Endoplasmic reticulum-associated protein degradation (ERAD) is a protein quality 
control mechanism that minimizes the detrimental effects of protein misfolding 
in the secretory pathway. Molecular chaperones and ER lumenal lectins are 
essential components of this process because they maintain the solubility of 
unfolded proteins and can target ERAD substrates to the cytoplasmic proteasome. 
Other factors are likely required to aid in the selection of ERAD substrates, 
and distinct proteinaceous machineries are required for substrate 
retrotranslocation/dislocation from the ER and proteasome targeting. When the 
capacity of the ERAD machinery is exceeded or compromised, multiple degradative 
routes can be enlisted to prevent the detrimental consequences of ERAD substrate 
accumulation, which include cell death and disease.