Brain protein phosphorylation in vitro: selective substrate action of insulin.
Insulin action on [32P]-phosphate incorporation into brain membranes was determined. Hippocampal homogenate tissue was phosphorylated with [32P]-ATP, and insulin was introduced at various times before or after ATP addition. With 50 microM Mg++ in the medium, insulin selectively stimulated the phosphorylation of a 47kD phosphoprotein, Protein F1. This effect required the prior presence of ATP. No effect of insulin on other phosphoproteins, or on [32P]-phosphate incorporation into TCA-precipitated material, was observed under these conditions. At 1 mM Mg++, insulin selectively decreased the phosphorylation of the alpha-subunit of pyruvate dehydrogenase. Insulin had no effect on other phosphoproteins, or on [32P]-phosphate incorporation into TCA-precipitated material under these conditions. The present study suggests a role for insulin in the modulation of brain protein phosphorylation. Since Protein F1 is phosphorylated by exogenous C kinase, and is likely the CNS-specific B-50 protein, these data also indicate a brain-specific function for insulin, possibly by action on a Ca++/phospholipid protein kinase.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D007328:Insulin / Q000502:physiology*; D008274:Magnesium / Q000378:metabolism; D008297:Male; D010710:Phosphates / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism
D007328:Insulin; D010710:Phosphates; D010750:Phosphoproteins; D011972:Receptor, Insulin; D008274:Magnesium