Novel Innate Immune Genes and Asthma

Univ Of North Carolina Chapel Hill, Chapel Hill NC

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Abstract

We recently discovered the CATERPILLER family which share structural similarities with the NB-LRR (nucleotide-binding, leucine-rich repeat) super-family of disease resistance (R) proteins that constitutes the plant immune system. In the animal kingdom, this family is also known as NOD or NLR. The clinical importance of this family is underscored by the genetic linkage of family members to a number of immunologic disorders. Among the human gene family members, several of these appear to mediate negative regulatory function in controlling an overzealous inflammatory response. Most notable is the Monarch-1 protein which blocks the function of NF-kB inducing kinase (NIK). Inhibition of NIK reduces the expression of an array of chemokines with relevance in asthma. Gene profiling of induced sputum from mildly asthmatic individuals suggests that the Monarch-1 gene is reduced in these individuals relative to controls, supporting the inhibitory role of this gene during inflammation. Another group of family members regulates IL-1 production. Most notable among these is cryopyrin which mediates formation of the inflammasome complex upon stimulation with a number of inducers. The inflammasome complex is required for procaspase 1 processing to mature caspase 1. In turn, caspase-1 is required for the processing of pro-IL-1 and pro-IL-18 to their mature forms. IL-1 and IL-18 are respectively important in inflammation and TH2 skewing. Cryopyrin is also important in mediating macrophage necrosis which exacerbates inflammation. Thus there are compelling reasons to believe that Monarch-1 and cryopyrin have crucial roles in asthma, however there is no in vivo data to indicate that this is the case. Furthermore we have shown that both of these proteins are ATP-binding proteins, and they exhibit ATPase activity, thus providing ways to modulate their function, which might be important leads to drug discovery. The goals of this proposal are: (1) To study the relevance of Monarch-1 in three animal models of asthma (OVA-induced, endotoxin, and house dust mite and delineate the biochemical effects of Monarch-1 in vivo and ex vivo. (2) To study the relevance of cryopyrin and a cryopyrin-adaptor (ASC) in asthma. (3) To study and identify factors which modulate the nucleotide-binding properties and ATPase function of Monarch-1 and cryopyrin.