title: Characterization of store-operated Ca2+ channels in pancreatic duct epithelia.
abstract: Store-operated Ca2+ channels (SOCs) are activated by depletion of intracellular Ca2+ stores following agonist-mediated Ca2+ release. Previously we demonstrated that Ca2+ influx through SOCs elicits exocytosis efficiently in pancreatic duct epithelial cells (PDEC). Here we describe the biophysical, pharmacological, and molecular properties of the duct epithelial SOCs using Ca2+ imaging, whole-cell patch-clamp, and molecular biology. In PDEC, agonists of purinergic, muscarinic, and adrenergic receptors coupled to phospholipase C activated SOC-mediated Ca2+ influx as Ca2+ was released from intracellular stores. Direct measurement of [Ca2+] in the ER showed that SOCs greatly slowed depletion of the ER. Using IP3 or thapsigargin in the patch pipette elicited inwardly rectifying SOC currents. The currents increased ∼8-fold after removal of extracellular divalent cations, suggesting competitive permeation between mono- and divalent cations. The current was completely blocked by high doses of La3+ and 2-aminoethoxydiphenyl borate (2-APB) but only partially depressed by SKF-96365. In polarized PDEC, SOCs were localized specifically to the basolateral membrane. RT-PCR screening revealed the expression of both STIM and Orai proteins for the formation of SOCs in PDEC. By expression of fluorescent STIM1 and Orai1 proteins in PDEC, we confirmed that colocalization of the two proteins increases after store depletion. In conclusion, basolateral Ca2+ entry through SOCs fills internal Ca2+ stores depleted by external stimuli and will facilitate cellular processes dependent on cytoplasmic Ca2+ such as salt and mucin secretion from the exocrine pancreatic ducts.
authors: Department of Physics, Pohang University of Science and Technology, Pohang, Republic of Korea.
authors: Mean-Hwan
authors: MH
authors: Kim
authors: Jong Bae
authors: JB
authors: Seo
authors: Lindsey A
authors: LA
authors: Burnett
authors: Bertil
authors: B
authors: Hille
authors: Duk-Su
authors: DS
authors: Koh
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D002469:Cell Separation; D004285:Dogs; D004837:Epinephrine / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D056726:Genetic Association Studies; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects; D008565:Membrane Proteins / Q000378:metabolism; D010183:Pancreatic Ducts / Q000187:drug effects / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D014544:Uridine Triphosphate / Q000494:pharmacology
chemical_list: D015220:Calcium Channels; D008565:Membrane Proteins; D043562:Receptors, G-Protein-Coupled; D002118:Calcium; D014544:Uridine Triphosphate; D004837:Epinephrine
keywords: ATP; Ca(2+) imaging; D1-ER cameleon; Epithelia; IP(3); Orai; PDEC; Patch clamp; RT-PCR; SOCs; STIM; Store-operated Ca(2+) channels; TRP; UTP; adenosine-5′-triphosphate; inositol 1,4,5-trisphosphate; pancreatic duct epithelial cells; store-operated Ca(2+) channels; uridine-5′-triphosphate
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