Co-evolution of the Opioid/Orphanin Gene Family and Cognate Receptor Gene Families

University Of Denver, Denver CO

Investigators

Abstract

Title:Co-evolution of the Opioid/Orphanin Gene Family and Cognate Receptor Gene Families. PI: Robert M. Dores. Institution : University of Denver Communication among organ systems is accomplished by two intercellular communication systems, the nervous system and the endocrine system, that facilitates the flow of information throughout the body. In these communication networks, critical messages are carried by chemical signals (ligands) that interact in a highly selective manner with specific receptors on a target cell, a "lock and key" strategy. The origin of these ligand/receptor interactions are unknown, but the studies in this proposal will examine species from old lineages in order to reconstruct the transformations that have occurred in ligand-coding and receptor-coding genes during the evolution of distinct chemical communication networks. In order to study the co-evolution of ligand-coding genes and their corresponding receptor-coding genes this proposal will use the opioid/orphanin ligand-coding gene family (the source of opioid and melanocortin ligands), the opioid receptor-coding gene family and the melanocortin receptor gene family, which provide excellent models. The opioid/orphanin ligands influence analgesia, cardiovascular function, and some actions of the immune system, while the melanocortins are involved in chronic stress regulation, fat and glucose metabolism, and feeding behavior. Students will analyze species at critical branch points in the radiation of vertebrates such as: the lungfish, Neoceratodus forsteri, the white sturgeon, Acipenser transmontanus, the horn shark, Heterodontus francisci , the ratfish, Hydrolagus colliei, and the jawless vertebrates, Myxine glutinosa (hagfish) and Petromyzon marinus (lamprey). Studies will integrate the cloning of ligand coding genes with the cloning of their respective cognate receptor-coding genes in these species. The cloned receptors will be expressed in cell lines for binding study analysis, and the distribution of these receptors in the central nervous system and in peripheral tissues will be determined. These studies will reveal novel sequences for both ligands and receptors in the species that have been selected for these projects. Receptor sequence and ligand sequence databases will be created to identify amino acid motifs that could be modified in future site directed mutagenesis experiments to address structure/function related questions. These studies may lead to the development of analogs to the ligands (opioids and melanocortins) that may have therapeutic applications. Projects will be conducted by Ph.D. and MS graduate students and undergraduate honors students. Minority students will be recruited for summer REU (NSF Research Experience for Undergraduates) positions. Finally, a molecular cloning project related to this set of studies will be incorporated into the lab techniques course, BIOL 3655 "Molecular Neuroendocrinology" annually. This proposal fits into the area of Biological Systems Informatics in which questions of genome evolution can be addressed using genomic sequence database analyses. This proposal will both add information to a large ligand/receptor sequence database, as well as "data-mine" the database for new insights into receptor/ligand protein evolution and linked gene co-evolution.