Biophysical Properties of Xenopus TRPV6 Channel and its Regulation by TRPC1

Abstract Transient Receptor Potential (TRP) ion channels are formed by either homomeric or heteromeric assembly of four TRP subunits that have six transmembrane domains (TM) and a P-loop located between TM5 and TM6 defining the channel pore. So far 30 different subunits classified in 6 families sharing as low as 20% homology, have been identified in mammals and about 20 in Xenopus. Although heterotetramers can be formed within a family, the assembly of subunits from members of different families was thought to be unlikely. We here propose that TRPV6 and TRPC1 subunits can co-assemble in the Xenopus oocyte. Western blots performed on naive oocytes lysates revealed that they express both TRPV6 and TRPC1 proteins. Furthermore, co-immunoprecipitation of tagged xTRPV6 and xTRPC1 proteins expressed in oocytes suggested a heteromeric assembly. In mammals, TRPV6 is mainly expressed in intestinal epithelia and in the placenta where it forms a homomeric channel with high calcium permeability whereas TRPC1 is a ubiq...