The type III secretion system of Gram-negative bacterial pathogens creates one of the most direct interfaces between pathogens and their hosts. These `needle-like' molecular machines inject bacterial effector proteins directly into host cells for the purpose of destroying an innate immune response and facilitating bacterial replication, dissemination, and disease progression. Effector proteins are unique virulence factors in that they often capture or mimic the properties of host signal transduction molecules. The present study focuses on three important bacterial type III effector families. First, we will interrogate a large family of bacterial Guanine-nucleotide exchange factors (GEFs) required for Salmonella, Shigella, and enterohaemorrhagic E. coli pathogenesis, respectively, through their common ability to activate Rho-family GTPase signaling cascades. The studies described here will advance recent high-throughput genetic screening approaches to identify bacterial effector protein localization within the host cellular environment. Findings from these preliminary studies will be applied to uncover the system dynamics of host-pathogen interactions responsible for Shigella invasion, and particularly the role of host acidic phospholipids on bacterial GEF signaling functions (Aim 1). Second, we will characterize the novel enzymatic mechanism of the Invasion plasmid antigen J (IpaJ) family of bacterial cysteine proteases that catalyze the proteolytic elimination of N-myristoyl modifications on host ARF GTPase cellular substrates. Insights gleaned from these studies will be advanced through a detailed analysis of Shigella innate immune pathway evasion, and specifically the role of protein demyristoylation in this process (Aim 2). Finally, we will investigate orphan members of the Shigella E3-ubiquitin ligase superfamily, and specifically their ability to modulate host immune components through protein ubiquitylation (Aim 3). Developing new drugs that target bacterial and host enzyme complexes would be an innovative approach to combat emerging antibiotic resistant microbes. Therefore, by revealing molecular details of type III effector family functions, from biochemistry to systems biology, we will uncover sites of potential weakness in bacterial pathogens that may be exploited for therapeutic intervention. Importantly, these studies will also provide new insights into the pathogenic mechanisms of numerous infectious disease agents and also into the biology of the human host.
Small molecules including guanine-nucleotides, phosphoinositides, and ubiquitin peptides are essential components of many cellular signal transduction cascades, and represent major targets of bacterial toxins and effector proteins. This application examines the ability of bacterial Type III effector proteins to hijack human signa transduction networks that utilize these common molecular components. A deeper understanding of the enzymatic and biochemical interface between bacterial effector proteins and human GTPases, the membrane lipids that they are attached to, and the immunological systems regulated by ubiquitin will lead to a more complete knowledge of numerous bacterial pathogenic mechanisms and may reveal new aspects of human infectious disease.
|Weigele, Bethany A; Orchard, Robert C; Jimenez, Alyssa et al. (2017) A systematic exploration of the interactions between bacterial effector proteins and host cell membranes. Nat Commun 8:532|
|Perelman, Sofya S; Abrams, Michael E; Eitson, Jennifer L et al. (2016) Cell-Based Screen Identifies Human Interferon-Stimulated Regulators of Listeria monocytogenes Infection. PLoS Pathog 12:e1006102|
|Jimenez, Alyssa; Chen, Didi; Alto, Neal M (2016) How Bacteria Subvert Animal Cell Structure and Function. Annu Rev Cell Dev Biol 32:373-397|
|de Jong, Maarten F; Liu, Zixu; Chen, Didi et al. (2016) Shigella flexneri suppresses NF-?B activation by inhibiting linear ubiquitin chain ligation. Nat Microbiol 1:16084|
|Dobbs, Nicole; Burnaevskiy, Nikolay; Chen, Didi et al. (2015) STING Activation by Translocation from the ER Is Associated with Infection and Autoinflammatory Disease. Cell Host Microbe 18:157-68|
|Burnaevskiy, Nikolay; Peng, Tao; Reddick, L Evan et al. (2015) Myristoylome profiling reveals a concerted mechanism of ARF GTPase deacylation by the bacterial protease IpaJ. Mol Cell 58:110-22|
|Reddick, L Evan; Alto, Neal M (2014) Bacteria fighting back: how pathogens target and subvert the host innate immune system. Mol Cell 54:321-8|
|Selyunin, Andrey S; Reddick, Lovett Evan; Weigele, Bethany A et al. (2014) Selective protection of an ARF1-GTP signaling axis by a bacterial scaffold induces bidirectional trafficking arrest. Cell Rep 6:878-91|
|Burnaevskiy, Nikolay; Fox, Thomas G; Plymire, Daniel A et al. (2013) Proteolytic elimination of N-myristoyl modifications by the Shigella virulence factor IpaJ. Nature 496:106-9|
|Alto, Neal M; Orth, Kim (2012) Subversion of cell signaling by pathogens. Cold Spring Harb Perspect Biol 4:a006114|
Showing the most recent 10 out of 19 publications