Negative control of store-operated Ca2+ influx by B cell receptor cross-linking.
An increase in the intracellular Ca(2+) concentration by B cell receptor (BCR) cross-linking plays important roles in the regulation of B cell functions. [Ca(2+)](i) is regulated by Ca(2+) release from the Ca(2+) store as well as store-operated Ca(2+) influx (SOC). Protein tyrosine kinases downstream of BCR cross-linking were shown to regulate the mechanism for Ca(2+) release. However, it remains elusive whether BCR cross-linking regulates SOC or not. In this study, we examined the effect of BCR cross-linking on thapsigargin-induced SOC in the DT40 B cells. We found that the SOC-mediated increase in intracellular Ca(2+) concentration was inhibited by BCR cross-linking. Using a membrane-potential-sensitive dye, we found that BCR cross-linking induced depolarization, which is expected to decrease the driving force of Ca(2+) influx and SOC channel conductance. When membrane potential was held constant by the transmembrane K(+) concentration gradient in the presence of valinomycin, the BCR-mediated inhibition of SOC was still observed. Thus, the BCR-mediated inhibition of SOC involves both depolarization-dependent and depolarization-independent mechanisms of SOC inhibition. The depolarization-independent inhibition of the SOC was abolished in Lyn-deficient, but not in Bruton's tyrosine kinase-, Syk- or SHIP (Src homology 2 domain containing phosphatidylinositol 5'-phosphatase)-deficient cells, indicating that Lyn is involved in the inhibition. These results show novel pathways of BCR-mediated SOC regulations.
Hashimoto
A
A
Department of Pharmacology, Graduate School of Medicine, University of Tokyo, Japan.
Hirose
K
K
Kurosaki
T
T
Iino
M
M
D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000378:metabolism; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism*; D002118:Calcium / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000276:immunology; D002460:Cell Line; D002645:Chickens; D015536:Down-Regulation / Q000187:drug effects / Q000276:immunology*; D007148:Immunoglobulin mu-Chains / Q000276:immunology; D007424:Intracellular Fluid / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D007476:Ionophores / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000276:immunology; D011947:Receptors, Antigen, B-Cell / Q000276:immunology* / Q000378:metabolism* / Q000502:physiology; D019284:Thapsigargin / Q000494:pharmacology; D014634:Valinomycin / Q000494:pharmacology; D019061:src-Family Kinases / Q000502:physiology
D000888:Antibodies, Anti-Idiotypic; D007148:Immunoglobulin mu-Chains; D007476:Ionophores; D011947:Receptors, Antigen, B-Cell; C044203:anti-IgM; D014634:Valinomycin; D019284:Thapsigargin; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D002118:Calcium