Effects of the inflammatory cytokines TNF-α and IL-13 on stromal interaction molecule-1 aggregation in human airway smooth muscle intracellular Ca2+ regulation

Li Jia, Philippe Delmotte, Bharathi Aravamudan, Christina M. Pabelick, Y. S. Prakash, Gary C. Sieck

Research output: Contribution to journalArticle

17 Scopus citations

Abstract

Inflammation elevates intracellular Ca2+ ([Ca2+]i) concentrations in airway smooth muscle (ASM). Store-operated Ca2+ entry (SOCE) is an important source of [Ca2+]i mediated by stromal interaction molecule-1 (STIM1), a sarcoplasmic reticulum (SR) protein. In transducing SR Ca2+ depletion, STIM1 aggregates to form puncta, thereby activatingSOCE via interactions with aCa2+ release-activated Ca2+ channel protein (Orai1) in the plasma membrane. We hypothesized that STIM1 aggregation is enhanced by inflammatory cytokines, thereby augmenting SOCE in human ASM cells. We used real-time fluorescence microscopic imaging to assess the dynamics of STIM1 aggregation and SOCE after exposure to TNF-α or IL-13 in ASM cells overexpressing yellow fluorescent protein-tagged wildtype STIM1 (WT-STIM1) and STIM1mutants lacking the Ca2+-sensing EF-hand(STIM1-D76A), orlackingthecytoplasmicmembranebinding site (STIM1DK). STIM1 aggregation was analyzed by monitoring punctasizeduringtheSRCa 2+depletion inducedbycyclopiazonic acid (CPA). We found that puncta size was increased in cells expressing WT-STIM1 after CPA. However, STIM1-D76A constitutively formed puncta, whereas STIM1DK failed to form puncta. Furthermore, cytokines increased basalWT-STIM1 puncta size, and the SOCE triggered by SR Ca2+ depletion was increased in cells expressing WT-STIM1 or STIM1-D76A. Meanwhile, SOCE in cells expressing STIM1DK and STIM1 short, interfering RNA (siRNA) was decreased. Similarly, in cells overexpressing STIM1, the siRNA knockdown ofOrai1 blunted SOCE. However, exposure to cytokines increased SOCE in all cells, increased basal [Ca2+]i, and decreased SR Ca2+ content. These data suggest that cytokines induce a constitutiveincreaseinSTIM1aggregationthatcontributestoenhancedSOCE inhumanASMafter inflammation. Such effects of inflammationonSTIM1 aggregationsmay contribute to airway hyperresponsiveness.

Original languageEnglish (US)
Pages (from-to)601-608
Number of pages8
JournalAmerican journal of respiratory cell and molecular biology
Volume49
Issue number4
DOIs
StatePublished - Oct 1 2013

Keywords

  • Airway smooth muscle
  • Asthma
  • Inflammation
  • SOCE
  • STIM1

ASJC Scopus subject areas

  • Molecular Biology
  • Pulmonary and Respiratory Medicine
  • Clinical Biochemistry
  • Cell Biology

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