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Kenworthy AK. The building blocks of caveolae revealed: caveolins finally take center stage. Biochem Soc Trans 2023; 51:855-869. [PMID: 37082988 DOI: 10.1042/bst20221298] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 04/07/2023] [Accepted: 04/14/2023] [Indexed: 04/22/2023]
Abstract
The ability of cells to divide, migrate, relay signals, sense mechanical stimuli, and respond to stress all rely on nanoscale invaginations of the plasma membrane known as caveolae. The caveolins, a family of monotopic membrane proteins, form the inner layer of the caveolar coat. Caveolins have long been implicated in the generation of membrane curvature, in addition to serving as scaffolds for signaling proteins. Until recently, however, the molecular architecture of caveolins was unknown, making it impossible to understand how they operate at a mechanistic level. Over the past year, two independent lines of evidence - experimental and computational - have now converged to provide the first-ever glimpse into the structure of the oligomeric caveolin complexes that function as the building blocks of caveolae. Here, we summarize how these discoveries are transforming our understanding of this long-enigmatic protein family and their role in caveolae assembly and function. We present new models inspired by the structure for how caveolins oligomerize, remodel membranes, interact with their binding partners, and reorganize when mutated. Finally, we discuss emerging insights into structural differences among caveolin family members that enable them to support the proper functions of diverse tissues and organisms.
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Affiliation(s)
- Anne K Kenworthy
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, U.S.A
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, U.S.A
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2
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Wan W, Dong H, Lai DH, Yang J, He K, Tang X, Liu Q, Hide G, Zhu XQ, Sibley LD, Lun ZR, Long S. The Toxoplasma micropore mediates endocytosis for selective nutrient salvage from host cell compartments. Nat Commun 2023; 14:977. [PMID: 36813769 PMCID: PMC9947163 DOI: 10.1038/s41467-023-36571-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 02/03/2023] [Indexed: 02/24/2023] Open
Abstract
Apicomplexan parasite growth and replication relies on nutrient acquisition from host cells, in which intracellular multiplication occurs, yet the mechanisms that underlie the nutrient salvage remain elusive. Numerous ultrastructural studies have documented a plasma membrane invagination with a dense neck, termed the micropore, on the surface of intracellular parasites. However, the function of this structure remains unknown. Here we validate the micropore as an essential organelle for endocytosis of nutrients from the host cell cytosol and Golgi in the model apicomplexan Toxoplasma gondii. Detailed analyses demonstrated that Kelch13 is localized at the dense neck of the organelle and functions as a protein hub at the micropore for endocytic uptake. Intriguingly, maximal activity of the micropore requires the ceramide de novo synthesis pathway in the parasite. Thus, this study provides insights into the machinery underlying acquisition of host cell-derived nutrients by apicomplexan parasites that are otherwise sequestered from host cell compartments.
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Affiliation(s)
- Wenyan Wan
- National Key Laboratory of Veterinary Public Health Security and School of Veterinary Medicine, China Agricultural University, 100193, Beijing, China
| | - Hui Dong
- National Key Laboratory of Veterinary Public Health Security and School of Veterinary Medicine, China Agricultural University, 100193, Beijing, China
| | - De-Hua Lai
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510275, China
| | - Jiong Yang
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510275, China
| | - Kai He
- National Key Laboratory of Veterinary Public Health Security and School of Veterinary Medicine, China Agricultural University, 100193, Beijing, China
| | - Xiaoyan Tang
- National Key Laboratory of Veterinary Public Health Security and School of Veterinary Medicine, China Agricultural University, 100193, Beijing, China
| | - Qun Liu
- National Key Laboratory of Veterinary Public Health Security and School of Veterinary Medicine, China Agricultural University, 100193, Beijing, China
| | - Geoff Hide
- Biomedical Research and Innovation Centre and Environmental Research and Innovation Centre, School of Science, Engineering and Environment, University of Salford, Salford, M5 4WT, UK
| | - Xing-Quan Zhu
- College of Veterinary Medicine, Shanxi Agricultural University, Taigu, 030801, Shanxi, China
| | - L David Sibley
- Department of Molecular Microbiology, Washington University School of Medicine in Saint Louis, Saint Louis, MO, 63110-1093, USA
| | - Zhao-Rong Lun
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510275, China
| | - Shaojun Long
- National Key Laboratory of Veterinary Public Health Security and School of Veterinary Medicine, China Agricultural University, 100193, Beijing, China.
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Flourieusse A, Bourgeois P, Schenckbecher E, Palvair J, Legrand D, Labbé C, Bescond T, Avoscan L, Orlowski S, Rouleau A, Frelet-Barrand A. Formation of intracellular vesicles within the Gram+ Lactococcus lactis induced by the overexpression of Caveolin-1β. Microb Cell Fact 2022; 21:239. [PMCID: PMC9670397 DOI: 10.1186/s12934-022-01944-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 10/02/2022] [Indexed: 11/18/2022] Open
Abstract
Abstract
Background
Caveolae are invaginated plasma membrane domains of 50–100 nm in diameter involved in many important physiological functions in eukaryotic cells. They are composed of different proteins, including the membrane-embedded caveolins and the peripheric cavins. Caveolin-1 has already been expressed in various expression systems (E. coli, insect cells, Toxoplasma gondii, cell-free system), generating intracellular caveolin-enriched vesicles in E. coli, insect cells and T. gondii. These systems helped to understand the protein insertion within the membrane and its oligomerization. There is still need for fundamental insights into the formation of specific domains on membrane, the deformation of a biological membrane driven by caveolin-1, the organization of a caveolar coat, and the requirement of specific lipids and proteins during the process. The aim of this study was to test whether the heterologously expressed caveolin-1β was able to induce the formation of intracellular vesicles within a Gram+ bacterium, Lactococcus lactis, since it displays a specific lipid composition different from E. coli and appears to emerge as a good alternative to E. coli for efficient overexpression of various membrane proteins.
Results
Recombinant bacteria transformed with the plasmid pNZ-HTC coding for the canine isoform of caveolin-1β were shown to produce caveolin-1β, in its functional oligomeric form, at a high expression level unexpected for an eukaryotic membrane protein. Electron microscopy revealed several intracellular vesicles from 30 to 60 nm, a size comparable to E. coli h-caveolae, beneath the plasma membrane of the overexpressing bacteria, showing that caveolin-1β is sufficient to induce membrane vesiculation. Immunolabelling studies showed antibodies on such neo-formed intracellular vesicles, but none on plasma membrane. Density gradient fractionation allowed the correlation between detection of oligomers on Western blot and appearance of vesicles measurable by DLS, showing the requirement of caveolin-1β oligomerization for vesicle formation.
Conclusions
Lactococcus lactis cells can heterologously overexpress caveolin-1β, generating caveolin-1β enriched intracellular neo-formed vesicles. These vesicles might be useful for potential co-expression of membrane proteins of pharmaceutical interest for their simplified functional characterization.
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Zhang Y, Zhang X, Kong W, Wang S. Reconstitution of Caveolin-1 into Artificial Lipid Membrane: Characterization by Transmission Electron Microscopy and Solid-State Nuclear Magnetic Resonance. Molecules 2021; 26:molecules26206201. [PMID: 34684779 PMCID: PMC8539922 DOI: 10.3390/molecules26206201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 10/09/2021] [Accepted: 10/11/2021] [Indexed: 12/26/2022] Open
Abstract
Caveolin-1 (CAV1), a membrane protein that is necessary for the formation and maintenance of caveolae, is a promising drug target for the therapy of various diseases, such as cancer, diabetes, and liver fibrosis. The biology and pathology of caveolae have been widely investigated; however, very little information about the structural features of full-length CAV1 is available, as well as its biophysical role in reshaping the cellular membrane. Here, we established a method, with high reliability and reproducibility, for the expression and purification of CAV1. Amyloid-like properties of CAV1 and its C-terminal peptide CAV1(168-178) suggest a structural basis for the short linear CAV1 assemblies that have been recently observed in caveolin polyhedral cages in Escherichia coli (E. coli). Reconstitution of CAV1 into artificial lipid membranes induces a caveolae-like membrane curvature. Structural characterization of CAV1 in the membrane by solid-state nuclear magnetic resonance (ssNMR) indicate that it is largely α-helical, with very little β-sheet content. Its scaffolding domain adopts a α-helical structure as identified by chemical shift analysis of threonine (Thr). Taken together, an in vitro model was developed for the CAV1 structural study, which will further provide meaningful evidences for the design and screening of bioactive compounds targeting CAV1.
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Affiliation(s)
- Yanli Zhang
- Department of Pharmacy, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Jinan 250012, China;
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, NE 68198, USA;
| | - Xinyan Zhang
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, NE 68198, USA;
| | - Wenru Kong
- School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China;
| | - Shuqi Wang
- School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China;
- Correspondence: ; Tel.: +86-0531-88382014
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McGovern OL, Rivera-Cuevas Y, Carruthers VB. Emerging Mechanisms of Endocytosis in Toxoplasma gondii. Life (Basel) 2021; 11:life11020084. [PMID: 33503859 PMCID: PMC7911406 DOI: 10.3390/life11020084] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 01/19/2021] [Accepted: 01/20/2021] [Indexed: 02/07/2023] Open
Abstract
Eukaryotes critically rely on endocytosis of autologous and heterologous material to maintain homeostasis and to proliferate. Although mechanisms of endocytosis have been extensively identified in mammalian and plant systems along with model systems including budding yeast, relatively little is known about endocytosis in protozoan parasites including those belonging to the phylum Apicomplexa. Whereas it has been long established that the apicomplexan agents of malaria (Plasmodium spp.) internalize and degrade hemoglobin from infected red blood cells to acquire amino acids for growth, that the related and pervasive parasite Toxoplasma gondii has a functional and active endocytic system was only recently discovered. Here we discuss emerging and hypothesized mechanisms of endocytosis in Toxoplasma gondii with reference to model systems and malaria parasites. Establishing a framework for potential mechanisms of endocytosis in Toxoplasma gondii will help guide future research aimed at defining the molecular basis and biological relevance of endocytosis in this tractable and versatile parasite.
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Sangaré LO, Alayi TD, Westermann B, Hovasse A, Sindikubwabo F, Callebaut I, Werkmeister E, Lafont F, Slomianny C, Hakimi MA, Van Dorsselaer A, Schaeffer-Reiss C, Tomavo S. Unconventional endosome-like compartment and retromer complex in Toxoplasma gondii govern parasite integrity and host infection. Nat Commun 2016; 7:11191. [PMID: 27064065 PMCID: PMC4831018 DOI: 10.1038/ncomms11191] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 02/26/2016] [Indexed: 12/31/2022] Open
Abstract
Membrane trafficking pathways play critical roles in Apicomplexa, a phylum of protozoan parasites that cause life-threatening diseases worldwide. Here we report the first retromer-trafficking interactome in Toxoplasma gondii. This retromer complex includes a trimer Vps35-Vps26-Vps29 core complex that serves as a hub for the endosome-like compartment and parasite-specific proteins. Conditional ablation of TgVps35 reveals that the retromer complex is crucial for the biogenesis of secretory organelles and for maintaining parasite morphology. We identify TgHP12 as a parasite-specific and retromer-associated protein with functions unrelated to secretory organelle formation. Furthermore, the major facilitator superfamily homologue named TgHP03, which is a multiple spanning and ligand transmembrane transporter, is maintained at the parasite membrane by retromer-mediated endocytic recycling. Thus, our findings highlight that both evolutionarily conserved and unconventional proteins act in concert in T. gondii by controlling retrograde transport that is essential for parasite integrity and host infection.
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Affiliation(s)
- Lamba Omar Sangaré
- Center for Infection and Immunity of Lille, INSERM U 1019, CNRS UMR 8204, Institut Pasteur de Lille, Université de Lille, 59000 Lille, France
| | - Tchilabalo Dilezitoko Alayi
- Laboratory of Bio-Organic Mass Spectrometry, IPHC, CNRS UMR 7178, Université de Strasbourg, 67087 Strasbourg, France
- Plateforme de Protéomique et des Peptides Modifiés (P3M), Institut Pasteur de Lille, CNRS, Université de Lille, 59000 Lille, France
| | - Benoit Westermann
- Laboratory of Bio-Organic Mass Spectrometry, IPHC, CNRS UMR 7178, Université de Strasbourg, 67087 Strasbourg, France
| | - Agnes Hovasse
- Laboratory of Bio-Organic Mass Spectrometry, IPHC, CNRS UMR 7178, Université de Strasbourg, 67087 Strasbourg, France
| | | | - Isabelle Callebaut
- CNRS UMR7590, Sorbonne Universités, Université Pierre et Marie Curie-Paris 6, MNHN, IRD-IUC, Paris 75005, France
| | | | - Frank Lafont
- Bioimaging Platform, IBL, CNRS, Université de Lille, 59000 Lille, France
| | - Christian Slomianny
- Laboratory of Cell Physiology, INSERM U 1003, Université de Lille, 59655 Villeneuve d'Ascq, France
| | | | - Alain Van Dorsselaer
- Laboratory of Bio-Organic Mass Spectrometry, IPHC, CNRS UMR 7178, Université de Strasbourg, 67087 Strasbourg, France
| | - Christine Schaeffer-Reiss
- Laboratory of Bio-Organic Mass Spectrometry, IPHC, CNRS UMR 7178, Université de Strasbourg, 67087 Strasbourg, France
| | - Stanislas Tomavo
- Center for Infection and Immunity of Lille, INSERM U 1019, CNRS UMR 8204, Institut Pasteur de Lille, Université de Lille, 59000 Lille, France
- Plateforme de Protéomique et des Peptides Modifiés (P3M), Institut Pasteur de Lille, CNRS, Université de Lille, 59000 Lille, France
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Exploitation of auxotrophies and metabolic defects in Toxoplasma as therapeutic approaches. Int J Parasitol 2014; 44:109-20. [DOI: 10.1016/j.ijpara.2013.09.003] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2013] [Revised: 09/22/2013] [Accepted: 09/22/2013] [Indexed: 12/30/2022]
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Tomavo S, Slomianny C, Meissner M, Carruthers VB. Protein trafficking through the endosomal system prepares intracellular parasites for a home invasion. PLoS Pathog 2013; 9:e1003629. [PMID: 24204248 PMCID: PMC3812028 DOI: 10.1371/journal.ppat.1003629] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Toxoplasma (toxoplasmosis) and Plasmodium (malaria) use unique secretory organelles for migration, cell invasion, manipulation of host cell functions, and cell egress. In particular, the apical secretory micronemes and rhoptries of apicomplexan parasites are essential for successful host infection. New findings reveal that the contents of these organelles, which are transported through the endoplasmic reticulum (ER) and Golgi, also require the parasite endosome-like system to access their respective organelles. In this review, we discuss recent findings that demonstrate that these parasites reduced their endosomal system and modified classical regulators of this pathway for the biogenesis of apical organelles.
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Affiliation(s)
- Stanislas Tomavo
- Center for Infection and Immunity of Lille, CNRS UMR 8204, INSERM U 1019, Institut Pasteur de Lille, Université Lille Nord de France, Lille, France
- * E-mail:
| | - Christian Slomianny
- Laboratory of Cell Physiology, INSERM U 1003, Université Lille Nord de France, Villeneuve d'Ascq, Lille, France
| | - Markus Meissner
- Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Vern B. Carruthers
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
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The role of clathrin in post-Golgi trafficking in Toxoplasma gondii. PLoS One 2013; 8:e77620. [PMID: 24147036 PMCID: PMC3795686 DOI: 10.1371/journal.pone.0077620] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Accepted: 09/13/2013] [Indexed: 11/19/2022] Open
Abstract
Apicomplexan parasites are single eukaryotic cells with a highly polarised secretory system that contains unique secretory organelles (micronemes and rhoptries) that are required for host cell invasion. In contrast, the role of the endosomal system is poorly understood in these parasites. With many typical endocytic factors missing, we speculated that endocytosis depends exclusively on a clathrin-mediated mechanism. Intriguingly, in Toxoplasma gondii we were only able to observe the endogenous clathrin heavy chain 1 (CHC1) at the Golgi, but not at the parasite surface. For the functional characterisation of Toxoplasma gondii CHC1 we generated parasite mutants conditionally expressing the dominant negative clathrin Hub fragment and demonstrate that CHC1 is essential for vesicle formation at the trans-Golgi network. Consequently, the functional ablation of CHC1 results in Golgi aberrations, a block in the biogenesis of the unique secretory microneme and rhoptry organelles, and of the pellicle. However, we found no morphological evidence for clathrin mediating endocytosis in these parasites and speculate that they remodelled their vesicular trafficking system to adapt to an intracellular lifestyle.
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