title: "Slow" Voltage-Dependent Inactivation of CaV2.2 Calcium Channels Is Modulated by the PKC Activator Phorbol 12-Myristate 13-Acetate (PMA).
abstract: CaV2.2 (N-type) voltage-gated calcium channels (Ca2+ channels) play key roles in neurons and neuroendocrine cells including the control of cellular excitability, neurotransmitter / hormone secretion, and gene expression. Calcium entry is precisely controlled by channel gating properties including multiple forms of inactivation. "Fast" voltage-dependent inactivation is relatively well-characterized and occurs over the tens-to- hundreds of milliseconds timeframe. Superimposed on this is the molecularly distinct, but poorly understood process of "slow" voltage-dependent inactivation, which develops / recovers over seconds-to-minutes. Protein kinases can modulate "slow" inactivation of sodium channels, but little is known about if/how second messengers control "slow" inactivation of Ca2+ channels. We investigated this using recombinant CaV2.2 channels expressed in HEK293 cells and native CaV2 channels endogenously expressed in adrenal chromaffin cells. The PKC activator phorbol 12-myristate 13-acetate (PMA) dramatically prolonged recovery from "slow" inactivation, but an inactive control (4α-PMA) had no effect. This effect of PMA was prevented by calphostin C, which targets the C1-domain on PKC, but only partially reduced by inhibitors that target the catalytic domain of PKC. The subtype of the channel β-subunit altered the kinetics of inactivation but not the magnitude of slowing produced by PMA. Intracellular GDP-β-S reduced the effect of PMA suggesting a role for G proteins in modulating "slow" inactivation. We postulate that the kinetics of recovery from "slow" inactivation could provide a molecular memory of recent cellular activity and help control CaV2 channel availability, electrical excitability, and neurotransmission in the seconds-to-minutes timeframe.
authors.affiliation: Department of Anesthesiology, Vanderbilt University, Nashville, Tennessee, United States of America.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhu
authors.affiliation: Department of Anesthesiology, Vanderbilt University, Nashville, Tennessee, United States of America.
authors.forename: Sarah
authors.initials: S
authors.lastname: McDavid
authors.affiliation: Department of Anesthesiology, Vanderbilt University, Nashville, Tennessee, United States of America; Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, United States of America; Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee, United States of America.
authors.forename: Kevin P M
authors.initials: KP
authors.lastname: Currie
mesh_terms: D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020864:Calcium Channels, N-Type / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007700:Kinetics; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D013873:Thionucleotides / Q000378:metabolism
chemical_list: C500545:CACNA1B protein, human; D002121:Calcium Channel Blockers; D020864:Calcium Channels, N-Type; D011994:Recombinant Proteins; D013873:Thionucleotides; D006153:Guanosine Diphosphate; C023427:guanosine 5'-O-(2-thiodiphosphate); D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate