Specific knowledge of C1 inhibitor (C1INH) function and of regulation of its gene can lead to improved therapy of hereditary angioneurotic edema (HANE) and other conditions in which C1INH may play a role. The proposed studies also will contribute to our understanding of genetic disease and mutagenesis, of interferon, interleukin-6 and androgen-mediated gene regulation and of the inhibitory mechanism utilized by the serine proteinase inhibitor (serpin) family. The first specific aim will continue the molecular definition of mutations that result in C1INH deficiency and dysfunction. These studies will test the hypothesis that the C1INH gene contains at least two regions with an enhanced propensity toward mutation. The second specific aim is directed toward an analysis of the structure function relationships in C1INH. This will be accomplished primarily via analysis of recombinant mutant C1INH molecules. Mutations to be introduced will be based either on naturally- occurring dysfunctional mutants, or on predictions made from molecular modeling.
This specific aim will approach three issues: the determinants of target protease specificity, the structural rearrangements that take place in the inhibitor during complex formation, and the functional role of the heavily glycosylated amino terminal domain of the protein. The third specific aim will explore the regulation of expression of the C1INH gene. We hypothesize that the precise regulation of the C1INH gene results from the cooperative interaction of multiple inducing agents, including gamma-IFN, IL-6 and androgens. The initiator driven promoter of the gene will be characterized, as will the cis-acting elements that influence its function. The major known regulators of C1INH expression are gamma-IFN and IL-6. The characterization of the elements responsible for induction of these agents will be completed, as will characterization of the effects of androgens. Finally, the mouse will be examined for its suitability to use for development of a model of HANE. Preliminary data suggest its utility. If this is supported, a C1INH deficient mouse will be developed using gene knockout technology. This would allow precise characterization of the mediators of symptoms in the disease and in vivo analysis of gene regulation. This would be a necessity for the ultimate analysis of agents to enhance C1INH expression in this disease in which symptoms develop in individuals who are heterozygous for the deficiency state.
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