ER stress induces the expression of Jpk, which inhibits cell cycle progression in F9 teratocarcinoma cell.
Jopock (Jpk), a transacting factor associated with the position-specific regulatory element of murine Hoxa-7, has shown to induce cell death in both prokaryotic and eukaryotic cells when introduced and overexpressed. Since Jpk protein harbors a transmembrane domain (TM) and a putative endoplasmic reticulum (ER) -retention signal at the N terminus, a subcellular localization of the protein was analyzed after fusing it into the green fluorescent protein (GFP). Both N-term- (Jpk-EGFP) and C-term-fused Jpk (EGFP-Jpk) showed to be localized in the ER when analyzed under the fluorescence microscope after staining the cells with ER- and Mito-Tracker. Through deletion analysis TM turned out to be important for ER localization of Jpk. When flow cytometric analysis was performed, both cells expressing Jpk-EGFP and EGFP-Jpk led cell cycle arrest and subsequent apoptotic cell death. In order to see whether Jpk is expressed during ER stress-mediated apoptosis, F9 cells were treated with DTT, an ER stress inducer. In the presence of 4 mM of DTT, about 50% of cells died strongly expressing Jpk (sevenfold) as well as Grp78, a molecular chaperone, and CHOP-10, a well-known apoptotic protein. When cells were transfected with both pEGFP-Jpk and pJpk-EGFP, cell cycle progression was interrupted compared to those of control cells. In summary, excess ER stress upregulated the expression of Jpk, which seemed to inhibit the cell cycle progression. These results altogether suggest that Jpk could be a useful cell death-triggering molecule applicable for cancer therapy as well as a useful target molecule for the treatment of certain neurodegenerative diseases caused by ER stress.
Kim
Hye Sun
HS
Department of Anatomy, Embryology Lab, Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, C.P.O. Box 8044, Seoul 120-752, Korea.
Kong
Kyoung-Ah
KA
Chung
Hyunjoo
H
Park
Sungdo
S
Kim
Myoung Hee
MH
D000818:Animals; D019556:COS Cells; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology*; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D053595:Embryonic Stem Cells / Q000378:metabolism / Q000473:pathology; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000473:pathology*; D000091342:Endoplasmic Reticulum Chaperone BiP; D020555:GTP-Binding Protein Regulators / Q000096:biosynthesis* / Q000235:genetics; D006131:Growth Inhibitors / Q000096:biosynthesis* / Q000235:genetics; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D018384:Oxidative Stress / Q000235:genetics / Q000502:physiology*; D018243:Teratocarcinoma / Q000378:metabolism* / Q000473:pathology*; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics
D000091342:Endoplasmic Reticulum Chaperone BiP; D020555:GTP-Binding Protein Regulators; D006131:Growth Inhibitors; C000717248:Hspa5 protein, mouse; C519056:Jpk protein, mouse; D008565:Membrane Proteins; D015534:Trans-Activators