Figure 1.

Schematic representation of the different branches of the proteostasis network, divided into trafficking, folding and degradation. (A) Trafficking: Protein prenylation involves the transfer of either a farnesyl or a geranylgeranyl moiety to the C-terminal cysteine(s) of the target protein by farnesyltransferase (FTase) and geranylgeranyltransferase (GGTase-I), respectively. Chaperones involved in regulation of this prenylation process and trafficking of prenylated proteins, include AIPL1, PDE6D, and UNC119 (depicted in green). (B) Folding: Two responses that are activated upon protein misfolding are the unfolded protein response (UPR) and the heat shock response (HSR). Both responses result in enhanced expression of chaperones (depicted in green) in order to restore the correct folding of proteins. (C) Degradation: ER-associated degradation (ERAD) results in the degradation of proteins by the ubiquitin–proteasome system (UPS). Another pathway of protein degradation is autophagy. Background colors in figure (green, blue, and red) correspond with background colors of Table 1.