The NMR Structure of Human Obestatin in Membrane-Like Environments: Insights into the Structure-Bioactivity Relationship of Obestatin

The quest for therapeutic applications of obestatin involves, as a first step, the determination of its 3D solution structure and the relationship between this structure and the biological activity of obestatin. On this basis, we have employed a combination of circular dichroism (CD), nuclear magnetic resonance (NMR) spectroscopy, and modeling techniques to determine the solution structure of human obestatin (1). Other analogues, including human non-amidated obestatin (2) and the fragment peptides (6–23)-obestatin (3), (11–23)-obestatin (4), and (16–23)-obestatin (5) have also been scrutinized. These studies have been performed in a micellar environment to mimic the cell membrane (sodium dodecyl sulfate, SDS). Furthermore, structural-activity relationship studies have been performed by assessing the in vitro proliferative capabilities of these peptides in the human retinal pigmented epithelial cell line ARPE-19 (ERK1/2 and Akt phosphorylation, Ki67 expression, and cellular proliferation). Our findings emphasize the importance of both the primary structure (composition and size) and particular segments of the obestatin molecule that posses significant α-helical characteristics. Additionally, details of a species-specific role for obestatin have also been hypothesized by comparing human and mouse obestatins (1 and 6, respectively) at both the structural and bioactivity levels.

针对肥胖抑制素（obestatin）治疗应用的探索，首要步骤在于解析其三维溶液结构，并阐明该结构与肥胖抑制素生物学活性之间的关联。基于此，我们结合圆二色谱（circular dichroism, CD）、核磁共振波谱（nuclear magnetic resonance, NMR）与建模技术，解析了人源肥胖抑制素（1）的溶液结构。此外，我们还对其他类似物展开了细致研究，包括人源未酰胺化肥胖抑制素（2）以及片段肽（6–23）-肥胖抑制素（3）、（11–23）-肥胖抑制素（4）与（16–23）-肥胖抑制素（5）。本研究在模拟细胞膜的胶束环境（十二烷基硫酸钠，SDS）中完成。此外，我们通过在人源视网膜色素上皮细胞系ARPE-19中评估这些肽的体外增殖能力（检测指标包括ERK1/2与Akt磷酸化水平、Ki67表达量及细胞增殖活性），开展了结构-活性关系研究。本研究结果证实，肥胖抑制素分子的一级结构（组成与长度）以及具备显著α-螺旋特征的特定结构域，均发挥着关键作用。此外，我们通过分别在结构与生物活性层面比较人源与鼠源肥胖抑制素（分别对应样本1与6），还推测了肥胖抑制素的物种特异性作用细节。