Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA.
J Biol Chem. 2010 Apr 30;285(18):13678-84. doi: 10.1074/jbc.M109.096040. Epub 2010 Feb 26.
Members of the Bcl-2 protein family play a central role in the regulation of apoptosis. An interaction between anti-apoptotic Bcl-x(L) and the endoplasmic reticulum (ER)-localized inositol trisphosphate receptor Ca(2+) release channel (InsP(3)R) enables Bcl-x(L) to be fully efficacious as an anti-apoptotic mediator (White, C., Li, C., Yang, J., Petrenko, N. B., Madesh, M., Thompson, C. B., and Foskett, J. K. (2005) Nat. Cell Biol. 7, 1021-1028). Physiologically, Bcl-x(L) binds to the InsP(3)R to enhance its gating and Ca(2+) signaling. Here we have discovered that structurally related proteins Bcl-2 and Mcl-1 function similarly. Bcl-2, Mcl-1 and Bcl-x(L) bind with comparable affinity to the carboxyl termini of all three mammalian InsP(3)R isoforms with important functional consequences. Stable expression of Bcl-2 or Mcl-1 lowered ER Ca(2+) content and enhanced the rate of InsP(3)-mediated Ca(2+) release in response to submaximal InsP(3) stimulation in permeabilized wild-type DT40 cells but not in cells lacking InsP(3)R. In addition, expression of either Bcl-2 or Mcl-1 enhanced spontaneous InsP(3)R-dependent Ca(2+) oscillations and spiking in intact cells in the absence of agonist stimulation. Bcl-2- and Mcl-1-mediated protection from apoptosis induced by staurosporine or etoposide was enhanced in cells expressing InsP(3)R, demonstrating that their interactions with InsP(3)R enable Bcl-2 and Mcl-1 to be fully efficacious anti-apoptotic mediators. Our data suggest a molecular mechanism that is shared by several anti-apoptotic Bcl-2 proteins that provides apoptosis resistance by direct interactions at the ER with the InsP(3)R that impinges on cellular Ca(2+) homeostasis.
Bcl-2 蛋白家族的成员在细胞凋亡的调控中起着核心作用。抗凋亡 Bcl-x(L)与内质网 (ER)局部定位的三磷酸肌醇受体 Ca(2+)释放通道 (InsP(3)R)之间的相互作用使 Bcl-x(L)能够充分有效地作为抗凋亡介质发挥作用 (White, C., Li, C., Yang, J., Petrenko, N. B., Madesh, M., Thompson, C. B., and Foskett, J. K. (2005) Nat. Cell Biol. 7, 1021-1028)。在生理上，Bcl-x(L)与 InsP(3)R 结合以增强其门控和 Ca(2+)信号。在这里，我们发现结构相关的蛋白质 Bcl-2 和 Mcl-1 具有相似的功能。Bcl-2、Mcl-1 和 Bcl-x(L)以相似的亲和力与所有三种哺乳动物 InsP(3)R 同工型的羧基末端结合，具有重要的功能后果。在透化的野生型 DT40 细胞中，稳定表达 Bcl-2 或 Mcl-1 降低了 ER Ca(2+)含量，并增强了 InsP(3)介导的 Ca(2+)释放反应的速率，但在缺乏 InsP(3)R 的细胞中则没有。此外，在没有激动剂刺激的情况下，在完整细胞中，表达 Bcl-2 或 Mcl-1 增强了自发的 InsP(3)R 依赖性 Ca(2+)振荡和尖峰。在表达 InsP(3)R 的细胞中，Bcl-2 和 Mcl-1 介导的对 staurosporine 或依托泊苷诱导的细胞凋亡的保护作用增强，表明它们与 InsP(3)R 的相互作用使 Bcl-2 和 Mcl-1 成为完全有效的抗凋亡介质。我们的数据表明，几种抗凋亡 Bcl-2 蛋白具有共同的分子机制，通过与内质网的直接相互作用提供抗凋亡作用，这种相互作用作用于 InsP(3)R，影响细胞 Ca(2+)稳态。
