: Giardia lamblia, an important human pathogen, must successfully excyst in order to infect a new host. Since excystation is too rapid to rely entirely on new gene expression, the unifying hypothesis of this proposal is that second messenger pathways may be central for regulation. While we can reproduce the entire life cycle in vitro, neither the precise stimuli nor the second messenger pathways that regulate excystation are known. Based on extensive Preliminary Data, we propose these Specific Aims:
Specific Aim 1 is to define the key physiological excystation stimuli, and to test the hypothesis that Giardia cysts' responses to these signals are mediated by or reflected in changes in cytosolic calcium and/or cyclic AMP. We will ask whether pharmacological release of """"""""caged"""""""" Ca 2v and/or cAMP into the cytosol can bypass the corresponding excystation stimulus.
Specific Aim 2 is to define the role(s) of calmodulin (CAM) in regulating excystation and to identify specific """"""""downstream"""""""" effectors that carry out its function. gCaM co-localizes with protein kinase A to the flagellar basal bodies-centrosomes, suggesting a key role in coordinating these pathways. We will use in vivo cross-linking and genomic data to functionally identify downstream effectors that specifically interact with CaM during excystation.
Specific Aim 3 is to test the hypothesis that changes in protein phosphorylation may be important in regulating excystation, compared with de novo protein synthesis. We will compare changes in protein phosphorylation (the """"""""phosphoproteome""""""""), with overall changes in the protein expression in excysting cells. Sequence analyses and genomic data will permit us to identify key excystation proteins. This proteomic approach will test our overall hypothesis and complement the cellular and molecular data of Aims 1 and 2. Our proposed studies will reveal important insights into regulation of G lamblia excystation. Many other parasites have cystic forms whose excystation is required for transmission. Giardia may be a valuable model for understanding parasite differentiation in the intestinal tract. On a basic level, Giardia excystation is a unique model for cellular awakening from dormancy in response to environmental signals in an early-diverging eukaryotes.
| Davids, B J; Gilbert, M A; Liu, Q et al. (2011) An atypical proprotein convertase in Giardia lamblia differentiation. Mol Biochem Parasitol 175:169-80 |
| Manning, Gerard; Reiner, David S; Lauwaet, Tineke et al. (2011) The minimal kinome of Giardia lamblia illuminates early kinase evolution and unique parasite biology. Genome Biol 12:R66 |
| Lauwaet, Tineke; Smith, Alias J; Reiner, David S et al. (2011) Mining the Giardia genome and proteome for conserved and unique basal body proteins. Int J Parasitol 41:1079-92 |
| Lauwaet, Tineke; Andersen, Yolanda; Van de Ven, Liesbeth et al. (2010) Rapid detachment of Giardia lamblia trophozoites as a mechanism of antimicrobial action of the isoflavone formononetin. J Antimicrob Chemother 65:531-4 |
| Davids, Barbara J; Williams, Sarah; Lauwaet, Tineke et al. (2008) Giardia lamblia aurora kinase: a regulator of mitosis in a binucleate parasite. Int J Parasitol 38:353-69 |
| Reiner, David S; Ankarklev, Johan; Troell, Karin et al. (2008) Synchronisation of Giardia lamblia: identification of cell cycle stage-specific genes and a differentiation restriction point. Int J Parasitol 38:935-44 |
| Ringqvist, Emma; Palm, J E Daniel; Skarin, Hanna et al. (2008) Release of metabolic enzymes by Giardia in response to interaction with intestinal epithelial cells. Mol Biochem Parasitol 159:85-91 |
| Morrison, Hilary G; McArthur, Andrew G; Gillin, Frances D et al. (2007) Genomic minimalism in the early diverging intestinal parasite Giardia lamblia. Science 317:1921-6 |
| Lauwaet, Tineke; Davids, Barbara J; Torres-Escobar, Ascencion et al. (2007) Protein phosphatase 2A plays a crucial role in Giardia lamblia differentiation. Mol Biochem Parasitol 152:80-9 |
| Lauwaet, Tineke; Davids, Barbara J; Reiner, David S et al. (2007) Encystation of Giardia lamblia: a model for other parasites. Curr Opin Microbiol 10:554-9 |
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