Page D M, DeFranco A L
Department of Microbiology and Immunology, University of California, San Francisco 94143.
J Immunol. 1988 Jun 1;140(11):3717-26.
Anti-IgM irreversibly inhibits the growth of WEHI-231 B lymphoma cells and induces phosphoinositide hydrolysis--producing diacylglycerol, which activates protein kinase C, inositol 1,4,5-trisphosphate, which induces the release of calcium from intracellular storage sites into the cytoplasm, and other inositol polyphosphates. The roles of two of the possible second messengers, cytoplasmic free calcium and diacylglycerol, in mediating the action of anti-IgM on WEHI-231 cells were assessed by elevating [Ca2+]i with ionomycin and by activating protein kinase C with phorbol 12,13-dibutyrate (PdBu). The combination of 250 nM ionomycin and 4 to 7 nM PdBu was found to cause growth arrest and cell volume decrease responses in WEHI-231 cells which were similar to those caused by anti-IgM, although clearly slower. Both anti-IgM and the combination of mimicking reagents induced growth arrest of WEHI-231 cells in the G1 phase of the cell cycle. In both cases, this growth arrest was mitigated by addition of bacterial LPS. Moreover, 250 nM ionomycin plus 4 to 7 nM PdBu did not inhibit the growth of two other murine B lymphoma cell lines, each of which did exhibit increased phosphoinositide hydrolysis but not growth arrest in response to anti-Ig. Taken together, these results suggest that ionomycin and PdBu, at the concentrations used, did not inhibit WEHI-231 growth by general toxicity, but rather by mimicking the effects of the natural second messengers generated from Ag receptor cross-linking. Thus, the phosphoinositide-derived second messengers Ca2+i and diacylglycerol are capable of playing important roles in mediating the action of anti-IgM on WEHI-231 B lymphoma cells. However, the response of WEHI-231 cells to anti-IgM could not be fully reproduced with ionomycin and phorbol diester. These results suggest that another second messenger induced by anti-IgM may also play an important role in mediating the growth arrest of these cells.
抗 IgM 不可逆地抑制 WEHI-231 B 淋巴瘤细胞的生长，并诱导磷酸肌醇水解，产生二酰基甘油（激活蛋白激酶 C）、肌醇 1,4,5-三磷酸（诱导细胞内储存部位的钙释放到细胞质中）以及其他肌醇多磷酸。通过用离子霉素升高 [Ca2+]i 和用佛波酯 12,13-二丁酸酯（PdBu）激活蛋白激酶 C，评估了两种可能的第二信使——细胞质游离钙和二酰基甘油在介导抗 IgM 对 WEHI-231 细胞作用中的作用。发现 250 nM 离子霉素和 4 至 7 nM PdBu 的组合会导致 WEHI-231 细胞生长停滞和细胞体积减小，这与抗 IgM 引起的反应相似，尽管明显较慢。抗 IgM 和模拟试剂组合均诱导 WEHI-231 细胞在细胞周期的 G1 期生长停滞。在这两种情况下，添加细菌脂多糖均可减轻这种生长停滞。此外，250 nM 离子霉素加 4 至 7 nM PdBu 并不抑制另外两种小鼠 B 淋巴瘤细胞系的生长，这两种细胞系在响应抗 Ig 时均表现出磷酸肌醇水解增加但无生长停滞。综上所述，这些结果表明，所用浓度的离子霉素和 PdBu 并非通过一般毒性抑制 WEHI-231 的生长，而是通过模拟由抗原受体交联产生的天然第二信使的作用。因此，磷酸肌醇衍生的第二信使 Ca2+i 和二酰基甘油能够在介导抗 IgM 对 WEHI-231 B 淋巴瘤细胞的作用中发挥重要作用。然而，离子霉素和佛波酯无法完全重现 WEHI-231 细胞对抗 IgM 的反应。这些结果表明，抗 IgM 诱导的另一种第二信使可能在介导这些细胞的生长停滞中也起重要作用。
