Distinct mechanisms of integrin binding by Yersinia pseudotuberculosis adhesins determine the phagocytic response of host macrophages

Abstract

SummaryThe enteropathogenic yersiniae express two outer membrane adhesins, invasin and YadA, that contribute to pathogenesis. While invasin binds directly to b b b b 1 integrin receptors with high affinity, YadA binds indirectly through extracellular matrix (ECM) components. In this study, Yersinia pseudotuberculosis inv and yadA mutants were used to investigate how these distinct binding mechanisms compare and potentially compete in activating signalling pathways and promoting bacterial uptake by host macrophages. The efficiency of adhesin-mediated phagocytic responses was found to be dependent on the relative expression of invasin and YadA on the bacterial surface as well as the expression of ECM proteins in the extracellular milieu. Under conditions of low concentrations of ECM, invasin was found to be the dominant adhesin, promoting high levels of phagocytosis coincident with robust and sustained activation of the protein tyrosine kinases Fak and Pyk2, phosphorylation of the adaptor molecule Cas and activation of the small GTPase Rac1. In the presence of higher concentrations of ECM, YadA became the dominant functional adhesin through its ability to engage integrin receptors via an ECM bridge. We propose a model whereby invasin promotes robust and prolonged activation of phagocytic signalling cascades by inducing a 'highaffinity' integrin conformation as well as integrin clustering. We postulate that YadA-ECM promotes phagocytosis through a more transient activation of signalling cascades that arises from integrin clustering in the context of a cross-linked fibrillar ECM network.

β1 Integrin-Dependent Engulfment of Yersinia enterocolitica by Macrophages Is Coupled to the Activation of Autophagy and Suppressed by Type III Protein Secretion

“…Because Src also controls cell invasion by yersiniae, we used cytochalasin D to assess the role of bacterial internalization on autophagy induction. Cytochalasin D depolymerizes F-actin and thereby prevents bacterial cell invasion (58,59,61). This drug similarly inhibited the conversion of LC3-II triggered by WA-C and WA-⌬lcrD (Fig.…”

A Conserved Glycine Residue of Trimeric Autotransporter Domains Plays a Key Role inYersiniaAdhesin A Autotransport

“…Therefore, it is strictly dose dependent and requires high concentrations of invasin (17,20,38). In contrast, YadA as a trimeric protein provides three ECM binding pockets with each complex, analogous to the Haemophilus adhesin Hia (44); moreover, it is capable of binding to various ligands.…”

Unusual, Virulence Plasmid-Dependent Growth Behavior of Yersinia enterocolitica in Three-Dimensional Collagen Gels

“…As reported recently, the extracellular environment plays a critical role in defining Yersinia-host cell interactions (11,22). The ECM content is one of the determining factors for the phagocytic response of host macrophages.…”

“…Yops are microinjected into host cells by the TTSS and interfere with a variety of cell functions, including cytoskeletal regulation, cytokine production, and the control of apoptosis, to suppress the immune response to infection, resulting in predominantly extracellular survival of the pathogen in the lymphoid tissue of the host (reviewed in references 1, 16, 20, and 42). Besides the virulence plasmid, essential for virulence are chromosomally located genes, such as the invasin-encoding gene inv and the yersiniabactin (ybt) determinant, located on the high pathogenicity island (HPI) which is responsible for ferric iron provision (reviewed in reference 37).As reported recently, the extracellular environment plays a critical role in defining Yersinia-host cell interactions (11,22). The ECM content is one of the determining factors for the phagocytic response of host macrophages.…”