Zhao M, Eaton J W, Brunk U T
Division of Pathology II, Faculty of Health Sciences, Linköping University, Sweden.
FEBS Lett. 2001 Dec 14;509(3):405-12. doi: 10.1016/s0014-5793(01)03185-4.
B-cell leukemia/lymphoma 2 (Bcl-2) blocks oxidant-induced apoptosis at least partly by stabilizing lysosomes. Here we report that phosphorylation of Bcl-2 may be required for these protective effects. J774 cells overexpressing wild-type Bcl-2 resist oxidant-induced lysosomal leak as well as apoptosis, and this protection is amplified by pretreatment with phorbol 12-myristate 13-acetate (which promotes protein kinase C (PKC)-dependent phosphorylation of Bcl-2). In contrast, cells overexpressing the Bcl-2 mutant S70A (which cannot be phosphorylated) are not protected in either circumstance. Transfection with Bcl-2(S70E), a constitutively active Bcl-2 mutant which does not require phosphorylation, is protective independent of PKC activation. In contrast, C(2)-ceramide, a putative protein phosphatase 2A activator, abolishes the protective effects of wild-type Bcl-2 overexpression but does not diminish protection afforded by Bcl-2(S70E). Additional results suggest that, perhaps as a consequence of lysosomal stabilization, Bcl-2 may prevent activation of phospholipase A2, an event potentially important in the ultimate initiation of apoptosis.
B细胞白血病/淋巴瘤2（Bcl-2）至少部分地通过稳定溶酶体来阻断氧化剂诱导的细胞凋亡。在此我们报告，Bcl-2的磷酸化可能是这些保护作用所必需的。过表达野生型Bcl-2的J774细胞能抵抗氧化剂诱导的溶酶体渗漏以及细胞凋亡，并且用佛波酯12-肉豆蔻酸酯13-乙酸酯（其促进Bcl-2的蛋白激酶C（PKC）依赖性磷酸化）预处理可增强这种保护作用。相反，过表达不能被磷酸化的Bcl-2突变体S70A的细胞在这两种情况下均不受保护。用Bcl-2（S70E）（一种不需要磷酸化的组成型活性Bcl-2突变体）转染具有保护作用，且与PKC激活无关。相反，一种假定的蛋白磷酸酶2A激活剂C（2）-神经酰胺消除了野生型Bcl-2过表达的保护作用，但不减弱Bcl-2（S70E）提供的保护作用。其他结果表明，也许作为溶酶体稳定的结果，Bcl-2可能阻止磷脂酶A2的激活，这一事件在细胞凋亡的最终启动中可能很重要。
