Structural and mechanistic insights into STIM1-mediated initiation of store-operated calcium entry.
Stromal interaction molecule-1 (STIM1) activates store-operated Ca2+ entry (SOCE) in response to diminished luminal Ca2+ levels. Here, we present the atomic structure of the Ca2+-sensing region of STIM1 consisting of the EF-hand and sterile alpha motif (SAM) domains (EF-SAM). The canonical EF-hand is paired with a previously unidentified EF-hand. Together, the EF-hand pair mediates mutually indispensable hydrophobic interactions between the EF-hand and SAM domains. Structurally critical mutations in the canonical EF-hand, "hidden" EF-hand, or SAM domain disrupt Ca2+ sensitivity in oligomerization via destabilization of the entire EF-SAM entity. In mammalian cells, EF-SAM destabilization mutations within full-length STIM1 induce punctae formation and activate SOCE independent of luminal Ca2+. We provide atomic resolution insight into the molecular basis for STIM1-mediated SOCE initiation and show that the folded/unfolded state of the Ca2+-sensing region of STIM is crucial to SOCE regulation.
Stathopulos
Peter B
PB
Division of Signaling Biology, Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, Toronto Medical Discovery Tower, MaRS Centre, 101 College Street, Toronto, Ontario M5G 1L7, Canada.
Zheng
Le
L
Li
Guang-Yao
GY
Plevin
Michael J
MJ
Ikura
Mitsuhiko
M
D000595:Amino Acid Sequence; D000818:Animals; D020013:Calcium Signaling / Q000235:genetics; D004252:DNA Mutational Analysis; D020832:EF Hand Motifs; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000737:chemistry* / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D016415:Sequence Alignment; D000071737:Stromal Interaction Molecule 1
D008565:Membrane Proteins; D009363:Neoplasm Proteins; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1