Molecular Biology Reports

, Volume 26, Issue 1, pp 125–130

Endoplasmic reticulum degradation. Reverse protein transport and its end in the proteasome

  • Richard K. Plemper
  • Dieter H. Wolf

DOI: 10.1023/A:1006913215484

Cite this article as:
Plemper, R.K. & Wolf, D.H. Mol Biol Rep (1999) 26: 125. doi:10.1023/A:1006913215484


Degradation of misfolded or unassembled proteins of the secretory pathway is an essential function of the quality control system of the Endoplasmic Reticulum (ER). Using yeast as a model organism we show that a mutated and therefore misfolded soluble lumenal protein carboxypeptidase yscY (CPY*), and a polytopic membrane protein, the ATP-binding cassette transporter Pdr5 (Pdr5*), are retrograde transported out of the ER and degraded via the cytoplasmic ubiquitin-proteasome system. Retrograde transport depends on an intact Sec61 translocon. Complete import of CPY* into the lumen of the ER requests a new targeting mechanism for retrograde transport of the malfolded enzyme through the Sec61 channel to occur. For soluble CPY*, but not for the polytopic membrane protein Pdr5* action of the ER-lumenal Hsp70 chaperone Kar2 is necessary to deliver the protein to the ubiquitin-proteasome machinery. Polyubiquitination of CPY* and Pdr5* by the ubiquitin conjugating enzymes Ubc6 and Ubc7 is crucial for degradation to occur. Also transport of CPY* out of the ER-lumen depends on ubiquitination. Newly discovered proteins of the ER membrane, Der1, Der3/Hrd1, and Hrd3 are specifically involved in the retrograde transport processes.

endoplasmic reticulumER associated degradationproteasomeyeast Saccharomyces cerevisiae

Copyright information

© Kluwer Academic Publishers 1999

Authors and Affiliations

  • Richard K. Plemper
    • 1
  • Dieter H. Wolf
    • 1
  1. 1.Institut für BiochemieUniversität StuttgartStuttgartGermany