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.
Soulard
Alexandre
A
Modèles levure des Pathologies Humaines, F.R.E. 2375 du Centre National de la Recheche Scientifique, Strasbourg, France.
Lechler
Terry
T
Spiridonov
Vladislav
V
Shevchenko
Andrej
A
Shevchenko
Anna
A
Li
Rong
R
Winsor
Barbara
B
D000199:Actins / Q000378:metabolism*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D016764:Cell Polarity; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism*; D005800:Genes, Fungal; D017930:Genes, Reporter; D046911:Macromolecular Substances; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D024461:Myosin Type I / Q000378:metabolism*; D011108:Polymers; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D020798:Two-Hybrid System Techniques; D051316:Wiskott-Aldrich Syndrome Protein
D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; C468557:Bzz1 protein, S cerevisiae; D003598:Cytoskeletal Proteins; C480361:LAS17 protein, S cerevisiae; C100412:MYO5 protein, S cerevisiae; D046911:Macromolecular Substances; D008840:Microfilament Proteins; D011108:Polymers; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D013844:Thiazoles; D053778:Thiazolidines; D051316:Wiskott-Aldrich Syndrome Protein; D024461:Myosin Type I; C037067:latrunculin A