Uncoupling protein 3 (UCP3) modulates the activity of Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) by decreasing mitochondrial ATP production.
Uncoupling protein 3 (UCP3) modulates the activity of Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) by decreasing mitochondrial ATP production.
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DOI：
10.1074/jbc.m110.216044
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发表时间：
2011-09-16
期刊：
影响因子：
--
通讯作者：
Demaurex N
中科院分区：
文献类型：
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作者：
De Marchi U;Castelbou C;Demaurex N
解偶联蛋白UCP 2和UCP 3被认为催化Ca 2+进入线粒体内膜，但这一提议是有争议的，其他不相关的蛋白质已被确定为线粒体Ca 2+单向转运蛋白。为了阐明UCPs在线粒体Ca 2+处理中的作用，我们下调了HeLa细胞唯一解偶联蛋白UCP 3的表达，并用遗传编码的探针测量了胞质溶胶和细胞器中的Ca 2+和ATP水平。UCP 3沉默并没有改变透性化细胞的线粒体Ca 2+摄取。然而，在完整的细胞中，UCP 3耗竭增加线粒体ATP的产生，并强烈降低组胺引起的细胞质和线粒体Ca 2+升高。降低的Ca 2+升高是由于抑制了钙库操作的Ca 2+进入和减少了内质网（ER）Ca 2+库的消耗。UCP 3耗竭加速ER Ca 2+再填充动力学，表明肌浆网/内质网Ca 2+（SERCA）泵的活性增加。因此，SERCA抑制剂逆转了UCP 3耗竭对胞质、ER和线粒体Ca 2+响应的影响。我们的研究结果表明，UCP 3不是线粒体钙单向转运体，而是通过限制线粒体ATP的产生来负调节SERCA的活性。因此，UCP 3对线粒体Ca 2+的影响反映了影响细胞Ca 2+稳态的代谢改变。SERCA对线粒体ATP产生的敏感性表明，线粒体控制ER Ca 2+摄取和释放位点的局部ATP可用性。
The uncoupling proteins UCP2 and UCP3 have been postulated to catalyze Ca2+ entry across the inner membrane of mitochondria, but this proposal is disputed, and other, unrelated proteins have since been identified as the mitochondrial Ca2+ uniporter. To clarify the role of UCPs in mitochondrial Ca2+ handling, we down-regulated the expression of the only uncoupling protein of HeLa cells, UCP3, and measured Ca2+ and ATP levels in the cytosol and in organelles with genetically encoded probes. UCP3 silencing did not alter mitochondrial Ca2+ uptake in permeabilized cells. In intact cells, however, UCP3 depletion increased mitochondrial ATP production and strongly reduced the cytosolic and mitochondrial Ca2+ elevations evoked by histamine. The reduced Ca2+ elevations were due to inhibition of store-operated Ca2+ entry and reduced depletion of endoplasmic reticulum (ER) Ca2+ stores. UCP3 depletion accelerated the ER Ca2+ refilling kinetics, indicating that the activity of sarco/endoplasmic reticulum Ca2+ (SERCA) pumps was increased. Accordingly, SERCA inhibitors reversed the effects of UCP3 depletion on cytosolic, ER, and mitochondrial Ca2+ responses. Our results indicate that UCP3 is not a mitochondrial Ca2+ uniporter and that it instead negatively modulates the activity of SERCA by limiting mitochondrial ATP production. The effects of UCP3 on mitochondrial Ca2+ thus reflect metabolic alterations that impact on cellular Ca2+ homeostasis. The sensitivity of SERCA to mitochondrial ATP production suggests that mitochondria control the local ATP availability at ER Ca2+ uptake and release sites.