title: PERK-dependent regulation of HSP70 expression and the regulation of autophagy.
abstract: The manuscript by Park et al. (Mol. Pharm. 2008; mol.107.042697 / PMID: 18182481) further defines the mechanism(s) by which OSU-03012 (OSU) kills transformed cells. It notes that in PKR-like endoplasmic reticulum kinase null cells (PERK-/-) the lethality of OSU is attenuated. OSU enhances the expression of ATG5 in a PERK-dependent fashion and promotes the ATG5-dependent formation of vesicles containing LC3, followed by a subsequent cleavage of cathepsin B and a cathepsin B-dependent formation of low pH intracellular vesicles; cathepsin B is activated and released into the cytosol, and genetic suppression of cathepsin B or AIF function significantly suppresses cell killing. In parallel, OSU causes PERK-dependent increases in HSP70 expression and decreases in HSP90 and Grp78/BiP expression. Inhibition of HSP70 expression enhances OSU toxicity and over-expression of HSP70 suppresses OSU-induced low pH vesicle formation and lethality. Thus, in this system PERK signaling promotes autophagy, which is causally linked to lysosomal dysfunction, cathepsin activation and cell death. However, in parallel, PERK signaling acts to suppress autophagy and lysosomal dysfunction by increasing the expression of HSP70. These findings may help explain why, in a cell type and stimulus-dependent fashion; autophagy has been noted to act either as a protective or as a toxic signal in cells.
authors.affiliation: Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, USA.
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Park
authors.forename: David T
authors.initials: DT
authors.lastname: Curiel
authors.forename: Costas
authors.initials: C
authors.lastname: Koumenis
authors.forename: Martin
authors.initials: M
authors.lastname: Graf
authors.forename: Ching-Shih
authors.initials: CS
authors.lastname: Chen
authors.forename: Paul B
authors.initials: PB
authors.lastname: Fisher
authors.forename: Steven
authors.initials: S
authors.lastname: Grant
authors.forename: Paul
authors.initials: P
authors.lastname: Dent
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D000071187:Autophagy-Related Protein 5; D002401:Cathepsin B / Q000502:physiology; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000187:drug effects*; D004721:Endoplasmic Reticulum / Q000201:enzymology; D000091342:Endoplasmic Reticulum Chaperone BiP; D005347:Fibroblasts / Q000187:drug effects / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis*; D018841:HSP90 Heat-Shock Proteins / Q000096:biosynthesis; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis; D011720:Pyrazoles / Q000494:pharmacology*; D015398:Signal Transduction; D013449:Sulfonamides / Q000494:pharmacology*; D019892:eIF-2 Kinase / Q000235:genetics / Q000502:physiology*
chemical_list: D000970:Antineoplastic Agents; D051033:Apoptosis Inducing Factor; D000071187:Autophagy-Related Protein 5; D002401:Cathepsin B; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D008869:Microtubule-Associated Proteins; D011720:Pyrazoles; D013449:Sulfonamides; D019892:eIF-2 Kinase; C502778:ATG5 protein, human; C000717247:HSPA5 protein, human; C000717248:Hspa5 protein, mouse; C500894:OSU 03012