Identification of Obscure yet Conserved Actin-Associated Proteins in Giardia lamblia

ABSTRACTConsistent with its proposed status as an early branching eukaryote,Giardiahas the most divergent actin of any eukaryote and lacks core actin regulators. Although conserved actin-binding proteins are missing fromGiardia, 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 inGiardiausing 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 althoughGiardialacks 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.

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Involvement of Actin and Actin-Binding Proteins in Carcinogenesis

Cells ◽

10.3390/cells9102245 ◽

2020 ◽

Vol 9 (10) ◽

pp. 2245 ◽

Cited By ~ 1

Author(s):

Magdalena Izdebska ◽

Wioletta Zielińska ◽

Marta Hałas-Wiśniewska ◽

Alina Grzanka

Keyword(s):

Cancer Cells ◽

Binding Proteins ◽

Initial Step ◽

Actin Binding ◽

Migration And Invasion ◽

Filamin A ◽

Actin Binding Proteins ◽

Promote Cell Proliferation ◽

Cellular Processes ◽

Associated Proteins

The actin cytoskeleton plays a crucial role in many cellular processes while its reorganization is important in maintaining cell homeostasis. However, in the case of cancer cells, actin and ABPs (actin-binding proteins) are involved in all stages of carcinogenesis. Literature has reported that ABPs such as SATB1 (special AT-rich binding protein 1), WASP (Wiskott-Aldrich syndrome protein), nesprin, and villin take part in the initial step of carcinogenesis by regulating oncogene expression. Additionally, changes in actin localization promote cell proliferation by inhibiting apoptosis (SATB1). In turn, migration and invasion of cancer cells are based on the formation of actin-rich protrusions (Arp2/3 complex, filamin A, fascin, α-actinin, and cofilin). Importantly, more and more scientists suggest that microfilaments together with the associated proteins mediate tumor vascularization. Hence, the presented article aims to summarize literature reports in the context of the potential role of actin and ABPs in all steps of carcinogenesis.

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Actin–binding proteins in the Arabidopsis genome database: properties of functionally distinct plant actin–depolymerizing factors/cofilins

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2002.1086 ◽

2002 ◽

Vol 357 (1422) ◽

pp. 791-798 ◽

Cited By ~ 51

Author(s):

Patrick J. Hussey ◽

Ellen G. Allwood ◽

Andrei P. Smertenko

Keyword(s):

Abiotic Stresses ◽

Cytoplasmic Streaming ◽

Binding Proteins ◽

Plant Cells ◽

Actin Binding ◽

Biotic And Abiotic Stresses ◽

Actin Binding Proteins ◽

Genome Database ◽

Cellular Processes ◽

Stimulus Responsive

The plant actin cytoskeleton is a highly dynamic, fibrous structure essential in many cellular processes including cell division and cytoplasmic streaming. This structure is stimulus responsive, being affected by internal stimuli, by biotic and abiotic stresses mediated in signal transduction pathways by actin–binding proteins. The completion of the Arabidopsis genome sequence has allowed a comparative identification of many actin–binding proteins. However, not all are conserved in plants, which possibly reflects the differences in the processes involved in morphogenesis between plant and other cells. Here we have searched for the Arabidopsis equivalents of 67 animal/fungal actin–binding proteins and show that 36 are not conserved in plants. One protein that is conserved across phylogeny is actin–depolymerizing factor or cofilin and we describe our work on the activity of vegetative tissue and pollen–specific isoforms of this protein in plant cells, concluding that they are functionally distinct.

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Actin-binding proteins from Drosophila embryos: a complex network of interacting proteins detected by F-actin affinity chromatography.

The Journal of Cell Biology ◽

10.1083/jcb.109.6.2963 ◽

1989 ◽

Vol 109 (6) ◽

pp. 2963-2975 ◽

Cited By ~ 77

Author(s):

K G Miller ◽

C M Field ◽

B M Alberts

Keyword(s):

Affinity Chromatography ◽

Complex Network ◽

Binding Proteins ◽

Actin Binding ◽

Small Subset ◽

Interacting Proteins ◽

Actin Binding Proteins ◽

Cell Extracts ◽

Drosophila Embryos

By using F-actin affinity chromatography columns to select proteins solely by their ability to bind to actin filaments, we have identified and partially purified greater than 40 proteins from early Drosophila embryos. These proteins represent approximately 0.5% of the total protein present in soluble cell extracts, and 2 mg are obtained by chromatography of an extract from 10 g of embryos. As judged by immunofluorescence of fixed embryos, 90% of the proteins that we have detected in F-actin column eluates are actin-associated in vivo (12 of 13 proteins tested). The distributions of antigens observed suggest that groups of these proteins cooperate in generating unique actin structures at different places in the cell. These structures change as cells progress through the cell cycle and as they undergo the specializations that accompany development. The variety of different spatial localizations that we have observed in a small subset of the total actin-binding proteins suggests that the actin cytoskeleton is a very complex network of interacting proteins.

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Evolutionary conservation of actin-binding proteins inTrypanosoma cruziand unusual subcellular localization of the actin homologue

Parasitology ◽

10.1017/s0031182008004496 ◽

2008 ◽

Vol 135 (8) ◽

pp. 955-965 ◽

Cited By ~ 16

Author(s):

L. D. B. DE MELO ◽

C. SANT'ANNA ◽

S. A. REIS ◽

D. LOURENÇO ◽

W. DE SOUZA ◽

...

Keyword(s):

Spatial Organization ◽

Binding Proteins ◽

Homology Modelling ◽

Actin Binding ◽

Protein Sequence Analysis ◽

Actin Binding Proteins ◽

Cellular Processes ◽

Dynamic Events ◽

Cell Substrate

SUMMARYThe actin cytoskeleton controls pivotal cellular processes such as motility and cytokinesis, as well as cell-cell and cell-substrate interactions. Assembly and spatial organization of actin filaments are dynamic events regulated by a large repertoire of actin-binding proteins. This report presents the first detailed characterization of theTrypanosoma cruziactin (TcActin). Protein sequence analysis and homology modelling revealed that the overall structure ofT. cruziactin is conserved and that the majority of amino-acid changes are concentrated on the monomer surface. Immunofluorescence assays using specific polyclonal antibody against TcActin revealed numerous rounded and punctated structures spread all over the parasitic body. No pattern differences could be found between epimastigotes and trypomastigotes or amastigotes. Moreover, in detergent extracts, TcActin was localized only in the soluble fraction, indicating its presence in the G-actin form or in short filaments dissociated from the microtubule cytoskeleton. The trypanosomatid genome was prospected to identify actin-binding and actin-related conserved proteins. The main proteins responsible for actin nucleation and treadmilling in higher eukaryotes are conserved inT. cruzi.

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The actin cytoskeleton of Dictyostelium: a story told by mutants

Journal of Cell Science ◽

10.1242/jcs.113.5.759 ◽

2000 ◽

Vol 113 (5) ◽

pp. 759-766 ◽

Cited By ~ 4

Author(s):

A.A. Noegel ◽

M. Schleicher

Keyword(s):

Actin Cytoskeleton ◽

Binding Proteins ◽

Developmental Stages ◽

Temporal Dynamics ◽

Cell Signalling ◽

Actin Binding ◽

Actin Binding Proteins ◽

Associated Proteins ◽

Bona Fide ◽

Cellular Behaviour

Actin-binding proteins are effectors of cell signalling and coordinators of cellular behaviour. Research on the Dictyostelium actin cytoskeleton has focused both on the elucidation of the function of bona fide actin-binding proteins as well as on proteins involved in signalling to the cytoskeleton. A major part of this work is concerned with the analysis of Dictyostelium mutants. The results derived from these investigations have added to our understanding of the role of the actin cytoskeleton in growth and development. Furthermore, the studies have identified several cellular and developmental stages that are particularly sensitive to an unbalanced cytoskeleton. In addition, use of GFP fusion proteins is revealing the spatial and temporal dynamics of interactions between actin-associated proteins and the cytoskeleton.

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