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The Haemophilus ducreyi LspA1 protein inhibits phagocytosis by using a new mechanism involving activation of C-terminal Src kinase.
- Source :
-
MBio [mBio] 2014 May 20; Vol. 5 (3), pp. e01178-14. Date of Electronic Publication: 2014 May 20. - Publication Year :
- 2014
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Abstract
- Unlabelled: Haemophilus ducreyi causes chancroid, a sexually transmitted infection. A primary means by which this pathogen causes disease involves eluding phagocytosis; however, the molecular basis for this escape mechanism has been poorly understood. Here, we report that the LspA virulence factors of H. ducreyi inhibit phagocytosis by stimulating the catalytic activity of C-terminal Src kinase (Csk), which itself inhibits Src family protein tyrosine kinases (SFKs) that promote phagocytosis. Inhibitory activity could be localized to a 37-kDa domain (designated YL2) of the 456-kDa LspA1 protein. The YL2 domain impaired ingestion of IgG-opsonized targets and decreased levels of active SFKs when expressed in mammalian cells. YL2 contains tyrosine residues in two EPIYG motifs that are phosphorylated in mammalian cells. These tyrosine residues were essential for YL2-based inhibition of phagocytosis. Csk was identified as the predominant mammalian protein interacting with YL2, and a dominant-negative Csk rescued phagocytosis in the presence of YL2. Purified Csk phosphorylated the tyrosines in the YL2 EPIYG motifs. Phosphorylated YL2 increased Csk catalytic activity, resulting in positive feedback, such that YL2 can be phosphorylated by the same kinase that it activates. Finally, we found that the Helicobacter pylori CagA protein also inhibited phagocytosis in a Csk-dependent manner, raising the possibility that this may be a general mechanism among diverse bacteria. Harnessing Csk to subvert the Fcγ receptor (FcγR)-mediated phagocytic pathway represents a new bacterial mechanism for circumventing a crucial component of the innate immune response and may potentially affect other SFK-involved cellular pathways.<br />Importance: Phagocytosis is a critical component of the immune system that enables pathogens to be contained and cleared. A number of bacterial pathogens have developed specific strategies to either physically evade phagocytosis or block the intracellular signaling required for phagocytic activity. Haemophilus ducreyi, a sexually transmitted pathogen, secretes a 4,153-amino-acid (aa) protein (LspA1) that effectively inhibits FcγR-mediated phagocytic activity. In this study, we show that a 294-aa domain within this bacterial protein binds to C-terminal Src kinase (Csk) and stimulates its catalytic activity, resulting in a significant attenuation of Src kinase activity and consequent inhibition of phagocytosis. The ability to inhibit phagocytosis via Csk is not unique to H. ducreyi, because we found that the Helicobacter pylori CagA protein also inhibits phagocytosis in a Csk-dependent manner. Harnessing Csk to subvert the FcγR-mediated phagocytic pathway represents a new bacterial effector mechanism for circumventing the innate immune response.<br /> (Copyright © 2014 Dodd et al.)
- Subjects :
- Animals
Bacterial Proteins chemistry
Bacterial Proteins genetics
CSK Tyrosine-Protein Kinase
Chancroid microbiology
Enzyme Activation
Haemophilus ducreyi chemistry
Haemophilus ducreyi genetics
Host-Pathogen Interactions
Humans
Lectins chemistry
Lectins genetics
Lectins immunology
Protein Structure, Tertiary
src-Family Kinases chemistry
src-Family Kinases genetics
Bacterial Proteins immunology
Chancroid enzymology
Chancroid immunology
Haemophilus ducreyi immunology
Phagocytosis
src-Family Kinases immunology
Subjects
Details
- Language :
- English
- ISSN :
- 2150-7511
- Volume :
- 5
- Issue :
- 3
- Database :
- MEDLINE
- Journal :
- MBio
- Publication Type :
- Academic Journal
- Accession number :
- 24902122
- Full Text :
- https://doi.org/10.1128/mBio.01178-14