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Li M, Yang N, Li X, Duan N, Qin S, Wang M, Zhou Y, Jin Y, Wu W, Jin S, Cheng Z. Host Cells Upregulate Phosphate Transporter PIT1 to Inhibit Ehrlichia chaffeensis Intracellular Growth. Int J Mol Sci 2024; 25:7895. [PMID: 39063137 PMCID: PMC11276888 DOI: 10.3390/ijms25147895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2024] [Revised: 07/12/2024] [Accepted: 07/15/2024] [Indexed: 07/28/2024] Open
Abstract
Ehrlichia chaffeensis infects and proliferates inside monocytes or macrophages and causes human monocytic ehrlichiosis (HME), an emerging life-threatening tick-borne zoonosis. After internalization, E. chaffeensis resides in specialized membrane-bound inclusions, E. chaffeensis-containing vesicles (ECVs), to evade from host cell innate immune responses and obtain nutrients. However, mechanisms exploited by host cells to inhibit E. chaffeensis growth in ECVs are still largely unknown. Here we demonstrate that host cells recognize E. chaffeensis Ech_1067, a penicillin-binding protein, and then upregulate the expression of PIT1, which is a phosphate transporter and transports phosphate from ECVs to the cytosol to inhibit bacterial growth. We found that host cells upregulate the PIT1 expression upon E. chaffeensis infection using transcriptome sequencing, qRT-PCR and Western blotting, and PIT1 is localized on the ECV membrane in infected THP-1 cells using confocal microscopy. Silence of PIT1 using shRNA enhances E. chaffeensis intracellular growth. Finally, we found that E. chaffeensis Ech_1067 induces the upregulation of PIT1 expression through the MyD88-NF-κB pathway using recombinant protein for stimulation and siRNA for silence. Our findings deepen the understanding of the innate immune responses of host cells to inhibit bacterial intracellular growth and facilitate the development of new therapeutics for HME.
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Affiliation(s)
- Meifang Li
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China; (M.L.); (N.Y.); (X.L.); (N.D.); (S.Q.); (M.W.); (Y.Z.); (Y.J.); (W.W.); (S.J.)
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Nan Yang
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China; (M.L.); (N.Y.); (X.L.); (N.D.); (S.Q.); (M.W.); (Y.Z.); (Y.J.); (W.W.); (S.J.)
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Xiaoxiao Li
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China; (M.L.); (N.Y.); (X.L.); (N.D.); (S.Q.); (M.W.); (Y.Z.); (Y.J.); (W.W.); (S.J.)
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Nan Duan
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China; (M.L.); (N.Y.); (X.L.); (N.D.); (S.Q.); (M.W.); (Y.Z.); (Y.J.); (W.W.); (S.J.)
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Shanhua Qin
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China; (M.L.); (N.Y.); (X.L.); (N.D.); (S.Q.); (M.W.); (Y.Z.); (Y.J.); (W.W.); (S.J.)
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Mengyao Wang
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China; (M.L.); (N.Y.); (X.L.); (N.D.); (S.Q.); (M.W.); (Y.Z.); (Y.J.); (W.W.); (S.J.)
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Yuhong Zhou
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China; (M.L.); (N.Y.); (X.L.); (N.D.); (S.Q.); (M.W.); (Y.Z.); (Y.J.); (W.W.); (S.J.)
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Yongxin Jin
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China; (M.L.); (N.Y.); (X.L.); (N.D.); (S.Q.); (M.W.); (Y.Z.); (Y.J.); (W.W.); (S.J.)
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Weihui Wu
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China; (M.L.); (N.Y.); (X.L.); (N.D.); (S.Q.); (M.W.); (Y.Z.); (Y.J.); (W.W.); (S.J.)
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Shouguang Jin
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China; (M.L.); (N.Y.); (X.L.); (N.D.); (S.Q.); (M.W.); (Y.Z.); (Y.J.); (W.W.); (S.J.)
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Zhihui Cheng
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China; (M.L.); (N.Y.); (X.L.); (N.D.); (S.Q.); (M.W.); (Y.Z.); (Y.J.); (W.W.); (S.J.)
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
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Zhang T, Chien RC, Budachetri K, Lin M, Boyaka P, Huang W, Rikihisa Y. Ehrlichia effector TRP120 manipulates bacteremia to facilitate tick acquisition. mBio 2024; 15:e0047624. [PMID: 38501870 PMCID: PMC11005420 DOI: 10.1128/mbio.00476-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Accepted: 03/03/2024] [Indexed: 03/20/2024] Open
Abstract
Ehrlichia species are obligatory intracellular bacteria that cause a potentially fatal disease, human ehrlichiosis. The biomolecular mechanisms of tick acquisition of Ehrlichia and transmission between ticks and mammals are poorly understood. Ehrlichia japonica infection of mice recapitulates the full spectrum of human ehrlichiosis. We compared the pathogenicity and host acquisition of wild-type E. japonica with an isogenic transposon mutant of E. japonica that lacks tandem repeat protein 120 (TRP120) (ΔTRP120). Both wild-type and ΔTRP120 E. japonica proliferated similarly in cultures of mammalian and tick cells. Upon inoculation into mice, both wild-type and ΔTRP120 E. japonica multiplied to high levels in various tissues, with similar clinical chemistry and hematologic changes, proinflammatory cytokine induction, and fatal disease. However, the blood levels of ΔTRP120 E. japonica were almost undetectable within 24 h, whereas the levels of the wild type increased exponentially. Greater than 90% of TRP120 was released from infected cells into the culture medium. Mouse blood monocytes exposed to native TRP120 from culture supernatants showed significantly reduced cell surface expression of the transmigration-related markers Ly6C and CD11b. Larval ticks attached to mice infected with either wild-type or ΔTRP120 E. japonica imbibed similar amounts of blood and subsequently molted to nymphs at similar rates. However, unlike wild-type E. japonica, the ΔTRP120 mutant was minimally acquired by larval ticks and subsequent molted nymphs and, thus, failed to transmit to naïve mice. Thus, TRP120 is required for bacteremia but not disease. These findings suggest a novel mechanism whereby an obligatory intracellular bacterium manipulates infected blood monocytes to sustain the tick-mammal transmission cycle. IMPORTANCE Effective prevention of tick-borne diseases such as human ehrlichiosis requires an understanding of how disease-causing organisms are acquired. Ehrlichia species are intracellular bacteria that require infection of both mammals and ticks, involving cycles of transmission between them. Mouse models of ehrlichiosis and tick-mouse transmission can advance our fundamental understanding of the pathogenesis and prevention of ehrlichiosis. Herein, a mutant of Ehrlichia japonica was used to investigate the role of a single Ehrlichia factor, named tandem repeat protein 120 (TRP120), in infection of mammalian and tick cells in culture, infection and disease progression in mice, and tick acquisition of E. japonica from infected mice. Our results suggest that TRP120 is necessary only for Ehrlichia proliferation in circulating mouse blood and ongoing bacteremia to permit Ehrlichia acquisition by ticks. This study provides new insights into the importance of bacterial factors in regulating bacteremia, which may facilitate tick acquisition of pathogens.
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Affiliation(s)
- Tsian Zhang
- Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio, USA
| | - Rory C. Chien
- Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio, USA
| | - Khemraj Budachetri
- Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio, USA
| | - Mingqun Lin
- Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio, USA
| | - Prosper Boyaka
- Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio, USA
| | - Weiyan Huang
- Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio, USA
| | - Yasuko Rikihisa
- Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio, USA
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Byerly CD, Zhu B, Warwick PA, Patterson LL, Pittner NA, McBride JW. Ehrlichia chaffeensis TRP120 ubiquitinates tumor suppressor APC to modulate Hippo and Wnt signaling. Front Cell Dev Biol 2024; 12:1327418. [PMID: 38562145 PMCID: PMC10982408 DOI: 10.3389/fcell.2024.1327418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 03/05/2024] [Indexed: 04/04/2024] Open
Abstract
Ehrlichia chaffeensis: TRP120 is a multifunctional effector that acts as a ligand mimic to activate evolutionary conserved eukaryotic signaling pathways Notch, Wnt, Hedgehog and Hippo. In addition, TRP120 is also a HECT E3 ubiquitin ligase known to ubiquitinate several host cell regulatory proteins (FBW7, PCGF5 and ENO-1) for degradation. We previously determined that TRP120 ubiquitinates the Notch negative regulator, FBW7, to maintain Notch signaling and promote infection. In this study, we investigated a potential mechanism used by Ehrlichia chaffeensis to maintain Hippo and Wnt signaling by ubiquitinating the tumor suppressor, adenomatous polyposis coli (APC), a negative regulator of Wnt and Hippo signaling. We determined that APC was rapidly degraded during E. chaffeensis infection despite increased APC transcription. Moreover, RNAi knockdown of APC significantly increased E. chaffeensis infection and coincided with increased active Yap and β-catenin in the nucleus. We observed strong nuclear colocalization between TRP120 and APC in E. chaffeensis-infected THP-1 cells and after ectopic expression of TRP120 in HeLa cells. Additionally, TRP120 interacted with both APC full length and truncated isoforms via co-immunoprecipitation. Further, TRP120 ubiquitination of APC was demonstrated in vitro and confirmed by ectopic expression of a TRP120 HECT Ub ligase catalytic site mutant. This study identifies APC as a TRP120 HECT E3 Ub ligase substrate and demonstrates that TRP120 ligase activity promotes ehrlichial infection by degrading tumor suppressor APC to positively regulate Hippo and Wnt signaling.
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Affiliation(s)
| | | | | | | | | | - Jere W. McBride
- Departments of Pathology, Microbiology and Immunology, Center for Biodefense and Emerging Infectious Diseases, Sealy Institute for Vaccine Sciences and Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX, United States
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Byerly CD, Patterson LL, Pittner NA, Solomon RN, Patel JG, Rogan MR, McBride JW. Ehrlichia Wnt SLiM ligand mimic deactivates the Hippo pathway to engage the anti-apoptotic Yap-GLUT1-BCL-xL axis. Infect Immun 2023; 91:e0008523. [PMID: 37530530 PMCID: PMC10501218 DOI: 10.1128/iai.00085-23] [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: 03/02/2023] [Accepted: 06/03/2023] [Indexed: 08/03/2023] Open
Abstract
Ehrlichia chaffeensis TRP120 effector has evolved short linear motif (SLiM) ligand mimicry to repurpose multiple evolutionarily conserved cellular signaling pathways, including Wnt, Notch, and Hedgehog. In this investigation, we demonstrate that E. chaffeensis and recombinant TRP120 deactivate Hippo signaling, resulting in the activation of Hippo transcription coactivator Yes-associated protein (Yap). Moreover, a homologous 6 amino acid (QDVASH) SLiM shared by TRP120 and Wnt3a/5a ligands phenocopied Yap and β-catenin activation induced by E. chaffeensis, rTRP120, and Wnt5a. Similar Hippo gene expression profiles were also stimulated by E. chaffeensis, rTRP120, SLiM, and Wnt5a. Single siRNA knockdown of Hippo transcription co-activator/factors, Yap, and transcriptional enhanced associate domain (TEAD) significantly decreased E. chaffeensis infection. Yap activation was abolished in THP-1 Wnt Frizzled-5 (Fzd5) receptor knockout cells (KO), demonstrating Fzd5 receptor dependence. In addition, the TRP120-Wnt-SLiM antibody blocked Hippo deactivation (Yap activation). Expression of anti-apoptotic Hippo target gene SLC2A1 (encodes glucose transporter 1; GLUT1) was upregulated by E. chaffeensis and corresponded to increased levels of GLUT1. Conversely, siRNA knockdown of SLC2A1 significantly inhibited infection. Higher GLUT1 levels correlated with increased B cell lymphoma-extra large (BCL-xL) and decreased BCL2-associated X, apoptosis regulator (Bax) levels. Moreover, blocking Yap activation with the inhibitor Verteporfin induced apoptosis that corresponded to significant reductions in GLUT1 and BCL-xL levels and activation of Bax and Caspase-3 and -9. This study identifies a novel shared Wnt/Hippo SLiM ligand mimic and demonstrates that E. chaffeensis deactivates the Hippo pathway to engage the anti-apoptotic Yap-GLUT1-BCL-xL axis.
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Affiliation(s)
- Caitlan D. Byerly
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - LaNisha L. Patterson
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Nicholas A. Pittner
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Regina N. Solomon
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Jignesh G. Patel
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Madison R. Rogan
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Jere W. McBride
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, USA
- Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, USA
- Sealy Institute for Vaccine Sciences, University of Texas Medical Branch, Galveston, Texas, USA
- Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas, USA
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Patterson LL, Byerly CD, Solomon R, Pittner N, Bui DC, Patel J, McBride JW. Ehrlichia Notch signaling induction promotes XIAP stability and inhibits apoptosis. Infect Immun 2023; 91:e0000223. [PMID: 37594275 PMCID: PMC10501217 DOI: 10.1128/iai.00002-23] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Accepted: 06/07/2023] [Indexed: 08/19/2023] Open
Abstract
Ehrlichia chaffeensis has evolved multiple strategies to evade innate defenses of the mononuclear phagocyte. Recently, we reported the E. chaffeensis tandem repeat protein (TRP)120 effector functions as a Notch ligand mimetic and a ubiquitin ligase that degrades the nuclear tumor suppressor, F-box and WD repeat domain-containing 7, a negative regulator of Notch. The Notch intracellular domain (NICD) is known to inhibit apoptosis primarily by interacting with X-linked inhibitor of apoptosis protein (XIAP) to prevent degradation. In this study, we determined that E. chaffeensis activation of Notch signaling increases XIAP levels, thereby inhibiting apoptosis through both the intrinsic and executioner pathways. Increased NICD and XIAP levels were detected during E. chaffeensis infection and after TRP120 Notch ligand mimetic peptide treatment. Conversely, XIAP levels were reduced in the presence of Notch inhibitor DAPT. Cytoplasmic and nuclear colocalization of NICD and XIAP was observed during infection and a direct interaction was confirmed by co-immunoprecipitation. Procaspase levels increased temporally during infection, consistent with increased XIAP levels; however, knockdown (KD) of XIAP during infection significantly increased apoptosis and Caspase-3, -7, and -9 levels. Furthermore, treatment with SM-164, a second mitochondrial activator of caspases (Smac/DIABLO) antagonist, resulted in decreased procaspase levels and increased caspase activation, induced apoptosis, and significantly decreased infection. In addition, RNAi KD of XIAP also decreased infection and significantly increased apoptosis. Moreover, ectopic expression of TRP120 HECT Ub ligase catalytically defective mutant in HeLa cells decreased NICD and XIAP levels and increased caspase activation compared to HeLa cells with functional HECT Ub ligase catalytic activity (TRP120-WT). This investigation reveals a mechanism whereby E. chaffeensis modulates Notch signaling to stabilize XIAP and inhibit apoptosis.
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Affiliation(s)
- LaNisha L. Patterson
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Caitlan D. Byerly
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Regina Solomon
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Nicholas Pittner
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Duc Cuong Bui
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Jignesh Patel
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Jere W. McBride
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, USA
- Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, USA
- Sealy Institute for Vaccine Sciences, University of Texas Medical Branch, Galveston, Texas, USA
- Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas, USA
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Bui DC, Luo T, McBride JW. Type 1 secretion system and effectors in Rickettsiales. Front Cell Infect Microbiol 2023; 13:1175688. [PMID: 37256108 PMCID: PMC10225607 DOI: 10.3389/fcimb.2023.1175688] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 05/02/2023] [Indexed: 06/01/2023] Open
Abstract
Obligate intracellular bacteria in the order Rickettsiales are transmitted by arthropod vectors and cause life-threatening infections in humans and animals. While both type 1 and type 4 secretion systems (T1SS and T4SS) have been identified in this group, the most extensive studies of Rickettsiales T1SS and associated effectors have been performed in Ehrlichia. These studies have uncovered important roles for the T1SS effectors in pathobiology and immunity. To evade innate immune responses and promote intracellular survival, Ehrlichia and other related obligate pathogens secrete multiple T1SS effectors which interact with a diverse network of host targets associated with essential cellular processes. T1SS effectors have multiple functional activities during infection including acting as nucleomodulins and ligand mimetics that activate evolutionarily conserved cellular signaling pathways. In Ehrlichia, an array of newly defined major immunoreactive proteins have been identified that are predicted as T1SS substrates and have conformation-dependent antibody epitopes. These findings highlight the underappreciated and largely uncharacterized roles of T1SS effector proteins in pathobiology and immunity. This review summarizes current knowledge regarding roles of T1SS effectors in Rickettsiales members during infection and explores newly identified immunoreactive proteins as potential T1SS substrates and targets of a protective host immune response.
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Affiliation(s)
- Duc-Cuong Bui
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, United States
| | - Tian Luo
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, United States
| | - Jere W. McBride
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, United States
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, United States
- Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, TX, United States
- Sealy Institute for Vaccine Sciences, University of Texas Medical Branch, Galveston, TX, United States
- Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX, United States
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Gillespie JJ, Salje J. Orientia and Rickettsia: different flowers from the same garden. Curr Opin Microbiol 2023; 74:102318. [PMID: 37080115 DOI: 10.1016/j.mib.2023.102318] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 03/17/2023] [Accepted: 03/20/2023] [Indexed: 04/22/2023]
Abstract
Recent discoveries of basal extracellular Rickettsiales have illuminated divergent evolutionary paths to host dependency in later-evolving lineages. Family Rickettsiaceae, primarily comprised of numerous protist- and invertebrate-associated species, also includes human pathogens from two genera, Orientia and Rickettsia. Once considered sister taxa, these bacteria form distinct lineages with newly appreciated lifestyles and morphological traits. Contrasting other rickettsial human pathogens in Family Anaplasmataceae, Orientia and Rickettsia species do not reside in host-derived vacuoles and lack glycolytic potential. With only a few described mechanisms, strategies for commandeering host glycolysis to support cytosolic growth remain to be discovered. While regulatory systems for this unique mode of intracellular parasitism are unclear, conjugative transposons unique to Orientia and Rickettsia species provide insights that are critical for determining how these obligate intracellular pathogens overtake eukaryotic cytosol.
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Affiliation(s)
- Joseph J Gillespie
- Department of Microbiology and Immunology, School of Medicine, University of Maryland Baltimore, USA.
| | - Jeanne Salje
- Department of Biochemistry, Department of Pathology, and Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK.
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Pittner NA, Solomon RN, Bui DC, McBride JW. Ehrlichia effector SLiM-icry: Artifice of cellular subversion. Front Cell Infect Microbiol 2023; 13:1150758. [PMID: 36960039 PMCID: PMC10028187 DOI: 10.3389/fcimb.2023.1150758] [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: 01/24/2023] [Accepted: 02/23/2023] [Indexed: 03/09/2023] Open
Abstract
As an obligately intracellular bacterial pathogen that selectively infects the mononuclear phagocyte, Ehrlichia chaffeensis has evolved sophisticated mechanisms to subvert innate immune defenses. While the bacterium accomplishes this through a variety of mechanisms, a rapidly expanding body of evidence has revealed that E. chaffeensis has evolved survival strategies that are directed by the versatile, intrinsically disordered, 120 kDa tandem repeat protein (TRP120) effector. E. chaffeensis establishes infection by manipulating multiple evolutionarily conserved cellular signaling pathways through effector-host interactions to subvert innate immune defenses. TRP120 activates these pathways using multiple functionally distinct, repetitive, eukaryote-mimicking short linear motifs (SLiMs) located within the tandem repeat domain that have evolved in nihilo. Functionally, the best characterized TRP120 SLiMs mimic eukaryotic ligands (SLiM-icry) to engage pathway-specific host receptors and activate cellular signaling, thereby repurposing these pathways to promote infection. Moreover, E. chaffeensis TRP120 contains SLiMs that are targets of post-translational modifications such as SUMOylation in addition to many other validated SLiMs that are curated in the eukaryotic linear motif (ELM) database. This review will explore the extracellular and intracellular roles TRP120 SLiM-icry plays during infection - mediated through a variety of SLiMs - that enable E. chaffeensis to subvert mononuclear phagocyte innate defenses.
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Affiliation(s)
- Nicholas A. Pittner
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, United States
| | - Regina N. Solomon
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, United States
| | - Duc-Cuong Bui
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, United States
| | - Jere W. McBride
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, United States
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, United States
- Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, TX, United States
- Sealy Institute for Vaccine Sciences, University of Texas Medical Branch, Galveston, TX, United States
- Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX, United States
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Mavri M, Glišić S, Senćanski M, Vrecl M, Rosenkilde MM, Spiess K, Kubale V. Patterns of human and porcine gammaherpesvirus-encoded BILF1 receptor endocytosis. Cell Mol Biol Lett 2023; 28:14. [PMID: 36810008 PMCID: PMC9942385 DOI: 10.1186/s11658-023-00427-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 01/30/2023] [Indexed: 02/23/2023] Open
Abstract
BACKGROUND The viral G-protein-coupled receptor (vGPCR) BILF1 encoded by the Epstein-Barr virus (EBV) is an oncogene and immunoevasin and can downregulate MHC-I molecules at the surface of infected cells. MHC-I downregulation, which presumably occurs through co-internalization with EBV-BILF1, is preserved among BILF1 receptors, including the three BILF1 orthologs encoded by porcine lymphotropic herpesviruses (PLHV BILFs). This study aimed to understand the detailed mechanisms of BILF1 receptor constitutive internalization, to explore the translational potential of PLHV BILFs compared with EBV-BILF1. METHODS A novel real-time fluorescence resonance energy transfer (FRET)-based internalization assay combined with dominant-negative variants of dynamin-1 (Dyn K44A) and the chemical clathrin inhibitor Pitstop2 in HEK-293A cells was used to study the effect of specific endocytic proteins on BILF1 internalization. Bioluminescence resonance energy transfer (BRET)-saturation analysis was used to study BILF1 receptor interaction with β-arrestin2 and Rab7. In addition, a bioinformatics approach informational spectrum method (ISM) was used to investigate the interaction affinity of BILF1 receptors with β-arrestin2, AP-2, and caveolin-1. RESULTS We identified dynamin-dependent, clathrin-mediated constitutive endocytosis for all BILF1 receptors. The observed interaction affinity between BILF1 receptors and caveolin-1 and the decreased internalization in the presence of a dominant-negative variant of caveolin-1 (Cav S80E) indicated the involvement of caveolin-1 in BILF1 trafficking. Furthermore, after BILF1 internalization from the plasma membrane, both the recycling and degradation pathways are proposed for BILF1 receptors. CONCLUSIONS The similarity in the internalization mechanisms observed for EBV-BILF1 and PLHV1-2 BILF1 provide a foundation for further studies exploring a possible translational potential for PLHVs, as proposed previously, and provides new information about receptor trafficking.
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Affiliation(s)
- Maša Mavri
- Institute for preclinical sciences, Veterinary Faculty, Ljubljana, Slovenia
| | - Sanja Glišić
- Center for Multidisciplinary Research, Institute of Nuclear Sciences VINCA, University of Belgrade, Belgrade, Serbia
| | - Milan Senćanski
- Center for Multidisciplinary Research, Institute of Nuclear Sciences VINCA, University of Belgrade, Belgrade, Serbia
| | - Milka Vrecl
- Institute for preclinical sciences, Veterinary Faculty, Ljubljana, Slovenia
| | - Mette M Rosenkilde
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Katja Spiess
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Virus and Microbiological Special Diagnostics, Statens Serum Institute, Copenhagen, Denmark
| | - Valentina Kubale
- Institute for preclinical sciences, Veterinary Faculty, Ljubljana, Slovenia.
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Patterson LL, Byerly CD, Solomon R, Pittner N, Bui DC, Patel J, McBride JW. Ehrlichia Notch signaling induction promotes XIAP stability and inhibits apoptosis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.06.523066. [PMID: 36711597 PMCID: PMC9881962 DOI: 10.1101/2023.01.06.523066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Ehrlichia chaffeensis has evolved multiple strategies to evade innate defenses of the mononuclear phagocyte. Recently, we reported the E. chaffeensis TRP120 effector functions as a Notch ligand mimetic and a ubiquitin ligase that degrades the nuclear tumor suppressor, F-box and WD repeat domain-containing 7 (FBW7), a negative regulator of Notch. The Notch receptor intracellular domain (NICD) is known to inhibit apoptosis primarily by interacting with X-linked inhibitor of apoptosis protein (XIAP) to prevent degradation. In this study, we determined E. chaffeensis activation of Notch signaling increases XIAP levels, thereby inhibiting intrinsic apoptosis. Increased NICD and XIAP levels were detected during E. chaffeensis infection and after TRP120 Notch ligand mimetic peptide treatment. Conversely, XIAP levels were reduced in the presence of Notch inhibitor DAPT. Cytoplasmic colocalization of NICD and XIAP was observed during infection and a direct interaction was confirmed by co-immunoprecipitation. Procaspase levels increased temporally during infection, consistent with increased XIAP levels; however, knockdown of XIAP during infection significantly increased apoptosis and Caspase-3, -7 and -9 levels. Further, treatment with SM-164, a second mitochondrial activator of caspases (Smac/DIABLO) antagonist, resulted in decreased procaspase levels and increased caspase activation, induced apoptosis, and significantly decreased infection. In addition, iRNA knockdown of XIAP also decreased infection and significantly increased apoptosis. Moreover, ectopic expression of TRP120 HECT Ub ligase catalytically defective mutant in HeLa cells decreased NICD and XIAP levels and increased caspase activation compared to WT. This investigation reveals a mechanism whereby E. chaffeensis repurposes Notch signaling to stabilize XIAP and inhibit apoptosis. Author Summary Ehrlichia chaffeensis is a tick-borne, obligately intracellular bacterium that exhibits tropism for mononuclear phagocytes. E. chaffeensis survives by mobilizing various molecular strategies to promote cell survival, including modulation of apoptosis. This investigation reveals an E. chaffeensis initiated, Notch signaling regulated, antiapoptotic mechanism involving inhibitor of apoptosis proteins (IAPs). Herein, we demonstrate that E. chaffeensis induced Notch activation results in Notch intracellular domain stabilization of X-linked inhibitor of apoptosis protein (XIAP) to inhibit intrinsic apoptosis. This study highlights a novel mechanistic strategy whereby intracellular pathogens repurpose evolutionarily conserved eukaryotic signaling pathways to engage an antiapoptotic program for intracellular survival.
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Byerly CD, Mitra S, Patterson LL, Pittner NA, Velayutham TS, Paessler S, Veljkovic V, McBride JW. Ehrlichia SLiM ligand mimetic activates Hedgehog signaling to engage a BCL-2 anti-apoptotic cellular program. PLoS Pathog 2022; 18:e1010345. [PMID: 35576232 PMCID: PMC9135340 DOI: 10.1371/journal.ppat.1010345] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 05/26/2022] [Accepted: 04/21/2022] [Indexed: 11/19/2022] Open
Abstract
Ehrlichia chaffeensis (E. chaffeensis) has evolved eukaryotic ligand mimicry to repurpose multiple cellular signaling pathways for immune evasion. In this investigation, we demonstrate that TRP120 has a novel repetitive short linear motif (SLiM) that activates the evolutionarily conserved Hedgehog (Hh) signaling pathway to inhibit apoptosis. In silico analysis revealed that TRP120 has sequence and functional similarity with Hh ligands and a candidate Hh ligand SLiM was identified. siRNA knockdown of Hh signaling and transcriptional components significantly reduced infection. Co-immunoprecipitation and surface plasmon resonance demonstrated that rTRP120-TR interacted directly with Hh receptor Patched-2 (PTCH2). E. chaffeensis infection resulted in early upregulation of Hh transcription factor GLI-1 and regulation of Hh target genes. Moreover, soluble recombinant TRP120 (rTRP120) activated Hh and induced gene expression consistent with the eukaryotic Hh ligand. The TRP120-Hh-SLiM (NPEVLIKD) induced nuclear translocation of GLI-1 in THP-1 cells and primary human monocytes and induced a rapid and expansive activation of Hh pathway target genes. Furthermore, Hh activation was blocked by an α-TRP120-Hh-SLiM antibody. TRP120-Hh-SLiM significantly increased levels of Hh target, anti-apoptotic protein B-cell lymphoma 2 (BCL-2), and siRNA knockdown of BCL-2 dramatically inhibited infection. Blocking Hh signaling with the inhibitor Vismodegib, induced a pro-apoptotic cellular program defined by decreased mitochondria membrane potential, significant reductions in BCL-2, activation of caspase 3 and 9, and increased apoptotic cells. This study reveals a novel E. chaffeensis SLiM ligand mimetic that activates Hh signaling to maintain E. chaffeensis infection by engaging a BCL-2 anti-apoptotic cellular program.
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Affiliation(s)
- Caitlan D. Byerly
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Shubhajit Mitra
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - LaNisha L. Patterson
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Nicholas A. Pittner
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Thangam S. Velayutham
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Slobodan Paessler
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Biomed Protection, LLC, Galveston, Texas, United States of America
| | - Veljko Veljkovic
- Biomed Protection, LLC, Galveston, Texas, United States of America
| | - Jere W. McBride
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, United States of America
- Sealy Institute for Vaccine Sciences, University of Texas Medical Branch, Galveston, Texas, United States of America
- Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas, United States of America
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