PHOSPHORYLATION OF TYROSYL RESIDUES-350/354 OF THE BETA-ADRENERGIC-RECEPTOR IS OBLIGATORY FOR COUNTERREGULATORY EFFECTS OF INSULIN

Insulin stimulates a loss of function and increased phosphotyrosine content of the beta(2)-adrenergic receptor in intact cells, raising the possibility that the beta(2)-receptor itself is a substrate for the insulin receptor tyrosine kinase. Phosphorylation of synthetic peptides corresponding to cytoplasmic domains of the beta(2)-adrenergic receptor by the insulin receptor in vitro and peptide mapping of the beta(2)-adrenergic receptor phosphorylated in vivo in cells stimulated by insulin reveal tyrosyl residues 350/354 and 364 in the cytoplasmic, C-terminal region of the beta(2)-adrenergic receptor as primary targets. Mutation of tyrosyl residues 350, 354 (double mutation) to phenylalanine abolishes the ability of insulin to counterregulate beta-agonist stimulation of cyclic AMP accumulation. Phenylalanine substitution of tyrosyl reside 364, in contrast, abolishes beta-adrenergic stimulation itself.