Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, School of Medicine, Aurora, CO.
J Gen Physiol. 2020 Mar 2;152(3). doi: 10.1085/jgp.201912471.
Stomatin (STOM) is a monotopic integral membrane protein found in all classes of life that has been shown to regulate members of the acid-sensing ion channel (ASIC) family. However, the mechanism by which STOM alters ASIC function is not known. Using chimeric channels, we combined patch-clamp electrophysiology and FRET to search for regions of ASIC3 critical for binding to and regulation by STOM. With this approach, we found that regulation requires two distinct sites on ASIC3: the distal C-terminus and the first transmembrane domain (TM1). The C-terminal site is critical for formation of the STOM-ASIC3 complex, while TM1 is required only for the regulatory effect. We then looked at the mechanism of STOM-dependent regulation of ASIC3 and found that STOM does not alter surface expression of ASIC3 or shift the pH dependence of channel activation. However, a point mutation (Q269G) that prevents channel desensitization also prevents STOM regulation, suggesting that STOM may alter ASIC3 currents by stabilizing the desensitized state of the channel. Based on these findings, we propose a model whereby STOM is anchored to the channel via a site on the distal C-terminus and stabilizes the desensitized state of the channel via an interaction with TM1.
质膜蛋白 stomatin（STOM）是一种存在于所有生命形式中的单跨膜蛋白，已被证明可调节酸敏感离子通道（ASIC）家族的成员。然而，STOM 改变 ASIC 功能的机制尚不清楚。我们使用嵌合通道，结合膜片钳电生理学和 FRET 技术，寻找与 STOM 结合和调节至关重要的 ASIC3 区域。通过这种方法，我们发现调节需要 ASIC3 上的两个不同位点：远端 C 末端和第一个跨膜结构域（TM1）。C 末端位点对于形成 STOM-ASIC3 复合物至关重要，而 TM1 仅对于调节作用是必需的。然后，我们研究了 STOM 对 ASIC3 调节的机制，发现 STOM 不会改变 ASIC3 的表面表达，也不会改变通道激活的 pH 依赖性。然而，一个阻止通道脱敏的点突变（Q269G）也阻止了 STOM 的调节，这表明 STOM 可能通过稳定通道的脱敏状态来改变 ASIC3 电流。基于这些发现，我们提出了一个模型，即 STOM 通过远端 C 末端的一个位点锚定在通道上，并通过与 TM1 的相互作用稳定通道的脱敏状态。
