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Lu J, Veler A, Simonetti B, Raj T, Chou PH, Cross SJ, Phillips AM, Ruan X, Huynh L, Dowsey AW, Ye D, Murphy RF, Verkade P, Cullen PJ, Wülfing C. Five Inhibitory Receptors Display Distinct Vesicular Distributions in Murine T Cells. Cells 2023; 12:2558. [PMID: 37947636 PMCID: PMC10649679 DOI: 10.3390/cells12212558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 10/26/2023] [Accepted: 10/30/2023] [Indexed: 11/12/2023] Open
Abstract
T cells can express multiple inhibitory receptors. Upon induction of T cell exhaustion in response to a persistent antigen, prominently in the anti-tumor immune response, many are expressed simultaneously. Key inhibitory receptors are CTLA-4, PD-1, LAG3, TIM3, and TIGIT, as investigated here. These receptors are important as central therapeutic targets in cancer immunotherapy. Inhibitory receptors are not constitutively expressed on the cell surface, but substantial fractions reside in intracellular vesicular structures. It remains unresolved to which extent the subcellular localization of different inhibitory receptors is distinct. Using quantitative imaging of subcellular distributions and plasma membrane insertion as complemented by proximity proteomics and biochemical analysis of the association of the inhibitory receptors with trafficking adaptors, the subcellular distributions of the five inhibitory receptors were discrete. The distribution of CTLA-4 was most distinct, with preferential association with lysosomal-derived vesicles and the sorting nexin 1/2/5/6 transport machinery. With a lack of evidence for the existence of specific vesicle subtypes to explain divergent inhibitory receptor distributions, we suggest that such distributions are driven by divergent trafficking through an overlapping joint set of vesicular structures. This extensive characterization of the subcellular localization of five inhibitory receptors in relation to each other lays the foundation for the molecular investigation of their trafficking and its therapeutic exploitation.
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Affiliation(s)
- Jiahe Lu
- School of Cellular and Molecular Medicine, University of Bristol, Bristol BS8 1TD, UK; (J.L.); (A.V.); (T.R.); (P.H.C.); (L.H.)
- Department of Urology, Fudan University Shanghai Cancer Center, Fudan University, Shanghai 200032, China;
| | - Alisa Veler
- School of Cellular and Molecular Medicine, University of Bristol, Bristol BS8 1TD, UK; (J.L.); (A.V.); (T.R.); (P.H.C.); (L.H.)
| | - Boris Simonetti
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK; (B.S.); (P.V.); (P.J.C.)
| | - Timsse Raj
- School of Cellular and Molecular Medicine, University of Bristol, Bristol BS8 1TD, UK; (J.L.); (A.V.); (T.R.); (P.H.C.); (L.H.)
| | - Po Han Chou
- School of Cellular and Molecular Medicine, University of Bristol, Bristol BS8 1TD, UK; (J.L.); (A.V.); (T.R.); (P.H.C.); (L.H.)
| | - Stephen J. Cross
- Wolfson Bioimaging Facility, University of Bristol, Bristol BS8 1TD, UK;
| | - Alexander M. Phillips
- Department of Electrical Engineering & Electronics and Computational Biology Facility, University of Liverpool, Liverpool L69 7ZX, UK;
| | - Xiongtao Ruan
- Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA 15213, USA; (X.R.); (R.F.M.)
| | - Lan Huynh
- School of Cellular and Molecular Medicine, University of Bristol, Bristol BS8 1TD, UK; (J.L.); (A.V.); (T.R.); (P.H.C.); (L.H.)
| | - Andrew W. Dowsey
- Bristol Veterinary School, University of Bristol, Bristol BS40 5DU, UK;
| | - Dingwei Ye
- Department of Urology, Fudan University Shanghai Cancer Center, Fudan University, Shanghai 200032, China;
- Shanghai Genitourinary Cancer Institute, Shanghai 200032, China
| | - Robert F. Murphy
- Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA 15213, USA; (X.R.); (R.F.M.)
- Department of Biological Sciences, Biomedical Engineering and Machine Learning, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Paul Verkade
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK; (B.S.); (P.V.); (P.J.C.)
| | - Peter J. Cullen
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK; (B.S.); (P.V.); (P.J.C.)
| | - Christoph Wülfing
- School of Cellular and Molecular Medicine, University of Bristol, Bristol BS8 1TD, UK; (J.L.); (A.V.); (T.R.); (P.H.C.); (L.H.)
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Lu J, Veler A, Simonetti B, Raj T, Chou PH, Cross SJ, Phillips AM, Ruan X, Huynh L, Dowsey AW, Ye D, Murphy RF, Verkade P, Cullen PJ, Wülfing C. Five inhibitory receptors display distinct vesicular distributions in T cells. bioRxiv 2023:2023.07.21.550019. [PMID: 37503045 PMCID: PMC10370166 DOI: 10.1101/2023.07.21.550019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
T cells can express multiple inhibitory receptors. Upon induction of T cell exhaustion in response to persistent antigen, prominently in the anti-tumor immune response, many are expressed simultaneously. Key inhibitory receptors are CTLA-4, PD-1, LAG3, TIM3 and TIGIT, as investigated here. These receptors are important as central therapeutic targets in cancer immunotherapy. Inhibitory receptors are not constitutively expressed on the cell surface, but substantial fractions reside in intracellular vesicular structures. It remains unresolved to which extent the subcellular localization of different inhibitory receptors is distinct. Using quantitative imaging of subcellular distributions and plasma membrane insertion as complemented by proximity proteomics and a biochemical analysis of the association of the inhibitory receptors with trafficking adaptors, the subcellular distributions of the five inhibitory receptors were discrete. The distribution of CTLA-4 was most distinct with preferential association with lysosomal-derived vesicles and the sorting nexin 1/2/5/6 transport machinery. With a lack of evidence for the existence of specific vesicle subtypes to explain divergent inhibitory receptor distributions, we suggest that such distributions are driven by divergent trafficking through an overlapping joint set of vesicular structures. This extensive characterization of the subcellular localization of five inhibitory receptors in relation to each other lays the foundation for the molecular investigation of their trafficking and its therapeutic exploitation.
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Affiliation(s)
- Jiahe Lu
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, BS8 1TD, UK
- Department of Urology, Fudan University Shanghai Cancer Center, Fudan University, Shanghai, 200032, P.R. China
- Shanghai Genitourinary Cancer Institute, Shanghai, 200032, P.R. China
| | - Alisa Veler
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, BS8 1TD, UK
| | - Boris Simonetti
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK
| | - Timsse Raj
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, BS8 1TD, UK
| | - Po Han Chou
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, BS8 1TD, UK
| | - Stephen J. Cross
- Wolfson BioImaging Facility, University of Bristol, Bristol, BS8 1TD, UK
| | - Alexander M. Phillips
- Department of Electrical Engineering & Electronics and Computational Biology Facility, University of Liverpool, Liverpool, L69 7ZX, UK
| | - Xiongtao Ruan
- Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Lan Huynh
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, BS8 1TD, UK
| | - Andrew W. Dowsey
- Bristol Veterinary School, University of Bristol, Bristol, BS40 5DU, UK
| | - Dingwei Ye
- Department of Urology, Fudan University Shanghai Cancer Center, Fudan University, Shanghai, 200032, P.R. China
- Shanghai Genitourinary Cancer Institute, Shanghai, 200032, P.R. China
| | - Robert F. Murphy
- Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA 15213, USA
- Departments of Biological Sciences, Biomedical Engineering and Machine Learning, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Paul Verkade
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK
| | - Peter J. Cullen
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK
| | - Christoph Wülfing
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, BS8 1TD, UK
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3
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Simonetti B, Daly JL, Cullen PJ. Out of the ESCPE room: Emerging roles of endosomal SNX-BARs in receptor transport and host-pathogen interaction. Traffic 2023; 24:234-250. [PMID: 37089068 PMCID: PMC10768393 DOI: 10.1111/tra.12885] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 02/22/2023] [Accepted: 03/28/2023] [Indexed: 04/25/2023]
Abstract
Several functions of the human cell, such as sensing nutrients, cell movement and interaction with the surrounding environment, depend on a myriad of transmembrane proteins and their associated proteins and lipids (collectively termed "cargoes"). To successfully perform their tasks, cargo must be sorted and delivered to the right place, at the right time, and in the right amount. To achieve this, eukaryotic cells have evolved a highly organized sorting platform, the endosomal network. Here, a variety of specialized multiprotein complexes sort cargo into itineraries leading to either their degradation or their recycling to various organelles for further rounds of reuse. A key sorting complex is the Endosomal SNX-BAR Sorting Complex for Promoting Exit (ESCPE-1) that promotes the recycling of an array of cargos to the plasma membrane and/or the trans-Golgi network. ESCPE-1 recognizes a hydrophobic-based sorting motif in numerous cargoes and orchestrates their packaging into tubular carriers that pinch off from the endosome and travel to the target organelle. A wide range of pathogens mimic this sorting motif to hijack ESCPE-1 transport to promote their invasion and survival within infected cells. In other instances, ESCPE-1 exerts restrictive functions against pathogens by limiting their replication and infection. In this review, we discuss ESCPE-1 assembly and functions, with a particular focus on recent advances in the understanding of its role in membrane trafficking, cellular homeostasis and host-pathogen interaction.
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Affiliation(s)
- Boris Simonetti
- Charles River Laboratories, Discovery House, Quays Office ParkConference Avenue, PortisheadBristolUK
| | - James L. Daly
- Department of Infectious DiseasesSchool of Immunology and Microbial Sciences, Guy's Hospital, King's College LondonLondonUK
| | - Peter J. Cullen
- School of Biochemistry, Faculty of Life Sciences, Biomedical Sciences BuildingUniversity of BristolBristolUK
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4
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Simonetti B, Guo Q, Giménez-Andrés M, Chen KE, Moody ERR, Evans AJ, Chandra M, Danson CM, Williams TA, Collins BM, Cullen PJ. SNX27-Retromer directly binds ESCPE-1 to transfer cargo proteins during endosomal recycling. PLoS Biol 2022; 20:e3001601. [PMID: 35417450 PMCID: PMC9038204 DOI: 10.1371/journal.pbio.3001601] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 04/25/2022] [Accepted: 03/11/2022] [Indexed: 12/14/2022] Open
Abstract
Coat complexes coordinate cargo recognition through cargo adaptors with biogenesis of transport carriers during integral membrane protein trafficking. Here, we combine biochemical, structural, and cellular analyses to establish the mechanistic basis through which SNX27-Retromer, a major endosomal cargo adaptor, couples to the membrane remodeling endosomal SNX-BAR sorting complex for promoting exit 1 (ESCPE-1). In showing that the SNX27 FERM (4.1/ezrin/radixin/moesin) domain directly binds acidic-Asp-Leu-Phe (aDLF) motifs in the SNX1/SNX2 subunits of ESCPE-1, we propose a handover model where SNX27-Retromer captured cargo proteins are transferred into ESCPE-1 transport carriers to promote endosome-to-plasma membrane recycling. By revealing that assembly of the SNX27:Retromer:ESCPE-1 coat evolved in a stepwise manner during early metazoan evolution, likely reflecting the increasing complexity of endosome-to-plasma membrane recycling from the ancestral opisthokont to modern animals, we provide further evidence of the functional diversification of yeast pentameric Retromer in the recycling of hundreds of integral membrane proteins in metazoans.
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Affiliation(s)
- Boris Simonetti
- School of Biochemistry, Faculty of Life Sciences, University of Bristol, Bristol, United Kingdom
| | - Qian Guo
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, Australia
| | - Manuel Giménez-Andrés
- School of Biochemistry, Faculty of Life Sciences, University of Bristol, Bristol, United Kingdom
| | - Kai-En Chen
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, Australia
| | - Edmund R. R. Moody
- School of Biological Sciences, Faculty of Life Sciences, University of Bristol, Bristol, United Kingdom
| | - Ashley J. Evans
- School of Biochemistry, Faculty of Life Sciences, University of Bristol, Bristol, United Kingdom
| | - Mintu Chandra
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, Australia
| | - Chris M. Danson
- School of Biochemistry, Faculty of Life Sciences, University of Bristol, Bristol, United Kingdom
| | - Tom A. Williams
- School of Biological Sciences, Faculty of Life Sciences, University of Bristol, Bristol, United Kingdom
| | - Brett M. Collins
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, Australia
| | - Peter J. Cullen
- School of Biochemistry, Faculty of Life Sciences, University of Bristol, Bristol, United Kingdom
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Daly JL, Simonetti B, Klein K, Chen KE, Williamson MK, Antón-Plágaro C, Shoemark DK, Simón-Gracia L, Bauer M, Hollandi R, Greber UF, Horvath P, Sessions RB, Helenius A, Hiscox JA, Teesalu T, Matthews DA, Davidson AD, Collins BM, Cullen PJ, Yamauchi Y. Neuropilin-1 is a host factor for SARS-CoV-2 infection. Science 2020; 370:861-865. [PMID: 33082294 DOI: 10.1101/2020.06.05.134114] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Accepted: 10/12/2020] [Indexed: 05/20/2023]
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), uses the viral spike (S) protein for host cell attachment and entry. The host protease furin cleaves the full-length precursor S glycoprotein into two associated polypeptides: S1 and S2. Cleavage of S generates a polybasic Arg-Arg-Ala-Arg carboxyl-terminal sequence on S1, which conforms to a C-end rule (CendR) motif that binds to cell surface neuropilin-1 (NRP1) and NRP2 receptors. We used x-ray crystallography and biochemical approaches to show that the S1 CendR motif directly bound NRP1. Blocking this interaction by RNA interference or selective inhibitors reduced SARS-CoV-2 entry and infectivity in cell culture. NRP1 thus serves as a host factor for SARS-CoV-2 infection and may potentially provide a therapeutic target for COVID-19.
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Affiliation(s)
- James L Daly
- School of Biochemistry, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Boris Simonetti
- School of Biochemistry, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK.
| | - Katja Klein
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Kai-En Chen
- Institute for Molecular Bioscience, the University of Queensland, St. Lucia, QLD 4072, Australia
| | - Maia Kavanagh Williamson
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Carlos Antón-Plágaro
- School of Biochemistry, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Deborah K Shoemark
- School of Biochemistry and BrisSynBio Centre, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Lorena Simón-Gracia
- Laboratory of Cancer Biology, Institute of Biomedicine and Translational Medicine, University of Tartu, Tartu, Estonia
| | - Michael Bauer
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
| | - Reka Hollandi
- Synthetic and Systems Biology Unit, Biological Research Centre (BRC), Szeged, Hungary
| | - Urs F Greber
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
| | - Peter Horvath
- Synthetic and Systems Biology Unit, Biological Research Centre (BRC), Szeged, Hungary
- Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland
| | - Richard B Sessions
- School of Biochemistry, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Ari Helenius
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | - Julian A Hiscox
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, UK
- Singapore Immunology Network, Agency for Science, Technology, and Research, 138648, Singapore
| | - Tambet Teesalu
- Laboratory of Cancer Biology, Institute of Biomedicine and Translational Medicine, University of Tartu, Tartu, Estonia
| | - David A Matthews
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Andrew D Davidson
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Brett M Collins
- Institute for Molecular Bioscience, the University of Queensland, St. Lucia, QLD 4072, Australia
| | - Peter J Cullen
- School of Biochemistry, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK.
| | - Yohei Yamauchi
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK.
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
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6
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Daly JL, Simonetti B, Klein K, Chen KE, Williamson MK, Antón-Plágaro C, Shoemark DK, Simón-Gracia L, Bauer M, Hollandi R, Greber UF, Horvath P, Sessions RB, Helenius A, Hiscox JA, Teesalu T, Matthews DA, Davidson AD, Collins BM, Cullen PJ, Yamauchi Y. Neuropilin-1 is a host factor for SARS-CoV-2 infection. Science 2020; 370:861-865. [PMID: 33082294 DOI: 10.1126/science.abd3072] [Citation(s) in RCA: 845] [Impact Index Per Article: 211.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Accepted: 10/12/2020] [Indexed: 12/12/2022]
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), uses the viral spike (S) protein for host cell attachment and entry. The host protease furin cleaves the full-length precursor S glycoprotein into two associated polypeptides: S1 and S2. Cleavage of S generates a polybasic Arg-Arg-Ala-Arg carboxyl-terminal sequence on S1, which conforms to a C-end rule (CendR) motif that binds to cell surface neuropilin-1 (NRP1) and NRP2 receptors. We used x-ray crystallography and biochemical approaches to show that the S1 CendR motif directly bound NRP1. Blocking this interaction by RNA interference or selective inhibitors reduced SARS-CoV-2 entry and infectivity in cell culture. NRP1 thus serves as a host factor for SARS-CoV-2 infection and may potentially provide a therapeutic target for COVID-19.
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Affiliation(s)
- James L Daly
- School of Biochemistry, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Boris Simonetti
- School of Biochemistry, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK.
| | - Katja Klein
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Kai-En Chen
- Institute for Molecular Bioscience, the University of Queensland, St. Lucia, QLD 4072, Australia
| | - Maia Kavanagh Williamson
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Carlos Antón-Plágaro
- School of Biochemistry, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Deborah K Shoemark
- School of Biochemistry and BrisSynBio Centre, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Lorena Simón-Gracia
- Laboratory of Cancer Biology, Institute of Biomedicine and Translational Medicine, University of Tartu, Tartu, Estonia
| | - Michael Bauer
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
| | - Reka Hollandi
- Synthetic and Systems Biology Unit, Biological Research Centre (BRC), Szeged, Hungary
| | - Urs F Greber
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
| | - Peter Horvath
- Synthetic and Systems Biology Unit, Biological Research Centre (BRC), Szeged, Hungary.,Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland
| | - Richard B Sessions
- School of Biochemistry, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Ari Helenius
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | - Julian A Hiscox
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, UK.,Singapore Immunology Network, Agency for Science, Technology, and Research, 138648, Singapore
| | - Tambet Teesalu
- Laboratory of Cancer Biology, Institute of Biomedicine and Translational Medicine, University of Tartu, Tartu, Estonia
| | - David A Matthews
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Andrew D Davidson
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Brett M Collins
- Institute for Molecular Bioscience, the University of Queensland, St. Lucia, QLD 4072, Australia
| | - Peter J Cullen
- School of Biochemistry, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK.
| | - Yohei Yamauchi
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK. .,Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
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7
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Evans AJ, Daly JL, Anuar ANK, Simonetti B, Cullen PJ. Acute inactivation of retromer and ESCPE-1 leads to time-resolved defects in endosomal cargo sorting. J Cell Sci 2020; 133:133/15/jcs246033. [PMID: 32747499 PMCID: PMC7420817 DOI: 10.1242/jcs.246033] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 06/05/2020] [Indexed: 01/16/2023] Open
Abstract
Human retromer, a heterotrimer of VPS26 (VPS26A or VPS26B), VPS35 and VPS29, orchestrates the endosomal retrieval of internalised cargo and promotes their cell surface recycling, a prototypical cargo being the glucose transporter GLUT1 (also known as SLC2A1). The role of retromer in the retrograde sorting of the cation-independent mannose 6-phosphate receptor (CI-MPR, also known as IGF2R) from endosomes back to the trans-Golgi network remains controversial. Here, by applying knocksideways technology, we develop a method for acute retromer inactivation. While retromer knocksideways in HeLa and H4 human neuroglioma cells resulted in time-resolved defects in cell surface sorting of GLUT1, we failed to observe a quantifiable defect in CI-MPR sorting. In contrast, knocksideways of the ESCPE-1 complex – a key regulator of retrograde CI-MPR sorting – revealed time-resolved defects in CI-MPR sorting. Together, these data are consistent with a comparatively limited role for retromer in ESCPE-1-mediated CI-MPR retrograde sorting, and establish a methodology for acute retromer and ESCPE-1 inactivation that will aid the time-resolved dissection of their functional roles in endosomal cargo sorting. Summary: Retromer, a master controller of endosomal cargo sorting, is deregulated in neurodegenerative disease. Here, we develop and apply a retromer knocksideways methodology to quantify endosomal cargo sorting upon acute perturbation.
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Affiliation(s)
- Ashley J Evans
- School of Biochemistry, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - James L Daly
- School of Biochemistry, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Anis N K Anuar
- School of Biochemistry, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Boris Simonetti
- School of Biochemistry, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Peter J Cullen
- School of Biochemistry, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
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8
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Antón Z, Betin VMS, Simonetti B, Traer CJ, Attar N, Cullen PJ, Lane JD. A heterodimeric SNX4--SNX7 SNX-BAR autophagy complex coordinates ATG9A trafficking for efficient autophagosome assembly. J Cell Sci 2020; 133:jcs246306. [PMID: 32513819 PMCID: PMC7375690 DOI: 10.1242/jcs.246306] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Accepted: 06/02/2020] [Indexed: 11/24/2022] Open
Abstract
The sorting nexins (SNXs) are a family of peripheral membrane proteins that direct protein trafficking decisions within the endocytic network. Emerging evidence in yeast and mammalian cells implicates a subgroup of SNXs in selective and non-selective forms of autophagy. Using siRNA and CRISPR-Cas9, we demonstrate that the SNX-BAR protein SNX4 is needed for efficient LC3 (also known as MAP1LC3) lipidation and autophagosome assembly in mammalian cells. SNX-BARs exist as homo- and hetero-dimers, and we show that SNX4 forms functional heterodimers with either SNX7 or SNX30 that associate with tubulovesicular endocytic membranes. Detailed image-based analysis during the early stages of autophagosome assembly reveals that SNX4-SNX7 is an autophagy-specific SNX-BAR heterodimer, required for efficient recruitment and/or retention of core autophagy regulators at the nascent isolation membrane. SNX4 partially colocalises with juxtanuclear ATG9A-positive membranes, with our data linking the autophagy defect upon SNX4 disruption to the mis-trafficking and/or retention of ATG9A in the Golgi region. Taken together, our findings show that the SNX4-SNX7 heterodimer coordinates ATG9A trafficking within the endocytic network to establish productive autophagosome assembly sites, thus extending knowledge of SNXs as positive regulators of autophagy.
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Affiliation(s)
- Zuriñe Antón
- Cell Biology Laboratories, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Virginie M S Betin
- Cell Biology Laboratories, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Boris Simonetti
- Henry Wellcome Integrated Signalling Laboratories, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Colin J Traer
- Henry Wellcome Integrated Signalling Laboratories, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Naomi Attar
- Henry Wellcome Integrated Signalling Laboratories, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Peter J Cullen
- Henry Wellcome Integrated Signalling Laboratories, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Jon D Lane
- Cell Biology Laboratories, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
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9
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Simonetti B, Cullen PJ. Actin-dependent endosomal receptor recycling. Curr Opin Cell Biol 2018; 56:22-33. [PMID: 30227382 DOI: 10.1016/j.ceb.2018.08.006] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 08/20/2018] [Accepted: 08/27/2018] [Indexed: 12/18/2022]
Abstract
Endosomes constitute major sorting compartments within the cell. There, a myriad of transmembrane proteins (cargoes) are delivered to the lysosome for degradation or retrieved from this fate and recycled through tubulo-vesicular transport carriers to different cellular destinations. Retrieval and recycling are orchestrated by multi-protein assemblies that include retromer and retriever, sorting nexins, and the Arp2/3 activating WASH complex. Fine-tuned control of actin polymerization on endosomes is fundamental for the retrieval and recycling of cargoes. Recent advances in the field have highlighted several roles that actin plays in this process including the binding to cargoes, stabilization of endosomal subdomains, generation of the remodeling forces required for the biogenesis of cargo-enriched transport carriers and short-range motility of the transport carriers.
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Affiliation(s)
- Boris Simonetti
- School of Biochemistry, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Peter J Cullen
- School of Biochemistry, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK.
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10
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Simonetti B, Danson CM, Heesom KJ, Cullen PJ. Sequence-dependent cargo recognition by SNX-BARs mediates retromer-independent transport of CI-MPR. J Cell Biol 2017; 216:3695-3712. [PMID: 28935633 PMCID: PMC5674890 DOI: 10.1083/jcb.201703015] [Citation(s) in RCA: 120] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 07/19/2017] [Accepted: 08/11/2017] [Indexed: 12/11/2022] Open
Abstract
Endosomal recycling of transmembrane proteins requires sequence-dependent recognition of motifs present within their intracellular cytosolic domains. In this study, we have reexamined the role of retromer in the sequence-dependent endosome-to-trans-Golgi network (TGN) transport of the cation-independent mannose 6-phosphate receptor (CI-MPR). Although the knockdown or knockout of retromer does not perturb CI-MPR transport, the targeting of the retromer-linked sorting nexin (SNX)-Bin, Amphiphysin, and Rvs (BAR) proteins leads to a pronounced defect in CI-MPR endosome-to-TGN transport. The retromer-linked SNX-BAR proteins comprise heterodimeric combinations of SNX1 or SNX2 with SNX5 or SNX6 and serve to regulate the biogenesis of tubular endosomal sorting profiles. We establish that SNX5 and SNX6 associate with the CI-MPR through recognition of a specific WLM endosome-to-TGN sorting motif. From validating the CI-MPR dependency of SNX1/2-SNX5/6 tubular profile formation, we provide a mechanism for coupling sequence-dependent cargo recognition with the biogenesis of tubular profiles required for endosome-to-TGN transport. Therefore, the data presented in this study reappraise retromer's role in CI-MPR transport.
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Affiliation(s)
- Boris Simonetti
- School of Biochemistry, University of Bristol, Bristol, England, UK
| | - Chris M Danson
- School of Biochemistry, University of Bristol, Bristol, England, UK
| | - Kate J Heesom
- Proteomics Facility, School of Biochemistry, University of Bristol, Bristol, England, UK
| | - Peter J Cullen
- School of Biochemistry, University of Bristol, Bristol, England, UK
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11
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Saccone G, Simonetti B, Berghella V. Transvaginal ultrasound cervical length for prediction of spontaneous labour at term: a systematic review and meta-analysis. BJOG 2015; 123:16-22. [PMID: 26507579 DOI: 10.1111/1471-0528.13724] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/30/2015] [Indexed: 11/26/2022]
Abstract
BACKGROUND The possibility to predict the delivery date is a question frequently raised by pregnant women. However, a clinician has currently little to predict when a woman at term will deliver. OBJECTIVE To evaluate the predictive accuracy of transvaginal ultrasound (TVU) cervical length (CL) for spontaneous onset of labour in singleton gestation enrolled at term by a meta-analysis. SEARCH STRATEGY We performed a literature search in electronic databases. SELECTION CRITERIA We included only studies assessing the accuracy of TVU CL in prediction of spontaneous onset of labour in singleton gestations with vertex presentation who were enrolled at term. DATA COLLECTION AND ANALYSIS The primary outcome was the accuracy of CL for prediction of spontaneous labour within 7 days. Pooled sensitivities and specificities were calculated. MAIN RESULTS Five studies including 735 singleton gestations were included. For the prediction of spontaneous labour within 7 days for CL <30 mm the pooled sensitivity was 64% and pooled specificity was 60%. The higher the CL, the better the sensitivity; the lower the CL, the better the specificity. A woman with a singleton gestation at term and a TVU CL of 30 mm has a <50% chance of delivering within 7 days, while one with a TVU CL of 10 mm has an over 85% chance of delivery within 7 days. CONCLUSIONS TVU CL at term has moderate value in predicting the onset of spontaneous labour. A woman with a TVU CL of 10 mm or less has a high chance of delivering within a week. TWEETABLE ABSTRACT Cervical length at term has moderate value in predicting the onset of spontaneous labour.
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Affiliation(s)
- G Saccone
- Department of Neuroscience, Reproductive Sciences and Dentistry, School of Medicine, University of Naples Federico II, Naples, Italy
| | - B Simonetti
- Department of Law, Economics, Management and Quantitative Methods, University of Sannio, Benevento, Italy
| | - V Berghella
- Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Sidney Kimmel Medical College of Thomas Jefferson University, Philadelphia, PA, USA
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12
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Carotti M, Salaffi F, Manganelli P, Salera D, Simonetti B, Grassi W. Power Doppler sonography in the assessment of synovial tissue of the knee joint in rheumatoid arthritis: a preliminary experience. Ann Rheum Dis 2002; 61:877-82. [PMID: 12228155 PMCID: PMC1753902 DOI: 10.1136/ard.61.10.877] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
OBJECTIVE To investigate the intra-articular vascularisation of the synovial pannus in the knee of patients with rheumatoid arthritis (RA) with power Doppler ultrasonography (PDS) and an echo contrast agent and correlate the area under the time-intensity curves with the clinical findings and laboratory measures of disease activity. METHOD Forty two patients with RA (31 women, 11 men) with history and signs of knee arthritis, classified according to a modified index of synovitis activity (active, moderately active, and inactive), were studied. Clinical and functional assessment (number of swollen joints, intensity of pain, general health-visual analogue scale, disability index-Health Assessment Questionnaire, Ritchie articular index) and a laboratory evaluation were made on all patients. Disease activity was evaluated using the disease activity score (DAS) and the chronic arthritis systemic index (CASI) for each patient. All patients were examined with conventional ultrasonography and PDS before injection of intravenous ultrasound contrast agent (Levovist). The quantitative estimation of the vascularisation of the synovial membrane was performed with time-intensity curves and calculation of the area under the curves. RESULTS The mean (SD) value of the area underlying time-intensity curves was 216.2 (33.4) in patients with active synovitis, 186.8 (25.8) in patients with moderately active synovitis, and 169.6 (20.6) in those with inactive synovitis. The mean value of the areas differed significantly between the patients with active and those with inactive synovitis (p<0.01). The mean value of the area under the curve of the entire group was weakly correlated with the number of swollen joints (p=0.038), but a strong correlation was found with composite indexes of disease activity such as the DAS (p=0.006) and CASI (p=0.01). No correlation was found with age, disease duration, and other laboratory and clinical variables. CONCLUSION PDS may be a valuable tool to detect fractional vascular volume and to assist clinicians in distinguishing between inflammatory and non-inflammatory pannus. The transit of microbubbles of ultrasound contrast across a tissue can be used to estimate haemodynamic alterations and may have a role in assessing synovial activity and the therapeutic response to treatment of synovitis of the knee joint.
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Affiliation(s)
- M Carotti
- Department of Radiology, University of Ancona, Italy
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Perugi G, Toni C, Benedetti A, Simonetti B, Simoncini M, Torti C, Musetti L, Akiskal HS. Delineating a putative phobic-anxious temperament in 126 panic-agoraphobic patients: toward a rapprochement of European and US views. J Affect Disord 1998; 47:11-23. [PMID: 9476739 DOI: 10.1016/s0165-0327(97)00108-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND The current US official position, since DSM-III, is that panic attacks represent the hallmark of panic disorder and play a major role in the development of the agoraphobic syndrome. The more favoured view in the European tradition is that neurotic personality and/or prodromal features such as mild depression and excessive worries precede the illness. METHOD We studied 126 consecutive cases of panic disorder with or without agoraphobia by DSM-III-R criteria, evaluated by relevant structured and semi-structured interviews. RESULTS We provide evidence that characterological and prodromal antecedents represent a putative phobic-anxious temperamental substrate occurring in at least 30% of our sample. This temperament consists of three or more of the following traits: (1) increased sympathetic activity with repeated sporadic and isolated autonomic manifestations; (2) marked fear of illness; (3) hypersensitivity to separation; (4) difficulty to leave familiar surroundings; (5) marked need for reassurance; (6) oversensitivity to drugs and substances. Our data further suggest that these attributes are of familial origin, as a result of which the illness tends to declare itself earlier. LIMITATION The present investigation is largely correlational without a prospective component; however, the key validating familial data were obtained blindly. CONCLUSION Our data support a pathogenetic model whereby genetic diathesis unfolds from subclinical to clinical manifestations along temperamental, panic, phobic and avoidant patterns. We submit that the delineation of the phobic-anxious temperament will be useful in more completely charting the life course of the panic-agoraphobic spectrum; avoidant and dependent (Axis II) patterns appear more distal in the pathogenetic chain and, in many cases, can be conceptualized to be epiphenomenal to the disease process.
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Affiliation(s)
- G Perugi
- Institute of Psychiatry, University of Pisa, Italy
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14
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Abstract
In a sample of 131 patients with panic disorder, we explored both the presence of DSM-III-R criteria for hypochondriasis and the occurrence of illness phobia before the onset of panic disorder. To explore further the possible relationship between hypochondriacal features and panic-agoraphobic syndrome, we compared patients both with and without current hypochondriasis and then patients both with and without illness phobia before the onset of panic disorder. Finally, we investigated the relationship between premorbid phobic-anxious traits and hypochondriasis during panic disorder. No differences were found between patients with and without hypochondriasis, either in terms of clinical features or in the course of panic disorder. Patients with illness phobia before the onset of panic disorder reported higher levels of anticipatory anxiety in nonagoraphobic situations and more depersonalization and derealization during panic attacks, and they met our definition of phobic-anxious temperament more frequently than the rest of the sample. This would suggest that illness phobia before the onset of panic disorder may be viewed either as a separate disorder, a prodrome, or a mild, early-onset form of panic disorder without full-blown attacks. Although patients with premorbid illness phobia are more likely to develop hypochondriasis after the onset of panic disorder, approximately 40% of them do not; therefore, illness phobia should not be considered the only factor that influences the development of hypochondriasis during panic disorder.
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Affiliation(s)
- A Benedetti
- Psychiatric Clinic, University of Pisa, Italy
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15
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Di Mario U, Bacci S, Morano S, Pugliese G, Pietravalle P, Andreani D, Morabito S, Simonetti B, Pierucci A. Selective decrement of anionic immunoglobulin clearance after induced renal hemodynamic changes in diabetic patients. Am J Physiol 1992; 262:F381-8. [PMID: 1558156 DOI: 10.1152/ajprenal.1992.262.3.f381] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The charge permselectivity of proteins was evaluated in diabetic patients after systemic and renal hemodynamic changes induced by an intravenous injection of an angiotensin-converting enzyme inhibitor (captopril) or of clonidine. Anionic immunoglobulin clearance (IgG4) was compared with that of total immunoglobulins, which have the same size but are mostly cationic, and of albumin. Ten type I hypertensive diabetic patients (group 1), 10 type 2 hypertensive diabetic patients (group 2), 5 type 1 normotensive diabetic patients (group 3), 10 subjects with essential hypertension (group 4), and 7 normal volunteers (group 5) received an intravenous injection of captopril (25 mg/100 ml in 5 min). Twelve of the hypertensive diabetic patients underwent a second provocative test with clonidine (150 micrograms/100 ml) (group 6) or placebo (100 ml saline) (group 7) with the same procedure. None of the patients had clinical nephropathy or other disorders. Glomerular filtration rate (GFR) and renal plasma flow (RPF) were measured before and during the tests. A significant decrease in diastolic blood pressure was observed in groups 1, 2, 4, and 6, together with an increase in the GFR and RPF values in groups 1, 2, 3, and 4 only, as well as a decrease in renal vascular resistances in groups 1, 2, 3, 4, and 6. Both clearances and fractional clearances of IgG4 and IgG decreased after captopril in groups 1 and 2.2+ The decrease in IgG4 clearance was correlated to that of renal vascular resistances in group 1 patients. A significant decrease in the anionic-cationic immunoglobulin ratio (IgG4/IgG) was observed in groups 1, 2, and 3.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- U Di Mario
- Department of Endocrinology, University La Sapienza, Rome, Italy
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Pisapia A, Leheuzey JY, Faure J, Simonetti B, Szatmary L, Carta M, Rosario R, Barnay C, Duport G. Sino-atrial dissociation: evidence by intracardiac recordings in man and by microelectrode studies on isolated rabbit atrium. Pacing Clin Electrophysiol 1988; 11:23-32. [PMID: 2449670 DOI: 10.1111/j.1540-8159.1988.tb03927.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The electrophysiologic mechanisms of sinus dysfunction have recently been determined by direct recordings of the sinus node electrogram. The association of various degrees of abnormalities in the formation of the impulse within the sinus node and of sinoatrial conduction block, represents the pathophysiological substrate of the mechanism of sinus node dysfunction. The purpose of this work is to present clinical and experimental data supporting the concept of sinus node isolation. In our clinical case, the sinus node was probably intact despite aspects of sinus node dysfunction on the surface ECG. Sinus node electrograms were recorded with a sinoatrial conduction time of 100 ms (normal values in our laboratory: 83 ms +/- 38 ms). Atrial mapping demonstrated that the area depolarized by the sinus node involved a 2 cm2 zone surrounding it. This perisinusal activity could not be recorded on the surface ECG. Both exit and entry blocks in the sinus node were demonstrated. Our experimental data showed a total desynchronization between the electrical activity of the sinus node and that of the atrium under hypoxic conditions. Both types of cases demonstrated that an atrial dysrhythmia was coexisting with regular sinus activity. From these data we concluded that a sinus node free from any pathological involvement could be associated with severe symptoms of sinus node dysfunction on the surface ECG.
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Affiliation(s)
- A Pisapia
- Department of Cardiology, Saint-Joseph's Hospital, Marseille, France
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Pisapia A, Faure J, Simonetti B, Szatmary L, Barnay C, Blache E, Delaage M. [Sinoatrial and intra-atrial conductive disorders. The value of recording the sinus node potential]. Arch Mal Coeur Vaiss 1984; 77:665-672. [PMID: 6431931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Direct recording of the sinus node potential in the bipolar mode using two electrodes of a quadripolar recording catheter positioned in the region of the sinus node at the junction of the superior vena cava to the right atrium was performed in 24 patients. Asynchronous overdrive atrial pacing was carried out using Strauss 'technique. Pharmacological denervation was carried out using intravenous propranolol (0,02 mg/kg) and atropine (0,04 mg/kg) using Jose's technique. An intravenous injection of a bolus of 20 mg of ATP was given in 3 cases. The sinus potential was identified by morphological criteria and confirmed after carotid sinus compression and atrial extrastimuli to exclude artefacts, especially the end of ventricular repolarisation of the preceding complex. The sinoatrial conduction time measured directly under basal conditions was considered normal when within 80 to 150 ms. Direct measurement of the sinus potential in the diagnosis of sinus node dysfunction seems to be less useful than the indirect techniques. On the other hand, it does confirm the diagnosis of sinoatrial block: five cases of special interest are described; in four cases the degree of sinoatrial block was variable: a significant increase of sinoatrial conduction time under basal conditions in 1 case; paroxysmal 3rd degree sinoatrial block revealed by programmed atrial stimulation in 2 cases; 2nd degree 2/1 sinoatrial block after injection of ATP in which the direct sinoatrial conduction time and sinus node function had been considered to be normal (1 case).(ABSTRACT TRUNCATED AT 250 WORDS)
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