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Sallinger M, Grabmayr H, Humer C, Bonhenry D, Romanin C, Schindl R, Derler I. Activation mechanisms and structural dynamics of STIM proteins. J Physiol 2024; 602:1475-1507. [PMID: 36651592 DOI: 10.1113/jp283828] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 01/11/2023] [Indexed: 01/19/2023] Open
Abstract
The family of stromal interaction molecules (STIM) includes two widely expressed single-pass endoplasmic reticulum (ER) transmembrane proteins and additional splice variants that act as precise ER-luminal Ca2+ sensors. STIM proteins mainly function as one of the two essential components of the so-called Ca2+ release-activated Ca2+ (CRAC) channel. The second CRAC channel component is constituted by pore-forming Orai proteins in the plasma membrane. STIM and Orai physically interact with each other to enable CRAC channel opening, which is a critical prerequisite for various downstream signalling pathways such as gene transcription or proliferation. Their activation commonly requires the emptying of the intracellular ER Ca2+ store. Using their Ca2+ sensing capabilities, STIM proteins confer this Ca2+ content-dependent signal to Orai, thereby linking Ca2+ store depletion to CRAC channel opening. Here we review the conformational dynamics occurring along the entire STIM protein upon store depletion, involving the transition from the quiescent, compactly folded structure into an active, extended state, modulation by a variety of accessory components in the cell as well as the impairment of individual steps of the STIM activation cascade associated with disease.
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Affiliation(s)
- Matthias Sallinger
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Herwig Grabmayr
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Christina Humer
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Daniel Bonhenry
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, Nove Hrady, Czech Republic
| | - Christoph Romanin
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Rainer Schindl
- Gottfried Schatz Research Centre, Medical University of Graz, Graz, Austria
- BioTechMed-Graz, Graz, Austria
| | - Isabella Derler
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
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2
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Humer C, Radiskovic T, Horváti K, Lindinger S, Groschner K, Romanin C, Höglinger C. Bidirectional Allosteric Coupling between PIP 2 Binding and the Pore of the Oncochannel TRPV6. Int J Mol Sci 2024; 25:618. [PMID: 38203789 PMCID: PMC10779433 DOI: 10.3390/ijms25010618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 12/31/2023] [Accepted: 01/01/2024] [Indexed: 01/12/2024] Open
Abstract
The epithelial ion channel TRPV6 plays a pivotal role in calcium homeostasis. Channel function is intricately regulated at different stages, involving the lipid phosphatidylinositol-4,5-bisphosphate (PIP2). Given that dysregulation of TRPV6 is associated with various diseases, including different types of cancer, there is a compelling need for its pharmacological targeting. Structural studies provide insights on how TRPV6 is affected by different inhibitors, with some binding to sites else occupied by lipids. These include the small molecule cis-22a, which, however, also binds to and thereby blocks the pore. By combining calcium imaging, electrophysiology and optogenetics, we identified residues within the pore and the lipid binding site that are relevant for regulation by cis-22a and PIP2 in a bidirectional manner. Yet, mutation of the cytosolic pore exit reduced inhibition by cis-22a but preserved sensitivity to PIP2 depletion. Our data underscore allosteric communication between the lipid binding site and the pore and vice versa for most sites along the pore.
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Affiliation(s)
- Christina Humer
- Institute of Biophysics, Johannes Kepler University Linz, 4020 Linz, Austria; (C.H.); (T.R.); (C.R.)
| | - Tamara Radiskovic
- Institute of Biophysics, Johannes Kepler University Linz, 4020 Linz, Austria; (C.H.); (T.R.); (C.R.)
| | - Kata Horváti
- Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, 1117 Budapest, Hungary;
| | - Sonja Lindinger
- Institute of Biophysics, Johannes Kepler University Linz, 4020 Linz, Austria; (C.H.); (T.R.); (C.R.)
| | - Klaus Groschner
- Gottfried Schatz Research Center, Division of Biophysics, Medical University of Graz, 8010 Graz, Austria;
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, 4020 Linz, Austria; (C.H.); (T.R.); (C.R.)
| | - Carmen Höglinger
- Institute of Biophysics, Johannes Kepler University Linz, 4020 Linz, Austria; (C.H.); (T.R.); (C.R.)
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Derler I, Romanin C. Tubular aggregate myopathy mutant unveils novel activation and inactivation mechanisms of Orai1. Cell Calcium 2023; 112:102739. [PMID: 37058922 DOI: 10.1016/j.ceca.2023.102739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 04/05/2023] [Accepted: 04/06/2023] [Indexed: 04/16/2023]
Affiliation(s)
- Isabella Derler
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria.
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria.
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Horvath F, Berlansky S, Maltan L, Grabmayr H, Fahrner M, Derler I, Romanin C, Renger T, Krobath H. Swing-out opening of stromal interaction molecule 1. Protein Sci 2023; 32:e4571. [PMID: 36691702 PMCID: PMC9929737 DOI: 10.1002/pro.4571] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 12/15/2022] [Accepted: 01/13/2023] [Indexed: 01/25/2023]
Abstract
Stromal interaction molecule 1 (STIM1) resides in the endoplasmic reticulum (ER) membrane and senses luminal calcium (Ca2+ ) concentration. STIM1 activation involves a large-scale conformational transition that exposes a STIM1 domain termed "CAD/SOAR", - which is required for activation of the calcium channel Orai. Under resting cell conditions, STIM1 assumes a quiescent state where CAD/SOAR is suspended in an intramolecular clamp formed by the coiled-coil 1 domain (CC1) and CAD/SOAR. Here, we present a structural model of the cytosolic part of the STIM1 resting state using molecular docking simulations that take into account previously reported interaction sites between the CC1α1 and CAD/SOAR domains. We corroborate and refine previously reported interdomain coiled-coil contacts. Based on our model, we provide a detailed analysis of the CC1-CAD/SOAR binding interface using molecular dynamics simulations. We find a very similar binding interface for a proposed domain-swapped configuration of STIM1, where the CAD/SOAR domain of one monomer interacts with the CC1α1 domain of another monomer of STIM1. The rich structural and dynamical information obtained from our simulations reveals novel interaction sites such as M244, I409, or E370, which are crucial for STIM1 quiescent state stability. We tested our predictions by electrophysiological and Förster resonance energy transfer experiments on corresponding single-point mutants. These experiments provide compelling support for the structural model of the STIM1 quiescent state reported here. Based on transitions observed in enhanced-sampling simulations paired with an analysis of the quiescent STIM1 conformational dynamics, our work offers a first atomistic model for CC1α1-CAD/SOAR detachment.
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Affiliation(s)
- Ferdinand Horvath
- Department for Theoretical BiophysicsJohannes Kepler University LinzLinzAustria
| | - Sascha Berlansky
- Institute of BiophysicsJohannes Kepler University LinzLinzAustria
| | - Lena Maltan
- Institute of BiophysicsJohannes Kepler University LinzLinzAustria
| | - Herwig Grabmayr
- Institute of BiophysicsJohannes Kepler University LinzLinzAustria
| | - Marc Fahrner
- Institute of BiophysicsJohannes Kepler University LinzLinzAustria
| | - Isabella Derler
- Institute of BiophysicsJohannes Kepler University LinzLinzAustria
| | | | - Thomas Renger
- Department for Theoretical BiophysicsJohannes Kepler University LinzLinzAustria
| | - Heinrich Krobath
- Department for Theoretical BiophysicsJohannes Kepler University LinzLinzAustria
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5
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Gamage TH, Grabmayr H, Horvath F, Fahrner M, Misceo D, Louch WE, Gunnes G, Pullisaar H, Reseland JE, Lyngstadaas SP, Holmgren A, Amundsen SS, Rathner P, Cerofolini L, Ravera E, Krobath H, Luchinat C, Renger T, Müller N, Romanin C, Frengen E. A single amino acid deletion in the ER Ca 2+ sensor STIM1 reverses the in vitro and in vivo effects of the Stormorken syndrome-causing R304W mutation. Sci Signal 2023; 16:eadd0509. [PMID: 36749824 DOI: 10.1126/scisignal.add0509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 01/18/2023] [Indexed: 02/09/2023]
Abstract
Stormorken syndrome is a multiorgan hereditary disease caused by dysfunction of the endoplasmic reticulum (ER) Ca2+ sensor protein STIM1, which forms the Ca2+ release-activated Ca2+ (CRAC) channel together with the plasma membrane channel Orai1. ER Ca2+ 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 Ca2+ store depletion, causing constitutive binding to Orai1 and CRAC channel activation. We found that in cis deletion of one amino acid residue, Glu296 (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 Glu296 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.
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Affiliation(s)
- Thilini H Gamage
- Department of Medical Genetics, Oslo University Hospital and University of Oslo, 0450 Oslo, Norway
| | - Herwig Grabmayr
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Ferdinand Horvath
- Institute of Theoretical Physics, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040 Linz, Austria
| | - Marc Fahrner
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Doriana Misceo
- Department of Medical Genetics, Oslo University Hospital and University of Oslo, 0450 Oslo, Norway
| | - William Edward Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, 0450 Oslo, Norway
| | - Gjermund Gunnes
- Faculty of Veterinary Medicine, Norwegian University of Life Sciences, 1430 Ås, Norway
| | - Helen Pullisaar
- Department of Biomaterials, Institute of Clinical Dentistry, University of Oslo, 0455 Oslo, Norway
| | - Janne Elin Reseland
- Department of Biomaterials, Institute of Clinical Dentistry, University of Oslo, 0455 Oslo, Norway
| | | | - Asbjørn Holmgren
- Department of Medical Genetics, Oslo University Hospital and University of Oslo, 0450 Oslo, Norway
| | - Silja S Amundsen
- Department of Medical Genetics, Oslo University Hospital and University of Oslo, 0450 Oslo, Norway
| | - Petr Rathner
- Institute of Organic Chemistry and Institute of Inorganic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040 Linz, Austria
- Institut für Analytische Chemie, University of Vienna, Währinger Straße 38, 1090 Wien, Austria
| | - Linda Cerofolini
- Magnetic Resonance Center, University of Florence and Consorzio Interuniversitario Risonanze Magnetiche di Metalloproteine, 50019 Sesto Fiorentino, Italy
| | - Enrico Ravera
- Magnetic Resonance Center, University of Florence and Consorzio Interuniversitario Risonanze Magnetiche di Metalloproteine, 50019 Sesto Fiorentino, Italy
- Department of Chemistry, Ugo Schiff, University of Florence, 50019 Sesto Fiorentino, Italy
| | - Heinrich Krobath
- Institute of Theoretical Physics, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040 Linz, Austria
| | - Claudio Luchinat
- Department of Chemistry, Ugo Schiff, University of Florence, 50019 Sesto Fiorentino, Italy
- CERM, University of Florence, 50019 Sesto Fiorentino, Italy
| | - Thomas Renger
- Institute of Theoretical Physics, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040 Linz, Austria
| | - Norbert Müller
- Institute of Organic Chemistry and Institute of Inorganic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040 Linz, Austria
- Department of Chemistry, Faculty of Science, University of South Bohemia, Branišovská 1645/31A, 370 05 České Budějovice, Czech Republic
- Institute of Biochemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040 Linz, Austria
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Eirik Frengen
- Department of Medical Genetics, Oslo University Hospital and University of Oslo, 0450 Oslo, Norway
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Humer C, Romanin C. “Functional communication between IP3R and STIM2 at subthreshold stimuli is a critical checkpoint for initiation of SOCE”. Cell Calcium 2022; 104:102574. [DOI: 10.1016/j.ceca.2022.102574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 03/21/2022] [Indexed: 11/17/2022]
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Humer C, Romanin C, Höglinger C. Highlighting the Multifaceted Role of Orai1 N-Terminal- and Loop Regions for Proper CRAC Channel Functions. Cells 2022; 11:371. [PMID: 35159181 PMCID: PMC8834118 DOI: 10.3390/cells11030371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 01/14/2022] [Accepted: 01/15/2022] [Indexed: 11/16/2022] Open
Abstract
Orai1, the Ca2+-selective pore in the plasma membrane, is one of the key components of the Ca2+release-activated Ca2+ (CRAC) channel complex. Activated by the Ca2+ sensor in the endoplasmic reticulum (ER) membrane, stromal interaction molecule 1 (STIM1), via direct interaction when ER luminal Ca2+ levels recede, Orai1 helps to maintain Ca2+ homeostasis within a cell. It has already been proven that the C-terminus of Orai1 is indispensable for channel activation. However, there is strong evidence that for CRAC channels to function properly and maintain all typical hallmarks, such as selectivity and reversal potential, additional parts of Orai1 are needed. In this review, we focus on these sites apart from the C-terminus; namely, the second loop and N-terminus of Orai1 and on their multifaceted role in the functioning of CRAC channels.
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Affiliation(s)
| | | | - Carmen Höglinger
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria; (C.H.); (C.R.)
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8
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Abstract
Harnessing single-molecule FRET illuminates the structural changes necessary for a protein to fine-tune the influx of calcium when reserves inside a cell run low.
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Affiliation(s)
- Marc Fahrner
- Institute of Biophysics, Johannes Kepler University LinzLinzAustria
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Gupta A, Kitzler CM, Rathner P, Fahrner M, Grabmayr H, Rathner A, Romanin C, Müller N. Resonance assignment of coiled-coil 3 (CC3) domain of human STIM1. Biomol NMR Assign 2021; 15:433-439. [PMID: 34417953 PMCID: PMC8481183 DOI: 10.1007/s12104-021-10042-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Accepted: 08/11/2021] [Indexed: 06/13/2023]
Abstract
The protein stromal interaction molecule 1 (STIM1) plays a pivotal role in mediating store-operated calcium entry (SOCE) into cells, which is essential for adaptive immunity. It acts as a calcium sensor in the endoplasmic reticulum (ER) and extends into the cytosol, where it changes from an inactive (tight) to an active (extended) oligomeric form upon calcium store depletion. NMR studies of this protein are challenging due to its membrane-spanning and aggregation properties. Therefore follow the divide-and-conquer approach, focusing on individual domains first is in order. The cytosolic part is predicted to have a large content of coiled-coil (CC) structure. We report the 1H, 13C, 15N chemical shift assignments of the CC3 domain. This domain is crucial for the stabilisation of the tight quiescent form of STIM1 as well as for activating the ORAI calcium channel by direct contact, in the extended active form.
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Affiliation(s)
- Agrim Gupta
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040, Linz, Austria
| | - Christian Manuel Kitzler
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040, Linz, Austria
| | - Petr Rathner
- Institute of Inorganic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040, Linz, Austria
- Institute of Analytical Chemistry, University of Vienna, Währingerstrasse 38, 1090, Vienna, Austria
| | - Marc Fahrner
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria
| | - Herwig Grabmayr
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria
| | - Adriana Rathner
- Institute of Inorganic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040, Linz, Austria
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria
| | - Norbert Müller
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040, Linz, Austria.
- Faculty of Science, University of South Bohemia, Branišovská 1645/31A, 370 05, České Budějovice, Czech Republic.
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Höglinger C, Grabmayr H, Maltan L, Horvath F, Krobath H, Muik M, Tiffner A, Renger T, Romanin C, Fahrner M, Derler I. Defects in the STIM1 SOARα2 domain affect multiple steps in the CRAC channel activation cascade. Cell Mol Life Sci 2021; 78:6645-6667. [PMID: 34498097 PMCID: PMC8558294 DOI: 10.1007/s00018-021-03933-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 08/05/2021] [Accepted: 08/27/2021] [Indexed: 01/05/2023]
Abstract
The calcium release-activated calcium (CRAC) channel consists of STIM1, a Ca2+ sensor in the endoplasmic reticulum (ER), and Orai1, the Ca2+ ion channel in the plasma membrane. Ca2+ store depletion triggers conformational changes and oligomerization of STIM1 proteins and their direct interaction with Orai1. Structural alterations include the transition of STIM1 C-terminus from a folded to an extended conformation thereby exposing CAD (CRAC activation domain)/SOAR (STIM1-Orai1 activation region) for coupling to Orai1. In this study, we discovered that different point mutations of F394 in the small alpha helical segment (STIM1 α2) within the CAD/SOAR apex entail a rich plethora of effects on diverse STIM1 activation steps. An alanine substitution (STIM1 F394A) destabilized the STIM1 quiescent state, as evident from its constitutive activity. Single point mutation to hydrophilic, charged amino acids (STIM1 F394D, STIM1 F394K) impaired STIM1 homomerization and subsequent Orai1 activation. MD simulations suggest that their loss of homomerization may arise from altered formation of the CC1α1-SOAR/CAD interface and potential electrostatic interactions with lipid headgroups in the ER membrane. Consistent with these findings, we provide experimental evidence that the perturbing effects of F394D depend on the distance of the apex from the ER membrane. Taken together, our results suggest that the CAD/SOAR apex is in the immediate vicinity of the ER membrane in the STIM1 quiescent state and that different mutations therein can impact the STIM1/Orai1 activation cascade in various manners. Legend: Upon intracellular Ca2+ store depletion of the endoplasmic reticulum (ER), Ca2+ dissociates from STIM1. As a result, STIM1 adopts an elongated conformation and elicits Ca2+ influx from the extracellular matrix (EM) into the cell due to binding to and activation of Ca2+-selective Orai1 channels (left). The effects of three point mutations within the SOARα2 domain highlight the manifold roles of this region in the STIM1/Orai1 activation cascade: STIM1 F394A is active irrespective of the intracellular ER Ca2+ store level, but activates Orai1 channels to a reduced extent (middle). On the other hand, STIM1 F394D/K cannot adopt an elongated conformation upon Ca2+ store-depletion due to altered formation of the CC1α1-SOAR/CAD interface and/or electrostatic interaction of the respective side-chain charge with corresponding opposite charges on lipid headgroups in the ER membrane (right).
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Affiliation(s)
- Carmen Höglinger
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria
| | - Herwig Grabmayr
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria
| | - Lena Maltan
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria
| | - Ferdinand Horvath
- Institute of Theoretical Physics, Johannes Kepler University Linz, Altenbergerstraße 69, 4040, Linz, Austria
| | - Heinrich Krobath
- Institute of Theoretical Physics, Johannes Kepler University Linz, Altenbergerstraße 69, 4040, Linz, Austria
| | - Martin Muik
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria
| | - Adela Tiffner
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria
| | - Thomas Renger
- Institute of Theoretical Physics, Johannes Kepler University Linz, Altenbergerstraße 69, 4040, Linz, Austria
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria
| | - Marc Fahrner
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria.
| | - Isabella Derler
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria.
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Fahrner M, Höglinger C, Romanin C. Commentary to Baraniak et al. "Orai channel C-terminal peptides are key modulators of STIM-Orai coupling and calcium signal generation" published in cell reports 35: 109322. Cell Calcium 2021; 98:102455. [PMID: 34433107 DOI: 10.1016/j.ceca.2021.102455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Accepted: 08/15/2021] [Indexed: 10/20/2022]
Affiliation(s)
- Marc Fahrner
- Institute of Biophysics, Johannes Kepler University Linz, Austria
| | - Carmen Höglinger
- Institute of Biophysics, Johannes Kepler University Linz, Austria
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12
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Rathner P, Fahrner M, Cerofolini L, Grabmayr H, Horvath F, Krobath H, Gupta A, Ravera E, Fragai M, Bechmann M, Renger T, Luchinat C, Romanin C, Müller N. Interhelical interactions within the STIM1 CC1 domain modulate CRAC channel activation. Nat Chem Biol 2021; 17:196-204. [PMID: 33106661 PMCID: PMC7610458 DOI: 10.1038/s41589-020-00672-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 09/04/2020] [Accepted: 09/11/2020] [Indexed: 01/28/2023]
Abstract
The calcium release activated calcium channel is activated by the endoplasmic reticulum-resident calcium sensor protein STIM1. On activation, STIM1 C terminus changes from an inactive, tight to an active, extended conformation. A coiled-coil clamp involving the CC1 and CC3 domains is essential in controlling STIM1 activation, with CC1 as the key entity. The nuclear magnetic resonance-derived solution structure of the CC1 domain represents a three-helix bundle stabilized by interhelical contacts, which are absent in the Stormorken disease-related STIM1 R304W mutant. Two interhelical sites between the CC1α1 and CC1α2 helices are key in controlling STIM1 activation, affecting the balance between tight and extended conformations. Nuclear magnetic resonance-directed mutations within these interhelical interactions restore the physiological, store-dependent activation behavior of the gain-of-function STIM1 R304W mutant. This study reveals the functional impact of interhelical interactions within the CC1 domain for modifying the CC1-CC3 clamp strength to control the activation of STIM1.
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Affiliation(s)
- Petr Rathner
- Institute of Organic Chemistry, Johannes Kepler University Linz, Linz, Austria
- Institute of Inorganic Chemistry, Johannes Kepler University Linz, Linz, Austria
| | - Marc Fahrner
- Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria
| | - Linda Cerofolini
- Magnetic Resonance Center (CERM), University of Florence and Consorzio Interuniversitario Risonanze Magnetiche di Metallo Proteine (CIRMMP), Sesto Fiorentino, Italy
| | - Herwig Grabmayr
- Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria
| | - Ferdinand Horvath
- Institute for Theoretical Physics, Johannes Kepler University Linz, Linz, Austria
| | - Heinrich Krobath
- Institute for Theoretical Physics, Johannes Kepler University Linz, Linz, Austria
| | - Agrim Gupta
- Institute of Organic Chemistry, Johannes Kepler University Linz, Linz, Austria
| | - Enrico Ravera
- Magnetic Resonance Center (CERM), University of Florence and Consorzio Interuniversitario Risonanze Magnetiche di Metallo Proteine (CIRMMP), Sesto Fiorentino, Italy
- Department of Chemistry, University of Florence, Sesto Fiorentino, Italy
| | - Marco Fragai
- Magnetic Resonance Center (CERM), University of Florence and Consorzio Interuniversitario Risonanze Magnetiche di Metallo Proteine (CIRMMP), Sesto Fiorentino, Italy
- Department of Chemistry, University of Florence, Sesto Fiorentino, Italy
| | - Matthias Bechmann
- Institute of Organic Chemistry, Johannes Kepler University Linz, Linz, Austria
| | - Thomas Renger
- Institute for Theoretical Physics, Johannes Kepler University Linz, Linz, Austria
| | - Claudio Luchinat
- Magnetic Resonance Center (CERM), University of Florence and Consorzio Interuniversitario Risonanze Magnetiche di Metallo Proteine (CIRMMP), Sesto Fiorentino, Italy
- Department of Chemistry, University of Florence, Sesto Fiorentino, Italy
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria.
| | - Norbert Müller
- Institute of Organic Chemistry, Johannes Kepler University Linz, Linz, Austria.
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic.
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13
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Tiffner A, Schober R, Höglinger C, Bonhenry D, Pandey S, Lunz V, Sallinger M, Frischauf I, Fahrner M, Lindinger S, Maltan L, Berlansky S, Stadlbauer M, Schindl R, Ettrich R, Romanin C, Derler I. CRAC channel opening is determined by a series of Orai1 gating checkpoints in the transmembrane and cytosolic regions. J Biol Chem 2021; 296:100224. [PMID: 33361160 PMCID: PMC7948504 DOI: 10.1074/jbc.ra120.015548] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 12/15/2020] [Accepted: 12/22/2020] [Indexed: 12/13/2022] Open
Abstract
The initial activation step in the gating of ubiquitously expressed Orai1 calcium (Ca2+) ion channels represents the activation of the Ca2+-sensor protein STIM1 upon Ca2+ store depletion of the endoplasmic reticulum. Previous studies using constitutively active Orai1 mutants gave rise to, but did not directly test, the hypothesis that STIM1-mediated Orai1 pore opening is accompanied by a global conformational change of all Orai transmembrane domain (TM) helices within the channel complex. We prove that a local conformational change spreads omnidirectionally within the Orai1 complex. Our results demonstrate that these locally induced global, opening-permissive TM motions are indispensable for pore opening and require clearance of a series of Orai1 gating checkpoints. We discovered these gating checkpoints in the middle and cytosolic extended TM domain regions. Our findings are based on a library of double point mutants that contain each one loss-of-function with one gain-of-function point mutation in a series of possible combinations. We demonstrated that an array of loss-of-function mutations are dominant over most gain-of-function mutations within the same as well as of an adjacent Orai subunit. We further identified inter- and intramolecular salt-bridge interactions of Orai subunits as a core element of an opening-permissive Orai channel architecture. Collectively, clearance and synergistic action of all these gating checkpoints are required to allow STIM1 coupling and Orai1 pore opening. Our results unravel novel insights in the preconditions of the unique fingerprint of CRAC channel activation, provide a valuable source for future structural resolutions, and help to understand the molecular basis of disease-causing mutations.
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Affiliation(s)
- Adéla Tiffner
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Romana Schober
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Carmen Höglinger
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Daniel Bonhenry
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Czech Academy of Sciences, Nove Hrady, Czechia
| | - Saurabh Pandey
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Czech Academy of Sciences, Nove Hrady, Czechia
| | - Victoria Lunz
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Matthias Sallinger
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Irene Frischauf
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Marc Fahrner
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Sonja Lindinger
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Lena Maltan
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Sascha Berlansky
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Michael Stadlbauer
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Rainer Schindl
- Gottfried Schatz Research Center, Medical University of Graz, Graz, Austria
| | - Rudiger Ettrich
- College of Biomedical Sciences, Larkin University, Miami, Florida, USA; Faculty of Mathematics and Physics, Charles University, Prague, Czechia; Department of Cellular Biology & Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, Florida, USA
| | - Christoph Romanin
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Isabella Derler
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria.
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14
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Abstract
Stromal interaction molecules (STIM) are a distinct class of ubiquitously expressed single-pass transmembrane proteins in the endoplasmic reticulum (ER) membrane. Together with Orai ion channels in the plasma membrane (PM), they form the molecular basis of the calcium release-activated calcium (CRAC) channel. An intracellular signaling pathway known as store-operated calcium entry (SOCE) is critically dependent on the CRAC channel. The SOCE pathway is activated by the ligand-induced depletion of the ER calcium store. STIM proteins, acting as calcium sensors, subsequently sense this depletion and activate Orai ion channels via direct physical interaction to allow the influx of calcium ions for store refilling and downstream signaling processes. This review article is dedicated to the latest advances in the field of STIM proteins. New results of ongoing investigations based on the recently published functional data as well as structural data from nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) simulations are reported and complemented with a discussion of the latest developments in the research of STIM protein isoforms and their differential functions in regulating SOCE.
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Affiliation(s)
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria;
| | - Marc Fahrner
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria;
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15
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Bhardwaj R, Lindinger S, Neuberger A, Nadezhdin KD, Singh AK, Cunha MR, Derler I, Gyimesi G, Reymond JL, Hediger MA, Romanin C, Sobolevsky AI. Inactivation-mimicking block of the epithelial calcium channel TRPV6. Sci Adv 2020; 6:eabe1508. [PMID: 33246965 PMCID: PMC7695471 DOI: 10.1126/sciadv.abe1508] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 10/14/2020] [Indexed: 05/25/2023]
Abstract
Epithelial calcium channel TRPV6 plays vital roles in calcium homeostasis, and its dysregulation is implicated in multifactorial diseases, including cancers. Here, we study the molecular mechanism of selective nanomolar-affinity TRPV6 inhibition by (4-phenylcyclohexyl)piperazine derivatives (PCHPDs). We use x-ray crystallography and cryo-electron microscopy to solve the inhibitor-bound structures of TRPV6 and identify two types of inhibitor binding sites in the transmembrane region: (i) modulatory sites between the S1-S4 and pore domains normally occupied by lipids and (ii) the main site in the ion channel pore. Our structural data combined with mutagenesis, functional and computational approaches suggest that PCHPDs plug the open pore of TRPV6 and convert the channel into a nonconducting state, mimicking the action of calmodulin, which causes inactivation of TRPV6 channels under physiological conditions. This mechanism of inhibition explains the high selectivity and potency of PCHPDs and opens up unexplored avenues for the design of future-generation biomimetic drugs.
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Affiliation(s)
- Rajesh Bhardwaj
- Department of Nephrology and Hypertension and Department of Biomedical Research, University of Bern, Inselspital, Freiburgstrasse 15, CH-3010 Bern, Switzerland
| | - Sonja Lindinger
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Arthur Neuberger
- Department of Biochemistry and Molecular Biophysics, Columbia University, 650 West 168th Street, New York, NY 10032, USA
| | - Kirill D Nadezhdin
- Department of Biochemistry and Molecular Biophysics, Columbia University, 650 West 168th Street, New York, NY 10032, USA
| | - Appu K Singh
- Department of Biochemistry and Molecular Biophysics, Columbia University, 650 West 168th Street, New York, NY 10032, USA
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur 208016, India
| | - Micael R Cunha
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
| | - Isabella Derler
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Gergely Gyimesi
- Department of Nephrology and Hypertension and Department of Biomedical Research, University of Bern, Inselspital, Freiburgstrasse 15, CH-3010 Bern, Switzerland
| | - Jean-Louis Reymond
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
| | - Matthias A Hediger
- Department of Nephrology and Hypertension and Department of Biomedical Research, University of Bern, Inselspital, Freiburgstrasse 15, CH-3010 Bern, Switzerland.
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria.
| | - Alexander I Sobolevsky
- Department of Biochemistry and Molecular Biophysics, Columbia University, 650 West 168th Street, New York, NY 10032, USA.
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16
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Abstract
Store-operated calcium entry (SOCE) through Orai ion channels is an intracellular signaling pathway that is initiated by ligand-induced depletion of calcium from the endoplasmic reticulum (ER) store. The molecular link between SOCE and ER store depletion is thereby provided by a distinct class of single pass ER transmembrane proteins known as stromal interaction molecules (STIM). STIM proteins are equipped with a precise N-terminal calcium sensing domain that enables them to react to changes of the ER luminal calcium concentration. Additionally, a C-terminal coiled-coil domain permits relaying of signals to Orai ion channels via direct physical interaction. In this review, we provide a brief introduction to STIM proteins with a focus on structure and function and give an overview of recent developments in the field of STIM research.
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Affiliation(s)
- Marc Fahrner
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Herwig Grabmayr
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
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17
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Cunha MR, Bhardwaj R, Carrel AL, Lindinger S, Romanin C, Parise-Filho R, Hediger MA, Reymond JL. Natural product inspired optimization of a selective TRPV6 calcium channel inhibitor. RSC Med Chem 2020; 11:1032-1040. [PMID: 33479695 PMCID: PMC7513592 DOI: 10.1039/d0md00145g] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 06/18/2020] [Indexed: 12/25/2022] Open
Abstract
Transient receptor potential vanilloid 6 (TRPV6) is a calcium channel implicated in multifactorial diseases and overexpressed in numerous cancers. We recently reported the phenyl-cyclohexyl-piperazine cis-22a as the first submicromolar TRPV6 inhibitor. This inhibitor showed a seven-fold selectivity against the closely related calcium channel TRPV5 and no activity on store-operated calcium channels (SOC), but very significant off-target effects and low microsomal stability. Here, we surveyed analogues incorporating structural features of the natural product capsaicin and identified 3OG, a new oxygenated analog with similar potency against TRPV6 (IC50 = 0.082 ± 0.004 μM) and ion channel selectivity, but with high microsomal stability and very low off-target effects. This natural product-inspired inhibitor does not exhibit any non-specific toxicity effects on various cell lines and is proposed as a new tool compound to test pharmacological inhibition of TRPV6 mediated calcium flux in disease models.
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Affiliation(s)
- Micael Rodrigues Cunha
- Department of Chemistry and Biochemistry , University of Bern , Freiestrasse 3 , 3012 Bern , Switzerland .
- Department of Pharmacy , University of São Paulo , Prof. Lineu Prestes Avenue 580 , 05508-000 São Paulo , Brazil .
| | - Rajesh Bhardwaj
- Department of Nephrology and Hypertension , University Hospital Bern , Inselspital , 3010 Bern , Switzerland .
| | - Aline Lucie Carrel
- Department of Chemistry and Biochemistry , University of Bern , Freiestrasse 3 , 3012 Bern , Switzerland .
| | - Sonja Lindinger
- Institute of Biophysics , Johannes Kepler University Linz , Gruberstrasse 40 , 4020 Linz , Austria
| | - Christoph Romanin
- Institute of Biophysics , Johannes Kepler University Linz , Gruberstrasse 40 , 4020 Linz , Austria
| | - Roberto Parise-Filho
- Department of Pharmacy , University of São Paulo , Prof. Lineu Prestes Avenue 580 , 05508-000 São Paulo , Brazil .
| | - Matthias A Hediger
- Department of Nephrology and Hypertension , University Hospital Bern , Inselspital , 3010 Bern , Switzerland .
| | - Jean-Louis Reymond
- Department of Chemistry and Biochemistry , University of Bern , Freiestrasse 3 , 3012 Bern , Switzerland .
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18
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Derler I, Romanin C. Natural photoswitches expose STIM1 activation steps. Cell Calcium 2020; 90:102240. [PMID: 32574907 DOI: 10.1016/j.ceca.2020.102240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 06/05/2020] [Accepted: 06/05/2020] [Indexed: 10/24/2022]
Abstract
STIM1, an ER-located Ca2+ sensor, activates Orai1 channels upon Ca2+-storedepletion. Prior to this, STIM1 undergoes a sequence of conformational changes, which cannot be controlled individually with high spatiotemporal resolution. Ma et al. [1] used the power of optogenetic engineering to transfer light-sensitivity to STIM1 and precisely characterize individual STIM1 activation steps.
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Affiliation(s)
- Isabella Derler
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria.
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria.
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19
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Schober R, Bonhenry D, Lunz V, Zhu J, Krizova A, Frischauf I, Fahrner M, Zhang M, Waldherr L, Schmidt T, Derler I, Stathopulos PB, Romanin C, Ettrich RH, Schindl R. Sequential activation of STIM1 links Ca 2+ with luminal domain unfolding. Sci Signal 2019; 12:eaax3194. [PMID: 31744929 DOI: 10.1126/scisignal.aax3194] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The stromal interaction molecule 1 (STIM1) has two important functions, Ca2+ sensing within the endoplasmic reticulum and activation of the store-operated Ca2+ channel Orai1, enabling plasma-membrane Ca2+ influx. We combined molecular dynamics (MD) simulations with live-cell recordings and determined the sequential Ca2+-dependent conformations of the luminal STIM1 domain upon activation. Furthermore, we identified the residues within the canonical and noncanonical EF-hand domains that can bind to multiple Ca2+ ions. In MD simulations, a single Ca2+ ion was sufficient to stabilize the luminal STIM1 complex. Ca2+ store depletion destabilized the two EF hands, triggering disassembly of the hydrophobic cleft that they form together with the stable SAM domain. Point mutations associated with tubular aggregate myopathy or cancer that targeted the canonical EF hand, and the hydrophobic cleft yielded constitutively clustered STIM1, which was associated with activation of Ca2+ entry through Orai1 channels. On the basis of our results, we present a model of STIM1 Ca2+ binding and refine the currently known initial steps of STIM1 activation on a molecular level.
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Affiliation(s)
- Romana Schober
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, A-4020 Linz, Austria
| | - Daniel Bonhenry
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, Nove Hrady CZ-373 33, Czech Republic
| | - Victoria Lunz
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, A-4020 Linz, Austria
| | - Jinhui Zhu
- Schulich Dentistry, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario N6A 5C1, Canada
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Adela Krizova
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, A-4020 Linz, Austria
| | - Irene Frischauf
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, A-4020 Linz, Austria
| | - Marc Fahrner
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, A-4020 Linz, Austria
| | - MengQi Zhang
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario N6A 5C1, Canada
- Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Linda Waldherr
- Gottfried Schatz Research Center, Medical University of Graz, A-8010 Graz, Austria
| | - Tony Schmidt
- Gottfried Schatz Research Center, Medical University of Graz, A-8010 Graz, Austria
| | - Isabella Derler
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, A-4020 Linz, Austria
| | - Peter B Stathopulos
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Christoph Romanin
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, A-4020 Linz, Austria
| | - Rüdiger H Ettrich
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, Nove Hrady CZ-373 33, Czech Republic.
- College of Biomedical Sciences, Larkin University, Miami, FL 33169, USA
| | - Rainer Schindl
- Gottfried Schatz Research Center, Medical University of Graz, A-8010 Graz, Austria.
- BioTechMed-Graz, A-8010 Graz, Austria
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20
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Cunha MR, Bhardwaj R, Lindinger S, Butorac C, Romanin C, Hediger MA, Reymond JL. Photoswitchable Inhibitor of the Calcium Channel TRPV6. ACS Med Chem Lett 2019; 10:1341-1345. [PMID: 31531207 DOI: 10.1021/acsmedchemlett.9b00298] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 08/02/2019] [Indexed: 12/11/2022] Open
Abstract
Herein we report the first photoswitchable inhibitor of Transient Receptor Potential Vanilloid 6 (TRPV6), a selective calcium channel involved in a number of diseases and in cancer progression. By surveying analogs of a previously reported TRPV6 inhibitor appended with a phenyl-diazo group, we identified a compound switching between a weak TRPV6 inhibitor in its dark, E-diazo stereoisomer (Z/E = 3:97, IC50 ≫ 10 μM) and a potent inhibitor as the Z-diazo stereoisomer accessible reversibly by UV irradiation at λ = 365 nm (Z/E = 3:1, IC50 = 1.7 ± 0.4 μM), thereby allowing precise spatiotemporal control of inhibition. This new tool compound should be useful to deepen our understanding of TRPV6.
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Affiliation(s)
- Micael R. Cunha
- Department of Chemistry and Biochemistry, NCCR TransCure, University of Bern, Freiestrasse
3, 3012 Bern, Switzerland
| | - Rajesh Bhardwaj
- Institute of Biochemistry and Molecular Medicine, NCCR TransCure, University of Bern, Bühlstrasse 28, 3012 Bern, Switzerland & Department of Nephrology and Hypertension, University Hospital Bern, Inselspital, 3010 Bern, Switzerland
| | - Sonja Lindinger
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse
40, 4020 Linz, Austria
| | - Carmen Butorac
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse
40, 4020 Linz, Austria
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse
40, 4020 Linz, Austria
| | - Matthias A. Hediger
- Institute of Biochemistry and Molecular Medicine, NCCR TransCure, University of Bern, Bühlstrasse 28, 3012 Bern, Switzerland & Department of Nephrology and Hypertension, University Hospital Bern, Inselspital, 3010 Bern, Switzerland
| | - Jean-Louis Reymond
- Department of Chemistry and Biochemistry, NCCR TransCure, University of Bern, Freiestrasse
3, 3012 Bern, Switzerland
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21
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Butorac C, Muik M, Derler I, Stadlbauer M, Lunz V, Krizova A, Lindinger S, Schober R, Frischauf I, Bhardwaj R, Hediger MA, Groschner K, Romanin C. A novel STIM1-Orai1 gating interface essential for CRAC channel activation. Cell Calcium 2019; 79:57-67. [PMID: 30831274 DOI: 10.1016/j.ceca.2019.02.009] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 02/19/2019] [Accepted: 02/20/2019] [Indexed: 11/30/2022]
Abstract
Calcium signalling through store-operated calcium (SOC) entry is of crucial importance for T-cell activation and the adaptive immune response. This entry occurs via the prototypic Ca2+ release-activated Ca2+ (CRAC) channel. STIM1, a key molecular component of this process, is located in the membrane of the endoplasmic reticulum (ER) and is initially activated upon Ca2+ store depletion. This activation signal is transmitted to the plasma membrane via a direct physical interaction that takes place between STIM1 and the highly Ca2+-selective ion channel Orai1. The activation of STIM1 induces an extended cytosolic conformation. This, in turn, exposes the CAD/SOAR domain and leads to the formation of STIM1 oligomers. In this study, we focused on a small helical segment (STIM1 α3, aa 400-403), which is located within the CAD/SOAR domain. We determined this segment's specific functional role in terms of STIM1 activation and Orai1 gating. The STIM1 α3 domain appears not essential for STIM1 to interact with Orai1. Instead, it represents a key domain that conveys STIM1 interaction into Orai1 channel gating. The results of cysteine crosslinking experiments revealed the close proximity of STIM1 α3 to a region within Orai1, which was located at the cytosolic extension of transmembrane helix 3, forming a STIM1-Orai1 gating interface (SOGI). We suggest that the interplay between STIM1 α3 and Orai1 TM3 allows STIM1 coupling to be transmitted into physiological CRAC channel activation.
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Affiliation(s)
- Carmen Butorac
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Martin Muik
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Isabella Derler
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Michael Stadlbauer
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Victoria Lunz
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Adéla Krizova
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Sonja Lindinger
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Romana Schober
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Irene Frischauf
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Rajesh Bhardwaj
- Institute of Biochemistry and Molecular Medicine, University of Bern, Buehlstrasse 28, CH-3012 Bern, Switzerland
| | - Matthias A Hediger
- Institute of Biochemistry and Molecular Medicine, University of Bern, Buehlstrasse 28, CH-3012 Bern, Switzerland
| | - Klaus Groschner
- Gottfried Schatz Forschungszentrum, Medizinische Universität Graz, Neue Stiftingtalstraße 6, 8010 Graz, Austria
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria.
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22
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Affiliation(s)
- Jonathan Soboloff
- Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, PA, 19140, United States; Department of Medical Genetics & Molecular Biochemistry, Temple University School of Medicine, Philadelphia, PA, 19140, United States.
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Life Science Center, Gruberstrasse 40, 4020 Linz, Austria.
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23
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Tiapko O, Shrestha N, Lindinger S, Guedes de la Cruz G, Graziani A, Klec C, Butorac C, Graier WF, Kubista H, Freichel M, Birnbaumer L, Romanin C, Glasnov T, Groschner K. Lipid-independent control of endothelial and neuronal TRPC3 channels by light. Chem Sci 2019; 10:2837-2842. [PMID: 30997005 PMCID: PMC6427946 DOI: 10.1039/c8sc05536j] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 01/09/2019] [Indexed: 12/25/2022] Open
Abstract
Lipid-gated TRPC channels are highly expressed in cardiovascular and neuronal tissues. Exerting precise pharmacological control over their activity in native cells is expected to serve as a basis for the development of novel therapies. Here we report on a new photopharmacological tool that enables manipulation of TRPC3 channels by light, in a manner independent of lipid metabolism and with higher temporal precision than lipid photopharmacology. Using the azobenzene photoswitch moiety, we modified GSK1702934A to generate light-controlled TRPC agonists. We obtained one light-sensitive molecule (OptoBI-1) that allows us to exert efficient, light-mediated control over TRPC3 activity and the associated cellular Ca2+ signaling. OptoBI-1 enabled high-precision, temporal control of TRPC3-linked cell functions such as neuronal firing and endothelial Ca2+ transients. With these findings, we introduce a novel photopharmacological strategy to control native TRPC conductances.
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Affiliation(s)
- Oleksandra Tiapko
- Gottfried Schatz Research Center - Biophysics , Medical University of Graz , Neue Stiftingtalstraße 6/D/04 , 8010 Graz , Austria .
| | - Niroj Shrestha
- Gottfried Schatz Research Center - Biophysics , Medical University of Graz , Neue Stiftingtalstraße 6/D/04 , 8010 Graz , Austria .
| | - Sonja Lindinger
- Institute of Biophysics , University of Linz , Gruberstrasse 40/1 , 4020 Linz , Austria
| | | | - Annarita Graziani
- Gottfried Schatz Research Center - Biophysics , Medical University of Graz , Neue Stiftingtalstraße 6/D/04 , 8010 Graz , Austria .
| | - Christiane Klec
- Gottfried Schatz Research Center - Molecular Biology and Biochemistry , Medical University of Graz , Neue Stiftingtalstraße 6/6 , 8010 Graz , Austria
| | - Carmen Butorac
- Institute of Biophysics , University of Linz , Gruberstrasse 40/1 , 4020 Linz , Austria
| | - Wolfgang F Graier
- Gottfried Schatz Research Center - Molecular Biology and Biochemistry , Medical University of Graz , Neue Stiftingtalstraße 6/6 , 8010 Graz , Austria
| | - Helmut Kubista
- Institute of Pharmacology , Medical University of Vienna , Währinger Straße 13A , 1090 Vienna , Austria
| | - Marc Freichel
- Pharmakologisches Institut , Universität Heidelberg , Im Neuenheimer Feld 366 , D-69120 Heidelberg , Germany
| | - Lutz Birnbaumer
- Neurobiology Laboratory , National Institute of Environmental Health Sciences , Research Triangle Park , North Carolina 27709 , USA
- Institute of Biomedical Research (BIOMED) , Catholique University of Argentina , Buenos Aires C1107AZZ , Argentina
| | - Christoph Romanin
- Institute of Biophysics , University of Linz , Gruberstrasse 40/1 , 4020 Linz , Austria
| | - Toma Glasnov
- Institute of Chemistry , University of Graz , Heinrichstraße 28/I , 8010 Graz , Austria
| | - Klaus Groschner
- Gottfried Schatz Research Center - Biophysics , Medical University of Graz , Neue Stiftingtalstraße 6/D/04 , 8010 Graz , Austria .
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24
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Abstract
A primary calcium (Ca2+) entry pathway into non-excitable cells is through the store-operated Ca2+ release activated Ca2+ (CRAC) channel. Ca2+ entry into cells is responsible for the initiation of diverse signalling cascades that affect essential cellular processes like gene regulation, cell growth and death, secretion and gene transcription. Upon depletion of intracellular Ca2+ stores within the endoplasmic reticulum (ER), the CRAC channel opens to refill depleted stores. The two key limiting molecular players of the CRAC channel are the stromal interaction molecule (STIM1) embedded in the ER-membrane and Orai1, residing in the plasma membrane (PM), respectively. Together, they form a highly Ca2+ selective ion channel complex. STIM1 senses the Ca2+ content of the ER and confers Ca2+ store-depletion into the opening of Orai1 channels in the PM for triggering Ca2+-dependent gene transcription, T-cell activation or mast cell degranulation. The interplay of Orai and STIM proteins in the CRAC channel signalling cascade has been the main focus of research for more than twelve years. This chapter focuses on current knowledge and main experimental advances in the understanding of Orai1 activation by STIM1, thereby portraying key mechanistic steps in the CRAC channel signalling cascade.
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Affiliation(s)
- Victoria Lunz
- Institute of Biophysics, Johannes Kepler University Linz, A-4020, Linz, Austria
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, A-4020, Linz, Austria.
| | - Irene Frischauf
- Institute of Biophysics, Johannes Kepler University Linz, A-4020, Linz, Austria.
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25
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Rathner P, Stadlbauer M, Romanin C, Fahrner M, Derler I, Müller N. Rapid NMR-scale purification of 15N, 13C isotope-labeled recombinant human STIM1 coiled coil fragments. Protein Expr Purif 2018; 146:45-50. [PMID: 29414068 DOI: 10.1016/j.pep.2018.01.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Revised: 01/05/2018] [Accepted: 01/24/2018] [Indexed: 10/17/2022]
Abstract
We report a new NMR-scale purification procedure for two recombinant wild type fragments of the stromal interaction molecule 1 (STIM1). This protein acts as a calcium sensor in the endoplasmic reticulum (ER) and extends into the cytosol accumulating at ER - plasma membrane (PM) junctions upon calcium store depletion ultimately leading to activation of the Orai/CRAC channel. The functionally relevant cytosolic part of STIM1 consists of three coiled coil domains, which are mainly involved in intra- and inter-molecular homomeric interactions as well as coupling to and gating of CRAC channels. The optimized one-step rapid purification procedure for two 15N,13C isotope-labeled cytosolic coiled coil fragments, which avoids the problems of previous approaches. The high yields of soluble well folded 15N,13C isotope-labeled cytosolic coiled coil fragments followed by detergent screening provide for initial NMR characterization of these domains. The longer 30.5 kDa fragment represents the largest STIM1 wild type fragment that has been recombinantly prepared and characterized in solution without need for mutation or refolding.
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Affiliation(s)
- Petr Rathner
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstraße 69, 4040 Linz, Austria
| | - Michael Stadlbauer
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstraße 40, 4020 Linz, Austria
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstraße 40, 4020 Linz, Austria
| | - Marc Fahrner
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstraße 40, 4020 Linz, Austria
| | - Isabella Derler
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstraße 40, 4020 Linz, Austria
| | - Norbert Müller
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstraße 69, 4040 Linz, Austria; Faculty of Science, University of South Bohemia, Branišovská 31, 370 05 České Budějovice, Czech Republic.
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26
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Lichtenegger M, Tiapko O, Svobodova B, Stockner T, Glasnov TN, Schreibmayer W, Platzer D, de la Cruz GG, Krenn S, Schober R, Shrestha N, Schindl R, Romanin C, Groschner K. An optically controlled probe identifies lipid-gating fenestrations within the TRPC3 channel. Nat Chem Biol 2018; 14:396-404. [PMID: 29556099 PMCID: PMC5903546 DOI: 10.1038/s41589-018-0015-6] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 01/12/2018] [Indexed: 12/30/2022]
Abstract
Transient receptor potential canonical (TRPC) channels TRPC3, TRPC6 and TRPC7 are able to sense the lipid messenger diacylglycerol (DAG). The DAG-sensing and lipid-gating processes in these ion channels are still unknown. To gain insights into the lipid-sensing principle, we generated a DAG photoswitch, OptoDArG, that enabled efficient control of TRPC3 by light. A structure-guided mutagenesis screen of the TRPC3 pore domain unveiled a single glycine residue behind the selectivity filter (G652) that is exposed to lipid through a subunit-joining fenestration. Exchange of G652 with larger residues altered the ability of TRPC3 to discriminate between different DAG molecules. Light-controlled activation-deactivation cycling of TRPC3 channels by an OptoDArG-mediated optical 'lipid clamp' identified pore domain fenestrations as pivotal elements of the channel´s lipid-sensing machinery. We provide evidence for a novel concept of lipid sensing by TRPC channels based on a lateral fenestration in the pore domain that accommodates lipid mediators to control gating.
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Affiliation(s)
- Michaela Lichtenegger
- Gottfried Schatz Research Center, Biophysics, Medical University of Graz, Graz, Austria
| | - Oleksandra Tiapko
- Gottfried Schatz Research Center, Biophysics, Medical University of Graz, Graz, Austria
| | - Barbora Svobodova
- Gottfried Schatz Research Center, Biophysics, Medical University of Graz, Graz, Austria
| | - Thomas Stockner
- Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
| | | | - Wolfgang Schreibmayer
- Gottfried Schatz Research Center, Biophysics, Medical University of Graz, Graz, Austria
| | - Dieter Platzer
- Gottfried Schatz Research Center, Biophysics, Medical University of Graz, Graz, Austria
| | | | - Sarah Krenn
- Gottfried Schatz Research Center, Biophysics, Medical University of Graz, Graz, Austria
| | - Romana Schober
- Institute of Biophysics, University of Linz, Linz, Austria
| | - Niroj Shrestha
- Gottfried Schatz Research Center, Biophysics, Medical University of Graz, Graz, Austria
| | - Rainer Schindl
- Gottfried Schatz Research Center, Biophysics, Medical University of Graz, Graz, Austria
| | | | - Klaus Groschner
- Gottfried Schatz Research Center, Biophysics, Medical University of Graz, Graz, Austria,
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27
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Fahrner M, Stadlbauer M, Muik M, Rathner P, Stathopulos P, Ikura M, Müller N, Romanin C. A dual mechanism promotes switching of the Stormorken STIM1 R304W mutant into the activated state. Nat Commun 2018; 9:825. [PMID: 29483506 PMCID: PMC5827659 DOI: 10.1038/s41467-018-03062-w] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 01/17/2018] [Indexed: 11/22/2022] Open
Abstract
STIM1 and Orai1 are key components of the Ca2+-release activated Ca2+ (CRAC) current. Orai1, which represents the subunit forming the CRAC channel complex, is activated by the ER resident Ca2+ sensor STIM1. The genetically inherited Stormorken syndrome disease has been associated with the STIM1 single point R304W mutant. The resulting constitutive activation of Orai1 mainly involves the CRAC-activating domain CAD/SOAR of STIM1, the exposure of which is regulated by the molecular interplay between three cytosolic STIM1 coiled-coil (CC) domains. Here we present a dual mechanism by which STIM1 R304W attains the pathophysiological, constitutive activity eliciting the Stormorken syndrome. The R304W mutation induces a helical elongation within the CC1 domain, which together with an increased CC1 homomerization, destabilize the resting state of STIM1. This culminates, even in the absence of store depletion, in structural extension and CAD/SOAR exposure of STIM1 R304W leading to constitutive CRAC channel activation and Stormorken disease. Stormorken syndrome is associated with the R304W mutation in STIM1, which is a Calcium sensor in the endoplasmic reticulum. Here authors use FRET and electrophysiology to show that R304W induces STIM1 conformational extension by a dual mechanism resulting in constitutive activation of Ca2+ channels.
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Affiliation(s)
- Marc Fahrner
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria.
| | - Michael Stadlbauer
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria
| | - Martin Muik
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria
| | - Petr Rathner
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040, Linz, Austria
| | - Peter Stathopulos
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Mitsu Ikura
- Princess Margaret Cancer Center, University Health Network, Toronto, ON M5G 1L7, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, ON M5G 1L7, Canada
| | - Norbert Müller
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040, Linz, Austria.,Faculty of Science, University of South Bohemia, Branišovská 1645/31A, 370 05, České Budějovice, Czech Republic
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020, Linz, Austria.
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28
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Tiapko O, Lichtenegger M, de la Cruz GG, Glasnov TN, Svobodova B, Schreibmayer W, Platzer D, Krenn S, Shrestha N, Schindl R, Stockner T, Romanin C, Groschner K. Photoswitchable Diacylglycerols Identify a Novel Lipid-Gating Mechanism in TRPC3 Channels. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.3460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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29
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Fahrner M, Pandey SK, Muik M, Traxler L, Butorac C, Stadlbauer M, Zayats V, Krizova A, Plenk P, Frischauf I, Schindl R, Gruber HJ, Hinterdorfer P, Ettrich R, Romanin C, Derler I. Communication between N terminus and loop2 tunes Orai activation. J Biol Chem 2018; 293:1271-1285. [PMID: 29237733 PMCID: PMC5787804 DOI: 10.1074/jbc.m117.812693] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 12/12/2017] [Indexed: 11/22/2022] Open
Abstract
Ca2+ release-activated Ca2+ (CRAC) channels constitute the major Ca2+ entry pathway into the cell. They are fully reconstituted via intermembrane coupling of the Ca2+-selective Orai channel and the Ca2+-sensing protein STIM1. In addition to the Orai C terminus, the main coupling site for STIM1, the Orai N terminus is indispensable for Orai channel gating. Although the extended transmembrane Orai N-terminal region (Orai1 amino acids 73-91; Orai3 amino acids 48-65) is fully conserved in the Orai1 and Orai3 isoforms, Orai3 tolerates larger N-terminal truncations than Orai1 in retaining store-operated activation. In an attempt to uncover the reason for these isoform-specific structural requirements, we analyzed a series of Orai mutants and chimeras. We discovered that it was not the N termini, but the loop2 regions connecting TM2 and TM3 of Orai1 and Orai3 that featured distinct properties, which explained the different, isoform-specific behavior of Orai N-truncation mutants. Atomic force microscopy studies and MD simulations suggested that the remaining N-terminal portion in the non-functional Orai1 N-truncation mutants formed new, inhibitory interactions with the Orai1-loop2 regions, but not with Orai3-loop2. Such a loop2 swap restored activation of the N-truncation Orai1 mutants. To mimic interactions between the N terminus and loop2 in full-length Orai1 channels, we induced close proximity of the N terminus and loop2 via cysteine cross-linking, which actually caused significant inhibition of STIM1-mediated Orai currents. In aggregate, maintenance of Orai activation required not only the conserved N-terminal region but also permissive communication of the Orai N terminus and loop2 in an isoform-specific manner.
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Affiliation(s)
- Marc Fahrner
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria, and
| | - Saurabh K. Pandey
- the Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, 373 33 Nove Hrady, Czech Republic
| | - Martin Muik
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria, and
| | - Lukas Traxler
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria, and
| | - Carmen Butorac
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria, and
| | - Michael Stadlbauer
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria, and
| | - Vasilina Zayats
- the Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, 373 33 Nove Hrady, Czech Republic
| | - Adéla Krizova
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria, and
| | - Peter Plenk
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria, and
| | - Irene Frischauf
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria, and
| | - Rainer Schindl
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria, and
| | - Hermann J. Gruber
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria, and
| | - Peter Hinterdorfer
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria, and
| | - Rüdiger Ettrich
- the Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, 373 33 Nove Hrady, Czech Republic
| | - Christoph Romanin
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria, and
| | - Isabella Derler
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria, and
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30
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Derler I, Butorac C, Krizova A, Stadlbauer M, Muik M, Fahrner M, Frischauf I, Romanin C. Authentic CRAC channel activity requires STIM1 and the conserved portion of the Orai N terminus. J Biol Chem 2018; 293:1259-1270. [PMID: 29237734 PMCID: PMC5787803 DOI: 10.1074/jbc.m117.812206] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 11/23/2017] [Indexed: 11/06/2022] Open
Abstract
Calcium (Ca2+) is an essential second messenger required for diverse signaling processes in immune cells. Ca2+ release-activated Ca2+ (CRAC) channels represent one main Ca2+ entry pathway into the cell. They are fully reconstituted via two proteins, the stromal interaction molecule 1 (STIM1), a Ca2+ sensor in the endoplasmic reticulum, and the Ca2+ ion channel Orai in the plasma membrane. After Ca2+ store depletion, STIM1 and Orai couple to each other, allowing Ca2+ influx. CRAC-/STIM1-mediated Orai channel currents display characteristic hallmarks such as high Ca2+ selectivity, an increase in current density when switching from a Ca2+-containing solution to a divalent-free Na+ one, and fast Ca2+-dependent inactivation. Here, we discovered several constitutively active Orai1 and Orai3 mutants, containing substitutions in the TM3 and/or TM4 regions, all of which displayed a loss of the typical CRAC channel hallmarks. Restoring authentic CRAC channel activity required both the presence of STIM1 and the conserved Orai N-terminal portion. Similarly, these structural requisites were found in store-operated Orai channels. Key molecular determinants within the Orai N terminus that together with STIM1 maintained the typical CRAC channel hallmarks were distinct from those that controlled store-dependent Orai activation. In conclusion, the conserved portion of the Orai N terminus is essential for STIM1, as it fine-tunes the open Orai channel gating, thereby establishing authentic CRAC channel activity.
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Affiliation(s)
- Isabella Derler
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Carmen Butorac
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Adéla Krizova
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Michael Stadlbauer
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Martin Muik
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Marc Fahrner
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Irene Frischauf
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Christoph Romanin
- From the Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
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31
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Traxler L, Rathner P, Fahrner M, Stadlbauer M, Faschinger F, Charnavets T, Müller N, Romanin C, Hinterdorfer P, Gruber HJ. Multiple Evidenz für einen ungewöhnlichen Wechselwirkungsmodus zwischen Calmodulin und Orai-Proteinen. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201708667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Lukas Traxler
- Institut für Biophysik; Johannes Kepler Universität; Gruberstrasse 40 4020 Linz Österreich
| | - Petr Rathner
- Institut für Organische Chemie; Johannes Kepler Universität; Altenberger Strasse 69 4020 Linz Österreich
| | - Marc Fahrner
- Institut für Biophysik; Johannes Kepler Universität; Gruberstrasse 40 4020 Linz Österreich
| | - Michael Stadlbauer
- Institut für Biophysik; Johannes Kepler Universität; Gruberstrasse 40 4020 Linz Österreich
| | - Felix Faschinger
- Institut für Biophysik; Johannes Kepler Universität; Gruberstrasse 40 4020 Linz Österreich
| | - Tatsiana Charnavets
- CF Centre of Molecular Structure, BIOCEV; Průmyslová 595 252 50 Vestec Tschechische Republik
| | - Norbert Müller
- Institut für Organische Chemie; Johannes Kepler Universität; Altenberger Strasse 69 4020 Linz Österreich
- Faculty of Science; University of South Bohemia; Branišovská 31 370 05 České Budějovice Tschechische Republik
| | - Christoph Romanin
- Institut für Biophysik; Johannes Kepler Universität; Gruberstrasse 40 4020 Linz Österreich
| | - Peter Hinterdorfer
- Institut für Biophysik; Johannes Kepler Universität; Gruberstrasse 40 4020 Linz Österreich
| | - Hermann J. Gruber
- Institut für Biophysik; Johannes Kepler Universität; Gruberstrasse 40 4020 Linz Österreich
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32
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Traxler L, Rathner P, Fahrner M, Stadlbauer M, Faschinger F, Charnavets T, Müller N, Romanin C, Hinterdorfer P, Gruber HJ. Detailed Evidence for an Unparalleled Interaction Mode between Calmodulin and Orai Proteins. Angew Chem Int Ed Engl 2017; 56:15755-15759. [PMID: 29024298 DOI: 10.1002/anie.201708667] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Indexed: 12/12/2022]
Abstract
Calmodulin (CaM) binds most of its targets by wrapping around an amphipathic α-helix. The N-terminus of Orai proteins contains a conserved CaM-binding segment but the binding mechanism has been only partially characterized. Here, microscale thermophoresis (MST), surface plasmon resonance (SPR), and atomic force microscopy (AFM) were employed to study the binding equilibria, the kinetics, and the single-molecule interaction forces involved in the binding of CaM to the conserved helical segments of Orai1 and Orai3. The results consistently indicated stepwise binding of two separate target peptides to the two lobes of CaM. An unparalleled high affinity was found when two Orai peptides were dimerized or immobilized at high lateral density, thereby mimicking the close proximity of the N-termini in native Orai oligomers. The analogous experiments with smooth muscle myosin light chain kinase (smMLCK) showed only the expected 1:1 binding, confirming the validity of our methods.
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Affiliation(s)
- Lukas Traxler
- Institute of Biophysics, Johannes Kepler University, Gruberstrasse 40, 4020, Linz, Austria
| | - Petr Rathner
- Institute of Organic Chemistry, Johannes Kepler University, Altenberger Strasse 69, 4020, Linz, Austria
| | - Marc Fahrner
- Institute of Biophysics, Johannes Kepler University, Gruberstrasse 40, 4020, Linz, Austria
| | - Michael Stadlbauer
- Institute of Biophysics, Johannes Kepler University, Gruberstrasse 40, 4020, Linz, Austria
| | - Felix Faschinger
- Institute of Biophysics, Johannes Kepler University, Gruberstrasse 40, 4020, Linz, Austria
| | - Tatsiana Charnavets
- CF Centre of Molecular Structure, BIOCEV, Průmyslová 595, 252 50, Vestec, Czech Republic
| | - Norbert Müller
- Institute of Organic Chemistry, Johannes Kepler University, Altenberger Strasse 69, 4020, Linz, Austria.,Faculty of Science, University of South Bohemia, Branišovská 31, 370 05, České Budějovice, Czech Republic
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University, Gruberstrasse 40, 4020, Linz, Austria
| | - Peter Hinterdorfer
- Institute of Biophysics, Johannes Kepler University, Gruberstrasse 40, 4020, Linz, Austria
| | - Hermann J Gruber
- Institute of Biophysics, Johannes Kepler University, Gruberstrasse 40, 4020, Linz, Austria
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33
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Frischauf I, Litviňuková M, Schober R, Zayats V, Svobodová B, Bonhenry D, Lunz V, Cappello S, Tociu L, Reha D, Stallinger A, Hochreiter A, Pammer T, Butorac C, Muik M, Groschner K, Bogeski I, Ettrich RH, Romanin C, Schindl R. Transmembrane helix connectivity in Orai1 controls two gates for calcium-dependent transcription. Sci Signal 2017; 10:eaao0358. [PMID: 29184031 PMCID: PMC6433236 DOI: 10.1126/scisignal.aao0358] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The channel Orai1 requires Ca2+ store depletion in the endoplasmic reticulum and an interaction with the Ca2+ sensor STIM1 to mediate Ca2+ signaling. Alterations in Orai1-mediated Ca2+ influx have been linked to several pathological conditions including immunodeficiency, tubular myopathy, and cancer. We screened large-scale cancer genomics data sets for dysfunctional Orai1 mutants. Five of the identified Orai1 mutations resulted in constitutively active gating and transcriptional activation. Our analysis showed that certain Orai1 mutations were clustered in the transmembrane 2 helix surrounding the pore, which is a trigger site for Orai1 channel gating. Analysis of the constitutively open Orai1 mutant channels revealed two fundamental gates that enabled Ca2+ influx: Arginine side chains were displaced so they no longer blocked the pore, and a chain of water molecules formed in the hydrophobic pore region. Together, these results enabled us to identify a cluster of Orai1 mutations that trigger Ca2+ permeation associated with gene transcription and provide a gating mechanism for Orai1.
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Affiliation(s)
- Irene Frischauf
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz A-4020, Austria
| | - Monika Litviňuková
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz A-4020, Austria
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Cardiovascular and Metabolic Sciences, Berlin D-13125, Germany
| | - Romana Schober
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz A-4020, Austria
| | - Vasilina Zayats
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, Nové Hrady CZ-373 33, Czech Republic
- Center of New Technologies, University of Warsaw, Warsaw 02-097, Poland
| | - Barbora Svobodová
- Institute for Biophysics, Medical University of Graz, Graz A-8010, Austria
| | - Daniel Bonhenry
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, Nové Hrady CZ-373 33, Czech Republic
| | - Victoria Lunz
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz A-4020, Austria
| | - Sabrina Cappello
- Molecular Physiology, Institute of Cardiovascular Physiology, University Medical Center, Georg August University Göttingen, Göttingen, Niedersachsen 37073, Germany
- Department of Biophysics, Center for Integrative Physiology and Molecular Medicine, Medical Faculty, Saarland University, Homburg D-66421, Germany
| | - Laura Tociu
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, Nové Hrady CZ-373 33, Czech Republic
- University of Chicago, Chicago, IL 60637, USA
| | - David Reha
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, Nové Hrady CZ-373 33, Czech Republic
- Faculty of Sciences, University of South Bohemia, Nové Hrady CZ-373 33, Czech Republic
| | - Amrutha Stallinger
- Institute for Molecular Biosciences, Karl-Franzens-University Graz, Graz A-8010, Austria
| | - Anna Hochreiter
- Institute for Experimental and Clinical Cell Therapy, Paracelsus Medical University, Salzburg A-5020, Austria
| | - Teresa Pammer
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz A-4020, Austria
| | - Carmen Butorac
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz A-4020, Austria
| | - Martin Muik
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz A-4020, Austria
| | - Klaus Groschner
- Institute for Biophysics, Medical University of Graz, Graz A-8010, Austria
| | - Ivan Bogeski
- Molecular Physiology, Institute of Cardiovascular Physiology, University Medical Center, Georg August University Göttingen, Göttingen, Niedersachsen 37073, Germany
| | - Rüdiger H Ettrich
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, Nové Hrady CZ-373 33, Czech Republic
- Faculty of Sciences, University of South Bohemia, Nové Hrady CZ-373 33, Czech Republic
| | - Christoph Romanin
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz A-4020, Austria
| | - Rainer Schindl
- Institute for Biophysics, Medical University of Graz, Graz A-8010, Austria.
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Maringer L, Grabmann M, Muik M, Nitsche D, Romanin C, Wallner G, Buchberger W. Investigations on the distribution of polymer additives in polypropylene using confocal fluorescence microscopy. International Journal of Polymer Analysis and Characterization 2017. [DOI: 10.1080/1023666x.2017.1367120] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Leila Maringer
- Institute of Analytical Chemistry, Johannes Kepler University Linz, Linz, Austria
| | - Michael Grabmann
- Institute of Polymeric Materials and Testing, Johannes Kepler University Linz, Linz, Austria
| | - Martin Muik
- Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria
| | | | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria
| | - Gernot Wallner
- Institute of Polymeric Materials and Testing, Johannes Kepler University Linz, Linz, Austria
| | - Wolfgang Buchberger
- Institute of Analytical Chemistry, Johannes Kepler University Linz, Linz, Austria
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35
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Abstract
A primary Ca2+ entry pathway in non-excitable cells is established by the Ca2+ release-activated Ca2+ channels. Their two limiting molecular components include the Ca2+-sensor protein STIM1 located in the endoplasmic reticulum and the Orai channel in the plasma membrane. STIM1 senses the luminal Ca2+ content, and store depletion induces its oligomerization into puncta-like structures, thereby triggering coupling to as well as activation of Orai channels. A C-terminal STIM1 domain is assumed to couple to both C- and N-terminal, cytosolic strands of Orai, accomplishing gating of the channel. Here we highlight the inter- and intramolecular steps of the STIM1-Orai signaling cascade together with critical sites of the pore structure that accomplishes Ca2+ permeation.
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Affiliation(s)
- Marc Fahrner
- Institute of Biophysics, Johannes Kepler University Linz, 4020, Linz, Austria.
| | - Rainer Schindl
- Institute of Biophysics, Johannes Kepler University Linz, 4020, Linz, Austria
| | - Martin Muik
- Institute of Biophysics, Johannes Kepler University Linz, 4020, Linz, Austria
| | - Isabella Derler
- Institute of Biophysics, Johannes Kepler University Linz, 4020, Linz, Austria
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, 4020, Linz, Austria.
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36
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Poteser M, Leitinger G, Pritz E, Platzer D, Frischauf I, Romanin C, Groschner K. Live-cell imaging of ER-PM contact architecture by a novel TIRFM approach reveals extension of junctions in response to store-operated Ca 2+-entry. Sci Rep 2016; 6:35656. [PMID: 27759093 PMCID: PMC5069484 DOI: 10.1038/srep35656] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 09/29/2016] [Indexed: 01/16/2023] Open
Abstract
Nanometer-spaced appositions between endoplasmic reticulum and plasma membrane (ER-PM junctions) stabilized by membrane-joining protein complexes are critically involved in cellular Ca2+-handling and lipid trafficking. ER-PM junctional architecture and plasticity associated with inter-membrane communication are as yet barely understood. Here, we introduce a method to precisely characterize ER-PM junction morphology and dynamics with high temporal resolution and minimal disturbance of junctional intermembrane communication. We show that expression of soluble cytosolic fluorophores in combination with TIRFM enables to delineate ER and PM distance in the range of 10-150 nm. Live-cell imaging of sub-plasmalemmal structures in RBL-2H3 mast cells by this method, designated as fluorescence density mapping (FDM), revealed profound dynamics of ER-PM contact sites in response to store-depletion. We report the existence of a Ca2+-dependent process that expands the junctional ER to enlarge its contact surface with the PM, thereby promoting and stabilizing STIM1-Orai1 competent ER-PM junctions.
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Affiliation(s)
- Michael Poteser
- Institute of Biophysics, Medical University of Graz, Harrachgasse 21/4, 8010 Graz, Austria
| | - Gerd Leitinger
- Institute of Cell Biology, Histology and Embryology Research Unit "Electron Microscopic Techniques", Medical University of Graz, Harrachgasse 21/7, 8010 Graz, Austria
| | - Elisabeth Pritz
- Institute of Cell Biology, Histology and Embryology Research Unit "Electron Microscopic Techniques", Medical University of Graz, Harrachgasse 21/7, 8010 Graz, Austria
| | - Dieter Platzer
- Institute of Biophysics, Medical University of Graz, Harrachgasse 21/4, 8010 Graz, Austria
| | - Irene Frischauf
- Institute of Biophysics, Johannes Kepler University of Linz, Austria, Gruberstrasse 40, 4020 Linz, Austria
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University of Linz, Austria, Gruberstrasse 40, 4020 Linz, Austria
| | - Klaus Groschner
- Institute of Biophysics, Medical University of Graz, Harrachgasse 21/4, 8010 Graz, Austria
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37
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Fahrner M, Stadlbauer M, Muik M, Romanin C. Impact of STIM1 R304W Mutant on Intra- and Intermolecular Cytosolic Coiled-Coil Interactions. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.1448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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38
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Abstract
Ca2+ entry into the cell via store-operated Ca2+ release-activated Ca2+ (CRAC) channels triggers diverse signaling cascades that affect cellular processes like cell growth, gene regulation, secretion, and cell death. These store-operated Ca2+ channels open after depletion of intracellular Ca2+ stores, and their main features are fully reconstituted by the two molecular key players: the stromal interaction molecule (STIM) and Orai. STIM represents an endoplasmic reticulum-located Ca2+ sensor, while Orai forms a highly Ca2+-selective ion channel in the plasma membrane. Functional as well as mutagenesis studies together with structural insights about STIM and Orai proteins provide a molecular picture of the interplay of these two key players in the CRAC signaling cascade. This review focuses on the main experimental advances in the understanding of the STIM1-Orai choreography, thereby establishing a portrait of key mechanistic steps in the CRAC channel signaling cascade. The focus is on the activation of the STIM proteins, the subsequent coupling of STIM1 to Orai1, and the consequent structural rearrangements that gate the Orai channels into the open state to allow Ca2+ permeation into the cell.
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Affiliation(s)
- Isabella Derler
- Institute of Biophysics, Johannes Kepler University of Linz, Linz, Austria; and
| | - Isaac Jardin
- Department of Physiology, University of Extremadura, Cáceres, Spain
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University of Linz, Linz, Austria; and
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39
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Derler I, Jardin I, Stathopulos PB, Muik M, Fahrner M, Zayats V, Pandey SK, Poteser M, Lackner B, Absolonova M, Schindl R, Groschner K, Ettrich R, Ikura M, Romanin C. Cholesterol modulates Orai1 channel function. Sci Signal 2016; 9:ra10. [PMID: 26814231 DOI: 10.1126/scisignal.aad7808] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
STIM1 (stromal interaction molecule 1) and Orai proteins are the essential components of Ca(2+) release-activated Ca(2+) (CRAC) channels. We focused on the role of cholesterol in the regulation of STIM1-mediated Orai1 currents. Chemically induced cholesterol depletion enhanced store-operated Ca(2+) entry (SOCE) and Orai1 currents. Furthermore, cholesterol depletion in mucosal-type mast cells augmented endogenous CRAC currents, which were associated with increased degranulation, a process that requires calcium influx. Single point mutations in the Orai1 amino terminus that would be expected to abolish cholesterol binding enhanced SOCE to a similar extent as did cholesterol depletion. The increase in Orai1 activity in cells expressing these cholesterol-binding-deficient mutants occurred without affecting the amount in the plasma membrane or the coupling of STIM1 to Orai1. We detected cholesterol binding to an Orai1 amino-terminal fragment in vitro and to full-length Orai1 in cells. Thus, our data showed that Orai1 senses the amount of cholesterol in the plasma membrane and that the interaction of Orai1 with cholesterol inhibits its activity, thereby limiting SOCE.
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Affiliation(s)
- Isabella Derler
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria.
| | - Isaac Jardin
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Peter B Stathopulos
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Martin Muik
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Marc Fahrner
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Vasilina Zayats
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, CZ-373 33 Nové Hrady, Czech Republic
| | - Saurabh K Pandey
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, CZ-373 33 Nové Hrady, Czech Republic
| | - Michael Poteser
- Institute of Biophysics, Medical University of Graz, Harrachgasse 21/4, 8010 Graz, Austria
| | - Barbara Lackner
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Marketa Absolonova
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Rainer Schindl
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Klaus Groschner
- Institute of Biophysics, Medical University of Graz, Harrachgasse 21/4, 8010 Graz, Austria
| | - Rüdiger Ettrich
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, CZ-373 33 Nové Hrady, Czech Republic
| | - Mitsu Ikura
- Princess Margaret Cancer Centre and Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 1L7, Canada
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria.
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40
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Abstract
Ca(2+) influx via store-operated Ca(2+) release activated Ca(2+) (CRAC) channels represents a main signalling pathway for a variety of cell functions, including T-cell activation as well as mast-cell degranulation. Depletion of [Ca(2+)]ER results in activation of Ca(2+) channels within the plasmamembrane that mediate sustained Ca(2+) influx which is required for refilling Ca(2+) stores and down-stream Ca(2+) signalling. The CRAC channel is the best characterized store-operated channel (SOC) with well-defined electrophysiological properties. In recent years, the molecular components of the CRAC channel have been defined. The ER - located Ca(2+)-sensor, STIM1 and the Ca(2+)-selective ion pore, Orai1 in the membrane are sufficient to fully reconstitute CRAC currents. Stromal interaction molecule (STIM) 1 is localized in the ER, senses [Ca(2+)]ER and activates the CRAC channel upon store depletion by direct binding to Orai1 in the plasmamembrane. The identification of STIM1 and Orai1 and recently the structural resolution of both proteins by X-ray crystallography and nuclear magnetic resonance substantiated many findings from structure-function studies which has substantially improved the understanding of CRAC channel activation. Within this review, we summarize the functional and structural mechanisms of CRAC channel regulation, present a detailed overview of the STIM1/Orai1 signalling pathway where we focus on the critical domains mediating interactions and on the ion permeation pathway. We portray a mechanistic view of the steps in the dynamics of CRAC channel signalling ranging from STIM1 oligomerization over STIM1-Orai1 coupling to CRAC channel activation and permeation.
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Affiliation(s)
| | - Marc Fahrner
- Institute of Biophysics, University of Linz, Linz, Austria
| | - Isaac Jardín
- Department of Physiology, University of Extremadura, Cáceres, Spain
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41
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Frischauf I, Zayats V, Deix M, Hochreiter A, Jardin I, Muik M, Lackner B, Svobodová B, Pammer T, Litviňuková M, Sridhar AA, Derler I, Bogeski I, Romanin C, Ettrich RH, Schindl R. A calcium-accumulating region, CAR, in the channel Orai1 enhances Ca(2+) permeation and SOCE-induced gene transcription. Sci Signal 2015; 8:ra131. [PMID: 26696631 DOI: 10.1126/scisignal.aab1901] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The Ca(2+) release-activated Ca(2+) channel mediates Ca(2+) influx in a plethora of cell types, thereby controlling diverse cellular functions. The channel complex is composed of stromal interaction molecule 1 (STIM1), an endoplasmic reticulum Ca(2+)-sensing protein, and Orai1, a plasma membrane Ca(2+) channel. Channels composed of STIM1 and Orai1 mediate Ca(2+) influx even at low extracellular Ca(2+) concentrations. We investigated whether the activity of Orai1 adapted to different environmental Ca(2+) concentrations. We used homology modeling and molecular dynamics simulations to predict the presence of an extracellular Ca(2+)-accumulating region (CAR) at the pore entrance of Orai1. Furthermore, simulations of Orai1 proteins with mutations in CAR, along with live-cell experiments, or simulations and electrophysiological recordings of the channel with transient, electrostatic loop3 interacting with loop1 (the site of CAR) determined that CAR enhanced Ca(2+) permeation most efficiently at low external Ca(2+) concentrations. Consistent with these results, cells expressing Orai1 CAR mutants exhibited impaired gene expression stimulated by the Ca(2+)-activated transcription factor nuclear factor of activated T cells (NFAT). We propose that the Orai1 channel architecture with a close proximity of CAR to the selectivity filter, which enables Ca(2+)-selective ion permeation, enhances the local extracellular Ca(2+) concentration to maintain Ca(2+)-dependent gene regulation even in environments with relatively low Ca(2+)concentrations.
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Affiliation(s)
- Irene Frischauf
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Vasilina Zayats
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, Zamek 136, CZ-373 33, Nove Hrady, Czech Republic.,Faculty of Sciences, University of South Bohemia, Zamek 136, CZ-373 33, Nove Hrady, Czech Republic
| | - Michael Deix
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Anna Hochreiter
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria.,Institute for Experimental and Clinical Cell Therapy, Paracelsus Medical University, A-5020 Salzburg, Austria
| | - Isaac Jardin
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Martin Muik
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Barbara Lackner
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Barbora Svobodová
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria.,Institute for Biophysics of Medical University Graz, A-8010, Graz, Austria
| | - Teresa Pammer
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Monika Litviňuková
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Amrutha Arumbakam Sridhar
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Isabella Derler
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Ivan Bogeski
- Department of Biophysics, School of Medicine, University of Saarland, D-66421 Homburg, Germany
| | - Christoph Romanin
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Rüdiger H Ettrich
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, Zamek 136, CZ-373 33, Nove Hrady, Czech Republic.,Faculty of Sciences, University of South Bohemia, Zamek 136, CZ-373 33, Nove Hrady, Czech Republic
| | - Rainer Schindl
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
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42
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Maus M, Jairaman A, Stathopulos PB, Muik M, Fahrner M, Weidinger C, Benson M, Fuchs S, Ehl S, Romanin C, Ikura M, Prakriya M, Feske S. Missense mutation in immunodeficient patients shows the multifunctional roles of coiled-coil domain 3 (CC3) in STIM1 activation. Proc Natl Acad Sci U S A 2015; 112:6206-11. [PMID: 25918394 PMCID: PMC4434767 DOI: 10.1073/pnas.1418852112] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Store-operated Ca(2+) entry (SOCE) is a universal Ca(2+) influx pathway that is important for the function of many cell types. SOCE occurs upon depletion of endoplasmic reticulum (ER) Ca(2+) stores and relies on a complex molecular interplay between the plasma membrane (PM) Ca(2+) channel ORAI1 and the ER Ca(2+) sensor stromal interaction molecule (STIM) 1. Patients with null mutations in ORAI1 or STIM1 genes present with severe combined immunodeficiency (SCID)-like disease. Here, we describe the molecular mechanisms by which a loss-of-function STIM1 mutation (R429C) in human patients abolishes SOCE. R429 is located in the third coiled-coil (CC3) domain of the cytoplasmic C terminus of STIM1. Mutation of R429 destabilizes the CC3 structure and alters the conformation of the STIM1 C terminus, thereby releasing a polybasic domain that promotes STIM1 recruitment to ER-PM junctions. However, the mutation also impairs cytoplasmic STIM1 oligomerization and abolishes STIM1-ORAI1 interactions. Thus, despite its constitutive localization at ER-PM junctions, mutant STIM1 fails to activate SOCE. Our results demonstrate multifunctional roles of the CC3 domain in regulating intra- and intermolecular STIM1 interactions that control (i) transition of STIM1 from a quiescent to an active conformational state, (ii) cytoplasmic STIM1 oligomerization, and (iii) STIM1-ORAI1 binding required for ORAI1 activation.
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Affiliation(s)
- Mate Maus
- Department of Pathology, New York University School of Medicine, New York, NY 10016
| | - Amit Jairaman
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | - Peter B Stathopulos
- Princess Margaret Cancer Centre and Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada, M5G 1L7; Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada, N6A 5C1
| | - Martin Muik
- Institute of Biophysics, Johannes Kepler University Linz, A-4020 Linz, Austria
| | - Marc Fahrner
- Institute of Biophysics, Johannes Kepler University Linz, A-4020 Linz, Austria
| | - Carl Weidinger
- Department of Pathology, New York University School of Medicine, New York, NY 10016
| | - Melina Benson
- Department of Pathology, New York University School of Medicine, New York, NY 10016
| | - Sebastian Fuchs
- Center for Chronic Immunodeficiency, University Medical Center, University of Freiburg, D-79106 Freiburg, Germany; Faculty of Biology, University of Freiburg, D-79104 Freiburg, Germany; and
| | - Stephan Ehl
- Center for Chronic Immunodeficiency, University Medical Center, University of Freiburg, D-79106 Freiburg, Germany; Center for Pediatrics and Adolescent Medicine, University Medical Center, University of Freiburg, D-79106 Freiburg, Germany
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, A-4020 Linz, Austria
| | - Mitsuhiko Ikura
- Princess Margaret Cancer Centre and Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada, M5G 1L7
| | - Murali Prakriya
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | - Stefan Feske
- Department of Pathology, New York University School of Medicine, New York, NY 10016;
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43
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Zhang X, Zhang W, González-Cobos JC, Jardin I, Romanin C, Matrougui K, Trebak M. Complex role of STIM1 in the activation of store-independent Orai1/3 channels. ACTA ACUST UNITED AC 2014; 143:345-59. [PMID: 24567509 PMCID: PMC3933941 DOI: 10.1085/jgp.201311084] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Orai proteins contribute to Ca(2+) entry into cells through both store-dependent, Ca(2+) release-activated Ca(2+) (CRAC) channels (Orai1) and store-independent, arachidonic acid (AA)-regulated Ca(2+) (ARC) and leukotriene C4 (LTC4)-regulated Ca(2+) (LRC) channels (Orai1/3 heteromultimers). Although activated by fundamentally different mechanisms, CRAC channels, like ARC and LRC channels, require stromal interacting molecule 1 (STIM1). The role of endoplasmic reticulum-resident STIM1 (ER-STIM1) in CRAC channel activation is widely accepted. Although ER-STIM1 is necessary and sufficient for LRC channel activation in vascular smooth muscle cells (VSMCs), the minor pool of STIM1 located at the plasma membrane (PM-STIM1) is necessary for ARC channel activation in HEK293 cells. To determine whether ARC and LRC conductances are mediated by the same or different populations of STIM1, Orai1, and Orai3 proteins, we used whole-cell and perforated patch-clamp recording to compare AA- and LTC4-activated currents in VSMCs and HEK293 cells. We found that both cell types show indistinguishable nonadditive LTC4- and AA-activated currents that require both Orai1 and Orai3, suggesting that both conductances are mediated by the same channel. Experiments using a nonmetabolizable form of AA or an inhibitor of 5-lipooxygenase suggested that ARC and LRC currents in both cell types could be activated by either LTC4 or AA, with LTC4 being more potent. Although PM-STIM1 was required for current activation by LTC4 and AA under whole-cell patch-clamp recordings in both cell types, ER-STIM1 was sufficient with perforated patch recordings. These results demonstrate that ARC and LRC currents are mediated by the same cellular populations of STIM1, Orai1, and Orai3, and suggest a complex role for both ER-STIM1 and PM-STIM1 in regulating these store-independent Orai1/3 channels.
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Affiliation(s)
- Xuexin Zhang
- Nanobioscience Constellation, State University of New York College of Nanoscale Science and Engineering, Albany, NY 12203
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44
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Fahrner M, Muik M, Schindl R, Butorac C, Stathopulos P, Zheng L, Jardin I, Ikura M, Romanin C. A coiled-coil clamp controls both conformation and clustering of stromal interaction molecule 1 (STIM1). J Biol Chem 2014; 289:33231-44. [PMID: 25342749 PMCID: PMC4246082 DOI: 10.1074/jbc.m114.610022] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Store-operated Ca2+ entry, essential for the adaptive immunity, is initiated by the endoplasmic reticulum (ER) Ca2+ sensor STIM1. Ca2+ entry occurs through the plasma membrane resident Ca2+ channel Orai1 that directly interacts with the C-terminal STIM1 domain, named SOAR/CAD. Depletion of the ER Ca2+ store controls this STIM1/Orai1 interaction via transition to an extended STIM1 C-terminal conformation, exposure of the SOAR/CAD domain, and STIM1/Orai1 co-clustering. Here we developed a novel approach termed FRET-derived Interaction in a Restricted Environment (FIRE) in an attempt to dissect the interplay of coiled-coil (CC) interactions in controlling STIM1 quiescent as well as active conformation and cluster formation. We present evidence of a sequential activation mechanism in the STIM1 cytosolic domains where the interaction between CC1 and CC3 segment regulates both SOAR/CAD exposure and CC3-mediated higher-order oligomerization as well as cluster formation. These dual levels of STIM1 auto-inhibition provide efficient control over the coupling to and activation of Orai1 channels.
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Affiliation(s)
- Marc Fahrner
- From the Life Science Center JKU, Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Martin Muik
- From the Life Science Center JKU, Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Rainer Schindl
- From the Life Science Center JKU, Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Carmen Butorac
- From the Life Science Center JKU, Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Peter Stathopulos
- Department of Physiology and Pharmacology, Western University, London, Ontario N6A 5C1, Canada, and
| | - Le Zheng
- Princess Margaret Cancer Centre and Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 1L7, Canada
| | - Isaac Jardin
- From the Life Science Center JKU, Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Mitsuhiko Ikura
- Princess Margaret Cancer Centre and Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 1L7, Canada
| | - Christoph Romanin
- From the Life Science Center JKU, Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria,
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Stathopulos PB, Schindl R, Fahrner M, Zheng L, Gasmi-Seabrook GM, Muik M, Romanin C, Ikura M. STIM1/Orai1 coiled-coil interplay in the regulation of store-operated calcium entry. Nat Commun 2014; 4:2963. [PMID: 24351972 PMCID: PMC3927877 DOI: 10.1038/ncomms3963] [Citation(s) in RCA: 166] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 11/20/2013] [Indexed: 12/11/2022] Open
Abstract
Orai1 calcium channels in the plasma membrane are activated by stromal interaction molecule-1 (STIM1), an endoplasmic reticulum calcium sensor, to mediate store-operated calcium entry (SOCE). The cytosolic region of STIM1 contains a long putative coiled-coil (CC)1 segment and shorter CC2 and CC3 domains. Here we present solution nuclear magnetic resonance structures of a trypsin-resistant CC1–CC2 fragment in the apo and Orai1-bound states. Each CC1–CC2 subunit forms a U-shaped structure that homodimerizes through antiparallel interactions between equivalent α-helices. The CC2:CC2′ helix pair clamps two identical acidic Orai1 C-terminal helices at opposite ends of a hydrophobic/basic STIM–Orai association pocket. STIM1 mutants disrupting CC1:CC1′ interactions attenuate, while variants promoting CC1 stability spontaneously activate Orai1 currents. CC2 mutations cause remarkable variability in Orai1 activation because of a dual function in binding Orai1 and autoinhibiting STIM1 oligomerization via interactions with CC3. We conclude that SOCE is activated through dynamic interplay between STIM1 and Orai1 helices. When endoplasmic reticulum calcium levels are low, STIM1 binds to and opens Orai1 channels in the plasma membrane to replenish calcium stores. Stathopulos et al. present solution structures of the STIM1 coiled-coil domain in the presence and absence of Orai1, revealing the structural basis for this interaction.
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Affiliation(s)
- Peter B Stathopulos
- University Health Network and Department of Medical Biophysics, Campbell Family Cancer Research Institute, Ontario Cancer Institute, University of Toronto, Room 4-804, MaRS TMDT, 101 College Street, Toronto, Ontario, Canada M5G 1L7
| | - Rainer Schindl
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Marc Fahrner
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Le Zheng
- University Health Network and Department of Medical Biophysics, Campbell Family Cancer Research Institute, Ontario Cancer Institute, University of Toronto, Room 4-804, MaRS TMDT, 101 College Street, Toronto, Ontario, Canada M5G 1L7
| | - Geneviève M Gasmi-Seabrook
- University Health Network and Department of Medical Biophysics, Campbell Family Cancer Research Institute, Ontario Cancer Institute, University of Toronto, Room 4-804, MaRS TMDT, 101 College Street, Toronto, Ontario, Canada M5G 1L7
| | - Martin Muik
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Mitsuhiko Ikura
- University Health Network and Department of Medical Biophysics, Campbell Family Cancer Research Institute, Ontario Cancer Institute, University of Toronto, Room 4-804, MaRS TMDT, 101 College Street, Toronto, Ontario, Canada M5G 1L7
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Zhang X, Zhang W, González-Cobos JC, Jardin I, Romanin C, Matrougui K, Trebak M. Complex role of STIM1 in the activation of store-independent Orai1/3 channels. J Biophys Biochem Cytol 2014. [DOI: 10.1083/jcb.2045oia34] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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47
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Derler I, Lackner B, Fahrner M, Stathopulos PB, Jardin I, Bergsmann J, Ikura M, Romanin C. Cholesterol Regulates Orai1 Function. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.1834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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48
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Schindl R, Frischauf I, Zayats V, Svobodova B, Deix M, Muik M, Hochreiter A, Ettrich R, Romanin C. Novel Trans-Membrane Mutation Switches Orai1 to a Constitutively Active and Ca2+ Selective Channel. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.1828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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49
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König S, Browne S, Doleschal B, Schernthaner M, Poteser M, Mächler H, Wittchow E, Braune M, Muik M, Romanin C, Groschner K. Inhibition of Orai1-mediated Ca(2+) entry is a key mechanism of the antiproliferative action of sirolimus in human arterial smooth muscle. Am J Physiol Heart Circ Physiol 2013; 305:H1646-57. [PMID: 24056904 DOI: 10.1152/ajpheart.00365.2013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Sirolimus (rapamycin) is used in drug-eluting stent strategies and proved clearly superior in this application compared with other immunomodulators such as pimecrolimus. The molecular basis of this action of sirolimus in the vascular system is still incompletely understood. Measurements of cell proliferation in human coronary artery smooth muscle cells (hCASM) demonstrated a higher antiproliferative activity of sirolimus compared with pimecrolimus. Although sirolimus lacks inhibitory effects on calcineurin, nuclear factor of activated T-cell activation in hCASM was suppressed to a similar extent by both drugs at 10 μM. Sirolimus, but not pimecrolimus, inhibited agonist-induced and store-operated Ca(2+) entry as well as cAMP response element binding protein (CREB) phosphorylation in human arterial smooth muscle, suggesting the existence of an as-yet unrecognized inhibitory effect of sirolimus on Ca(2+) signaling and Ca(2+)-dependent gene transcription. Electrophysiological experiments revealed that only sirolimus but not pimecrolimus significantly blocked the classical stromal interaction molecule/Orai-mediated, store-operated Ca(2+) current reconstituted in human embryonic kidney cells (HEK293). A link between Orai function and proliferation was confirmed by dominant-negative knockout of Orai in hCASM. Analysis of the effects of sirolimus on cell proliferation and CREB activation in an in vitro model of arterial intervention using human aorta corroborated the ability of sirolimus to suppress stent implantation-induced CREB activation in human arteries. We suggest inhibition of store-operated Ca(2+) entry based on Orai channels and the resulting suppression of Ca(2+) transcription coupling as a key mechanism underlying the antiproliferative activity of sirolimus in human arteries. This mechanism of action is specific for sirolimus and not a general feature of drugs interacting with FK506-binding proteins.
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Affiliation(s)
- Sarah König
- Institute of Biophysics, Medical University of Graz, Graz, Austria
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50
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Romanin C. In this issue of Channels: Special issue on STIM and Orai. Channels (Austin) 2013; 7:329. [PMID: 24212114 PMCID: PMC3893731 DOI: 10.4161/chan.27137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Christoph Romanin
- Institute of Biophysics; Johannes Kepler University Linz; Linz, Austria
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