title: A store-operated Ca(2+) influx pathway in the bag cell neurons of Aplysia.
abstract: Although store-operated Ca(2+) influx has been well-studied in nonneuronal cells, an understanding of its nature in neurons remains poor. In the bag cell neurons of Aplysia californica, prior work has suggested that a Ca(2+) entry pathway can be activated by Ca(2+) store depletion. Using fura-based imaging of intracellular Ca(2+) in cultured bag cell neurons, we now characterize this pathway as store-operated Ca(2+) influx. In the absence of extracellular Ca(2+), the endoplasmic reticulum Ca(2+)-ATPase inhibitors, cyclopiazonic acid (CPA) or thapsigargin, depleted intracellular stores and elevated intracellular free Ca(2+). With the subsequent addition of extracellular Ca(2+), a prominent Ca(2+) influx was observed. The ryanodine receptor agonist, chloroethylphenol (CEP), also increased intracellular Ca(2+) but did not initiate store-operated Ca(2+) influx, despite overlap between CEP- and CPA-sensitive stores. Bafilomycin A, a vesicular H(+)-ATPase inhibitor, liberated intracellular Ca(2+) from acidic stores and attenuated subsequent Ca(2+) influx, presumably by replenishing CPA-depleted stores. Store-operated Ca(2+) influx was partially blocked by low concentrations of La(3+) or BTP2, and strongly inhibited by either 1-[b-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole (SKF-96365) or a high concentration of Ni(2+). Regarding IP(3) receptor blockers, 2-aminoethyldiphenyl borate, but not xestospongin C, prevented store-operated Ca(2+) influx. However, jasplakinolide, an actin stabilizer reported to inhibit this pathway in smooth muscle cell lines, was ineffective. The bag cell neurons initiate reproductive behavior through a prolonged afterdischarge associated with intracellular Ca(2+) release and neuropeptide secretion. Store-operated Ca(2+) influx may serve to replenish stores depleted during the afterdischarge or participate in the release of peptide that triggers behavior.
authors.affiliation: Department of Physiology, Queen's University, 4th Floor, Botterell Hall, 18 Stuart St., Kingston, ON, K7L 3N6, Canada.
authors.forename: Babak A
authors.initials: BA
authors.lastname: Kachoei
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Knox
authors.forename: Didier
authors.initials: D
authors.lastname: Uthuza
authors.forename: Simon
authors.initials: S
authors.lastname: Levy
authors.forename: Leonard K
authors.initials: LK
authors.lastname: Kaczmarek
authors.forename: Neil S
authors.initials: NS
authors.lastname: Magoski
mesh_terms: D000813:Anilides / Q000494:pharmacology; D000818:Animals; D001048:Aplysia / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology*; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D007211:Indoles / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D007811:Lanthanum / Q000494:pharmacology; D047028:Macrocyclic Compounds / Q000494:pharmacology; D008564:Membrane Potentials / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D009532:Nickel / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects; D019284:Thapsigargin / Q000494:pharmacology; D013830:Thiadiazoles / Q000494:pharmacology
chemical_list: C476308:4-methyl-4'-(3,5-bis(trifluoromethyl)-1H-pyrazol-1-yl)-1,2,3-thiadiazole-5-carboxanilide; D000813:Anilides; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004791:Enzyme Inhibitors; D007093:Imidazoles; D007202:Indicators and Reagents; D007211:Indoles; D047028:Macrocyclic Compounds; D010080:Oxazoles; D019837:Ryanodine Receptor Calcium Release Channel; D013830:Thiadiazoles; C511704:xestospongin C; D019284:Thapsigargin; D007811:Lanthanum; D009532:Nickel; D015544:Inositol 1,4,5-Trisphosphate; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; C000543:cyclopiazonic acid