Spatial Arrangement of TRPC1, 3 and 6 Channels in Rabbit Ventricular Cardiomyocytes

Abstract

Transient receptor potential canonical (TRPC) 1, 3 and 6 channels are mechanosensitive cation channels abundantly expressed in the mammalian heart. A physiological role of the channels in regulation of intracellular calcium and contractility in cardiomyocytes was proposed. Increased TRPC expression and activity was linked to cardiac hypertrophy and heart failure. Understanding the precise location of TRPCs is essential to investigations of their functional role in normal and diseased hearts. We studied the spatial arrangement of TRPC channels in left ventricular myocardium from sham and transverse aortic constriction (TAC) adult rabbit using single-molecule localization microscopy. We acquired 3-dimensional images from tissue labelled for TRPC1, 3 and 6, along with sarco/endoplasmic reticulum ATPase (SERCA) as a marker of sarcoplasmic reticulum (SR) or wheat germ agglutinin (WGA) as a marker of sarcolemma including transverse tubular system. Proximity of TRPCs with SERCA and WGA was quantified with nearest neighbor analyses. The images revealed that TRPC1, 3 and 6 localize in intracellular regularly distributed striations. We found high proximity of TRPC1, 3 and 6 with SERCA and lower proximity with WGA in sham animals. In TAC animals we found decreased proximity of TRPCs with SERCA. Our studies suggest that TRPC1, 3 and 6 reside in the SR membrane in adult rabbit cardiomyocytes. This finding agrees with our functional studies testing the hypothesis that TRPC channels act as mechanical modulators of SR calcium content. We also revealed spatial remodeling associated with cardiac hypertrophy. Our study sheds light on the physiological function of TRPCs in cardiomyocytes and their role in hypertrophic remodeling in cardiac disease.