Identification of protein kinase C phosphorylation sites involved in desensitization of the histamine H1 receptor

Abstract

We studied whether direct phosphorylation plays a key role in protein kinase C-activating phorbol estermediated H₁ receptor desensitization. Several potential protein kinase C-mediated phosphorylation sites were located in the third cytoplasmic loop form our cloning studies of H₁ receptors. Ser³⁹⁶ and Ser³⁹⁸ were determined to be the phosphorylation sites by in vitro phosphorylation studies using synthetic peptides corresponding to the partial amino acid sequence of the third cytoplasmic loop. Mutant H₁ receptors whose Ser³⁹⁶ or Ser³⁹⁸ were displaced by alanine were expressed in Chinese hamster ovary cells by site-directed mutagenesis. Characterization of these receptors revealed that Ser³⁹⁸, but not Ser³⁹⁶, was primarily responsible for protein kinase C-mediated H₁ receptor desensitization.