Presentation: Three Dimensional (3-D) Model of the PRYSPRY Domain of Pyrin: Implications for Disease Severity in Familial Mediterranean Fever (FMF) and Exploration of Alternative Pathogenetic Mechanism (2007)

844 Three Dimensional (3-D) Model of the PRYSPRY Domain of Pyrin: Implications for Disease Severity in Familial Mediterranean Fever (FMF) and Exploration of Alternative Pathogenetic Mechanism

Background: The gene responsible for the FMF is MEFV and encodes for the pyrin protein. The 3-D structure of the C-terminal PRYSPRY domain of pyrin, harboring most MEFV mutations, has been constructed and mutations were localized upon classification according to the clinical severity of FMF. A suggested mechanism for the pathogenesis of FMF, referred to the direct interactions between caspase-1 and B30.2 (PRYSPRY) domain, may have some areas that need further refinement. Moreover, a protein called SIVA was isolated and confirmed to be a pyrin-interacting protein.
Purpose: a) To construct a 3-D model presenting the direct interaction of the PRYSPRY domain of pyrin with caspase-1; b) To examine whether the "flexible loops" of caspase-1, which interact with crucial functional positions of pyrin, have also access to various distal positions; and c) To analyze potential interactions between the SIVA protein and PRYSPRY domain of pyrin.
Methods: Mutant forms of pyrin have been created by using Site-Directed Mutagenesis. The ability of various pyrin mutants to bind caspase-1 or SIVA protein will be examined by immuno-blotting and immunoprecipitation experiments. The 3-D model of the pyrin PRYSPRY-domain was created following the homology-modeling approach. The derived model was checked for folding and packing errors using the QUANTA-CHARMm program.
Results: The 3-D model revealed that the PRYSPRY pyrin globular domain is formed by a beta sandwich and contains an elongated hydrophobic cavity. Mutations causing severe phenotype are spread on the rim of the cavity while mutations with no severe effects are localized on loops away from the major recognition site of PRYSPRY. The “flexible loops” of caspase-1 may be unable to interact with sites of PRYSPRY domain distally located to the binding cavity. The finding of a putative interaction between the pyrin-interacting, pro-apoptotic protein SIVA protein and the PRYSPRY domain has prompted us to further explore its contribution to the pathogenesis of FMF.
Conclusions: This report approaches the issue of the necessity of alternative pathogenic pathways leading to FMF, taking into consideration the localization of certain mutations on the constructed 3-D model of pyrin and the ability of pyrin’s interacting molecules to have access to the proper interacting sites. It is of particular interest to elucidate further whether any interaction between SIVA protein and PRYSPRY domain may contribute to the pathogenesis of FMF, causing or contributing to serious inflammatory and/or apoptotic processes.

 G.N. Goulielmos, None; E. Eliopoulos, None; E. Petraki, None; E. Fragouli, None; P. Sidiropoulos, None; D. Gumucio, None; D.T. Boumpas, None.