Structural perturbations induced by Asn131 and Asn171 glycosylation converge within the EFSAM core and enhance stromal interaction molecule-1 mediated store operated calcium entry

Yoo Jung Choi, Yue Zhao, Moshmi Bhattacharya, Peter B. Stathopulos

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

A major intracellular calcium (Ca2 +) uptake pathway in both excitable and non-excitable eukaryotic cells is store-operated Ca2 + entry (SOCE). SOCE is the process by which endoplasmic reticulum (ER)-stored Ca2 + depletion leads to activation of plasma membrane Ca2 + channels to provide a sustained increase in cytosolic Ca2 + levels that mediate a plethora of physiological processes ranging from the immune response to platelet aggregation. Stromal interaction molecule-1 (STIM1) is the principal regulator of SOCE and responds to changes in ER stored Ca2 + through luminal sensing machinery composed of EF-hand and SAM domains (EFSAM). The EFSAM domain can undergo N-glycosylation at Asn131 and Asn171 sites; however, the precise role of EFSAM N-glycosylation in the Ca2 + sensing mechanism of STIM1 is unclear. By establishing a site-specific chemical approach to covalently linking glucose to EFSAM and examining α-helicity, thermal stability, three dimensional atomic-resolution structure, Ca2 + binding affinity and oligomerization, we show that N-glycosylation of the EFSAM domain enhances the properties that promote STIM1 activation. This augmentation occurs through changes in structure localized near the Asn131 and Asn171 sites that together permeate through the protein core and lead to decreased Ca2 + binding affinity, reduced stability and enhanced oligomerization. Congruently, Ca2 + influx via SOCE in HEK293 cells co-expressing Orai1 and STIM1 was diminished when N-glycosylation was blocked by introducing Asn131Gln and Asn171Gln mutations. Collectively, our data suggests that N-glycosylation enhances the EFSAM destabilization-coupled oligomerization in response to ER Ca2 + depletion thereby augmenting the role of STIM1 as a robust ON/OFF regulator of SOCE. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech.

Original languageEnglish (US)
Pages (from-to)1054-1063
Number of pages10
JournalBiochimica et Biophysica Acta - Molecular Cell Research
Volume1864
Issue number6
DOIs
StatePublished - Jun 1 2017

All Science Journal Classification (ASJC) codes

  • Molecular Biology
  • Cell Biology

Keywords

  • EFSAM
  • N-glycosylation
  • Nuclear magnetic resonance spectroscopy
  • Stability
  • Store-operated calcium entry
  • Stromal interaction molecule-1

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