Transient Receptor Potential (TRP) ion channels are formed by the juxtaposition of either homomeric or heteromeric assembly of four TRP subunits. TRP proteins have six transmembrane domains (TM) and a P-loop located between TM5 and TM6 that defines the channel pore. So far 30 different subunits, sharing as low as 20% homology, have been identified in mammals and classified in 6 families. Although heterotetramers can be formed within a family, the assembly of subunits from members of different families was thought to be unlikely. Here using biochemical and electrophysiological techniques we evaluated the interaction between xTRPV6 and xTRPC1 overexpressed in Xenopus oocytes. Western blot analysis of oocytes lysates revealed that the native cells expressed both xTRPC1 and xTRPV6. Oocytes were then injected with RNA encoding the two subunits associated or not with protein tags to allow easier immunoprecipitation. The later experiments revealed that xTRPC1 and xTRPV6 expressed in oocytes co-immunoprecipitate. The expression of solely xTRPC1 did not result in a detectable ionic current, whereas xTRPV6 injected oocytes displayed large inward rectifying cationic currents. Ion substitution experiments revealed that the xTRPV6 channel was more permeable to Mg2+ ions than Ca2+, a characteristic opposite to its mammalian counterpart. Co-expression of both subunits resulted in an ionic current mainly carried by Mg2+ ions. Experiments are now being performed in oocytes and in a human cell line to help us further understand Mg2+ and Ca2+ homeostasis and the contribution of different TRP subunits assemblies to it.


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  1. R.J. Courjaret, S. Haun, K. Machaca, Multimerization of the transient receptor proteins TRPV6 and TRPC1, QFARF Proceedings, 2010, BMP1.
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