Identification of molecular determinants that govern distinct STIM2 activation dynamics

• Published in: PLoS biology 2018-11, Vol.16 (11), p.e2006898-e2006898
• Main Authors: Zheng, Sisi, Ma, Guolin, He, Lian, Zhang, Tian, Li, Jia, Yuan, Xiaoman, Nguyen, Nhung T, Huang, Yun, Zhang, Xiaoyan, Gao, Ping, Nwokonko, Robert, Gill, Donald L, Dong, Hao, Zhou, Yubin, Wang, Youjun
• Format: Article
• Language: English
• Subjects: Activation; Biological control systems; Biology and Life Sciences; Calcium; Calcium (extracellular); Calcium (reticular); Calcium - metabolism; Calcium Channels - metabolism; Calcium homeostasis; Calcium influx; Calcium ions; Calcium Signaling - physiology; Calcium signalling; Cancer; Cell Membrane - physiology; Depletion; Endoplasmic reticulum; Endoplasmic Reticulum - metabolism; Energy transfer; Engineering; Engineering and Technology; Fluorescence resonance energy transfer; Fluorescence Resonance Energy Transfer - methods; HEK293 Cells; HeLa Cells; Homeostasis; Humans; Laboratories; Life sciences; Mammalian cells; Mammals; Medical research; Medicine; Membrane proteins; Membrane Proteins - metabolism; Mutation; Neoplasm Proteins - genetics; Neoplasm Proteins - metabolism; Neoplasm Proteins - physiology; People and Places; Physiological aspects; Physiological research; Physiology; Protein engineering; Proteins; Research and Analysis Methods; Science Policy; Sensors; STIM1 protein; Stromal Interaction Molecule 1 - genetics; Stromal Interaction Molecule 1 - metabolism; Stromal Interaction Molecule 1 - physiology; Stromal Interaction Molecule 2 - genetics; Stromal Interaction Molecule 2 - metabolism; Stromal Interaction Molecule 2 - physiology; Topology; University colleges
• ISSN: 1545-7885; 1544-9173; 1545-7885
• DOI: 10.1371/journal.pbio.2006898

The endoplasmic reticulum (ER) Ca2+ sensors stromal interaction molecule 1 (STIM1) and STIM2, which connect ER Ca2+ depletion with extracellular Ca2+ influx, are crucial for the maintenance of Ca2+ homeostasis in mammalian cells. Despite the recent progress in unraveling the role of STIM2 in Ca2+ signaling, the mechanistic underpinnings of its activation remain underexplored. We use an engineering approach to direct ER-resident STIMs to the plasma membrane (PM) while maintaining their correct membrane topology, as well as Förster resonance energy transfer (FRET) sensors that enabled in cellulo real-time monitoring of STIM activities. This allowed us to determine the calcium affinities of STIM1 and STIM2 both in cellulo and in situ, explaining the current discrepancies in the literature. We also identified the key structural determinants, especially the corresponding G residue in STIM1, which define the distinct activation dynamics of STIM2. The chimeric E470G mutation could switch STIM2 from a slow and weak Orai channel activator into a fast and potent one like STIM1 and vice versa. The systemic dissection of STIM2 activation by protein engineering sets the stage for the elucidation of the regulation and function of STIM2-mediated signaling in mammals.