Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, 986495 Nebraska Medical Center, Omaha, Nebraska 68198-6495, United States.
Biochemistry. 2012 Jan 17;51(2):653-64. doi: 10.1021/bi2016266. Epub 2012 Jan 6.
LL-23 is a natural peptide corresponding to the 23 N-terminal amino acid residues of human host defense cathelicidin LL-37. LL-23 demonstrated, compared to LL-37, a conserved ability to induce the chemokine MCP-1 in human peripheral blood mononuclear cells, a lack of ability to suppress induction of the pro-inflammatory cytokine TNF-α in response to bacterial lipopolysaccharides (LPS), and reduced antimicrobial activity. Heteronuclear multidimensional nuclear magnetic resonance (NMR) characterization of LL-23 revealed similar secondary structures and backbone dynamics in three membrane-mimetic micelles: SDS, dodecylphosphocholine (DPC), and dioctanoylphosphatidylglycerol. The NMR structure of LL-23 determined in perdeuterated DPC contained a unique serine that segregated the hydrophobic surface of the amphipathic helix into two domains. To improve our understanding, Ser9 of LL-23was changed to either Ala or Val on the basis of homologous primate cathelicidins. These changes made the hydrophobic surface of LL-23 continuous and enhanced antibacterial activity. While identical helical structures did not explain the altered activities, a reduced rate of hydrogen-deuterium exchange from LL-23 to LL-23A9 to LL-23V9 suggested a deeper penetration of LL-23V9 into the interior of the micelles, which correlated with enhanced activities. Moreover, these LL-23 variants had discrete immunomodulatory activities. Both restored the TNF-α dampening activity to the level of LL-37. Furthermore, LL-23A9, like LL-23, maintained superior protective MCP-1 production, while LL-23V9 was strongly immunosuppressive, preventing baseline MCP-1 induction and substantially reducing LPS-stimulated MCP-1 production. Thus, these LL-23 variants, designed on the basis of a structural hot spot, are promising immune modulators that are easier to synthesize and less toxic to mammalian cells than the parent peptide LL-37.
LL-23 是一种天然肽，对应于人防御素 LL-37 的 23 个 N 端氨基酸残基。与 LL-37 相比，LL-23 表现出诱导人外周血单个核细胞趋化因子 MCP-1 的保守能力，缺乏抑制细菌脂多糖（LPS）刺激的促炎细胞因子 TNF-α诱导的能力，并且抗菌活性降低。LL-23 的异核多维核磁共振（NMR）表征在三种膜模拟胶束中显示出相似的二级结构和骨架动力学：SDS、十二烷基磷酸胆碱（DPC）和二油酰基磷脂酰甘油。在氘代 DPC 中确定的 LL-23 的 NMR 结构在疏水区的一个独特丝氨酸将疏水性的两亲螺旋分为两个区域。为了提高我们的理解，根据同源灵长类防御素，将 LL-23 的 Ser9 分别突变为 Ala 或 Val。这些变化使 LL-23 的疏水性表面连续，并增强了抗菌活性。虽然相同的螺旋结构不能解释改变的活性，但从 LL-23 到 LL-23A9 到 LL-23V9 的氢氘交换率降低表明 LL-23V9 更深入地渗透到胶束内部，这与增强的活性相关。此外，这些 LL-23 变体具有离散的免疫调节活性。两者均将 TNF-α 抑制活性恢复到 LL-37 的水平。此外，LL-23A9 与 LL-23 一样，保持了优越的保护性 MCP-1 产生，而 LL-23V9 具有强烈的免疫抑制作用，阻止了基线 MCP-1 的诱导，并大大降低了 LPS 刺激的 MCP-1 产生。因此，这些基于结构热点设计的 LL-23 变体是有前途的免疫调节剂，它们比母肽 LL-37 更容易合成，对哺乳动物细胞的毒性更小。
