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Saccharomyces cerevisiae Bzz1p is implicated with type I myosins in actin patch polarization and is able to recruit actin-polymerizing machinery in vitro.

In Saccharomyces cerevisiae, the WASP (Wiskott-Aldrich syndrome protein) homologue Las17p (also called Bee1p) is an important component of cortical actin patches. Las17p is part of a high-molecular-weight protein complex that regulates Arp2/3 complex-dependent actin polymerization at the cell cortex and that includes the type I myosins Myo3p and Myo5p and verprolin (Vrp1p). To identify other factors implicated with this complex in actin regulation, we isolated proteins that bind to Las17p by two-hybrid screening and affinity chromatography. Here, we report the characterization of Lsb7/Bzz1p (for Las seventeen binding protein 7), an Src homology 3 (SH3) domain protein that interacts directly with Las17p via a polyproline-SH3 interaction. Bzz1p coimmunoprecipitates in a complex with Las17p, Vrp1p, Myo3/5p, Bbc1p, Hsp70p, and actin. It colocalizes with cortical actin patches and with Las17p. This localization is dependent on Las17p, but not on F-actin. Bzz1p interacts physically and genetically with type I myosins. While deletion of BZZ1 shows no obvious phenotype, simultaneous deletion of the BZZ1, MYO3, and MYO5 genes is lethal. Overexpression of Bzz1p inhibits cell growth, and a bzz1Delta myo5Delta double mutant is unable to restore actin polarity after NaCl stress. Finally, Bzz1p in vitro is able to recruit a functional actin polymerization machinery through its SH3 domains. Its interactions with Las17p, Vrp1p, and the type I myosins are essential for this process. This suggests that Bzz1p could be implicated in the regulation of actin polymerization.

Pubmed ID: 12391157

Authors

  • Soulard A
  • Lechler T
  • Spiridonov V
  • Shevchenko A
  • Shevchenko A
  • Li R
  • Winsor B

Journal

Molecular and cellular biology

Publication Data

November 22, 2002

Associated Grants

None

Mesh Terms

  • Actins
  • Bicyclo Compounds, Heterocyclic
  • Cell Polarity
  • Cytoskeletal Proteins
  • Cytoskeleton
  • Genes, Fungal
  • Genes, Reporter
  • Macromolecular Substances
  • Microfilament Proteins
  • Myosin Type I
  • Polymers
  • Protein Binding
  • Protein Structure, Tertiary
  • Recombinant Fusion Proteins
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Thiazoles
  • Thiazolidines
  • Two-Hybrid System Techniques
  • Wiskott-Aldrich Syndrome Protein