Distinct Roles of the Repeat-Containing Regions and Effector Domains of the <named-content content-type="genus-species">Vibrio vulnificus</named-content> Multifunctional-Autoprocessing Repeats-in-Toxin (MARTX) Toxin

ABSTRACT Vibrio vulnificus is a seafood-borne pathogen that destroys the intestinal epithelium, leading to rapid bacterial dissemination and death. The most important virulence factor is the multifunctional-autoprocessing repeats-in-toxin (MARTX) toxin comprised of effector domains in the center reg...

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Autores principales:	Byoung Sik Kim, Hannah E. Gavin, Karla J. F. Satchell
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2015
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/b0194175457c4f9286923634349e15b7
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spelling	oai:doaj.org-article:b0194175457c4f9286923634349e15b72021-11-15T15:41:33ZDistinct Roles of the Repeat-Containing Regions and Effector Domains of the <named-content content-type="genus-species">Vibrio vulnificus</named-content> Multifunctional-Autoprocessing Repeats-in-Toxin (MARTX) Toxin10.1128/mBio.00324-152150-7511https://doaj.org/article/b0194175457c4f9286923634349e15b72015-05-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00324-15https://doaj.org/toc/2150-7511ABSTRACT Vibrio vulnificus is a seafood-borne pathogen that destroys the intestinal epithelium, leading to rapid bacterial dissemination and death. The most important virulence factor is the multifunctional-autoprocessing repeats-in-toxin (MARTX) toxin comprised of effector domains in the center region flanked by long repeat-containing regions which are well conserved among MARTX toxins and predicted to translocate effector domains. Here, we examined the role of the repeat-containing regions using a modified V. vulnificus MARTX (MARTXVv) toxin generated by replacing all the internal effector domains with β-lactamase (Bla). Bla activity was detected in secretions from the bacterium and also in the cytosol of intoxicated epithelial cells. The modified MARTXVv toxin without effector domains retained its necrotic activity but lost its cell-rounding activity. Further, deletion of the carboxyl-terminal repeat-containing region blocked toxin secretion from the bacterium. Deletion of the amino-terminal repeat-containing region had no effect on secretion but completely abolished translocation and necrosis. Neither secretion nor translocation was affected by enzymatically inactivating the cysteine protease domain of the toxin. These data demonstrate that the amino-terminal and carboxyl-terminal repeat-containing regions of the MARTXVv toxin are necessary and sufficient for the delivery of effector domains and epithelial cell lysis in vitro but that effector domains are required for other cytopathic functions. Furthermore, Ca2+-dependent secretion of the modified MARTXVv toxin suggests that nonclassical RTX-like repeats found in the carboxyl-terminal repeat-containing region are functionally similar to classical RTX repeats found in other RTX proteins. IMPORTANCE Up to 95% of deaths from seafood-borne infections in the United States are due solely to one pathogen, V. vulnificus. Among its various virulence factors, the MARTXVv toxin has been characterized as a critical exotoxin for successful pathogenesis of V. vulnificus in mouse infection models. Similarly to MARTX toxins of other pathogens, MARTXVv toxin is comprised of repeat-containing regions, central effector domains, and an autoprocessing cysteine protease domain. Yet how each of these regions contributes to essential activities of the toxins has not been fully identified for any of MARTX toxins. Using modified MARTXVv toxin fused with β-lactamase as a reporter enzyme, the portion(s) responsible for toxin secretion from bacteria, effector domain translocation into host cells, rapid host cell rounding, and necrotic host cell death was identified. The results are relevant for understanding how MARTXVv toxin serves as both a necrotic pore-forming toxin and an effector delivery platform.Byoung Sik KimHannah E. GavinKarla J. F. SatchellAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 6, Iss 2 (2015)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Byoung Sik Kim Hannah E. Gavin Karla J. F. Satchell Distinct Roles of the Repeat-Containing Regions and Effector Domains of the <named-content content-type="genus-species">Vibrio vulnificus</named-content> Multifunctional-Autoprocessing Repeats-in-Toxin (MARTX) Toxin
description	ABSTRACT Vibrio vulnificus is a seafood-borne pathogen that destroys the intestinal epithelium, leading to rapid bacterial dissemination and death. The most important virulence factor is the multifunctional-autoprocessing repeats-in-toxin (MARTX) toxin comprised of effector domains in the center region flanked by long repeat-containing regions which are well conserved among MARTX toxins and predicted to translocate effector domains. Here, we examined the role of the repeat-containing regions using a modified V. vulnificus MARTX (MARTXVv) toxin generated by replacing all the internal effector domains with β-lactamase (Bla). Bla activity was detected in secretions from the bacterium and also in the cytosol of intoxicated epithelial cells. The modified MARTXVv toxin without effector domains retained its necrotic activity but lost its cell-rounding activity. Further, deletion of the carboxyl-terminal repeat-containing region blocked toxin secretion from the bacterium. Deletion of the amino-terminal repeat-containing region had no effect on secretion but completely abolished translocation and necrosis. Neither secretion nor translocation was affected by enzymatically inactivating the cysteine protease domain of the toxin. These data demonstrate that the amino-terminal and carboxyl-terminal repeat-containing regions of the MARTXVv toxin are necessary and sufficient for the delivery of effector domains and epithelial cell lysis in vitro but that effector domains are required for other cytopathic functions. Furthermore, Ca2+-dependent secretion of the modified MARTXVv toxin suggests that nonclassical RTX-like repeats found in the carboxyl-terminal repeat-containing region are functionally similar to classical RTX repeats found in other RTX proteins. IMPORTANCE Up to 95% of deaths from seafood-borne infections in the United States are due solely to one pathogen, V. vulnificus. Among its various virulence factors, the MARTXVv toxin has been characterized as a critical exotoxin for successful pathogenesis of V. vulnificus in mouse infection models. Similarly to MARTX toxins of other pathogens, MARTXVv toxin is comprised of repeat-containing regions, central effector domains, and an autoprocessing cysteine protease domain. Yet how each of these regions contributes to essential activities of the toxins has not been fully identified for any of MARTX toxins. Using modified MARTXVv toxin fused with β-lactamase as a reporter enzyme, the portion(s) responsible for toxin secretion from bacteria, effector domain translocation into host cells, rapid host cell rounding, and necrotic host cell death was identified. The results are relevant for understanding how MARTXVv toxin serves as both a necrotic pore-forming toxin and an effector delivery platform.
format	article
author	Byoung Sik Kim Hannah E. Gavin Karla J. F. Satchell
author_facet	Byoung Sik Kim Hannah E. Gavin Karla J. F. Satchell
author_sort	Byoung Sik Kim
title	Distinct Roles of the Repeat-Containing Regions and Effector Domains of the <named-content content-type="genus-species">Vibrio vulnificus</named-content> Multifunctional-Autoprocessing Repeats-in-Toxin (MARTX) Toxin
title_short	Distinct Roles of the Repeat-Containing Regions and Effector Domains of the <named-content content-type="genus-species">Vibrio vulnificus</named-content> Multifunctional-Autoprocessing Repeats-in-Toxin (MARTX) Toxin
title_full	Distinct Roles of the Repeat-Containing Regions and Effector Domains of the <named-content content-type="genus-species">Vibrio vulnificus</named-content> Multifunctional-Autoprocessing Repeats-in-Toxin (MARTX) Toxin
title_fullStr	Distinct Roles of the Repeat-Containing Regions and Effector Domains of the <named-content content-type="genus-species">Vibrio vulnificus</named-content> Multifunctional-Autoprocessing Repeats-in-Toxin (MARTX) Toxin
title_full_unstemmed	Distinct Roles of the Repeat-Containing Regions and Effector Domains of the <named-content content-type="genus-species">Vibrio vulnificus</named-content> Multifunctional-Autoprocessing Repeats-in-Toxin (MARTX) Toxin
title_sort	distinct roles of the repeat-containing regions and effector domains of the <named-content content-type="genus-species">vibrio vulnificus</named-content> multifunctional-autoprocessing repeats-in-toxin (martx) toxin
publisher	American Society for Microbiology
publishDate	2015
url	https://doaj.org/article/b0194175457c4f9286923634349e15b7
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Distinct Roles of the Repeat-Containing Regions and Effector Domains of the <named-content content-type="genus-species">Vibrio vulnificus</named-content> Multifunctional-Autoprocessing Repeats-in-Toxin (MARTX) Toxin

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