title: Identification of obscure yet conserved actin-associated proteins in Giardia lamblia.
abstract: Consistent with its proposed status as an early branching eukaryote, Giardia has the most divergent actin of any eukaryote and lacks core actin regulators. Although conserved actin-binding proteins are missing from Giardia, its actin is utilized similarly to that of other eukaryotes and functions in core cellular processes such as cellular organization, endocytosis, and cytokinesis. We set out to identify actin-binding proteins in Giardia using affinity purification coupled with mass spectroscopy (multidimensional protein identification technology [MudPIT]) and have identified >80 putative actin-binding proteins. Several of these have homology to conserved proteins known to complex with actin for functions in the nucleus and flagella. We validated localization and interaction for seven of these proteins, including 14-3-3, a known cytoskeletal regulator with a controversial relationship to actin. Our results indicate that although Giardia lacks canonical actin-binding proteins, there is a conserved set of actin-interacting proteins that are evolutionarily indispensable and perhaps represent some of the earliest functions of the actin cytoskeleton.
authors.affiliation: Department of Biology, University of Washington, Seattle, Washington, USA Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California, USA aparedez@uw.edu.
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Paredez
authors.affiliation: Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California, USA.
authors.forename: Arash
authors.initials: A
authors.lastname: Nayeri
authors.affiliation: Department of Biology, University of Washington, Seattle, Washington, USA Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California, USA.
authors.forename: Jennifer W
authors.initials: JW
authors.lastname: Xu
authors.affiliation: Department of Biology, University of Washington, Seattle, Washington, USA.
authors.forename: Jana
authors.initials: J
authors.lastname: Krtková
authors.affiliation: Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California, USA.
authors.forename: W Zacheus
authors.initials: WZ
authors.lastname: Cande
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism; D008841:Actin Cytoskeleton / Q000737:chemistry / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D017124:Conserved Sequence; D005407:Flagella / Q000378:metabolism; D016829:Giardia lamblia / Q000378:metabolism*; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D015800:Protozoan Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D048948:14-3-3 Proteins; D000199:Actins; D008840:Microfilament Proteins; D015800:Protozoan Proteins
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