Abstract 4537: Computational modeling and characterization of Diedel proteins that regulate highly-conserved immune signaling

Abstract

Abstract The NF-kB and JAK/STAT pathways are well-established signal transduction pathways, conserved from insects to mammals. They regulate several key biological processes such as cellular proliferation, stem cell maintenance, hematopoiesis and innate immunity responses. Consequently, their dysregulation results in aberrant conditions, often with deleterious consequences. It is well documented that a variety of human diseases, especially cancer and immune-related conditions are associated with various components of these pathways. The focus of this study is the protein Diedel, which was identified as one of the novel genes involved in the regulation of the JAK/STAT pathway in a genome-wide RNA interference screen in Drosophila cells. Drosophila Diedel and its viral homolog also suppress the conserved Imd-mediated NF-kB pathway in flies. Diedel is a small cysteine-rich protein: It is comprised of only 115 amino acids out of which 10 are cysteines. A recent crystal structure has revealed that Diedel is composed of two sub-domains and incorporates two special structural features, i.e. a hydrophobic surface patch suggesting a putative interaction site, and a cis/trans conformation for a proline residue that may be relevant to its physiological mechanism. However, its precise molecular function and mechanism of action still remains unclear. Based on current sequence information in the databases, Diedel seems to be conserved in drosophilids, the aphid Acyrtosiphon pisum, and insect DNA viruses of the Baculoviridae and Ascoviridae families. While investigating the mechanism of infection of Drosophila melanogaster larvae by the parasitic wasp, Leptopilina heterotoma, we have uncovered two wasp venom sequences that are putative Diedel homologs. This study explores the detailed characterization of various Diedel homologs with an end to establishing structure-function correlations in this family of novel proteins, using a combined tool-kit of template based modeling, sequence and structure analyses algorithms. Our results confirm a conserved structural fold but there are significant sequence differences among the homologs. We present a comparative analysis of the theoretical models of Diedel homologs and their biophysical characterization. This study will help elucidate the molecular function of the parasite Diedel proteins in suppressing the fly’s immune response. Our findings will also point to new ways by which dysregulated immune signaling can be turned down and these findings will potentially have implications in treating inflammation and cancer in humans. Citation Format: Aulon Jerliu, Mary Ellen Heavner, Shubha Govind, Shaneen Singh. Computational modeling and characterization of Diedel proteins that regulate highly-conserved immune signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4537. doi:10.1158/1538-7445.AM2017-4537