Preferential selection of Arginine at the lipid-water-interface of TRPV1 during vertebrate evolution correlates with its snorkeling behaviour and cholesterol interaction

Somdatta Saha,Abhishek Kumar,Nikhil Tiwari,Arijit Ghosh,Ashutosh Kumar,Chandan Goswami

doi:10.1038/s41598-017-16780-w

Abstract

TRPV1 is a thermo-sensitive ion channel involved in neurosensory and other physiological functions. The trans-membrane helices of TRPV1 undergo quick and complex conformational changes governed by thermodynamic parameters and membrane components leading to channel opening. However, the molecular mechanisms underlying such events are poorly understood. Here we analysed the molecular evolution of TRPV1 at the lipid-water-interface region (LWI), typically defined as a layer of 6 Å thickness on each side of the membrane with less availability of free water. Amino acids demarcating the end of the trans-membrane helices are highly conserved. Residues present in the inner leaflet are more conserved and have been preferentially selected over others. Amino acids with snorkeling properties (Arginine and Tyrosine) undergo specific selection during the vertebrate evolution in a cholesterol-dependent and/or body temperature manner. Results suggest that H-bond formation between the OH- group of cholesterol and side chain of Arg557 or Arg575 at the inner leaflet is a critical parameter that can regulate channel functions. Different LWI mutants of TRPV1 have altered membrane localization and deficient colocalization with lipid raft markers. These findings may help to understand the lipid-protein interactions, and molecular basis of different neuronal functions. Such findings may have broad importance in the context of differential sensory responses, pathophysiologies, and application of pharmacological drugs such as anaesthetics acting on TRPVs.

Highlights

Transient Receptor Potential (TRP) channels are one of the most versatile eukaryotic ion channels in nature
Such analysis opens up the importance of cholesterol in the molecular function of TRPV1 and suggests that physical interaction of cholesterol with key Arg residues located at the lipid-water interface may be critical for the stabilization as well as conformational dynamics required for TRPV1 channel functions
Analysis of different isoforms of TRPV1 sequences reveal the overall conservation of amino acids in the lipid-water interface (LWI) regions

Summary

Introduction

Transient Receptor Potential (TRP) channels are one of the most versatile eukaryotic ion channels in nature. This is in full agreement with the reports suggesting that Capsaicin binds to the intracellular loop region joining 2nd and 3rd transmembrane region[19,20] This in general suggests that the loop regions of TRPV1 are critical for the channel functions and the physico-chemical properties of lipid-water interface have strong influences on the channel functions. This analysis is mainly based on the available high-resolution Cryo-EM structure of rat TRPV1, systematic analysis of conservation as well as preferential selection of certain amino acids present in lipid-water interface regions, and the physico-chemical behaviour of the selected amino acids in these microenvironments Such analysis opens up the importance of cholesterol in the molecular function of TRPV1 and suggests that physical interaction of cholesterol with key Arg residues located at the lipid-water interface may be critical for the stabilization as well as conformational dynamics required for TRPV1 channel functions

Methods

Results

Conclusion