Amino acids critical for lipid/s-interaction at the lipid-water-interface of TRPV5/TRPV6 remain different during vertebrate radiation: Relevance in cancer, bone disorders and other pathophysiologies

Abstract

TRPV5 and TRPV6 are members of the TRP superfamily of ion channels and are present in almost all vertebrates as linked-genes with high homology and functional similarities. Abnormalities in the regulation or function of these two channels cause multiple pathological conditions, making these highly relevant for several diseases and pharmacological applications. In this context, how these two channels differ from each other is largely unknown. Here we analysed ∼250 protein sequences from vertebrates and critically analysed the conservation of signature motifs, such as different domains, TM-regions, loop-regions, cholesterol-binding regions and lipid-water-interface (LWI) regions. We demonstrate the subtle differences in the motifs and residues that are present at the LWI in TRPV5 and TRPV6. The ratio of hydrophobic-to-hydrophilic residues (but not of positive-to-negative residues) remains conserved for TRPV5 and TRPV6 throughout the vertebrate evolution. We also found motifs where cholesterol and/or sphingolipid can interact with TRPV5 and TRPV6 yet with different energies, both in open- and close-conformation. Accordingly, experimental evidence suggest that partial depletion of membrane cholesterol lowers the agonist-mediated opening of TRPV6, confirming the importance of membrane cholesterol for channel function. Further analysis of somatic mutations suggests that the specific inner LWI regions of TRPV5 (first 3) and TRPV6 (first 5) impose mutational hot-spots that are linked with different cancers. These findings may have broad significance in designing pharmacological agents for targeting TRPV5 and TRPV6 separately or simultaneously.