The role of phosphoproteins and newly synthesized proteins in the hormonal regulation of steroidogenesis in Leydig cells.

LH activation of steroidogenesis in Leydig cells is accompanied by increased phosphorylation of at least 5 phosphoproteins. The 17000 Da protein is localized in nuclei and appears not to be involved in the acute stimulation of steroidogenesis. The 57,000 Da protein is the regulatory subunit of the cAMP-dependent protein kinase. The 22,000, 24,000 and 33,000 phosphoproteins are present in microsomes and may regulate the synthesis of specific rapidly-turning-over protein(s) which in turn may stimulate the mitochondrial cholesterol side-chain cleavage activity.