Demaree Isaac S, Kumar Sanjay, Tennessen Kayla, Hoang Quyen Q, White Fletcher A, Obukhov Alexander G
Department of Anatomy, Cell Biology & Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
Department of Life Science, School of Earth, Biological, and Environmental Sciences, Central University of South Bihar, Gaya 824236, India.
Cells. 2024 Dec 6;13(23):2019. doi: 10.3390/cells13232019.
TRPC5 proteins form plasma membrane cation channels and are expressed in the nervous and cardiovascular systems. TRPC5 activation leads to cell depolarization and increases neuronal excitability, whereas a homologous TRPC1 inhibits TRPC5 function via heteromerization. The mechanism underlying the inhibitory effect of TRPC1 in TRPC5/TRPC1 heteromers remains unknown.
We used electrophysiological techniques to examine the roles of subunit stoichiometry and positively charged luminal residues of TRPC1 on TRPC5/TRPC1 function. We also performed molecular dynamics simulations.
We found that increasing the relative amount of TRPC1 in TRPC5/TRPC1 heteromers reduced histamine-induced cation influx through the heteromeric channels. Consistently, histamine-induced cation influx was small in cells co-expressing TRPC5-TRPC1 concatemers and TRPC1, and large in cells co-expressing TRPC5-TRPC1 concatemers and TRPC5. Molecular dynamics simulations revealed that the TRPC1 protein has two positively charged lysine residues that are facing the heteromeric channel pore lumen. Substitution of these lysines with asparagines decreased TRPC1's inhibitory effect on TRPC5/TRPC1 function, indicating that these lysines may regulate cation influx through TRPC5/TRPC1 heteromers. Additionally, we established that extracellular Mg inhibits cation influx through TRPC5/TRPC1, contributing to channel regulation.
We revealed that the inhibitory effect of TRPC1 on heteromeric TRPC5/TRPC1 function likely involves luminal lysines of TRPC1.
瞬时受体电位通道蛋白5（TRPC5）形成质膜阳离子通道，在神经和心血管系统中表达。TRPC5激活导致细胞去极化并增加神经元兴奋性，而同源的瞬时受体电位通道蛋白1（TRPC1）通过异源二聚化抑制TRPC5功能。TRPC1对TRPC5/TRPC1异源二聚体抑制作用的潜在机制尚不清楚。
我们使用电生理技术研究TRPC1的亚基化学计量和带正电荷的腔内残基对TRPC5/TRPC1功能的作用。我们还进行了分子动力学模拟。
我们发现，增加TRPC5/TRPC1异源二聚体中TRPC1的相对含量可减少组胺诱导的通过异源通道的阳离子内流。同样，在共表达TRPC5-TRPC1串联体和TRPC1的细胞中，组胺诱导的阳离子内流较小，而在共表达TRPC5-TRPC1串联体和TRPC5的细胞中较大。分子动力学模拟显示，TRPC1蛋白有两个带正电荷的赖氨酸残基，它们面向异源通道孔腔。用天冬酰胺取代这些赖氨酸会降低TRPC1对TRPC5/TRPC1功能的抑制作用，表明这些赖氨酸可能调节通过TRPC5/TRPC1异源二聚体的阳离子内流。此外，我们确定细胞外镁可抑制通过TRPC5/TRPC1的阳离子内流，有助于通道调节。
我们揭示了TRPC1对异源TRPC5/TRPC1功能的抑制作用可能涉及TRPC1的腔内赖氨酸。
