Characterization and stage-specific expression analysis of members of Toxoplasma gondii a-crystallin/sHsp family

DE MIGUEL, N; ECHEVERRIA, PC; ANGEL,SO

Francia

Congreso; Eighth International Congress on Toxoplasmosis; 2005

The small heat shock proteins (sHSPs) are a diverse group of stress-inducible proteins characterized by a monomer size ranges between 15-30 kDa, a conserved region (similar to a-crystallin domain) of approximately 90 amino acid residues in the C-terminal and a more variable sequence in the N-terminal region of these proteins. The number of sHsps in differents species is highly variable. Cell-specific expression of sHsps in the absence of stress has been reported during the development of a wide range of organism. Their particular cell-specific pattern of expression has lead to the hypothesis that sHsp may be implicated in differentiation mechanisms. Convertion from tachyzoite  to bradyzoite stage in T. gondii can be induced by stress factors. Until now, only one sHsp have been described (BAG1) which is mainly expressed in bradyzoite stage. The main goal of this work was to identify and characterize the parasite a-crystallin/sHSP family, in order to know the role of these proteins in the process of stage convertion of T.gondii. Four differents sHsps called Hsp20, Hsp21, Hsp28, Hsp29, were identified by in silico analysis at www.toxodb.org page and cloned using RT-PCR. A phylogenetic analysis was performed based on the conserved C-terminal aminoacidic sequence of the predicted proteins. The T. gondii  sHsps branched in two groups, one containing the Hsp20, Hsp21, Hsp29 and Hsp30 forming a group with others apicomplexan sHsps; and the Hsp28 that is grouped with the plants sHsps. Differential expression of these genes in tachyzoite and bradyzoite stage were analyzed by RT-PCR. Hsp 20, Hsp21, and Hsp29 were presented in both stages of the parasite. On the other hand, Hsp28 was only detected in tachyzoite stage and Hsp30/Bag1 in bradyzoite stage. This work describes for first time the presence of at least five sHsps in T. gondii. The phylogenetic analysis and the expression in tachyzoite/bradyzoite stages shown that Hsp28 has a unique characteristics, and could be implicated in differentiation mechanisms of T.gondii.