Characterization and Follicle Stimulating Hormone Activation of Sertoli Cell Cyclic AMP-Dependent Protein Kinases

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Abstract
The Sertoli cell of the rat testis contains 2 cytoplasmic forms of cyclic[c]AMP-dependent protein kinase, designated as Peak I and Peak II, which change in relative proportion during Sertoli cell maturation. Peak I and Peak II differ in their subunit interaction. While the substrates, ATP and histone, affect cAMP binding to Peak I, neither of these compounds affect the binding of cAMP to the Peak II enzyme. The effects on cAMP binding to Peak I appear to be due to the fact that histone and high ionic strength cause dissociation of the Peak I holoenzyme, whereas ATP stabilizes the holoenzyme complex against dissociation. The Peak II holoenzyme is not affected by either salt or histone and is only dissociated by cAMP. Once dissociated, the subunits of Peak II will rapidly reassociate under low salt conditions whereas the subunits of Peak I will not reassociate. By utilizing the distinct properties of Peak I and Peak II, it is possible to demonstrate the activation of both Peak I and Peak II Sertoli cell protein kinase in response to FSH [follicle stimulating hormone].