COMPARATIVE STUDIES OF TRYPANOSOME RECEPTOR FOR ACTIVATED PROTEIN KINASE C (TRACK)

B. NYAMBEGA; M. JURI AYUB; D. MASIGA; M. LEVIN

Huerta Grande, Córdoba

Congreso; XXI Reunion Anual de la Sociedad Argentina de Protozoología; 2006

In contrast with eukaryotic cells where complex interacting signaling networks have been described, a simple pathway is yet to be identified in trypanosomes. We have recently conducted preliminary studies on the trypanosome anchor protein, the Receptor for Activated Protein Kinase C previously shown to regulate a range of cellular activities including cell growth, cytokinesis and translation (Rothberg et al., 2005). Here, we report studies on characterization of TRACK 1 from pathogenic Trypanosoma brucei and Trypanosoma cruzi, the causative agents of African and American trypanosomiases respectively.   Contrary to previous Cryo-EM assays showing the absence of T. cruzi RACK (TcRACK) on the 40S density maps (Gao et al., 2005), our studies reveal the presence of T. brucei RACK (TbRACK) strategically poised near the messenger RNA exit channel.  In addition, Western blot analysis using anti-TRACK on purified trypanosome ribosomes reveals the presence of both TbRACK and TcRACK on the 80S ribosome.  In yeast, arginine 38 and lysine 40 were vital for attachment to the ribosome, mutation of these amino acids abolished binding. The replacement of lysine at position 40 with asparagine in TcRACK could be responsible for weak binding and subsequent fall-off during Cryo-EM assays, and hence the ‘absence’ of TcRACK on the density maps. Over-expression of pTREX-TbRACK and pTREX-TcRACK in T. cruzi led to growth arrest and parasite death. This is with agreement to previous observations in T. brucei (Mathews et al.; Welburn et al., 1998). Put together these preliminary studies support the involvement of TRACK in mRNA translation and apoptotic pathways. Supported by SSI/TDR, FONCYT and CONICET.