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The class V myosin Myo2p is required for Fus2p transport and actin polarization during the yeast mating response.

Mating yeast cells remove their cell walls and fuse their plasma membranes in a spatially restricted cell contact region. Cell wall removal is dependent on Fus2p, an amphiphysin-associated Rho-GEF homolog. As mating cells polarize, Fus2p-GFP localizes to the tip of the mating projection, where cell fusion will occur, and to cytoplasmic puncta, which show rapid movement toward the tip. Movement requires polymerized actin, whereas tip localization is dependent on both actin and a membrane protein, Fus1p. Here, we show that Fus2p-GFP movement is specifically dependent on Myo2p, a type V myosin, and not on Myo4p, another type V myosin, or Myo3p and Myo5p, type I myosins. Fus2p-GFP tip localization and actin polarization in shmoos are also dependent on Myo2p. A temperature-sensitive tropomyosin mutation and Myo2p alleles that specifically disrupt vesicle binding caused rapid loss of actin patch organization, indicating that transport is required to maintain actin polarity. Mutant shmoos lost actin polarity more rapidly than mitotic cells, suggesting that the maintenance of cell polarity in shmoos is more sensitive to perturbation. The different velocities, differential sensitivity to mutation and lack of colocalization suggest that Fus2p and Sec4p, another Myo2p cargo associated with exocytotic vesicles, reside predominantly on different cellular organelles.

Pubmed ID: 19403698

Authors

  • Sheltzer JM
  • Rose MD

Journal

Molecular biology of the cell

Publication Data

June 15, 2009

Associated Grants

  • Agency: NIGMS NIH HHS, Id: GM37739
  • Agency: NIGMS NIH HHS, Id: R01 GM037739
  • Agency: NIGMS NIH HHS, Id: R01 GM037739-22

Mesh Terms

  • Actins
  • Alleles
  • Cell Polarity
  • Cytoskeletal Proteins
  • Cytoskeleton
  • Genes, Mating Type, Fungal
  • Membrane Proteins
  • Mutation
  • Myosin Heavy Chains
  • Myosin Type V
  • Protein Structure, Tertiary
  • Protein Transport
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Secretory Vesicles
  • Tropomyosin
  • rab GTP-Binding Proteins