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Pipercevic J, Kohl B, Gerasimaite R, Comte-Miserez V, Hostachy S, Müntener T, Agustoni E, Jessen HJ, Fiedler D, Mayer A, Hiller S. Inositol pyrophosphates activate the vacuolar transport chaperone complex in yeast by disrupting a homotypic SPX domain interaction. Nat Commun 2023; 14:2645. [PMID: 37156835 PMCID: PMC10167327 DOI: 10.1038/s41467-023-38315-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Accepted: 04/25/2023] [Indexed: 05/10/2023] Open
Abstract
Many proteins involved in eukaryotic phosphate homeostasis are regulated by SPX domains. In yeast, the vacuolar transporter chaperone (VTC) complex contains two such domains, but mechanistic details of its regulation are not well understood. Here, we show at the atomic level how inositol pyrophosphates interact with SPX domains of subunits Vtc2 and Vtc3 to control the activity of the VTC complex. Vtc2 inhibits the catalytically active VTC subunit Vtc4 by homotypic SPX-SPX interactions via the conserved helix α1 and the previously undescribed helix α7. Binding of inositol pyrophosphates to Vtc2 abrogates this interaction, thus activating the VTC complex. Accordingly, VTC activation is also achieved by site-specific point mutations that disrupt the SPX-SPX interface. Structural data suggest that ligand binding induces reorientation of helix α1 and exposes the modifiable helix α7, which might facilitate its post-translational modification in vivo. The variable composition of these regions within the SPX domain family might contribute to the diversified SPX functions in eukaryotic phosphate homeostasis.
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Affiliation(s)
- Joka Pipercevic
- Biozentrum, University of Basel, Spitalstrasse 41, 4056, Basel, Switzerland
| | - Bastian Kohl
- Biozentrum, University of Basel, Spitalstrasse 41, 4056, Basel, Switzerland
| | - Ruta Gerasimaite
- Department of Immunobiology, University of Lausanne, Chemin des Boveresses 155, CP51 1066, Epalinges, Switzerland
- Max-Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany
| | - Véronique Comte-Miserez
- Department of Immunobiology, University of Lausanne, Chemin des Boveresses 155, CP51 1066, Epalinges, Switzerland
| | - Sarah Hostachy
- Department of Chemical Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Straße 10, 13125, Berlin, Germany
| | - Thomas Müntener
- Biozentrum, University of Basel, Spitalstrasse 41, 4056, Basel, Switzerland
| | - Elia Agustoni
- Biozentrum, University of Basel, Spitalstrasse 41, 4056, Basel, Switzerland
| | - Henning Jacob Jessen
- Institute of Organic Chemistry, University of Freiburg, Albertstraße 21, 79104, Freiburg, Germany
| | - Dorothea Fiedler
- Department of Chemical Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Straße 10, 13125, Berlin, Germany
| | - Andreas Mayer
- Department of Immunobiology, University of Lausanne, Chemin des Boveresses 155, CP51 1066, Epalinges, Switzerland
| | - Sebastian Hiller
- Biozentrum, University of Basel, Spitalstrasse 41, 4056, Basel, Switzerland.
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D'Agostino M, Risselada HJ, Endter LJ, Comte-Miserez V, Mayer A. SNARE-mediated membrane fusion arrests at pore expansion to regulate the volume of an organelle. EMBO J 2018; 37:embj.201899193. [PMID: 30120144 DOI: 10.15252/embj.201899193] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [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: 02/07/2018] [Revised: 06/28/2018] [Accepted: 07/03/2018] [Indexed: 11/09/2022] Open
Abstract
Constitutive membrane fusion within eukaryotic cells is thought to be controlled at its initial steps, membrane tethering and SNARE complex assembly, and to rapidly proceed from there to full fusion. Although theory predicts that fusion pore expansion faces a major energy barrier and might hence be a rate-limiting and regulated step, corresponding states with non-expanding pores are difficult to assay and have remained elusive. Here, we show that vacuoles in living yeast are connected by a metastable, non-expanding, nanoscopic fusion pore. This is their default state, from which full fusion is regulated. Molecular dynamics simulations suggest that SNAREs and the SM protein-containing HOPS complex stabilize this pore against re-closure. Expansion of the nanoscopic pore to full fusion can thus be triggered by osmotic pressure gradients, providing a simple mechanism to rapidly adapt organelle volume to increases in its content. Metastable, nanoscopic fusion pores are then not only a transient intermediate but can be a long-lived, physiologically relevant and regulated state of SNARE-dependent membrane fusion.
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Affiliation(s)
- Massimo D'Agostino
- Département de Biochimie, Université de Lausanne, Epalinges, Switzerland
| | - Herre Jelger Risselada
- Department of Theoretical Physics, Georg-August University, Göttingen, Germany.,Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands
| | - Laura J Endter
- Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands
| | | | - Andreas Mayer
- Département de Biochimie, Université de Lausanne, Epalinges, Switzerland
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