Regulation of hormone(PTH and PGE1)-stimulated adenylate cyclase by renal cytosolic factors.

Cytosolic factors in a 50--75% (NH4)2SO4 fraction of the 105 000 x g supernatant of the renal cortex modulated adenylate cyclase activity in membrane preparations enriched in renal tubular cell basal--lateral membranes. The crude factor preparation had no effect on basal activity but it contained components that augmented the stimulated of the enzyme by NaF, parathyroid hormone (PTH), prostaglandin E1 (PGE1), and inhibited the activation of the enzyme by GMP--PNP. The factor(s) potentiating the stimulation by the hormones was partially purified (13-fold) by DEAE-cellulose and Sephadex G-75 chromatography. During purification, the component(s) that increased hormone-stimulated adenylate cyclase was separated from those affecting the activity in the presence of NaF and GMP--PNP. The factor(s) enhanced the PTH- and PGE1-stimulated enzyme at all concentrations of hormone, suggesting that the affinity for the hormone was not affected. The factor(s) was heat-stable. Partial proteolysis with chymotrypsin greatly reduced the ability of the factor(s) to enhance hormonal responsive adenylate cyclase. However, the factor(s) was resistant to trypsin digestion. The effect of the factor was not due to GTP, nor was GTP necessary for its action. Ca2+ was not needed for the enhancing activity of the factor(s). These findings suggest the presence in the cytosol of the kidney cortex of a protein(s) that regulates the response of renal adenylate cyclase to hormones. The relationship between this kidney cytosolic factor and those reported in other tissues remains to be established.