Partial Purification and Differential Androgen Sensitivity of Protein Phosphokinases from Nuclei of Rat Ventral Prostate

Total protein kinase activity associated with nuclei of rat ventral prostate was extracted and fractionated with the aid of DEAE‐Sephadex column chromatography. The flow‐through peak contained kinase activities towards dephosphophosvitin, lysine‐rich histone, and nonhistone proteins as phosphoprotein substrates. These activities were not stimulated by addition of cAMP, although the cAMP‐dependent protein kinase inhibitor reduced the lysine‐rich histone kinase activity by 70% or more, suggesting that it might represent the catalytic subunit of the cAMP‐dependent histone kinase. By contrast, the inhibitor produced a stimulation of kinase activities toward dephosphophosvitin and nonhistone proteins by 15% and 50%, respectively. The bound fraction on the DEAE Sephadex column was eluted in two peaks of protein kinase activity, one at 0.15–0.20 M (NH 4 ) 2 SO 4 , and the other at 0.25–0.30 M (NH 4 ) 2 SO 4 . The first peak contained activity only toward nonhistone proteins, whereas the second had activity toward dephosphophosvitin, lysine‐rich histone, and nonhistone proteins. None of these was inhibited by the cAMP‐dependent protein kinase inhibitor. The effect of orchiectomy on the activity of the various protein kinase fractions was determined. The kinase activity toward dephosphophosvitin, in the flow‐through peak, was reduced by about 20% and 40% at 24 and 48 h post‐orchiectomy, respectively, and in the bound peak by 33% and 50%, under the same circumstances. Little change was observed in the kinase activity toward lysine‐rich histone in the flow‐through peak or in the bound peak at 24 h post‐orchiectomy. However, at 48 h post‐orchiectomy, it increased by 250% in both fractions. This particular kinase activity toward lysine‐rich histone might be localized to nucleoplasm rather than chromatin. The protein kinase active toward nonhistone proteins present in the flow‐through peak did not change at 24 h post‐orchiectomy, but declined by 50% at 48 h post‐orchiectomy. Of the two bound nonhistone protein kinase activities, that eluting at 0.25–0.30 M (NH 4 ) 2 SO 4 was reduced by over 80% within 24 h post‐orchiectomy, whereas that eluting at 0.15–0.20 M increased by 100% at 24 h and 200% at 48 h post‐orchiectomy. These data demonstrate a differential response of prostatic nuclear‐associated protein kinases to androgen deprivation.