Structure and function of TRP channels

Transient receptor potential (TRP) channels encompass a diverse class of non-selective
cation channels that are primarily grouped by sequence homology to an ion channel
discovered in the light transduction pathway of fly photoreceptors. Emphasis on gene
sequence and protein domains rather than a functional classification scheme is necessary
given the broad array of physiological roles for these channels as well as theirmodes of
activation. To date, approximately 30 mammalian orthologues of the original fly TRP
have been identified, and these have been further classified into six sub-groups: TRPC,
TRPV, TRPA, TRPM, TRPP and TRPML. Functional characterization by electrophysiology
andmutational or chimeric analysis have been the cornerstone of advancing
our knowledge about TRP channels. A recent wave of TRP channel structures has
confirmed many of the keenest observations from electrophysiology experiments and
provided fertile starting ground for a newwave of functional analysis.This chapter aims
to consolidate an understanding of TRP channel function with the growing number of
TRP channel structures that are being solved at an incredible pace. In these structures,
4TRPsubunits assemble into a pore-forming ion channel, andeachsubunit is defined by
six transmembrane segments separated into a pore domain and voltage sensor-like
domain, common to the voltage-gated ion channel super-family. A high degree of
structural similarity in the transmembrane region will be the backdrop to a discussion on
general principles of gating, lipid interactions, Ca2+ dependent modulation and cell
signaling in the TRP channel family.