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.
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.
Mochida
Junko
J
Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, 060-0815, Japan.
Yamamoto
Takaharu
T
Fujimura-Kamada
Konomi
K
Tanaka
Kazuma
K
D000199:Actins / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D003598:Cytoskeletal Proteins; D003599:Cytoskeleton / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D008840:Microfilament Proteins / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D018995:Myosin Heavy Chains / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D020798:Two-Hybrid System Techniques
D000199:Actins; C464845:BBC1 protein, S cerevisiae; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D005656:Fungal Proteins; C491722:MYO3 protein, S cerevisiae; D008840:Microfilament Proteins; D029701:Saccharomyces cerevisiae Proteins; C090350:VRP1 protein, S cerevisiae; D018995:Myosin Heavy Chains