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Chiu PL, Orjuela JD, de Groot BL, Aponte-Santamaría C, Walz T. Structure and dynamics of cholesterol-mediated aquaporin-0 arrays and implications for lipid rafts. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.05.16.540959. [PMID: 37292626 PMCID: PMC10245776 DOI: 10.1101/2023.05.16.540959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Aquaporin-0 (AQP0) tetramers form square arrays in lens membranes through a yet unknown mechanism, but lens membranes are enriched in sphingomyelin and cholesterol. Here, we determined electron crystallographic structures of AQP0 in sphingomyelin/cholesterol membranes and performed molecular dynamics (MD) simulations to establish that the observed cholesterol positions represent those seen around an isolated AQP0 tetramer and that the AQP0 tetramer largely defines the location and orientation of most of its associated cholesterol molecules. At a high concentration, cholesterol increases the hydrophobic thickness of the annular lipid shell around AQP0 tetramers, which may thus cluster to mitigate the resulting hydrophobic mismatch. Moreover, neighboring AQP0 tetramers sandwich a cholesterol deep in the center of the membrane. MD simulations show that the association of two AQP0 tetramers is necessary to maintain the deep cholesterol in its position and that the deep cholesterol increases the force required to laterally detach two AQP0 tetramers, not only due to protein-protein contacts but also due to increased lipid-protein complementarity. Since each tetramer interacts with four such 'glue' cholesterols, avidity effects may stabilize larger arrays. The principles proposed to drive AQP0 array formation could also underlie protein clustering in lipid rafts.
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2
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Mikuličić S, Shamun M, Massenberg A, Franke AL, Freitag K, Döring T, Strunk J, Tenzer S, Lang T, Florin L. ErbB2/HER2 receptor tyrosine kinase regulates human papillomavirus promoter activity. Front Immunol 2024; 15:1335302. [PMID: 38370412 PMCID: PMC10869470 DOI: 10.3389/fimmu.2024.1335302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Accepted: 01/16/2024] [Indexed: 02/20/2024] Open
Abstract
Human papillomaviruses (HPVs) are a major cause of cancer. While surgical intervention remains effective for a majority of HPV-caused cancers, the urgent need for medical treatments targeting HPV-infected cells persists. The pivotal early genes E6 and E7, which are under the control of the viral genome's long control region (LCR), play a crucial role in infection and HPV-induced oncogenesis, as well as immune evasion. In this study, proteomic analysis of endosomes uncovered the co-internalization of ErbB2 receptor tyrosine kinase, also called HER2/neu, with HPV16 particles from the plasma membrane. Although ErbB2 overexpression has been associated with cervical cancer, its influence on HPV infection stages was previously unknown. Therefore, we investigated the role of ErbB2 in HPV infection, focusing on HPV16. Through siRNA-mediated knockdown and pharmacological inhibition studies, we found that HPV16 entry is independent of ErbB2. Instead, our signal transduction and promoter assays unveiled a concentration- and activation-dependent regulatory role of ErbB2 on the HPV16 LCR by supporting viral promoter activity. We also found that ErbB2's nuclear localization signal was not essential for LCR activity, but rather the cellular ErbB2 protein level and activation status that were inhibited by tucatinib and CP-724714. These ErbB2-specific tyrosine kinase inhibitors as well as ErbB2 depletion significantly influenced the downstream Akt and ERK signaling pathways and LCR activity. Experiments encompassing low-risk HPV11 and high-risk HPV18 LCRs uncovered, beyond HPV16, the importance of ErbB2 in the general regulation of the HPV early promoter. Expanding our investigation to directly assess the impact of ErbB2 on viral gene expression, quantitative analysis of E6 and E7 transcript levels in HPV16 and HPV18 transformed cell lines unveiled a noteworthy decrease in oncogene expression following ErbB2 depletion, concomitant with the downregulation of Akt and ERK signaling pathways. In light of these findings, we propose that ErbB2 holds promise as potential target for treating HPV infections and HPV-associated malignancies by silencing viral gene expression.
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Affiliation(s)
- Snježana Mikuličić
- Institute for Virology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Merha Shamun
- Institute for Virology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Annika Massenberg
- University of Bonn, Faculty of Mathematics and Natural Sciences, Life & Medical Sciences (LIMES) Institute, Bonn, Rheinland-Pfalz, Germany
| | - Anna-Lena Franke
- Institute for Virology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Kirsten Freitag
- Institute for Virology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Tatjana Döring
- Institute for Virology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Johannes Strunk
- Institute for Virology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Stefan Tenzer
- Institute for Immunology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Rheinland-Pfalz, Germany
- Helmholtz Institute for Translational Oncology (HI-TRON) Mainz, Mainz, Rheinland-Pfalz, Germany
| | - Thorsten Lang
- University of Bonn, Faculty of Mathematics and Natural Sciences, Life & Medical Sciences (LIMES) Institute, Bonn, Rheinland-Pfalz, Germany
| | - Luise Florin
- Institute for Virology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
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3
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Schmidt SC, Massenberg A, Homsi Y, Sons D, Lang T. Microscopic clusters feature the composition of biochemical tetraspanin-assemblies and constitute building-blocks of tetraspanin enriched domains. Sci Rep 2024; 14:2093. [PMID: 38267610 PMCID: PMC10808221 DOI: 10.1038/s41598-024-52615-1] [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: 09/22/2023] [Accepted: 01/21/2024] [Indexed: 01/26/2024] Open
Abstract
Biochemical approaches revealed that tetraspanins are multi-regulatory proteins forming a web, where they act in tetraspanin-enriched-microdomains (TEMs). A microscopic criterion differentiating between web and TEMs is lacking. Using super-resolution microcopy, we identify co-assemblies between the tetraspanins CD9 and CD81 and CD151 and CD81. CD9 assemblies contain as well the CD9/CD81-interaction partner EWI-2. Moreover, CD9 clusters are proximal to clusters of the CD81-interaction partner CD44 and CD81-/EWI-2-interacting ezrin-radixin-moesin proteins. Assemblies scatter unorganized across the cell membrane; yet, upon EWI-2 elevation, they agglomerate into densely packed arranged-crowds in a process independent from actin dynamics. In conclusion, microscopic clusters are equivalent to biochemical tetraspanin-assemblies, defining in their entirety the tetraspanin web. Cluster-agglomeration enriches tetraspanins, which makes agglomerations to a microscopic complement of TEMs. The microscopic classification of tetraspanin assemblies advances our understanding of this enigmatic protein family, whose members play roles in a plethora of cellular functions, diseases, and pathogen infections.
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Affiliation(s)
- Sara C Schmidt
- Faculty of Mathematics and Natural Sciences, Life & Medical Sciences (LIMES) Institute, University of Bonn, Carl-Troll-Straße 31, 53115, Bonn, Germany
| | - Annika Massenberg
- Faculty of Mathematics and Natural Sciences, Life & Medical Sciences (LIMES) Institute, University of Bonn, Carl-Troll-Straße 31, 53115, Bonn, Germany
| | - Yahya Homsi
- Faculty of Mathematics and Natural Sciences, Life & Medical Sciences (LIMES) Institute, University of Bonn, Carl-Troll-Straße 31, 53115, Bonn, Germany
| | - Dominik Sons
- Faculty of Mathematics and Natural Sciences, Life & Medical Sciences (LIMES) Institute, University of Bonn, Carl-Troll-Straße 31, 53115, Bonn, Germany
| | - Thorsten Lang
- Faculty of Mathematics and Natural Sciences, Life & Medical Sciences (LIMES) Institute, University of Bonn, Carl-Troll-Straße 31, 53115, Bonn, Germany.
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4
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Kumari A, Saha D, Bhattacharya J, Aswal VK, Moulick RG. Studying the structural organization of non-membranous protein hemoglobin in a lipid environment after reconstitution. Int J Biol Macromol 2023:125212. [PMID: 37302629 DOI: 10.1016/j.ijbiomac.2023.125212] [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: 01/29/2023] [Revised: 05/24/2023] [Accepted: 06/01/2023] [Indexed: 06/13/2023]
Abstract
In our current work we have developed a supported 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer with embedded hemoglobin, reconstituted via detergent-mediated method. Microscopic studies revealed that the hemoglobin molecules could be visualized without any labelling agents. The reconstituted proteins assemble themselves as supramolecular structures to adapt to lipid bilayer environment. The nonionic detergent, n-octyl-β-d-glucoside (NOG) used for insertion of hemoglobin played an important role in formation of these structures. When concentrations of lipid, protein and detergent were raised by four folds, we observed phase separation by protein molecules within bilayer via protein-protein assembly. This phase separation process exhibited extremely slow kinetics to form large stable domains with correlation times in the order of minutes. Confocal Z-scanning images showed that these supramolecular structures generated membrane deformities. UV-Vis, Fluorescence and Circular Dichroism (CD) measurement indicated minor structural change to expose the hydrophobic regions of the protein to adjust the hydrophobic stress of the lipid environment whilst Small Angle Neutron Scattering (SANS) results indicated that the hemoglobin molecules retained their overall tetrameric form in the system. In conclusion, we state that this investigation allowed us to closely inspect some rare but noteworthy phenomena like the formation of supramolecular structures, large domain formation and membrane deformation etc.
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Affiliation(s)
- Akanksha Kumari
- Amity Institute of Biotechnology, Amity University Haryana, 122413, India
| | - Debasish Saha
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
| | | | - V K Aswal
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
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5
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Sui B, Chen J, Ge D, Liang F, Wang H. Assembly Characterization of Human Equilibrium Nucleoside Transporter 1 (hENT1) by Inhibitor Probe-Based dSTORM Imaging. Anal Chem 2023. [PMID: 37276019 DOI: 10.1021/acs.analchem.3c00596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Nucleoside transporters (NTs) play an important role in the metabolism of nucleoside substances and the efficacy of nucleoside drugs. Its spatial information related to biofunctions at the single-molecule level remains unclear, owing to the limitation of the existing labeling methods and traditional imaging methods. Therefore, we synthesize the inhibitor-based fluorescent probe SAENTA-Cy5 and apply direct stochastic optical reconstruction microscopy (dSTORM) to conduct refined observation of human equilibrative nucleoside transporter 1 (hENT1), the most important and famous member of NTs. We first demonstrate the labeling specificity and superiority of SAENTA-Cy5 to the antibody probe. Then, we found different assembly patterns of hENT1 on the apical and basal membranes, which are further investigated to be caused by varying associations of membrane carbohydrates, membrane classical functional domains (lipid rafts), and associated membrane proteins (EpCAM). Our work provides an efficient method for labeling hENT1, which contributes to realize fine observation of NTs. The findings on the assembly features and potential assembly mechanism of hENT1 promote a better understanding of its biofunction, which facilitates further investigations on how NTs work in the metabolism of nucleoside and nucleoside analogues.
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Affiliation(s)
- Binglin Sui
- Improve-WUST Joint Laboratory of Advanced Technology for Point-of-Care Testing and Precision Medicine, School of Chemistry & Chemical Engineering, Wuhan University of Science and Technology, 947 Heping Street, Wuhan, Hubei 430081, China
| | - Junling Chen
- Improve-WUST Joint Laboratory of Advanced Technology for Point-of-Care Testing and Precision Medicine, School of Chemistry & Chemical Engineering, Wuhan University of Science and Technology, 947 Heping Street, Wuhan, Hubei 430081, China
| | - Dian Ge
- Improve-WUST Joint Laboratory of Advanced Technology for Point-of-Care Testing and Precision Medicine, School of Chemistry & Chemical Engineering, Wuhan University of Science and Technology, 947 Heping Street, Wuhan, Hubei 430081, China
| | - Feng Liang
- Improve-WUST Joint Laboratory of Advanced Technology for Point-of-Care Testing and Precision Medicine, School of Chemistry & Chemical Engineering, Wuhan University of Science and Technology, 947 Heping Street, Wuhan, Hubei 430081, China
| | - Hongda Wang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Research Center of Biomembranomics, 5625 Renmin Street, Changchun, Jilin 130022, China
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6
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Andersen C, Zulueta Díaz YDLM, Kure JL, Hessellund Eriksen M, Lovatt AL, Lagerholm C, Morales S, Sehayek S, Sheard TMD, Wiseman PW, Arnspang EC. Angiotensin II Treatment Induces Reorganization and Changes in the Lateral Dynamics of Angiotensin II Type 1 Receptor in the Plasma Membrane Elucidated by Photoactivated Localization Microscopy Combined with Image Spatial Correlation Analysis. Anal Chem 2023; 95:730-738. [PMID: 36574961 DOI: 10.1021/acs.analchem.2c02720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The mechanisms by which angiotensin II type 1 receptor is distributed and the diffusional pattern in the plasma membrane (PM) remain unclear, despite their crucial role in cardiovascular homeostasis. In this work, we obtained quantitative information of angiotensin II type 1 receptor (AT1R) lateral dynamics as well as changes in the diffusion properties after stimulation with ligands in living cells using photoactivated localization microscopy (PALM) combined with image spatial-temporal correlation analysis. To study the organization of the receptor at the nanoscale, expansion microscopy (ExM) combined with PALM was performed. This study revealed that AT1R lateral diffusion increased after binding to angiotensin II (Ang II) and the receptor diffusion was transiently confined in the PM. In addition, ExM revealed that AT1R formed nanoclusters at the PM and the cluster size significantly decreased after Ang II treatment. Taking these results together suggest that Ang II binding and activation cause reorganization and changes in the dynamics of AT1R at the PM.
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Affiliation(s)
- Camilla Andersen
- SDU Biotechnology, Department of Green Technology, University of Southern Denmark, Odense M5230, Denmark
| | | | - Jakob L Kure
- SDU Biotechnology, Department of Green Technology, University of Southern Denmark, Odense M5230, Denmark
| | - Mathias Hessellund Eriksen
- SDU Biotechnology, Department of Green Technology, University of Southern Denmark, Odense M5230, Denmark
| | - Adam Leslie Lovatt
- SDU Biotechnology, Department of Green Technology, University of Southern Denmark, Odense M5230, Denmark
| | | | - Sebastian Morales
- Department of Physics and Department of Chemistry, McGill University, MontrealH3A 0B8, Canada
| | - Simon Sehayek
- Department of Physics and Department of Chemistry, McGill University, MontrealH3A 0B8, Canada
| | - Thomas M D Sheard
- School of Biosciences, University of Sheffield, SheffieldS10 2TN, U.K
| | - Paul W Wiseman
- Department of Physics and Department of Chemistry, McGill University, MontrealH3A 0B8, Canada
| | - Eva C Arnspang
- SDU Biotechnology, Department of Green Technology, University of Southern Denmark, Odense M5230, Denmark
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7
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Yang X, Tu W, Gao X, Zhang Q, Guan J, Zhang J. Functional regulation of syntaxin-1: An underlying mechanism mediating exocytosis in neuroendocrine cells. Front Endocrinol (Lausanne) 2023; 14:1096365. [PMID: 36742381 PMCID: PMC9892835 DOI: 10.3389/fendo.2023.1096365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Accepted: 01/05/2023] [Indexed: 01/20/2023] Open
Abstract
The fusion of the secretory vesicle with the plasma membrane requires the assembly of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein complexes formed by synaptobrevin, syntaxin-1, and SNAP-25. Within the pathway leading to exocytosis, the transitions between the "open" and "closed" conformations of syntaxin-1 function as a switch for the fusion of vesicles with the plasma membranes; rapid assembly and disassembly of syntaxin-1 clusters on the plasma membrane provide docking and fusion sites for secretory vesicles in neuroendocrine cells; and the fully zippered trans-SNARE complex, which requires the orderly, rapid and accurate binding of syntaxin-1 to other SNARE proteins, play key roles in triggering fusion. All of these reactions that affect exocytosis under physiological conditions are tightly regulated by multiple factors. Here, we review the current evidence for the involvement of syntaxin-1 in the mechanism of neuroendocrine cell exocytosis, discuss the roles of multiple factors such as proteins, lipids, protein kinases, drugs, and toxins in SNARE complex-mediated membrane fusion, and present an overview of syntaxin-1 mutation-associated diseases with a view to developing novel mechanistic therapeutic targets for the treatment of neuroendocrine disorders.
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Affiliation(s)
- Xinquan Yang
- Anesthesia and Perioperative Medicine laboratory, the Affiliated Lianyungang Hospital of Jiangsu University, Lianyungang, China
| | - Weifeng Tu
- Faculty of Anesthesioloy, Suzhou Hospital Affiliated to Medical School of Nanjing University, Suzhou, China
| | - Xuzhu Gao
- Department of Central Laboratory, Lianyungang Hospital Affiliated to Jiangsu University, Lianyungang, China
| | - Qi Zhang
- Anesthesia and Perioperative Medicine laboratory, the Affiliated Lianyungang Hospital of Jiangsu University, Lianyungang, China
| | - Jinping Guan
- Anesthesia and Perioperative Medicine laboratory, the Affiliated Lianyungang Hospital of Jiangsu University, Lianyungang, China
| | - Junlong Zhang
- Anesthesia and Perioperative Medicine laboratory, the Affiliated Lianyungang Hospital of Jiangsu University, Lianyungang, China
- *Correspondence: Junlong Zhang,
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8
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Munc18-dependent and -independent clustering of syntaxin in the plasma membrane of cultured endocrine cells. Proc Natl Acad Sci U S A 2021; 118:2025748118. [PMID: 34857632 DOI: 10.1073/pnas.2025748118] [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] [Accepted: 10/04/2021] [Indexed: 11/18/2022] Open
Abstract
Syntaxin helps in catalyzing membrane fusion during exocytosis. It also forms clusters in the plasma membrane, where both its transmembrane and SNARE domains are thought to homo-oligomerize. To study syntaxin clustering in live PC12 cells, we labeled granules with neuropeptide-Y-mCherry and syntaxin clusters with syntaxin-1a green fluorescent protein (GFP). Abundant clusters appeared under total internal reflection (TIRF) illumination, and some of them associated with granules ("on-granule clusters"). Syntaxin-1a-GFP or its mutants were expressed at low levels and competed with an excess of endogenous syntaxin for inclusion into clusters. On-granule inclusion was diminished by mutations known to inhibit binding to Munc18-1 in vitro. Knock-down of Munc18-1 revealed Munc18-dependent and -independent on-granule clustering. Clustering was inhibited by mutations expected to break salt bridges between syntaxin's Hb and SNARE domains and was rescued by additional mutations expected to restore them. Most likely, syntaxin is in a closed conformation when it clusters on granules, and its SNARE and Hb domains approach to within atomic distances. Pairwise replacements of Munc18-contacting residues with alanines had only modest effects, except that the pair R114A/I115A essentially abolished on-granule clustering. In summary, an on-granule cluster arises from the specific interaction between a granule and a dense cluster of syntaxin-Munc18-1 complexes. Off-granule clusters, by contrast, were resistant to even the strongest mutations we tried and required neither Munc18-1 nor the presence of a SNARE domain. They may well form through the nonstoichiometric interactions with membrane lipids that others have observed in cell-free systems.
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9
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Mertins J, Finke J, Sies R, Rink KM, Hasenauer J, Lang T. The mesoscale organization of syntaxin 1A and SNAP25 is determined by SNARE-SNARE interactions. eLife 2021; 10:69236. [PMID: 34779769 PMCID: PMC8629428 DOI: 10.7554/elife.69236] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 11/14/2021] [Indexed: 01/01/2023] Open
Abstract
SNARE proteins have been described as the effectors of fusion events in the secretory pathway more than two decades ago. The strong interactions between SNARE domains are clearly important in membrane fusion, but it is unclear whether they are involved in any other cellular processes. Here, we analyzed two classical SNARE proteins, syntaxin 1A and SNAP25. Although they are supposed to be engaged in tight complexes, we surprisingly find them largely segregated in the plasma membrane. Syntaxin 1A only occupies a small fraction of the plasma membrane area. Yet, we find it is able to redistribute the far more abundant SNAP25 on the mesoscale by gathering crowds of SNAP25 molecules onto syntaxin clusters in a SNARE-domain-dependent manner. Our data suggest that SNARE domain interactions are not only involved in driving membrane fusion on the nanoscale, but also play an important role in controlling the general organization of proteins on the mesoscale. Further, we propose these mechanisms preserve active syntaxin 1A–SNAP25 complexes at the plasma membrane.
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Affiliation(s)
- Jasmin Mertins
- Departments of Membrane Biochemistry, Life & Medical Sciences (LIMES) Institute, University of Bonn, Bonn, Germany
| | - Jérôme Finke
- Departments of Membrane Biochemistry, Life & Medical Sciences (LIMES) Institute, University of Bonn, Bonn, Germany
| | - Ricarda Sies
- Departments of Membrane Biochemistry, Life & Medical Sciences (LIMES) Institute, University of Bonn, Bonn, Germany
| | - Kerstin M Rink
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Jan Hasenauer
- Computational Life Sciences, Life & Medical Sciences (LIMES) Institute, University of Bonn, Bonn, Germany.,Interdisciplinary Research Unit Mathematics and Life Sciences, University of Bonn, Bonn, Germany.,Institute of Computational Biology, Helmholtz Center Munich - German Research Center for Environmental Health, Neuherberg, Germany
| | - Thorsten Lang
- Departments of Membrane Biochemistry, Life & Medical Sciences (LIMES) Institute, University of Bonn, Bonn, Germany
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10
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Super-resolution microscopy: a closer look at synaptic dysfunction in Alzheimer disease. Nat Rev Neurosci 2021; 22:723-740. [PMID: 34725519 DOI: 10.1038/s41583-021-00531-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/27/2021] [Indexed: 11/08/2022]
Abstract
The synapse has emerged as a critical neuronal structure in the degenerative process of Alzheimer disease (AD), in which the pathogenic signals of two key players - amyloid-β (Aβ) and tau - converge, thereby causing synaptic dysfunction and cognitive deficits. The synapse presents a dynamic, confined microenvironment in which to explore how key molecules travel, localize, interact and assume different levels of organizational complexity, thereby affecting neuronal function. However, owing to their small size and the diffraction-limited resolution of conventional light microscopic approaches, investigating synaptic structure and dynamics has been challenging. Super-resolution microscopy (SRM) techniques have overcome the resolution barrier and are revolutionizing our quantitative understanding of biological systems in unprecedented spatio-temporal detail. Here we review critical new insights provided by SRM into the molecular architecture and dynamic organization of the synapse and, in particular, the interactions between Aβ and tau in this compartment. We further highlight how SRM can transform our understanding of the molecular pathological mechanisms that underlie AD. The application of SRM for understanding the roles of synapses in AD pathology will provide a stepping stone towards a broader understanding of dysfunction in other subcellular compartments and at cellular and circuit levels in this disease.
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11
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Li M, Oh TJ, Fan H, Diao J, Zhang K. Syntaxin Clustering and Optogenetic Control for Synaptic Membrane Fusion. J Mol Biol 2020; 432:4773-4782. [PMID: 32682743 DOI: 10.1016/j.jmb.2020.07.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 07/05/2020] [Accepted: 07/12/2020] [Indexed: 01/01/2023]
Abstract
Membrane fusion during synaptic transmission mediates the trafficking of chemical signals and neuronal communication. The fast kinetics of membrane fusion on the order of millisecond is precisely regulated by the assembly of SNAREs and accessory proteins. It is believed that the formation of the SNARE complex is a key step during membrane fusion. Little is known, however, about the molecular machinery that mediates the formation of a large pre-fusion complex, including multiple SNAREs and accessory proteins. Syntaxin, a transmembrane protein on the plasma membrane, has been observed to undergo oligomerization to form clusters. Whether this clustering plays a critical role in membrane fusion is poorly understood in live cells. Optogenetics is an emerging biotechnology armed with the capacity to precisely modulate protein-protein interaction in time and space. Here, we propose an experimental scheme that combines optogenetics with single-vesicle membrane fusion, aiming to gain a better understanding of the molecular mechanism by which the syntaxin cluster regulates membrane fusion. We envision that newly developed optogenetic tools could facilitate the mechanistic understanding of synaptic transmission in live cells and animals.
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Affiliation(s)
- Miaoling Li
- Key Laboratory of Medical Electrophysiology of Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Teak-Jung Oh
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Huaxun Fan
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Jiajie Diao
- Department of Cancer Biology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA.
| | - Kai Zhang
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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12
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Finke J, Mikuličić S, Loster AL, Gawlitza A, Florin L, Lang T. Anatomy of a viral entry platform differentially functionalized by integrins α3 and α6. Sci Rep 2020; 10:5356. [PMID: 32210347 PMCID: PMC7093462 DOI: 10.1038/s41598-020-62202-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 03/10/2020] [Indexed: 12/26/2022] Open
Abstract
During cell invasion, human papillomaviruses use large CD151 patches on the cell surface. Here, we studied whether these patches are defined architectures with features for virus binding and/or internalization. Super-resolution microscopy reveals that the patches are assemblies of closely associated nanoclusters of CD151, integrin α3 and integrin α6. Integrin α6 is required for virus attachment and integrin α3 for endocytosis. We propose that CD151 organizes viral entry platforms with different types of integrin clusters for different functionalities. Since numerous viruses use tetraspanin patches, we speculate that this building principle is a blueprint for cell-surface architectures utilized by viral particles.
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Affiliation(s)
- Jérôme Finke
- Department of Membrane Biochemistry, Life & Medical Sciences (LIMES) Institute, University of Bonn, Carl-Troll-Straße 31, 53115, Bonn, Germany
| | - Snježana Mikuličić
- Institute for Virology and Research Center for Immunotherapy (FZI), University Medical Center of the Johannes Gutenberg University Mainz, Obere Zahlbacher Straße 67, 55131, Mainz, Germany
| | - Anna-Lena Loster
- Institute for Virology and Research Center for Immunotherapy (FZI), University Medical Center of the Johannes Gutenberg University Mainz, Obere Zahlbacher Straße 67, 55131, Mainz, Germany
| | - Alexander Gawlitza
- Institute for Virology and Research Center for Immunotherapy (FZI), University Medical Center of the Johannes Gutenberg University Mainz, Obere Zahlbacher Straße 67, 55131, Mainz, Germany
| | - Luise Florin
- Institute for Virology and Research Center for Immunotherapy (FZI), University Medical Center of the Johannes Gutenberg University Mainz, Obere Zahlbacher Straße 67, 55131, Mainz, Germany
| | - Thorsten Lang
- Department of Membrane Biochemistry, Life & Medical Sciences (LIMES) Institute, University of Bonn, Carl-Troll-Straße 31, 53115, Bonn, Germany.
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13
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Phase separation and clustering of an ABC transporter in Mycobacterium tuberculosis. Proc Natl Acad Sci U S A 2019; 116:16326-16331. [PMID: 31366629 DOI: 10.1073/pnas.1820683116] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Phase separation drives numerous cellular processes, ranging from the formation of membrane-less organelles to the cooperative assembly of signaling proteins. Features such as multivalency and intrinsic disorder that enable condensate formation are found not only in cytosolic and nuclear proteins, but also in membrane-associated proteins. The ABC transporter Rv1747, which is important for Mycobacterium tuberculosis (Mtb) growth in infected hosts, has a cytoplasmic regulatory module consisting of 2 phosphothreonine-binding Forkhead-associated domains joined by an intrinsically disordered linker with multiple phospho-acceptor threonines. Here we demonstrate that the regulatory modules of Rv1747 and its homolog in Mycobacterium smegmatis form liquid-like condensates as a function of concentration and phosphorylation. The serine/threonine kinases and sole phosphatase of Mtb tune phosphorylation-enhanced phase separation and differentially colocalize with the resulting condensates. The Rv1747 regulatory module also phase-separates on supported lipid bilayers and forms dynamic foci when expressed heterologously in live yeast and M. smegmatis cells. Consistent with these observations, single-molecule localization microscopy reveals that the endogenous Mtb transporter forms higher-order clusters within the Mycobacterium membrane. Collectively, these data suggest a key role for phase separation in the function of these mycobacterial ABC transporters and their regulation via intracellular signaling.
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Padmanabhan P, Bademosi AT, Kasula R, Lauwers E, Verstreken P, Meunier FA. Need for speed: Super-resolving the dynamic nanoclustering of syntaxin-1 at exocytic fusion sites. Neuropharmacology 2019; 169:107554. [PMID: 30826343 DOI: 10.1016/j.neuropharm.2019.02.036] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 02/21/2019] [Accepted: 02/27/2019] [Indexed: 01/08/2023]
Abstract
Communication between cells relies on regulated exocytosis, a multi-step process that involves the docking, priming and fusion of vesicles with the plasma membrane, culminating in the release of neurotransmitters and hormones. Key proteins and lipids involved in exocytosis are subjected to Brownian movement and constantly switch between distinct motion states which are governed by short-lived molecular interactions. Critical biochemical reactions between exocytic proteins that occur in the confinement of nanodomains underpin the precise sequence of priming steps which leads to the fusion of vesicles. The advent of super-resolution microscopy techniques has provided the means to visualize individual molecules on the plasma membrane with high spatiotemporal resolution in live cells. These techniques are revealing a highly dynamic nature of the nanoscale organization of the exocytic machinery. In this review, we focus on soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) syntaxin-1, which mediates vesicular fusion. Syntaxin-1 is highly mobile at the plasma membrane, and its inherent speed allows fast assembly and disassembly of syntaxin-1 nanoclusters which are associated with exocytosis. We reflect on recent studies which have revealed the mechanisms regulating syntaxin-1 nanoclustering on the plasma membrane and draw inferences on the effect of synaptic activity, phosphoinositides, N-ethylmaleimide-sensitive factor (NSF), α-soluble NSF attachment protein (α-SNAP) and SNARE complex assembly on the dynamic nanoscale organization of syntaxin-1. This article is part of the special issue entitled 'Mobility and trafficking of neuronal membrane proteins'.
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Affiliation(s)
- Pranesh Padmanabhan
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Queensland, Australia
| | - Adekunle T Bademosi
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Queensland, Australia
| | - Ravikiran Kasula
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Queensland, Australia
| | - Elsa Lauwers
- VIB-KU Leuven Center for Brain & Disease Research, 3000 Leuven, Belgium; Department of Neurosciences and Leuven Brain Institute, KU Leuven, 3000 Leuven, Belgium
| | - Patrik Verstreken
- VIB-KU Leuven Center for Brain & Disease Research, 3000 Leuven, Belgium; Department of Neurosciences and Leuven Brain Institute, KU Leuven, 3000 Leuven, Belgium
| | - Frédéric A Meunier
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Queensland, Australia.
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Abstract
Plasma membrane proteins organize into structures named compartments, microdomains, rafts, phases, crowds, or clusters. These structures are often smaller than 100 nm in diameter. Despite their importance in many cellular functions, little is known about their inner organization. For instance, how densely are molecules packed? Being aware of the protein compaction may contribute to our general understanding of why such structures exist and how they execute their functions. In this study, we have investigated plasma membrane crowds formed by the amyloid precursor protein (APP), a protein well known for its involvement in Alzheimer's disease. By combining biochemical experiments with conventional and super-resolution stimulated emission depletion microscopy, we quantitatively determined the protein packing density within APP crowds. We found that crowds occurring with reasonable frequency contain between 20 and 30 molecules occupying a spherical area with a diameter between 65 and 85 nm. Additionally, we found the vast majority of plasmalemmal APP residing in these crowds. The model suggests a high molecular density of protein material within plasmalemmal APP crowds. This should affect the protein's biochemical accessibility and processing by nonpathological α-secretases. As clustering of APP is a prerequisite for endocytic entry into the pathological processing pathway, elucidation of the packing density also provides a deeper understanding of this part of APP's life cycle.
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Wijesooriya CS, Nyamekye CKA, Smith EA. Optical Imaging of the Nanoscale Structure and Dynamics of Biological Membranes. Anal Chem 2018; 91:425-440. [DOI: 10.1021/acs.analchem.8b04755] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
| | - Charles K. A. Nyamekye
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
- The Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50011, United States
| | - Emily A. Smith
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
- The Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50011, United States
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A Rationale for Mesoscopic Domain Formation in Biomembranes. Biomolecules 2018; 8:biom8040104. [PMID: 30274275 PMCID: PMC6316292 DOI: 10.3390/biom8040104] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 09/04/2018] [Accepted: 09/06/2018] [Indexed: 12/25/2022] Open
Abstract
Cell plasma membranes display a dramatically rich structural complexity characterized by functional sub-wavelength domains with specific lipid and protein composition. Under favorable experimental conditions, patterned morphologies can also be observed in vitro on model systems such as supported membranes or lipid vesicles. Lipid mixtures separating in liquid-ordered and liquid-disordered phases below a demixing temperature play a pivotal role in this context. Protein-protein and protein-lipid interactions also contribute to membrane shaping by promoting small domains or clusters. Such phase separations displaying characteristic length-scales falling in-between the nanoscopic, molecular scale on the one hand and the macroscopic scale on the other hand, are named mesophases in soft condensed matter physics. In this review, we propose a classification of the diverse mechanisms leading to mesophase separation in biomembranes. We distinguish between mechanisms relying upon equilibrium thermodynamics and those involving out-of-equilibrium mechanisms, notably active membrane recycling. In equilibrium, we especially focus on the many mechanisms that dwell on an up-down symmetry breaking between the upper and lower bilayer leaflets. Symmetry breaking is an ubiquitous mechanism in condensed matter physics at the heart of several important phenomena. In the present case, it can be either spontaneous (domain buckling) or explicit, i.e., due to an external cause (global or local vesicle bending properties). Whenever possible, theoretical predictions and simulation results are confronted to experiments on model systems or living cells, which enables us to identify the most realistic mechanisms from a biological perspective.
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18
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Abstract
Phosphoinositides (PtdIns) play important roles in exocytosis and are thought to regulate secretory granule docking by co-clustering with the SNARE protein syntaxin to form a docking receptor in the plasma membrane. Here we tested this idea by high-resolution total internal reflection imaging of EGFP-labeled PtdIns markers or syntaxin-1 at secretory granule release sites in live insulin-secreting cells. In intact cells, PtdIns markers distributed evenly across the plasma membrane with no preference for granule docking sites. In contrast, syntaxin-1 was found clustered in the plasma membrane, mostly beneath docked granules. We also observed rapid accumulation of syntaxin-1 at sites where granules arrived to dock. Acute depletion of plasma membrane phosphatidylinositol (4,5) bisphosphate (PtdIns(4,5)P2 ) by recruitment of a 5'-phosphatase strongly inhibited Ca2+ -dependent exocytosis, but had no effect on docked granules or the distribution and clustering of syntaxin-1. Cell permeabilization by α-toxin or formaldehyde-fixation caused PtdIns marker to slowly cluster, in part near docked granules. In summary, our data indicate that PtdIns(4,5)P2 accelerates granule priming, but challenge a role of PtdIns in secretory granule docking or clustering of syntaxin-1 at the release site.
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Affiliation(s)
| | - Nikhil R Gandasi
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Sebastian Barg
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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Bademosi AT, Steeves J, Karunanithi S, Zalucki OH, Gormal RS, Liu S, Lauwers E, Verstreken P, Anggono V, Meunier FA, van Swinderen B. Trapping of Syntaxin1a in Presynaptic Nanoclusters by a Clinically Relevant General Anesthetic. Cell Rep 2018; 22:427-440. [DOI: 10.1016/j.celrep.2017.12.054] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 10/27/2017] [Accepted: 12/15/2017] [Indexed: 12/12/2022] Open
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