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 co ntent of the beta(2)-adrenergic receptor in intact cells, raising the possibility that the beta(2)-receptor itself is a substrate for the in sulin receptor tyrosine kinase. Phosphorylation of synthetic peptides corresponding to cytoplasmic domains of the beta(2)-adrenergic recepto r by the insulin receptor in vitro and peptide mapping of the beta(2)- adrenergic receptor phosphorylated in vivo in cells stimulated by insu lin reveal tyrosyl residues 350/354 and 364 in the cytoplasmic, C-term inal region of the beta(2)-adrenergic receptor as primary targets. Mut ation of tyrosyl residues 350, 354 (double mutation) to phenylalanine abolishes the ability of insulin to counterregulate beta-agonist stimu lation of cyclic AMP accumulation. Phenylalanine substitution of tyros yl reside 364, in contrast, abolishes beta-adrenergic stimulation itse lf.