Programa de Fisiología y Biofísica, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Chile; Advanced Center for Chronic Diseases, Facultad de Ciencias Químicas y Farmacéuticas & Facultad Medicina, Universidad de Chile, Santiago 8380453, Chile.
Programa de Fisiopatología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Chile.
Biochim Biophys Acta Mol Cell Res. 2018 Feb;1865(2):289-296. doi: 10.1016/j.bbamcr.2017.11.001. Epub 2017 Nov 7.
The L-type calcium channel (LTCC) is an important determinant of cardiac contractility. Therefore, changes in LTCC activity or protein levels could be expected to affect cardiac function. Several studies describing LTCC regulation are available, but only a few examine LTCC protein stability. Polycystin-1 (PC1) is a mechanosensor that regulates heart contractility and is involved in mechanical stretch-induced cardiac hypertrophy. PC1 was originally described as an unconventional Gi/o protein-coupled receptor in renal cells. We recently reported that PC1 regulates LTCC stability in cardiomyocytes under stress; however, the mechanism underlying this effect remains unknown. Here, we use cultured neonatal rat ventricular myocytes and hypo-osmotic stress (HS) to model mechanical stretch. The model shows that the Cavβ2 subunit is necessary for LTCC stabilization in cardiomyocytes during mechanical stretch, acting through an AKT-dependent mechanism. Our data also shows that AKT activation depends on the G protein-coupled receptor activity of PC1, specifically its G protein-binding domain, and the associated Gβγ subunit of a heterotrimeric Gi/o protein. In fact, over-expression of the human PC1 C-terminal mutant lacking the G protein-binding domain blunted the AKT activation-induced increase in Cav1.2 protein in cardiomyocytes. These findings provide novel evidence that PC1 is involved in the regulation of cardiac LTCCs through a Giβγ-AKT-Cavβ2 pathway, suggesting a new mechanism for regulation of cardiac function.
L 型钙通道（LTCC）是心肌收缩力的重要决定因素。因此，LTCC 活性或蛋白水平的变化预计会影响心脏功能。有几项描述 LTCC 调节的研究，但只有少数研究检查 LTCC 蛋白稳定性。多囊蛋白 1（PC1）是一种机械感受器，可调节心脏收缩力，并参与机械拉伸诱导的心肌肥厚。PC1 最初在肾脏细胞中被描述为一种非常规的 Gi/o 蛋白偶联受体。我们最近报道 PC1 在应激下调节心肌细胞中的 LTCC 稳定性；然而，这种效应的机制尚不清楚。在这里，我们使用培养的新生大鼠心室肌细胞和低渗应激（HS）来模拟机械拉伸。该模型表明，在机械拉伸过程中，Cavβ2 亚基对于心肌细胞中的 LTCC 稳定是必需的，其通过 AKT 依赖性机制起作用。我们的数据还表明，AKT 激活取决于 PC1 的 G 蛋白偶联受体活性，具体而言是其 G 蛋白结合域以及异三聚体 Gi/o 蛋白的相关 Gβγ 亚基。事实上，表达缺乏 G 蛋白结合域的人 PC1 C 末端突变体，削弱了 AKT 激活诱导的心肌细胞中 Cav1.2 蛋白的增加。这些发现为 PC1 通过 Giβγ-AKT-Cavβ2 途径参与心脏 LTCC 调节提供了新的证据，提示心脏功能调节的一种新机制。
