We have demonstrated previously that glucose activates the multifunctional Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) in isolated rat pancreatic islets in a manner consistent with a role of this enzyme in the regulation of insulin secretion [Wenham, Landt and Easom (1994) J. Biol. Chem. 269, 4947–4952]. In the current study, the muscarinic agonist, carbachol, has been shown to induce the conversion of CaM kinase II into a Ca2+-independent, autonomous form indicative of its activation. Maximal activation (2-fold) was achieved by 15 s, followed by a rapid return to basal levels by 1 min. This response was primarily the result of the mobilization of Ca2+ from intracellular stores since it was not affected by a concentration (20 μM) of verapamil that completely prevented the activation of CaM kinase II by glucose. Surprisingly, carbachol added prior to, or simultaneously with, glucose attenuated nutrient activation of CaM kinase II. This effect was mimicked by cholecystokinin-8 (CCK-8) and thapsigargin, suggesting its mediation by phospholipase C and the mobilization of intracellular Ca2+. In contrast, carbachol, CCK-8 and thapsigargin markedly potentiated glucose (12 mM)-induced insulin secretion. These results suggest that CaM kinase II activation can be temporally dissociated from insulin secretion but do not exclude the potential dependence of insulin exocytosis on CaM kinase II-mediated protein phosphorylation.
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Research Article|
July 01 1996
Muscarinic activation of Ca2+/calmodulin-dependent protein kinase II in pancreatic islets. Temporal dissociation of kinase activation and insulin secretion
Eric L. BABB;
Eric L. BABB
*Department of Biochemistry and Molecular Biology, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107-2699
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Jim TARPLEY;
Jim TARPLEY
*Department of Biochemistry and Molecular Biology, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107-2699
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Michael LANDT;
Michael LANDT
†Department of Pediatrics, Washington University School of Medicine, St. Louis, MO 63110, U.S.A.
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Richard A. EASOM
Richard A. EASOM
‡
*Department of Biochemistry and Molecular Biology, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107-2699
‡To whom correspondence should be addressed.
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Publisher: Portland Press Ltd
Received:
January 15 1996
Revision Received:
March 05 1996
Accepted:
March 08 1996
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1996
1996
Biochem J (1996) 317 (1): 167–172.
Article history
Received:
January 15 1996
Revision Received:
March 05 1996
Accepted:
March 08 1996
Citation
Eric L. BABB, Jim TARPLEY, Michael LANDT, Richard A. EASOM; Muscarinic activation of Ca2+/calmodulin-dependent protein kinase II in pancreatic islets. Temporal dissociation of kinase activation and insulin secretion. Biochem J 1 July 1996; 317 (1): 167–172. doi: https://doi.org/10.1042/bj3170167
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