IDENTIFICATION AND CHARACTERIZATION OF THE GLUCAGON RECEPTOR FROM ADIPOSE-TISSUE

I-125-glucagon was directly cross-linked to its receptor in isolated a dipocyte plasma membranes using a UV irradiation procedure. This inves tigation resulted in identification of an adipocyte glucagon receptor complex of 62 kDa, present both in white and brown adipose tissues. Th e specificity of labeling was shown by interference of unlabeled hormo ne with incorporation of radioactive glucagon into 62 kDa species. Tre atment of adipose plasma membranes with N-glycanase resulted in appear ance of intermediate species, indicating that the glucagon receptor is modified with several N-linked oligosaccharide chains similarly to th e hepatic glucagon receptor. Peptide mapping of the affinity labeled a dipose membranes with Staphylococcus aureus V8 protease generated thre e distinct receptor fragments identical to that of the hepatic recepto r. Overall, the biochemical characterization of the rat adipocyte gluc agon receptor indicates that it closely resembles the hepatic glucagon receptor.