pathway promoting kappa gene rearrangement.
Oda
Akihisa
A
Division of Molecular Biology, Tokyo University of Science, Noda, Chiba 278-0022, Japan.
Ono
Tomohiro
T
Yamamoto
Mutsumi
M
Goitsuka
Ryo
R
Kitamura
Daisuke
D
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D015536:Down-Regulation; D015328:Gene Rearrangement, B-Lymphocyte, Light Chain; D007148:Immunoglobulin mu-Chains / Q000378:metabolism; D050835:Interferon Regulatory Factors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D054448:Precursor Cells, B-Lymphoid / Q000276:immunology / Q000378:metabolism; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D011940:Receptor Aggregation; D011947:Receptors, Antigen, B-Cell / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology; D015533:Transcriptional Activation / Q000276:immunology; D000099218:Interferon Regulatory Factor-4
D048868:Adaptor Proteins, Signal Transducing; D007148:Immunoglobulin mu-Chains; D050835:Interferon Regulatory Factors; D011493:Protein Kinase C; D011947:Receptors, Antigen, B-Cell; D000099218:Interferon Regulatory Factor-4; C113939:B cell linker protein; C081975:protein kinase C eta