The store-operated Ca2+ entry complex comprises a small cluster of STIM1 associated with one Orai1 channel.
Proc Natl Acad Sci U S A
; 118(10)2021 03 09.
Article
em En
| MEDLINE
| ID: mdl-33649206
ABSTRACT
Increases in cytosolic Ca2+ concentration regulate diverse cellular activities and are usually evoked by opening of Ca2+ channels in intracellular Ca2+ stores and the plasma membrane (PM). For the many signals that evoke formation of inositol 1,4,5-trisphosphate (IP3), IP3 receptors coordinate the contributions of these two Ca2+ sources by mediating Ca2+ release from the endoplasmic reticulum (ER). Loss of Ca2+ from the ER then activates store-operated Ca2+ entry (SOCE) by causing dimers of STIM1 to cluster and unfurl cytosolic domains that interact with the PM Ca2+ channel, Orai1, causing its pore to open. The relative concentrations of STIM1 and Orai1 are important, but most analyses of their interactions use overexpressed proteins that perturb the stoichiometry. We tagged endogenous STIM1 with EGFP using CRISPR/Cas9. SOCE evoked by loss of ER Ca2+ was unaffected by the tag. Step-photobleaching analysis of cells with empty Ca2+ stores revealed an average of 14.5 STIM1 molecules within each sub-PM punctum. The fluorescence intensity distributions of immunostained Orai1 puncta were minimally affected by store depletion, and similar for Orai1 colocalized with STIM1 puncta or remote from them. We conclude that each native SOCE complex is likely to include only a few STIM1 dimers associated with a single Orai1 channel. Our results, demonstrating that STIM1 does not assemble clusters of interacting Orai channels, suggest mechanisms for digital regulation of SOCE by local depletion of the ER.
Palavras-chave
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Cálcio
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Sinalização do Cálcio
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Retículo Endoplasmático
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Multimerização Proteica
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Molécula 1 de Interação Estromal
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Proteína ORAI1
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Proteínas de Neoplasias
Tipo de estudo:
Risk_factors_studies
Limite:
Humans
Idioma:
En
Ano de publicação:
2021
Tipo de documento:
Article