WASP/Las17p-interacting protein Bzz1p functions with Myo5p in an early stage of endocytosis

The formation of actin filaments is crucial for endocytosis and other interrelated cellular phenomena such as motility, polarized morphogenesis, and cytokinesis. In this paper we have investigated the role of the WASP/Las17-interacting protein Bzz1p in endocytosis and trafficking to the vacuole. We...

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Bibliographic Details
Published in:Protoplasma 2005-10, Vol.226 (1-2), p.89-101
Main Authors: Soulard, A, Friant, S, Fitterer, C, Orange, C, Kaneva, G, Mirey, G, Winsor, B
Format: Article
Language:English
Subjects:
actin
actin patch protein
Actins - metabolism
binding proteins
Cell Polarity
Cells
cytochemistry
cytoskeleton
Endocytosis
fungal proteins
Microfilament Proteins - physiology
myosin
Myosin Type I - metabolism
protein-protein interactions
Proteins
Saccharomyces cerevisiae
Saccharomyces cerevisiae Proteins - metabolism
Saccharomyces cerevisiae Proteins - physiology
Signal Transduction
Time Factors
Transport Vesicles - physiology
vacuoles
Wiskott-Aldrich Syndrome Protein - metabolism
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Summary:The formation of actin filaments is crucial for endocytosis and other interrelated cellular phenomena such as motility, polarized morphogenesis, and cytokinesis. In this paper we have investigated the role of the WASP/Las17-interacting protein Bzz1p in endocytosis and trafficking to the vacuole. We and others have recently shown that Bzz1p is an actin patch protein that interacts directly with Las17p via a SH3-polyproline interaction. Bzz1p functions with type I myosins to restore polarity of the actin cytoskeleton after NaCl stress. In an in vitro bead assay, GST-Bzz1p fusion protein triggers a functional actin polymerization machinery through its two C-terminal SH3 domains. In this paper we implicate Bzz1p with the type I myosins both in fluid-phase and in the internalization step of receptor-mediated endocytosis. As deduced from their localization as GFP fusions, the vacuolar delivery of endocytic and biosynthetic cargoes as well as the multivesicular body pathway appear unaffected. We further elucidate Bzz1p direct participation in actin polymerization by demonstrating that each of the SH3 domains of Bzz1p individually is able to trigger actin polymerization in a cell-free system dependent on Arp2/3, Las17p, Vrp1p, and the type I myosins. Taken together, our results show that Bzz1p participates, essentially via its SH3 domains, in early steps of endocytosis together with known actin nucleation activators.
ISSN:0033-183X
1615-6102
DOI:10.1007/s00709-005-0108-4