HEK293 cells co-transfected with TRPV6 and the tyrosine phosphatase PTP1B show a constitutive Ca2+ entry which was independent of tyrosine phosphorylation under resting conditions. Following depletion of intracellular Ca2+ stores, TRPV6-mediated Ca2+ entry could be increased in the presence of a tyrosine phosphatase inhibitor (bis-(N,N-dimethyl-hydroxamido) hydroxo-vanadate; DMHV). Inhibition of Src-kinases completely abolished DMHV-induced increase in TRPV6-mediated Ca2+ influx. Co-transfection with Src led to tyrosine phosphorylation of TRPV6 which could be dephosphorylated by PTP1B.
In vivo interaction of TRPV6 with PTP1B was visualized using the bimolecular fluorescence complementation (BiFC) method and proved by co-immunoprecipitation of both proteins.
These data indicate that tyrosine phosphorylation is involved in the regulation of the TRPV6 channel protein.