The separation of antagonist from agonist effects of trisubstituted purines on CaV2.2 (N-type) channels

Authors

  • Zafir Buraei,

    1. Department of Physiology, Tulane University Health Sciences Center, New Orleans, Louisiana, USA
    2. Rockefeller University, Cardiac/Membrane Biology Lab, New York, New York, USA
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    • 1

      The present address of Zafir Buraei is the Department of Biological Sciences, Columbia University, New York, NY 10027.

  • Keith S. Elmslie

    1. Department of Physiology, Tulane University Health Sciences Center, New Orleans, Louisiana, USA
    2. Departments of Anesthesiology and Pharmacology, Penn State College of Medicine, Milton S. Hershey Medical Center, Hershey, Pennsylvania, USA
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Address correspondence and reprint requests to Keith S. Elmslie, Ph.D., Department of Anesthesiology, Penn State College of Medicine, Milton S. Hershey Medical Center, 500 University Drive, Hershey, PA 17033. E-mail: kse10@psu.edu

Abstract

Dihydropyridines can affect L-type calcium channels (CaV1) as either agonists or antagonists. Seliciclib or R-roscovitine, a 2,6,9-trisubstituted purine, is a potent cyclin-dependent kinase inhibitor that induces both agonist and antagonist effects on CaV2 channels (N-, P/Q- and R-type). We studied the effects induced by various trisubstituted purines on CaV2.2 (N-type) channels to learn about chemical structure–function relationships. We found that S-roscovitine and R-roscovitine showed similar potency to inhibit, but agonist activity of S-roscovitine required at least a 20-fold higher concentration, suggesting stereospecificity of the agonist-binding site. The testing of other trisubstituted purines showed a correlation between CaV2.2 inhibition and cyclin-dependent kinase affinity that broke down after determining that a chemically unrelated inhibitor, kenpaullone, was a poor CaV2.2 inhibitor, and a kinase inactive analog (dimethylamino-olomoucine; DMAO) was a strong inhibitor, which together support a kinase independent effect. In fact, like dihydropyridine-induced L-channel inhibition, R-roscovitine left-shifted the closed-state inactivation versus voltage relationship, which suggests that inhibition results from CaV2 channels moving into the inactivated state. Trisubstituted purine antagonists could become clinically important drugs to treat diseases, such as heart failure and neuropathic pain that result from elevated CaV2 channel activity.

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