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Zheng W, Chang IC, Limberis J, Budzik JM, Zha BS, Howard Z, Chen L, Ernst JD. Mycobacterium tuberculosis resides in lysosome-poor monocyte-derived lung cells during chronic infection. PLoS Pathog 2024; 20:e1012205. [PMID: 38701094 PMCID: PMC11095722 DOI: 10.1371/journal.ppat.1012205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 05/15/2024] [Accepted: 04/19/2024] [Indexed: 05/05/2024] Open
Abstract
Mycobacterium tuberculosis (Mtb) infects lung myeloid cells, but the specific Mtb-permissive cells and host mechanisms supporting Mtb persistence during chronic infection are incompletely characterized. We report that after the development of T cell responses, CD11clo monocyte-derived cells harbor more live Mtb than alveolar macrophages (AM), neutrophils, and CD11chi monocyte-derived cells. Transcriptomic and functional studies revealed that the lysosome pathway is underexpressed in this highly permissive subset, characterized by less lysosome content, acidification, and proteolytic activity than AM, along with less nuclear TFEB, a regulator of lysosome biogenesis. Mtb infection does not drive lysosome deficiency in CD11clo monocyte-derived cells but promotes recruitment of monocytes that develop into permissive lung cells, mediated by the Mtb ESX-1 secretion system. The c-Abl tyrosine kinase inhibitor nilotinib activates TFEB and enhances lysosome functions of macrophages in vitro and in vivo, improving control of Mtb infection. Our results suggest that Mtb exploits lysosome-poor lung cells for persistence and targeting lysosome biogenesis is a potential host-directed therapy for tuberculosis.
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Affiliation(s)
- Weihao Zheng
- Division of Experimental Medicine, Department of Medicine, University of California, San Francisco, California, United States of America
| | - I-Chang Chang
- Division of Experimental Medicine, Department of Medicine, University of California, San Francisco, California, United States of America
| | - Jason Limberis
- Division of Experimental Medicine, Department of Medicine, University of California, San Francisco, California, United States of America
| | - Jonathan M. Budzik
- Division of Pulmonary, Critical Care, Allergy and Sleep Medicine, Department of Medicine, University of California, San Francisco, California, United States of America
| | - Beth Shoshana Zha
- Division of Experimental Medicine, Department of Medicine, University of California, San Francisco, California, United States of America
- Division of Pulmonary, Critical Care, Allergy and Sleep Medicine, Department of Medicine, University of California, San Francisco, California, United States of America
| | - Zachary Howard
- Division of Experimental Medicine, Department of Medicine, University of California, San Francisco, California, United States of America
| | - Lucas Chen
- Division of Experimental Medicine, Department of Medicine, University of California, San Francisco, California, United States of America
| | - Joel D. Ernst
- Division of Experimental Medicine, Department of Medicine, University of California, San Francisco, California, United States of America
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2
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Kadhim DJ, Azari H, Sokhangouy SK, Hassanian SM, Alshekarchi HI, Goshayeshi L, Goshayeshi L, Abbaszadegan MR, Khojasteh-Leylakoohi F, Khazaei M, Gataa IS, Peters GJ, A. Ferns G, Batra J, Lam AKY, Giovannetti E, Avan A. G-Protein Signaling Modulator 2 as a Potential Biomarker in Colorectal Cancer: Integrative Analysis Using Genetic Profiling and Pan-Cancer Studies. Genes (Basel) 2024; 15:474. [PMID: 38674408 PMCID: PMC11050220 DOI: 10.3390/genes15040474] [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: 03/02/2024] [Revised: 04/06/2024] [Accepted: 04/06/2024] [Indexed: 04/28/2024] Open
Abstract
Colorectal cancer (CRC) imposes a significant healthcare burden globally, prompting the quest for innovative biomarkers to enhance diagnostic and therapeutic strategies. This study investigates the G-protein signaling modulator (GPSM) family across several cancers and presents a comprehensive pan-cancer analysis of the GPSM2 gene across several gastrointestinal (GI) cancers. Leveraging bioinformatics methodologies, we investigated GPSM2 expression patterns, protein interactions, functional enrichments, prognostic implications, genetic alterations, and immune infiltration associations. Furthermore, the expression of the GPSM2 gene was analyzed using real-time analysis. Our findings reveal a consistent upregulation of GPSM2 expression in all GI cancer datasets analyzed, suggesting its potential as a universal biomarker in GI cancers. Functional enrichment analysis underscores the involvement of GPSM2 in vital pathways, indicating its role in tumor progression. The prognostic assessment indicates that elevated GPSM2 expression correlates with adverse overall and disease-free survival outcomes across multiple GI cancer types. Genetic alteration analysis highlights the prevalence of mutations, particularly missense mutations, in GPSM2. Furthermore, significant correlations between GPSM2 expression and immune cell infiltration are observed, suggesting its involvement in tumor immune evasion mechanisms. Collectively, our study underscores the multifaceted role of GPSM2 in GI cancers, particularly in CRC, emphasizing its potential as a promising biomarker for prognosis and therapeutic targeting. Further functional investigations are warranted to elucidate its clinical utility and therapeutic implications in CRC management.
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Affiliation(s)
- Doaa Jawad Kadhim
- Metabolic Syndrome Research Center, Mashhad University of Medical Sciences, Mashhad 91779-48564, Iran (H.A.); (S.M.H.); (F.K.-L.); (M.K.)
| | - Hanieh Azari
- Metabolic Syndrome Research Center, Mashhad University of Medical Sciences, Mashhad 91779-48564, Iran (H.A.); (S.M.H.); (F.K.-L.); (M.K.)
| | - Saeideh Khorshid Sokhangouy
- Medical Genetics Research Center, Mashhad University of Medical Sciences, Mashhad 91886-17871, Iran; (S.K.S.); (M.R.A.)
| | - Seyed Mahdi Hassanian
- Metabolic Syndrome Research Center, Mashhad University of Medical Sciences, Mashhad 91779-48564, Iran (H.A.); (S.M.H.); (F.K.-L.); (M.K.)
| | - Hawraa Ibrahim Alshekarchi
- Al-Zahraa Center for Medical and Pharmaceutical Research Sciences (ZCMRS), Al-Zahraa University for Women, Kerbala 56001, Iraq
| | - Ladan Goshayeshi
- Department of Gastroenterology and Hepatology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad 91779-48564, Iran;
- Surgical Oncology Research Center, Mashhad University of Medical Sciences, Mashhad 91779-48954, Iran
| | - Lena Goshayeshi
- Surgical Oncology Research Center, Mashhad University of Medical Sciences, Mashhad 91779-48954, Iran
| | - Mohammad Reza Abbaszadegan
- Medical Genetics Research Center, Mashhad University of Medical Sciences, Mashhad 91886-17871, Iran; (S.K.S.); (M.R.A.)
| | - Fatemeh Khojasteh-Leylakoohi
- Metabolic Syndrome Research Center, Mashhad University of Medical Sciences, Mashhad 91779-48564, Iran (H.A.); (S.M.H.); (F.K.-L.); (M.K.)
| | - Majid Khazaei
- Metabolic Syndrome Research Center, Mashhad University of Medical Sciences, Mashhad 91779-48564, Iran (H.A.); (S.M.H.); (F.K.-L.); (M.K.)
| | | | - Godefridus J. Peters
- Department of Biochemistry, Medical University of Gdansk, 80-211 Gdansk, Poland;
- Cancer Center Amsterdam, Cancer Biology and Immunology, Amsterdam UMC, Vrije Universiteit, Department of Medical Oncology, 1081 HV Amsterdam, The Netherlands
| | - Gordon A. Ferns
- Department of Medical Education, Brighton & Sussex Medical School, Falmer, Brighton BN1 9PH, UK;
| | - Jyotsna Batra
- Faculty of Health, School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia;
| | - Alfred King-Yin Lam
- Pathology, School of Medicine and Dentistry, Gold Coast Campus, Griffith University, Gold Coast, QLD 4222, Australia;
| | - Elisa Giovannetti
- Cancer Center Amsterdam, Cancer Biology and Immunology, Amsterdam UMC, Vrije Universiteit, Department of Medical Oncology, 1081 HV Amsterdam, The Netherlands
- Cancer Pharmacology Laboratory, AIRC Start Up Unit, Fondazione Pisana per La Scienza, 56017 Pisa, Italy
| | - Amir Avan
- Metabolic Syndrome Research Center, Mashhad University of Medical Sciences, Mashhad 91779-48564, Iran (H.A.); (S.M.H.); (F.K.-L.); (M.K.)
- Faculty of Health, School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia;
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3
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Vural A, Lanier SM. Properties of biomolecular condensates defined by Activator of G-protein Signaling 3. J Cell Sci 2024; 137:jcs261326. [PMID: 38264908 PMCID: PMC10911133 DOI: 10.1242/jcs.261326] [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: 05/12/2023] [Accepted: 01/11/2024] [Indexed: 01/25/2024] Open
Abstract
Activator of G-protein signaling 3 (AGS3; also known as GPSM1), a receptor-independent activator of G-protein signaling, oscillates among defined subcellular compartments and biomolecular condensates (BMCs) in a regulated manner that is likely related to the functional diversity of the protein. We determined the influence of cell stress on the cellular distribution of AGS3 and core material properties of AGS3 BMCs. Cellular stress (oxidative, pHi and thermal) induced the formation of AGS3 BMCs in HeLa and COS-7 cells, as determined by fluorescent microscopy. Oxidative stress-induced AGS3 BMCs were distinct from G3BP1 stress granules and from RNA processing BMCs defined by the P-body protein Dcp1a. Immunoblots indicated that cellular stress shifted AGS3, but not the stress granule protein G3BP1 to a membrane pellet fraction following cell lysis. The stress-induced generation of AGS3 BMCs was reduced by co-expression of the signaling protein Gαi3, but not the AGS3-binding partner DVL2. Fluorescent recovery following photobleaching of individual AGS3 BMCs indicated that there are distinct diffusion kinetics and restricted fluidity for AGS3 BMCs. These data suggest that AGS3 BMCs represent a distinct class of stress granules that serve as a previously unrecognized signal processing node.
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Affiliation(s)
- Ali Vural
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Stephen M. Lanier
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201, USA
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4
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Zheng W, Chang IC, Limberis J, Budzik J, Zha BS, Howard Z, Chen L, Ernst J. Mycobacterium tuberculosis resides in lysosome-poor monocyte-derived lung cells during chronic infection. RESEARCH SQUARE 2023:rs.3.rs-3049913. [PMID: 37398178 PMCID: PMC10312915 DOI: 10.21203/rs.3.rs-3049913/v1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Mycobacterium tuberculosis (Mtb) persists in lung myeloid cells during chronic infection. However, the mechanisms allowing Mtb to evade elimination are not fully understood. Here, we determined that in chronic phase, CD11clo monocyte-derived lung cells termed MNC1 (mononuclear cell subset 1), harbor more live Mtb than alveolar macrophages (AM), neutrophils, and less permissive CD11chi MNC2. Transcriptomic and functional studies of sorted cells revealed that the lysosome biogenesis pathway is underexpressed in MNC1, which have less lysosome content, acidification, and proteolytic activity than AM, and less nuclear TFEB, a master regulator of lysosome biogenesis. Mtb infection does not drive lysosome deficiency in MNC1. Instead, Mtb recruits MNC1 and MNC2 to the lungs for its spread from AM to these cells via its ESX-1 secretion system. The c-Abl tyrosine kinase inhibitor nilotinib activates TFEB and enhances lysosome function of primary macrophages and MNC1 and MNC2 in vivo, improving control of Mtb infection. Our results indicate that Mtb exploits lysosome-poor monocyte-derived cells for in vivo persistence, suggesting a potential target for host-directed tuberculosis therapy.
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5
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Zheng W, Chang IC, Limberis J, Budzik JM, Zha BS, Howard Z, Chen L, Ernst JD. Mycobacterium tuberculosis resides in lysosome-poor monocyte-derived lung cells during chronic infection. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.19.524758. [PMID: 36711606 PMCID: PMC9882350 DOI: 10.1101/2023.01.19.524758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Mycobacterium tuberculosis (Mtb) infects cells in multiple lung myeloid cell subsets and causes chronic infection despite innate and adaptive immune responses. However, the mechanisms allowing Mtb to evade elimination are not fully understood. Here, using new methods, we determined that after T cell responses have developed, CD11clo monocyte-derived lung cells termed MNC1 (mononuclear cell subset 1), harbor more live Mtb compared to alveolar macrophages (AM), neutrophils, and less permissive CD11chi MNC2. Bulk RNA sequencing of sorted cells revealed that the lysosome biogenesis pathway is underexpressed in MNC1. Functional assays confirmed that Mtb-permissive MNC1 have less lysosome content, acidification, and proteolytic activity than AM, and less nuclear TFEB, a master regulator of lysosome biogenesis. Mtb infection does not drive lysosome deficiency in MNC1 in vivo. Instead, Mtb recruits MNC1 and MNC2 to the lungs for its spread from AM to these cell subsets as a virulence mechanism that requires the Mtb ESX-1 secretion system. The c-Abl tyrosine kinase inhibitor nilotinib activates TFEB and enhances lysosome function of primary macrophages in vitro and MNC1 and MNC2 in vivo, improving control of Mtb infection. Our results indicate that Mtb exploits lysosome-poor monocyte-derived cells for in vivo persistence, suggesting a potential target for host-directed tuberculosis therapy.
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Affiliation(s)
- Weihao Zheng
- Division of Experimental Medicine, Department of Medicine, University of California, San Francisco, California, USA
| | - I-Chang Chang
- Division of Experimental Medicine, Department of Medicine, University of California, San Francisco, California, USA
| | - Jason Limberis
- Division of Experimental Medicine, Department of Medicine, University of California, San Francisco, California, USA
| | - Jonathan M. Budzik
- Division of Pulmonary, Critical Care, Allergy and Sleep Medicine, Department of Medicine, University of California, San Francisco, California, USA
| | - B. Shoshana Zha
- Division of Experimental Medicine, Department of Medicine, University of California, San Francisco, California, USA
- Division of Pulmonary, Critical Care, Allergy and Sleep Medicine, Department of Medicine, University of California, San Francisco, California, USA
| | - Zach Howard
- Division of Experimental Medicine, Department of Medicine, University of California, San Francisco, California, USA
| | - Lucas Chen
- Division of Experimental Medicine, Department of Medicine, University of California, San Francisco, California, USA
| | - Joel D. Ernst
- Division of Experimental Medicine, Department of Medicine, University of California, San Francisco, California, USA
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6
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GPSM1 impairs metabolic homeostasis by controlling a pro-inflammatory pathway in macrophages. Nat Commun 2022; 13:7260. [PMID: 36434066 PMCID: PMC9700814 DOI: 10.1038/s41467-022-34998-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 11/15/2022] [Indexed: 11/27/2022] Open
Abstract
G-protein-signaling modulator 1 (GPSM1) exhibits strong genetic association with Type 2 diabetes (T2D) and Body Mass Index in population studies. However, how GPSM1 carries out such control and in which types of cells are poorly understood. Here, we demonstrate that myeloid GPSM1 promotes metabolic inflammation to accelerate T2D and obesity development. Mice with myeloid-specific GPSM1 ablation are protected against high fat diet-induced insulin resistance, glucose dysregulation, and liver steatosis via repression of adipose tissue pro-inflammatory states. Mechanistically, GPSM1 deficiency mainly promotes TNFAIP3 transcription via the Gαi3/cAMP/PKA/CREB axis, thus inhibiting TLR4-induced NF-κB signaling in macrophages. In addition, we identify a small-molecule compound, AN-465/42243987, which suppresses the pro-inflammatory phenotype by inhibiting GPSM1 function, which could make it a candidate for metabolic therapy. Furthermore, GPSM1 expression is upregulated in visceral fat of individuals with obesity and is correlated with clinical metabolic traits. Overall, our findings identify macrophage GPSM1 as a link between metabolic inflammation and systemic homeostasis.
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7
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Najibi M, Honwad HH, Moreau JA, Becker SM, Irazoqui JE. A NOVEL NOX/PHOX-CD38-NAADP-TFEB AXIS IMPORTANT FOR MACROPHAGE ACTIVATION DURING BACTERIAL PHAGOCYTOSIS. Autophagy 2021; 18:124-141. [PMID: 33818279 PMCID: PMC8865266 DOI: 10.1080/15548627.2021.1911548] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Macrophage activation in the presence of bacterial cells and molecules entails complex programs of gene expression. How such triggers elicit specific gene expression programs is incompletely understood. We previously discovered that TFEB (transcription factor EB) is a key contributor to macrophage activation during bacterial phagocytosis. However, the mechanism linking phagocytosis of bacterial cells to TFEB activation and downstream pro-inflammatory cytokine induction remained unknown. We found that macrophages lacking both TFEB and TFE3 (transcription factor E3) were unable to mount a pro-inflammatory phenotype in response to bacterial infection. The NOX/PHOX (NADPH oxidase)-dependent oxidative burst was required for nuclear translocation of TFEB during phagocytosis of Gram-positive or -negative bacteria, and reactive oxygen species (ROS) were sufficient to trigger TFEB activation in a CD38- and NAADP (nicotinic acid adenine dinucleotide phosphate)-dependent manner. Consistent with the Ca2+-releasing activity of NAADP, intracellular Ca2+ chelation and PPP3/calcineurin inhibition prevented TFEB activation by phagocytosis and ROS (reactive oxygen species), impairing the induction of pro-inflammatory cytokines such as IL6 and TNF/TNFα. Therefore, here we describe a previously unknown pathway that links phagocytosis with macrophage pro-inflammatory polarization via TFEB and related transcription factor TFE3. These findings reveal that activation of TFEB and TFE3 is a key regulatory event for the activation of macrophages, and have important implications for infections, inflammation, cancer, obesity, and atherosclerosis.
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Affiliation(s)
- Mehran Najibi
- Department of Microbiology and Physiological Systems and Program in Innate Immunity, University of Massachusetts Medical School, Worcester, USA.,Present Address: Department of Pathology, The Warren Alpert Medical School of Brown University, Providence
| | - Havisha H Honwad
- Department of Microbiology and Physiological Systems and Program in Innate Immunity, University of Massachusetts Medical School, Worcester, USA
| | - Joseph A Moreau
- Department of Microbiology and Physiological Systems and Program in Innate Immunity, University of Massachusetts Medical School, Worcester, USA
| | - Stephanie M Becker
- Department of Microbiology and Physiological Systems and Program in Innate Immunity, University of Massachusetts Medical School, Worcester, USA
| | - Javier E Irazoqui
- Department of Microbiology and Physiological Systems and Program in Innate Immunity, University of Massachusetts Medical School, Worcester, USA
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8
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Zhang Y, Zhou B, Sun J, He Q, Zhao Y. Knockdown of GPSM1 Inhibits the Proliferation and Promotes the Apoptosis of B-Cell Acute Lymphoblastic Leukemia Cells by Suppressing the ADCY6-RAPGEF3-JNK Signaling Pathway. Pathol Oncol Res 2021; 27:643376. [PMID: 34257610 PMCID: PMC8262160 DOI: 10.3389/pore.2021.643376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 03/01/2021] [Indexed: 12/24/2022]
Abstract
B-cell acute lymphoblastic leukemia (B-ALL) is the common type of blood cancer. Although the remission rate has increased, the current treatment options for B-ALL are usually related to adverse reactions and recurrence, so it is necessary to find other treatment options. G protein signaling modulator 1 (GPSM1) is one of several factors that affect the basic activity of the G protein signaling system, but its role in B-ALL has not yet been clarified. In this study, we analyzed the expression of GPSM1 in the Oncomine database and found that the GPSM1 levels were higher in B-ALL cells than in peripheral blood mononuclear cells (PBMCs). Analyses of the Gene Expression Profiling Interactive Analysis (GEPIA) demonstrated that patients with high GPSM1 levels had shorter survival times than those with low levels. Additionally, gene set enrichment analysis (GSEA) suggested that GPSM1 was positively correlated with proliferation, G protein-coupled receptor (GPCR) ligand binding, Gαs signaling and calcium signaling pathways. In further experiments, GPSM1 was found to be highly expressed in Acute lymphoblastic leukemia (ALL) cell lines, and downregulation of GPSM1 inhibited proliferation and promoted cell cycle arrest and apoptosis in BALL-1 and Reh cells. Moreover, knockdown of GPSM1 suppressed ADCY6 and RAPGEF3 expression in BALL-1 and Reh cells. Furthermore, we reported that GPSM1 regulated JNK expression via ADCY6-RAPGEF3. The present study demonstrates that GPSM1 promotes tumor growth in BALL-1 and Reh cells by modulating ADCY6-RAPGEF3-JNK signaling.
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Affiliation(s)
- Ye Zhang
- Key Laboratory of Cell Biology of Ministry of Public Health, and Key Laboratory of Medical Cell Biology of Ministry of Education, China Medical University, Shenyang, China.,Department of Bioinformatics, School of Life Sciences, China Medical University, Shenyang, China
| | - Bo Zhou
- Key Laboratory of Cell Biology of Ministry of Public Health, and Key Laboratory of Medical Cell Biology of Ministry of Education, China Medical University, Shenyang, China.,Department of Bioinformatics, School of Life Sciences, China Medical University, Shenyang, China
| | - Jingjing Sun
- Key Laboratory of Cell Biology of Ministry of Public Health, and Key Laboratory of Medical Cell Biology of Ministry of Education, China Medical University, Shenyang, China.,Department of Bioinformatics, School of Life Sciences, China Medical University, Shenyang, China
| | - Qun He
- Department of Bioinformatics, School of Life Sciences, China Medical University, Shenyang, China
| | - Yujie Zhao
- Key Laboratory of Cell Biology of Ministry of Public Health, and Key Laboratory of Medical Cell Biology of Ministry of Education, China Medical University, Shenyang, China
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9
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Kang Y, Wu T, He Y, He Y, Zhao D. Elf4 regulates lysosomal biogenesis and the mTOR pathway to promote clearance of Staphylococcus aureus in macrophages. FEBS Lett 2021; 595:881-891. [PMID: 33423322 DOI: 10.1002/1873-3468.14037] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 12/16/2020] [Accepted: 12/17/2020] [Indexed: 11/10/2022]
Abstract
Staphylococcus aureus is a major cause of infectious disease. Macrophages can directly destroy most of the invading bacteria through the phagolysosomal pathway. E74-like factor 4 (Elf4) is one of the important transcription factors that controls diverse pathogens, but the role of Elf4 in macrophage-mediated S. aureus eradication is unknown. Our data show that Elf4 is induced by S. aureus in macrophages. Elevated expression of Elf4 results in decreased bacterial load and inflammatory responses during S. aureus infection in vivo and in vitro. Elf4-overexpressed macrophages have decreased mTOR activity and increased lysosomal mass. Collectively, these results suggest that S. aureus induces Elf4 expression, which enhances lysosomal function and increases the capacity of macrophages to eliminate intracellular pathogens.
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Affiliation(s)
- Yanhua Kang
- Hangzhou Key Lab of Inflammation and Immunoregulation, Department of Basic Medical Science, School of Medicine, Hangzhou Normal University, China
| | - Tingyue Wu
- Hangzhou Key Lab of Inflammation and Immunoregulation, Department of Basic Medical Science, School of Medicine, Hangzhou Normal University, China
| | - Yan He
- Hangzhou Key Lab of Inflammation and Immunoregulation, Department of Basic Medical Science, School of Medicine, Hangzhou Normal University, China
| | - Yunfan He
- Hangzhou Key Lab of Inflammation and Immunoregulation, Department of Basic Medical Science, School of Medicine, Hangzhou Normal University, China
| | - Dongjiu Zhao
- Hangzhou Key Lab of Inflammation and Immunoregulation, Department of Basic Medical Science, School of Medicine, Hangzhou Normal University, China
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10
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Sachdeva K, Sundaramurthy V. The Interplay of Host Lysosomes and Intracellular Pathogens. Front Cell Infect Microbiol 2020; 10:595502. [PMID: 33330138 PMCID: PMC7714789 DOI: 10.3389/fcimb.2020.595502] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Accepted: 10/22/2020] [Indexed: 12/20/2022] Open
Abstract
Lysosomes are an integral part of the intracellular defense system against microbes. Lysosomal homeostasis in the host is adaptable and responds to conditions such as infection or nutritional deprivation. Pathogens such as Mycobacterium tuberculosis (Mtb) and Salmonella avoid lysosomal targeting by actively manipulating the host vesicular trafficking and reside in a vacuole altered from the default lysosomal trafficking. In this review, the mechanisms by which the respective pathogen containing vacuoles (PCVs) intersect with lysosomal trafficking pathways and maintain their distinctness are discussed. Despite such active inhibition of lysosomal targeting, emerging literature shows that different pathogens or pathogen derived products exhibit a global influence on the host lysosomal system. Pathogen mediated lysosomal enrichment promotes the trafficking of a sub-set of pathogens to lysosomes, indicating heterogeneity in the host-pathogen encounter. This review integrates recent advancements on the global lysosomal alterations upon infections and the host protective role of the lysosomes against these pathogens. The review also briefly discusses the heterogeneity in the lysosomal targeting of these pathogens and the possible mechanisms and consequences.
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11
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Vural A, Lanier SM. Intersection of two key signal integrators in the cell: activator of G-protein signaling 3 and dishevelled-2. J Cell Sci 2020; 133:jcs247908. [PMID: 32737219 PMCID: PMC7490517 DOI: 10.1242/jcs.247908] [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: 04/21/2020] [Accepted: 07/23/2020] [Indexed: 10/23/2022] Open
Abstract
Activator of G-protein signaling 3 (AGS3, encoded by GPSM1) was discovered as a one of several receptor-independent activators of G-protein signaling, which are postulated to provide a platform for divergence between canonical and noncanonical G-protein signaling pathways. Similarly, Dishevelled (DVL) proteins serve as a point of divergence for β-catenin-dependent and -independent signaling pathways involving the family of Frizzled (FZD) ligands and cell-surface WNT receptors. We recently discovered the apparent regulated localization of dishevelled-2 (DVL2) and AGS3 to distinct cellular puncta, suggesting that the two proteins interact as part of various cell signaling systems. To address this hypothesis, we asked the following questions: (1) do AGS3 signaling pathways influence the activation of β-catenin (CTNNB1)-regulated transcription through the WNT-Frizzled-Dishevelled axis, and (2) is the AGS3 and DVL2 interaction regulated? The interaction of AGS3 and DVL2 was regulated by protein phosphorylation, subcellular distribution, and a cell-surface G-protein-coupled receptor. These data, and the commonality of functional system impacts observed for AGS3 and DVL2, suggest that the AGS3-DVL2 complex presents an unexpected path for functional integration within the cell.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Ali Vural
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Stephen M Lanier
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201, USA
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12
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Adekoya TO, Smith N, Aladeniyi T, Blumer JB, Chen XL, Richardson RM. Activator of G protein signaling 3 modulates prostate tumor development and progression. Carcinogenesis 2020; 40:1504-1513. [PMID: 31215992 DOI: 10.1093/carcin/bgz076] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 04/05/2019] [Accepted: 04/22/2019] [Indexed: 12/24/2022] Open
Abstract
Prostate cancer (PCa) is a leading cause of cancer death among men, with greater prevalence of the disease among the African American population in the USA. Activator of G-protein signaling 3 (AGS3/G-protein signaling modulator 1) was shown to be overexpressed in prostate adenocarcinoma relative to the prostate gland. In this study, we investigated the correlation between AGS3 overexpression and PCa malignancy. Immunoblotting analysis and real-time quantitative-PCR showed increase in AGS3 expression in the metastatic cell lines LNCaP (~3-fold), MDA PCa 2b (~2-fold), DU 145 (~2-fold) and TRAMP-C1 (~20-fold) but not in PC3 (~1-fold), relative to control RWPE-1. Overexpression of AGS3 in PC3, LNCaP and MDA PCa 2b enhanced tumor growth. AGS3 contains seven tetratricopeptide repeats (TPR) and four G-protein regulatory (GPR) motifs. Overexpression of the TPR or the GPR motifs in PC3 cells had no effect in tumor growth. Depletion of AGS3 in the TRAMP-C1 cells (TRAMP-C1-AGS3-/-) decreased cell proliferation and delayed wound healing and tumor growth in both C57BL/6 (~3-fold) and nude mice xenografts, relative to control TRAMP-C1 cells. TRAMP-C1-AGS3-/- tumors also exhibited a marked increase (~5-fold) in both extracellular signal-regulated kinase (ERK) 1/2 and P38 mitogen-activated protein kinase (MAPK) activation, which correlated with a significant increase (~3-fold) in androgen receptor (AR) expression, relative to TRAMP-C1 xenografts. Interestingly, overexpression of AGS3 in TRAMP-C1-AGS3-/- cells inhibited ERK activation and AR overexpression as compared with control TRAMP-C1 cells. Taken together, the data indicate that the effect of AGS3 in prostate cancer development and progression is probably mediated via a MAPK/AR-dependent pathway.
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Affiliation(s)
- Timothy O Adekoya
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA.,Department of Biological and Biomedical Sciences, North Carolina Central University, Durham, NC, USA
| | - Nikia Smith
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA
| | - Temilade Aladeniyi
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA
| | - Joe B Blumer
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston, SC, USA
| | - Xiaoxin L Chen
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA.,Department of Biological and Biomedical Sciences, North Carolina Central University, Durham, NC, USA
| | - Ricardo M Richardson
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA.,Department of Biological and Biomedical Sciences, North Carolina Central University, Durham, NC, USA
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13
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The Effect of the Chorion on Size-Dependent Acute Toxicity and Underlying Mechanisms of Amine-Modified Silver Nanoparticles in Zebrafish Embryos. Int J Mol Sci 2020; 21:ijms21082864. [PMID: 32325940 PMCID: PMC7215958 DOI: 10.3390/ijms21082864] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 03/16/2020] [Accepted: 04/16/2020] [Indexed: 12/12/2022] Open
Abstract
As the worldwide application of nanomaterials in commercial products increases every year, various nanoparticles from industry might present possible risks to aquatic systems and human health. Presently, there are many unknowns about the toxic effects of nanomaterials, especially because the unique physicochemical properties of nanomaterials affect functional and toxic reactions. In our research, we sought to identify the targets and mechanisms for the deleterious effects of two different sizes (~10 and ~50 nm) of amine-modified silver nanoparticles (AgNPs) in a zebrafish embryo model. Fluorescently labeled AgNPs were taken up into embryos via the chorion. The larger-sized AgNPs (LAS) were distributed throughout developing zebrafish tissues to a greater extent than small-sized AgNPs (SAS), which led to an enlarged chorion pore size. Time-course survivorship revealed dose- and particle size-responsive effects, and consequently triggered abnormal phenotypes. LAS exposure led to lysosomal activity changes and higher number of apoptotic cells distributed among the developmental organs of the zebrafish embryo. Overall, AgNPs of ~50 nm in diameter exhibited different behavior from the ~10-nm-diameter AgNPs. The specific toxic effects caused by these differences in nanoscale particle size may result from the different mechanisms, which remain to be further investigated in a follow-up study.
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14
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Irazoqui JE. Key Roles of MiT Transcription Factors in Innate Immunity and Inflammation. Trends Immunol 2020; 41:157-171. [PMID: 31959514 PMCID: PMC6995440 DOI: 10.1016/j.it.2019.12.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2019] [Revised: 11/26/2019] [Accepted: 12/06/2019] [Indexed: 01/07/2023]
Abstract
Microphthalmia/TFE (MiT) transcription factors (TFs), such as transcription factor EB (TFEB) and transcription factor E3 (TFE3), are emerging as key regulators of innate immunity and inflammation. Rapid progress in the field requires a focused update on the latest advances. Recent studies show that TFEB and TFE3 function in innate immune cells to regulate antibacterial and antiviral responses downstream of phagocytosis, interferon (IFN)-γ, lipopolysaccharide (LPS), and adenosine receptors. Moreover, overexpression of TFEB or TFE3 can drive inflammation in vivo, such as in atherosclerosis, while in other scenarios they can perform anti-inflammatory functions. MiT factors may constitute potential therapeutic targets for a broad range of diseases; however, to harness their therapeutic potential, sophisticated ways to manipulate MiT factor activity safely and effectively must be developed.
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Affiliation(s)
- Javier E Irazoqui
- Department of Microbiology and Physiological Systems and Program in Innate Immunity, University of Massachusetts Medical School, Worcester, MA 01605, USA.
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15
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Del Borrello G, Stocchero M, Giordano G, Pirillo P, Zanconato S, Da Dalt L, Carraro S, Esposito S, Baraldi E. New insights into pediatric community-acquired pneumonia gained from untargeted metabolomics: A preliminary study. Pediatr Pulmonol 2020; 55:418-425. [PMID: 31821737 PMCID: PMC7168041 DOI: 10.1002/ppul.24602] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 12/02/2019] [Indexed: 12/27/2022]
Abstract
BACKGROUND Available diagnostics often fail to distinguish viral from bacterial causes of pediatric community-acquired pneumonia (pCAP). Metabolomics, which aims at characterizing diseases based on their metabolic signatures, has been applied to expand pathophysiological understanding of many diseases. In this exploratory study, we used the untargeted metabolomic analysis to shed new light on the etiology of pCAP. METHODS Liquid chromatography coupled with mass spectrometry was used to quantify the metabolite content of urine samples collected from children hospitalized for CAP of pneumococcal or viral etiology, ascertained using a conservative algorithm combining microbiological and biochemical data. RESULTS Fifty-nine children with CAP were enrolled over 16 months. Pneumococcal and viral cases were distinguished by means of a multivariate model based on 93 metabolites, 20 of which were identified and considered as putative biomarkers. Among these, six metabolites belonged to the adrenal steroid synthesis and degradation pathway. CONCLUSIONS This preliminary study suggests that viral and pneumococcal pneumonia differently affect the systemic metabolome, with a stronger disruption of the adrenal steroid pathway in pneumococcal pneumonia. This finding may lead to the discovery of novel diagnostic biomarkers and bring us closer to personalized therapy for pCAP.
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Affiliation(s)
| | - Matteo Stocchero
- Department of Women's and Children's Health, University of Padova, Padova, Italy.,Institute of Pediatric Research (IRP), Fondazione Città della Speranza, Padova, Italy
| | - Giuseppe Giordano
- Department of Women's and Children's Health, University of Padova, Padova, Italy.,Institute of Pediatric Research (IRP), Fondazione Città della Speranza, Padova, Italy
| | - Paola Pirillo
- Department of Women's and Children's Health, University of Padova, Padova, Italy.,Institute of Pediatric Research (IRP), Fondazione Città della Speranza, Padova, Italy
| | - Stefania Zanconato
- Department of Women's and Children's Health, University of Padova, Padova, Italy
| | - Liviana Da Dalt
- Department of Women's and Children's Health, University of Padova, Padova, Italy
| | - Silvia Carraro
- Department of Women's and Children's Health, University of Padova, Padova, Italy
| | - Susanna Esposito
- Department of Surgical and Biomedical Sciences, Pediatric Clinic, University of Perugia, Perugia, Italy
| | - Eugenio Baraldi
- Department of Women's and Children's Health, University of Padova, Padova, Italy.,Institute of Pediatric Research (IRP), Fondazione Città della Speranza, Padova, Italy
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16
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Ben Shlomo S, Mouhadeb O, Cohen K, Varol C, Gluck N. COMMD10-Guided Phagolysosomal Maturation Promotes Clearance of Staphylococcus aureus in Macrophages. iScience 2019; 14:147-163. [PMID: 30959277 PMCID: PMC6453835 DOI: 10.1016/j.isci.2019.03.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 02/28/2019] [Accepted: 03/21/2019] [Indexed: 12/13/2022] Open
Abstract
Staphylococcus aureus is a major cause of infectious disease. Liver Kupffer cells (KCs) are responsible for sequestering and destroying S. aureus through the phagolysosomal pathway. Proteins belonging to the COMMD family emerge as key intracellular regulators of protein trafficking, but the role of COMMD10 in macrophage-mediated S. aureus eradication is unknown. Here we report that COMMD10 in macrophages was necessary for its timely elimination, as demonstrated with two different S. aureus subspecies. In vivo, COMMD10-deficient liver KCs exhibited impaired clearance of systemic S. aureus infection. S. aureus-infected COMMD10-deficient macrophages exhibited impaired activation of the transcription factor EB, resulting in reduced lysosomal biogenesis. Moreover, S. aureus-initiated phagolysosomal maturation and function were significantly attenuated in COMMD10-deficient macrophages. Finally, expression of COMMD/CCDC22/CCDC93 complex, linked to phagolysosomal maturation, was reduced by COMMD10 deficiency. Collectively, these results support an important role for COMMD10 in instructing macrophage phagolysosomal biogenesis and maturation during S. aureus infection.
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Affiliation(s)
- Shani Ben Shlomo
- The Research Center for Digestive Tract and Liver Diseases, Tel-Aviv Sourasky Medical Center and Sackler School of Medicine, Tel-Aviv University, 6 Weizmann St, Tel-Aviv 64239, Israel
| | - Odelia Mouhadeb
- The Research Center for Digestive Tract and Liver Diseases, Tel-Aviv Sourasky Medical Center and Sackler School of Medicine, Tel-Aviv University, 6 Weizmann St, Tel-Aviv 64239, Israel; Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Keren Cohen
- The Research Center for Digestive Tract and Liver Diseases, Tel-Aviv Sourasky Medical Center and Sackler School of Medicine, Tel-Aviv University, 6 Weizmann St, Tel-Aviv 64239, Israel; Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Chen Varol
- The Research Center for Digestive Tract and Liver Diseases, Tel-Aviv Sourasky Medical Center and Sackler School of Medicine, Tel-Aviv University, 6 Weizmann St, Tel-Aviv 64239, Israel; Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel.
| | - Nathan Gluck
- The Research Center for Digestive Tract and Liver Diseases, Tel-Aviv Sourasky Medical Center and Sackler School of Medicine, Tel-Aviv University, 6 Weizmann St, Tel-Aviv 64239, Israel.
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17
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Pérez-Stuardo D, Morales-Reyes J, Tapia S, Ahumada DE, Espinoza A, Soto-Herrera V, Brianson B, Ibaceta V, Sandino AM, Spencer E, Vallejos-Vidal E, Reyes-López FE, Valdés J, Reyes-Cerpa S. Non-lysosomal Activation in Macrophages of Atlantic Salmon ( Salmo salar) After Infection With Piscirickettsia salmonis. Front Immunol 2019; 10:434. [PMID: 30941123 PMCID: PMC6433878 DOI: 10.3389/fimmu.2019.00434] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 02/19/2019] [Indexed: 01/29/2023] Open
Abstract
Piscirickettsia salmonis is a facultative intracellular pathogen and etiological agent of the systemic disease salmonid rickettsial septicemia. It has been suggested that P. salmonis is able to survive in host macrophages, localized within a vacuole like-compartment which prevents lysosomal degradation. However, the relevant aspects of the pathogenesis of P. salmonis as the host modulation that allow its intracellular survival have been poorly characterized. In this study, we evaluated the role of lysosomes in the response to P. salmonis infection in macrophage-enriched cell cultures established from Atlantic salmon head kidneys. Bacterial infection was confirmed using confocal microscopy. A gentamicin protection assay was performed to recover intracellular bacteria and the 16S rDNA copy number was quantified through quantitative polymerase chain reaction in order to determine the replication of P. salmonis within macrophages. Lysosomal activity in Atlantic salmon macrophage-enriched cell cultures infected with P. salmonis was evaluated by analyzing the lysosomal pH and proteolytic ability through confocal microscopy. The results showed that P. salmonis can survive ≥120 h in Atlantic salmon macrophage-enriched cell cultures, accompanied by an increase in the detection of the 16S rDNA copy number/cell. The latter finding suggests that P. salmonis also replicates in Atlantic salmon macrophage-enriched cell cultures. Moreover, this bacterial survival and replication appears to be favored by a perturbation of the lysosomal degradation system. We observed a modulation in the total number of lysosomes and lysosomal acidification following infection with P. salmonis. Collectively, the results of this study showed that infection of Atlantic salmon macrophages with P. salmonis induced limited lysosomal response which may be associated with host immune evasion mechanisms of P. salmonis that have not been previously reported.
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Affiliation(s)
- Diego Pérez-Stuardo
- Centro de Genómica y Bioinformática, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | | | - Sebastián Tapia
- Centro de Genómica y Bioinformática, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Diego E Ahumada
- Centro de Genómica y Bioinformática, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Allison Espinoza
- Centro de Genómica y Bioinformática, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | | | - Bernardo Brianson
- Centro de Genómica y Bioinformática, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Valentina Ibaceta
- Centro de Genómica y Bioinformática, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Ana M Sandino
- Consorcio de Sanidad Acuícola, Ictio Biotechnologies S.A., Santiago, Chile.,Centro de Biotecnología Acuícola, Universidad de Santiago de Chile, Santiago, Chile
| | - Eugenio Spencer
- Consorcio de Sanidad Acuícola, Ictio Biotechnologies S.A., Santiago, Chile.,Centro de Biotecnología Acuícola, Universidad de Santiago de Chile, Santiago, Chile
| | - Eva Vallejos-Vidal
- Department of Cell Biology, Physiology and Immunology, Universitat Autonoma de Barcelona, Barcelona, Spain
| | - Felipe E Reyes-López
- Department of Cell Biology, Physiology and Immunology, Universitat Autonoma de Barcelona, Barcelona, Spain
| | - Jorge Valdés
- Centro de Genómica y Bioinformática, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Sebastián Reyes-Cerpa
- Centro de Genómica y Bioinformática, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
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18
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Rajarathnam K, Schnoor M, Richardson RM, Rajagopal S. How do chemokines navigate neutrophils to the target site: Dissecting the structural mechanisms and signaling pathways. Cell Signal 2019; 54:69-80. [PMID: 30465827 PMCID: PMC6664297 DOI: 10.1016/j.cellsig.2018.11.004] [Citation(s) in RCA: 147] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 11/07/2018] [Accepted: 11/08/2018] [Indexed: 12/12/2022]
Abstract
Chemokines play crucial roles in combating microbial infection and initiating tissue repair by recruiting neutrophils in a timely and coordinated manner. In humans, no less than seven chemokines (CXCL1, CXCL2, CXCL3, CXCL5, CXCL6, CXCL7, and CXCL8) and two receptors (CXCR1 and CXCR2) mediate neutrophil functions but in a context dependent manner. Neutrophil-activating chemokines reversibly exist as monomers and dimers, and their receptor binding triggers conformational changes that are coupled to G-protein and β-arrestin signaling pathways. G-protein signaling activates a variety of effectors including Ca2+ channels and phospholipase C. β-arrestin serves as a multifunctional adaptor and is coupled to several signaling hubs including MAP kinase and tyrosine kinase pathways. Both G-protein and β-arrestin signaling pathways play important non-overlapping roles in neutrophil trafficking and activation. Functional studies have established many similarities but distinct differences for a given chemokine and between chemokines at the level of monomer vs. dimer, CXCR1 vs. CXCR2 activation, and G-protein vs. β-arrestin pathways. We propose that two forms of the ligand binding two receptors and activating two signaling pathways enables fine-tuned neutrophil function compared to a single form, a single receptor, or a single pathway. We summarize the current knowledge on the molecular mechanisms by which chemokine monomers/dimers activate CXCR1/CXCR2 and how these interactions trigger G-protein/β-arrestin-coupled signaling pathways. We also discuss current challenges and knowledge gaps, and likely advances in the near future that will lead to a better understanding of the relationship between the chemokine-CXCR1/CXCR2-G-protein/β-arrestin axis and neutrophil function.
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Affiliation(s)
- Krishna Rajarathnam
- Department of Biochemistry and Molecular Biology, Department of Microbiology and Immunology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, USA.
| | - Michael Schnoor
- Department for Molecular Biomedicine, Cinvestav-IPN, 07360 Mexico City, Mexico
| | - Ricardo M Richardson
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, NC 27707, USA
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19
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Vural A, Nabar NR, Hwang IY, Sohn S, Park C, Karlsson MCI, Blumer JB, Kehrl JH. Gα i2 Signaling Regulates Inflammasome Priming and Cytokine Production by Biasing Macrophage Phenotype Determination. THE JOURNAL OF IMMUNOLOGY 2019; 202:1510-1520. [PMID: 30683698 DOI: 10.4049/jimmunol.1801145] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 12/19/2018] [Indexed: 12/14/2022]
Abstract
Macrophages exist as innate immune subsets that exhibit phenotypic heterogeneity and functional plasticity. Their phenotypes are dictated by inputs from the tissue microenvironment. G-protein-coupled receptors are essential in transducing signals from the microenvironment, and heterotrimeric Gα signaling links these receptors to downstream effectors. Several Gαi-coupled G-protein-coupled receptors have been implicated in macrophage polarization. In this study, we use genetically modified mice to investigate the role of Gαi2 on inflammasome activity and macrophage polarization. We report that Gαi2 in murine bone marrow-derived macrophages (BMDMs) regulates IL-1β release after activation of the NLRP3, AIM2, and NLRC4 inflammasomes. We show this regulation stems from the biased polarity of Gαi2 deficient (Gnai2 -/-) and RGS-insensitive Gαi2 (Gnai2 G184S/G184S) BMDMs. We determined that although Gnai2 G184S/G184S BMDMs (excess Gαi2 signaling) have a tendency toward classically activated proinflammatory (M1) phenotype, Gnai2-/- BMDMs (Gαi2 deficient) are biased toward alternatively activated anti-inflammatory (M2) phenotype. Finally, we find that Gαi2-deficient macrophages have increased Akt activation and IFN-β production but defects in ERK1/2 and STAT3 activation after LPS stimulation. Gαi2-deficient macrophages also exhibit increased STAT6 activation after IL-4 stimulation. In summary, our data indicates that excess Gαi2 signaling promotes an M1 macrophage phenotype, whereas Gαi2 signaling deficiency promotes an M2 phenotype. Understanding Gαi2-mediated effects on macrophage polarization may bring to light insights regarding disease pathogenesis and the reprogramming of macrophages for the development of novel therapeutics.
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Affiliation(s)
- Ali Vural
- B-Cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Neel R Nabar
- B-Cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892; .,Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 171 77 Stockholm, Sweden; and
| | - Il-Young Hwang
- B-Cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Silke Sohn
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 171 77 Stockholm, Sweden; and
| | - Chung Park
- B-Cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Mikael C I Karlsson
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 171 77 Stockholm, Sweden; and
| | - Joe B Blumer
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston, SC 29425
| | - John H Kehrl
- B-Cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892;
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20
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Vural A, Fadillioglu E, Kelesoglu F, Ma D, Lanier SM. Role of G-proteins and phosphorylation in the distribution of AGS3 to cell puncta. J Cell Sci 2018; 131:jcs.216507. [PMID: 30404823 DOI: 10.1242/jcs.216507] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 08/02/2018] [Indexed: 12/20/2022] Open
Abstract
Activator of G-protein signaling 3 (AGS3, also known as GPSM1) exhibits broad functional diversity and oscillates among different subcellular compartments in a regulated manner. AGS3 consists of a tetratricopeptide repeat (TPR) domain and a G-protein regulatory (GPR) domain. Here, we tested the hypothesis that phosphorylation of the AGS3 GPR domain regulates its subcellular distribution and functionality. In contrast to the cortical and/or diffuse non-homogeneous distribution of wild-type (WT) AGS3, an AGS3 construct lacking all 24 potential phosphorylation sites in the GPR domain localized to cytosolic puncta. This change in localization was revealed to be dependent upon phosphorylation of a single threonine amino acid (T602). The punctate distribution of AGS3-T602A was rescued by co-expression of Gαi and Gαo but not Gαs or Gαq Following treatment with alkaline phosphatase, both AGS3-T602A and WT AGS3 exhibited a gel shift in SDS-PAGE as compared to untreated WT AGS3, consistent with a loss of protein phosphorylation. The punctate distribution of AGS3-T602A was lost in an AGS3-A602T conversion mutant, but was still present upon T602 mutation to glutamate or aspartate. These results implicate dynamic phosphorylation as a discrete mechanism to regulate the subcellular distribution of AGS3 and associated functionality.
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Affiliation(s)
- Ali Vural
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Ersin Fadillioglu
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Fatih Kelesoglu
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Dzwokai Ma
- Department of Molecular, Cellular, and Developmental Biology, Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Stephen M Lanier
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201, USA .,Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston, SC 29425, USA
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21
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Liu X, Zhang N, Liu Y, Liu L, Zeng Q, Yin M, Wang Y, Song D, Deng H. MPB, a novel berberine derivative, enhances lysosomal and bactericidal properties via TGF-β-activated kinase 1-dependent activation of the transcription factor EB. FASEB J 2018; 33:1468-1481. [PMID: 30161000 DOI: 10.1096/fj.201801198r] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Lysosome has a crucial role in clearance of endocytosed pathogens from the cell. Small molecules that can boost lysosome function and bactericidal ability to cope with subsequent infection are urgently needed. Here, we report that MPB, a novel berberine derivative, induced lysosome-based degradation and clearance of methicillin-resistant Staphylococcus aureus and enteroinvasive Escherichia coli in macrophages. MPB caused nuclear translocation of transcription factor EB (TFEB), which boosted expression of lysosome genes. TFEB silencing repressed the MPB-mediated enhancements in degradation and bacterial eradication. MPB switched on TFEB nuclear translocation by coupling 2 parallel signaling pathways. MPB-triggered JNK activation led to 14-3-3δ being released from TFEB, which, in turn, caused TFEB nuclear translocation. In addition, MPB induced AMPK activation and subsequent inhibition of mechanistic target of rapamycin activity, which also contributed to TFEB nuclear translocation. Importantly, genetical or pharmaceutical inhibition of TGF-β-activated kinase 1 (TAK1) reduced MPB action remarkably. MPB acted through TAK1 at lysine 158 to activate JNK and AMPK and, thus, induced TFEB-dependent bactericidal activity in macrophages. Therefore, our study reveals a novel mechanism by which MPB controls JNK and AMPK phosphorylation cascades to activate lysosomal function and bactericidal activity via TAK1 K158-dependent manner, which may offer insight into novel therapeutic strategies to control bacterial infection.-Liu, X., Zhang, N., Liu, Y., Liu, L., Zeng, Q., Yin, M., Wang, Y., Song, D., Deng, H. MPB, a novel berberine derivative, enhances lysosomal and bactericidal properties via TGF-β-activated kinase 1-dependent activation of the transcription factor EB.
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Affiliation(s)
- Xiaojia Liu
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Na Zhang
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Yang Liu
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Lu Liu
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Qingxuan Zeng
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Mingxiao Yin
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Yanxiang Wang
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Danqing Song
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Hongbin Deng
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
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22
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Hipolito VEB, Ospina-Escobar E, Botelho RJ. Lysosome remodelling and adaptation during phagocyte activation. Cell Microbiol 2018; 20. [PMID: 29349904 DOI: 10.1111/cmi.12824] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Revised: 01/11/2018] [Accepted: 01/15/2018] [Indexed: 12/30/2022]
Abstract
Lysosomes are acidic and hydrolytic organelles responsible for receiving and digesting cargo acquired during endocytosis, phagocytosis, and autophagy. For macrophages and dendritic cells, the lysosome is kingpin, playing a direct role in microbe killing and antigen processing for presentation. Strikingly, the historic view that lysosomes are homogeneous and static organelles is being replaced with a more elegant paradigm, in which lysosomes are heterogeneous, dynamic, and respond to cellular needs. For example, lysosomes are signalling platforms that integrate stress detection and molecular decision hubs such as the mTOR complex 1 and AMPK to modulate cellular activity. These signals can even adjust lysosome activity by modulating transcription factors such as transcription factor EB (TFEB) and TFE3 that govern lysosome gene expression. Here, we review lysosome remodelling and adaptation during macrophage and dendritic cell stimulation. First, we assess the functional outcomes and regulatory mechanisms driving the dramatic restructuring of lysosomes from globular organelles into a tubular network during phagocyte activation. Second, we discuss lysosome adaptation and scaling in macrophages driven by TFEB and TFE3 stimulation in response to phagocytosis and microbe challenges. Collectively, we are beginning to appreciate that lysosomes are dynamic and adapt to serve phagocyte differentiation in response to microbes and immune stress.
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Affiliation(s)
- Victoria E B Hipolito
- Department of Chemistry and Biology and the Graduate Program in Molecular Science, Ryerson University, Toronto, Ontario, Canada
| | - Erika Ospina-Escobar
- Department of Chemistry and Biology and the Graduate Program in Molecular Science, Ryerson University, Toronto, Ontario, Canada
| | - Roberto J Botelho
- Department of Chemistry and Biology and the Graduate Program in Molecular Science, Ryerson University, Toronto, Ontario, Canada
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Nabar NR, Kehrl JH. The Transcription Factor EB Links Cellular Stress to the Immune Response
. THE YALE JOURNAL OF BIOLOGY AND MEDICINE 2017; 90:301-315. [PMID: 28656016 PMCID: PMC5482306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
The transcription factor EB (TFEB) is the master transcriptional regulator of autophagy and lysosome biogenesis. Recent advances have led to a paradigm shift in our understanding of lysosomes from a housekeeping cellular waste bin to a dynamically regulated pathway that is efficiently turned up or down based on cellular needs. TFEB coordinates the cellular response to nutrient deprivation and other forms of cell stress through the lysosome system, and regulates a myriad of cellular processes associated with this system including endocytosis, phagocytosis, autophagy, and lysosomal exocytosis. Autophagy and the endolysosomal system are critical to both the innate and adaptive arms of the immune system, with functions in effector cell priming and direct pathogen clearance. Recent studies have linked TFEB to the regulation of the immune response through the endolysosmal pathway and by direct transcriptional activation of immune related genes. In this review, we discuss the current understanding of TFEB's function and the molecular mechanisms behind TFEB activation. Finally, we discuss recent advances linking TFEB to the immune response that positions lysosomal signaling as a potential target for immune modulation.
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Affiliation(s)
- Neel R. Nabar
- B cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institutes of Allergy and Infection Disease, National Institutes of Health, Bethesda, MD
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Solna, Sweden
| | - John H. Kehrl
- B cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institutes of Allergy and Infection Disease, National Institutes of Health, Bethesda, MD
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Su BC, Lin WC, Huang HN, Chen JY. Recombinant expression of Epinephelus lanceolatus serum amyloid A (ElSAA) and analysis of its macrophage modulatory activities. FISH & SHELLFISH IMMUNOLOGY 2017; 64:276-286. [PMID: 28323212 DOI: 10.1016/j.fsi.2017.03.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Revised: 03/10/2017] [Accepted: 03/16/2017] [Indexed: 06/06/2023]
Abstract
Serum amyloid A (SAA) is an acute-phase protein that plays a crucial role in the inflammatory response. In this study, we identified an SAA homolog from Epinephelus lanceolatus (ElSAA). Molecular characterization revealed that ElSAA contains a fibronectin-like motif that is typical of SAAs. Recombinant ElSAA protein (rElSAA) was produced in E. coli BL21 (DE3) cells and purified as a soluble protein. To analyze its biological activity, mouse Raw264.7 macrophage cells were treated with various concentrations of rElSAA. Expression of several inflammation-related cytokines, including tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, IL-6, and IL-10, was induced by rElSAA. This protein also triggered macrophage differentiation, as evidenced by increases in cell size and complexity. To determine whether rElSAA regulates macrophage polarization, we assessed gene expression of M1 and M2 markers. The results demonstrated that rElSAA induced the expression of both M1 and M2 markers, suggesting that it promotes the differentiation of macrophages into a mixed M1/M2 phenotype. To evaluate whether rElSAA enhances phagocytosis via an opsonization-dependent mechanism, GFP-labeled E. coli cells were pretreated with rElSAA, followed by incubation with Raw264.7 cells. Flow cytometry was used to monitor the phagocytic uptake of GFP-labeled E. coli by macrophages. Surprisingly, incubating E. coli with rElSAA did not enhance bacterial uptake by macrophages. However, preincubating Raw264.7 cells with various concentrations of rElSAA, followed by infection with E. coli (multiplicity of infection = 20 or 40), resulted in a clear enhancement of macrophage phagocytic capacity. In conclusion, we have identified SAA from E. lanceolatus and have demonstrated that rElSAA promotes inflammatory cytokine production and macrophage differentiation. In addition, rElSAA enhances phagocytosis of bacteria by macrophages via an opsonization-independent mechanism.
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Affiliation(s)
- Bor-Chyuan Su
- Marine Research Station, Institute of Cellular and Organismic Biology, Academia Sinica, 23-10 Dahuen Road, Jiaushi, Ilan 262, Taiwan
| | - Wen-Chun Lin
- Marine Research Station, Institute of Cellular and Organismic Biology, Academia Sinica, 23-10 Dahuen Road, Jiaushi, Ilan 262, Taiwan
| | - Han-Ning Huang
- Marine Research Station, Institute of Cellular and Organismic Biology, Academia Sinica, 23-10 Dahuen Road, Jiaushi, Ilan 262, Taiwan
| | - Jyh-Yih Chen
- Marine Research Station, Institute of Cellular and Organismic Biology, Academia Sinica, 23-10 Dahuen Road, Jiaushi, Ilan 262, Taiwan.
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Robichaux WG, Branham-O'Connor M, Hwang IY, Vural A, Kehrl JH, Blumer JB. Regulation of Chemokine Signal Integration by Activator of G-Protein Signaling 4 (AGS4). J Pharmacol Exp Ther 2017; 360:424-433. [PMID: 28062526 DOI: 10.1124/jpet.116.238436] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2016] [Accepted: 12/28/2016] [Indexed: 12/15/2022] Open
Abstract
Activator of G-protein signaling 4 (AGS4)/G-protein signaling modulator 3 (Gpsm3) contains three G-protein regulatory (GPR) motifs, each of which can bind Gαi-GDP free of Gβγ We previously demonstrated that the AGS4-Gαi interaction is regulated by seven transmembrane-spanning receptors (7-TMR), which may reflect direct coupling of the GPR-Gαi module to the receptor analogous to canonical Gαβγ heterotrimer. We have demonstrated that the AGS4-Gαi complex is regulated by chemokine receptors in an agonist-dependent manner that is receptor-proximal. As an initial approach to investigate the functional role(s) of this regulated interaction in vivo, we analyzed leukocytes, in which AGS4/Gpsm3 is predominantly expressed, from AGS4/Gpsm3-null mice. Loss of AGS4/Gpsm3 resulted in mild but significant neutropenia and leukocytosis. Dendritic cells, T lymphocytes, and neutrophils from AGS4/Gpsm3-null mice also exhibited significant defects in chemoattractant-directed chemotaxis and extracellular signal-regulated kinase activation. An in vivo peritonitis model revealed a dramatic reduction in the ability of AGS4/Gpsm3-null neutrophils to migrate to primary sites of inflammation. Taken together, these data suggest that AGS4/Gpsm3 is required for proper chemokine signal processing in leukocytes and provide further evidence for the importance of the GPR-Gαi module in the regulation of leukocyte function.
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Affiliation(s)
- William G Robichaux
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina (W.G.R., M.B.-O., J.B.B.); and B-Cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland (I.-Y.H., A.V., J.H.K.)
| | - Melissa Branham-O'Connor
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina (W.G.R., M.B.-O., J.B.B.); and B-Cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland (I.-Y.H., A.V., J.H.K.)
| | - Il-Young Hwang
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina (W.G.R., M.B.-O., J.B.B.); and B-Cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland (I.-Y.H., A.V., J.H.K.)
| | - Ali Vural
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina (W.G.R., M.B.-O., J.B.B.); and B-Cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland (I.-Y.H., A.V., J.H.K.)
| | - Johne H Kehrl
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina (W.G.R., M.B.-O., J.B.B.); and B-Cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland (I.-Y.H., A.V., J.H.K.)
| | - Joe B Blumer
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina (W.G.R., M.B.-O., J.B.B.); and B-Cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland (I.-Y.H., A.V., J.H.K.)
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26
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Kehrl JH. The impact of RGS and other G-protein regulatory proteins on Gαi-mediated signaling in immunity. Biochem Pharmacol 2016; 114:40-52. [PMID: 27071343 DOI: 10.1016/j.bcp.2016.04.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 04/08/2016] [Indexed: 01/30/2023]
Abstract
Leukocyte chemoattractant receptors are members of the G-protein coupled receptor (GPCR) family. Signaling downstream of these receptors directs the localization, positioning and homeostatic trafficking of leukocytes; as well as their recruitment to, and their retention at, inflammatory sites. Ligand induced changes in the molecular conformation of chemoattractant receptors results in the engagement of heterotrimeric G-proteins, which promotes α subunits to undergo GTP/GDP exchange. This results in the functional release of βγ subunits from the heterotrimers, thereby activating downstream effector molecules, which initiate leukocyte polarization, gradient sensing, and directional migration. Pertussis toxin ADP ribosylates Gαi subunits and prevents chemoattractant receptors from triggering Gαi nucleotide exchange. The use of pertussis toxin revealed the essential importance of Gαi subunit nucleotide exchange for chemoattractant receptor signaling. More recent studies have identified a range of regulatory mechanisms that target these receptors and their associated heterotrimeric G-proteins, thereby helping to control the magnitude, kinetics, and duration of signaling. A failure in these regulatory pathways can lead to impaired receptor signaling and immunopathology. The analysis of mice with targeted deletions of Gαi isoforms as well as some of these G-protein regulatory proteins is providing insights into their roles in chemoattractant receptor signaling.
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Affiliation(s)
- John H Kehrl
- Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 2089, United States.
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