scholarly journals The Novel Adaptor Protein, Mti1p, and Vrp1p, a Homolog of Wiskott-Aldrich Syndrome Protein-Interacting Protein (WIP), May Antagonistically Regulate Type I Myosins in Saccharomyces cerevisiae

Genetics ◽  
2002 ◽  
Vol 160 (3) ◽  
pp. 923-934
Author(s):  
Junko Mochida ◽  
Takaharu Yamamoto ◽  
Konomi Fujimura-Kamada ◽  
Kazuma Tanaka
Keyword(s):  
Adaptor Protein ◽  
Actin Binding ◽  
Temperature Sensitive ◽  
Null Mutation ◽  
Type I ◽  
Cortical Actin ◽  
Tail Region ◽  
Interacting Protein ◽  
Wiskott Aldrich Syndrome ◽  
Syndrome Protein

Abstract Type I myosins in yeast, Myo3p and Myo5p (Myo3/5p), are involved in the reorganization of the actin cytoskeleton. The SH3 domain of Myo5p regulates the polymerization of actin through interactions with both Las17p, a homolog of mammalian Wiskott-Aldrich syndrome protein (WASP), and Vrp1p, a homolog of WASP-interacting protein (WIP). Vrp1p is required for both the localization of Myo5p to cortical patch-like structures and the ATP-independent interaction between the Myo5p tail region and actin filaments. We have identified and characterized a new adaptor protein, Mti1p (Myosin tail region-interacting protein), which interacts with the SH3 domains of Myo3/5p. Mti1p co-immunoprecipitated with Myo5p and Mti1p-GFP co-localized with cortical actin patches. A null mutation of MTI1 exhibited synthetic lethal phenotypes with mutations in SAC6 and SLA2, which encode actin-bundling and cortical actin-binding proteins, respectively. Although the mti1 null mutation alone did not display any obvious phenotype, it suppressed vrp1 mutation phenotypes, including temperature-sensitive growth, abnormally large cell morphology, defects in endocytosis and salt-sensitive growth. These results suggest that Mti1p and Vrp1p antagonistically regulate type I myosin functions.

scholarly journals The Wiskott-Aldrich Syndrome Protein-interacting Protein (WIP) Binds to the Adaptor Protein Nck

1998 ◽  
Vol 273 (33) ◽  
pp. 20992-20995 ◽  
Author(s):  
Inés M. Antón ◽  
Wange Lu ◽  
Bruce J. Mayer ◽  
Narayanaswamy Ramesh ◽  
Raif S. Geha
Keyword(s):  
Adaptor Protein ◽  
Interacting Protein ◽  
Wiskott Aldrich Syndrome ◽  
Syndrome Protein

scholarly journals Osmotic stress and the yeast cytoskeleton: phenotype-specific suppression of an actin mutation.

1992 ◽  
Vol 118 (3) ◽  
pp. 561-571 ◽  
Author(s):  
S Chowdhury ◽  
K W Smith ◽  
M C Gustin
Keyword(s):  
Osmotic Stress ◽  
Actin Filament ◽  
Physiological Process ◽  
Actin Binding ◽  
Temperature Sensitive ◽  
Filamentous Actin ◽  
Cortical Actin ◽  
Yeast Saccharomyces Cerevisiae ◽  
Rhodamine Phalloidin ◽  
Diploid Cells

In the yeast Saccharomyces cerevisiae, actin filaments function to direct cell growth to the emerging bud. Yeast has a single essential actin gene, ACT1. Diploid cells containing a single copy of ACT1 are osmosensitive (Osms), i.e., they fail to grow in high osmolarity media (D. Shortle, unpublished observations cited by Novick, P., and D. Botstein. 1985. Cell. 40:415-426). This phenotype suggests that an underlying physiological process involving actin is osmosensitive. Here, we demonstrate that this physiological process is a rapid and reversible change in actin filament organization in cells exposed to osmotic stress. Filamentous actin was stained using rhodamine phalloidin. Increasing external osmolarity caused a rapid loss of actin filament cables, followed by a slower redistribution of cortical actin filament patches. In the recovery phase, cables and patches were restored to their original levels and locations. Strains containing an act1-1 mutation are both Osms and temperature-sensitive (Ts) (Novick and Botstein, 1985). To identify genes whose products functionally interact with actin in cellular responses to osmotic stress, we have isolated extragenic suppressors which revert only the Osms but not the Ts phenotype of an act1-1 mutant. These suppressors identify three genes, RAH1-RAH3. Morphological and genetic properties of a dominant suppressor mutation suggest that the product of the wild-type allele, RAH3+, is an actin-binding protein that interacts with actin to allow reassembly of the cytoskeleton following osmotic stress.

scholarly journals CD44 and β3 Integrin Organize Two Functionally Distinct Actin-based Domains in Osteoclasts

2007 ◽  
Vol 18 (12) ◽  
pp. 4899-4910 ◽  
Author(s):  
Anne Chabadel ◽  
Inmaculada Bañon-Rodríguez ◽  
David Cluet ◽  
Brian B. Rudkin ◽  
Bernhard Wehrle-Haller ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Actin Cytoskeleton ◽  
Interacting Protein ◽  
Wiskott Aldrich Syndrome ◽  
Diffuse Cloud ◽  
Sealing Zone ◽  
Β3 Integrin ◽  
Syndrome Protein

The actin cytoskeleton of mature osteoclasts (OCs) adhering to nonmineralized substrates is organized in a belt of podosomes reminiscent of the sealing zone (SZ) found in bone resorbing OCs. In this study, we demonstrate that the belt is composed of two functionally different actin-based domains: podosome cores linked with CD44, which are involved in cell adhesion, and a diffuse cloud associated with β3 integrin, which is involved in cell adhesion and contraction. Wiskott Aldrich Syndrome Protein (WASp) Interacting Protein (WIP)−/− OCs were devoid of podosomes, but they still exhibited actin clouds. Indeed, WIP−/− OCs show diminished expression of WASp, which is required for podosome formation. CD44 is a novel marker of OC podosome cores and the first nonintegrin receptor detected in these structures. The importance of CD44 is revealed by showing that its clustering restores podosome cores and WASp expression in WIP−/− OCs. However, although CD44 signals are sufficient to form a SZ, the presence of WIP is indispensable for the formation of a fully functional SZ.

scholarly journals Filopodia formation and endosome clustering induced by mutant plus-end–directed myosin VI

2017 ◽  
Vol 114 (7) ◽  
pp. 1595-1600 ◽  
Author(s):  
Thomas A. Masters ◽  
Folma Buss
Keyword(s):  
Actin Filaments ◽  
Leucine Zipper ◽  
Adaptor Protein ◽  
Cell Cortex ◽  
Myosin Vi ◽  
Actin Network ◽  
Ph Domain ◽  
Cortical Actin ◽  
Directed Movement ◽  
Interacting Protein

Myosin VI (MYO6) is the only myosin known to move toward the minus end of actin filaments. It has roles in numerous cellular processes, including maintenance of stereocilia structure, endocytosis, and autophagosome maturation. However, the functional necessity of minus-end–directed movement along actin is unclear as the underlying architecture of the local actin network is often unknown. To address this question, we engineered a mutant of MYO6, MYO6+, which undergoes plus-end–directed movement while retaining physiological cargo interactions in the tail. Expression of this mutant motor in HeLa cells led to a dramatic reorganization of cortical actin filaments and the formation of actin-rich filopodia. MYO6 is present on peripheral adaptor protein, phosphotyrosine interacting with PH domain and leucine zipper 1 (APPL1) signaling endosomes and MYO6+ expression causes a dramatic relocalization and clustering of this endocytic compartment in the cell cortex. MYO6+ and its adaptor GAIP interacting protein, C terminus (GIPC) accumulate at the tips of these filopodia, while APPL1 endosomes accumulate at the base. A combination of MYO6+ mutagenesis and siRNA-mediated depletion of MYO6 binding partners demonstrates that motor activity and binding to endosomal membranes mediated by GIPC and PI(4,5)P2 are crucial for filopodia formation. A similar reorganization of actin is induced by a constitutive dimer of MYO6+, indicating that multimerization of MYO6 on endosomes through binding to GIPC is required for this cellular activity and regulation of actin network structure. This unique engineered MYO6+ offers insights into both filopodia formation and MYO6 motor function at endosomes and at the plasma membrane.

scholarly journals The expression of Wiskott-Aldrich syndrome protein (WASP) is dependent on WASP-interacting protein (WIP)

2006 ◽  
Vol 19 (2) ◽  
pp. 185-192 ◽  
Author(s):  
A. Konno ◽  
M. Kirby ◽  
S. A. Anderson ◽  
P. L. Schwartzberg ◽  
F. Candotti
Keyword(s):  
Interacting Protein ◽  
Wiskott Aldrich Syndrome ◽  
Syndrome Protein

scholarly journals Aip1 and Cofilin Promote Rapid Turnover of Yeast Actin Patches and Cables: A Coordinated Mechanism for Severing and Capping Filaments

2006 ◽  
Vol 17 (7) ◽  
pp. 2855-2868 ◽  
Author(s):  
Kyoko Okada ◽  
Harini Ravi ◽  
Ellen M. Smith ◽  
Bruce L. Goode
Keyword(s):  
Close Correlation ◽  
Actin Binding ◽  
Temperature Sensitive ◽  
Interacting Protein ◽  
Rapid Turnover ◽  
Actin Cable ◽  
Actin Turnover ◽  
Actin Cables

Rapid turnover of actin structures is required for dynamic remodeling of the cytoskeleton and cell morphogenesis, but the mechanisms driving actin disassembly are poorly defined. Cofilin plays a central role in promoting actin turnover by severing/depolymerizing filaments. Here, we analyze the in vivo function of a ubiquitous actin-interacting protein, Aip1, suggested to work with cofilin. We provide the first demonstration that Aip1 promotes actin turnover in living cells. Further, we reveal an unanticipated role for Aip1 and cofilin in promoting rapid turnover of yeast actin cables, dynamic structures that are decorated and stabilized by tropomyosin. Through systematic mutagenesis of Aip1 surfaces, we identify two well-separated F-actin–binding sites, one of which contributes to actin filament binding and disassembly specifically in the presence of cofilin. We also observe a close correlation between mutations disrupting capping of severed filaments in vitro and reducing rates of actin turnover in vivo. We propose a model for balanced regulation of actin cable turnover, in which Aip1 and cofilin function together to “prune” tropomyosin-decorated cables along their lengths. Consistent with this model, deletion of AIP1 rescues the temperature-sensitive growth and loss of actin cable defects of tpm1Δ mutants.

scholarly journals TheSaccharomyces cerevisiaeHomologue of Human Wiskott–Aldrich Syndrome Protein Las17p Interacts with the Arp2/3 Complex

1999 ◽  
Vol 10 (10) ◽  
pp. 3521-3538 ◽  
Author(s):  
Ammar Madania ◽  
Pascal Dumoulin ◽  
Sandrine Grava ◽  
Hiroko Kitamoto ◽  
Claudia Schärer-Brodbeck ◽  
...  
Keyword(s):  
Actin Polymerization ◽  
Temperature Sensitive ◽  
Multicopy Suppressor ◽  
Wiskott Aldrich Syndrome ◽  
Regulatory Cascades ◽  
Src Homology ◽  
Synthetically Lethal ◽  
Actin Patch ◽  
Syndrome Protein

Yeast Las17 protein is homologous to the Wiskott–Aldrich Syndrome protein, which is implicated in severe immunodeficiency. Las17p/Bee1p has been shown to be important for actin patch assembly and actin polymerization. Here we show that Las17p interacts with the Arp2/3 complex. LAS17 is an allele-specific multicopy suppressor of ARP2 and ARP3 mutations; overexpression restores both actin patch organization and endocytosis defects in ARP2 temperature-sensitive (ts) cells. Six of seven ARP2 ts mutants and at least oneARP3 ts mutant are synthetically lethal withlas17Δ ts confirming functional interaction with the Arp2/3 complex. Further characterization of las17Δcells showed that receptor-mediated internalization of α factor by the Ste2 receptor is severely defective. The polarity of normal bipolar bud site selection is lost. Las17-gfp remains localized in cortical patches in vivo independently of polymerized actin and is required for the polarized localization of Arp2/3 as well as actin. Coimmunoprecipitation of Arp2p with Las17p indicates that Las17p interacts directly with the complex. Two hybrid results also suggest that Las17p interacts with actin, verprolin, Rvs167p and several other proteins including Src homology 3 (SH3) domain proteins, suggesting that Las17p may integrate signals from different regulatory cascades destined for the Arp2/3p complex and the actin cytoskeleton.

scholarly journals Isoform-specific complementation of the yeast sac6 null mutation by human fimbrin.

1995 ◽  
Vol 15 (1) ◽  
pp. 69-75 ◽  
Author(s):  
A E Adams ◽  
W Shen ◽  
C S Lin ◽  
J Leavitt ◽  
P Matsudaira
Keyword(s):  
Cell Types ◽  
Biochemical Properties ◽  
Actin Binding ◽  
Growth Defect ◽  
Temperature Sensitive ◽  
Null Mutation ◽  
Homologous Proteins ◽  
Functional Conservation ◽  
Cytoskeletal Component

The actin cytoskeleton is a fundamental component of eukaryotic cells, with both structural and motile roles. Actin and many of the actin-binding proteins found in different cell types are highly conserved, showing considerable similarity in both primary structure and biochemical properties. To make detailed comparisons between homologous proteins, it is necessary to know whether the various proteins are functionally, as well as structurally, conserved. Fimbrin is an example of a cytoskeletal component that, as shown by sequence determinations and biochemical characterizations, is conserved between organisms as diverse as Saccharomyces cerevisiae and humans. In this study, we examined whether the human homolog can substitute for the yeast protein in vivo. We report here that two isoforms of human fimbrin, also referred to as T- and L-plastin, can both substitute in vivo for yeast fimbrin, also known as Sac6p, whereas a third isoform, I-fimbrin (or I-plastin), cannot. We demonstrate that the human T- and L-fimbrins, in addition to complementing the temperature-sensitive growth defect of the sac6 null mutant, restore both normal cytoskeletal organization and cell shape to the mutant cells. In addition, we show that human T- and L-fimbrins can complement a sporulation defect caused by the sac6 null mutation. These findings indicate that there is a high degree of functional conservation in the cytoskeleton, even between organisms as diverse as S. cerevisiae and humans.

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