P2X1 receptor currents after disruption of the PKC site and its surroundings by dominant negative mutations in HEK293 cells.

It has been suggested that phosphorylation at the T18P19R20 PKC sites of the P2X1 receptor regulates its functions. Here, we show that mutation at T18 (T18A and T18N) almost abolishes P2X1 current in response to ATP and that mutations of R20T but not of P19V also decrease the P2X1 current. Immunoblotting with anti-Thr(P)-Pro monoclonal antibody of membrane proteins from HEK293 cells transfected with P2X1R20T indicate the absence of Thr(P)18 which is present in HEK293 cells transfected with WT P2X1. We conclude that T18P19R20 is phosphorylated following P2X1 binding of ligand but that the three PKC sites function to different degree.