ADP-ribosylating and vacuolating cytotoxin of Mycoplasma pneumoniae represents unique virulence determinant among bacterial pathogens. Proc Nat Acad Sci USA

Department of Microbiology and Immunology, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 05/2006; 103(17):6724-9. DOI: 10.1073/pnas.0510644103
Source: PubMed

ABSTRACT Unlike many bacterial pathogens, Mycoplasma pneumoniae is not known to produce classical toxins, and precisely how M. pneumoniae injures the respiratory epithelium has remained a mystery for >50 years. Here, we report the identification of a virulence factor (MPN372) possibly responsible for airway cellular damage and other sequelae associated with M. pneumoniae infections in humans. We show that M. pneumoniae MPN372 encodes a 68-kDa protein that possesses ADP-ribosyltransferase (ART) activity. Within its N terminus, MPN372 contains key amino acids associated with NAD binding and ADP-ribosylating activity, similar to pertussis toxin (PTX) S1 subunit (PTX-S1). Interestingly, MPN372 ADP ribosylates both identical and distinct mammalian proteins when compared with PTX-S1. Remarkably, MPN372 elicits extensive vacuolization and ultimate cell death of mammalian cells, including distinct and progressive patterns of cytopathology in tracheal rings in organ culture that had been previously ascribed to infection with WT virulent M. pneumoniae. We observed dramatic seroconversion to MPN372 in patients diagnosed with M. pneumoniae-associated pneumonia, indicating that this toxin is synthesized in vivo and possesses highly immunogenic epitopes.

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    • "The N-terminal region of CARDS toxin shares limited identity with the catalytic domain of many ADPRT toxins (Kannan and Baseman, 2006). To detect protein scaffolds compatible with the CARDS toxin amino acid sequence, we used the program HHPRED and the entire CARDS toxin amino acid sequence as the query. "
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    ABSTRACT: Community-acquired respiratory distress syndrome (CARDS) toxin from Mycoplasma pneumoniae is a 591 amino acid virulence factor with ADP-ribosyltransferase (ADPRT) and vacuolating activities. It is expressed at low levels during in vitro growth and at high levels during colonization of the lung. Exposure of experimental animals to purified recombinant CARDS toxin alone is sufficient to recapitulate the cytopathology and inflammatory responses associated with M. pneumoniae infection in humans and animals. Here, by molecular modeling, serial truncations and site-directed mutagenesis, we show that the N-terminal region is essential for ADP-ribosylating activity. Also, by systematic truncation and limited proteolysis experiments we identified a portion of the C-terminal region that mediates toxin binding to mammalian cell surfaces and subsequent internalization. In addition, the C-terminal region alone induces vacuolization in a manner similar to full-length toxin. Together, these data suggest that CARDS toxin has a unique architecture with functionally separable N-terminal and C-terminal domains.
    Molecular Microbiology 06/2014; 93(3). DOI:10.1111/mmi.12680 · 5.03 Impact Factor
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    • "It possesses only a minor ability to injure respiratory epithelial cells by producing an excess of activated oxygen within the infected cells [for review, see Waites & Talkington, 2004]. Recent evidence has shown that M. pneumoniae produces the community acquired respiratory distress syndrome toxin, but its pathogenic role in human illness still remains to be elucidated [Hardy et al., 2009; Kannan & Baseman, 2006]. Nevertheless, M. pneumoniae is a major pathogen of primary atypical pneumonia as well as a number of extrapulmonary diseases. "
    Advances in the Etiology, Pathogenesis and Pathology of Vasculitis, 10/2011; , ISBN: 978-953-307-651-5
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    • "This pathogenic mycoplasma utilizes multiple adherence mechanisms to colonize and invade airway cells, leading to loss of respiratory epithelium integrity, decreased ciliary movement, and increased cellular vacuolation and exfoliation (Carson et al., 1979, Collier et al., 1983, Tyron et al., 1992, Baseman, 1993, Krause et al., 2001, Balasubramanian et al., 2009). Recently, we identified an ADP ribosylating and vacuolating toxin in M. pneumoniae that can reproduce the cytopathology phenotype associated with mycoplasma infection (Kannan et al., 2006, Hardy et al., 2009). In addition to the overt histopathology that accompanies M. pneumoniae infection, we earlier described alterations in host metabolism that precede and parallel "
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    ABSTRACT: We identified Mpn133 as a Ca(2+)-dependent cytotoxic nuclease of Mycoplasma pneumoniae. Flow cytometry analysis and immunofluorescence studies revealed the binding and internalization of recombinant Mpn133 (rMpn133) in human airway A549 cells. Amino acid sequence comparisons of Mpn133 with other mycoplasma nucleases demonstrated the presence of a unique glutamic acid-, lysine- and serine-rich region (EKS region; amino acids 72-110). Deletion of this EKS peptide (rMpn133(Δ72-110)) abrogated its binding and internalization but not its nuclease activity. The function of the EKS region in host cell trafficking and nuclear localization was reinforced by the successful delivery of EKS-conjugated mCherry protein into A549 cells. rMpn133, but not rMpn133(Δ72-110), induced apoptosis-like death in A549 cells. This observation suggested a unique role of Mpn133 as an important contributor to M. pneumoniae-associated life cycle events and as a virulence factor in host-associated cytopathologies. In addition, the distinct property of the EKS peptide in delivery of proteins, like mCherry, into target cells opens new avenues to the establishment of novel concepts of drug delivery and therapy.
    Cellular Microbiology 12/2010; 12(12):1821-31. DOI:10.1111/j.1462-5822.2010.01513.x · 4.82 Impact Factor
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