Description
GOPC, also known as PIST, interacts specifically with TC1 (a Rho-family small GTPase)] as a binding partner for Rhotekin. Rhotekin associates with PIST in vitro and both polarized and non-polarized MDCK (Madin-Darby canine kidney) cells. The C-terminal SPV (Ser-Pro-Val) motif of Rhotekin binds to the PDZ domain of PIST. The co-localization of PIST and Rhotekin at the Golgi apparatus can be detected in non-polarized fibroblast-like MDCK cells and AJs (adherens junctions) in the fully polarized cells. PIST and Rhotekin are recruited from the cytosol to AJs as the cell becomes polarized. Expression of constitutively active Rho or prevention of Rhotekin-PIST interaction induced diffuse cytoplasmic distribution of Rhotekin in polarized MDCK cells. GOPC may regulate CFTR chloride currents and acid-induced ACCN3 currents by modulating cell surface expression of both channels. It may also regulate the intracellular trafficking of the ADR1B receptor. GOPC is ubiquitously expressed and its overexpression results in CFTR intracellular retention and degradation in the lysosomes