Parietal cell protein kinases. Selective activation of type I cAMP-dependent protein kinase by histamine.
cAMP-dependent protein kinases have been characterized in parietal cells isolated from rabbit gastric mucosa. Both Type I and Type II cAMP-dependent protein kinase isozymes are present in these cells. Type II isozymes were detected in 900, 14,000, and 100,000 X g particulate fractions as well as 100,000 X g cytosolic fractions; Type I isozymes were found predominately in the cytosolic fraction. When parietal cells were stimulated with histamine, an agent that elevates intracellular cAMP content and initiates parietal cell HCl secretion, cAMP-dependent protein kinase activity was increased in homogenates of these cells as measured by an increase in the cAMP-dependent protein kinase activity ratio. Histamine activation of cAMP-dependent protein kinase was correlated with parietal cell acid secretory responses which were measured indirectly as increased cellular uptake of the weak base, [14C]aminopyrine. These results suggest that cAMP-dependent protein kinase(s) is involved in the control of parietal cell HCl secretion. The parietal cell response to histamine may be compartmentalized because histamine appears to activate only a cytosolic Type I cAMP-dependent protein kinase isozyme, as determined by three different techniques including 1) ion exchange chromatography; 2) Sephadex G-25 to remove cAMP and allow rapid reassociation of the Type II but not the Type I isozyme; and 3) 8-azido-[32P]cAMP photoaffinity labeling. Forskolin, an agent that directly stimulates adenylate cyclases, was found to activate both the Type I and Type II isozymes. Several cAMP-dependent protein kinases were also detected in parietal cell homogenates, including a Ca2+-phospholipid-sensitive or C kinase and two casein kinases which were tentatively identified as casein kinase I and II. At least two additional protein kinases with a preference for serine or lysine-rich histones, respectively, were also detected. The function of these enzymes in parietal cells remains to be shown.
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D000067956:Adenylyl Cyclase Inhibitors; D000818:Animals; D001386:Azides / Q000494:pharmacology; D005576:Colforsin; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004224:Diterpenes / Q000494:pharmacology; D004789:Enzyme Activation; D006632:Histamine / Q000494:pharmacology*; D007700:Kinetics; D008970:Molecular Weight; D010295:Parietal Cells, Gastric / Q000201:enzymology*; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D011817:Rabbits; D013347:Subcellular Fractions / Q000201:enzymology
D000067956:Adenylyl Cyclase Inhibitors; D001386:Azides; D004224:Diterpenes; D005576:Colforsin; C017042:8-azidoadenosine-3',5'-monophosphate; D006632:Histamine; D000242:Cyclic AMP; D011494:Protein Kinases