The 180000 molecular weight plasma membrane insulin receptor substrate is a protein tyrosine phosphatase and is elevated in diabetic plasma membranes.
Wheat germ agglutinin-purified non-diabetic and diabetic human placenta membranes were or were not depleted of EGF receptor with monoclonal anti-EGF receptor antibody B1D8, and subsequently phosphorylated. Phosphorylated insulin receptor beta-subunit was lower and pp180 was higher in diabetic placenta membranes than in non-diabetic membranes. Phosphorylated-beta-subunit was also lower in diabetic (streptozotocin-induced) rat liver whereas the amount of pp180 was dependent on membrane protein concentration. When rat liver tyrosine-phosphorylated proteins were incubated 30 min, 4 degrees C with EDTA-terminated 32P-phosphorylation reaction mixtures of wheat germ agglutinin-purified rat liver proteins, less phosphorylated proteins were immunoprecipitated with antiphosphotyrosine. The decrease in tyrosine-phosphorylated products suggested that pp180 was a protein tyrosine phosphatase. Taken together, the results suggest that diabetic plasma membranes contain more tyrosine phosphatase than non-diabetic membranes.
Goren
H J
HJ
Department of Medical Biochemistry, Faculty of Medicine, University of Calgary, Alberta, Canada.
Boland
D
D
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002846:Chromatography, Affinity; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D005260:Female; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D008099:Liver / Q000378:metabolism*; D008970:Molecular Weight; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D011254:Pregnancy in Diabetics / Q000378:metabolism*; D017027:Protein Tyrosine Phosphatases / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D011972:Receptor, Insulin / Q000302:isolation & purification / Q000378:metabolism*; D012016:Reference Values; D014909:Wheat Germ Agglutinins
D007328:Insulin; D014909:Wheat Germ Agglutinins; D011972:Receptor, Insulin; D017027:Protein Tyrosine Phosphatases