A Bni4-Glc7 phosphatase complex that recruits chitin synthase to the site of bud emergence

Mol Biol Cell. 2003 Jan;14(1):26-39. doi: 10.1091/mbc.e02-06-0373.

Abstract

Bni4 is a scaffold protein in the yeast Saccharomyces cerevisiae that tethers chitin synthase III to the bud neck by interacting with septin neck filaments and with Chs4, a regulatory subunit of chitin synthase III. We show herein that Bni4 is also a limiting determinant for the targeting of the type 1 serine/threonine phosphatase (Glc7) to the bud neck. Yeast cells containing a Bni4 variant that fails to associate with Glc7 fail to tether Chs4 to the neck, due in part to the failure of Bni4(V831A/F833A) to localize properly. Conversely, the Glc7-129 mutant protein fails to bind Bni4 properly and glc7-129 mutants exhibit reduced levels of Bni4 at the bud neck. Bni4 is phosphorylated in a cell cycle-dependent manner and Bni4(V831A/F833A) is both hyperphosphorylated and mislocalized in vivo. Yeast cells lacking the protein kinase Hsl1 exhibit increased levels of Bni4-GFP at the bud neck. GFP-Chs4 does not accumulate at the incipient bud site in either a bni4::TRP1 or a bni4(V831A/F833A) mutant but does mobilize to the neck at cytokinesis. Together, these results indicate that the formation of the Bni4-Glc7 complex is required for localization to the site of bud emergence and for subsequent targeting of chitin synthase.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cell Division / physiology
  • Chitin Synthase / metabolism*
  • Phosphoprotein Phosphatases / metabolism*
  • Protein Kinases / metabolism
  • Protein Phosphatase 1
  • Protein Serine-Threonine Kinases
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / metabolism*

Substances

  • Saccharomyces cerevisiae Proteins
  • Chitin Synthase
  • Protein Kinases
  • HSL1 protein, S cerevisiae
  • Protein Serine-Threonine Kinases
  • GLC7 protein, S cerevisiae
  • Phosphoprotein Phosphatases
  • Protein Phosphatase 1