Gamage Thilini H, Grabmayr Herwig, Horvath Ferdinand, Fahrner Marc, Misceo Doriana, Louch William Edward, Gunnes Gjermund, Pullisaar Helen, Reseland Janne Elin, Lyngstadaas Staale Petter, Holmgren Asbjørn, Amundsen Silja S, Rathner Petr, Cerofolini Linda, Ravera Enrico, Krobath Heinrich, Luchinat Claudio, Renger Thomas, Müller Norbert, Romanin Christoph, Frengen Eirik
Department of Medical Genetics, Oslo University Hospital and University of Oslo, 0450 Oslo, Norway.
Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria.
Sci Signal. 2023 Feb 7;16(771):eadd0509. doi: 10.1126/scisignal.add0509.
Stormorken syndrome is a multiorgan hereditary disease caused by dysfunction of the endoplasmic reticulum (ER) Ca sensor protein STIM1, which forms the Ca release-activated Ca (CRAC) channel together with the plasma membrane channel Orai1. ER Ca store depletion activates STIM1 by releasing the intramolecular "clamp" formed between the coiled coil 1 (CC1) and CC3 domains of the protein, enabling the C terminus to extend and interact with Orai1. The most frequently occurring mutation in patients with Stormorken syndrome is R304W, which destabilizes and extends the STIM1 C terminus independently of ER Ca store depletion, causing constitutive binding to Orai1 and CRAC channel activation. We found that in cis deletion of one amino acid residue, Glu (which we called E296del) reversed the pathological effects of R304W. Homozygous Stim1 E296del+R304W mice were viable and phenotypically indistinguishable from wild-type mice. NMR spectroscopy, molecular dynamics simulations, and cellular experiments revealed that although the R304W mutation prevented CC1 from interacting with CC3, the additional deletion of Glu opposed this effect by enabling CC1-CC3 binding and restoring the CC domain interactions within STIM1 that are critical for proper CRAC channel function. Our results provide insight into the activation mechanism of STIM1 by clarifying the molecular basis of mutation-elicited protein dysfunction and pathophysiology.
斯托莫尔肯综合征是一种多器官遗传性疾病，由内质网（ER）钙传感器蛋白STIM1功能障碍引起，该蛋白与质膜通道Orai1共同形成钙释放激活钙（CRAC）通道。内质网钙库耗竭通过释放蛋白质的卷曲螺旋1（CC1）和CC3结构域之间形成的分子内“夹子”来激活STIM1，使C末端能够延伸并与Orai1相互作用。斯托莫尔肯综合征患者中最常见的突变是R304W，它使STIM1的C末端不稳定并延长，而与内质网钙库耗竭无关，导致与Orai1的组成性结合和CRAC通道激活。我们发现，在顺式缺失一个氨基酸残基Glu（我们称之为E296del）后，可逆转R304W的病理效应。纯合子Stim1 E296del+R304W小鼠存活，表型与野生型小鼠无异。核磁共振光谱、分子动力学模拟和细胞实验表明，虽然R304W突变阻止了CC1与CC3相互作用，但Glu的额外缺失通过使CC1-CC3结合并恢复STIM1内对CRAC通道正常功能至关重要的CC结构域相互作用来对抗这种效应。我们的结果通过阐明突变引发的蛋白质功能障碍和病理生理学的分子基础，为STIM1的激活机制提供了见解。
