Di Muzio Elena, Polticelli Fabio, Trezza Viviana, Fanali Gabriella, Fasano Mauro, Ascenzi Paolo
Department of Sciences, Roma Tre University, I-00146 Roma, Italy.
Department of Sciences, Roma Tre University, I-00146 Roma, Italy; National Institute of Nuclear Physics, Roma Tre Section, I-00146 Roma, Italy.
Arch Biochem Biophys. 2014 Oct 15;560:100-12. doi: 10.1016/j.abb.2014.07.001. Epub 2014 Jul 21.
Imatinib, an inhibitor of the Bcr-Abl tyrosine kinase, is approximately 95% bound to plasma proteins, α1-acid glycoprotein (AGP) being the primary carrier. However, human serum albumin (HSA) may represent the secondary carrier of imatinib in pathological states characterized by low AGP levels, such as pancreatic cancer, hepatic cirrhosis, hepatitis, hyperthyroidism, nephrotic syndrome, malnutrition, and cachexia. Here, thermodynamics of imatinib binding to full-length HSA and its recombinant Asp1-Glu382 truncated form (containing only the FA1, FA2, FA6, and FA7 binding sites; trHSA), in the absence and presence of ferric heme (heme-Fe(III)), and the thermodynamics of heme-Fe(III) binding to HSA and trHSA, in the absence and presence of imatinib, has been investigated. Moreover, the effect of imatinib on kinetics of peroxynitrite detoxification by ferric human serum heme-albumin (HSA-heme-Fe(III)) and ferric truncated human serum heme-albumin (trHSA-heme-Fe(III)) has been explored. All data were obtained at pH 7.0, and 20.0 °C and 37.0 °C. Imatinib binding to the FA7 site of HSA and trHSA inhibits allosterically heme-Fe(III) association to the FA1 site and vice versa, according to linked functions. Moreover, imatinib binding to the secondary FA2 site of HSA-heme-Fe(III) inhibits allosterically peroxynitrite detoxification. Docking simulations and local structural comparison with other imatinib-binding proteins support functional data indicating the preferential binding of imatinib to the FA1 and FA7 sites of HSA, and to the FA2 and FA7 sites of HSA-heme-Fe(III). Present results highlight the allosteric coupling of the FA1, FA2, and FA7 sites of HSA, and may be relevant in modulating ligand binding and reactivity properties of HSA in vivo.
伊马替尼是一种Bcr - Abl酪氨酸激酶抑制剂，约95%与血浆蛋白结合，α1 - 酸性糖蛋白（AGP）是主要载体。然而，在AGP水平较低的病理状态下，如胰腺癌、肝硬化、肝炎、甲状腺功能亢进、肾病综合征、营养不良和恶病质，人血清白蛋白（HSA）可能是伊马替尼的次要载体。在此，研究了在有无高铁血红素（血红素 - Fe(III)）存在的情况下，伊马替尼与全长HSA及其重组Asp1 - Glu382截短形式（仅包含FA1、FA2、FA6和FA7结合位点；trHSA）的结合热力学，以及在有无伊马替尼存在的情况下，血红素 - Fe(III)与HSA和trHSA的结合热力学。此外，还探讨了伊马替尼对高铁人血清血红素白蛋白（HSA - 血红素 - Fe(III)）和高铁截短人血清血红素白蛋白（trHSA - 血红素 - Fe(III)）对过氧亚硝酸盐解毒动力学的影响。所有数据均在pH 7.0、20.0°C和37.0°C条件下获得。根据连锁函数，伊马替尼与HSA和trHSA的FA7位点结合会变构抑制血红素 - Fe(III)与FA1位点的结合，反之亦然。此外，伊马替尼与HSA - 血红素 - Fe(III)的次要FA2位点结合会变构抑制过氧亚硝酸盐解毒。对接模拟以及与其他伊马替尼结合蛋白的局部结构比较支持了功能数据，表明伊马替尼优先结合HSA的FA1和FA7位点，以及HSA - 血红素 - Fe(III)的FA2和FA7位点。目前的结果突出了HSA的FA1、FA2和FA7位点的变构偶联，可能与体内调节HSA的配体结合和反应特性有关。
