Oligomerization and Ca2+/calmodulin control binding of the ER Ca2+-sensors STIM1 and STIM2 to plasma membrane lipids
Ca2+ (calcium) homoeostasis and signalling rely on physical contacts between Ca2+ sensors in the ER (endoplasmic reticulum) and Ca2+ channels in the PM (plasma membrane). STIM1 (stromal interaction molecule 1) and STIM2 Ca2+ sensors oligomerize upon Ca2+ depletion in the ER lumen, contact phosphoino...
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| Main Authors: | , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
October 31, 2013
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| In: |
Bioscience reports
Year: 2013, Volume: 33, Issue: 5, Pages: 833-845 |
| ISSN: | 1573-4935 |
| DOI: | 10.1042/BSR20130089 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1042/BSR20130089 Verlag, lizenzpflichtig, Volltext: /bioscirep/article/33/5/e00077/56153/Oligomerization-and-Ca2-calmodulin-control-binding 
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| Author Notes: | Rajesh Bhardwaj, Hans-Michael Müller, Walter Nickel and Matthias Seedorf |
| Summary: | Ca2+ (calcium) homoeostasis and signalling rely on physical contacts between Ca2+ sensors in the ER (endoplasmic reticulum) and Ca2+ channels in the PM (plasma membrane). STIM1 (stromal interaction molecule 1) and STIM2 Ca2+ sensors oligomerize upon Ca2+ depletion in the ER lumen, contact phosphoinositides at the PM via their cytosolic lysine (K)-rich domains, and activate Ca2+ channels. Differential sensitivities of STIM1 and STIM2 towards ER luminal Ca2+ have been studied but responses towards elevated cytosolic Ca2+ concentration and the mechanism of lipid binding remain unclear. We found that tetramerization of the STIM1 K-rich domain is necessary for efficient binding to PI(4,5)P2-containing PM-like liposomes consistent with an oligomerization-driven STIM1 activation. In contrast, dimerization of STIM2 K-rich domain was sufficient for lipid binding. Furthermore, the K-rich domain of STIM2, but not of STIM1, forms an amphipathic α-helix. These distinct features of the STIM2 K-rich domain cause an increased affinity for PI(4,5)P2, consistent with the lower activation threshold of STIM2 and a function as regulator of basal Ca2+ levels. Concomitant with higher affinity for PM lipids, binding of CaM (calmodulin) inhibited the interaction of the STIM2 K-rich domain with liposomes in a Ca2+ and PI(4,5)P2 concentration-dependent manner. Therefore we suggest that elevated cytosolic Ca2+ concentration down-regulates STIM2-mediated ER-PM contacts via CaM binding. |
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| Item Description: | Im Titel ist "2+" hochgestellt Gesehen am 25.11.2020 |
| Physical Description: | Online Resource |
| ISSN: | 1573-4935 |
| DOI: | 10.1042/BSR20130089 |