title: Phosphorylation of STIM1 at ERK1/2 target sites regulates interaction with the microtubule plus-end binding protein EB1.
abstract: STIM1 (stromal interaction molecule 1) is a key regulator of store-operated calcium entry (SOCE). Upon depletion of Ca(2+) concentration within the endoplasmic reticulum (ER), STIM1 relocalizes at ER-plasma membrane junctions, activating store-operated calcium channels (SOCs). Although the molecular details for STIM1-SOC binding is known, the regulation of SOCE remains largely unknown. A detailed list of phosphorylated residues within the STIM1 sequence has been reported. However, the molecular pathways controlling this phosphorylation and its function are still under study. Using phosphospecific antibodies, we demonstrate that ERK1/2 mediates STIM1 phosphorylation at Ser575, Ser608 and Ser621 during Ca(2+) store depletion, and that Ca(2+) entry and store refilling restore phosphorylation to basal levels. This phosphorylation occurs in parallel to the dissociation from end-binding protein 1 (EB1), a regulator of growing microtubule ends. Although Ser to Ala mutation of residues 575, 608 and 621 showed a constitutive binding to EB1 even after Ca(2+) store depletion, Ser to Glu mutation of these residues (to mimic the phosphorylation profile attained after store depletion) triggered full dissociation from EB1. Given that wild-type STIM1 and STIM1(S575E/S608E/S621E) activate SOCE similarly, a model is proposed to explain how ERK1/2-mediated phosphorylation of STIM1 regulates SOCE. This regulation is based on the phosphorylation of STIM1 to trigger dissociation from EB1 during Ca(2+) store depletion, an event that is fully reversed by Ca(2+) entry and store refilling.
authors.affiliation: Department of Biochemistry and Molecular Biology, College of Life Sciences, University of Extremadura, Badajoz 06006, Spain.
authors.forename: Eulalia
authors.initials: E
authors.lastname: Pozo-Guisado
authors.forename: Vanessa
authors.initials: V
authors.lastname: Casas-Rua
authors.forename: Patricia
authors.initials: P
authors.lastname: Tomas-Martin
authors.forename: Aida M
authors.initials: AM
authors.lastname: Lopez-Guerrero
authors.forename: Alberto
authors.initials: A
authors.lastname: Alvarez-Barrientos
authors.forename: Francisco Javier
authors.initials: FJ
authors.lastname: Martin-Romero
mesh_terms: D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000502:physiology*; D009154:Mutation / Q000235:genetics; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D000071737:Stromal Interaction Molecule 1; D019076:Transgenes / Q000235:genetics
chemical_list: D015220:Calcium Channels; C405804:EB1 microtubule binding proteins; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; D048049:Extracellular Signal-Regulated MAP Kinases; D002118:Calcium
keywords: Calcium; EB1; ERK1/2; Phosphorylation; STIM1; Store-operated calcium entry