Mining the Giardia genome and proteome for conserved and unique basal body proteins

Abstract

Giardia lamblia is a flagellated protozoan parasite and a major cause of diarrhea in humans. Its microtubular cytoskeleton mediates trophozoite motility, attachment and cytokinesis, and is characterized by an attachment disk and eight flagella that are each nucleated in a basal body. To date, only 10 giardial basal body proteins have been identified, including universal signaling proteins that are important for regulating mitosis or differentiation. In this study, we have exploited bioinformatics and proteomic approaches to identify new Giardia basal body proteins and confocal microscopy to confirm their localization in interphase trophozoites. This approach identified 75 homologs of conserved basal body proteins in the genome including 65 not previously known to be associated with Giardia basal bodies. Thirteen proteins were confirmed to co-localize with centrin to the Giardia basal bodies. We also demonstrate that most basal body proteins localize to additional cytoskeletal structures in interphase trophozoites. This might help to explain the roles of the four pairs of flagella and Giardia-specific organelles in motility and differentiation. A deeper understanding of the composition of the Giardia basal bodies will contribute insights into the complex signaling pathways that regulate its unique cytoskeleton and the biological divergence of these conserved organelles.

FOR20, a conserved centrosomal protein, is required for assembly of the transition zone and basal body docking at the cell surface

“…A similar localisation at the tip of the basal bodies was described both in Tetrahymena by electron microscopy for the homologous protein called Bbc20 (Kilburn et al, 2007) and in mouse trachea epithelia by immunofluorescence (Sedjaï et al, 2010). In Giardia, a protein homologous to Bbc20/FOR20 is detected along the intracytoplasmic part of axonemes, suggesting an interaction with microtubule doublets (Lauwaet et al, 2011). The fact that, at the ultrastructural level, the labelling was observed only on a fraction of basal bodies by pre-embedding labelling on whole permeabilised cells as well as by post-embedding labelling on sections of non permeabilised cells, suggests that the protein is not abundant and/or located on discrete structures, thus not found on all longitudinal sections of basal bodies.…”

Regulation of a Myb Transcription Factor by Cyclin-dependent Kinase 2 in Giardia lamblia

“…Similarly, it has been found that the expression of plant Cdks was induced in specific tissues with a high proliferative or mitotic competence (78). Interestingly, the giardial Cdk2 was detected in the basal body-enriched fraction, suggesting its role in giardial cell division (85). We also found that FIGURE 6.…”

SAS-4 Protein in Trypanosoma brucei Controls Life Cycle Transitions by Modulating the Length of the Flagellum Attachment Zone Filament

“…Paramecium tetraurelia, a ciliated protozoan that branched after T. brucei from the last common eukaryotic ancestor, contains a SAS-4 homolog that is essential for basal body duplication (48). However, Giardia lamblia, one of the earliest diverging eukaryotes following the last common eukaryotic ancestor (49), contains a conserved SAS-4 homolog that is enriched in the basal body, although its function is not known (50). Therefore, it is highly likely that the T. brucei SAS-4 homolog has evolved a novel function.…”