title: Imatinib binding to human serum albumin modulates heme association and reactivity.
abstract: 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.
authors: Department of Sciences, Roma Tre University, I-00146 Roma, Italy.
authors: Elena
authors: E
authors: Di Muzio
authors: Department of Sciences, Roma Tre University, I-00146 Roma, Italy; National Institute of Nuclear Physics, Roma Tre Section, I-00146 Roma, Italy.
authors: Fabio
authors: F
authors: Polticelli
authors: Department of Sciences, Roma Tre University, I-00146 Roma, Italy.
authors: Viviana
authors: V
authors: Trezza
authors: Biomedical Research Division, Department of Theoretical and Applied Sciences and Center of Neuroscience, University of Insubria, I-21052 Busto Arsizio, VA, Italy.
authors: Gabriella
authors: G
authors: Fanali
authors: Biomedical Research Division, Department of Theoretical and Applied Sciences and Center of Neuroscience, University of Insubria, I-21052 Busto Arsizio, VA, Italy.
authors: Mauro
authors: M
authors: Fasano
authors: Interdepartmental Laboratory for Electron Microscopy, Roma Tre University, I-00146 Roma, Italy; National Institute of Biostructures and Biosystems, I-00136 Roma, Italy. Electronic address: ascenzi@uniroma3.it.
authors: Paolo
authors: P
authors: Ascenzi
mesh_terms: D001549:Benzamides / Q000378:metabolism* / Q000494:pharmacology; D006418:Heme / Q000378:metabolism*; D006801:Humans; D000068877:Imatinib Mesylate; D007536:Isomerism; D007700:Kinetics; D062105:Molecular Docking Simulation; D030421:Peroxynitrous Acid / Q000737:chemistry; D010879:Piperazines / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding; D011487:Protein Conformation; D047428:Protein Kinase Inhibitors / Q000378:metabolism* / Q000494:pharmacology; D011743:Pyrimidines / Q000378:metabolism* / Q000494:pharmacology; D017384:Sequence Deletion; D012709:Serum Albumin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013816:Thermodynamics
chemical_list: D001549:Benzamides; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D012709:Serum Albumin; D030421:Peroxynitrous Acid; D006418:Heme; D000068877:Imatinib Mesylate
keywords: Allosteric effects; Human serum albumin; Human serum heme-albumin; Imatinib binding; Molecular docking; Peroxynitrite detoxification