title: Conformational changes induced in voltage-gated calcium channel Cav1.2 by BayK 8644 or FPL64176 modify the kinetics of secretion independently of Ca2+ influx.
abstract: The role of the L-type calcium channel (Cav1.2) as a molecular switch that triggers secretion prior to Ca(2+) transport has previously been demonstrated in bovine chromaffin cells and rat pancreatic beta cells. Here, we examined the effect of specific Cav1.2 allosteric modulators, BayK 8644 (BayK) and FPL64176 (FPL), on the kinetics of catecholamine release, as monitored by amperometry in single bovine chromaffin cells. We show that 2 microm BayK or 0.5 microm FPL accelerates the rate of catecholamine secretion to a similar extent in the presence either of the permeable Ca(2+) and Ba(2+) or the impermeable charge carrier La(3+). These results suggest that structural rearrangements generated through the binding of BayK or FPL, by altering the channel activity, could affect depolarization-evoked secretion prior to cation transport. FPL also accelerated the rate of secretion mediated by a Ca(2+)-impermeable channel made by replacing the wild type alpha(1)1.2 subunit was replaced with the mutant alpha(1)1.2/L775P. Furthermore, BayK and FPL modified the kinetic parameters of the fusion pore formation, which represent the initial contact between the vesicle lumen and the extracellular medium. A direct link between the channel activity and evoked secretion lends additional support to the view that the voltage-gated Ca(2+) channels act as a signaling molecular switch, triggering secretion upstream to ion transport into the cell.
authors.affiliation: Department of Biological Chemistry, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 919104, Israel.
authors.forename: Merav
authors.initials: M
authors.lastname: Marom
authors.forename: Yamit
authors.initials: Y
authors.lastname: Hagalili
authors.forename: Ariel
authors.initials: A
authors.lastname: Sebag
authors.forename: Lior
authors.initials: L
authors.lastname: Tzvier
authors.forename: Daphne
authors.initials: D
authors.lastname: Atlas
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000818:Animals; D001464:Barium / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002120:Calcium Channel Agonists / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D002395:Catecholamines / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D055664:Electrochemical Techniques; D007811:Lanthanum / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009154:Mutation; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011758:Pyrroles / Q000494:pharmacology*; D051381:Rats
chemical_list: D002120:Calcium Channel Agonists; D020746:Calcium Channels, L-Type; D002395:Catecholamines; C419385:L-type calcium channel alpha(1C); D021122:Protein Subunits; D011758:Pyrroles; C071658:FPL 64176; D001464:Barium; D007811:Lanthanum; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D002118:Calcium