title: A modulatory role for protein phosphatase 2B (calcineurin) in the regulation of Ca2+ entry.
abstract: The Ca2+/calmodulin-dependent protein phosphatase 2B (PP2B) also known as calcineurin (CN) has been implicated in the Ca2+-dependent inactivation of Ca2+ channels in several cell types. To study the role of calcineurin in the regulation of Ca2+-channel activity, phosphatase expression was altered in NG108-15 cells by transfection of sense and antisense plasmid constructs carrying the catalytic subunit of human PP2Bbeta3. Relative to mock-transfected (wild-type) controls, cells overexpressing calcineurin showed dramatically reduced high-voltage-activated Ca2+ currents which were recoverable by the inclusion of 1 microM FK506 in the patch pipette. Conversely, in cells with reduced calcineurin expression, high-voltage-activated Ca2+ currents were larger relative to controls. Additionally in these cells, low-voltage-activated currents were significantly reduced. Analysis of high-voltage-activated Ca2+ currents revealed that the kinetics of inactivation were significantly accelerated in cells overexpressing calcineurin. Following the delivery of a train of depolarizing pulses in experiments designed to produce large-scale Ca2+ influx across the cell membrane, Ca2+-dependent inactivation of high-voltage-activated Ca2+ currents was increased in sense cells, and this increase could be reduced by intracellular application of 1 mM BAPTA or 1 microM FK506. These data support a role of calcineurin in the negative feedback regulation of Ca2+ entry through voltage-operated Ca2+ channels.
authors.affiliation: Department of Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
authors.forename: J R
authors.initials: JR
authors.lastname: Burley
authors.forename: T S
authors.initials: TS
authors.lastname: Sihra
mesh_terms: D000818:Animals; D016375:Antisense Elements (Genetics); D019703:Calcineurin / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D015870:Gene Expression / Q000502:physiology; D005910:Glioma; D006801:Humans; D015151:Immunoblotting; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009447:Neuroblastoma; D009474:Neurons / Q000737:chemistry / Q000201:enzymology*; D018408:Patch-Clamp Techniques; D016559:Tacrolimus / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D016375:Antisense Elements (Genetics); D015220:Calcium Channels; D002614:Chelating Agents; D007166:Immunosuppressive Agents; D004533:Egtazic Acid; D019703:Calcineurin; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium; D016559:Tacrolimus