Selective role of PKCbeta enzymatic function in regulating cell survival mediated by B cell antigen receptor cross-linking.
Cross-linking of the B cell antigen receptor (BCR) results in the activation of several protein tyrosine kinases leading to phospholipase C-gamma2-dependent phospholipid hydrolysis and Ca2+ mobilization, followed by activation of the protein kinase C (PKC) family members. Sustained Ca2+ release in B lymphocytes is dependent on the membrane localization and activation of the protein tyrosine kinase BTK. Ca2+ release is a tightly regulated process involving BTK membrane localization through its phosphorylation by PKCbeta. A selective role of PKCbeta in B cell signaling was first revealed by the characterization of PKCbeta knockout mice, which displayed decreased B cell proliferation in response to various mitogenic stimuli. However, it is not clear whether the B cell defects displayed by the PKCbeta knockout mice are due a B cell developmental defect or the scaffolding function of PKCbeta, resulting in a defect in the recruitment or formation of signal transducing complex molecules. Thus, in this report we investigated the effects of pharmacologic inhibition of the catalytic function of PKCbeta on B cell survival and growth. Treatment of Daudi B lymphoma cell line with a selective PKCbeta inhibitor, LY333531, inhibited anti-IgM-induced phosphorylation of BTK on Ser180 in a concentration-dependent manner, which was concomitant with an increase in BTK activation, and Ca2+ mobilization. In primary splenic B cells, LY333531 inhibited BCR-induced B cell proliferation, but did not affect basal or LPS-induced proliferation. Finally, LY333531 treatment resulted in the induction of apoptosis of anti-IgM-activated B cells, which corroborated with their inability to up-regulate pro-survival factors, Bcl-X(L) and Bcl-2. These results support the important and selective role of the PKCbeta enzymatic function in controlling Ca2+ release during BCR signaling leading to B lymphocyte survival and growth.
Venkataraman
Chandrasekar
C
Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA. venkataramanch@lilly.com
Chen
Xinyi Cynthia
XC
Na
Songqing
S
Lee
Linda
L
Neote
Kuldeep
K
Tan
Seng-Lai
SL
D000077329:Agammaglobulinaemia Tyrosine Kinase; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology*; D020013:Calcium Signaling / Q000187:drug effects; D002470:Cell Survival; D003432:Cross-Linking Reagents; D005260:Female; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D064546:Protein Kinase C beta; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism*
D003432:Cross-Linking Reagents; D007211:Indoles; D008301:Maleimides; D047428:Protein Kinase Inhibitors; D011947:Receptors, Antigen, B-Cell; C099154:ruboxistaurin; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; D011493:Protein Kinase C; D064546:Protein Kinase C beta