Hormonal regulation of protein synthesis, secretion, and phosphorylation in cultured rat Sertoli cells

The accumulation of two polypeptides, SCm1 and SCm2, in the medium of Sertoli cell cultures is enhanced by follicle-stimulating hormone (FSH) but is unaffected by either the cAMP analog, N6,O2'-dibutyrl cAMP or luteinizing hormone. The assigned molecular weights of SCm1 and SCm2 differ from those of androgen-binding protein subunits or any other previously identified Sertoli cell secretory product. Incubation of Sertoli cell cultures with either FSH or N6,O2'-dibutyryl cAMP also stimulates the incorporation of [35S]methionine into two intracellular polypeptides, SCc1 and SCc2. In addition, the phosphorylation of three intracellular polypeptides, SCc3, SCc4, and SCc5, is intensified when Sertoli cell cultures are treated with either FSH or N6,O2'-dibutyryl cAMP. Based on these results and on previous work, we conclude that (i) SCm1 and SCm2 may, like androgen-binding protein, be secreted by Sertoli cells and function extracellularly while SCc1 and SCc2 are involved in FSH-dependent intracellular activity; (ii) SCc3, SCc4, and SCc5 are possible substrates for FSH-stimulated, cAMP-dependent protein kinase activity; and (iii) SCc5 is an isoelectric variant of vimentin-type intermediate filament protein presumably involved in FSH- and N6,O2'-dibutyryl cAMP-induced Sertoli cell shape changes.