Molecular Dissection of the Campylobacter jejuni CadF and FlpA Virulence Proteins in Binding to Host Cell Fibronectin.

Prabhat K Talukdar,Nicholas M Negretti,Kyrah L Turner,Michael E Konkel

doi:10.3390/microorganisms8030389

Prabhat K Talukdar, Nicholas M Negretti + Show 2 more

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https://doi.org/10.3390/microorganisms8030389

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Journal: Microorganisms	Publication Date: Mar 11, 2020
Citations: 23	License type: CC BY 4.0

Affiliation: Washington State University

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.

Highlights

Fibronectin (FN)-binding proteins (FNBPs) are members of the Microbial Surface Components Recognizing Adhesive Matrix Molecule(s) (MSCRAMMs) family
The experiments performed revealed that: (1) neither CadF nor fibronectin-like protein A (FlpA) alone could restore the defect in binding of C. jejuni ∆cadF ∆flpA double mutant to host cells; (2) CadF and FlpA binding to FN is additive; (3) both CadF and FlpA are necessary for C. jejuni activation of the MAPK signaling pathway (Erk 1/2); and (4) both CadF and FlpA are required for the delivery of the Cia effector proteins into the cytosol of a host cell
The experiments performed in this study revealed that CadF and FlpA are bi-functional proteins that act in a cooperative manner to first bind to host cells and to stimulate signal transduction pathways, including the MAPK pathway, involved in C. jejuni cell invasion

Summary

Introduction

Fibronectin (FN)-binding proteins (FNBPs) are members of the Microbial Surface Components Recognizing Adhesive Matrix Molecule(s) (MSCRAMMs) family. These proteins are bacterial surface proteins that mediate the attachment of bacteria to FN and can promote adhesion to cells. Given that FNBPs frequently contribute in establishing an infection, a significant amount of effort has been put forth to identify and characterize these proteins in both Gram-positive and Gram-negative bacteria. FNBPs have been identified in Gram-negative pathogens, such as ShdA in Salmonella enterica serotype Typhimurium [4], YadA in Yersinia spp. Defining the role of MSCRAMMs in promoting bacteria–host interactions has provided a better understanding of the process of microbial colonization and disease

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