Tyrosine kinase activity of brain insulin and IGF-1 receptors.
Lectin-purified rat brain preparations demonstrate specific [125I]insulin and [125I]-IGF-1 binding. Insulin-stimulable tyrosine kinase activity as measured by exogenous substrate phosphorylation was present in brain and liver lectin purified preparations with the delta kinase activity/B/F of brain approximately 2.5 fold greater than that of liver. Insulin-stimulable tyrosine kinase activity was abolished in liver but decreased by only approximately 50 percent in brain after immuno-depletion with antiserum which recognizes insulin but not IGF-1 receptors. Insulin and IGF-1 dose responses for phosphorylation of the immunodepleted brain preparations suggested that the remaining tyrosine kinase activity was IGF-1 receptor mediated. Thus, functional IGF-1 receptors are present in rat brain, and the doses of insulin typically used to evaluate insulin receptor tyrosine kinase activity will stimulate IGF-1 receptor tyrosine kinase activity as well.
D000818:Animals; D001921:Brain / Q000201:enzymology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D037102:Lectins; D008099:Liver / Q000201:enzymology; D008297:Male; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D011972:Receptor, Insulin / Q000302:isolation & purification / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000378:metabolism*
D037102:Lectins; D010750:Phosphoproteins; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin