RESUMO

Various biochemical differences exist between mammalian tyrosine aminotransferase (TAT) and its analogue in Trypanosoma cruzi (TcTAT), the causative agent of Chagas disease. Moreover, TcTAT is over-expressed in strains of the parasite that are resistant to benznidazole (BZ), a drug currently used in chemotherapy. TAT has thus been indicated as a potential target for the development of new chemotherapeutic agents. In the present study, the TcTAT gene has been characterised in 14 BZ-resistant and susceptible strains and clones of T. cruzi. A unique transcript of 2.0kb and similar levels of TcTAT mRNA were observed in all parasite populations. TcTAT gene is organized in a tandem multicopy array and is located on 8 chromosomal bands that vary from 785-2500kb. No amplification of TcTAT was observed in the parasite genome. A 42kDa protein expressed by TcTAT was present in all T. cruzi samples. The results suggest that TcTAT is not directly associated with the T. cruzi drug resistance phenotype. However, it may act as a general secondary compensatory mechanism or stress response factor rather than as a key component of the specific primary resistance mechanism in T. cruzi.

Assuntos

Resistência a Medicamentos/genética , Nitroimidazóis/farmacologia , Tripanossomicidas/farmacologia , Trypanosoma cruzi/enzimologia , Trypanosoma cruzi/genética , Tirosina Transaminase/genética , Animais , Northern Blotting , Southern Blotting , Western Blotting , Clonagem Molecular , DNA de Protozoário/análise , Eletroforese em Gel de Campo Pulsado , Regulação Enzimológica da Expressão Gênica/genética , RNA Mensageiro/metabolismo , RNA de Protozoário/análise , Proteínas Recombinantes/genética , Proteínas Recombinantes/imunologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transcrição Gênica , Trypanosoma cruzi/efeitos dos fármacos , Tirosina Transaminase/imunologia