In cholera toxin-treated gastric chief cells, incubation with a cholinergic agonist (carbamylcholine), a regulatory peptide (cholecystokinin), or a calcium ionophore (A23187) causes a dose- and time-dependent potentiation of cAMP levels. Because this augmented response is calcium/calmodulin-dependent, we hypothesized that it was mediated by calcineurin (protein phosphatase 2B). To test this hypothesis, we examined the actions of calcineurin inhibitors on secretagogue-induced potentiation of cAMP levels in guinea pig chief cells. Preincubation of cells with 0.1 microM FK-506 completely prevented carbachol-induced augmentation of cAMP levels and pepsinogen secretion from cholera toxin-treated cells. Cyclosporin-A, another calcineurin inhibitor, also prevented the augmented cAMP response. FK-506 and cyclosporin inhibited augmentation of cAMP levels following treatment with cholecystokinin(26-33) and A23187, but not the smaller increase in cAMP following treatment with a phorbol ester that activates protein kinase C. Hence, the actions of calcineurin inhibitors were limited to secretagogues that increase cellular calcium. Rapamycin, an agent that competes with FK-506 for the immunophilin, FK binding protein 12, does not inhibit calcineurin. In the present study, preincubation with rapamycin did not prevent carbachol-induced augmentation of cAMP levels in cholera toxin-treated chief cells. However, a molar excess of rapamycin reversed the inhibitory actions of FK-506. These experiments provide further evidence that the actions of FK-506 on cholera toxin-treated gastric chief cells are caused by its inhibitory actions on calcineurin. FK-506 also inhibited potentiation of cAMP levels when carbachol was added to cells that were preincubated with forskolin, an agent that directly activates adenylyl cyclase. We conclude that, in gastric chief cells, calcineurin mediates cross-talk between the calcium/calmodulin and adenylyl cyclase signaling pathways.
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http://dx.doi.org/10.1074/jbc.271.33.19877 | DOI Listing |
J Virol Methods
January 2025
Department of Pharmacology, Physiology, and Biophysics, Boston University Chobanian and Avedisian School of Medicine, Boston, MA, USA; National Emerging Infectious Diseases Laboratories, Boston University Chobanian and Avedisian School of Medicine, Boston, MA, USA; Department of Virology, Immunology & Microbiology, Boston University Chobanian and Avedisian School of Medicine, Boston, MA, USA.
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View Article and Find Full Text PDFProc Natl Acad Sci U S A
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Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 1L7, Canada.
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Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, AB, T6G 2E1, Canada.
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Department of Radiology and Imaging Sciences, Center for Neuroimaging, Indiana University School of Medicine, Indianapolis, IN, USA.
Alzheimer's disease (AD) is a debilitating neurodegenerative disease that is marked by profound neurovascular dysfunction and significant cell-specific alterations in the brain vasculature. Recent advances in high throughput single-cell transcriptomics technology have enabled the study of the human brain vasculature at an unprecedented depth. Additionally, the understudied niche of cerebrovascular cells, such as endothelial and mural cells, and their subtypes have been scrutinized for understanding cellular and transcriptional heterogeneity in AD.
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Center for Autoimmune Musculoskeletal and Hematopoietic Diseases, Institute of Molecular Medicine, The Feinstein Institutes for Medical Research, Northwell Health, 350 Community Drive, Manhasset, New York, 11030, USA.
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