1
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Raab JE, Hamilton DJ, Harju TB, Huynh TN, Russo BC. Pushing boundaries: mechanisms enabling bacterial pathogens to spread between cells. Infect Immun 2024:e0052423. [PMID: 38661369 DOI: 10.1128/iai.00524-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2024] Open
Abstract
For multiple intracellular bacterial pathogens, the ability to spread directly into adjacent epithelial cells is an essential step for disease in humans. For pathogens such as Shigella, Listeria, Rickettsia, and Burkholderia, this intercellular movement frequently requires the pathogens to manipulate the host actin cytoskeleton and deform the plasma membrane into structures known as protrusions, which extend into neighboring cells. The protrusion is then typically resolved into a double-membrane vacuole (DMV) from which the pathogen quickly escapes into the cytosol, where additional rounds of intercellular spread occur. Significant progress over the last few years has begun to define the mechanisms by which intracellular bacterial pathogens spread. This review highlights the interactions of bacterial and host factors that drive mechanisms required for intercellular spread with a focus on how protrusion structures form and resolve.
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Affiliation(s)
- Julie E Raab
- Department of Immunology and Microbiology, School of Medicine, University of Colorado-Anschutz Medical Campus, Denver, Colorado, USA
| | - Desmond J Hamilton
- Department of Immunology and Microbiology, School of Medicine, University of Colorado-Anschutz Medical Campus, Denver, Colorado, USA
| | - Tucker B Harju
- Department of Immunology and Microbiology, School of Medicine, University of Colorado-Anschutz Medical Campus, Denver, Colorado, USA
| | - Thao N Huynh
- Department of Immunology and Microbiology, School of Medicine, University of Colorado-Anschutz Medical Campus, Denver, Colorado, USA
| | - Brian C Russo
- Department of Immunology and Microbiology, School of Medicine, University of Colorado-Anschutz Medical Campus, Denver, Colorado, USA
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2
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Suri A, Hu KKY, Younas T, Dumsday G, Haritos VS. Functionalizing Yeast Lipid Droplets as Versatile Biomaterials. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2308463. [PMID: 38566530 DOI: 10.1002/smll.202308463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2023] [Revised: 01/02/2024] [Indexed: 04/04/2024]
Abstract
Lipid droplets (LD) are dynamic cellular organelles of ≈1 µm diameter in yeast where a neutral lipid core is surrounded by a phospholipid monolayer and attendant proteins. Beyond the storage of lipids, opportunities for LD engineering remain underdeveloped but they show excellent potential as new biomaterials. In this research, LD from yeast Saccharomyces cerevisiae is engineered to display mCherry fluorescent protein, Halotag ligand binding protein, plasma membrane binding v-SNARE protein, and carbonic anhydrase enzyme via linkage to oleosin, an LD anchoring protein. Each protein-oleosin fusion is coded via a single gene construct. The expressed fusion proteins are specifically displayed on LD and their functions can be assessed within cells by fluorescence confocal microscopy, TEM, and as isolated materials via AFM, flow cytometry, spectrophotometry, and by enzyme activity assay. LD isolated from the cell are shown to be robust and stabilize proteins anchored into them. These engineered LD function as reporters, bind specific ligands, guide LD and their attendant proteins into union with the plasma membrane, and catalyze reactions. Here, engineered LD functions are extended well beyond traditional lipid storage toward new material applications aided by a versatile oleosin platform anchored into LD and displaying linked proteins.
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Affiliation(s)
- Ankita Suri
- Department of Chemical and Biological Engineering, Monash University, Clayton, 3800, Australia
- CSIRO Black Mountain, 2-40 Clunies Ross Street, Acton, ACT, 2601, Australia
| | - Kevin K Y Hu
- Department of Chemical and Biological Engineering, Monash University, Clayton, 3800, Australia
| | - Tayyaba Younas
- Department of Chemical and Biological Engineering, Monash University, Clayton, 3800, Australia
| | - Geoff Dumsday
- CSIRO Clayton, Research Way, Clayton, Victoria, 3168, Australia
| | - Victoria S Haritos
- Department of Chemical and Biological Engineering, Monash University, Clayton, 3800, Australia
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3
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Dennis C, Pouchin P, Richard G, Mirouse V. Basement membrane diversification relies on two competitive secretory routes defined by Rab10 and Rab8 and modulated by dystrophin and the exocyst complex. PLoS Genet 2024; 20:e1011169. [PMID: 38437244 PMCID: PMC10939200 DOI: 10.1371/journal.pgen.1011169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 03/14/2024] [Accepted: 02/05/2024] [Indexed: 03/06/2024] Open
Abstract
The basement membrane (BM) is an essential structural element of tissues, and its diversification participates in organ morphogenesis. However, the traffic routes associated with BM formation and the mechanistic modulations explaining its diversification are still poorly understood. Drosophila melanogaster follicular epithelium relies on a BM composed of oriented BM fibrils and a more homogenous matrix. Here, we determined the specific molecular identity and cell exit sites of BM protein secretory routes. First, we found that Rab10 and Rab8 define two parallel routes for BM protein secretion. When both routes were abolished, BM production was fully blocked; however, genetic interactions revealed that these two routes competed. Rab10 promoted lateral and planar-polarized secretion, whereas Rab8 promoted basal secretion, leading to the formation of BM fibrils and homogenous BM, respectively. We also found that the dystrophin-associated protein complex (DAPC) and Rab10 were both present in a planar-polarized tubular compartment containing BM proteins. DAPC was essential for fibril formation and sufficient to reorient secretion towards the Rab10 route. Moreover, we identified a dual function for the exocyst complex in this context. First, the Exo70 subunit directly interacted with dystrophin to limit its planar polarization. Second, the exocyst complex was also required for the Rab8 route. Altogether, these results highlight important mechanistic aspects of BM protein secretion and illustrate how BM diversity can emerge from the spatial control of distinct traffic routes.
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Affiliation(s)
- Cynthia Dennis
- Université Clermont Auvergne, Institute of Genetics, Reproduction and Development (iGReD), UMR CNRS 6293-INSERM U1103, Faculté de Médecine, Clermont-Ferrand, France
| | - Pierre Pouchin
- Université Clermont Auvergne, Institute of Genetics, Reproduction and Development (iGReD), UMR CNRS 6293-INSERM U1103, Faculté de Médecine, Clermont-Ferrand, France
| | - Graziella Richard
- Université Clermont Auvergne, Institute of Genetics, Reproduction and Development (iGReD), UMR CNRS 6293-INSERM U1103, Faculté de Médecine, Clermont-Ferrand, France
| | - Vincent Mirouse
- Université Clermont Auvergne, Institute of Genetics, Reproduction and Development (iGReD), UMR CNRS 6293-INSERM U1103, Faculté de Médecine, Clermont-Ferrand, France
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4
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Fernández-Infante C, Hernández-Cano L, Herranz Ó, Berrocal P, Sicilia-Navarro C, González-Porras JR, Bastida JM, Porras A, Guerrero C. Platelet C3G: a key player in vesicle exocytosis, spreading and clot retraction. Cell Mol Life Sci 2024; 81:84. [PMID: 38345631 PMCID: PMC10861696 DOI: 10.1007/s00018-023-05109-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 12/22/2023] [Accepted: 12/23/2023] [Indexed: 02/15/2024]
Abstract
C3G is a Rap1 GEF that plays a pivotal role in platelet-mediated processes such as angiogenesis, tumor growth, and metastasis by modulating the platelet secretome. Here, we explore the mechanisms through which C3G governs platelet secretion. For this, we utilized animal models featuring either overexpression or deletion of C3G in platelets, as well as PC12 cell clones expressing C3G mutants. We found that C3G specifically regulates α-granule secretion via PKCδ, but it does not affect δ-granules or lysosomes. C3G activated RalA through a GEF-dependent mechanism, facilitating vesicle docking, while interfering with the formation of the trans-SNARE complex, thereby restricting vesicle fusion. Furthermore, C3G promotes the formation of lamellipodia during platelet spreading on specific substrates by enhancing actin polymerization via Src and Rac1-Arp2/3 pathways, but not Rap1. Consequently, C3G deletion in platelets favored kiss-and-run exocytosis. C3G also controlled granule secretion in PC12 cells, including pore formation. Additionally, C3G-deficient platelets exhibited reduced phosphatidylserine exposure, resulting in decreased thrombin generation, which along with defective actin polymerization and spreading, led to impaired clot retraction. In summary, platelet C3G plays a dual role by facilitating platelet spreading and clot retraction through the promotion of outside-in signaling while concurrently downregulating α-granule secretion by restricting granule fusion.
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Affiliation(s)
- Cristina Fernández-Infante
- Instituto de Biología Molecular y Celular del Cáncer (IMBCC), USAL-CSIC, Centro de Investigación del Cáncer, Campus Unamuno S/N, Salamanca, Spain
- Instituto de Investigación Biomédica de Salamanca (IBSAL), Salamanca, Spain
- Departamento de Medicina, Universidad de Salamanca, Salamanca, Spain
| | - Luis Hernández-Cano
- Instituto de Biología Molecular y Celular del Cáncer (IMBCC), USAL-CSIC, Centro de Investigación del Cáncer, Campus Unamuno S/N, Salamanca, Spain
- Instituto de Investigación Biomédica de Salamanca (IBSAL), Salamanca, Spain
- Departamento de Medicina, Universidad de Salamanca, Salamanca, Spain
| | - Óscar Herranz
- Instituto de Biología Molecular y Celular del Cáncer (IMBCC), USAL-CSIC, Centro de Investigación del Cáncer, Campus Unamuno S/N, Salamanca, Spain
- Instituto de Investigación Biomédica de Salamanca (IBSAL), Salamanca, Spain
- Departamento de Medicina, Universidad de Salamanca, Salamanca, Spain
| | - Pablo Berrocal
- Instituto de Biología Molecular y Celular del Cáncer (IMBCC), USAL-CSIC, Centro de Investigación del Cáncer, Campus Unamuno S/N, Salamanca, Spain
- Instituto de Investigación Biomédica de Salamanca (IBSAL), Salamanca, Spain
- Departamento de Medicina, Universidad de Salamanca, Salamanca, Spain
| | - Carmen Sicilia-Navarro
- Instituto de Biología Molecular y Celular del Cáncer (IMBCC), USAL-CSIC, Centro de Investigación del Cáncer, Campus Unamuno S/N, Salamanca, Spain
- Instituto de Investigación Biomédica de Salamanca (IBSAL), Salamanca, Spain
- Departamento de Medicina, Universidad de Salamanca, Salamanca, Spain
| | - José Ramón González-Porras
- Instituto de Investigación Biomédica de Salamanca (IBSAL), Salamanca, Spain
- Departamento de Medicina, Universidad de Salamanca, Salamanca, Spain
- Servicio de Hematología, Hospital Universitario de Salamanca, Salamanca, Spain
| | - José María Bastida
- Instituto de Investigación Biomédica de Salamanca (IBSAL), Salamanca, Spain
- Departamento de Medicina, Universidad de Salamanca, Salamanca, Spain
- Servicio de Hematología, Hospital Universitario de Salamanca, Salamanca, Spain
| | - Almudena Porras
- Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad Complutense de Madrid, Ciudad Universitaria, Madrid, Spain.
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain.
| | - Carmen Guerrero
- Instituto de Biología Molecular y Celular del Cáncer (IMBCC), USAL-CSIC, Centro de Investigación del Cáncer, Campus Unamuno S/N, Salamanca, Spain.
- Instituto de Investigación Biomédica de Salamanca (IBSAL), Salamanca, Spain.
- Departamento de Medicina, Universidad de Salamanca, Salamanca, Spain.
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5
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Lima IS, da Silva TM, Weiss S, Homuth G, Lerch MM, Figueiredo CA, Alcantara-Neves NM, Barreto ML, Marques CR. Genome-wide association study of Helicobacter pylori serological status in Latin American children. Helicobacter 2023; 28:e13008. [PMID: 37497783 DOI: 10.1111/hel.13008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 06/07/2023] [Accepted: 07/10/2023] [Indexed: 07/28/2023]
Abstract
BACKGROUND Few genome-wide association studies (GWAS) on Helicobacter pylori infection susceptibility have been conducted for admixed populations from developing countries. Here, we performed a GWAS to identify genetic factors associated with H. pylori serostatus in a cohort of admixed children from a large Latin American urban center. METHODS A cross-sectional study involving 1161 children from 4 to 11 years old living in poor areas of Salvador, in northeastern Brazil. Logistic regression analysis was performed to detect associations between single-nucleotide variants (SNVs) and H. pylori seropositivity, assuming an additive genetic model. Enrichment analyses were conducted using the MAGMA v1.10 software. RESULTS We found 22 SNVs to be suggestively associated (p < 10-5 ) with H. pylori seropositivity. The most suggestive SNV was the rs77955022 (p = 4.83e-07) located in an intronic region of EXOC3 at 5p15.33. The second most suggestively associated SNV was rs10914996 (p = 8.97e-07), located in an intergenic region at 1p34.3. Furthermore, we were able to replicate three SNVs (p < 0.05) in the Study of Health in Pomerania (SHIP) cohort: the rs2339212 and rs4795970, both located at 17q12 near TMEM132E, as well as the rs6595814, an intronic variant of FBN2 at 5q23.3. The enrichment analysis indicated the participation of genes and metabolic pathways related to the regulation of the digestive system and gastric acid secretion in the risk of seropositivity for H. pylori. CONCLUSIONS Additional studies are required to validate these association findings in larger population samples and to get insight into the underlying physiological mechanisms.
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Affiliation(s)
- Iasmin Souza Lima
- Multidisciplinary Institute in Health, Federal University of Bahia, Vitória da Conquista, Brazil
| | | | - Stefan Weiss
- Department of Functional Genomics, Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
- Department of Medicine A, University Medicine Greifswald, Greifswald, Germany
| | - Georg Homuth
- Department of Functional Genomics, Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Markus M Lerch
- Department of Medicine A, University Medicine Greifswald, Greifswald, Germany
| | | | | | - Maurício Lima Barreto
- Center of Data and Knowledge Integration for Health, Instituto Gonçalo Muniz, Fundação Osvaldo Cruz, Salvador, Brazil
| | - Cintia Rodrigues Marques
- Multidisciplinary Institute in Health, Federal University of Bahia, Vitória da Conquista, Brazil
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6
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Cheng Z, Zheng Y, Yang W, Sun H, Zhou F, Huang C, Zhang S, Song Y, Liang Q, Yang N, Li M, Liu B, Feng L, Wang L. Pathogenic bacteria exploit transferrin receptor transcytosis to penetrate the blood-brain barrier. Proc Natl Acad Sci U S A 2023; 120:e2307899120. [PMID: 37733740 PMCID: PMC10523449 DOI: 10.1073/pnas.2307899120] [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: 05/11/2023] [Accepted: 08/23/2023] [Indexed: 09/23/2023] Open
Abstract
The human blood-brain barrier (BBB) comprises a single layer of brain microvascular endothelial cells (HBMECs) protecting the brain from bloodborne pathogens. Meningitis is among the most serious diseases, but the mechanisms by which major meningitis-causing bacterial pathogens cross the BBB to reach the brain remain poorly understood. We found that Streptococcus pneumoniae, group B Streptococcus, and neonatal meningitis Escherichia coli commonly exploit a unique vesicle fusion mechanism to hitchhike on transferrin receptor (TfR) transcytosis to cross the BBB and illustrated the details of this process in human BBB model in vitro and mouse model. Toll-like receptor signals emanating from bacteria-containing vesicles (BCVs) trigger K33-linked polyubiquitination at Lys168 and Lys181 of the innate immune regulator TRAF3 and then activate the formation of a protein complex containing the guanine nucleotide exchange factor RCC2, the small GTPase RalA and exocyst subcomplex I (SC I) on BCVs. The distinct function of SEC6 in SC I, interacting directly with RalA on BCVs and the SNARE protein SNAP23 on TfR vesicles, tethers these two vesicles and initiates the fusion. Our results reveal that innate immunity triggers a unique modification of TRAF3 and the formation of the HBMEC-specific protein complex on BCVs to authenticate the precise recognition and selection of TfR vesicles to fuse with and facilitate bacterial penetration of the BBB.
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Affiliation(s)
- Zhihui Cheng
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin300071, China
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin300071, China
| | - Yangyang Zheng
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin300071, China
- TEDA Institute of Biological Sciences and Biotechnology, Tianjin Key Laboratory of Microbial Functional Genomics, Nankai University, Tianjin300457, China
| | - Wen Yang
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin300071, China
- TEDA Institute of Biological Sciences and Biotechnology, Tianjin Key Laboratory of Microbial Functional Genomics, Nankai University, Tianjin300457, China
| | - Hongmin Sun
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin300071, China
- TEDA Institute of Biological Sciences and Biotechnology, Tianjin Key Laboratory of Microbial Functional Genomics, Nankai University, Tianjin300457, China
| | - Fangyu Zhou
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin300071, China
- TEDA Institute of Biological Sciences and Biotechnology, Tianjin Key Laboratory of Microbial Functional Genomics, Nankai University, Tianjin300457, China
| | - Chuangjie Huang
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin300071, China
- TEDA Institute of Biological Sciences and Biotechnology, Tianjin Key Laboratory of Microbial Functional Genomics, Nankai University, Tianjin300457, China
| | - Shuwen Zhang
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin300071, China
- TEDA Institute of Biological Sciences and Biotechnology, Tianjin Key Laboratory of Microbial Functional Genomics, Nankai University, Tianjin300457, China
| | - Yingying Song
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin300071, China
- TEDA Institute of Biological Sciences and Biotechnology, Tianjin Key Laboratory of Microbial Functional Genomics, Nankai University, Tianjin300457, China
| | - Qi’an Liang
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin300071, China
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin300071, China
| | - Nan Yang
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin300071, China
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin300071, China
| | - Meifang Li
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin300071, China
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin300071, China
| | - Bin Liu
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin300071, China
- TEDA Institute of Biological Sciences and Biotechnology, Tianjin Key Laboratory of Microbial Functional Genomics, Nankai University, Tianjin300457, China
| | - Lu Feng
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin300071, China
- TEDA Institute of Biological Sciences and Biotechnology, Tianjin Key Laboratory of Microbial Functional Genomics, Nankai University, Tianjin300457, China
| | - Lei Wang
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin300071, China
- TEDA Institute of Biological Sciences and Biotechnology, Tianjin Key Laboratory of Microbial Functional Genomics, Nankai University, Tianjin300457, China
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7
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Ireton K, Gyanwali GC, Herath TUB, Lee N. Exploitation of the host exocyst complex by bacterial pathogens. Mol Microbiol 2023. [PMID: 36717381 DOI: 10.1111/mmi.15034] [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: 11/17/2022] [Revised: 01/24/2023] [Accepted: 01/26/2023] [Indexed: 02/01/2023]
Abstract
Intracellular bacterial pathogens remodel the plasma membrane of eukaryotic cells in order to establish infection. A common and well-studied mechanism of plasma membrane remodelling involves bacterial stimulation of polymerization of the host actin cytoskeleton. Here, we discuss recent results showing that several bacterial pathogens also exploit the host vesicular trafficking pathway of 'polarized exocytosis' to expand and reshape specific regions in the plasma membrane during infection. Polarized exocytosis is mediated by an evolutionarily conserved octameric protein complex termed the exocyst. We describe examples in which the bacteria Listeria monocytogenes, Salmonella enterica serovar Typhimurium, and Shigella flexneri co-opt the exocyst to promote internalization into human cells or intercellular spread within host tissues. We also discuss results showing that Legionella pneumophila or S. flexneri manipulate exocyst components to modify membrane vacuoles to favour intracellular replication or motility of bacteria. Finally, we propose potential ways that pathogens manipulate exocyst function, discuss how polarized exocytosis might promote infection and highlight the importance of future studies to determine how actin polymerization and polarized exocytosis are coordinated to achieve optimal bacterial infection.
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Affiliation(s)
- Keith Ireton
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | | | - Thilina U B Herath
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Nicole Lee
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
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8
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Jimenez V, Miranda K, Ingrid A. The old and the new about the contractile vacuole of Trypanosoma cruzi. J Eukaryot Microbiol 2022; 69:e12939. [PMID: 35916682 PMCID: PMC11178379 DOI: 10.1111/jeu.12939] [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: 06/27/2022] [Revised: 07/27/2022] [Accepted: 07/27/2022] [Indexed: 11/28/2022]
Abstract
Osmoregulation is a conserved cellular process required for the survival of all organisms. In protists, the need for robust compensatory mechanisms that can maintain cell volume and tonicity within physiological range is even more relevant, as their life cycles are often completed in different environments. Trypanosoma cruzi, the protozoan pathogen responsible for Chagas disease, is transmitted by an insect vector to multiple types of mammalian hosts. The contractile vacuole complex (CVC) is an organelle that senses and compensates osmotic changes in the parasites, ensuring their survival upon ionic and osmotic challenges. Recent work shows that the contractile vacuole is also a key component of the secretory and endocytic pathways, regulating the selective targeting of surface proteins during differentiation. Here we summarize our current knowledge of the mechanisms involved in the osmoregulatory processes that take place in the vacuole, and we explore the new and exciting functions of this organelle in cell trafficking and signaling.
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Affiliation(s)
- Veronica Jimenez
- Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, California, USA
| | - Kildare Miranda
- Laboratorio de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- Centro Nacional de Biologia Estrutural e Bioimagem, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Augusto Ingrid
- Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, California, USA
- Laboratorio de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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9
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Guo H, Wang J, Ren S, Zheng LF, Zhuang YX, Li DL, Sun HH, Liu LY, Xie C, Wu YY, Wang HR, Deng X, Li P, Zhao TJ. Targeting EGFR-dependent tumors by disrupting an ARF6-mediated sorting system. Nat Commun 2022; 13:6004. [PMID: 36224181 PMCID: PMC9556547 DOI: 10.1038/s41467-022-33788-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 10/03/2022] [Indexed: 11/09/2022] Open
Abstract
Aberrant activation of EGFR due to overexpression or mutation is associated with poor prognosis in many types of tumors. Here we show that blocking the sorting system that directs EGFR to plasma membrane is a potent strategy to treat EGFR-dependent tumors. We find that EGFR palmitoylation by DHHC13 is critical for its plasma membrane localization and identify ARF6 as a key factor in this process. N-myristoylated ARF6 recognizes palmitoylated EGFR via lipid-lipid interaction, recruits the exocyst complex to promote EGFR budding from Golgi, and facilitates EGFR transporting to plasma membrane in a GTP-bound form. To evaluate the therapeutic potential of this sorting system, we design a cell-permeable peptide, N-myristoylated GKVL-TAT, and find it effectively disrupts plasma membrane localization of EGFR and significantly inhibits progression of EGFR-dependent tumors. Our findings shed lights on the underlying mechanism of how palmitoylation directs protein sorting and provide an potential strategy to manage EGFR-dependent tumors. EGFR is aberrantly activated in many cancer types. Here the authors show that small GTPase ARF6 mediates the trafficking of palmitoylated EGFR from Golgi to plasma membrane and the blockade of this sorting system inhibits the growth of EGFR overexpression tumours.
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Affiliation(s)
- Huiling Guo
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Juan Wang
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Metabolic Remodeling and Health, Institute of Metabolism and Integrative Biology, Zhongshan Hospital, Fudan University, Shanghai, 200438, China
| | - Su Ren
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Lang-Fan Zheng
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Metabolic Remodeling and Health, Institute of Metabolism and Integrative Biology, Zhongshan Hospital, Fudan University, Shanghai, 200438, China
| | - Yi-Xuan Zhuang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Dong-Lin Li
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Hui-Hui Sun
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Li-Ying Liu
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Changchuan Xie
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Ya-Ying Wu
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Hong-Rui Wang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Xianming Deng
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China.,State-province Joint Engineering Laboratory of Targeted Drugs from Natural Products, Xiamen University, Xiamen, Fujian, 361102, China
| | - Peng Li
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Metabolic Remodeling and Health, Institute of Metabolism and Integrative Biology, Zhongshan Hospital, Fudan University, Shanghai, 200438, China.,School of life sciences, Zhengzhou University, Zhengzhou, Henan, 450001, China.,Shanghai Qi Zhi Institute, Shanghai, 200232, China
| | - Tong-Jin Zhao
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Metabolic Remodeling and Health, Institute of Metabolism and Integrative Biology, Zhongshan Hospital, Fudan University, Shanghai, 200438, China. .,Shanghai Qi Zhi Institute, Shanghai, 200232, China.
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10
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Farquhar RE, Cheung TT, Logue MJE, McDonald FJ, Devor DC, Hamilton KL. Role of SNARE Proteins in the Insertion of KCa3.1 in the Plasma Membrane of a Polarized Epithelium. Front Physiol 2022; 13:905834. [PMID: 35832483 PMCID: PMC9271999 DOI: 10.3389/fphys.2022.905834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Accepted: 06/01/2022] [Indexed: 11/29/2022] Open
Abstract
Targeting proteins to a specific membrane is crucial for proper epithelial cell function. KCa3.1, a calcium-activated, intermediate-conductance potassium channel, is targeted to the basolateral membrane (BLM) in epithelial cells. Surprisingly, the mechanism of KCa3.1 membrane targeting is poorly understood. We previously reported that targeting of KCa3.1 to the BLM of epithelial cells is Myosin-Vc-, Rab1-and Rab8-dependent. Here, we examine the role of the SNARE proteins VAMP3, SNAP-23 and syntaxin 4 (STX-4) in the targeting of KCa3.1 to the BLM of Fischer rat thyroid (FRT) epithelial cells. We carried out immunoblot, siRNA and Ussing chamber experiments on FRT cells, stably expressing KCa3.1-BLAP/Bir-A-KDEL, grown as high-resistance monolayers. siRNA-mediated knockdown of VAMP3 reduced BLM expression of KCa3.1 by 57 ± 5% (p ≤ 0.05, n = 5). Measurements of BLM-localized KCa3.1 currents, in Ussing chambers, demonstrated knockdown of VAMP3 reduced KCa3.1 current by 70 ± 4% (p ≤ 0.05, n = 5). Similarly, siRNA knockdown of SNAP-23 reduced the expression of KCa3.1 at the BLM by 56 ± 7% (p ≤ 0.01, n = 6) and reduced KCa3.1 current by 80 ± 11% (p ≤ 0.05, n = 6). Also, knockdown of STX-4 lowered the BLM expression of KCa3.1 by 54 ± 6% (p ≤ 0.05, n = 5) and reduced KCa3.1 current by 78 ± 11% (p ≤ 0.05, n = 5). Finally, co-immunoprecipitation experiments demonstrated associations between KCa3.1, VAMP3, SNAP-23 and STX-4. These data indicate that VAMP3, SNAP-23 and STX-4 are critical for the targeting KCa3.1 to BLM of polarized epithelial cells.
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Affiliation(s)
- Rachel E. Farquhar
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Tanya T. Cheung
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Matthew J. E. Logue
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Fiona J. McDonald
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Daniel C. Devor
- Department of Cell Biology, University of Pittsburgh, School of Medicine, Pittsburgh, PA, United States
| | - Kirk L. Hamilton
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
- *Correspondence: Kirk L. Hamilton,
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11
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Abstract
Phosphoinositides are signalling lipids derived from phosphatidylinositol, a ubiquitous phospholipid in the cytoplasmic leaflet of eukaryotic membranes. Initially discovered for their roles in cell signalling, phosphoinositides are now widely recognized as key integrators of membrane dynamics that broadly impact on all aspects of cell physiology and on disease. The past decade has witnessed a vast expansion of our knowledge of phosphoinositide biology. On the endocytic and exocytic routes, phosphoinositides direct the inward and outward flow of membrane as vesicular traffic is coupled to the conversion of phosphoinositides. Moreover, recent findings on the roles of phosphoinositides in autophagy and the endolysosomal system challenge our view of lysosome biology. The non-vesicular exchange of lipids, ions and metabolites at membrane contact sites in between organelles has also been found to depend on phosphoinositides. Here we review our current understanding of how phosphoinositides shape and direct membrane dynamics to impact on cell physiology, and provide an overview of emerging concepts in phosphoinositide regulation.
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12
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García P, Coll PM, Del Rey F, Geli MI, Pérez P, Vázquez de Aldana CR, Encinar Del Dedo J. Eng2, a new player involved in feedback loop regulation of Cdc42 activity in fission yeast. Sci Rep 2021; 11:17872. [PMID: 34504165 PMCID: PMC8429772 DOI: 10.1038/s41598-021-97311-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 08/05/2021] [Indexed: 11/09/2022] Open
Abstract
Cell polarity and morphogenesis are regulated by the small GTPase Cdc42. Even though major advances have been done in the field during the last years, the molecular details leading to its activation in particular cellular contexts are not completely understood. In fission yeast, the β(1,3)-glucanase Eng2 is a "moonlighting protein" with a dual function, acting as a hydrolase during spore dehiscence, and as component of the endocytic machinery in vegetative cells. Here, we report that Eng2 plays a role in Cdc42 activation during polarized growth through its interaction with the scaffold protein Scd2, which brings Cdc42 together with its guanine nucleotide exchange factor (GEF) Scd1. eng2Δ mutant cells have defects in activation of the bipolar growth (NETO), remaining monopolar during all the cell cycle. In the absence of Eng2 the accumulation of Scd1 and Scd2 at the poles is reduced, the levels of Cdc42 activation decrease, and the Cdc42 oscillatory behavior, associated with bipolar growth in wild type cells, is altered. Furthermore, overexpression of Eng2 partially rescues the growth and polarity defects of a cdc42-L160S mutant. Altogether, our work unveils a new factor regulating the activity of Cdc42, which could potentially link the polarity and endocytic machineries.
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Affiliation(s)
- Patricia García
- Instituto de Biología Funcional y Genómica, CSIC/Universidad de Salamanca, c/ Zacarías González 2, 37007, Salamanca, Spain
| | - Pedro M Coll
- Instituto de Biología Funcional y Genómica, CSIC/Universidad de Salamanca, c/ Zacarías González 2, 37007, Salamanca, Spain
| | - Francisco Del Rey
- Instituto de Biología Funcional y Genómica, CSIC/Universidad de Salamanca, c/ Zacarías González 2, 37007, Salamanca, Spain
| | - M Isabel Geli
- Institute for Molecular Biology of Barcelona (CSIC), Baldiri Reixac 15, 08028, Barcelona, Spain
| | - Pilar Pérez
- Instituto de Biología Funcional y Genómica, CSIC/Universidad de Salamanca, c/ Zacarías González 2, 37007, Salamanca, Spain
| | - Carlos R Vázquez de Aldana
- Instituto de Biología Funcional y Genómica, CSIC/Universidad de Salamanca, c/ Zacarías González 2, 37007, Salamanca, Spain.
| | - Javier Encinar Del Dedo
- Instituto de Biología Funcional y Genómica, CSIC/Universidad de Salamanca, c/ Zacarías González 2, 37007, Salamanca, Spain.
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13
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Lei Z, Wang J, Zhang L, Liu CH. Ubiquitination-Dependent Regulation of Small GTPases in Membrane Trafficking: From Cell Biology to Human Diseases. Front Cell Dev Biol 2021; 9:688352. [PMID: 34277632 PMCID: PMC8281112 DOI: 10.3389/fcell.2021.688352] [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: 03/30/2021] [Accepted: 06/09/2021] [Indexed: 01/04/2023] Open
Abstract
Membrane trafficking is critical for cellular homeostasis, which is mainly carried out by small GTPases, a class of proteins functioning in vesicle budding, transport, tethering and fusion processes. The accurate and organized membrane trafficking relies on the proper regulation of small GTPases, which involves the conversion between GTP- and GDP-bound small GTPases mediated by guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). Emerging evidence indicates that post-translational modifications (PTMs) of small GTPases, especially ubiquitination, play an important role in the spatio-temporal regulation of small GTPases, and the dysregulation of small GTPase ubiquitination can result in multiple human diseases. In this review, we introduce small GTPases-mediated membrane trafficking pathways and the biological processes of ubiquitination-dependent regulation of small GTPases, including the regulation of small GTPase stability, activity and localization. We then discuss the dysregulation of small GTPase ubiquitination and the associated human membrane trafficking-related diseases, focusing on the neurological diseases and infections. An in-depth understanding of the molecular mechanisms by which ubiquitination regulates small GTPases can provide novel insights into the membrane trafficking process, which knowledge is valuable for the development of more effective and specific therapeutics for membrane trafficking-related human diseases.
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Affiliation(s)
- Zehui Lei
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Beijing, China.,Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China
| | - Jing Wang
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Beijing, China
| | - Lingqiang Zhang
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences (Beijing), Beijing Institute of Lifeomics, Beijing, China
| | - Cui Hua Liu
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Beijing, China.,Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China
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14
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Boukhalfa A, Roccio F, Dupont N, Codogno P, Morel E. The autophagy protein ATG16L1 cooperates with IFT20 and INPP5E to regulate the turnover of phosphoinositides at the primary cilium. Cell Rep 2021; 35:109045. [PMID: 33910006 DOI: 10.1016/j.celrep.2021.109045] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 02/22/2021] [Accepted: 04/07/2021] [Indexed: 02/07/2023] Open
Abstract
The primary cilium (PC) regulates signalization linked to external stress sensing. Previous works established a functional interplay between the PC and the autophagic machinery. When ciliogenesis is promoted by serum deprivation, the autophagy protein ATG16L1 and the ciliary protein IFT20 are co-transported to the PC. Here, we demonstrate that IFT20 and ATG16L1 are part of the same complex requiring the WD40 domain of ATG16L1 and a Y-E-F-I motif in IFT20. We show that ATG16L1-deficient cells exhibit aberrant ciliary structures, which accumulate PI4,5P2, whereas PI4P, a lipid normally concentrated in the PC, is absent. Finally, we demonstrate that INPP5E, a phosphoinositide-associated phosphatase responsible for PI4P generation, interacts with ATG16L1 and that a perturbation of the ATG16L1/IFT20 complex alters its trafficking to the PC. Altogether, our results reveal a function of ATG16L1 in ciliary lipid and protein trafficking, thus directly contributing to proper PC dynamics and functions.
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Affiliation(s)
- Asma Boukhalfa
- Institut Necker-Enfants Malades (INEM), INSERM U1151-CNRS UMR 8253, Université de Paris, Paris, France
| | - Federica Roccio
- Institut Necker-Enfants Malades (INEM), INSERM U1151-CNRS UMR 8253, Université de Paris, Paris, France
| | - Nicolas Dupont
- Institut Necker-Enfants Malades (INEM), INSERM U1151-CNRS UMR 8253, Université de Paris, Paris, France
| | - Patrice Codogno
- Institut Necker-Enfants Malades (INEM), INSERM U1151-CNRS UMR 8253, Université de Paris, Paris, France.
| | - Etienne Morel
- Institut Necker-Enfants Malades (INEM), INSERM U1151-CNRS UMR 8253, Université de Paris, Paris, France.
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15
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Cancer-driving mutations and variants of components of the membrane trafficking core machinery. Life Sci 2020; 264:118662. [PMID: 33127517 DOI: 10.1016/j.lfs.2020.118662] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 10/17/2020] [Accepted: 10/22/2020] [Indexed: 12/12/2022]
Abstract
The core machinery for vesicular membrane trafficking broadly comprises of coat proteins, RABs, tethering complexes and SNAREs. As cellular membrane traffic modulates key processes of mitogenic signaling, cell migration, cell death and autophagy, its dysregulation could potentially results in increased cell proliferation and survival, or enhanced migration and invasion. Changes in the levels of some components of the core machinery of vesicular membrane trafficking, likely due to gene amplifications and/or alterations in epigenetic factors (such as DNA methylation and micro RNA) have been extensively associated with human cancers. Here, we provide an overview of association of membrane trafficking with cancer, with a focus on mutations and variants of coat proteins, RABs, tethering complex components and SNAREs that have been uncovered in human cancer cells/tissues. The major cellular and molecular cancer-driving or suppression mechanisms associated with these components of the core membrane trafficking machinery shall be discussed.
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16
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Silva-Rodrigues JF, Patrício-Rodrigues CF, de Sousa-Xavier V, Augusto PM, Fernandes AC, Farinho AR, Martins JP, Teodoro RO. Peripheral axonal ensheathment is regulated by RalA GTPase and the exocyst complex. Development 2020; 147:dev.174540. [PMID: 31969325 DOI: 10.1242/dev.174540] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 01/14/2020] [Indexed: 12/21/2022]
Abstract
Axon ensheathment is fundamental for fast impulse conduction and the normal physiological functioning of the nervous system. Defects in axonal insulation lead to debilitating conditions, but, despite its importance, the molecular players responsible are poorly defined. Here, we identify RalA GTPase as a key player in axon ensheathment in Drosophila larval peripheral nerves. We demonstrate through genetic analysis that RalA action through the exocyst complex is required in wrapping glial cells to regulate their growth and development. We suggest that the RalA-exocyst pathway controls the targeting of secretory vesicles for membrane growth or for the secretion of a wrapping glia-derived factor that itself regulates growth. In summary, our findings provide a new molecular understanding of the process by which axons are ensheathed in vivo, a process that is crucial for normal neuronal function.
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Affiliation(s)
- Joana F Silva-Rodrigues
- CEDOC, Chronic Diseases Research Centre, NOVA Medical School - Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1150-082 Lisboa, Portugal
| | - Cátia F Patrício-Rodrigues
- CEDOC, Chronic Diseases Research Centre, NOVA Medical School - Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1150-082 Lisboa, Portugal
| | - Vicente de Sousa-Xavier
- CEDOC, Chronic Diseases Research Centre, NOVA Medical School - Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1150-082 Lisboa, Portugal
| | - Pedro M Augusto
- CEDOC, Chronic Diseases Research Centre, NOVA Medical School - Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1150-082 Lisboa, Portugal
| | - Ana C Fernandes
- CEDOC, Chronic Diseases Research Centre, NOVA Medical School - Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1150-082 Lisboa, Portugal
| | - Ana R Farinho
- CEDOC, Chronic Diseases Research Centre, NOVA Medical School - Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1150-082 Lisboa, Portugal
| | - João P Martins
- CEDOC, Chronic Diseases Research Centre, NOVA Medical School - Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1150-082 Lisboa, Portugal.,Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
| | - Rita O Teodoro
- CEDOC, Chronic Diseases Research Centre, NOVA Medical School - Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1150-082 Lisboa, Portugal
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17
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Listeria monocytogenes exploits host exocytosis to promote cell-to-cell spread. Proc Natl Acad Sci U S A 2020; 117:3789-3796. [PMID: 32015134 DOI: 10.1073/pnas.1916676117] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The facultative intracellular pathogen Listeria monocytogenes uses an actin-based motility process to spread within human tissues. Filamentous actin from the human cell forms a tail behind bacteria, propelling microbes through the cytoplasm. Motile bacteria remodel the host plasma membrane into protrusions that are internalized by neighboring cells. A critical unresolved question is whether generation of protrusions by Listeria involves stimulation of host processes apart from actin polymerization. Here we demonstrate that efficient protrusion formation in polarized epithelial cells involves bacterial subversion of host exocytosis. Confocal microscopy imaging indicated that exocytosis is up-regulated in protrusions of Listeria in a manner that depends on the host exocyst complex. Depletion of components of the exocyst complex by RNA interference inhibited the formation of Listeria protrusions and subsequent cell-to-cell spread of bacteria. Additional genetic studies indicated important roles for the exocyst regulators Rab8 and Rab11 in bacterial protrusion formation and spread. The secreted Listeria virulence factor InlC associated with the exocyst component Exo70 and mediated the recruitment of Exo70 to bacterial protrusions. Depletion of exocyst proteins reduced the length of Listeria protrusions, suggesting that the exocyst complex promotes protrusion elongation. Collectively, these results demonstrate that Listeria exploits host exocytosis to stimulate intercellular spread of bacteria.
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