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The Orai Pore Opening Mechanism.

Adéla Tiffner1, Lena Maltan1, Sarah Weiß1

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|January 12, 2021
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Calcium (Ca2+) regulation is vital for cell function, primarily through CRAC channels formed by STIM1 and Orai1. This review details how Orai1 gating checkpoints control channel opening and pore formation.

Keywords:
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Area of Science:

  • Cellular Biology
  • Ion Channel Physiology
  • Molecular Biophysics

Background:

  • Cell survival depends on precise cytosolic calcium (Ca2+) regulation.
  • Calcium release-activated calcium (CRAC) channels, crucial for Ca2+ entry, are activated by internal Ca2+ store depletion.
  • CRAC channels comprise stromal interaction molecule 1 (STIM1) and Orai1 subunits.

Purpose of the Study:

  • To elucidate the gating mechanisms of the Orai1 channel.
  • To describe how Orai1 gating checkpoints ensure channel opening.
  • To review the role of Orai1 mutations in understanding activation pathways.

Main Methods:

  • Review of existing literature on Orai1 channel gating.
  • Analysis of Orai1 mutations and their impact on channel function.
  • Integration of knowledge on STIM1-Orai1 interaction and pore formation.

Main Results:

  • Orai1 gating involves checkpoints in transmembrane and cytosolic regions.
  • These checkpoints act concertedly to achieve an open channel conformation.
  • Orai1 mutations have identified key gating steps and their functions.

Conclusions:

  • Synergistic action of gating checkpoints maintains pore geometry and STIM1 coupling.
  • These checkpoints govern the precise opening of the Orai1 channel.
  • Further research is needed to fully understand the STIM1-Orai1 gating machinery.