Browsing by Subject "cytotoxicity"

Now showing 1 - 2 of 2
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    Molecular mechanisms of cytotoxicity regulation in pseudomonas aeruginosa by the magnedium transporter MGTE
    (2017-07) Chakravarty, Shubham; Anderson, Gregory G.
    The Gram-negative bacterium Pseudomonas aeruginosa causes numerous acute and chronic opportunistic infections in humans. One of its most formidable weapons is a type III secretion system (T3SS), a multi-protein molecular syringe that injects powerful toxins directly into host cells. The toxins lead to cell dysfunction and, ultimately, cell death. Identification of regulatory pathways that control T3SS gene expression may lead to the discovery of novel therapeutics to treat P. aeruginosa infections. In a previous study, it was found that expression of the magnesium transporter gene mgtE inhibits T3SS gene transcription. MgtE-dependent inhibition appeared to interfere with the synthesis or function of the master T3SS transcriptional activator ExsA, although the exact mechanism was unclear. In this work, we demonstrate that mgtE expression acts through the GacAS two-component system to activate transcription of the small regulatory RNAs RsmY and RsmZ. This event ultimately leads to inhibition of exsA translation. Moreover, our data reveal that MgtE acts solely through this pathway to regulate T3SS gene transcription. Our study reveals an important mechanism that may allow P. aeruginosa to fine-tune T3SS activity in response to certain environmental stimuli. In addition, a previous study has shown that the P. aeruginosa gene algR abrogates mgtE mediated regulation of cytotoxicity. AlgR has pleiotropic effects in P. aeruginosa, including regulation of synthesis of the exopolysaccharide alginate. In the second part of my thesis, I show that algR and mgtE genetically crosstalk to inhibit ExsA driven T3SS gene transcription. This genetic interaction between algR and mgtE seems to be specifically directed towards regulation of T3SS gene expression rather than having an indiscriminate effect on multiple virulence attributes in P. aeruginosa. Additionally, we have further demonstrated that AlgR inhibits mgtE transcription. These studies suggest the presence of a T3SS inhibitor that is inhibited by both AlgR and MgtE. Future work will involve transcriptomic and proteomic analysis to identify such an inhibitor. Taken together, this study provides important insight into the molecular mechanisms of mgtE expression and function in P. aeruginosa. We have established that mgtE has pleiotropic effects on cytotoxicity in P. aeruginosa. Thus, given the role that cytotoxicity regulation plays in shaping P. aeruginosa pathogenesis and associated clinical outcomes, mgtE might be an interesting drug target, though extensive future studies are required to validate this proposition. Nevertheless, this research, provides clues for identification of novel therapeutic targets in P. aeruginosa. Hence this work, in the long run, serve to ameliorate the morbidity and mortality in patients infected with P. aeruginosa.
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    The Role of Receptor Interacting Protein Kinases in Diabetogenic Beta-Cell Loss and Hyperglycemia
    (2024-11) Mukherjee, Noyonika; Templin, Andrew T.; Dong, X. Charlie; Elmendorf, Jeffrey S.; Evans-Molina, Carmella; Linnemann, Amelia K.
    Diabetes is characterized by pancreatic -cell loss, insulin insufficiency, and hyperglycemia. Although major efforts have been made to manage diabetes using pharmacological agents that lower blood glucose levels, less effort has been focused on therapies to prevent the two major forms of diabetes, type 1 (T1D) and type 2 diabetes (T2D). Hence, there is a critical need to understand the mechanisms that underlie -cell demise in these diseases, and to develop therapies targeting such mechanisms. Recent studies in non-islet cell types identified receptor interacting protein kinase 1 and 3 (RIPK1 and RIPK3) as mediators of inflammation and programmed cell death. RIPKs are being considered as potential therapeutic target in human diseases including renal, hepatic and neurodegenerative diseases. However, the role of RIPKs in -cell loss in diabetes remains unknown. My thesis work evaluated the roles of RIPK1 and RIPK3 in mediating -cell cytotoxicity and islet inflammation in diabetes pathogenesis. Through the studies, I examined the role of RIPK1 and RIPK3 in -cell loss in response to known inducers of diabetogenic -cell stress, including proinflammatory cytokines, endoplasmic reticulum (ER) stress and islet amyloid deposition. My work revealed roles of RIPK1 and RIPK3 in mediating both caspase-dependent and caspase-independent cell death, kinase activation and transcriptional responses in vitro. Furthermore, I found that RIPK1 and RIPK3 play important roles in regulating glucose homeostasis in mouse models in vivo. The studies revealed a novel role of RIPKs in the pathogenesis of diabetes and suggests that RIPKs might be a potential target to treat or prevent the disease.