title: 2-Aminoethoxydiphenyl borate perturbs hormone-sensitive calcium stores and blocks store-operated calcium influx pathways independent of cytoskeletal disruption in human A549 lung cancer cells.
abstract: Recent studies have identified novel actions for 2-aminoethoxydiphenyl borate (2-APB) in triggering calcium release and enhancing calcium influx induced by the depletion of intracellular calcium stores. In this study, we have examined the effects of 2-APB on the human lung adenocarcinoma A549 cell line, which we have previously shown displays a unique calcium influx response, when ER calcium stores are depleted by thapsigargin (TG) treatment. Here, we show that low concentrations of 2-APB failed to induce the rapid augmentation of TG-activated calcium influx previously reported for other cell types. We observed that store-operated calcium (SOC) channels in the A549 cell line exhibited short-term sensitivity to low doses of 2-APB, perhaps reflecting a delayed augmentation of SOC channel activity or the recruitment of 2-APB-insensitive SOC channels. In both intact and permeabilized cells, 2-APB effectively discharged a subset of A549 calcium pools corresponding to the hormone-sensitive intracellular calcium stores. The 2-APB-induced calcium release produced a long-lasting perturbation of the adenosine triphosphate (ATP)-releasable calcium pools, effectively uncoupling ATP-activated calcium release even, when stores are replenished with calcium. In contrast to previous reports, we found that disruption of either the actin or microtubule-based cytoskeleton failed to block the 2-APB-induced effects on calcium signaling in A549 cells. Our study describes novel cytoskeletal-independent effects of 2-APB on Ca2+-signaling pathways, revealing differentially sensitive Ca2+-influx pathways and long-term perturbation of hormone-sensitive Ca2+ stores.
authors.affiliation: Department of Physiology and Pharmacology, Thomas J. Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, CA 95211, USA.
authors.forename: Shanthala
authors.initials: S
authors.lastname: Padar
authors.forename: Diptiman D
authors.initials: DD
authors.lastname: Bose
authors.forename: John C
authors.initials: JC
authors.lastname: Livesey
authors.forename: David W
authors.initials: DW
authors.lastname: Thomas
mesh_terms: D000199:Actins / Q000378:metabolism; D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D001896:Boron Compounds / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D045744:Cell Line, Tumor; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism*; D004072:Digitonin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D007202:Indicators and Reagents / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D015759:Ionomycin / Q000378:metabolism; D008175:Lung Neoplasms / Q000378:metabolism* / Q000473:pathology; D018613:Microscopy, Confocal; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D017239:Paclitaxel / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors
chemical_list: D000199:Actins; D000972:Antineoplastic Agents, Phytogenic; D001896:Boron Compounds; D015220:Calcium Channels; D004791:Enzyme Inhibitors; D007202:Indicators and Reagents; D019384:Nucleic Acid Synthesis Inhibitors; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D015638:Cytochalasin D; D015759:Ionomycin; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D004072:Digitonin; D017239:Paclitaxel; D002118:Calcium