Physiological aspects of Trypanosoma cruzi gene regulation during heat-shock

Investigations on the conditions of heat-shock response in Trypanosoma cruzi, the agent of Chagas disease, showed that at 37 degrees C, one of the heat-shock temperatures employed, the parasites from 48 h culture do not display a classical response to the heat treatment, since a general increase in RNA and protein synthesis was detected. The classical heat-shock response was detected only at 40 degrees C. The data also suggest that the heat shock proteins (HSP) mRNA population is sufficient to maintain protein synthesis at a high rate for at least 1 h and, to maintain the same rate of response for a longer period, transcription is necessary. The half life of HSP 70 mRNA is less than 3 h at 37 degrees C. The protein synthesized during the first hour of the heat shock at 37 degrees C is stable for at least 24 h. The parasite seems to be able to reuse the stock of HSP mRNAs stored during the first thermal shock to respond to a second heat treatment. These data are discussed bearing in mind other cell types

The heat-shock response in Trypanosoma cruzi and Crithidia fasciculata

Molecular aspects of heat-shock response were investigated in monogenetic and digenetic members of the Trypanosomatidae and the data obtained compared. Trypanosoma cruzi and Crithidia fasciculata differ in the number of heat-shock proteins (HSPs) induced and in the range of supra-optimal temperature induction of these proteins. Whereas low molecular weight Hsps were induced by high temperature in Crithidia, this effect was only seen in T. cruzi after ethanol treatment. The 61 kDa peptide of T. cruzi, induced by heat, was characterized as a HSP60 family member by Western blot using a Mycobacterium polyclonal anti-HSP60 antibody. The HSP61 aa. sequence, deduced from the isolated HSP60 gene and its mRNA product were characterized. The predicted aa. sequence has shown the presence of a mitochondrial peptide leader and no large domains of aa. sequence conservation were found when compared to other known HSP60, in contrast to what is observed in HSP70. Furthermore, the HSP60 gene is apparently conserved in T. cruzi, C. fascilulata and Leishmania as suggested by genomic Southern blot analysis.