title: Slowed N-type calcium channel (CaV2.2) deactivation by the cyclin-dependent kinase inhibitor roscovitine.
abstract: The lack of a calcium channel agonist (e.g., BayK8644) for CaV2 channels has impeded their investigation. Roscovitine, a potent inhibitor of cyclin-dependent kinases 1, 2, and 5, has recently been reported to slow the deactivation of P/Q-type calcium channels (CaV2.1). We show that roscovitine also slows deactivation (EC(50) approximately 53 microM) of N-type calcium channels (CaV2.2) and investigate gating alterations induced by roscovitine. The onset of slowed deactivation was rapid ( approximately 2 s), which contrasts with a slower effect of roscovitine to inhibit N-current (EC(50) approximately 300 microM). Slow deactivation was specific to roscovitine, since it could not be induced by a closely related cyclin-dependent kinase inhibitor, olomoucine (300 microM). Intracellularly applied roscovitine failed to slow deactivation, which implies an extracellular binding site. The roscovitine-induced slow deactivation was accompanied by a slight left shift in the activation-voltage relationship, slower activation at negative potentials, and increased inactivation. Additional data showed that roscovitine preferentially binds to the open channel to slow deactivation. A model where roscovitine reduced a backward rate constant between two open states was able to reproduce the effect of roscovitine on both activation and deactivation.
authors.affiliation: Department of Physiology, Tulane University Health Sciences Center, New Orleans, Louisiana, USA.
authors.forename: Zafir
authors.initials: Z
authors.lastname: Buraei
authors.forename: Mircea
authors.initials: M
authors.lastname: Anghelescu
authors.forename: Keith S
authors.initials: KS
authors.lastname: Elmslie
mesh_terms: D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D020864:Calcium Channels, N-Type / Q000502:physiology*; D020865:Calcium Channels, P-Type / Q000187:drug effects / Q000502:physiology*; D020907:Calcium Channels, Q-Type / Q000187:drug effects / Q000502:physiology*; D003198:Computer Simulation; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005728:Ganglia, Sympathetic / Q000378:metabolism; D015640:Ion Channel Gating; D007700:Kinetics; D007701:Kinetin / Q000737:chemistry / Q000494:pharmacology; D008390:Markov Chains; D008564:Membrane Potentials; D008956:Models, Chemical; D009474:Neurons / Q000378:metabolism; D018377:Neurotransmitter Agents; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D011687:Purines / Q000737:chemistry / Q000494:pharmacology*; D011892:Rana catesbeiana; D000077546:Roscovitine
chemical_list: C500963:Cacna1b protein, mouse; D020864:Calcium Channels, N-Type; D020865:Calcium Channels, P-Type; D020907:Calcium Channels, Q-Type; D004791:Enzyme Inhibitors; D018377:Neurotransmitter Agents; D047428:Protein Kinase Inhibitors; D011687:Purines; D000077546:Roscovitine; C090046:olomoucine; D018844:Cyclin-Dependent Kinases; D007701:Kinetin; D002118:Calcium