Regulation of hormone-sensitive calcium influx by the adenylyl cyclase system in renal epithelial cells.
To study signaling pathways regulated by alpha s and alpha i1 in renal epithelial cells, we expressed mutant, activated forms of alpha s and alpha i1 in a continuous proximal tubule cell line (MCT cells). alpha sQ227L increased cAMP production, and alpha ilQ204L reduced forskolin-sensitive cAMP production. alpha ilQ204L increased and alpha sQ227L decreased bradykinin-induced Ca influx across the cell membrane, but neither mutant affected bradykinin-stimulated intracellular Ca release or basal Ca influx. Bradykinin-stimulated Ca influx was reduced by dibutyryl cAMP, isoproterenol, and forskolin. Expression of a mutant regulatory type I subunit for cAMP-dependent protein kinase with reduced affinity for cAMP and treatment with KT-5720, a specific cAMP-dependent protein kinase inhibitor, enhanced Ca influx to a degree similar to that in cells expressing alpha ilQ204L. Bradykinin-stimulated c-fos mRNA expression is partially dependent on extracellular Ca. alpha sQ227L reduced and alpha ilQ204L enhanced bradykinin-stimulated c-fos expression. Consequently, in bradykinin-stimulated cells, the adenylyl cyclase system regulates Ca influx through cAMP-dependent protein kinase, but not intracellular Ca release. Furthermore, the Ca influx mechanism acts as an integrator of two signaling pathways such that Ca-dependent signals are damped by activators of adenylyl cyclase and enhanced by inhibitors of adenylyl cyclase.
Nephrology Division, University of Texas Southwestern Medical Center, Dallas 75235-8856.
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Kitamura
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Miller
D000262:Adenylyl Cyclases / Q000502:physiology*; D000818:Animals; D001483:Base Sequence; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D004848:Epithelium / Q000378:metabolism; D016762:Genes, fos; D006160:Guanosine Triphosphate / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data
D006160:Guanosine Triphosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases; D001920:Bradykinin; D002118:Calcium