Phosphorylation of STIM1 at ERK1/2 target sites modulates store-operated calcium entry

Store-operated calcium entry (SOCE) is an important Ca²⁺ entry pathway that regulates many cell functions. Upon store depletion, STIM1, a transmembrane protein located in the endoplasmic reticulum (ER), aggregates and relocates close to the plasma membrane (PM) where it activates store-operated calc...

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Veröffentlicht in:Journal of cell science 2010-09, Vol.123 (18), p.3084-3093
Hauptverfasser: Pozo-Guisado, Eulalia, Campbell, David G, Deak, Maria, Álvarez-Barrientos, Alberto, Morrice, Nicholas A, Álvarez, Ignacio S, Alessi, Dario R, Martín-Romero, Francisco Javier
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Sprache:eng
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Zusammenfassung:Store-operated calcium entry (SOCE) is an important Ca²⁺ entry pathway that regulates many cell functions. Upon store depletion, STIM1, a transmembrane protein located in the endoplasmic reticulum (ER), aggregates and relocates close to the plasma membrane (PM) where it activates store-operated calcium channels (SOCs). Although STIM1 was early defined as a phosphoprotein, the contribution of the phosphorylation has been elusive. In the present work, STIM1 was found to be a target of extracellular-signal-regulated kinases 1 and 2 (ERK1/2) in vitro, and we have defined the ERK1/2-phosphorylated sites on the STIM1 sequence. Using HEK293 cells stably transfected for the expression of tagged STIM1, we found that alanine substitution mutants of ERK1/2 target sites reduced SOCE significantly, suggesting that phosphorylation of these residues are required to fully accomplish SOCE. Indeed, the ERK1/2 inhibitors PD184352 and PD0325901 decreased SOCE in transfected cells. Conversely, 12-O-tetradecanoylphorbol-13-acetate, which activates ERK1/2, enhanced SOCE in cells expressing wild-type tagged STIM1, but did not potentiate Ca²⁺ influx in cells expressing serine to alanine mutations in ERK1/2 target sites of STIM1. Alanine substitution mutations decreased Ca²⁺ influx without disturbing the aggregation of STIM1 upon store depletion and without affecting the relocalization in ER-PM punctae. However, our results suggest that STIM1 phosphorylation at ERK1/2 target sites can modulate SOCE by altering STIM1 binding to SOCs, because a significant decrease in FRET efficiency was observed between alanine substitution mutants of STIM1-GFP and ORAI1-CFP.
ISSN:0021-9533
1477-9137
DOI:10.1242/jcs.067215