Enhanced expression of membrane phosphoproteins tyrosine phosphorylation in estrogen-induced kidney tumors.
We demonstrate for the first time that the expression of tyrosine containing membrane phosphoproteins is elevated in estrogen-induced kidney tumors, which is evident from both the types of experiments, i.e., alkali-resistant phosphorylation of membrane proteins and immunoprecipitation of tyrosine containing phosphoproteins. Tyrosine phosphorylation of proteins or peptides was modulated by the growth factors (EGF, IGF-I) and by the inhibitors of tyrosine protein kinase(s). The kinetic analyses revealed that tumor membranes have high affinity and catalytically more efficient tyrosine phosphorylating kinase enzyme(s) compared to that of normal membranes which have low affinity and catalytically less efficient kinase enzyme(s). It is proposed that overexpression of tyrosine containing membranal phosphoproteins may be involved in the induction and growth of estrogen-induced renal neoplasm.
Narayan
S
S
Center for Molecular Sciences, University of Texas Medical Branch, Galveston 77550.
Roy
D
D
D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D006224:Cricetinae; D004054:Diethylstilbestrol; D004591:Electrophoresis, Polyacrylamide Gel; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007668:Kidney / Q000201:enzymology*; D007680:Kidney Neoplasms / Q000139:chemically induced / Q000201:enzymology*; D007700:Kinetics; D008297:Male; D008647:Mesocricetus; D008970:Molecular Weight; D009363:Neoplasm Proteins / Q000302:isolation & purification / Q000378:metabolism; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000302:isolation & purification / Q000378:metabolism*; D011794:Quercetin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values
D009363:Neoplasm Proteins; D010750:Phosphoproteins; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D004054:Diethylstilbestrol; D011794:Quercetin; D011505:Protein-Tyrosine Kinases; D005033:Ethylmaleimide