PROTEIN-KINASE-C DEFICIENCY BLOCKS RECOVERY FROM AGONIST-INDUCED DESENSITIZATION

Protein phosphorylation is central. to agonist-induced attenuation of the function of G-protein-linked receptors. Stable expression of RNA a ntisense to specific protein kinase mRNAs permitted analysis of loss-o f-function mutants of A431 human epidermoid carcinoma cells, lacking p rotein kinase A, protein kinase C, or beta-adrenergic receptor kinase. Deficiency of protein kinase C, but not the others, amplified rather than attenuated agonist-induced desensitization. In wild-type cells, t he t1/2 for recovery from desensitization was similar to 25 min follow ing removal of agonist, In the protein kinase C-deficient cells, no re sensitization was observed even 60 min after agonist removal. Like pro tein kinase C-deficiency, inhibition of protein kinase C with bisindol ylmaleimide or calphostin C blocked resensitization. Resensitization w as suppressed by FK506, all inhibitor of protein phosphatase 2B, mimic king protein kinase C-deficiency, but in a non-additive manner, The da ta reveal protein kinase C and protein phosphatase 2B to be critical e lements of resensitization.