Agonist-dependent interaction of the rat somatostatin receptor subtype 2 with cortactin-binding protein 1

We report here an interaction between the C terminus of the rat somatostatin receptor subtype 2 (SSTR2) and a protein that has recently been identified as contactin-binding protein 1 (CortBP1). Interaction is mediated by the PDZ (PSD-95/discs large/ZO-1) domain of CortBP1. As shown by in situ hybridization, SSTR2 and cortactin-binding protein are coexpressed in the rat brain. The association between SSTR2 and the PDZ-domain of CortBP1 was verified by overlay assays and by coprecipitation after transfection in human embryonic kidney (HEK) cells. Analysis by confocal microscopy indicates that CortBP1 is distributed diffusely throughout the cytosol in transfected cells and that it becomes concentrated at the plasma membrane when SSTR2 is present. This process is largely increased when the receptor is stimulated by somatostatin; as CortBP1 interacts with the C terminus of SSTR2, our data suggest that the binding of agonist to the receptor increase the accessibility of the receptor C terminus to the PDZ domain of CortBP1. Our data for the first time establish a link between a G-protein coupled receptor and constituents of the cytoskeleton.