Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, PR China; Shanghai Skin Disease Hospital, Shanghai, 200050, PR China.
Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, PR China.
Cell Calcium. 2020 May;87:102171. doi: 10.1016/j.ceca.2020.102171. Epub 2020 Feb 7.
B-cell activating factor (BAFF) is a crucial survival factor for B cells, and excess BAFF contributes to development of autoimmune diseases. Recent studies have shown that rapamycin can prevent BAFF-induced B-cell proliferation and survival, but the underlying mechanism remains to be elucidated. Here we found that rapamycin inhibited human soluble BAFF (hsBAFF)-stimulated cell proliferation by inducing G-cell cycle arrest, which was through downregulating the protein levels of CDK2, CDK4, CDK6, cyclin A, cyclin D1, and cyclin E. Rapamycin reduced hsBAFF-stimulated cell survival by downregulating the levels of anti-apoptotic proteins (Mcl-1, Bcl-2, Bcl-xL and survivin) and meanwhile upregulating the levels of pro-apoptotic proteins (BAK and BAX). The cytostatic and cytotoxic effects of rapamycin linked to its attenuation of hsBAFF-elevated intracellular free Ca ([Ca]). In addition, rapamycin blocked hsBAFF-stimulated B-cell proliferation and survival by preventing hsBAFF from inactivating PTEN and activating the Akt-Erk1/2 pathway. Overexpression of wild type PTEN or ectopic expression of dominant negative Akt potentiated rapamycin's suppression of hsBAFF-induced Erk1/2 activation and proliferation/viability in Raji cells. Interestingly, PP242 (mTORC1/2 inhibitor) or Akt inhibitor X, like rapamycin (mTORC1 inhibitor), reduced the basal or hsBAFF-induced [Ca] elevations. Chelating [Ca] with BAPTA/AM, preventing [Ca] elevation using EGTA, 2-APB or verapamil, inhibiting CaMKII with KN93, or silencing CaMKII strengthened rapamycin's inhibitory effects. The results indicate that rapamycin inhibits BAFF-stimulated B-cell proliferation and survival by blunting mTORC1/2-mediated [Ca] elevations and suppressing Ca-CaMKII-dependent PTEN/Akt-Erk1/2 signaling pathway. Our finding underscores that rapamycin may be exploited for prevention of excessive BAFF-induced aggressive B-cell malignancies and autoimmune diseases.
B 细胞激活因子 (BAFF) 是 B 细胞的关键存活因子，过量的 BAFF 有助于自身免疫性疾病的发展。最近的研究表明，雷帕霉素可以阻止 BAFF 诱导的 B 细胞增殖和存活，但潜在的机制仍有待阐明。在这里，我们发现雷帕霉素通过诱导 G 期细胞周期阻滞来抑制人可溶性 BAFF (hsBAFF) 刺激的细胞增殖，这是通过下调 CDK2、CDK4、CDK6、细胞周期蛋白 A、细胞周期蛋白 D1 和细胞周期蛋白 E 的蛋白水平实现的。雷帕霉素通过下调抗凋亡蛋白 (Mcl-1、Bcl-2、Bcl-xL 和 survivin) 的水平，同时上调促凋亡蛋白 (BAK 和 BAX) 的水平，从而减少 hsBAFF 刺激的细胞存活。雷帕霉素的细胞生长抑制和细胞毒性作用与其减弱 hsBAFF 升高的细胞内游离钙 ([Ca]) 有关。此外，雷帕霉素通过阻止 hsBAFF 使 PTEN 失活并激活 Akt-Erk1/2 通路，阻断 hsBAFF 刺激的 B 细胞增殖和存活。野生型 PTEN 的过表达或显性失活 Akt 的异位表达增强了雷帕霉素对 hsBAFF 诱导的 Erk1/2 激活和 Raji 细胞增殖/活力的抑制作用。有趣的是，PP242(mTORC1/2 抑制剂)或 Akt 抑制剂 X，与雷帕霉素 (mTORC1 抑制剂) 一样，降低了基础或 hsBAFF 诱导的 [Ca] 升高。用 BAPTA/AM 螯合 [Ca]、用 EGTA、2-APB 或维拉帕米阻止 [Ca] 升高、用 KN93 抑制 CaMKII 或沉默 CaMKII 增强了雷帕霉素的抑制作用。结果表明，雷帕霉素通过抑制 mTORC1/2 介导的 [Ca] 升高和抑制 Ca-CaMKII 依赖性 PTEN/Akt-Erk1/2 信号通路来抑制 BAFF 刺激的 B 细胞增殖和存活。我们的发现强调，雷帕霉素可能被用于预防过度的 BAFF 诱导的侵袭性 B 细胞恶性肿瘤和自身免疫性疾病。
