title: Differential regulation of calcium channel coding genes by prolonged depolarization.
abstract: Calcium channels must be subjected to a very precise regulation in order to preserve cell function and viability. Voltage gated calcium channels (VGCC) represent the main pathway for calcium entry in excitable cells. This explains why depolarization induces a rapid-onset and short-term inactivation of calcium currents. Contrarily to this well-documented mechanism to maintain calcium below toxic levels, the regulatory pathways inducing longer-lasting changes and cell surface expression of functional calcium channels are largely unknown. Since calcium is a main player in the activity-dependent regulation of many genes, we hypothesize that calcium channel coding genes could be also subjected to activity-dependent regulation. We have used prolonged depolarization to analyze the effects of sustained intracellular calcium elevation on the mRNAs coding for the different alpha(1) pore-forming subunits of the calcium channels expressed in chromaffin cells. Our findings reveal that persistent depolarization is accompanied by a prolonged intracellular calcium elevation and reduction of calcium current. This calcium current inhibition could be mediated, at least partially, by the downregulation of the mRNAs coding for several alpha(1) subunits. Thus, we show here that depolarization inhibits the expression of Ca(V)1.1, Ca(V)1.2, Ca(V)1.3, Ca(V)2.2 and Ca(V)2.3 mRNAs, while the Ca(V)2.1 mRNA remains unmodified. Moreover, such downregulation of channels depends on calcium entry through the L-type calcium channel, as both mRNA and calcium current changes induced by depolarization are abrogated by L-type channel specific blockers.
authors.affiliation: Faculty of Medicine and Regional Center for Biomedical Research, University of Castilla La Mancha, Albacete, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Benavides
authors.forename: D
authors.initials: D
authors.lastname: Pastor
authors.forename: N
authors.initials: N
authors.lastname: Fradejas
authors.forename: D
authors.initials: D
authors.lastname: Tornero
authors.forename: S
authors.initials: S
authors.lastname: Calvo
mesh_terms: D000818:Animals; D001562:Benzimidazoles; D052160:Benzothiazoles; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000235:genetics*; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000378:metabolism; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D003959:Diamines; D015536:Down-Regulation / Q000187:drug effects; D004594:Electrophysiology; D005456:Fluorescent Dyes; D005786:Gene Expression Regulation / Q000502:physiology*; D007202:Indicators and Reagents; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D009543:Nifedipine / Q000494:pharmacology; D009930:Organic Chemicals; D011804:Quinolines; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D001562:Benzimidazoles; D052160:Benzothiazoles; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D018076:DNA, Complementary; D003959:Diamines; D005456:Fluorescent Dyes; D007202:Indicators and Reagents; D009930:Organic Chemicals; D011804:Quinolines; D012333:RNA, Messenger; C098022:SYBR Green I; D007770:L-Lactate Dehydrogenase; D009543:Nifedipine; C017807:bisbenzimide ethoxide trihydrochloride; D002118:Calcium