An apical Phe-His pair defines the Orai1-coupling site and its occlusion within STIM1
Ca 2+ signal-generation through inter-membrane junctional coupling between endoplasmic reticulum (ER) STIM proteins and plasma membrane (PM) Orai channels, remains a vital but undefined mechanism. We identify two unusual overlapping Phe-His aromatic pairs within the STIM1 apical helix, one of which...
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Veröffentlicht in: | Nature communications 2023-10, Vol.14 (1), p.6921-6921, Article 6921 |
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Sprache: | eng |
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Zusammenfassung: | Ca
2+
signal-generation through inter-membrane junctional coupling between endoplasmic reticulum (ER) STIM proteins and plasma membrane (PM) Orai channels, remains a vital but undefined mechanism. We identify two unusual overlapping Phe-His aromatic pairs within the STIM1 apical helix, one of which (F394-H398) mediates important control over Orai1-STIM1 coupling. In resting STIM1, this locus is deeply clamped within the folded STIM1-CC1 helices, likely near to the ER surface. The clamped environment in holo-STIM1 is critical—positive charge replacing Phe-394 constitutively unclamps STIM1, mimicking store-depletion, negative charge irreversibly locks the clamped-state. In store-activated, unclamped STIM1, Phe-394 mediates binding to the Orai1 channel, but His-398 is indispensable for transducing STIM1-binding into Orai1 channel-gating, and is spatially aligned with Phe-394 in the exposed Sα2 helical apex. Thus, the Phe-His locus traverses between ER and PM surfaces and is decisive in the two critical STIM1 functions—unclamping to activate STIM1, and conformational-coupling to gate the Orai1 channel.
The intermembrane complexes mediating calcium signals are crucial but poorly understood. Here the authors identify a Phe-His pair in the calcium-sensing STIM1 protein that controls both activation and pairing of STIM1 with Orai channels to generate calcium signals |
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ISSN: | 2041-1723 2041-1723 |
DOI: | 10.1038/s41467-023-42254-x |