Table 1 of
Gorbatyuk, Mol Vis 2013; 19:1985-1998. Table 1 of
Gorbatyuk, Mol Vis 2013; 19:1985-1998.
Table 1. List of UPR markers.
| PERK | Pancreatic ER kinase (PKR)-like ER kinase | PERK signaling. Once activated phosphorylates eIf2α and blocks general protein synthesis. |
|---|---|---|
| IRE1 | Inositol-requiring kinase/endoRNase 1 | IRE1 signaling. Once activated IRE1 removes a 26-nucleotide intron from the XBP1 mRNA. May activate the c-Jun N-terminal kinase (JNK) pathway. |
| ATF6 | Activating transcription factor 6 | ATF6 signaling. Once activated translocates to the Golgi where it is cleaved by proteases. Active ATF6 translocates to the nucleus and induces genes with ER stress response element (ERSE) such as GRP78. GRP94, CHOP, XBP1. |
| GRP78 or Bip | Glucose-regulated protein 78 or binding immunoglobulin protein | Key player of PERK, ATF6, IRE1 signaling. On accumulation of unfolded proteins dissociates from the three receptors PERK, ATF6 and IRE1 leading to their activation and triggers the UPR. |
| eIF2α | Eukaryotic transcription factor 2α | PERK signaling. Phosphorylation of eIF2α by activated PERK blocks protein synthesis by attenuating of capor-eIF2α-dependent translation. |
| ATF4 | Activating transcription factor 4 | PERK signaling. Carries internal ribosomal entry site (IRES) in five prime untranslated region and escapes the eIF2α-dependent translation block. Induces expression of genes involved in amino acid metabolism, redox reactions, stress response, protein secretion and pro-apoptotic CHOP protein. |
| CHOP | C/EBP homologous protein or GADD153 (Growth Arrest and DNA Damage inducible gene 153) | PERK, ATF6, IRE1 signaling. Pro-apoptotic protein. Important element of the switch from pro-survival to pro-death signaling. Apoptosis-induced targeted genes are Bcl2 (downregulation), GADD34, TRB3, Ero1. |
| GADD34 | Growth Arrest and DNA Damage inducible gene 34. a protein phosphatase 1 (PP1)-interacting protein | PERK signaling. Causes PP1 to dephosphorylate eIF2α and thus release the translational block. Expression of GADD34 correlates with apoptosis. |
| XBP1 | X box-binding protein 1, transcription factor | IRE1 signaling. Undergone by splicing (26bp) to be active. Translocates to the nucleus and controls the transcription of chaperones |
| P58IPK | Interferon-induced protein kinase PKR, Hsp40 family member (DnaJC3) | IRE1 signaling. Binds and inhibits PERK providing negative feedback loop and relieves the PERK-mediated translation block. |