Concanavalin A (ConA) stimulated the phosphorylation of the beta-subunit of the insulin receptor and an Mr-185,000 protein on serine and tyrosine residues in intact H-35 rat hepatoma cells. This Mr-185,000 protein whose phosphorylation was stimulated by ConA was identical to pp185, a protein reported previously to be a putative endogenous substrate for the insulin receptor tyrosine kinase in rat hepatoma cells. In Chinese hamster ovary (CHO) cells transfected with cDNA of the human insulin receptor, tyrosine-phosphorylation of pp185 was strongly enhanced by ConA compared with the controls, suggesting that the induction of tyrosine-phosphorylation of pp185 was due to stimulation of the insulin receptor kinase by ConA. Moreover, monovalent ConA only slightly induced the tyrosine-phosphorylation of pp185, which was enhanced by the addition of anti-ConA IgG, suggesting that ConA stimulated the insulin receptor kinase mainly by the receptor cross-linking or aggregation in intact cells. These data suggest that the insulin-mimetic action of ConA is related to the autophosphorylation and activation of the insulin receptor tyrosine kinase, as well as the subsequent phosphorylation of pp185 in intact cells.
Concanavalin A-induced receptor aggregation stimulates the tyrosine kinase activity of the insulin receptor in intact cells
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T Shiba, K Tobe, O Koshio, R Yamamoto, Y Shibasaki, N Matsumoto, S Toyoshima, T Osawa, Y Akanuma, F Takaku, M Kasuga; Concanavalin A-induced receptor aggregation stimulates the tyrosine kinase activity of the insulin receptor in intact cells. Biochem J 1 May 1990; 267 (3): 787–794. doi: https://doi.org/10.1042/bj2670787
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