<P> These ion channels are relatively non-selectively permeable to cations, including sodium, calcium and magnesium . TRP channels were initially discovered in trp - mutant strain of the fruit fly Drosophila . Later, TRP channels were found in vertebrates where they are ubiquitously expressed in many cell types and tissues . Most TRP channels are composed of 6 membrane - spanning helices with intracellular N - and C - termini . Mammalian TRP channels are activated and regulated by a wide variety of stimuli and are expressed throughout the body . </P> <P> They are encoded by at least 28--30 channel subunit genes divided into seven sub-families: </P> <Dl> <Dt> Canonical (TRPC) </Dt> <Dd> Associated with focal segmental glomerulosclerosis . </Dd> <Dt> Vanilloid (TRPV) </Dt> <Dd> TRPV1 mediates the pungent odour and pain / hot sensations associated with capsaicin and piperine . </Dd> <Dt> Ankyrin (TRPA) </Dt> <Dd> Stress (mechanical) receptor . Disputed to be temperature - sensitive; activated by isothiocyanates (pungent chemicals in substances such as mustard oil and wasabi). </Dd> <Dt> Melastatin (TRPM) </Dt> <Dd> Associated with hypomagnesemia with secondary hypocalcemia . </Dd> <Dt> Polycystic (TRPP) </Dt> <Dd> Associated with polycystic kidney disease . </Dd> <Dt> Mucolipin (TRPML) </Dt> <Dd> Associated with mucolipidosis type IV . </Dd> <Dt> No mechanoreceptor potential C (NOMPC; TRPN) </Dt> <Dd> Not found in mammals . </Dd> </Dl> <Dt> Canonical (TRPC) </Dt>

The trp family of ion channels is principally responsive to