The heat-shock response in Trypanosoma cruzi.
When Trypanosoma cruzi epimastigotes are exposed to temperatures of 37-41 degrees C there is a drastic decline in total protein synthesis. Analysis of the proteins synthesized at 41 degrees C by one-dimensional gel electrophoresis showed three major bands of Mr 83,000, 70,000 and 60,000. A similar pattern of heat-shock proteins was found in two different strains of T. cruzi (Tulahuen and GM strains) and in exponentially growing or in stationary epimastigotes. Actinomycin D prevented the appearance of these polypeptide bands, suggesting that the heat-shock proteins in T. cruzi epimastigotes are induced at the level of transcription. Analysis of the proteins synthesized by metacyclic forms at different temperatures suggests that heat-shock proteins in these cells are already synthesized at 27 degrees C. Elevation of temperature above 37 degrees C blocks the synthesis of most proteins in metacyclic forms except for major bands of Mr 83,000, 70,000, 60,000 and 55,000. More detailed analyses by high-resolution two-dimensional gel electrophoresis of the proteins synthesized at 27 degrees C or 37 degrees C by epimastigotes indicates that the heat-shock protein pattern is more complex than that demonstrated by one dimension, and at least ten new polypeptides are identified in two-dimensional gels. A similar analysis of metacyclic forms shows that most if not all the proteins present at 39 degrees C are also present at 27 degrees C. This result led us to the suggestion that the differentiation of T. cruzi to metacyclic forms involves the induction of heat-shock proteins, which prepares the parasite to infect the mammalian host.
Alcina
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A
Departamento de Microbiologia, Universidad Autonoma, Madrid, Spain.
Urzainqui
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A
Carrasco
L
L
D000818:Animals; D003609:Dactinomycin / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D006360:Heat-Shock Proteins / Q000032:analysis / Q000096:biosynthesis*; D006358:Hot Temperature; D013045:Species Specificity; D014349:Trypanosoma cruzi / Q000254:growth & development / Q000378:metabolism*
D006360:Heat-Shock Proteins; D003609:Dactinomycin