Lauwaet, T., D. Reiner, E.P. Romijn, M. Baitaluk, D. Palm, B. Davids, S.Svard, A.G. McArthur, A. Ray, A. Gupta, J. Yates, & F.D. Gillin. 2007. Transcriptome and interaction analyses of the Giardia lamblia basal body proteome. Presentation at the Annual Meeting of the American Society for Cell Biology, Washington, D.C.Encystation and excystation are crucial to the pathogenesis of Giardia lamblia. Both differentiations are marked by dramatic cytoskeletal remodeling. However, the underlying signaling pathways are poorly understood. Earlier, we showed that signaling proteins needed for differentiation localize constitutively to the basal bodies/centrioles. The purpose of this study is to identify Giardia basal body proteins and their roles in differentiation.
We isolated basal bodies from Giardia cytoskeletons by sucrose density centrifugation and assayed the basal body markers γ-tubulin and centrin in the fractions by IFA and ELISA. The basal body enriched fraction was analyzed by Multidimensional protein identification technology (MudPIT), which revealed 308 candidate basal body (cbb) proteins. 31% of the cbb proteins were validated by comparison with other species' centrosome / centriole / basal body proteomes. 33% of the cbb proteins are unique to Giardia and basal body localization of seven of the eight unique cbb proteins was confirmed by IFA.
Serial analysis of gene expression (SAGE) revealed that the mRNA of certain functional classes of cbb proteins is either upregulated in encystation or in excystation. In order to identify potential interactions between the upregulated cbb proteins, we created networks based on the interactions of their yeast and human orthologs in those organisms. The networks derived suggest that the molecular machines involved in encystation are distinct from those in excystation. Moreover, the cbb signaling proteins are highly conserved between Giardia, human and yeast. The presence of differentially regulated signaling proteins and conserved molecular machines in the Giardia basal bodies, supports their central roles in giardial differentiation.
