Phospholipase Cgamma2 dosage is critical for B cell development in the absence of adaptor protein BLNK.
B cell linker (BLNK) protein and phospholipase Cgamma2 (PLCgamma2) are components of the BCR signalosome that activate calcium signaling in B cells. Mice lacking either molecule have a severe but incomplete block in B lymphopoiesis. In this study, we generated BLNK-/- PLCgamma2-/- mice to examine the effect of simultaneous disruption of both molecules on B cell development. We showed that BLNK-/- PLCgamma2-/- mice had compounded defects in B cell maturation compared with either single mutant, suggesting that these two molecules cooperatively or synergistically signaled B lymphopoiesis. However, Ig H chain allelic exclusion was maintained in single and double mutants, indicating that signals propagated by BLNK and PLCgamma2 were not involved in this process. Interestingly, in the absence of BLNK, B cell development was dependent on plcgamma2 gene dosage. This was evidenced by the proportionate decrease in splenic B cell population and increase in bone marrow surface pre-BCR+ cells in PLCgamma2-diploid, -haploid, and -null animals. Intracellular calcium signaling and ERK activation in response to BCR engagement were also proportionately decreased and delayed, respectively, with stepwise reduction of plcgamma2 dosage in a BLNK(null) background. Thus, these data indicate the importance of BLNK not only as a conduit to specifically channel BCR-signaling pathways and as a scaffold for the assembling of macromolecular complex, but also as an efficient aggregator or concentrator of PLCgamma2 molecules to effect optimal signaling for B cell generation and activation.
Laboratory of Immunology, Center for Molecular Medicine and Institute of Molecular and Cell Biology, Singapore.
Shengli
S
Xu
Jianxin
J
Huo
Weng-Keong
WK
Chew
Masaki
M
Hikida
Tomohiro
T
Kurosaki
Kong-Peng
KP
Lam
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology* / Q000201:enzymology* / Q000276:immunology; D020013:Calcium Signaling; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D004789:Enzyme Activation; D018628:Gene Dosage; D015326:Gene Rearrangement, B-Lymphocyte, Heavy Chain; D066298:In Vitro Techniques; D038041:Lymphopoiesis; D020935:MAP Kinase Signaling System; D051379:Mice; D018345:Mice, Knockout; D051966:Phospholipase C gamma / Q000172:deficiency* / Q000235:genetics* / Q000378:metabolism; D010750:Phosphoproteins / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; C113939:B cell linker protein; D002352:Carrier Proteins; D010750:Phosphoproteins; D051966:Phospholipase C gamma