RESUMO
Phosphorylation of proteins on tyrosine (Tyr) residues evolved in metazoan organisms as a mechanism of coordinating tissue growth1. Multicellular eukaryotes typically have more than 50 distinct protein Tyr kinases that catalyse the phosphorylation of thousands of Tyr residues throughout the proteome1-3. How a given Tyr kinase can phosphorylate a specific subset of proteins at unique Tyr sites is only partially understood4-7. Here we used combinatorial peptide arrays to profile the substrate sequence specificity of all human Tyr kinases. Globally, the Tyr kinases demonstrate considerable diversity in optimal patterns of residues surrounding the site of phosphorylation, revealing the functional organization of the human Tyr kinome by substrate motif preference. Using this information, Tyr kinases that are most compatible with phosphorylating any Tyr site can be identified. Analysis of mass spectrometry phosphoproteomic datasets using this compendium of kinase specificities accurately identifies specific Tyr kinases that are dysregulated in cells after stimulation with growth factors, treatment with anti-cancer drugs or expression of oncogenic variants. Furthermore, the topology of known Tyr signalling networks naturally emerged from a comparison of the sequence specificities of the Tyr kinases and the SH2 phosphotyrosine (pTyr)-binding domains. Finally we show that the intrinsic substrate specificity of Tyr kinases has remained fundamentally unchanged from worms to humans, suggesting that the fidelity between Tyr kinases and their protein substrate sequences has been maintained across hundreds of millions of years of evolution.
Assuntos
Fosfotirosina , Proteínas Tirosina Quinases , Especificidade por Substrato , Tirosina , Animais , Humanos , Motivos de Aminoácidos , Evolução Molecular , Espectrometria de Massas , Fosfoproteínas/química , Fosfoproteínas/metabolismo , Fosforilação , Fosfotirosina/metabolismo , Proteínas Tirosina Quinases/efeitos dos fármacos , Proteínas Tirosina Quinases/metabolismo , Proteoma/química , Proteoma/metabolismo , Proteômica , Transdução de Sinais , Domínios de Homologia de src , Tirosina/metabolismo , Tirosina/químicaRESUMO
O efeito do aluminio foi avaliado em plaquetas humanas de individuos clinicamente saudaveis atraves de estudos de agregacao, peroxidacao e fosforilacao de proteinas em residuo de tirosina com os inibidores plaquetarios "in vitro" (Trolox, AAS, NDGA, EDTA E DFO). Os resultados obtidos demonstraram que o aluminio foi capaz de promover peroxidacao lipidica com ativacao de proteina tirosina quinase (PTK) e agregacao plaquetaria. A ativacao plaquetaria pelo aluminio independe da formacao de metabolitos do acido araquidonico via ciclooxigenase. por outro lado, os eventos de agregacao e fosforilacao de PTK foram dependentes de peroxidacao enzimatica mediada preferencialmente por hidrolise de acido araquidonico, via ativacao de lipoxigenases