Comparative Modeling and Functional Characterization of Two Enzymes of the Cyclooxygenase Pathway in Drosophila melanogaster

Eicosanoids are biologically active molecules oxygenated from twenty carbon polyunsaturated fatty acids. Natural eicosanoids exert potent biological effects in humans, and a great deal of pharmaceutical research has led to the discovery of compounds for selective inhibition of specific enzymes in eicosanoid biosynthesis. Coupled with different receptors, eicosanoids mediate various physiological and pathophysiological processes, including fever generation, pain response, vasoconstriction, vasodilation, platelet aggregation, platelet declumping, body temperature maintenance and sleep-wake cycle regulation. In mammals, the eicosanoid biosynthesis has three pathways: the cyclooxygenase (COX) pathway, the lipoxygenase (LOX) pathway and the epoxygenase pathway. The COX pathway synthesizes prostanoids, which are important signaling molecules in inflammation. Because of their central role in inflammatory disease and human health, COX enzymes continue to be a focus of intense research as new details emerge about their mechanism of action and their interactions with NSAIDs. To date, the majority of studies dealing with the COX pathway are centered on mammalian systems. Although the literature is rich in speculations that prostaglandins are central signaling molecules for mediating and coordinating insect cellular immunity, genes responsible for encoding COX or COX-like enzymes and other enzymes in the COX pathway have not been reported in insects. The value of Drosophila melanogaster as a model organism is well established, and the fundamental regulatory signaling mechanisms that regulate immunity at the cellular level in human and flies are conserved. Given the importance of eicosanoids in mammalian and insect immunity, this study was designed to identify and characterize the enzymes that mediate eicosanoid biosynthesis in D. melanogaster computationally. After a preliminary extensive search for putative D. melanogaster homologues for all enzymes in the COX pathway, we conducted a systematic, comprehensive, and detailed computational investigation for two enzymes, COX and prostaglandin E synthase (PGES) in an endeavor to model and characterize the possible candidates and identify those that possess all the requisite sequence and structural motifs to qualify as valid COX(s)/PGE synthase proteins. In this study, we report the presence of qualified D. melanogaster COX(s)/PGE synthase proteins, characterize their biophysical properties, and compare them with their mammalian counterparts. This study lays the groundwork for further exploration of these proteins and establishing their role in D. melanogaster inflammation and immunity, opening up avenues for addressing the use of this model organism in COX signaling and its crosstalk with other signaling pathways