title: Molecular evolution of the NF-kappaB signaling system.
abstract: The mechanisms of innate immunity in vertebrates show certain overall resemblances to immune mechanisms of insects. Two hypotheses have been proposed to explain these resemblances. (1) According to the evolutionary continuity hypothesis, innate immune mechanisms evolved in the common ancestor of vertebrates and insects and have been conserved since that time. (2) In the independent-evolution hypothesis, the mechanisms of innate immunity in vertebrates evolved independently from invertebrate immune mechanisms. Phylogenetic analysis of five gene families (Pelle, Rel, IkappaB, Toll, and TRAF) whose members are involved in NF-kappaB signaling in vertebrates and insects were used to decide between these hypotheses. The phylogenies of the Rel and TRAF families strongly supported independent evolution of immune functions in vertebrates and invertebrates, and, except for a possible case in the Pelle family, orthologous molecules having immune functions in both vertebrates and invertebrates were not found. The results suggest that NF-kappaB represents an ancient, generalized signaling system that has been co-opted for immune system roles independently in vertebrate and insect lineages.
authors.affiliation: Department of Biological Sciences, University of South Carolina, Coker Life Sciences Bldg., 700 Sumter St., Columbia, SC 29208, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Friedman
authors.forename: Austin L
authors.initials: AL
authors.lastname: Hughes
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D029721:Drosophila Proteins; D019143:Evolution, Molecular; D006801:Humans; D007107:Immune System / Q000378:metabolism*; D008562:Membrane Glycoproteins; D016328:NF-kappa B / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D010802:Phylogeny; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020569:Proto-Oncogene Proteins c-rel / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011971:Receptors, Immunologic; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D047990:TNF Receptor-Associated Factor 1; D051193:Toll-Like Receptors
chemical_list: D029721:Drosophila Proteins; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D011506:Proteins; D020569:Proto-Oncogene Proteins c-rel; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D047990:TNF Receptor-Associated Factor 1; D051193:Toll-Like Receptors; C079896:pll protein, Drosophila; D017346:Protein Serine-Threonine Kinases