标题：Bromophenacyl bromide binding to the actin-bundling protein l-plastin inhibits inositol trisphosphate-independent increase in Ca2+ in human neutrophils
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1994
卷号：91
期号：9
页码：3534-3538
DOI：10.1073/pnas.91.9.3534
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Ligation of IgG Fc receptors on polymorphonuclear leukocytes causes an increase in the concentration of free intracytoplasmic Ca2+ ([Ca2+]i) which arises from release of intracellular stores but is independent of inositol 1,4,5-trisphosphate. We found that bromophenacyl bromide (BPB), an alkylating agent which inhibits leukocyte degranulation, adherence, and phagocytosis, inhibited IgG-stimulated increases in [Ca2+]i with an IC50 of 0.2 microM. In contrast, BPB had no effect on inositol 1,4,5-trisphosphate-dependent [Ca2+]i increases induced by fMet-Leu-Phe, complement fragment C5a, ATP, or platelet-activating factor. Using a monoclonal antibody specific for BPB, we identified in polymorphonuclear leukocytes a single cytosolic protein of 66 kDa and isoelectric point pH 5.6 which bound BPB when intact cells were treated with the alkylating agent. This BPB-binding protein was identified as l-plastin, a Ca(2+)-regulated actin-bundling protein. l-Plastin was found associated with the Triton X-100-insoluble cytoskeleton in polymorphonuclear leukocytes adherent to immune complexes, suggesting that BPB affects Fc receptor-mediated signal transduction by altering the actin cytoskeleton. Consistent with this hypothesis, both cytochalasin B and cytochalasin D inhibited the IgG-dependent increase in [Ca2+]i, without any effect on fMet-Leu-Phe-induced Ca2+ release. These data suggest that the actin cytoskeleton is essential for signal transduction from plasma membrane Fc receptors and that l-plastin has a critical role in activation of this pathway.
