Pacher Pál, Sharma Kumar, Csordás György, Zhu Yanqing, Hajnóczky György
Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Am J Physiol Renal Physiol. 2008 Nov;295(5):F1303-12. doi: 10.1152/ajprenal.90343.2008. Epub 2008 Jul 23.
Transforming growth factor-beta (TGF-beta) has been implicated as a key factor in mediating many cellular processes germane to disease pathogenesis, including diabetic vascular complications. TGF-beta alters cytosolic [Ca2+] ([Ca2+]c) signals, which in some cases may result from the downregulation of the IP3 receptor Ca2+ channels (IP3R). Ca2+ released by IP3Rs is effectively transferred from endoplasmic reticulum (ER) to the mitochondria to stimulate ATP production and to allow feedback control of the Ca2+ mobilization. To assess the effect of TGF-beta on the ER-mitochondrial Ca2+ transfer, we first studied the [Ca2+]c and mitochondrial matrix Ca2+ ([Ca2+]m) signals in single preglomerular afferent arteriolar smooth muscle cells (PGASMC). TGF-beta pretreatment (24 h) decreased both the [Ca2+]c and [Ca2+]m responses evoked by angiotensin II or endothelin. Strikingly, the [Ca2+]m signal was more depressed than the [Ca2+]c signal and was delayed. In permeabilized cells, TGF-beta pretreatment attenuated the rate but not the magnitude of the IP(3)-induced [Ca2+]c rise, yet caused massive depression of the [Ca2+]m responses. ER Ca2+ storage and mitochondrial uptake of added Ca2+ were not affected by TGF-beta. Also, TGF-beta had no effect on mitochondrial distribution and on the ER-mitochondrial contacts assessed by two-photon NAD(P)H imaging and electron microscopy. Downregulation of both IP3R1 and IP3R3 was found in TGF-beta-treated PGASMC. Thus, TGF-beta causes uncoupling of mitochondria from the ER Ca2+ release. The sole source of this would be suppression of the IP3R-mediated Ca2+ efflux, indicating that the ER-mitochondrial Ca2+ transfer depends on the maximal rate of Ca2+ release. The impaired ER-mitochondrial coupling may contribute to the vascular pathophysiology associated with TGF-beta production.
转化生长因子-β（TGF-β）被认为是介导许多与疾病发病机制相关的细胞过程的关键因素，包括糖尿病血管并发症。TGF-β会改变胞质[Ca2+]（[Ca2+]c）信号，在某些情况下，这可能是由于肌醇三磷酸受体Ca2+通道（IP3R）下调所致。IP3R释放的Ca2+有效地从内质网（ER）转移到线粒体，以刺激ATP生成并实现对Ca2+动员的反馈控制。为了评估TGF-β对内质网-线粒体Ca2+转移的影响，我们首先研究了单个入球小动脉前平滑肌细胞（PGASMC）中的[Ca2+]c和线粒体基质Ca2+（[Ca2+]m）信号。TGF-β预处理（24小时）降低了血管紧张素II或内皮素引起的[Ca2+]c和[Ca2+]m反应。令人惊讶的是，[Ca2+]m信号比[Ca2+]c信号更受抑制且延迟出现。在通透细胞中，TGF-β预处理减弱了IP(3)诱导的[Ca2+]c升高的速率，但不影响其幅度，然而却导致[Ca2+]m反应大幅降低。内质网Ca2+储存和添加Ca2+后的线粒体摄取不受TGF-β影响。此外，TGF-β对线粒体分布以及通过双光子NAD(P)H成像和电子显微镜评估的内质网-线粒体接触没有影响。在TGF-β处理的PGASMC中发现IP3R1和IP3R3均下调。因此，TGF-β导致线粒体与内质网Ca2+释放解偶联。其唯一原因可能是IP3R介导的Ca2+外流受到抑制，这表明内质网-线粒体Ca2+转移依赖于Ca2+释放的最大速率。内质网-线粒体偶联受损可能导致与TGF-β产生相关的血管病理生理过程。
