p32 protein levels are integral to mitochondrial and endoplasmic reticulum morphology, cell metabolism and survival.
p32 protein levels are integral to mitochondrial and endoplasmic reticulum morphology, cell metabolism and survival.
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DOI：
10.1042/bj20121829
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发表时间：
2013-08-01
期刊：
影响因子：
--
通讯作者：
Bogoyevitch MA
中科院分区：
文献类型：
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作者：
Hu M;Crawford SA;Henstridge DC;Ng IH;Boey EJ;Xu Y;Febbraio MA;Jans DA;Bogoyevitch MA
p32 [也称为 HABP1（乙酰透明质酸结合蛋白 1）、gC1qR（球状头结构域补体 1q 的受体）或 C1qbp（补体 1q 结合蛋白）] 先前已被证明具有线粒体和非线粒体定位和功能。在本研究中，我们首次证明内源性 p32 蛋白是 HeLa 细胞在控制和应激条件下的线粒体蛋白。在定义改变这些细胞中 p32 水平的影响时，我们证明 p32 的过度表达增加了线粒体原纤维。相反，siRNA 介导的 p32 敲除增强了线粒体断裂，同时线粒体融合介导蛋白 Mfn（线粒体融合蛋白）1 和 Mfn2 的可检测水平下降。通过透射电子显微镜进行更详细的超微结构分析，揭示了异常的线粒体结构，嵴较少和/或破碎，线粒体基质密度降低，以及更多的点状 ER（内质网），核糖体明显解离。线粒体生物能学分析表明，p32 耗尽后基础呼吸和氧化 ATP 周转能力显着降低。此外，siRNA介导的p32敲低导致对细胞死亡的不同应激依赖性影响，在高渗应激或顺铂处理下观察到细胞死亡增强，但在亚砷酸盐存在下细胞死亡减少。总而言之，我们的研究强调了 p32 蛋白在正常细胞条件下对线粒体和 ER 形态的关键贡献，以及 p32 蛋白在细胞代谢和各种应激反应中的重要作用。
p32 [also known as HABP1 (hyaluronan-binding protein 1), gC1qR (receptor for globular head domains complement 1q) or C1qbp (complement 1q-binding protein)] has been shown previously to have both mitochondrial and non-mitochondrial localization and functions. In the present study, we show for the first time that endogenous p32 protein is a mitochondrial protein in HeLa cells under control and stress conditions. In defining the impact of altering p32 levels in these cells, we demonstrate that the overexpression of p32 increased mitochondrial fibrils. Conversely, siRNA-mediated p32 knockdown enhanced mitochondrial fragmentation accompanied by a loss of detectable levels of the mitochondrial fusion mediator proteins Mfn (mitofusin) 1 and Mfn2. More detailed ultrastructure analysis by transmission electron microscopy revealed aberrant mitochondrial structures with less and/or fragmented cristae and reduced mitochondrial matrix density as well as more punctate ER (endoplasmic reticulum) with noticeable dissociation of their ribosomes. The analysis of mitochondrial bioenergetics showed significantly reduced capacities in basal respiration and oxidative ATP turnover following p32 depletion. Furthermore, siRNA-mediated p32 knockdown resulted in differential stress-dependent effects on cell death, with enhanced cell death observed in the presence of hyperosmotic stress or cisplatin treatment, but decreased cell death in the presence of arsenite. Taken together, our studies highlight the critical contributions of the p32 protein to the morphology of mitochondria and ER under normal cellular conditions, as well as important roles of the p32 protein in cellular metabolism and various stress responses.