Lung macrophages represent a key first line defense against pathogens. Macrophages sense microbes that induce the production, processing and release of the proinflammatory cytokine IL-1beta. Regulation of IL-1beta is fundamental to many types of lung inflammatory diseases including acute lung injury and sepsis. In this context, macrophages are suppressed in their ability to process and release IL-1beta compared to monocytes. This is despite the fact that, after endotoxin challenge, macrophages contain abundant precursor IL-1beta and caspase-1. Recently, a new class of host defense molecules has been described that may shed light on this important difference. These proteins, termed CATERPILLERs, are homologues of plant disease resistance genes. They contain CARD and PYRIN domains that direct molecular groupings. One such grouping, termed the inflammasome, regulates the ability of caspase-1 to cleave the precursors of IL-1beta and IL-18 to their functional forms. This led us to hypothesize that modifications of the inflammasome dictate innate host responses in macrophages. Preliminary data presented here show that signaling through tyrosine kinase and JAK/STAT pathways can respectively activate or suppress function of the inflammasome. Therefore, to determine the specifics of this central innate host response, this application uses the monocyte macrophage difference to discover key inflammasome structure function relationships. Specifically, this proposal will 1) determine the role of CARD and PYRIN domain proteins as regulators of IL-1beta release during monocyte maturation; 2) test the hypothesis that JAK/STAT pathways induce functional changes in the inflammasome; 3) determine how certain CATERPILLER proteins inhibit function of the inflammasome; and 4) test the hypothesis that tyrosine kinase activity is required for correct inflammasome assembly. Successful completion of these aims will provide novel insights into innate host responses and create new therapeutic opportunities to prevent and treat inflammatory lung diseases.
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