Title of Oral/Poster Presentation

Investigating the role of an identified Pi-bulge in IpaD on Shigella flexneri virulence

Class

Article

Department

Chemistry and Biochemistry

Faculty Mentor

Nicholas Dickenson

Presentation Type

Poster Presentation

Abstract

Shigella flexneri is a bacterial pathogen that, upon infection, causes bacillary dysentery. Shigella uses a Type III secretion system (T3SS) which provides a unidirectional conduit between the bacterial and host cell cytoplasm, allowing translocation of effector proteins into the host cell. Invasion Plasmid Antigen D (IpaD) is a key component of this complex and is responsible for controlling the secretion of effector proteins through the immature apparatus. This role appears to be central to Shigella's virulence and may be regulated by structural changes that follow IpaD interaction with bile salts in the host GI tract. Here, we report on a series of studies characterizing specific point mutants that were designed to stabilize an identified Pi-bulge within IpaD that we believe to be responsible for the observed structural flexibility of IpaD. Specifically, we used a combination of spectroscopic biophysical methods and phenotype assays to investigate the effects of each mutation on both protein structure and Shigella virulence. Interestingly, while the IpaD mutants appear to have little overall effect on protein structure, they result in significant differences when tested for bile salt sensitivity with respect to virulence. Together, these results suggest that we have in fact targeted a key region responsible for sensing bile salts in which minor local structural perturbations reduce/eliminate bile salt sensitivity and reduce the risk of cellular invasion following Shigella exposure.

Start Date

4-9-2015 3:00 PM

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Apr 9th, 3:00 PM

Investigating the role of an identified Pi-bulge in IpaD on Shigella flexneri virulence

Shigella flexneri is a bacterial pathogen that, upon infection, causes bacillary dysentery. Shigella uses a Type III secretion system (T3SS) which provides a unidirectional conduit between the bacterial and host cell cytoplasm, allowing translocation of effector proteins into the host cell. Invasion Plasmid Antigen D (IpaD) is a key component of this complex and is responsible for controlling the secretion of effector proteins through the immature apparatus. This role appears to be central to Shigella's virulence and may be regulated by structural changes that follow IpaD interaction with bile salts in the host GI tract. Here, we report on a series of studies characterizing specific point mutants that were designed to stabilize an identified Pi-bulge within IpaD that we believe to be responsible for the observed structural flexibility of IpaD. Specifically, we used a combination of spectroscopic biophysical methods and phenotype assays to investigate the effects of each mutation on both protein structure and Shigella virulence. Interestingly, while the IpaD mutants appear to have little overall effect on protein structure, they result in significant differences when tested for bile salt sensitivity with respect to virulence. Together, these results suggest that we have in fact targeted a key region responsible for sensing bile salts in which minor local structural perturbations reduce/eliminate bile salt sensitivity and reduce the risk of cellular invasion following Shigella exposure.