A Structural Study on the Listeria Monocytogenes Internalin A-Human E-cadherin Interaction: A Molecular Tool to Investigate the Effects of Missense Mutations.

Luca Dellafiora,Chiara Dall’Asta,Marina Nadia Losio,Virginia Filipello,Gianni Galaverna,Guido Finazzi

doi:10.3390/toxins12010060

Abstract

Listeria monocytogenes is a widespread foodborne pathogen of high concern and internalin A is an important virulence factor that mediates cell invasion upon the interaction with the host protein E-cadherin. Nonsense mutations of internalin A are known to reduce virulence. Although missense mutations are largely overlooked, they need to be investigated in respect to their effects in cell invasion processes. This work presented a computational workflow to early characterize internalin A missense mutations. The method reliably estimated the effects of a set of engineered missense mutations in terms of their effects on internalin A–E-cadherin interaction. Then, the effects of mutations of an internalin A variant from a L. monocytogenes isolate were calculated. Mutations showed impairing effects on complex stability providing a mechanistic explanation of the low cells invasion capacity previously observed. Overall, our results provided a rational approach to explain the effects of internalin A missense mutations. Moreover, our findings highlighted that the strength of interaction may not directly relate to the cell invasion capacity reflecting the non-exclusive role of internalin A in determining the virulence of L. monocytogenes. The workflow could be extended to other virulence factors providing a promising platform to support a better molecular understanding of L. monocytogenes epidemiology.

Highlights

Listeria monocytogenes is a widespread, gram-positive, opportunistic intracellular pathogen with the capacity to actively invade and multiply within a broad range of animal cells [1]
While premature stop codons (PMSCs) are usually associated with an attenuated invasiveness, the effect of missense mutations on inlA gene product (InlA)-Ecad interaction, which may either result in lower or higher invasion capacity, can be an important factor to get dissected for a preliminary evaluation of either novel L. monocytogenes isolates or new and uncharacterized InlA variants
In the context of providing a framework for the rapid and early identification of strains to be considered at risk, the present study aimed at checking whether a structure-based computational approach can reliably compute the effects of missense mutation in the InlA-Ecad complex formation

Summary

Introduction

Listeria monocytogenes is a widespread, gram-positive, opportunistic intracellular pathogen with the capacity to actively invade and multiply within a broad range of animal cells [1]. L. monocytogenes is the etiologic agent of listeriosis, a foodborne disease affecting both humans and animals (mainly ruminants) [2,3]. Concerning human cases, listeriosis generally affects people with an altered immune system and it is characterized by low incidence and high case-fatality rate (up to 30%), with a great. L. monocytogenes invades the human body thanks to the ability of crossing the gastrointestinal barrier by inducing its own endocytosis in epithelial cells. The infection typically gets a broad diffusion through the host body when bacteria reach the bloodstream [6]

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