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Lolicato F, Steringer JP, Saleppico R, Beyer D, Fernandez-Sobaberas J, Unger S, Klein S, Riegerová P, Wegehingel S, Müller HM, Schmitt XJ, Kaptan S, Freund C, Hof M, Šachl R, Chlanda P, Vattulainen I, Nickel W. Disulfide bridge-dependent dimerization triggers FGF2 membrane translocation into the extracellular space. eLife 2024; 12:RP88579. [PMID: 38252473 PMCID: PMC10945597 DOI: 10.7554/elife.88579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2024] Open
Abstract
Fibroblast growth factor 2 (FGF2) exits cells by direct translocation across the plasma membrane, a type I pathway of unconventional protein secretion. This process is initiated by phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2)-dependent formation of highly dynamic FGF2 oligomers at the inner plasma membrane leaflet, inducing the formation of lipidic membrane pores. Cell surface heparan sulfate chains linked to glypican-1 (GPC1) capture FGF2 at the outer plasma membrane leaflet, completing FGF2 membrane translocation into the extracellular space. While the basic steps of this pathway are well understood, the molecular mechanism by which FGF2 oligomerizes on membrane surfaces remains unclear. In the current study, we demonstrate the initial step of this process to depend on C95-C95 disulfide-bridge-mediated FGF2 dimerization on membrane surfaces, producing the building blocks for higher FGF2 oligomers that drive the formation of membrane pores. We find FGF2 with a C95A substitution to be defective in oligomerization, pore formation, and membrane translocation. Consistently, we demonstrate a C95A variant of FGF2 to be characterized by a severe secretion phenotype. By contrast, while also important for efficient FGF2 secretion from cells, a second cysteine residue on the molecular surface of FGF2 (C77) is not involved in FGF2 oligomerization. Rather, we find C77 to be part of the interaction interface through which FGF2 binds to the α1 subunit of the Na,K-ATPase, the landing platform for FGF2 at the inner plasma membrane leaflet. Using cross-linking mass spectrometry, atomistic molecular dynamics simulations combined with a machine learning analysis and cryo-electron tomography, we propose a mechanism by which disulfide-bridged FGF2 dimers bind with high avidity to PI(4,5)P2 on membrane surfaces. We further propose a tight coupling between FGF2 secretion and the formation of ternary signaling complexes on cell surfaces, hypothesizing that C95-C95-bridged FGF2 dimers are functioning as the molecular units triggering autocrine and paracrine FGF2 signaling.
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Affiliation(s)
- Fabio Lolicato
- Heidelberg University Biochemistry CenterHeidelbergGermany
- Department of Physics, University of HelsinkiHelsinkiFinland
| | | | | | - Daniel Beyer
- Heidelberg University Biochemistry CenterHeidelbergGermany
| | | | | | - Steffen Klein
- Schaller Research Group, Department of Infectious Diseases-Virology, Heidelberg University HospitalHeidelbergGermany
| | - Petra Riegerová
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of SciencesPragueCzech Republic
| | | | | | - Xiao J Schmitt
- Institute for Chemistry and Biochemistry, Freie Universität BerlinBerlinGermany
| | - Shreyas Kaptan
- Department of Physics, University of HelsinkiHelsinkiFinland
| | - Christian Freund
- Institute for Chemistry and Biochemistry, Freie Universität BerlinBerlinGermany
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of SciencesPragueCzech Republic
| | - Radek Šachl
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of SciencesPragueCzech Republic
| | - Petr Chlanda
- Schaller Research Group, Department of Infectious Diseases-Virology, Heidelberg University HospitalHeidelbergGermany
| | | | - Walter Nickel
- Heidelberg University Biochemistry CenterHeidelbergGermany
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2
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Dimou E, Katsinelos T, Meisl G, Tuck BJ, Keeling S, Smith AE, Hidari E, Lam JYL, Burke M, Lövestam S, Ranasinghe RT, McEwan WA, Klenerman D. Super-resolution imaging unveils the self-replication of tau aggregates upon seeding. Cell Rep 2023; 42:112725. [PMID: 37393617 PMCID: PMC7614924 DOI: 10.1016/j.celrep.2023.112725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 04/03/2023] [Accepted: 06/14/2023] [Indexed: 07/04/2023] Open
Abstract
Tau is a soluble protein interacting with tubulin to stabilize microtubules. However, under pathological conditions, it becomes hyperphosphorylated and aggregates, a process that can be induced by treating cells with exogenously added tau fibrils. Here, we employ single-molecule localization microscopy to resolve the aggregate species formed in early stages of seeded tau aggregation. We report that entry of sufficient tau assemblies into the cytosol induces the self-replication of small tau aggregates, with a doubling time of 5 h inside HEK cells and 1 day in murine primary neurons, which then grow into fibrils. Seeding occurs in the vicinity of the microtubule cytoskeleton, is accelerated by the proteasome, and results in release of small assemblies into the media. In the absence of seeding, cells still spontaneously form small aggregates at lower levels. Overall, our work provides a quantitative picture of the early stages of templated seeded tau aggregation in cells.
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Affiliation(s)
- Eleni Dimou
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK; UK Dementia Research Institute at University of Cambridge, Department of Clinical Neurosciences, Hills Road, Cambridge CB2 0AH, UK.
| | - Taxiarchis Katsinelos
- UK Dementia Research Institute at University of Cambridge, Department of Clinical Neurosciences, Hills Road, Cambridge CB2 0AH, UK; MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Georg Meisl
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Benjamin J Tuck
- UK Dementia Research Institute at University of Cambridge, Department of Clinical Neurosciences, Hills Road, Cambridge CB2 0AH, UK
| | - Sophie Keeling
- UK Dementia Research Institute at University of Cambridge, Department of Clinical Neurosciences, Hills Road, Cambridge CB2 0AH, UK
| | - Annabel E Smith
- UK Dementia Research Institute at University of Cambridge, Department of Clinical Neurosciences, Hills Road, Cambridge CB2 0AH, UK
| | - Eric Hidari
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK; UK Dementia Research Institute at University of Cambridge, Department of Clinical Neurosciences, Hills Road, Cambridge CB2 0AH, UK
| | - Jeff Y L Lam
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK; UK Dementia Research Institute at University of Cambridge, Department of Clinical Neurosciences, Hills Road, Cambridge CB2 0AH, UK
| | - Melanie Burke
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK; UK Dementia Research Institute at University of Cambridge, Department of Clinical Neurosciences, Hills Road, Cambridge CB2 0AH, UK
| | - Sofia Lövestam
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Rohan T Ranasinghe
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK; UK Dementia Research Institute at University of Cambridge, Department of Clinical Neurosciences, Hills Road, Cambridge CB2 0AH, UK
| | - William A McEwan
- UK Dementia Research Institute at University of Cambridge, Department of Clinical Neurosciences, Hills Road, Cambridge CB2 0AH, UK
| | - David Klenerman
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK; UK Dementia Research Institute at University of Cambridge, Department of Clinical Neurosciences, Hills Road, Cambridge CB2 0AH, UK.
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Panzi C, Surana S, De La-Rocque S, Moretto E, Lazo OM, Schiavo G. Botulinum neurotoxin A modulates the axonal release of pathological tau in hippocampal neurons. Toxicon 2023; 228:107110. [PMID: 37037273 PMCID: PMC10636589 DOI: 10.1016/j.toxicon.2023.107110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 04/03/2023] [Accepted: 04/03/2023] [Indexed: 04/12/2023]
Abstract
Pathological tau aggregates propagate across functionally connected neuronal networks in human neurodegenerative pathologies, such as Alzheimer's disease. However, the mechanism underlying this process is poorly understood. Several studies have showed that tau release is dependent on neuronal activity and that pathological tau is found in the extracellular space in free form, as well as in the lumen of extracellular vesicles. We recently showed that metabotropic glutamate receptor activity and SNAP25 integrity modulate the release of pathological tau from human and mouse synaptosomes. Here, we have leveraged botulinum neurotoxins (BoNTs), which impair neurotransmitter release by cleaving specific synaptic SNARE proteins, to dissect molecular mechanisms related to tau release at synapses. In particular, we have tested the effect of botulinum neurotoxin A (BoNT/A) on the synaptic release of tau in primary mouse neurons. Hippocampal neurons were grown in microfluidic chambers and transduced with lentiviruses expressing human tau (hTau). We found that neuronal stimulation significantly increases the release of mutant hTau, whereas wild-type hTau is unaffected. Importantly, BoNT/A blocks mutant hTau release, indicating that this process is controlled by SNAP25, a component of the SNARE complex, in intact neurons. These results suggest that BoNTs are potent tools to study the spreading of pathological proteins in neurodegenerative diseases and could play a central role in identifying novel molecular targets for the development of therapeutic interventions to treat tauopathies.
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Affiliation(s)
- Chiara Panzi
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK; UK Dementia Research Institute, University College London, London, UK; UCL Queen Square Motor Neuron Disease Centre, University College London, London, UK.
| | - Sunaina Surana
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK; UK Dementia Research Institute, University College London, London, UK; UCL Queen Square Motor Neuron Disease Centre, University College London, London, UK
| | - Samantha De La-Rocque
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK; UK Dementia Research Institute, University College London, London, UK
| | - Edoardo Moretto
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK; UK Dementia Research Institute, University College London, London, UK; Institute of Neuroscience, CNR, 20854, Vedano al Lambro, Italy
| | - Oscar Marcelo Lazo
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK; UK Dementia Research Institute, University College London, London, UK; UCL Queen Square Motor Neuron Disease Centre, University College London, London, UK
| | - Giampietro Schiavo
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK; UK Dementia Research Institute, University College London, London, UK; UCL Queen Square Motor Neuron Disease Centre, University College London, London, UK.
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Remtulla AAN, Huber RJ. The conserved cellular roles of CLN proteins: Novel insights from Dictyostelium discoideum. Eur J Cell Biol 2023; 102:151305. [PMID: 36917916 DOI: 10.1016/j.ejcb.2023.151305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/15/2023] [Accepted: 03/07/2023] [Indexed: 03/14/2023] Open
Abstract
The neuronal ceroid lipofuscinoses (NCLs), collectively referred to as Batten disease, are a group of fatal neurodegenerative disorders that primarily affect children. The etiology of Batten disease is linked to mutations in 13 genes that encode distinct CLN proteins, whose functions have yet to be fully elucidated. The social amoeba Dictyostelium discoideum has been adopted as an efficient and powerful model system for studying the diverse cellular roles of CLN proteins. The genome of D. discoideum encodes several homologs of human CLN proteins, and a growing body of literature supports the conserved roles and networking of CLN proteins in D. discoideum and humans. In humans, CLN proteins have diverse cellular roles related to autophagy, signal transduction, lipid homeostasis, lysosomal ion homeostasis, and intracellular trafficking. Recent work also indicates that CLN proteins play an important role in protein secretion. Remarkably, many of these findings have found parallels in studies with D. discoideum. Accordingly, this review will highlight the translatable value of novel work with D. discoideum in the field of NCL research and propose further avenues of research using this biomedical model organism for studying the NCLs.
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Affiliation(s)
- Adam A N Remtulla
- Environmental and Life Sciences Graduate Program, Trent University, Peterborough, Ontario, Canada
| | - Robert J Huber
- Environmental and Life Sciences Graduate Program, Trent University, Peterborough, Ontario, Canada; Department of Biology, Trent University, Peterborough, Ontario, Canada.
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Jacopo M. Unconventional protein secretion (UPS): role in important diseases. MOLECULAR BIOMEDICINE 2023; 4:2. [PMID: 36622461 PMCID: PMC9827022 DOI: 10.1186/s43556-022-00113-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 12/19/2022] [Indexed: 01/10/2023] Open
Abstract
Unconventional protein secretion (UPS) is the new secretion process discovered in liquid form over three decades ago. More recently, UPS has been shown to operate also in solid forms generated from four types of organelles: fractions of lysosomes and autophagy (APh) undergoing exocytosis; exosomes and ectosomes, with their extracellular vesicles (EVs). Recently many mechanisms and proteins of these solid forms have been shown to depend on UPS. An additional function of UPS is the regulation of diseases, often investigated separately from each other. In the present review, upon short presentation of UPS in healthy cells and organs, interest is focused on the mechanisms and development of diseases. The first reported are neurodegenerations, characterized by distinct properties. Additional diseases, including inflammasomes, inflammatory responses, glial effects and other diseases of various origin, are governed by proteins generated, directly or alternatively, by UPS. The diseases most intensely affected by UPS are various types of cancer, activated in most important processes: growth, proliferation and invasion, relapse, metastatic colonization, vascular leakiness, immunomodulation, chemoresistence. The therapy role of UPS diseases depends largely on exosomes. In addition to affecting neurodegenerative diseases, its special aim is the increased protection against cancer. Its immense relevance is due to intrinsic features, including low immunogenicity, biocompatibility, stability, and crossing of biological barriers. Exosomes, loaded with factors for pharmacological actions and target cell sensitivity, induce protection against various specific cancers. Further expansion of disease therapies is expected in the near future.
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Affiliation(s)
- Meldolesi Jacopo
- grid.18887.3e0000000417581884San Raffaele Institute, Vita-Salute San Raffaele University, Milan, Italy ,CNR Institute of Neuroscience at the Milano-Bicocca University, Milan, Italy
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Unconventional secretion mediated by direct protein self-translocation across the plasma membranes of mammalian cells. Trends Biochem Sci 2022; 47:699-709. [PMID: 35490075 DOI: 10.1016/j.tibs.2022.04.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 03/22/2022] [Accepted: 04/01/2022] [Indexed: 12/17/2022]
Abstract
In recent years, a surprisingly complex picture emerged about endoplasmic reticulum (ER)/Golgi-independent secretory pathways, and several routes have been discovered that differ with regard to their molecular mechanisms and machineries. Fibroblast growth factor 2 (FGF2) is secreted by a pathway of unconventional protein secretion (UPS) that is based on direct self-translocation across the plasma membrane. Building on previous research, a component of this process has been identified to be glypican-1 (GPC1), a GPI-anchored heparan sulfate proteoglycan located on cell surfaces. These findings not only shed light on the molecular mechanism underlying this process but also reveal an intimate relationship between FGF2 and GPC1 that might be of critical relevance for the prominent roles they both have in tumor progression and metastasis.
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Zhang Y, Qian L, Kuang Y, Liu J, Wang D, Xie W, Zhang L, Fu L. An adeno-associated virus-mediated immunotherapy for Alzheimer’s disease. Mol Immunol 2022; 144:26-34. [DOI: 10.1016/j.molimm.2022.02.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Revised: 01/30/2022] [Accepted: 02/06/2022] [Indexed: 11/29/2022]
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Filaquier A, Marin P, Parmentier ML, Villeneuve J. Roads and hubs of unconventional protein secretion. Curr Opin Cell Biol 2022; 75:102072. [PMID: 35305454 DOI: 10.1016/j.ceb.2022.02.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 02/07/2022] [Accepted: 02/14/2022] [Indexed: 12/11/2022]
Abstract
In eukaryotes, there is now compelling evidence that in addition to the conventional endoplasmic reticulum-Golgi secretory pathway, there are additional routes for the export of cytoplasmic proteins with a critical role in numerous physio-pathological conditions. These alternative secretory pathways or unconventional protein secretion (UPS) start now to be molecularly dissected, and while UPS landscape appears to be governed by a striking diversity and heterogeneity of mechanisms, common principles are emerging. We review here the role of key molecular determinants as well as the role of central hubs for UPS, highlighting the plasticity and dynamic properties of membrane-bound compartments. We also describe recent findings that position UPS as an integral component of adaptive responses to cope with particular cellular needs and stresses.
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Affiliation(s)
- Aurore Filaquier
- Institute of Functional Genomics, University of Montpellier, CNRS, INSERM, Montpellier, France
| | - Philippe Marin
- Institute of Functional Genomics, University of Montpellier, CNRS, INSERM, Montpellier, France
| | - Marie-Laure Parmentier
- Institute of Functional Genomics, University of Montpellier, CNRS, INSERM, Montpellier, France
| | - Julien Villeneuve
- Institute of Functional Genomics, University of Montpellier, CNRS, INSERM, Montpellier, France.
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Membrane interaction and disulphide-bridge formation in the unconventional secretion of Tau. Biosci Rep 2021; 41:229358. [PMID: 34308969 PMCID: PMC8350431 DOI: 10.1042/bsr20210148] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 07/04/2021] [Accepted: 07/21/2021] [Indexed: 11/17/2022] Open
Abstract
Misfolded, pathological tau protein propagates from cell to cell causing neuronal degeneration in Alzheimer's disease and other tauopathies. The molecular mechanisms of this process have remained elusive. Unconventional secretion of tau takes place via several different routes, including direct penetration through the plasma membrane. Here, we show that tau secretion requires membrane interaction via disulphide bridge formation. Mutating residues that reduce tau interaction with membranes or formation of disulphide bridges decrease both tau secretion from cells, and penetration through artificial lipid membranes. Our results demonstrate that tau is indeed able to penetrate protein-free membranes in a process independent of active cellular processes and that both membrane interaction and disulphide bridge formation are needed for this process. QUARK-based de novo modelling of the second and third microtubule-binding repeat domains (MTBDs), in which the two cysteine residues of 4R isoforms of tau are located, supports the concept that this region of tau could form transient amphipathic helices for membrane interaction.
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