Pattern of Protein Phosphorylation in Intact Stimulated Cells: Thyrotropin and Dog Thyroid

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Abstract
Two-dimensional, high-resolution electrophoretic technique of O''Farrell was adapted to the analysis of thyroid phosphorylated proteins. Proteins were extracted from dog thyroid slices which were incubated in the presence of [32P]phosphate with thyrotropin [TSH] or with different agents which enhance the intracellular accumulation of cyclic[c]AMP. About 350 phosphorylated polypeptides were separated. Thyrotropin stimulated the phosphorylation of at least 8 of these polypeptides. An increase in the phosphorylation of the same polypeptides was observed when dog thyroid slices were incubated with dibutyryl cAMP, cholera toxin or prostaglandin E1 instead of TSH. Most of dog thyroid protein phosphorylation is independent of cAMP. A link may exist between the action of cAMP on protein kinase and the physiological effects of TSH. Most TSH effects apparently mediated by cAMP.