title: Activation of ERK1/2 by store-operated calcium entry in rat parotid acinar cells.
abstract: The regulation of intracellular Ca(2+) concentration ([Ca(2+)]i) plays a critical role in a variety of cellular processes, including transcription, protein activation, vesicle trafficking, and ion movement across epithelial cells. In many cells, the activation of phospholipase C-coupled receptors hydrolyzes membrane phosphoinositides and produces the depletion of endoplasmic reticulum Ca(2+) stores, followed by the sustained elevation of [Ca(2+)]i from Ca(2+) entry across the plasma membrane via store-operated Ca(2+) entry (SOCE). Ca(2+) entry is also increased in a store-independent manner by arachidonate-regulated Ca(2+) (ARC) channels. Using rat parotid salivary gland cells, we examined multiple pathways of Ca(2+) entry/elevation to determine if they activated cell signaling proteins and whether this occurred in a pathway-dependent manner. We observed that SOCE activates extracellular signal-related kinases 1 and 2 (ERK1/2) to ∼3-times basal levels via a receptor-independent mechanism when SOCE was initiated by depleting Ca(2+) stores using the endoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin (TG). TG-initiated ERK1/2 phosphorylation increased as rapidly as that initiated by the muscarinic receptor agonist carbachol, which promoted an increase to ∼5-times basal levels. Notably, ERK1/2 phosphorylation was not increased by the global elevation of [Ca(2+)]i by Ca(2+) ionophore or by Ca(2+) entry via ARC channels in native cells, although ERK1/2 phosphorylation was increased by Ca(2+) ionophore in Par-C10 and HSY salivary cell lines. Agents and conditions that blocked SOCE in native cells, including 2-aminoethyldiphenyl borate (2-APB), SKF96363, and removal of extracellular Ca(2+), also reduced TG- and carbachol-stimulated ERK1/2 phosphorylation. TG-promoted ERK1/2 phosphorylation was blocked when SRC and Protein Kinases C (PKC) were inhibited, and it was blocked in cells pretreated with β-adrenergic agonist isoproterenol. These observations demonstrate that ERK1/2 is activated by a selective mechanism of Ca(2+) entry (SOCE) in these cells, and suggest that ERK1/2 may contribute to events downstream of SOCE.
authors.affiliation: Beth Israel Deaconess Medical Center, Department of Medicine, Division of Signal Transduction, Harvard Medical School, Boston, Massachussetts, USA. ssoltoff@bidmc.harvard.edu
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Soltoff
authors.forename: William A
authors.initials: WA
authors.lastname: Lannon
mesh_terms: D061354:Acinar Cells / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001896:Boron Compounds / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects; D002460:Cell Line; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D010306:Parotid Gland / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D001896:Boron Compounds; D015220:Calcium Channels; D019284:Thapsigargin; C109986:2-aminoethoxydiphenyl borate; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3