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Cofilin-mediated sorting and export of specific cargo from the Golgi apparatus in yeast

Amy J Curwin1, Julia von Blume, Vivek Malhotra

  • 1Department of Cell and Developmental Biology, Centre for Genomic Regulation, 08003 Barcelona, Spain.

Molecular Biology of the Cell
|May 4, 2012
PubMed

Insights

Cofilin and secretory pathway calcium ATPase 1 (SPCA1) are crucial for sorting secretory proteins at the Golgi. Yeast lacking cofilin shows defects in exporting cell wall proteins and mis-sorting of carboxypeptidase Y (CPY).

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Protein Trafficking

Background:

  • The mechanism of cargo sorting at the trans-Golgi network (TGN) for secretion remains unclear.
  • Previous studies implicated cofilin and secretory pathway calcium ATPase 1 (SPCA1) in mammalian TGN sorting.
  • This study investigates the role of cofilin and its associated pathways in yeast secretion.

Purpose of the Study:

  • To elucidate the function of cofilin in selective secretory cargo export at the late Golgi membranes in yeast.
  • To examine the relationship between cofilin and the yeast SPCA1 orthologue, Pmr1, in protein sorting.
  • To determine if SPCA1/Pmr1 can rescue cofilin-dependent sorting defects.

Main Methods:

  • Analysis of cofilin mutant (cof1-8) yeast strains.
  • Tracking the secretion and localization of cell wall protein Bgl2 and plasma membrane H(+) ATPase Pma1.
  • Investigating the sorting of carboxypeptidase Y (CPY) in cofilin and Pmr1 mutants.
  • Assessing synthetic sickness between cof1-8 and pmr1 loss-of-function mutants.
  • Evaluating the effect of PMR1 overexpression in cof1-8 cells.

Main Results:

  • Cofilin mutant yeast exhibited reduced secretion and late Golgi retention of cell wall protein Bgl2.
  • Plasma membrane H(+) ATPase Pma1 transport was unaffected in cofilin mutants.
  • Sorting of carboxypeptidase Y (CPY) to the vacuole was impaired, leading to CPY secretion.
  • Loss of yeast SPCA1 orthologue (Pmr1) caused similar sorting defects and synthetic sickness with cof1-8.
  • Overexpression of PMR1 rescued Bgl2 secretion defects in cofilin mutant cells.

Conclusions:

  • Cofilin is essential for the export of selective secretory cargo from late Golgi membranes in yeast.
  • The yeast SPCA1 orthologue, Pmr1, plays a conserved role in cargo sorting alongside cofilin.
  • These findings highlight a conserved eukaryotic mechanism involving cofilin and SPCA1/Pmr1 in TGN/late Golgi sorting.

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