title: Hypoxia regulates the cAMP- and Ca2+/calmodulin signaling systems in PC12 cells.
abstract: Hypoxic/ischemic trauma is a primary factor in the pathology of various disease states. Yet, very little is known about the molecular mechanisms involved in cellular responses and adaptations to hypoxia. As a means of identifying intracellular signaling systems that are regulated in response to hypoxia, the effects of acute and chronic hypoxia on the activity of protein kinase A (PKA) and Ca2+/CaM-dependent protein kinase II (CaMK-II) were evaluated in rat pheochromocytoma (PC12) cells. Chronic (> 6 hr), but not acute exposure to hypoxia (5% O2) significantly decreased both PKA enzyme activity and immunoreactivity compared to control levels. This effect was not due to hypoxia-induced alterations in cell number or viability. Similarly, chronic hypoxia significantly decreased CaMK-II enzyme activity and protein levels in PC12 cells. These data demonstrate that down-regulation of the cAMP and Ca2+/CaM-signaling systems is a mechanism by which PC12 cells adapt to long-term hypoxia.
authors.affiliation: Department of Cellular and Molecular Physiology, College of Medicine, University of Cincinnati, Ohio 45267-0576, USA.
authors.forename: D
authors.initials: D
authors.lastname: Beitner-Johnson
authors.forename: J
authors.initials: J
authors.lastname: Leibold
authors.forename: D E
authors.initials: DE
authors.lastname: Millhorn
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism*; D002452:Cell Count; D002470:Cell Survival; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015536:Down-Regulation; D000860:Hypoxia / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D016716:PC12 Cells; D051381:Rats; D015398:Signal Transduction; D013347:Subcellular Fractions / Q000201:enzymology
chemical_list: D002147:Calmodulin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium