Substrate specificity and possible functions of the metacaspases of Trypanosoma cruzi

MARC LAVERRIERE; JUAN J. CAZZULO; VANINA E. ALVAREZ

San Miguel de Tucumán, Tucumán

Congreso; XLV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB 2009); 2009

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular.

Metacaspases (MCAs) are distant caspase relatives present in plants, fungi and protozoa, but absent in animals. We have previously determined the catalytic properties of two MCA gene products (TcMCA3 and TcMCA5) in T. cruzi. TcMCAs are cysteine peptidases that need an intact His-Cys catalytic dyad but at variance with caspases are enzymatically active without proteolytic processing and display substrate specificity for Arg at P1. We used the tetracycline inducible vector pTcINDEX to generate cell lines overexpressing TcMCA3, TcMCA5 and their corresponding active site mutants in order to determine if they produce any effects in the different stages of the parasite: epimastigote, trypomastigote and amastigote. Overexpression of TcMCA3, but not its active site mutant, impairs epimastigote growth. By Flow cytometry analysis of a synchronized epimastigote culture overexpressing TcMCA3, we showed an arrest in cell cycle progression at the G1/S transition. Overexpression of TcMCA3 in the parasite mammalian stages also suggests alteration of the parasite life cycle in the Vero cell model. Overexpression of TcMCA5, on the other hand, did not cause similar effects. Thus, our results suggest that metacaspases, although differing from classical caspases in their biochemical properties, might share some of their possible functions in apoptosis, progression of the cell cycle and differentiation.