Article

Novel Interactors and a Role for Supervillin in Early Cytokinesis

Department of Cell Biology and Cell Dynamics Program, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
Cytoskeleton (Impact Factor: 3.12). 06/2010; 67(6):346-64. DOI: 10.1002/cm.20449
Source: PubMed

ABSTRACT

Supervillin, the largest member of the villin/gelsolin/flightless family, is a peripheral membrane protein that regulates each step of cell motility, including cell spreading. Most known interactors bind within its amino (N)-terminus. We show here that the supervillin carboxy (C)-terminus can be modeled as supervillin-specific loops extending from gelsolin-like repeats plus a villin-like headpiece. We have identified 27 new candidate interactors from yeast two-hybrid screens. The interacting sequences from 12 of these proteins (BUB1, EPLIN/LIMA1, FLNA, HAX1, KIF14, KIFC3, MIF4GD/SLIP1, ODF2/Cenexin, RHAMM, STARD9/KIF16A, Tks5/SH3PXD2A, TNFAIP1) co-localize with and mis-localize EGFP-supervillin in mammalian cells, suggesting associations in vivo. Supervillin-interacting sequences within BUB1, FLNA, HAX1, and MIF4GD also mimic supervillin over-expression by inhibiting cell spreading. Most new interactors have known roles in supervillin-associated processes, e.g. cell motility, membrane trafficking, ERK signaling, and matrix invasion; three (KIF14, KIFC3, STARD9/KIF16A) have kinesin motor domains; and five (EPLIN, KIF14, BUB1, ODF2/cenexin, RHAMM) are important for cell division. GST fusions of the supervillin G2-G3 or G4-G6 repeats co-sediment KIF14 and EPLIN, respectively, consistent with a direct association. Supervillin depletion leads to increased numbers of bi- and multi-nucleated cells. Cytokinesis failure occurs predominately during early cytokinesis. Supervillin localizes with endogenous myosin II and EPLIN in the cleavage furrow, and overlaps with the oncogenic kinesin, KIF14, at the midbody. We conclude that supervillin, like its interactors, is important for efficient cytokinesis. Our results also suggest that supervillin and its interaction partners coordinate actin and microtubule motor functions throughout the cell cycle.

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    • "SVIL belongs to the gelsolin gene family, which encodes a number of actin-binding proteins (ABPs). These proteins have been shown to control important actin-dependent functions in the cytoplasm, such as cell division, mobility, and morphology (Bhuwania et al., 2012; Fang et al., 2010; Smith et al., 2010). However, these ABPs also have specific nuclear functions such as nuclear transport, structural maintenance, and regulation of transcription (Ting et al., 2002; Wulfkuhle et al., 1999). "
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    ABSTRACT: Lysine-specific demethylase 1 (LSD1) has been reported to repress and activate transcription by mediating histone H3K4me1/2 and H3K9me1/2 demethylation, respectively. The molecular mechanism that underlies this dual substrate specificity has remained unknown. Here we report that an isoform of LSD1, LSD1+8a, does not have the intrinsic capability to demethylate H3K4me2. Instead, LSD1+8a mediates H3K9me2 demethylation in collaboration with supervillin (SVIL), a new LSD1+8a interacting protein. LSD1+8a knockdown increases H3K9me2, but not H3K4me2, levels at its target promoters and compromises neuronal differentiation. Importantly, SVIL co-localizes to LSD1+8a-bound promoters, and its knockdown mimics the impact of LSD1+8a loss, supporting SVIL as a cofactor for LSD1+8a in neuronal cells. These findings provide insight into mechanisms by which LSD1 mediates H3K9me demethylation and highlight alternative splicing as a means by which LSD1 acquires selective substrate specificities (H3K9 versus H3K4) to differentially control specific gene expression programs in neurons. Copyright © 2015 Elsevier Inc. All rights reserved.
    Full-text · Article · Feb 2015 · Molecular cell
    • "To determine whether the supervillin-Trio interaction functions in vivo, we first looked for dominant-negative effects of supervillin-interacting Trio protein fragments on early cell spreading (Fig. 7). Based on our prior observations that 30 min after replating is a point of maximal difference in the diameters of spreading cells [Takizawa et al., 2007; Smith et al., 2010], we quantified the percentages of spread HeLa cells, defined as cells with lengths >two times that of the mean diameter of initially plated cells. Overexpression of myc-Trio 771–1057, but not other Trio protein fragments assayed, significantly delayed cell spreading (Figs. "
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    ABSTRACT: We investigated cross-talk between the membrane-associated, myosin II-regulatory protein supervillin and the actin-regulatory small GTPases Rac1, RhoA, and Cdc42. Supervillin knockdown reduced Rac1-GTP loading, but not the GTP loading of RhoA or Cdc42, in HeLa cells with normal levels of the Rac1-activating protein Trio. No reduction in Rac1-GTP loading was observed when supervillin levels were reduced in Trio-depleted cells. Conversely, overexpression of supervillin isoform 1 (SV1) or, especially, isoform 4 (SV4) increased Rac1 activation. Inhibition of the Trio-mediated Rac1 guanine nucleotide exchange (GEF) activity with ITX3 partially blocked the SV4-mediated increase in Rac1-GTP. Both SV4 and SV1 co-localized with Trio at or near the plasma membrane in ruffles and cell surface projections. Two sequences within supervillin bound directly to Trio spectrin repeats 4-7: SV1-171, which contains N-terminal residues found in both SV1 and SV4 and the SV4-specific differentially spliced coding exons 3, 4, and 5 within SV4 (SV4-E345; SV4 amino acids 276 – 669). In addition, SV4-E345 interacted with the homologous sequence in rat kalirin (repeats 4-7, amino acids 531 - 1101). Overexpressed SV1-174 and SV4-E345 affected Rac1-GTP loading, but only in cells with endogenous levels of Trio. Trio residues 771 – 1057, which contain both supervillin-interaction sites, exerted a dominant-negative effect on cell spreading. Supervillin and Trio knockdowns, separately or together, inhibited cell spreading, suggesting that supervillin regulates the Rac1 guanine nucleotide exchange activity of Trio, and potentially also kalirin, during cell spreading and lamellipodia extension. This article is protected by copyright. All rights reserved.
    No preview · Article · Feb 2015 · Cytoskeleton
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    • "The type-1 calcium-binding site is present in domain 4, further suggesting that this may be a functional actin binding domain. Supervillin forms links between membranes and the actin cytoskeleton, and participates in myogenesis [Oh et al., 2003], cytokinesis [Smith et al., 2010], cell-substrate adhesion of platelets and tumor cells [Takizawa et al., 2006; Edelstein et al., 2012], cell spreading [Takizawa et al., 2007], motility [Fang et al., 2010], invadosome function in macrophages and tumor cells [Crowley et al., 2009; Bhuwania et al., 2012], transactivation of the androgen receptor [Sampson et al., 2001; Ting et al., 2002] and cytoarchitecture at both the nucleus and plasma membrane [Wulfkuhle et al., 1999; Chen et al., 2003]. Recently, supervillin has also been shown to regulate cell survival through the control of p53 levels [Fang and Luna, 2013]. "
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    ABSTRACT: Gelsolin superfamily members are Ca(2+) -dependent, multi-domain regulators of the actin cytoskeleton. Calcium binding activates gelsolin by inducing molecular gymnastics (large-scale conformational changes) that expose actin interaction surfaces by releasing a series of latches. A specialized tail latch has distinguished gelsolin within the superfamily. Active gelsolin exhibits actin filament severing and capping, and actin monomer sequestering activities. Here, we analyze a combination of sequence, structural, biophysical and biochemical data to assess whether the molecular plasticity, regulation and actin-related properties of gelsolin are also present in other superfamily members. We conclude that all members of the superfamily will be able to transition between a compact conformation and a more open form, and that most of these open forms will interact with actin. Supervillin, which lacks the severing domain 1 and the F-actin binding-site on domain 2, is the clear exception. Eight calcium-binding sites are absolutely conserved in gelsolin, adseverin, advillin and villin, and compromised to increasing degrees in CapG, villin-like protein, supervillin and flightless I. Advillin, villin and supervillin each contain a potential tail latch, which is absent from CapG, adseverin and flightless I, and ambiguous in villin-like protein. Thus, calcium regulation will vary across the superfamily. Potential novel isoforms of the superfamily suggest complex regulation at the gene, transcript and protein levels. We review animal, clinical and cellular data that illuminate how the regulation of molecular flexibility in gelsolin-like proteins permits cells to exploit the force generated from actin polymerization to drive processes such as cell movement in health and disease.
    Full-text · Article · Jul 2013 · Cytoskeleton
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