Short host-defence peptides from frog skin

Gene-encoded antimicrobial peptides (AMPs) are key components of the innate immune response of all pluricellular organisms, providing them with the first-line defence against pathogens [1-4]. Amphibian skin secretions represent one of the richest natural sources for such molecules, which are synthesized and stored within granules of holocrine-type serous glands and released upon stimulation [5-7].We are studying two major groups, temporins and bombinins H. Temporins constitute a large family of AMPs (more than 40 members) isolated from the skin of the genus Rana, and are among the smallest amphipathic a-helical peptides (10-14 residues) found in nature to date, and with the lowest number of positively charged amino acids [8,9]. Interestingly, some temporins (A, B and L) do possess attractive and unique properties that make them promising candidates for the future design of anti-infective agents with new modes of action, urgently needed due to the increasing resistance of microorganisms to the available drugs. These properties include: (i) a fast membranolytic effect against a large spectrum of pathogens (bacteria, fungi and protozoa of Leishmania genus including both the insect and the mammalian stages of the parasite) [10,11]; (ii) preservation of biological activity in serum and in physiological salt concentration [11]; (iii) chemotactive activities on human phagocytes; (iv) synergistic action when combined with conventional antibiotics [12]; (v) in vivo efficacy in preventing prosthetic graft infections and lethality in rat models of septic shock. The second interesting family of AMPs refers to bombinins H, isolated from amphibia of Bombina genus [13] and containing isomers with a single D-amino acid which results from a post-traslational modification. By studying these peptides [14],we have demonstrated the importance of a single L- to D epimerization as a new approach developed by nature to modulate not only the bio-availability (e.g. higher solubility) and biostability (i.e. protection from proteolytic degradation) of these molecules, but also their biophysical properties (peptide structure and organization within membranes) and antimicrobial activities [15]. REFERENCES [1] Boman H.G. Peptide antibiotics and their role in innate immunity. Annu. Rev. Immunol. 1995; 13:61-92. [2] Kimbrell D.A. and Beutler B. The evolution and genetics of innate immunity. Nat. Rev. Genet. 2001; 2:256-267. [3] Ganz T. Defensins: antimicrobial peptides of innate immunity. Nat. Rev. Immunol. 2003; 3:710-720. [4] Selsted M.E. and Ouellette A.J. Mammalian defensins in the antimicrobial immune response. Nat. Immunol. 2005; 6:551-557. [5] Barra, D., and Simmaco, M. Amphibian skin: a promising resource for antimicrobial peptides, Trends Biotechnol. 1995; 13: 205-209. [6] Bevins, C. L., and Zasloff, M. Peptides from frog skin, Annu. Rev. Biochem. 1990; 59:395-414. [7] Mangoni, M. L., Miele, R., Renda, T. G., Barra, D., and Simmaco, M. The synthesis of antimicrobial peptides in the skin of Rana esculenta is stimulated by microorganisms, FASEB J. 2001; 15:1431-1432. [8] Simmaco M., Mignogna G., Canofeni S., Miele R., Mangoni M.L., Barra D. Temporins, antimicrobial peptides from the European red frog Rana temporaria. Eur. J. Biochem. 1996; 242:788-792. [9] Conlon J.M., Kolodziejek J. and Nowotny N. Antimicrobial peptides from ranid frogs: taxonomic and phylogenetic markers and a potential source of new therapeutic agents. Biochim. Biophys. Acta 2004;1696: 1-14. [10] Mangoni M.L., Papo N., Barra D., Simmaco M., Bozzi A., Di Giulio A., Rinaldi AC. Effects of the antimicrobial peptide temporin L on cell morphology, membrane permeability and viability of Escherichia coli. Biochem. J. 2004; 380:859-865. [11] Mangoni, M. L., Saugar, J. M., Dellisanti, M., Barra, D., Simmaco, M., Rivas, L. Temporins, small antimicrobial peptides with leishmanicidal activity, J. Biol. Chem. 2005; 280:984-990. [12] Mangoni M.L., Rinaldi A.C., Di Giulio A., Mignogna G., Bozzi A., Barra D. Simmaco M. Structure-function relationships of temporins, small antimicrobial peptides from amphibian skin. Eur. J. Biochem. 2000; 267: 1447-1454. [13] Mignogna, G., Simmaco, M., Kreil, G., Barra, D. Antibacterial and haemolytic peptides containing D-alloisoleucine from the skin of Bombina variegata, EMBO J. 1993; 12: 4829-4832. [14] Mangoni, M. L., Grovale, N., Giorgi, A., Mignogna, G., Simmaco, M., Barra, D. Structure-function relationships in bombinins H, antimicrobial peptides from Bombina skin secretions, Peptides 2000; 21: 1673-1679. [15] Mangoni M.L., Papo N., Saugar J.M., Barra D., Shai Y., Simmaco M., Rivas R. Biochemistry. 2006; in press