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Updated: Oct 16, 2025

Single-Cell Calcium Imaging for Studying the Activation of Calcium Ion Channels
Published on: December 13, 2024
High affinity associations with α-SNAP enable calcium entry via Orai1 channels
Ramanagouda Ramanagoudr-Bhojappa1, Yong Miao2, Monika Vig3
1Cancer Genetics and Comparative Genomics Branch, NHGRI, Bethesda, MD, United States of America.
Alpha-SNAP (soluble NSF attachment protein) is crucial for store-operated calcium entry (SOCE). It binds Orai1 and Stim1 channels with high affinity, enabling their functional assembly and calcium influx.
Area of Science:
- Cellular Biology
- Molecular Medicine
- Biochemistry
Background:
- Store-operated calcium entry (SOCE) is vital for cellular signaling, but its precise molecular activation mechanisms via Orai channels are not fully understood.
- Previous research indicated alpha-SNAP's role in Orai1 channel assembly and calcium selectivity.
Purpose of the Study:
- To elucidate the molecular interactions between alpha-SNAP, Orai1, and Stim1.
- To define the specific binding sites and functional significance of alpha-SNAP in SOCE regulation.
Main Methods:
- Investigated alpha-SNAP's binding affinity to Orai1 and Stim1.
- Utilized site-directed mutagenesis in Stim1 (W430) and Orai1 (V262, L74) to assess binding and function.
- Assessed the impact of mutations on alpha-SNAP association and SOCE induction.
Main Results:
- Alpha-SNAP exhibits significantly higher affinity for Stim1 and Orai1 than previously reported Stim-Orai interactions.
- Alpha-SNAP binds the CC3 subdomain of Stim1, with W430 mutation disrupting binding and SOCE.
- Alpha-SNAP interacts with Orai1's C-terminal hinge region and N-terminal domain, with V262 and L74 being critical for these interactions.
Conclusions:
- High-affinity binding of alpha-SNAP to Stim1 and Orai1 is essential for their functional assembly and the induction of SOCE.
- Identified novel binding sites and functional roles for specific residues in Stim1 and Orai1 mediated by alpha-SNAP.
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