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Ehrlichia Notch signaling induction promotes XIAP stability and inhibits apoptosis
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 a...
Autores principales: | , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
American Society for Microbiology
2023
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10501217/ https://www.ncbi.nlm.nih.gov/pubmed/37594275 http://dx.doi.org/10.1128/iai.00002-23 |
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author | Patterson, LaNisha L. Byerly, Caitlan D. Solomon, Regina Pittner, Nicholas Bui, Duc Cuong Patel, Jignesh McBride, Jere W. |
author_facet | Patterson, LaNisha L. Byerly, Caitlan D. Solomon, Regina Pittner, Nicholas Bui, Duc Cuong Patel, Jignesh McBride, Jere W. |
author_sort | Patterson, LaNisha L. |
collection | PubMed |
description | 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. |
format | Online Article Text |
id | pubmed-10501217 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2023 |
publisher | American Society for Microbiology |
record_format | MEDLINE/PubMed |
spelling | pubmed-105012172023-09-15 Ehrlichia Notch signaling induction promotes XIAP stability and inhibits apoptosis Patterson, LaNisha L. Byerly, Caitlan D. Solomon, Regina Pittner, Nicholas Bui, Duc Cuong Patel, Jignesh McBride, Jere W. Infect Immun Cellular Microbiology: Pathogen-Host Cell Molecular Interactions 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. American Society for Microbiology 2023-08-18 /pmc/articles/PMC10501217/ /pubmed/37594275 http://dx.doi.org/10.1128/iai.00002-23 Text en Copyright © 2023 Patterson et al. https://creativecommons.org/licenses/by/4.0/This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0/) . |
spellingShingle | Cellular Microbiology: Pathogen-Host Cell Molecular Interactions Patterson, LaNisha L. Byerly, Caitlan D. Solomon, Regina Pittner, Nicholas Bui, Duc Cuong Patel, Jignesh McBride, Jere W. Ehrlichia Notch signaling induction promotes XIAP stability and inhibits apoptosis |
title | Ehrlichia Notch signaling induction promotes XIAP stability and inhibits apoptosis |
title_full | Ehrlichia Notch signaling induction promotes XIAP stability and inhibits apoptosis |
title_fullStr | Ehrlichia Notch signaling induction promotes XIAP stability and inhibits apoptosis |
title_full_unstemmed | Ehrlichia Notch signaling induction promotes XIAP stability and inhibits apoptosis |
title_short | Ehrlichia Notch signaling induction promotes XIAP stability and inhibits apoptosis |
title_sort | ehrlichia notch signaling induction promotes xiap stability and inhibits apoptosis |
topic | Cellular Microbiology: Pathogen-Host Cell Molecular Interactions |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10501217/ https://www.ncbi.nlm.nih.gov/pubmed/37594275 http://dx.doi.org/10.1128/iai.00002-23 |
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