Saccharomyces cerevisiae Bzz1p Is Implicated with Type I Myosins in Actin Patch Polarization and Is Able To Recruit Actin-Polymerizing Machinery In Vitro

Abstract

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 bzz1⌬ myo5⌬ 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.

Dictyostelium MEGAPs: F-BAR domain proteins that regulate motility and membrane tubulation in contractile vacuoles

“…These genes encode proteins with N-terminal FCH and predicted coiled-coil domains and a C-terminal SH3 domain but no RhoGAP domains. Their domain organisations are similar to Syndapin (Qualmann et al, 1999) and Nwk/Bzz1p (Soulard et al, 2002;Coyle et al, 2004;Vlahou and Rivero, 2006), respectively (Fig. 1A).…”

F-BAR domains: multifunctional regulators of membrane curvature

“…The best-characterised interaction is between F-BAR proteins and Wiskott-Aldrich syndrome protein (WASP) or neuronal-WASP (N-WASP), which are regulators of the actin-nucleating Arp2/3 complex (Ho et al, 2004). This interaction has also been observed in the budding yeast Saccharomyces cerevisiae, in which the PSTPIP orthologue Bzz1p binds to the WASP orthologue Las17p (Soulard et al, 2002). In resting mammalian cells, members of the WASP-interacting protein (WIP) family sequester N-WASP in an auto-inhibited conformation that masks the C-terminal Arp2/3-binding site.…”

TheUstilago maydisClp1 Protein Orchestrates Pheromone andb-Dependent Signaling Pathways to Coordinate the Cell Cycle and Pathogenic Development

“…Notably, as Clp1-interacting proteins (see Supplemental Table 1 online), we identified Cdc15, a protein required for cytokinesis and nuclear distribution in U. maydis (Bö hmer et al, 2009) and, in addition, the orthologs of BZZ1, Mob1, and CDC36, which were shown to be involved in septum formation, polar growth, and cell cycle control in various fungal species (Hartwell et al, 1970;Reed, 1980;Breter et al, 1983;Luca and Winey, 1998;Luca et al, 2001;Soulard et al, 2002;Weiss et al, 2002;Song et al, 2008;Maerz et al, 2009). A possible role for these proteins during in planta development of U. maydis has not been investigated yet and thus remains speculative.…”