title: Phospho-STIM1 is a downstream effector that mediates the signaling triggered by IGF-1 in HEK293 cells.
abstract: STIM1 is a Ca(2+) sensor of the endoplasmic reticulum (ER) that triggers the activation of plasma membrane Ca(2+) channels upon depletion of Ca(2+) levels within the ER. During thapsigargin-triggered Ca(2+) store depletion, ERK1/2 phosphorylates STIM1 at Ser575, Ser608, and Ser621. This phosphorylation plays a role in the regulation of STIM1 dissociation from the microtubule plus-end binding protein EB1, an essential step for STIM1 activation by thapsigargin. However, little is known regarding the physiological role of this phosphorylation. Because IGF-1 triggers the activation of the RAF-MEK-ERK and the phosphoinositide pathways, the role of STIM1 phosphorylation in IGF-1 stimulation was studied. There was found to be phosphorylation of ERK1/2 in both the presence and the absence of extracellular Ca(2+), demonstrating that Ca(2+) influx is not essential for ERK1/2 activation. In parallel, IGF-1 triggered STIM1 phosphorylation at the aforementioned sites, an effect that was blocked by PD0325901, a MEK1/2 inhibitor used to block ERK1/2 activation. Also, STIM1-GFP was found in clusters upon IGF-1 stimulation, and STIM1-S575A/S608A/S621A-GFP strongly reduced this multimerization. Interestingly, phospho-STIM1 was mainly found in clusters when cells were treated with IGF-1, and IGF-1 triggered the dissociation of STIM1 from EB1, similarly to what has been observed for thapsigargin, suggesting that STIM1 mediates the IGF-1 signaling pathway. A study of IGF-1-stimulated NFAT translocation was therefore performed, finding that STIM1-S575A/S608A/S621A blocked this translocation, as did the fusion protein STIM1-EB1, confirming that both STIM1 phosphorylation and STIM1-EB1 dissociation are required for IGF-1-triggered Ca(2+)-dependent signaling, and demonstrating that STIM1 phosphorylation plays a role as a downstream effector of the RAF-MEK-ERK pathway and an upstream activator of Ca(2+) entry.
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Life Sciences, University of Extremadura, Badajoz 06006, Spain. Electronic address: patriciatm@unex.es.
authors.forename: Patricia
authors.initials: P
authors.lastname: Tomas-Martin
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Life Sciences, University of Extremadura, Badajoz 06006, Spain. Electronic address: ailogue@unex.es.
authors.forename: Aida M
authors.initials: AM
authors.lastname: Lopez-Guerrero
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Life Sciences, University of Extremadura, Badajoz 06006, Spain. Electronic address: vanessacr@unex.es.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Casas-Rua
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Life Sciences, University of Extremadura, Badajoz 06006, Spain. Electronic address: epozo@unex.es.
authors.forename: Eulalia
authors.initials: E
authors.lastname: Pozo-Guisado
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Life Sciences, University of Extremadura, Badajoz 06006, Spain. Electronic address: fjmartin@unex.es.
authors.forename: Francisco Javier
authors.initials: FJ
authors.lastname: Martin-Romero
mesh_terms: D001549:Benzamides / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D004159:Diphenylamine / Q000031:analogs & derivatives / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048055:Mitogen-Activated Protein Kinase 8 / Q000378:metabolism; D048056:Mitogen-Activated Protein Kinase 9 / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D055503:Protein Multimerization / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects*; D000071737:Stromal Interaction Molecule 1; D019284:Thapsigargin / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D001549:Benzamides; C500985:MAPRE1 protein, human; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; D019284:Thapsigargin; D007334:Insulin-Like Growth Factor I; C506614:mirdametinib; D004159:Diphenylamine; D048056:Mitogen-Activated Protein Kinase 9; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048055:Mitogen-Activated Protein Kinase 8; D048051:p38 Mitogen-Activated Protein Kinases; D002118:Calcium
keywords: Calcium; ERK1/2; IGF-1; NFAT; Phosphorylation; STIM1