In and out of the ER: protein folding, quality control, degradation, and related human diseases

Physiol Rev. 2007 Oct;87(4):1377-408. doi: 10.1152/physrev.00050.2006.


A substantial fraction of eukaryotic gene products are synthesized by ribosomes attached at the cytosolic face of the endoplasmic reticulum (ER) membrane. These polypeptides enter cotranslationally in the ER lumen, which contains resident molecular chaperones and folding factors that assist their maturation. Native proteins are released from the ER lumen and are transported through the secretory pathway to their final intra- or extracellular destination. Folding-defective polypeptides are exported across the ER membrane into the cytosol and destroyed. Cellular and organismal homeostasis relies on a balanced activity of the ER folding, quality control, and degradation machineries as shown by the dozens of human diseases related to defective maturation or disposal of individual polypeptides generated in the ER.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Endoplasmic Reticulum / physiology*
  • Humans
  • Metabolic Diseases / etiology*
  • Metabolic Diseases / physiopathology
  • Molecular Chaperones / physiology
  • Protein Biosynthesis / physiology
  • Protein Folding*


  • Molecular Chaperones