The over-reaction of the immune system to invasive pathogens causes sepsis, which leads to cardiac dysfunction. The hyperinflammation-induced cytokine storm in septic-related mortality is controlled by inflammatory mediators, including interleukin (IL)-1b and the alarmin high mobility group box 1 (HMGB1), which are produced by inflammasomes upon its activation. Recruitment of the inflammatory caspase-1 to inflammasomes through a caspase-recruitment domain (CARD)-CARD-mediated interaction step with the inflammasome adaptor ASC, is essential for its activation and, consequently, induction of the septic cytokine storm. However, the molecular mechanism controlling caspase-1 activation is poorly understood. Three CARD-only proteins (COPs), COP/Pseudo-ICE, ICEBERG, and INCA, share high sequence identity with the caspase-1 CARD, and have been shown to interact with caspase-1 when over expressed and inhibit IL-1b secretion. However, these studies were performed by over expression in artificial cell systems irrelevant for inflammasome biology, but not with endogenous proteins. My hypothesis is that COPs bind to inflammasome components, such as caspases, ASC, or CARD containing PRRs (so called NLRCs) in macrophages, thereby blocking the CARD-CARD interactions necessary for recruiting caspase to inflammasomes for their activation, preventing cytokine release and the cytokine storm associated with sepsis. In this work, I will investigate the role of COP/Pseudo-ICE in macrophages and in ameliorating sepsis in vivo using a novel mouse model. My first aim is to determine the molecular mechanism by which COP/Pseudo-ICE regulates inflammasomes in response to LPS. Biochemical studies will be performed in human and mouse macrophages upon COP/Pseudo-ICE silencing and overexpression to determine inflammasome activity. My second aim is to determine the inhibitory role of COP/Pseudo-ICE during experimental sepsis in vivo, utilizing a novel humanized mouse strain expressing COP/Pseudo-ICE. I expect that expression of COP/Pseudo-ICE will prevent lethal systemic inflammation in response to LPS and in an experimental cecal ligation and puncture (CLP) polymicrobial sepsis model. Through this work, I expect to elucidate the role of COP/Pseudo-ICE in inflammasome regulation, and in ameliorating lethal systemic inflammation in vivo. Results from my studies will advance our knowledge on how inflammatory caspases are regulated and could open up a novel avenues for sepsis treatment.
|Effective start/end date||7/1/15 → 6/30/17|
- American Heart Association Midwest Affiliate (15PRE25700116)