ORF-C4 from the early branching eukaryote Giardia lamblia displays characteristics of α-crystallin small heat shock proteins

CÉSAR G. PRUCCA; MARÍA J. NORES; ELIANA V. ELÍAS; RODRIGO QUIROGA; LUCAS CAVALLÍN; ARGENTA M. PRICE; ALICIA SAURA; PEDRO G. CARRANZA; NATALIA GOTTIG; ALBERTO J. SOLARI; HUGO D. LUJAN

Rosario. Argentina.

Congreso; VIII congreso Argentino de Protozoología y Enfermedades parasitarias. Sociedad Argentina de Protozoología.; 2008

Giardia lamblia is a medically important protozoan parasite with a basal position in the eukaryotic lineage and an interesting model to understand evolution of biochemical events in eukaryotic cells. G. lamblia trophozoites undergo significant changes to survive outside the intestine of their host by differentiating into infective cysts. In this work, we characterize the previously identified gene Orf-C4 (Giardia lamblia open reading frame C4), considered specific of G. lamblia. It encodes a 22 kDa protein that assembles into high molecular mass complexes during the entire life cycle of the parasite. ORF-C4 localizes to the cytoplasm of trophozoites and cysts, and forms large spherical aggregates when overexpressed. ORF-C4 over-expression and down-regulation do not seems to affect trophozoite viability; however, differentiation into cysts is slightly delayed when the expression of ORF-C4 is down-regulated. Moreover, ORF-C4 protein expression is modified under specific stress-inducing conditions. Neither orthologous proteins nor conserved domains are found in databases by conventional sequence analysis of the predicted protein. However, ORF-C4 presents a region structurally similar to the α-crystallin domain of small heat shock proteins. Here, we show the potential role of ORF-C4 as a small chaperone involved in response to stress (including encystation) in G. lamblia.