Allosteric Inhibition of PTP1B by a Nonpolar Terpenoid

Protein
tyrosine phosphatases (PTPs) are promising drug targets
for treating a wide range of diseases such as diabetes, cancer, and
neurological disorders, but their conserved active sites have complicated
the design of selective therapeutics. This study examines the allosteric
inhibition of PTP1B by amorphadiene (AD), a terpenoid hydrocarbon
that is an unusually selective inhibitor. Molecular dynamics (MD)
simulations carried out in this study suggest that AD can stably sample
multiple neighboring sites on the allosterically influential C-terminus
of the catalytic domain. Binding to these sites requires a disordered
α7 helix, which stabilizes the PTP1B–AD complex and may
contribute to the selectivity of AD for PTP1B over TCPTP. Intriguingly,
the binding mode of AD differs from that of the most well-studied
allosteric inhibitor of PTP1B. Indeed, biophysical measurements and
MD simulations indicate that the two molecules can bind simultaneously.
Upon binding, both inhibitors destabilize the α7 helix by disrupting
interactions at the α3−α7 interface and prevent
the formation of hydrogen bonds that facilitate closure of the catalytically
essential WPD loop. These findings indicate that AD is a promising
scaffold for building allosteric inhibitors of PTP1B and illustrate,
more broadly, how unfunctionalized terpenoids can engage in specific
interactions with protein surfaces.

蛋白酪氨酸磷酸酶 (Protein tyrosine phosphatases, PTPs) 是治疗糖尿病、癌症及神经系统疾病等多种病症的极具潜力的药物靶点，但其保守的活性位点给选择性治疗药物的研发带来了极大挑战。本研究针对紫穗槐二烯 (amorphadiene, AD) 对PTP1B的变构抑制 (allosteric inhibition) 作用展开探究，AD是一种具备罕见选择性的萜类烃类抑制剂。本研究开展的分子动力学 (Molecular dynamics, MD) 模拟结果显示，AD可在催化结构域 (catalytic domain) 的变构调控相关C端区域稳定结合多个邻近位点。结合这些位点需要处于无序状态的α7螺旋 (α7 helix)，该螺旋可稳定PTP1B-AD复合物，或有助于AD对PTP1B相较于T细胞蛋白酪氨酸磷酸酶 (T-cell protein tyrosine phosphatase, TCPTP) 的选择性。值得注意的是，AD的结合模式与目前研究最为深入的PTP1B变构抑制剂存在显著差异。进一步的生物物理检测及MD模拟结果证实，这两种抑制剂可同时结合于PTP1B靶点。二者结合后，均可通过破坏α3-α7界面的相互作用使α7螺旋失去稳定性，并阻断催化必需的WPD环 (WPD loop) 闭合所需氢键的形成。本研究结果表明，AD可作为开发PTP1B变构抑制剂的极具潜力的骨架分子；同时也更广泛地揭示了无官能团修饰的萜类化合物如何与蛋白质表面产生特异性相互作用。