甲状腺激素(TH),T4和T3通过结合膜受体αvβ3整联蛋白介导癌细胞中的促有丝分裂作用。脱氨基类似物四合有效阻断TH与该受体的结合并阻止其作用。虽然有关TH与αvβ3整联蛋白结合的计算数据已发表,缺乏对其他TH代谢物的全面分析。
26种TH代谢物的硅对接,包括生物活性甲状腺激素(T3和T4)和一系列硫酸盐,脱碘,脱氨基或脱羧代谢物,基于整联蛋白的晶体结构的三维表示,使用DOCK6对αvβ3受体结合袋进行。由于整合素上的TH结合位点与明确定义的RGD结合位点非常接近,线性和环状RGD作为参考。使用网格评分和琥珀色评分以及距离可移动区域方案计算每个受体-配体复合物的结合能。
所有TH分子都表现出负自由能,提示对αvβ3整合素的亲和力。值得注意的是,基于Grid和Amber评分的3,3'T2(3,3'T2S)和T4(T4S)的硫酸化形式显示出对整联蛋白的最高结合亲和力,与环状RGD和一系列检查的TH代谢物相比。主要的甲状腺激素,T3和T4对整合素显示出高亲和力,优于线性RGD。对于所有激素代谢物,脱羧导致亲和力降低。这对应于观察到羧基通过金属离子依赖性粘附(MIDAS)基序位点处的二价阳离子介导与整联蛋白口袋的结合。对于T3(三端双向可控硅)和T4(四端双向可控硅)的脱氨基形式,记录了类似的降低的亲和力。最后,T3,T3S,和T3AM显示出较高的琥珀分数相对于他们的原生形式,表明与位置5'相比,位置5处的碘化与增加的结合亲和力相关。
各种TH代谢物的三维对接揭示了αvβ3整联蛋白的微分计算自由能的结构基础。这些发现可能表明,天然存在的内源性TH代谢物可能会影响生理和癌症中整合素介导的细胞内途径。
Thyroid hormones (TH), T4 and T3, mediate pro-mitogenic effects in cancer cells through binding the membrane receptor αvβ3 integrin. The deaminated analogue tetrac effectively blocks TH binding to this receptor and prevents their action. While computational data on TH binding to the αvβ3 integrin was published, a comprehensive analysis of additional TH metabolites is lacking.
In-silico docking of 26 TH metabolites, including the biologically active thyroid hormones (T3 and T4) and an array of sulfated, deiodinated, deaminated or decarboxylated metabolites, to the αvβ3 receptor binding pocket was performed using DOCK6, based on the three-dimensional representation of the crystallographic structure of the integrin. As the TH binding site upon the integrin is at close proximity to the well-defined RGD binding site, linear and cyclic RGD were included as a reference. Binding energy was calculated for each receptor-ligand complex using Grid score and Amber score with distance movable region protocol.
All TH molecules demonstrated negative free energy, suggesting affinity to the αvβ3 integrin. Notably, based on both Grid and Amber scores sulfated forms of 3,3\' T2 (3,3\' T2S) and T4 (T4S) demonstrated the highest binding affinity to the integrin, compared to both cyclic RGD and an array of examined TH metabolites. The major thyroid hormones, T3 and T4, showed high affinity to the integrin, which was superior to that of linear RGD. For all hormone metabolites, decarboxylation led to decreased affinity. This corresponds with the observation that the carboxylic group mediates binding to the integrin pocket via divalent cations at the metal-ion-dependent adhesion (MIDAS) motif site. A similar reduced affinity was documented for deaminated forms of T3 (triac) and T4 (tetrac). Lastly, the reverse forms of T3, T3S, and T3AM showed higher Amber scores relative to their native form, indicating that iodination at position 5 is associated with increased binding affinity compared to position 5\'.
Three-dimensional docking of various TH metabolites uncovered a structural basis for a differential computational free energy to the αvβ3 integrin. These findings may suggest that naturally occurring endogenous TH metabolites may impact integrin-mediate intracellular pathways in physiology and cancer.