title: Evidence of an Antimicrobial Peptide Signature Encrypted in HECT E3 Ubiquitin Ligases.
abstract: The ubiquitin-proteasome pathway (UPP) is a hallmark of the eukaryotic cell. In jawed vertebrates, it has been co-opted by the adaptive immune system, where proteasomal degradation produces endogenous peptides for major histocompatibility complex class I antigen presentation. However, proteolytic products are also necessary for the phylogenetically widespread innate immune system, as they often play a role as host defense peptides (HDPs), pivotal effectors against pathogens. Here, we report the identification of the arachnid HDP oligoventin, which shares homology to a core member of the UPP, E3 ubiquitin ligases. Oligoventin has broad antimicrobial activity and shows strong synergy with lysozymes. Using computational and phylogenetic approaches, we show high conservation of the oligoventin signature in HECT E3s.In silicosimulation of HECT E3s self-proteolysis provides evidence that HDPs can be generated by fine-tuned 26S proteasomal degradation, and therefore are consistent with the hypothesis that oligoventin is a cryptic peptide released by the proteolytic processing of an Nedd4 E3 precursor protein. Finally, we compare the production of HDPs and endogenous antigens from orthologous HECT E3s by proteasomal degradation as a means of analyzing the UPP coupling to metazoan immunity. Our results highlight the functional plasticity of the UPP in innate and adaptive immune systems as a possibly recurrent mechanism to generate functionally diverse peptides.
authors.affiliation: Special Laboratory for Applied Toxinology (LETA), Center of Toxins, Immune-Response and Cell Signaling (CeTICS), Butantan Institute, São Paulo, São Paulo, Brazil; Biosciences Institute, University of São Paulo, São Paulo, São Paulo, Brazil.
authors.forename: Ivan Lavander
authors.initials: IL
authors.lastname: Candido-Ferreira
authors.affiliation: Department of Parasitology, Biomedical Sciences Institute, University of São Paulo , São Paulo, São Paulo , Brazil.
authors.forename: Thales
authors.initials: T
authors.lastname: Kronenberger
authors.affiliation: Special Laboratory for Applied Toxinology (LETA), Center of Toxins, Immune-Response and Cell Signaling (CeTICS), Butantan Institute, São Paulo, São Paulo, Brazil; Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, São Paulo, Brazil.
authors.forename: Raphael Santa Rosa
authors.initials: RS
authors.lastname: Sayegh
authors.affiliation: Laboratory of Biochemistry and Biophysics, Butantan Institute , São Paulo, São Paulo , Brazil.
authors.forename: Isabel de Fátima Correia
authors.initials: IF
authors.lastname: Batista
authors.affiliation: Special Laboratory for Applied Toxinology (LETA), Center of Toxins, Immune-Response and Cell Signaling (CeTICS), Butantan Institute , São Paulo, São Paulo , Brazil.
authors.forename: Pedro Ismael
authors.initials: PI
authors.lastname: da Silva Junior
keywords: HECT ligases; Nedd4; host defense; immune evolution; innate immunity; synergy; ubiquitination; ubiquitin–proteasome system