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Extracellular ATP activates store-operated Ca2+ entry in white adipocytes: functional evidence for STIM1 and ORAI1

Journal article
Authors Michael El Hachmane
Anna Ermund
Cecilia Brännmark
Charlotta S Olofsson
Published in Biochemical Journal
Volume 475
Pages 691-704
ISSN 0264-6021
Publication year 2018
Published at Institute of Neuroscience and Physiology, Department of Physiology
Institute of Biomedicine, Department of Medical Biochemistry and Cell Biology
Pages 691-704
Language en
Links dx.doi.org/10.1042/bcj20170484
Keywords cytosolic-free calcium, intracellular calcium, leptin secretion, adipose-tissue, chromaffin cells, channel function, rat adipocytes, trpc, channels, fat-cells, lipolysis, Biochemistry & Molecular Biology
Subject categories Biochemistry and Molecular Biology

Abstract

In the present study, we have applied ratiometric measurements of intracellular Ca2+ concentrations ([Ca2+](i)) to show that extracellularly applied ATP (adenosine triphosphate) (100 mM) stimulates store-operated Ca2+ entry (SOCE) in 3T3-L1 adipocytes. ATP produced a rapid increase in [Ca2+](i) consisting of an initial transient elevation followed by a sustained elevated phase that could be observed only in the presence of extracellular Ca2+. Gene expression data and [Ca2+](i) recordings with uridine-50-triphosphate or with the phospholipase C (PLC) inhibitor U73122 demonstrated the involvement of purinergic P2Y2 receptors and the PLC/inositol trisphosphate pathway. The [Ca2+](i) elevation produced by reintroduction of a Ca2+-containing intracellular solution to adipocytes exposed to ATP in the absence of Ca2+ was diminished by known SOCE antagonists. The chief molecular components of SOCE, the stromal interaction molecule 1 (STIM1) and the calcium release-activated calcium channel protein 1 (ORAI1), were detected at the mRNA and protein level. Moreover, SOCE was largely diminished in cells where STIM1 and/or ORAI1 had been silenced by small interfering (si) RNA. We conclude that extracellular ATP activates SOCE in white adipocytes, an effect predominantly mediated by STIM1 and ORAI1.

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