Purification, Conformational Analysis, and Properties of a Family of Tigerinin Peptides from Skin Secretions of the Crowned Bullfrog Hoplobatrachus occipitalis

摘要

Four host-defense peptides belonging to the tigerinin family (tigerinin-10: RICTPIPFPMCY; tigerinin-20: RTCIPIPLVMC; tigerinin-30: RICTAIPLPMCL; and tigerinin-40: RTCIPIPPVCF) were isolated from skin secretions of the African crowned bullfrog Hoplobatrachus occipitalis. In aqueous solution at pH 4.8, the cyclic domain of tigerinin-20 adopts a rigid amphipathic conformation that incorporates a flexible N-terminal tail. The tigerinins lacked antimicrobial (MIC > 100 mu M) and hemolytic (LC50 > 500 mu M) activities but, at a concentration of 20 mu g/mL, significantly (P 0.05) inhibited production of interferon-gamma (IFN-gamma) by peritoneal cells from CS7BL/6 mice without affecting production of IL-10 and IL-17. Tigerinin-20 and -40 inhibited IFN-gamma production at concentrations as low as 1 mu g/mL. The tigerinins significantly (P = 0.05) stimulated the rate of insulin release from BRIN-BD11 clonal beta-cells without compromising the integrity of the plasma membrane. Tigerinin-10 was the most potent (threshold concentration 1 nM) and the most effective (395% increase over basal rate at a concentration of 1 mu M). Tigerinin-40 was the most potent and effective peptide in stimulating the rate of glucagon-like peptide-1 release from GLUTag enteroendocrine cells (threshold concentration 10 nM; 289% increase over basal rate at 1 mu M). Tigerinin peptides have potential for development into agents for the treatment of patients with type 2 diabetes.