Department of Chemistry, The University of Texas Rio Grande Valley, Edinburg, TX 78539, USA.
Department of Biochemistry and Molecular Medicine, University of California, Davis Cancer Center, Sacramento, CA 95616, USA.
Int J Mol Sci. 2020 Apr 27;21(9):3076. doi: 10.3390/ijms21093076.
The αvβ3 integrin, a receptor for many extracellular matrix proteins with RGD-sequence motif, is involved in multiple physiological processes and highly expressed in tumor cells, therefore making it a target for cancer therapy and tumor imaging. Several RGD-containing cyclic octapeptide (named LXW analogs) were screened as αvβ3 antagonists with dramatically different binding affinity, and their structure-activity relationship (SAR) remains elusive. We performed systematic SAR studies and optimized LXW analogs to improve antagonistic potency. The NMR structure of LXW64 was determined and docked to the integrin. Structural comparison and docking studies suggested that the hydrophobicity and aromaticity of the X7 amino acid are highly important for LXW analogs binding to the integrin, a potential hydrophobic pocket on the integrin surface was proposed to play a role in stabilizing the peptide binding. To develop a cost-efficient and fast screening method, computational docking was performed on LXW analogs and compared with in vitro screening. A consistency within the results of both methods was found, leading to the continuous optimization and testing of LXW mutants via in silico screening. Several new LXW analogs were predicted as the integrin antagonists, one of which-LXZ2-was validated by in vitro examination. Our study provides new insight into the RGD recognition specificity and valuable clues for rational design of novel αvβ3 antagonists.
αvβ3 整联蛋白是一种细胞外基质蛋白受体，具有 RGD 序列基序，参与多种生理过程，在肿瘤细胞中高度表达，因此成为癌症治疗和肿瘤成像的靶点。已经筛选出几种含有 RGD 的环八肽（命名为 LXW 类似物）作为αvβ3 拮抗剂，它们具有显著不同的结合亲和力，但其结构-活性关系（SAR）仍然难以捉摸。我们进行了系统的 SAR 研究，并对 LXW 类似物进行了优化，以提高拮抗活性。确定了 LXW64 的 NMR 结构，并将其对接至整合素。结构比较和对接研究表明，X7 氨基酸的疏水性和芳香性对 LXW 类似物与整合素的结合至关重要，整合素表面可能存在一个潜在的疏水性口袋，在稳定肽结合中起作用。为了开发一种经济高效且快速的筛选方法，我们对 LXW 类似物进行了计算对接，并与体外筛选进行了比较。两种方法的结果具有一致性，从而通过计算机筛选不断优化和测试 LXW 突变体。预测了几种新的 LXW 类似物作为整合素拮抗剂，其中一种 LXZ2 通过体外检测得到验证。我们的研究为 RGD 识别特异性提供了新的见解，并为新型αvβ3 拮抗剂的合理设计提供了有价值的线索。
