Structure-Activity Relationship of RGD-Containing Cyclic Octapeptide and αvβ3 Integrin Allows for Rapid Identification of a New Peptide Antagonist.

Aaron Silva,Yan Wang,Yonghong Zhang,Kit S. Lam,Wenwu Xiao,Heng Wei Chang,Wei Wang,James B. Ames

doi:10.3390/ijms21093076

Abstract

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.

Highlights

IntroductionIntegrin αvβ known as the vitronectin receptor is a member of the integrin superfamily and a heterodimeric transmembrane protein formed by non-covalent association of αv and β3 subunits
Integrin αvβ3 known as the vitronectin receptor is a member of the integrin superfamily and a heterodimeric transmembrane protein formed by non-covalent association of αv and β3 subunits.Each subunit consists of a large extracellular domain, a single transmembrane domain, and a short cytoplasmic domain, through which the integrin modulates bi-directional cell signaling over the plasma membrane [1]
structure–activity relationship (SAR) of LXW-analogous cyclic octapeptides and αvβ3 integrin had been investigated through NMR structure determination and complex modeling

Summary

Introduction

Integrin αvβ known as the vitronectin receptor is a member of the integrin superfamily and a heterodimeric transmembrane protein formed by non-covalent association of αv and β3 subunits. Each subunit consists of a large extracellular domain, a single transmembrane domain, and a short cytoplasmic domain, through which the integrin modulates bi-directional cell signaling over the plasma membrane [1]. As a cell surface receptor of the extracellular matrix (ECM), it binds a wide variety of ECM ligands with RGD motif implicated in many normal and pathological cell functions including cell survival, angiogenesis, tumor invasion, etc. Unlike other integrins ubiquitously expressed in adult tissues, αvβ is most abundantly expressed on angiogenic endothelial cells in pathological tissues [3].

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Discussion

Conclusion