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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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Nickle A, Ko S, Merrill AE. Fibroblast growth factor 2. Differentiation 2023:S0301-4681(23)00072-5. [PMID: 37858405 PMCID: PMC11009566 DOI: 10.1016/j.diff.2023.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 09/20/2023] [Accepted: 10/05/2023] [Indexed: 10/21/2023]
Abstract
Fibroblast Growth Factor 2 (FGF2), also known as basic fibroblast growth factor, is a potent stimulator of growth and differentiation in multiple tissues. Its discovery traces back over 50 years ago when it was first isolated from bovine pituitary extracts due to its ability to stimulate fibroblast proliferation. Subsequent studies investigating the genomic structure of FGF2 identified multiple protein isoforms, categorized as the low molecular weight and high molecular weight FGF2. These isoforms arise from alternative translation initiation events and exhibit unique molecular and cellular functions. In this concise review, we aim to provide an overview of what is currently known about the structure, expression, and functions of the FGF2 isoforms within the contexts of development, homeostasis, and disease.
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Affiliation(s)
- Audrey Nickle
- Center for Craniofacial Molecular Biology, Department of Biomedical Sciences, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, 90033, USA; Department of Biochemistry and Molecular Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA
| | - Sebastian Ko
- Center for Craniofacial Molecular Biology, Department of Biomedical Sciences, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, 90033, USA; Department of Biochemistry and Molecular Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA
| | - Amy E Merrill
- Center for Craniofacial Molecular Biology, Department of Biomedical Sciences, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, 90033, USA; Department of Biochemistry and Molecular Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA.
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3
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Lolicato F, Saleppico R, Griffo A, Meyer A, Scollo F, Pokrandt B, Müller HM, Ewers H, Hähl H, Fleury JB, Seemann R, Hof M, Brügger B, Jacobs K, Vattulainen I, Nickel W. Cholesterol promotes clustering of PI(4,5)P2 driving unconventional secretion of FGF2. J Biophys Biochem Cytol 2022; 221:213511. [PMID: 36173379 PMCID: PMC9526255 DOI: 10.1083/jcb.202106123] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 07/22/2022] [Accepted: 08/30/2022] [Indexed: 11/22/2022] Open
Abstract
FGF2 is a cell survival factor involved in tumor-induced angiogenesis that is secreted through an unconventional secretory pathway based upon direct protein translocation across the plasma membrane. Here, we demonstrate that both PI(4,5)P2-dependent FGF2 recruitment at the inner plasma membrane leaflet and FGF2 membrane translocation into the extracellular space are positively modulated by cholesterol in living cells. We further revealed cholesterol to enhance FGF2 binding to PI(4,5)P2-containing lipid bilayers. Based on extensive atomistic molecular dynamics (MD) simulations and membrane tension experiments, we proposed cholesterol to modulate FGF2 binding to PI(4,5)P2 by (i) increasing head group visibility of PI(4,5)P2 on the membrane surface, (ii) increasing avidity by cholesterol-induced clustering of PI(4,5)P2 molecules triggering FGF2 oligomerization, and (iii) increasing membrane tension facilitating the formation of lipidic membrane pores. Our findings have general implications for phosphoinositide-dependent protein recruitment to membranes and explain the highly selective targeting of FGF2 toward the plasma membrane, the subcellular site of FGF2 membrane translocation during unconventional secretion of FGF2.
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Affiliation(s)
- Fabio Lolicato
- Heidelberg University Biochemistry Center, Heidelberg, Germany.,Department of Physics, University of Helsinki, Helsinki, Finland
| | | | - Alessandra Griffo
- Department of Experimental Physics, Saarland University, Saarbrücken, Germany.,Biophysical Engineering Group, Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Annalena Meyer
- Heidelberg University Biochemistry Center, Heidelberg, Germany
| | - Federica Scollo
- Department of Biophysical Chemistry, J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Prague, Czech Republic
| | - Bianca Pokrandt
- Heidelberg University Biochemistry Center, Heidelberg, Germany
| | | | - Helge Ewers
- Institute for Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Hendrik Hähl
- Department of Experimental Physics, Saarland University, Saarbrücken, Germany
| | | | - Ralf Seemann
- Department of Experimental Physics, Saarland University, Saarbrücken, Germany
| | - Martin Hof
- Department of Biophysical Chemistry, J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Prague, Czech Republic
| | - Britta Brügger
- Heidelberg University Biochemistry Center, Heidelberg, Germany
| | - Karin Jacobs
- Department of Experimental Physics, Saarland University, Saarbrücken, Germany.,Max Planck School Matter to Life, Heidelberg, Germany
| | - Ilpo Vattulainen
- Department of Physics, University of Helsinki, Helsinki, Finland
| | - Walter Nickel
- Heidelberg University Biochemistry Center, Heidelberg, Germany
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4
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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: 9] [Impact Index Per Article: 4.5] [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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Lolicato F, Nickel W. A Role for Liquid-Ordered Plasma Membrane Nanodomains Coordinating the Unconventional Secretory Pathway of Fibroblast Growth Factor 2? Front Cell Dev Biol 2022; 10:864257. [PMID: 35433697 PMCID: PMC9010882 DOI: 10.3389/fcell.2022.864257] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 02/18/2022] [Indexed: 11/22/2022] Open
Abstract
Fibroblast growth factor 2 (FGF2) is a tumor cell survival factor that belongs to a subgroup of extracellular proteins lacking N-terminal signal peptides. Whereas this phenomenon was already recognized in the early 1990s, detailed insights into the molecular mechanisms underlying alternative pathways of protein secretion from eukaryotic cells were obtained only recently. Today, we know about a number of alternative secretory mechanisms, collectively termed unconventional protein secretion (UPS). FGF2 belongs to a subgroup of cargo proteins secreted by direct translocation across the plasma membrane. This feature has been classified as type I UPS and is shared with other unconventionally secreted proteins, such as HIV-Tat and Tau. FGF2 translocation across the membrane is initiated through sequential interactions with the Na,K-ATPase, Tec kinase, and phosphoinositide PI(4,5)P2 at the inner plasma membrane leaflet. Whereas the first two are auxiliary factors of this pathway, the interaction of FGF2 with PI(4,5)P2 triggers the core mechanism of FGF2 membrane translocation. It is based on a lipidic membrane pore that is formed by PI(4,5)P2-induced oligomerization of FGF2. Membrane-inserted FGF2 oligomers are recognized as translocation intermediates that are resolved at the outer plasma membrane leaflet by glypican-1, a heparan sulfate proteoglycan that captures and disassembles FGF2 oligomers on cell surfaces. Here, we discuss recent findings suggesting the molecular machinery mediating FGF2 membrane translocation to be highly organized in liquid-ordered plasma membrane nanodomains, the core process underlying this unusual pathway of protein secretion.
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Sparn C, Dimou E, Meyer A, Saleppico R, Wegehingel S, Gerstner M, Klaus S, Ewers H, Nickel W. Glypican-1 drives unconventional secretion of Fibroblast Growth Factor 2. eLife 2022; 11:75545. [PMID: 35348113 PMCID: PMC8986318 DOI: 10.7554/elife.75545] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Accepted: 03/24/2022] [Indexed: 11/13/2022] Open
Abstract
Fibroblast Growth Factor 2 (FGF2) is a tumor cell survival factor that is transported into the extracellular space by an unconventional secretory mechanism. Cell surface heparan sulfate proteoglycans are known to play an essential role in this process. Unexpectedly, we found that among the diverse sub-classes consisting of syndecans, perlecans, glypicans and others, Glypican-1 (GPC1) is the principle and rate-limiting factor that drives unconventional secretion of FGF2. By contrast, we demonstrate GPC1 to be dispensable for FGF2 signaling into cells. We provide first insights into the structural basis for GPC1-dependent FGF2 secretion, identifying disaccharides with N-linked sulfate groups to be enriched in the heparan sulfate chains of GPC1 to which FGF2 binds with high affinity. Our findings have broad implications for the role of GPC1 as a key molecule in tumor progression.
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Affiliation(s)
| | | | | | | | | | | | | | - Helge Ewers
- Institut für Chemie und Biochemie, Freie Universität Berlin
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7
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Complement-mediated release of fibroblast growth factor 2 from human RPE cells. Exp Eye Res 2021; 204:108471. [PMID: 33516764 DOI: 10.1016/j.exer.2021.108471] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2020] [Revised: 01/09/2021] [Accepted: 01/21/2021] [Indexed: 11/24/2022]
Abstract
PURPOSE Complement activation is associated with choroidal neovascularization (CNV) in age-related macular degeneration (AMD). Fibroblast growth factor 2 (FGF2) and membrane attack complex (MAC) are present in eyes of patients with CNV. Herein, we investigated the effect of complement activation on FGF2 release in human retinal pigment epithelial (RPE) cells. METHODS Cultured human RPE cells were primed with an anti-RPE antibody and then treated with C1q-depleted human serum in the presence or absence of Tec kinases inhibitor (LFM-A13). 38 cytokines/chemokines levels were measured by Luminex technology. Secretion of FGF2 and interleukin (IL)-6 was assessed by ELISA. Tec protein was measured by Western blot. mRNA expression of FGF2, chemokine (C-X-C motif) ligand 1 (CXCL-1), and family members of Tec kinases was evaluated by qPCR. Cell viability and MAC deposition were determined by WST-1 assay and flow cytometry, respectively. RESULTS Complement activation caused increased FGF2 and IL-6 release. FGF2 was released when C6-depleted human serum was reconstituted with C6. Anti-C5 antibody significantly attenuated complement-mediated FGF2 release, but not IL-6. FGF2 mRNA levels were not affected, while CXCL-1 mRNA levels were increased by complement activation. FGF2-containing extracellular vesicles were detected in response to complement challenge. Tec mRNA and protein were expressed in RPE cells. In the presence of LFM-A13, secretion of FGF2, but not IL-6, and MAC deposition were significantly decreased and cell viability was significantly increased in complement-treated cells when compared to controls. CONCLUSIONS Complement plays an important role to release FGF2 from RPE cells. Tec kinase is involved in MAC formation and complement-mediated FGF2 release. This information suggests a role for complement activation to mediate neovascularization in conditions such as AMD, and may elucidate potential therapeutic targets.
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8
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Šachl R, Čujová S, Singh V, Riegerová P, Kapusta P, Müller HM, Steringer JP, Hof M, Nickel W. Functional Assay to Correlate Protein Oligomerization States with Membrane Pore Formation. Anal Chem 2020; 92:14861-14866. [PMID: 33198473 DOI: 10.1021/acs.analchem.0c03276] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In-membrane oligomerization is decisive for the function (or dysfunction) of many proteins. Techniques were developed to characterize membrane-inserted oligomers and the hereby obtained oligomerization states were intuitively related to the function of these proteins. However, in many cases, it is unclear whether the obtained oligomerization states are functionally relevant or are merely the consequence of nonspecific aggregation. Using fibroblast growth factor 2 (FGF2) as a model system, we addressed this methodological challenge. FGF2 oligomerizes in a PI(4,5)P2-dependent manner at the inner plasma membrane leaflet. This process results in membrane insertion and the formation of a lipidic membrane pore, the key intermediate in unconventional secretion of FGF2. To tackle the problem of discriminating functional oligomers from irrelevant aggregates, we present a statistical single molecule and single vesicle assay determining the brightness of individually diffusing in-membrane oligomers and correlating their oligomerization state with membrane pore formation. Importantly, time-dependent membrane pore formation was analyzed with an ensemble of single vesicles providing detailed statistics. Our findings demonstrate that quantifying oligomeric states alone does not allow for a deep understanding of the structure-function relationship of membrane-inserted oligomers.
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Affiliation(s)
- Radek Šachl
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 3 182 23 Prague, Czech Republic
| | - Sabína Čujová
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 3 182 23 Prague, Czech Republic
| | - Vandana Singh
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 3 182 23 Prague, Czech Republic
| | - Petra Riegerová
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 3 182 23 Prague, Czech Republic
| | - Peter Kapusta
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 3 182 23 Prague, Czech Republic
| | - Hans-Michael Müller
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69 120 Heidelberg, Germany
| | - Julia P Steringer
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69 120 Heidelberg, Germany
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 3 182 23 Prague, Czech Republic
| | - Walter Nickel
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69 120 Heidelberg, Germany
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9
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Pallotta MT, Nickel W. FGF2 and IL-1β – explorers of unconventional secretory pathways at a glance. J Cell Sci 2020; 133:133/21/jcs250449. [DOI: 10.1242/jcs.250449] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
ABSTRACT
Fibroblast growth factor 2 (FGF2) and interleukin 1β (IL-1β) were among the earliest examples of a subclass of proteins with extracellular functions that were found to lack N-terminal secretory signal peptides and were shown to be secreted in an ER- and Golgi-independent manner. Many years later, a number of alternative secretory pathways have been discovered, processes collectively termed unconventional protein secretion (UPS). In the course of these studies, unconventional secretion of FGF2 and IL-1β were found to be based upon distinct pathways, mechanisms and molecular machineries. Following a concise introduction into various pathways mediating unconventional secretion and transcellular spreading of proteins, this Cell Science at a Glance poster article aims at a focused analysis of recent key discoveries providing unprecedented detail about the molecular mechanisms and machineries driving FGF2 and IL-1β secretion. These findings are also highly relevant for other unconventionally secreted cargoes that, like FGF2 and IL1β, exert fundamental biological functions in biomedically relevant processes, such as tumor-induced angiogenesis and inflammation.
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Affiliation(s)
| | - Walter Nickel
- Heidelberg University Biochemistry Center, Heidelberg 69120, Germany
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10
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Novák J, Vopálenský V, Pospíšek M, Vedeler A. Co-localization of Interleukin-1α and Annexin A2 at the plasma membrane in response to oxidative stress. Cytokine 2020; 133:155141. [PMID: 32615410 DOI: 10.1016/j.cyto.2020.155141] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 04/11/2020] [Accepted: 05/15/2020] [Indexed: 12/19/2022]
Abstract
Interleukin-1α (IL-1α) and Annexin A2 (AnxA2) are pleiotropic molecules with both intracellular and extracellular roles. They share several characteristics including unconventional secretion aided by S100 proteins, anchoring of the externalized proteins at the outer surface of the plasma membrane and response to oxidative stress. Although IL-1α and AnxA2 have been implicated in a variety of biological processes, including cancer, little is known about the mechanisms of their cellular release. In the present study, employing the non-cancerous breast epithelial MCF10A cells, we demonstrate that IL-1α and AnxA2 establish a close association in response to oxidative stress. Stress conditions lead to translocation of both proteins towards lamellipodia rich in vimentin and association of full-length IL-1α and Tyr23 phosphorylated AnxA2 with the plasma membrane at peripheral sites depleted of F-actin. Notably, membrane-associated IL-1α and AnxA2 preferentially localize to the outer edges of the MCF10A cell islands, suggesting that the two proteins participate in the communication of these epithelial cells with their neighboring cells. Similarly, in U2OS osteosarcoma cell line both endogenous IL-1α and transiently produced IL-1α/EGFP associate with the plasma membrane. While benign MFC10A cells present membrane-associated IL-1α and AnxA2 at the edges of their cell islands, the aggressive cancerous U2OS cells communicate in such manner also with distant cells.
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Affiliation(s)
- Josef Novák
- Department of Genetics and Microbiology, Faculty of Science, Charles University, Prague, Czech Republic; Department of Biomedicine, Faculty of Medicine, University of Bergen, Bergen, Norway.
| | - Václav Vopálenský
- Department of Genetics and Microbiology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Martin Pospíšek
- Department of Genetics and Microbiology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Anni Vedeler
- Department of Biomedicine, Faculty of Medicine, University of Bergen, Bergen, Norway
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Sluzalska KD, Slawski J, Sochacka M, Lampart A, Otlewski J, Zakrzewska M. Intracellular partners of fibroblast growth factors 1 and 2 - implications for functions. Cytokine Growth Factor Rev 2020; 57:93-111. [PMID: 32475760 DOI: 10.1016/j.cytogfr.2020.05.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 05/04/2020] [Accepted: 05/07/2020] [Indexed: 01/01/2023]
Abstract
Fibroblast growth factors 1 and 2 (FGF1 and FGF2) are mainly considered as ligands of surface receptors through which they regulate a broad spectrum of biological processes. They are secreted in non-canonical way and, unlike other growth factors, they are able to translocate from the endosome to the cell interior. These unique features, as well as the role of the intracellular pool of FGF1 and FGF2, are far from being fully understood. An increasing number of reports address this problem, focusing on the intracellular interactions of FGF1 and 2. Here, we summarize the current state of knowledge of the FGF1 and FGF2 binding partners inside the cell and the possible role of these interactions. The partner proteins are grouped according to their function, including proteins involved in secretion, cell signaling, nucleocytoplasmic transport, binding and processing of nucleic acids, ATP binding, and cytoskeleton assembly. An in-depth analysis of the network of these binding partners could indicate novel, non-classical functions of FGF1 and FGF2 and uncover an additional level of a fine control of the well-known FGF-regulated cellular processes.
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Affiliation(s)
- Katarzyna Dominika Sluzalska
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland
| | - Jakub Slawski
- Department of Biophysics, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland
| | - Martyna Sochacka
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland
| | - Agata Lampart
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland
| | - Jacek Otlewski
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland
| | - Malgorzata Zakrzewska
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland.
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Brunello CA, Merezhko M, Uronen RL, Huttunen HJ. Mechanisms of secretion and spreading of pathological tau protein. Cell Mol Life Sci 2020; 77:1721-1744. [PMID: 31667556 PMCID: PMC7190606 DOI: 10.1007/s00018-019-03349-1] [Citation(s) in RCA: 152] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 10/10/2019] [Accepted: 10/16/2019] [Indexed: 12/12/2022]
Abstract
Accumulation of misfolded and aggregated forms of tau protein in the brain is a neuropathological hallmark of tauopathies, such as Alzheimer's disease and frontotemporal lobar degeneration. Tau aggregates have the ability to transfer from one cell to another and to induce templated misfolding and aggregation of healthy tau molecules in previously healthy cells, thereby propagating tau pathology across different brain areas in a prion-like manner. The molecular mechanisms involved in cell-to-cell transfer of tau aggregates are diverse, not mutually exclusive and only partially understood. Intracellular accumulation of misfolded tau induces several mechanisms that aim to reduce the cellular burden of aggregated proteins and also promote secretion of tau aggregates. However, tau may also be released from cells physiologically unrelated to protein aggregation. Tau secretion involves multiple vesicular and non-vesicle-mediated pathways, including secretion directly through the plasma membrane. Consequently, extracellular tau can be found in various forms, both as a free protein and in vesicles, such as exosomes and ectosomes. Once in the extracellular space, tau aggregates can be internalized by neighboring cells, both neurons and glial cells, via endocytic, pinocytic and phagocytic mechanisms. Importantly, accumulating evidence suggests that prion-like propagation of misfolding protein pathology could provide a general mechanism for disease progression in tauopathies and other related neurodegenerative diseases. Here, we review the recent literature on cellular mechanisms involved in cell-to-cell transfer of tau, with a particular focus in tau secretion.
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Affiliation(s)
- Cecilia A Brunello
- Neuroscience Center, HiLIFE, University of Helsinki, P.O. Box 63, Haartmaninkatu 8, 00014, Helsinki, Finland
| | - Maria Merezhko
- Neuroscience Center, HiLIFE, University of Helsinki, P.O. Box 63, Haartmaninkatu 8, 00014, Helsinki, Finland
| | - Riikka-Liisa Uronen
- Neuroscience Center, HiLIFE, University of Helsinki, P.O. Box 63, Haartmaninkatu 8, 00014, Helsinki, Finland
| | - Henri J Huttunen
- Neuroscience Center, HiLIFE, University of Helsinki, P.O. Box 63, Haartmaninkatu 8, 00014, Helsinki, Finland.
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13
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Legrand C, Saleppico R, Sticht J, Lolicato F, Müller HM, Wegehingel S, Dimou E, Steringer JP, Ewers H, Vattulainen I, Freund C, Nickel W. The Na,K-ATPase acts upstream of phosphoinositide PI(4,5)P 2 facilitating unconventional secretion of Fibroblast Growth Factor 2. Commun Biol 2020; 3:141. [PMID: 32214225 PMCID: PMC7096399 DOI: 10.1038/s42003-020-0871-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 03/02/2020] [Indexed: 12/19/2022] Open
Abstract
FGF2 is a tumor cell survival factor that is exported from cells by an ER/Golgi-independent secretory pathway. This unconventional mechanism of protein secretion is based on direct translocation of FGF2 across the plasma membrane. The Na,K-ATPase has previously been shown to play a role in this process, however, the underlying mechanism has remained elusive. Here, we define structural elements that are critical for a direct physical interaction between FGF2 and the α1 subunit of the Na,K-ATPase. In intact cells, corresponding FGF2 mutant forms were impaired regarding both recruitment at the inner plasma membrane leaflet and secretion. Ouabain, a drug that inhibits both the Na,K-ATPase and FGF2 secretion, was found to impair the interaction of FGF2 with the Na,K-ATPase in cells. Our findings reveal the Na,K-ATPase as the initial recruitment factor for FGF2 at the inner plasma membrane leaflet being required for efficient membrane translocation of FGF2 to cell surfaces. Legrand et al. identify two lysine residues on molecular surface of Fibroblast Growth Factor 2 (FGF2) essential for its interaction with α1 subunit of the Na,K-ATPase. They further conclude that this interaction precedes interaction of the FGF2 with PI(4,5)P2 and facilitates its unconventional secretion across the membrane, which is impaired by Ouabain, an Na,K-ATPase inhibitor.
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Affiliation(s)
- Cyril Legrand
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120, Heidelberg, Germany
| | - Roberto Saleppico
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120, Heidelberg, Germany
| | - Jana Sticht
- Institute for Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195, Berlin, Germany.,Core Facility BioSupraMol, Freie Universität Berlin, Berlin, Germany
| | - Fabio Lolicato
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120, Heidelberg, Germany.,Department of Physics, University of Helsinki, FL-00014, Helsinki, Finland.,Computational Physics Laboratory, Tampere University, Fl-33100, Tampere, Finland
| | - Hans-Michael Müller
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120, Heidelberg, Germany
| | - Sabine Wegehingel
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120, Heidelberg, Germany
| | - Eleni Dimou
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120, Heidelberg, Germany
| | - Julia P Steringer
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120, Heidelberg, Germany
| | - Helge Ewers
- Institute for Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195, Berlin, Germany
| | - Ilpo Vattulainen
- Department of Physics, University of Helsinki, FL-00014, Helsinki, Finland.,Computational Physics Laboratory, Tampere University, Fl-33100, Tampere, Finland
| | - Christian Freund
- Institute for Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195, Berlin, Germany
| | - Walter Nickel
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120, Heidelberg, Germany.
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14
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Furini G, Burhan I, Huang L, Savoca MP, Atobatele A, Johnson T, Verderio EAM. Insights into the heparan sulphate-dependent externalisation of transglutaminase-2 (TG2) in glucose-stimulated proximal-like tubular epithelial cells. Anal Biochem 2020; 603:113628. [PMID: 32074489 DOI: 10.1016/j.ab.2020.113628] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Revised: 01/25/2020] [Accepted: 02/12/2020] [Indexed: 02/09/2023]
Abstract
The extracellular matrix crosslinking enzyme transglutaminase 2 (TG2) is highly implicated in tissue fibrosis that precedes end-stage kidney failure. TG2 is unconventionally secreted through extracellular vesicles in a way that depends on the heparan sulphate (HS) proteoglycan syndecan-4 (Sdc4), the deletion of which reduces experimental kidney fibrosis as a result of lower extracellular TG2 in the tubule-interstitium. Here we establish a model of TG2 externalisation in NRK-52E tubular epithelial cells subjected to glucose stress. HS-binding TG2 mutants had reduced extracellular TG2 in transfected NRK-52E, suggesting that TG2-externalisation depends on an intact TG2 heparin binding site. Inhibition of N-ethylmaleimide sensitive factor (NSF) vesicle-fusing ATPase, which was identified in the recently elucidated TG2 kidney membrane-interactome, led to significantly lower TG2-externalisation, thus validating the involvement of membrane fusion in TG2 secretion. As cyclin-G-associated kinase (GAK) had emerged as a further TG2-partner in the fibrotic kidney, we investigated whether glucose-induced TG2-externalisation was accompanied by TG2 phosphorylation in consensus sequences of cyclin-dependent kinase (CDK). Glucose stress led to intense TG2 phosphorylation in serine/threonine CDK-target. TG2 phosphorylation by tyrosine kinases was also increased by glucose. Although the precise role of glucose-induced TG2 phosphorylation is unknown, these novel data suggest that phosphorylation may be involved in TG2 membrane-trafficking.
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Affiliation(s)
- Giulia Furini
- School of Science and Technology, Centre for Health, Ageing and Understanding of Disease, Nottingham Trent University, Nottingham, NG11 8NS, UK
| | - Izhar Burhan
- School of Science and Technology, Centre for Health, Ageing and Understanding of Disease, Nottingham Trent University, Nottingham, NG11 8NS, UK
| | - Linghong Huang
- University of Sheffield, Academic Nephrology Unit, Medical School, Sheffield, S10 2RZ, United Kingdom
| | - Maria Pia Savoca
- School of Science and Technology, Centre for Health, Ageing and Understanding of Disease, Nottingham Trent University, Nottingham, NG11 8NS, UK
| | - Adeola Atobatele
- School of Science and Technology, Centre for Health, Ageing and Understanding of Disease, Nottingham Trent University, Nottingham, NG11 8NS, UK
| | - Tim Johnson
- University of Sheffield, Academic Nephrology Unit, Medical School, Sheffield, S10 2RZ, United Kingdom
| | - Elisabetta A M Verderio
- School of Science and Technology, Centre for Health, Ageing and Understanding of Disease, Nottingham Trent University, Nottingham, NG11 8NS, UK; BiGeA, University of Bologna, Bologna, 40126, Italy.
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15
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Ahmed M, Legrand C, Yagüe Relimpio A, Beretta CA, Muschko A, Wegehingel S, Müller HM, Sehr P, Will DW, Lewis JD, Nickel W. A time-resolved live cell imaging assay to identify small molecule inhibitors of FGF2 signaling. FEBS Lett 2019; 593:2162-2176. [PMID: 31135968 DOI: 10.1002/1873-3468.13462] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 05/18/2019] [Accepted: 05/24/2019] [Indexed: 11/10/2022]
Abstract
Fibroblast growth factor 2 (FGF2) is a cell survival factor with crucial functions in tumor-induced angiogenesis. Here, we describe a novel time-resolved FGF2 signaling assay based upon live cell imaging of neuroblastoma cells. To validate this system, we tested 8960 small molecules for inhibition of FGF2 signaling with kinetic resolution. Hit compounds were validated in dose-response experiments for FGF2 signaling, FGF receptor antagonism, downstream ERK phosphorylation and FGF2-dependent chemoresistance in a cellular leukemia model system. The new screening system for FGF2 signaling inhibitors has unique features, deselecting compounds with pleiotropic effects on cell proliferation and, along with the experimental pipeline reported, great potential for the discovery of new classes of FGF2 signaling inhibitors that block FGF2 dependent tumor cell survival.
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Affiliation(s)
| | | | | | - Carlo A Beretta
- CellNetworks Math-Clinic Core Facility, BioQuant, Heidelberg University, Germany
| | | | | | | | - Peter Sehr
- European Molecular Biology Laboratory, Heidelberg, Germany
| | - David W Will
- European Molecular Biology Laboratory, Heidelberg, Germany
| | - Joe D Lewis
- European Molecular Biology Laboratory, Heidelberg, Germany
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16
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Furini G, Verderio EAM. Spotlight on the Transglutaminase 2-Heparan Sulfate Interaction. Med Sci (Basel) 2019; 7:E5. [PMID: 30621228 PMCID: PMC6359630 DOI: 10.3390/medsci7010005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 12/17/2018] [Accepted: 12/18/2018] [Indexed: 02/07/2023] Open
Abstract
Heparan sulfate proteoglycans (HSPGs), syndecan-4 (Sdc4) especially, have been suggested as potential partners of transglutaminase-2 (TG2) in kidney and cardiac fibrosis, metastatic cancer, neurodegeneration and coeliac disease. The proposed role for HSPGs in the trafficking of TG2 at the cell surface and in the extracellular matrix (ECM) has been linked to the fibrogenic action of TG2 in experimental models of kidney fibrosis. As the TG2-HSPG interaction is largely mediated by the heparan sulfate (HS) chains of proteoglycans, in the past few years a number of studies have investigated the affinity of TG2 for HS, and the TG2 heparin binding site has been mapped with alternative outlooks. In this review, we aim to provide a compendium of the main literature available on the interaction of TG2 with HS, with reference to the pathological processes in which extracellular TG2 plays a role.
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Affiliation(s)
- Giulia Furini
- School of Science and Technology, Nottingham Trent University, Nottingham NG11 8NS, UK.
| | - Elisabetta A M Verderio
- School of Science and Technology, Nottingham Trent University, Nottingham NG11 8NS, UK.
- BiGeA, University of Bologna, 40126 Bologna, Italy.
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17
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Lee J, Ye Y. The Roles of Endo-Lysosomes in Unconventional Protein Secretion. Cells 2018; 7:cells7110198. [PMID: 30400277 PMCID: PMC6262434 DOI: 10.3390/cells7110198] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2018] [Revised: 10/30/2018] [Accepted: 10/31/2018] [Indexed: 12/21/2022] Open
Abstract
Protein secretion in general depends on signal sequence (also named leader sequence), a hydrophobic segment located at or close to the NH2-terminus of a secretory or membrane protein. This sequence guides the entry of nascent polypeptides into the lumen or membranes of the endoplasmic reticulum (ER) for folding, assembly, and export. However, evidence accumulated in recent years has suggested the existence of a collection of unconventional protein secretion (UPS) mechanisms that are independent of the canonical vesicular trafficking route between the ER and the plasma membrane (PM). These UPS mechanisms export soluble proteins bearing no signal sequence. The list of UPS cargos is rapidly expanding, along with the implicated biological functions, but molecular mechanisms accountable for the secretion of leaderless proteins are still poorly defined. This review summarizes our current understanding of UPS mechanisms with an emphasis on the emerging role of endo-lysosomes in this process.
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Affiliation(s)
- Juhyung Lee
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Yihong Ye
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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18
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Steringer JP, Nickel W. A direct gateway into the extracellular space: Unconventional secretion of FGF2 through self-sustained plasma membrane pores. Semin Cell Dev Biol 2018; 83:3-7. [PMID: 29458182 DOI: 10.1016/j.semcdb.2018.02.010] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Revised: 02/01/2018] [Accepted: 02/08/2018] [Indexed: 10/17/2022]
Abstract
As illustrated by a diverse set of examples in this special issue, multiple mechanisms of protein secretion have been identified in eukaryotes that do not involve the endoplasmic reticulum (ER) and the Golgi apparatus. Here we focus on the type I pathway with Fibroblast Growth Factor 2 (FGF2) being the most prominent example. Unconventional secretion of FGF2 from cells is mediated by direct protein translocation across the plasma membrane. A unique feature of this process is the ability of FGF2 to form its own membrane translocation intermediate through oligomerization and membrane insertion. This process depends on the phosphoinositide PI(4,5)P2 at the inner leaflet and results in the formation of lipidic membrane pores in the plasma membrane. Various lines of evidence suggest that these pores are characterized by a toroidal architecture with FGF2 oligomers being accommodated in the center of these structures. At the outer leaflet of the plasma membrane, membrane proximal heparan sulfate proteoglycans are required for the final step of FGF2 translocation into the extracellular space. Based upon mutually exclusive interactions of FGF2 with PI(4,5)P2 versus heparan sulfates, an assembly/disassembly pathway has been proposed to be the underlying principle of directional transport of FGF2 across the plasma membrane. Thus, the core mechanism of unconventional secretion of FGF2 is based upon three discrete steps with (i) PI(4,5)P2 dependent oligomerization of FGF2 at the inner leaflet, (ii) insertion of membrane spanning FGF2 oligomers into the plasma membrane and (iii) disassembly at the outer leaflet mediated by heparan sulfates that subsequently retain FGF2 on cell surfaces. This process has recently been reconstituted with an inside-out membrane model system using giant unilamellar vesicles providing a compelling explanation of how FGF2 reaches the extracellular space in an ER/Golgi independent manner. This review is part of a Special Issue of SCDB on "unconventional protein secretion" edited by Walter Nickel and Catherine Rabouille.
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Affiliation(s)
- Julia P Steringer
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
| | - Walter Nickel
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany.
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19
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Park S, Arrell DK, Reyes S, Park EY, Terzic A. Conventional and unconventional secretory proteins expressed with silkworm bombyxin signal peptide display functional fidelity. Sci Rep 2017; 7:14499. [PMID: 29101331 PMCID: PMC5670176 DOI: 10.1038/s41598-017-14833-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 10/18/2017] [Indexed: 11/10/2022] Open
Abstract
Growth factors are signaling molecules which orchestrate cell growth, proliferation and differentiation. The majority are secreted proteins, exported through the classical endoplasmic reticulum (ER)/Golgi-dependent pathway, but a few are released by unconventional ER/Golgi-independent means. Human fibroblast growth factor 2 (FGF2) and insulin-like growth factor 1 (IGF1), are canonical prototypes secreted by the unconventional and conventional pathway, respectively. We herein examined whether expression of these two growth factors in the Bombyx mori nucleopolyhedrovirus (BmNPV)-based silkworm expression system with its innate signal peptide, bombyxin, secures structural homogeneity at the signal peptide cleavage site regardless of the native secretory route. Proteomic analysis mapped structural microheterogeneity of signal peptide cleavage at the amino terminus of FGF2, whereas IGF1 displayed homogeneous amino-terminal cleavage with complete removal of the bombyxin signal peptide. A cell proliferation assay revealed potent functional activity of both FGF2 and IGF1, suggesting that FGF2 amino-terminal microheterogeneity does not alter mitogenic activity. These findings demonstrate that the occurrence of amino-terminal structural homogeneity may be associated with the original secretion mechanism of a particular growth factor. Furthermore, our results highlight the bombyxin signal peptide as a reliable secretion sequence applicable to mass production of functionally active secretory proteins in a silkworm-based expression platform.
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Affiliation(s)
- Sungjo Park
- Center for Regenerative Medicine, Mayo Clinic, Rochester, Minnesota, USA.,Marriott Heart Disease Research Program, Departments of Cardiovascular Medicine, Molecular Pharmacology and Experimental Therapeutics, and Medical Genetics, Mayo Clinic, Rochester, Minnesota, USA
| | - D Kent Arrell
- Center for Regenerative Medicine, Mayo Clinic, Rochester, Minnesota, USA.,Marriott Heart Disease Research Program, Departments of Cardiovascular Medicine, Molecular Pharmacology and Experimental Therapeutics, and Medical Genetics, Mayo Clinic, Rochester, Minnesota, USA
| | - Santiago Reyes
- Center for Regenerative Medicine, Mayo Clinic, Rochester, Minnesota, USA.,Marriott Heart Disease Research Program, Departments of Cardiovascular Medicine, Molecular Pharmacology and Experimental Therapeutics, and Medical Genetics, Mayo Clinic, Rochester, Minnesota, USA.,Department of Surgery, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Enoch Y Park
- Laboratory of Biotechnology, Graduate School of Science and Technology, Shizuoka University, Shizuoka, Japan
| | - Andre Terzic
- Center for Regenerative Medicine, Mayo Clinic, Rochester, Minnesota, USA. .,Marriott Heart Disease Research Program, Departments of Cardiovascular Medicine, Molecular Pharmacology and Experimental Therapeutics, and Medical Genetics, Mayo Clinic, Rochester, Minnesota, USA.
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20
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Steringer JP, Nickel W. The molecular mechanism underlying unconventional secretion of Fibroblast Growth Factor 2 from tumour cells. Biol Cell 2017; 109:375-380. [PMID: 28799166 DOI: 10.1111/boc.201700036] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 08/07/2017] [Accepted: 08/07/2017] [Indexed: 11/29/2022]
Abstract
Fibroblast Growth Factor 2 (FGF2) is a potent cell survival factor involved in tumour-induced angiogenesis. FGF2 is secreted from cells through an unconventional secretory mechanism based upon direct translocation across the plasma membrane. The molecular mechanism underlying this process depends on a surprisingly small set of trans-acting factors that are physically associated with the plasma membrane. FGF2 membrane translocation is mediated by the ability of FGF2 to oligomerise and to insert into the plasma membrane in a PI(4,5)P2 -dependent manner. Membrane-inserted FGF2 oligomers are dynamic translocation intermediates that are disassembled at the extracellular leaflet mediated by membrane proximal heparan sulphate proteoglycans. This process results in the exposure of FGF2 on cell surfaces as part of its unconventional mechanism of secretion. Although the trans-acting factors and cis-elements in FGF2 required for unconventional secretion have been known for a while, the core mechanism of this mysterious process has now been reconstituted with purified components establishing the molecular basis of FGF2 secretion from tumour cells.
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Affiliation(s)
| | - Walter Nickel
- Heidelberg University Biochemistry Center, Heidelberg, Germany
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21
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Brough D, Pelegrin P, Nickel W. An emerging case for membrane pore formation as a common mechanism for the unconventional secretion of FGF2 and IL-1β. J Cell Sci 2017; 130:3197-3202. [PMID: 28871048 DOI: 10.1242/jcs.204206] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 07/20/2017] [Indexed: 12/12/2022] Open
Abstract
Extracellular proteins with important signalling roles in processes, such as inflammation and angiogenesis, are known to employ unconventional routes of protein secretion. Although mechanisms of unconventional protein secretion are beginning to emerge, the precise molecular details have remained elusive for the majority of cargo proteins secreted by unconventional means. Recent findings suggest that for two examples of unconventionally secreted proteins, interleukin 1β (IL-1β) and fibroblast growth factor 2 (FGF2), the common molecular principle of pore formation may be shared. Under specific experimental conditions, secretion of IL-1β and FGF2 is triggered by phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2]-dependent formation of pores across the plasma membrane. However, the underlying mechanisms are different, with FGF2 known to directly interact with PI(4,5)P2, whereas in the case of IL-1β secretion, it is proposed that the N-terminal fragment of gasdermin D interacts with PI(4,5)P2 to form the pore. Thus, although implemented in different ways, these findings suggest that pore formation may be shared by the unconventional secretion mechanisms for FGF2 and IL-1β in at least some cases. In this Opinion article, we discuss the unconventional mechanisms of FGF2 and IL-1β release with a particular emphasis on recent discoveries suggesting the importance of pore formation on the plasma membrane.
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Affiliation(s)
- David Brough
- Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, M13 9PT, UK
| | - Pablo Pelegrin
- Grupo de Inflamación Molecular, Hospital Clínico Universitario Virgen de la Arrixaca, Instituto Murciano de Investigación Biosanitaria-Arrixaca (IMIB-Arrixaca), 30120 Murcia, Spain
| | - Walter Nickel
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
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22
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Steringer JP, Lange S, Čujová S, Šachl R, Poojari C, Lolicato F, Beutel O, Müller HM, Unger S, Coskun Ü, Honigmann A, Vattulainen I, Hof M, Freund C, Nickel W. Key steps in unconventional secretion of fibroblast growth factor 2 reconstituted with purified components. eLife 2017; 6. [PMID: 28722655 PMCID: PMC5601999 DOI: 10.7554/elife.28985] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 07/14/2017] [Indexed: 12/31/2022] Open
Abstract
FGF2 is secreted from cells by an unconventional secretory pathway. This process is mediated by direct translocation across the plasma membrane. Here, we define the minimal molecular machinery required for FGF2 membrane translocation in a fully reconstituted inside-out vesicle system. FGF2 membrane translocation is thermodynamically driven by PI(4,5)P2-induced membrane insertion of FGF2 oligomers. The latter serve as dynamic translocation intermediates of FGF2 with a subunit number in the range of 8-12 FGF2 molecules. Vectorial translocation of FGF2 across the membrane is governed by sequential and mutually exclusive interactions with PI(4,5)P2 and heparan sulfates on opposing sides of the membrane. Based on atomistic molecular dynamics simulations, we propose a mechanism that drives PI(4,5)P2 dependent oligomerization of FGF2. Our combined findings establish a novel type of self-sustained protein translocation across membranes revealing the molecular basis of the unconventional secretory pathway of FGF2. DOI:http://dx.doi.org/10.7554/eLife.28985.001
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Affiliation(s)
| | - Sascha Lange
- Institut für Chemie und Biochemie, Freie Universität Berlin, Berlin, Germany
| | - Sabína Čujová
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Radek Šachl
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Chetan Poojari
- Department of Physics, University of Helsinki, Helsinki, Finland.,Department of Physics, Tampere University of Technology, Tampere, Finland
| | - Fabio Lolicato
- Department of Physics, University of Helsinki, Helsinki, Finland.,Department of Physics, Tampere University of Technology, Tampere, Finland
| | - Oliver Beutel
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | | | - Sebastian Unger
- Heidelberg University Biochemistry Center, Heidelberg, Germany
| | - Ünal Coskun
- Paul Langerhans Institute Dresden, Helmholtz Zentrum München, University Hospital and Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.,Deutsches Zentrum fur Diabetesforschung, Neuherberg, Germany
| | - Alf Honigmann
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Ilpo Vattulainen
- Department of Physics, University of Helsinki, Helsinki, Finland.,Department of Physics, Tampere University of Technology, Tampere, Finland.,MEMPHYS - Center for Biomembrane Physics, University of Southern Denmark, Denmark, United Kingdom
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Christian Freund
- Institut für Chemie und Biochemie, Freie Universität Berlin, Berlin, Germany
| | - Walter Nickel
- Heidelberg University Biochemistry Center, Heidelberg, Germany
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23
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Teis D, Kukulski W. Meeting report - Emerging Concepts in Cell Organization. J Cell Sci 2017; 130:2229-2233. [PMID: 28738320 DOI: 10.1242/jcs.206219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
New concepts in cell organization emerged in a medieval castle during a snowy week in January 2017 in the middle of the Austrian Alps. The occasion was the 10th Annaberg EMBO workshop in Goldegg am See; organized by Gabriele Seethaler, Catherine Rabouille and Marino Zerial. There were 95 participants, including many who gave talks and presented posters, enjoying a familial and trusting atmosphere that stimulated lively exchange of (unpublished) results, new ideas and thoughts.
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Affiliation(s)
- David Teis
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Wanda Kukulski
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
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24
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Vanova T, Konecna Z, Zbonakova Z, La Venuta G, Zoufalova K, Jelinkova S, Varecha M, Rotrekl V, Krejci P, Nickel W, Dvorak P, Kunova Bosakova M. Tyrosine Kinase Expressed in Hepatocellular Carcinoma, TEC, Controls Pluripotency and Early Cell Fate Decisions of Human Pluripotent Stem Cells via Regulation of Fibroblast Growth Factor-2 Secretion. Stem Cells 2017. [PMID: 28631381 DOI: 10.1002/stem.2660] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Human pluripotent stem cells (hPSC) require signaling provided by fibroblast growth factor (FGF) receptors. This can be initiated by the recombinant FGF2 ligand supplied exogenously, but hPSC further support their niche by secretion of endogenous FGF2. In this study, we describe a role of tyrosine kinase expressed in hepatocellular carcinoma (TEC) kinase in this process. We show that TEC-mediated FGF2 secretion is essential for hPSC self-renewal, and its lack mediates specific differentiation. Following both short hairpin RNA- and small interfering RNA-mediated TEC knockdown, hPSC secretes less FGF2. This impairs hPSC proliferation that can be rescued by increasing amounts of recombinant FGF2. TEC downregulation further leads to a lower expression of the pluripotency markers, an improved priming towards neuroectodermal lineage, and a failure to develop cardiac mesoderm. Our data thus demonstrate that TEC is yet another regulator of FGF2-mediated hPSC pluripotency and differentiation. Stem Cells 2017;35:2050-2059.
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Affiliation(s)
- Tereza Vanova
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Zaneta Konecna
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Zuzana Zbonakova
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | | | - Karolina Zoufalova
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic.,International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic
| | - Sarka Jelinkova
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Miroslav Varecha
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic.,International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic
| | - Vladimir Rotrekl
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic.,International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic
| | - Pavel Krejci
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic.,International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic
| | - Walter Nickel
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Petr Dvorak
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic.,Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
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25
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Daniels MJD, Brough D. Unconventional Pathways of Secretion Contribute to Inflammation. Int J Mol Sci 2017; 18:E102. [PMID: 28067797 PMCID: PMC5297736 DOI: 10.3390/ijms18010102] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 12/16/2016] [Accepted: 12/30/2016] [Indexed: 12/13/2022] Open
Abstract
In the conventional pathway of protein secretion, leader sequence-containing proteins leave the cell following processing through the endoplasmic reticulum (ER) and Golgi body. However, leaderless proteins also enter the extracellular space through mechanisms collectively known as unconventional secretion. Unconventionally secreted proteins often have vital roles in cell and organism function such as inflammation. Amongst the best-studied inflammatory unconventionally secreted proteins are interleukin (IL)-1β, IL-1α, IL-33 and high-mobility group box 1 (HMGB1). In this review we discuss the current understanding of the unconventional secretion of these proteins and highlight future areas of research such as the role of nuclear localisation.
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Affiliation(s)
- Michael J D Daniels
- Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, University of Manchester, AV Hill Building, Oxford Road, Manchester M13 9PT, UK.
| | - David Brough
- Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, University of Manchester, AV Hill Building, Oxford Road, Manchester M13 9PT, UK.
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Rabouille C. Pathways of Unconventional Protein Secretion. Trends Cell Biol 2016; 27:230-240. [PMID: 27989656 DOI: 10.1016/j.tcb.2016.11.007] [Citation(s) in RCA: 368] [Impact Index Per Article: 46.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 11/14/2016] [Accepted: 11/15/2016] [Indexed: 01/02/2023]
Abstract
Secretory proteins are conventionally transported through the endoplasmic reticulum to the Golgi and then to the plasma membrane where they are released into the extracellular space. However, numerous substrates also reach these destinations using unconventional pathways. Unconventional protein secretion (UPS) is complex and comprises cargos without a signal peptide or a transmembrane domain that can translocate across the plasma membrane, and cargos that reach the plasma membrane by bypassing the Golgi despite entering the endoplasmic reticulum (ER). With a few exceptions, unconventional secretion is largely triggered by stress. Here I review new results and concepts that are beginning to define these pathways.
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Affiliation(s)
- Catherine Rabouille
- Hubrecht Institute of the KNAW and UMC Utrecht, Utrecht, The Netherlands; Department of Cell Biology, UMC Utrecht, Utrecht, The Netherlands; Department of Cell Biology, UMC Groningen, Groningen, The Netherlands.
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