title: Calcineurin enhances L-type Ca(2+) channel activity in hippocampal neurons: increased effect with age in culture.
abstract: The Ca(2+)/calmodulin-dependent protein phosphatase, calcineurin, modulates a number of key Ca(2+) signaling pathways in neurons, and has been implicated in Ca(2+)-dependent negative feedback inactivation of N-methyl-D-aspartate receptors and voltage-sensitive Ca(2+) channels. In contrast, we report here that three mechanistically disparate calcineurin inhibitors, FK-506, cyclosporin A, and the calcineurin autoinhibitory peptide, inhibited high-voltage-activated Ca(2+) channel currents by up to 40% in cultured hippocampal neurons, suggesting that calcineurin acts to enhance Ca(2+) currents. This effect occurred with Ba(2+) or Ca(2+) as charge carrier, and with or without intracellular Ca(2+) buffered by EGTA. Ca(2+)-dependent inactivation of Ca(2+) channels was not affected by FK-506. The immunosuppressant, rapamycin, and the protein phosphatase 1/2A inhibitor, okadaic acid, did not decrease Ca(2+) channel current, showing specificity for effects on calcineurin. Blockade of L-type Ca(2+) channels with nimodipine fully negated the effect of FK-506 on Ca(2+) channel current, while blockade of N-, and P-/Q-type Ca(2+) channels enhanced FK-506-mediated inhibition of the remaining L-type-enriched current. FK-506 also inhibited substantially more Ca(2+) channel current in 4-week-old vs. 2-week-old cultures, an effect paralleled by an increase in calcineurin A mRNA levels. These studies provide the first evidence that calcineurin selectively enhances L-type Ca(2+) channel activity in neurons. Moreover, this action appears to be increased concomitantly with the well-characterized increase in L-type Ca(2+) channel availability in hippocampal neurons with age-in-culture.
authors.affiliation: Department of Molecular and Biomedical Pharmacology, College of Medicine, MS-310 UKMC, University of Kentucky, Lexington, KY 40536-0298, USA. cnorr2@pop.uky.edu
authors.forename: C M
authors.initials: CM
authors.lastname: Norris
authors.forename: E M
authors.initials: EM
authors.lastname: Blalock
authors.forename: K-C
authors.initials: KC
authors.lastname: Chen
authors.forename: N M
authors.initials: NM
authors.lastname: Porter
authors.forename: P W
authors.initials: PW
authors.lastname: Landfield
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D051017:Apoptosis Regulatory Proteins; D019703:Calcineurin / Q000235:genetics / Q000378:metabolism*; D065095:Calcineurin Inhibitors; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002352:Carrier Proteins / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D016572:Cyclosporine / Q000494:pharmacology; D005260:Female; D005333:Fetus; D006624:Hippocampus / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011247:Pregnancy; D054645:Protein Phosphatase 1; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D016559:Tacrolimus / Q000494:pharmacology; D022061:Tacrolimus Binding Protein 1A / Q000494:pharmacology
chemical_list: D051017:Apoptosis Regulatory Proteins; C113573:Cabin1 protein, rat; D065095:Calcineurin Inhibitors; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D002352:Carrier Proteins; D002614:Chelating Agents; D007166:Immunosuppressive Agents; D012333:RNA, Messenger; D016572:Cyclosporine; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D022061:Tacrolimus Binding Protein 1A; D016559:Tacrolimus