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Expression and subunit interaction of voltage-dependent Ca2+ channels in PC12 cells.

ABSTRACT: Nerve growth factor (NGF)-induced differentiation in PC12 cells is accompanied by changes in the expression of voltage-dependent Ca2+ channels. Ca2+ channels are multimeric complexes composed of at least three subunits (alpha1, beta, and alpha2delta) and are involved in neuronal migration, gene expression, and neurotransmitter release. Although attempts have been undertaken to elucidate NGF regulation of Ca2+ channel expression, the changes in subunit composition of these channels during differentiation still remain uncertain. In the present study, patch-clamp recordings show that in addition to the previously documented L-type and N-type Ca2+ currents, undifferentiated PC12 cells also express an omega-agatoxin-IVA-sensitive (P/Q-type) component. In addition, the corresponding mRNA encoding the pore-forming alpha1 subunits for these channels (C, B, and A, respectively) was detected. Likewise, mRNA for three distinct auxiliary beta subunits (1, 2, 3) were also found, beta3 protein being dominantly expressed. Immunoprecipitation experiments show that the N-type Ca2+ channel is associated with either a beta2 or beta3 subunit and that NGF increases the channel expression without affecting its beta subunit association. These results (1) indicate that the diversity of Ca2+ currents in PC12 cells arise from the expression of three distinct alpha1 and three different beta subunit genes; (2) support a model for heterogenous beta subunit association of the N-type Ca2+ channel in a single cell type; and (3) suggest that the regulation of the N-type Ca2+ channel during NGF-mediated differentiation involves an increase in the number of functional channels with no apparent changes in subunit composition.

SUBMITTER: Liu H

PROVIDER: S-EPMC6579093 | biostudies-literature | 1996 Dec

REPOSITORIES: biostudies-literature

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Expression and subunit interaction of voltage-dependent Ca2+ channels in PC12 cells.

Liu H H Felix R R Gurnett C A CA De Waard M M Witcher D R DR Campbell K P KP

The Journal of neuroscience : the official journal of the Society for Neuroscience 19961201 23

Nerve growth factor (NGF)-induced differentiation in PC12 cells is accompanied by changes in the expression of voltage-dependent Ca2+ channels. Ca2+ channels are multimeric complexes composed of at least three subunits (alpha1, beta, and alpha2delta) and are involved in neuronal migration, gene expression, and neurotransmitter release. Although attempts have been undertaken to elucidate NGF regulation of Ca2+ channel expression, the changes in subunit composition of these channels during differe ...[more]

PMID: 8922412

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Project description:Voltage-dependent Na+ channel activation underlies action potential generation fundamental to cellular excitability. In skeletal and cardiac muscle this triggers contraction via ryanodine-receptor (RyR)-mediated sarcoplasmic reticular (SR) Ca2+ release. We here review potential feedback actions of intracellular [Ca2+] ([Ca2+]i) on Na+ channel activity, surveying their structural, genetic and cellular and functional implications, translating these to their possible clinical importance. In addition to phosphorylation sites, both Nav1.4 and Nav1.5 possess potentially regulatory binding sites for Ca2+ and/or the Ca2+-sensor calmodulin in their inactivating III-IV linker and C-terminal domains (CTD), where mutations are associated with a range of skeletal and cardiac muscle diseases. We summarize in vitro cell-attached patch clamp studies reporting correspondingly diverse, direct and indirect, Ca2+ effects upon maximal Nav1.4 and Nav1.5 currents (Imax) and their half-maximal voltages (V1/2) characterizing channel gating, in cellular expression systems and isolated myocytes. Interventions increasing cytoplasmic [Ca2+]i down-regulated Imax leaving V1/2 constant in native loose patch clamped, wild-type murine skeletal and cardiac myocytes. They correspondingly reduced action potential upstroke rates and conduction velocities, causing pro-arrhythmic effects in intact perfused hearts. Genetically modified murine RyR2-P2328S hearts modelling catecholaminergic polymorphic ventricular tachycardia (CPVT), recapitulated clinical ventricular and atrial pro-arrhythmic phenotypes following catecholaminergic challenge. These accompanied reductions in action potential conduction velocities. The latter were reversed by flecainide at RyR-blocking concentrations specifically in RyR2-P2328S as opposed to wild-type hearts, suggesting a basis for its recent therapeutic application in CPVT. We finally explore the relevance of these mechanisms in further genetic paradigms for commoner metabolic and structural cardiac disease.

Dataset Information

Expression and subunit interaction of voltage-dependent Ca2+ channels in PC12 cells.

Publications

Expression and subunit interaction of voltage-dependent Ca2+ channels in PC12 cells.

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