title: Conformational Analysis of the Host-Defense Peptides Pseudhymenochirin-1Pb and -2Pa and Design of Analogues with Insulin-Releasing Activities and Reduced Toxicities.
abstract: Pseudhymenochirin-1Pb (Ps-1Pb; IKIPSFFRNILKKVGKEAVSLIAGALKQS) and pseudhymenochirin-2Pa (Ps-2Pa; GIFPIFAKLLGKVIKVASSLISKGRTE) are amphibian peptides with broad spectrum antimicrobial activities and cytotoxicity against mammalian cells. In the membrane-mimetic solvent 50% (v/v) trifluoroethanol-H2O, both peptides adopt a well-defined α-helical conformation that extends over almost all the sequence and incorporates a flexible bend. Both peptides significantly (p < 0.05) stimulate the rate of release of insulin from BRIN-BD11 clonal β-cells at concentrations ≥ 0.1 nM but produce loss of integrity of the plasma membrane at concentrations ≥ 1 μM. Increasing cationicity by the substitution Glu(17) → l-Lys in Ps-1Pb and Glu(27) → l-Lys in Ps-2Pa generates analogues with increased cytotoxicity and reduced insulin-releasing potency. In contrast, the analogues [R8r]Ps-1Pb and [K8k,K19k]Ps-2Pa, incorporating d-amino acid residues to destabilize the α-helical domains, retain potent insulin-releasing activity but are nontoxic to BRIN-BD11 cells at concentrations of 3 μM. [R8r]Ps-1Pb produces a significant increase in insulin release rate at 0.3 nM and [K8k,K19k]Ps-2Pa at 0.01 nM. Both analogues show low hemolytic activity (IC50 > 100 μM) but retain broad-spectrum antimicrobial activity and remain cytotoxic to a range of human tumor cell lines, albeit with lower potency than the naturally occurring peptides. These analogues show potential for development into agents for type 2 diabetes therapy.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Manzo
authors.forename: Mariano Andrea
authors.initials: MA
authors.lastname: Scorciapino
authors.affiliation: SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster , Coleraine, BT52 1SA, U.K.
authors.forename: Dinesh
authors.initials: D
authors.lastname: Srinivasan
authors.affiliation: Department of Pharmacology, College of Medicine and Health Sciences, United Arab Emirates University , 17666 Al Ain, United Arab Emirates.
authors.forename: Samir
authors.initials: S
authors.lastname: Attoub
authors.affiliation: Istituto Pasteur-Fondazione Cenci Bolognetti, Department of Biochemical Sciences, Sapienza University of Rome , 5 00185 Rome, Italy.
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Mangoni
authors.forename: Andrea C
authors.initials: AC
authors.lastname: Rinaldi
authors.forename: Mariano
authors.initials: M
authors.lastname: Casu
authors.affiliation: SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster , Coleraine, BT52 1SA, U.K.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Flatt
authors.affiliation: SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster , Coleraine, BT52 1SA, U.K.
authors.forename: J Michael
authors.initials: JM
authors.lastname: Conlon
mesh_terms: D000595:Amino Acid Sequence; D029845:Amphibian Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D045744:Cell Line, Tumor; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy*; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular
chemical_list: D029845:Amphibian Proteins; D023181:Antimicrobial Cationic Peptides; D007328:Insulin; C000603832:pseudhymenochirin-1Pb peptide, Pseudhymenochirus merlini; C000603833:pseudhymenochirin-2Pa peptide, Pseudhymenochirus merlini