title: Effect of cell swelling on ER/PM junctional interactions and channel assembly involved in SOCE.
abstract: Store-operated calcium entry (SOCE) regulates critical cellular functions and is determined by precise ER/plasma membrane (PM) junctional interactions. Here we have assessed the effect of hypotonic cell volume increase on SOCE in a salivary gland epithelial cell line (HSG). Thapsigargin (Tg) activated a 2APB- and 1microM Gd(3+)-sensitive, inwardly rectifying, cation current, I(SOC), while hypotonic solution (150mOsm) induced cell swelling and activated an outwardly rectifying cation current that was blocked by 100microM Gd(3+) but not by 2APB. HTS addition before or after Tg attenuated the sensitivity of Ca(2+) influx to 2APB and 1microM Gd(3+). After HTS-induced volume increase, while stimulation of cells with Tg resulted in intracellular Ca(2+) release without Ca(2+) influx, stimulation with CCh caused neither internal Ca(2+) release nor Ca(2+) influx. Importantly, HTS caused the ER to recede from the plasma membrane which prevented Tg-stimulated clustering of STIM1 in the ER/PM region and association of STIM1 with TRPC1 and Orai1. Disruption of SOCE was dependent on the level of hypotonic stress as 225mOsm HTS induced relatively less cell swelling or disruption of SOCE. These results demonstrate that epithelial cells can tolerate small increases (up to 5%) in cell volume while larger increases lead to disruption of ER-PM interactions that are critical for activation of SOCE. We suggest that loss of SOCE could impact cell function and contribute to the deleterious effects of severe hypotonic stress.
authors.affiliation: Secretory Physiology Section, Molecular Physiology and Therapeutics Branch, National Institutes of Dental and Craniofacial Research, Bethesda, MD 20892, USA.
authors.forename: Xibao
authors.initials: X
authors.lastname: Liu
authors.forename: Hwei Ling
authors.initials: HL
authors.lastname: Ong
authors.forename: Biswaranjan
authors.initials: B
authors.lastname: Pani
authors.forename: Katherine
authors.initials: K
authors.lastname: Johnson
authors.forename: William B
authors.initials: WB
authors.lastname: Swaim
authors.forename: Brij
authors.initials: B
authors.lastname: Singh
authors.forename: Indu
authors.initials: I
authors.lastname: Ambudkar
mesh_terms: D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D048429:Cell Size; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006801:Humans; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D000071740:ORAI1 Protein; D018408:Patch-Clamp Techniques; D000071737:Stromal Interaction Molecule 1; D050052:TRPC Cation Channels / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D001896:Boron Compounds; D015220:Calcium Channels; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; D050052:TRPC Cation Channels; C096351:transient receptor potential cation channel, subfamily C, member 1; D019284:Thapsigargin; C109986:2-aminoethoxydiphenyl borate; D002118:Calcium