The protein kinase Cδ catalytic fragment targets Mcl-1 for degradation to trigger apoptosis
The protein kinase Cδ catalytic fragment targets Mcl-1 for degradation to trigger apoptosis
复制标题
DOI：
10.1074/jbc.m607351200
复制
发表时间：
2006-10-06
影响因子：
4.8
通讯作者：
Denning, Mitchell F.
中科院分区：
文献类型：
--
作者：
Sitailo, Leonid A.;Tibudan, Shalini S.;Denning, Mitchell F.
多种基因毒性剂（包括紫外线辐射）诱导的细胞凋亡需要蛋白水解裂解和随后的蛋白激酶 C (PKC) δ 激活。此外，组成型活性 PKC delta 催化片段 (PKC delta-cat) 的过度表达足以触发 Bax 激活、细胞色素 c 释放和细胞凋亡。虽然 PKC δ 是关键的凋亡效应子，但负责线粒体凋亡级联的下游靶标尚不清楚。我们发现 HaCaT 细胞中活性 PKC delta-cat 的表达会触发抗凋亡蛋白 Mcl-1 的减少，类似于紫外线辐射。 PKC delta-cat 诱导的 Mcl-1 下调并非在 mRNA 水平，而是由于蛋白质半衰期缩短。 Mcl-1 的过表达可保护 HaCaT 细胞免受 UV 和 PKC δ-cat 诱导的细胞凋亡，并阻止线粒体释放细胞色素 c，表明细胞凋亡信号传导需要 Mcl-1 下调。事实上，用 siRNA 下调 Mcl-1 会略微增加 HaCaT 细胞的基础凋亡率，并显着使其对 UV 或 PKC delta cat 诱导的细胞凋亡更加敏感。通过 Bax 交联测量，Mcl-1 下调的 HaCaT 细胞具有更高的活化 Bax 蛋白，表明 Mcl-1 下调足以激活 Bax。最后，重组 PKC δ 可以在体外磷酸化 Mcl-1，从而将 Mcl-1 确定为 PKC δ 的直接靶标。总的来说，我们的结果确定 Mcl-1 是 PKC delta-cat 的重要靶标，可以介导其对线粒体的促凋亡作用，从而放大由广泛的凋亡刺激诱导的凋亡信号传导。
Proteolytic cleavage and subsequent activation of protein kinaseC( PKC) delta is required for apoptosis induced by a variety of genotoxic agent, including UV radiation. In addition, overexpression of the constitutively active PKC delta catalytic fragment (PKC delta-cat) is sufficient to trigger Bax activation, cytochrome c release, and apoptosis. While PKC delta is a key apoptotic effector, the downstream target( s) responsible for the mitochondrial apoptotic cascade are not known. We found that expression of the active PKC delta- cat in HaCaT cells triggers a reduction in the antiapoptotic protein Mcl-1, similar to UV radiation. The downregulation of Mcl-1 induced by PKC delta- cat was not at the mRNA level but was due to decreased protein half- life. Overexpression of Mcl-1 protected HaCaT cells from both UV and PKC delta- catinduced apoptosis and blocked the release of cytochrome c from the mitochondria, indicating that Mcl-1 down- regulation was required for apoptosis signaling. Indeed, down- regulation of Mcl-1 with siRNA slightly increased the basal apoptotic rate of HaCaT cells and dramatically sensitized them to UV or PKC delta cat- induced apoptosis. HaCaT cells with down- regulated Mcl-1 had higher activated Bax protein, as measured by Bax cross-linking, indicating that Mcl-1 down- regulation is sufficient for Bax activation. Finally, recombinant PKC delta could phosphorylate Mcl-1 in vitro, identifying Mcl-1 as a direct target for PKC delta. Overall our results identify Mcl-1 as an important target for PKC delta-cat that can mediate its pro- apoptotic effects on mitochondria to amplify the apoptotic signaling induced by a wide range of apoptotic stimuli.