TRP Channel Proteins and Signal Transduction

Abstract

TRP channel proteins constitute a large and diverse family of proteins that are expressed in many tissues and cell types. This family was designated TRP because of a spontaneously occurring Drosophila mutant lacking TRP that responded to a continuous light with a transient receptor potential (hence TRP). In addition to responses to light, TRPs mediate responses to nerve growth factor, pheromones, olfaction, mechanical, chemical, temperature, pH, osmolarity, vasorelaxation of blood vessels, and metabolic stress. Furthermore, mutations in several members of TRP-related channel proteins are responsible for several diseases, such as several tumors and neurodegenerative disorders. TRP-related channel proteins are found in a variety of organisms, tissues, and cell types, including nonexcitable, smooth muscle, and neuronal cells. The large functional diversity of TRPs is also reflected in their diverse permeability to ions, although, in general, they are classified as nonselective cationic channels. The molecular domains that are conserved in all members of the TRP family constitute parts of the transmembrane domains and in most members also the ankyrin-like repeats at the NH2 terminal of the protein and a "TRP domain" at the COOH terminal, which is a highly conserved 25-amino acid stretch with still unknown function. All of the above features suggest that members of the TRP family are "special assignment" channels, which are recruited to diverse signaling pathways. The channels' roles and characteristics such as gating mechanism, regulation, and permeability are determined by evolution according to the specific functional requirements.

Intrinsic light responses of retinal ganglion cells projecting to the circadian system

“…In this respect, the light-activated current in SCN-projecting RGCs resembles currents carried by certain ion channels of the trp family (cf. Clapham et al, 2001;Minke & Cook, 2002). Specifically, the I-V characteristics closely resemble those reported for the TRPC6 channel in A7r5 smooth muscle cells (Jung et al, 2002), the mTRP6 channel in vascular smooth muscle (Inoue et al, 2001), and the TRPC4 and TRPC5 channels expressed in embryonic kidney cells (Shaefer et al, 2000).…”

Behavioral plasticity in C. elegans: Paradigms, circuits, genes

“…Members of this family are implicated in a variety of diverse physiologic processes including phototransduction and thermotransduction (Minke and Cook, 2002). There are some intriguing features of the osm-9 null mutant phenotype that warrant further elaboration.…”

Emerging roles of TRPM6/TRPM7 channel kinase signal transduction complexes

“…Genetic screening in Drosophila melanogaster for proteins involved in light-induced Ca 2+ influx into photosensitive cells resulted in the discovery of the transient receptor potential (TRP) cation channel family (Hardie 2001;Minke and Cook 2002;Montell 2001;Montell et al 2002a). According to primary sequence similarity, the members of the TRP gene family are classified into six subfamilies: TRPCs (seven canonical or classical TRPs), TRPVs (six vanilloid receptor and related proteins), TRPMs (eight TRP proteins homologous to the first cloned mammalian subfamily member, melastatin; Montell et al 2002a,b;Clapham et al 2003), TRPA (a single gene is present in mammalian genomes, ANKTM1; Tominaga and Caterina 2004), and two groups of more distantly related proteins, TRPMLs (three proteins defined by the initially discovered gene mucolipin 1; Slaugenhaupt 2002) and TRPPs (polycystic kidney disease 2 related proteins; Cantiello 2004).…”