1. Degradation of insoluble and soluble ER glycoproteins.
Degradation of insoluble and soluble ER glycoproteins. Some misfolded glycoproteins form insoluble aggregates or ordered polymers in the ER, and UGGT1-mediated modification of the glucosylation status (monoglucosylated or unglucosylated) might play a role in limiting insolubility. The soluble-to-insoluble transition might occur via compartmentalization in the ERAC, and insoluble substrates might also be resolubilized. Soluble forms of both luminal and transmembrane glycoproteins tend to be degraded through ERAD, whereas insoluble forms tend to be degraded via autophagy, although the mechanism by which insoluble ER proteins get to the lysosome is not entirely clear. Luminal insoluble glycoproteins might be packaged into EDEM1-containing vesicles (EDEMosomes) and transported to the lysosome. Transmembrane insoluble glycoproteins could accumulate in the aggresome and then be degraded by the proteasome, or be targeted by an unknown mechanism to the lysosome for degradation.
Sean P. Ferris et al. Dis. Model. Mech. 2014;7:
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