Medical Cell Biology, University of Regensburg, Regensburg, Germany.
Endocrinology. 2020 Oct 1;161(10). doi: 10.1210/endocr/bqaa135.
The physiological stimulation of aldosterone production in adrenocortical glomerulosa cells by angiotensin II and high plasma K+ depends on the depolarization of the cell membrane potential and the subsequent Ca2+ influx via voltage-activated Ca2+ channels. Germline mutations of the low-voltage activated T-type Ca2+ channel CACNA1H (Cav3.2) have been found in patients with primary aldosteronism. Here, we investigated the electrophysiology and Ca2+ signaling of adrenal NCI-H295R cells overexpressing CACNA1H wildtype and mutant M1549V in order to understand how mutant CACNA1H alters adrenal cell function. Whole-cell patch-clamp measurements revealed a strong activation of mutant CACNA1H at the resting membrane potential of adrenal cells. Both the expression of wildtype and mutant CACNA1H led to a depolarized membrane potential. In addition, cells expressing mutant CACNA1H developed pronounced action potential-like membrane voltage oscillations. Ca2+ measurements showed an increased basal Ca2+ activity, an altered K+ sensitivity, and abnormal oscillating Ca2+ changes in cells with mutant CACNA1H. In addition, removal of extracellular Na+ reduced CACNA1H current, voltage oscillations, and Ca2+ levels in mutant cells, suggesting a role of the partial Na+ conductance of CACNA1H in cellular pathology. In conclusion, the pathogenesis of stimulus-independent aldosterone production in patients with CACNA1H mutations involves several factors: i) a loss of normal control of the membrane potential, ii) an increased Ca2+ influx at basal conditions, and iii) alterations in sensitivity to extracellular K+ and Na+. Finally, our findings underline the importance of CACNA1H in the control of aldosterone production and support the concept of the glomerulosa cell as an electrical oscillator.
醛固酮的产生受到生理刺激，在肾上腺球状带细胞中的血管紧张素 II 和高血浆 K+的作用下，这取决于细胞膜电位的去极化和随后通过电压激活的 Ca2+通道的 Ca2+内流。在原发性醛固酮增多症患者中，已经发现低电压激活 T 型 Ca2+通道 CACNA1H（Cav3.2）的种系突变。在这里，我们研究了过表达 CACNA1H 野生型和突变型 M1549V 的肾上腺 NCI-H295R 细胞的电生理学和 Ca2+信号转导，以了解突变型 CACNA1H 如何改变肾上腺细胞的功能。全细胞膜片钳测量显示，突变型 CACNA1H 在肾上腺细胞的静息膜电位下被强烈激活。野生型和突变型 CACNA1H 的表达都导致膜电位去极化。此外，表达突变型 CACNA1H 的细胞会产生明显的动作电位样膜电压振荡。Ca2+测量显示，突变型 CACNA1H 细胞中的基础 Ca2+活性增加，K+敏感性改变，Ca2+振荡异常。此外，去除细胞外 Na+会减少突变细胞中的 CACNA1H 电流、电压振荡和 Ca2+水平，表明 CACNA1H 的部分 Na+电导在细胞病变中起作用。总之，CACNA1H 突变患者中刺激非依赖性醛固酮产生的发病机制涉及几个因素：i）膜电位的正常控制丧失，ii）基础条件下 Ca2+内流增加，iii）对细胞外 K+和 Na+的敏感性改变。最后，我们的发现强调了 CACNA1H 在醛固酮产生控制中的重要性，并支持了球状带细胞作为电振荡器的概念。
