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Molecular Dissection of the Campylobacter jejuni CadF and FlpA Virulence Proteins in Binding to Host Cell Fibronectin
Prabhat K Talukdar1, Nicholas M Negretti1, Kyrah L Turner1
1School of Molecular Biosciences, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-7520, USA.
Abstract:
Campylobacter jejuni, a zoonotic pathogen that frequently colonizes poultry, possesses two Microbial Surface Components Recognizing Adhesive Matrix Molecule(s) (MSCRAMMs) termed CadF and FlpA that bind to the glycoprotein fibronectin (FN). Previous to this study, it was not known whether the CadF and FlpA proteins were functionally redundant or if both were required to potentiate host cell binding and signaling processes. We addressed these questions by generating a complete repertoire of cadF and flpA mutants and complemented isolates, and performing multiple phenotypic assays. Both CadF and FlpA were found to be necessary for the maximal binding of C. jejuni to FN and to host cells. In addition, both CadF and FlpA are required for the delivery of the C. jejuni Cia effector proteins into the cytosol of host target cells, which in turn activates the MAPK signaling pathway (Erk 1/2) that is required for the C. jejuni invasion of host cells. These data demonstrate the non-redundant and bi-functional nature of these two C. jejuni FN-binding proteins. Taken together, the C. jejuni CadF and FlpA adhesins facilitate the binding of C. jejuni to the host cells, permit delivery of effector proteins into the cytosol of a host target cell, and aid in the rewiring of host cell signaling pathways to alter host cell behavior.
Insights
Campylobacter jejuni uses two fibronectin-binding proteins, CadF and FlpA, which are essential for maximal host cell adhesion and invasion by delivering effector proteins and activating host cell signaling pathways.
Area of Science:
- Microbiology
- Cellular Biology
- Pathogen-Host Interactions
Background:
- Campylobacter jejuni is a significant zoonotic pathogen.
- It colonizes poultry and possesses two fibronectin-binding proteins, CadF and FlpA.
- The functional redundancy of CadF and FlpA was previously unknown.
Purpose of the Study:
- To investigate the functional roles of CadF and FlpA in C. jejuni.
- To determine if these proteins are redundant or essential for host cell interactions.
- To elucidate their involvement in host cell binding, effector delivery, and signaling.
Main Methods:
- Generation of comprehensive cadF and flpA mutant and complemented strains.
- Phenotypic assays to assess bacterial binding to fibronectin and host cells.
- Analysis of Cia effector protein delivery and MAPK signaling pathway activation.
Main Results:
- Both CadF and FlpA are crucial for maximal C. jejuni binding to fibronectin and host cells.
- These proteins are required for delivering Cia effectors into host cell cytosol.
- Activation of the Erk 1/2 MAPK pathway by Cia effectors is essential for bacterial invasion.
Conclusions:
- CadF and FlpA are non-redundant and bi-functional adhesins in C. jejuni.
- They facilitate bacterial adhesion, effector protein translocation, and host cell signaling modulation.
- These proteins are key determinants of C. jejuni's ability to colonize and invade host cells.
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