INVESTIGADORES
CARRILLO carolina
congresos y reuniones científicas
Título:
Transgenic T. cruzi expressing an exogenous ornithine decarboxylase gene. Development of drug resistance
Autor/es:
CARRILLO C; HUBER MA; ZADIKIAN C; GONZÁLEZ NS; ALGRANATI ID
Lugar:
Copper Mountain, Colorado, USA
Reunión:
Simposio; Keystone Symposia - Drugs Against Protozoan Parasites: Target Selection, Structural Biology and Medicinal Chemistry.; 2005
Institución organizadora:
Keystone Symposia
Resumen:
T. cruzi differs from other protozoa in many physiological and metabolic characteristics. A key point of trypanosome metabolism is related to polyamines, a group of aliphatic cations, which play essential roles in cellular proliferation and differentiation. The biosynthesis of polyamines in most eukariotic organisms begins with the conversion of ornithine into putrescine catalysed by ornithine decarboxylase (ODC). This rate-limiting enzyme regulates the pathway and its activity is tightly controlled by the cell. There is an alternative route to synthesize putrescine from arginine by arginine decarboxylase (ADC), described mainly in bacteria and plants. We have found that T. cruzi epimastigotes are auxotrophic for polyamines because they lack both ODC and ADC enzymatic activities. Since the genes coding for these enzymes are absent in the parasite genome, we have transformed T. cruzi epimastigotes with an exogenous ODC gene cloned in an appropriate vector. The resulting transgenic T. cruzi expressed high levels of ODC activity becoming autotrophic for polyamines and sensitive to the inhibitor difluoro-methylornithine (DFMO). The presence of this drug for long periods of time in cultures of ODC transformed T. cruzi elicited the selection of DFMO resistant parasites, which showed ODC gene amplification. Restriction analyses of DNA from transgenic T. cruzi either sensitive or resistant to DFMO have demonstrated that exogenous ODC gene was mostly or totally integrated in the parasite genome.