title: Auto-inhibitory role of the EF-SAM domain of STIM proteins in store-operated calcium entry.
abstract: Stromal interaction molecules (STIM)s function as endoplasmic reticulum calcium (Ca(2+)) sensors that differentially regulate plasma membrane Ca(2+) release activated Ca(2+) channels in various cells. To probe the structural basis for the functional differences between STIM1 and STIM2 we engineered a series of EF-hand and sterile α motif (SAM) domain (EF-SAM) chimeras, demonstrating that the STIM1 Ca(2+)-binding EF-hand and the STIM2 SAM domain are major contributors to the autoinhibition of oligomerization in each respective isoform. Our nuclear magnetic resonance (NMR) derived STIM2 EF-SAM structure provides a rationale for an augmented stability, which involves a 54° pivot in the EF-hand:SAM domain orientation permissible by an expanded nonpolar cleft, ionic interactions, and an enhanced hydrophobic SAM core, unique to STIM2. Live cells expressing "super-unstable" or "super-stable" STIM1/STIM2 EF-SAM chimeras in the full-length context show a remarkable correlation with the in vitro data. Together, our data suggest that divergent Ca(2+)- and SAM-dependent stabilization of the EF-SAM fold contributes to the disparate regulation of store-operated Ca(2+) entry by STIM1 and STIM2.
authors.affiliation: Division of Signaling Biology, Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada M5G 1L7.
authors.forename: Le
authors.initials: L
authors.lastname: Zheng
authors.forename: Peter B
authors.initials: PB
authors.lastname: Stathopulos
authors.forename: Rainer
authors.initials: R
authors.lastname: Schindl
authors.forename: Guang-Yao
authors.initials: GY
authors.lastname: Li
authors.forename: Christoph
authors.initials: C
authors.lastname: Romanin
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Ikura
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020832:EF Hand Motifs; D004721:Endoplasmic Reticulum / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000071740:ORAI1 Protein; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D000071737:Stromal Interaction Molecule 1; D000071738:Stromal Interaction Molecule 2; D014162:Transfection
chemical_list: D015220:Calcium Channels; D015815:Cell Adhesion Molecules; D008164:Luminescent Proteins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; C103530:STIM1 protein, human; C513279:STIM2 protein, human; D000071737:Stromal Interaction Molecule 1; D000071738:Stromal Interaction Molecule 2; D002118:Calcium