Department of Chemical and Geological Sciences, University of Cagliari , Monserrato, Cagliari I-09042, Italy.
Biochemistry. 2013 Oct 15;52(41):7231-41. doi: 10.1021/bi4008287. Epub 2013 Oct 4.
Plasticin-L1 (GLVNGLLSSVLGGGQGGGGLLGGIL) is a conformationally flexible glycine/leucine-rich peptide originally isolated from norepinephrine-stimulated skin secretions of the South-American Santa Fe frog Leptodactylus laticeps (Leptodactylidae). A nuclear magnetic resonance/molecular dynamics characterization of plasticin-L1 in the presence of dodecylphosphocholine (DPC) and DPC/sodium dodecylsulphate micelles as membrane-mimetic models showed that the peptide has affinity for both neutral and anionic membranes. The peptide adopts a stable helical conformation at the N-terminal region and a more disordered helix at the C-terminal region, separated by an unstructured loop wherein the highest number of glycines is localized. In both micelle environments, plasticin-L1 slowly inserts between the detergent head groups but always remains localized at the micelle/water interface. Plasticin-L1 lacks direct antimicrobial activity but stimulates cytokine production by macrophages. Incubation with plasticin-L1 (20 μg/mL) significantly (P < 0.05) increased the production of the proinflammatory cytokines IL-1β, IL-12, IL-23, and TNF-α from unstimulated peritoneal macrophages from both C57BL/6 and BALB/C mice. The peptide also increased IL-6 production by unstimulated (P < 0.01) and lipopolysaccharide-stimulated (P < 0.01) macrophages, whereas the effects on production of the anti-inflammatory cytokine IL-10 were not significant. These findings suggest that plasticin-L1 may play an immunomodulatory role in vivo by stimulating cytokine production from frog skin macrophages in response to microbial pathogens. This peptide may represent a template for the design of peptides with therapeutic applications as immunostimulatory agents.
塑化素-L1(GLVNGLLSSVLGGGQGGGGLLGGIL) 是一种构象灵活的甘氨酸/亮氨酸丰富肽，最初从南美洲 Santa Fe 青蛙 Leptodactylus laticeps（Leptodactylidae）的去甲肾上腺素刺激的皮肤分泌物中分离出来。在十二烷基磷酸胆碱 (DPC) 和 DPC/十二烷基硫酸钠胶束作为膜模拟模型的存在下，对塑化素-L1 的核磁共振/分子动力学特性进行了表征，表明该肽对中性和阴离子膜都有亲和力。该肽在 N 端区域采用稳定的螺旋构象，在 C 端区域采用更无序的螺旋构象，中间由无规卷曲环隔开，其中定位了最多数量的甘氨酸。在两种胶束环境中，塑化素-L1 缓慢插入去污剂头基之间，但始终位于胶束/水界面处。塑化素-L1 没有直接的抗菌活性，但刺激巨噬细胞产生细胞因子。用塑化素-L1（20 μg/mL）孵育可显著（P < 0.05）增加 C57BL/6 和 BALB/C 小鼠未刺激腹腔巨噬细胞中促炎细胞因子 IL-1β、IL-12、IL-23 和 TNF-α 的产生。该肽还增加了未刺激（P < 0.01）和脂多糖刺激（P < 0.01）巨噬细胞中 IL-6 的产生，而对抗炎细胞因子 IL-10 的产生影响不显著。这些发现表明，塑化素-L1 可能通过刺激来自蛙皮巨噬细胞的细胞因子产生来发挥体内免疫调节作用，以应对微生物病原体。该肽可能代表一种模板，可用于设计具有治疗应用的免疫刺激肽。
