Quality control of a mutant plasma membrane ATPase: ubiquitylation prevents cell-surface stability

J Cell Sci. 2006 Jan 15;119(Pt 2):360-9. doi: 10.1242/jcs.02749.

Abstract

The plasma membrane ATPase, Pma1, has remarkable longevity at the cell surface. In contrast to the wild-type protein, the temperature-sensitive mutant Pma1-10 is misfolded and undergoes rapid removal from the cell surface for vacuolar degradation. At the restrictive temperature, Pma1-10 becomes ubiquitylated before or upon arrival at the plasma membrane. Internalization from the plasma membrane and vacuolar degradation of Pma1-10 is dependent on the ubiquitin-interacting motif (UIM) of the epsin Ent1, suggesting recognition of ubiquitylated substrate by the endocytic machinery. Surprisingly, ubiquitylation of Pma1-10 is reversed when its internalization is blocked in an end3 mutant. Under these conditions, Pma1-10 acquires association with detergent-insoluble, glycolipid-enriched complexes (DIGs) which has been suggested to promote stability of wild-type Pma1. Ubiquitylation does not cause DIG exclusion because a Pma1-Ub fusion protein is not significantly excluded from DIGs. We suggest that ubiquitylation of Pma1-10 represents a component of a quality control mechanism that targets the misfolded protein for removal from the plasma membrane. Rapid internalization of Pma1-10 caused by its ubiquitylation may preempt establishment of stabilizing interactions.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Carrier Proteins / metabolism
  • Cell Membrane / metabolism*
  • Endoplasmic Reticulum / metabolism
  • Enzyme Stability
  • Proton-Translocating ATPases / chemistry
  • Proton-Translocating ATPases / genetics
  • Proton-Translocating ATPases / metabolism*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Saccharomyces cerevisiae / cytology
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Ubiquitin / genetics
  • Ubiquitin / metabolism*
  • Vesicular Transport Proteins

Substances

  • Carrier Proteins
  • ENT1 protein, S cerevisiae
  • Recombinant Fusion Proteins
  • Saccharomyces cerevisiae Proteins
  • Ubiquitin
  • Vesicular Transport Proteins
  • PMA1 protein, S cerevisiae
  • Proton-Translocating ATPases