Activity of Protein Kinase Dependent on Adenosine 3′:5′‐Monophosphate and of Its Thermostable Protein Inhibitor in Rat Hepatoma (HTC) Cells

Publisher Website
Google Scholar
Abstract
Normal expression of a variety of hormonal effects which depend on cyclic[c]AMP requires the presence of glucocorticoids. Glucocorticoids probably directly or indirectly control the activity of cAMP-dependent protein kinase. This was investigated in cultured hepatoma (HTC) cells in which N6,O2''-dibutyrylcAMP increases the activity of tyrosine transaminase only after glucocorticoid treatment. In these cells, the following parameters were determined: the concentration and half-life of protein kinase; the sensitivity of this enzyme in vitro to cAMP and to its thermostable protein inhibitor; the state of dissociation of protein kinase holoenzyme in vivo and its sensitivity, in the intact cell, to dibutyrylcAMP and to the inhibitor diamide; and the concentration of endogenous thermostable protein inhibitor of protein kinase. None of these parameters were influenced by glucocorticoids under conditions where these hormones stimulate the activity of tyrosine transaminase and restore sensitivity to dibutyrylcAMP. The permissive action of glucocorticoids probably results from a control of cAMP-dependent processes exerted at a level beyond the protein kinase system.

This publication has 54 references indexed in Scilit: