title: Heat shock glycoprotein GP50: product of the retinoic acid-inducible J6 gene.
abstract: High intracellular levels of heat shock proteins and enhanced protein glycosylation are two phenomena closely associated with the cellular stress response. GP50 is the major heat-induced glycoprotein in Chinese hamster ovary (CHO) cells; however, GP50 is not well characterized, and its function is unknown. J6 is a gene originally identified in F9 murine teratocarcinoma cells after exposure to retinoic acid. In this study we show that J6 is heat-inducible and codes for a protein that shares characteristics with GP50. Western blotting of CHO cell homogenates, using a J6 polyclonal antibody, showed a single band with a molecular weight identical to that of GP50. Thermotolerant cells showed increased levels of the J6/GP50 protein. Heat-shocked CHO cells also accumulated transiently high levels of J6 mRNA between 2 and 7 h following 10 min at 45 degrees C. These induction kinetics are similar to those for GP50 labeling with D-[3H]mannose and to the activation of major heat shock genes, e.g., hsp70. Hybrid selection of J6 mRNA from CHO cells, followed by in vitro translation, produced a single band on SDS-PAGE with a molecular weight identical to that of deglycosylated GP50. Neither cellular proliferation (exponential growth versus plateau phase) nor the specific heat shock temperature (41.5 degrees C versus 45 degrees C) had significant effects on J6 induction by heat stress. Stress conditions other than hyperthermia, including ethanol, arsenite, and hypoxia, increased J6 mRNA levels. Conversely, J6 mRNA was reduced by quercetin, brefeldin A, okadaic acid, uv, and hydrogen peroxide. Our data support the hypothesis that J6 is a heat shock gene with a gene product identical to the polypeptide moiety of GP50.
authors.affiliation: Department of Medicine, University of Arkansas for Medical Sciences, Arkansas Children's Hospital Research Institute, Little Rock.
authors.forename: K J
authors.initials: KJ
authors.lastname: Henle
authors.forename: S Y
authors.initials: SY
authors.lastname: Wang
authors.forename: W A
authors.initials: WA
authors.lastname: Nagle
authors.forename: C K
authors.initials: CK
authors.lastname: Lumpkin
mesh_terms: D000818:Animals; D018053:Arsenites / Q000494:pharmacology; D020126:Brefeldin A; D016466:CHO Cells; D002455:Cell Division / Q000187:drug effects; D015687:Cell Hypoxia; D006224:Cricetinae; D003517:Cyclopentanes / Q000494:pharmacology; D004988:Ethers, Cyclic / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000528:radiation effects; D006360:Heat-Shock Proteins / Q000096:biosynthesis* / Q000235:genetics; D006358:Hot Temperature; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D008970:Molecular Weight; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D019319:Okadaic Acid; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors; D011794:Quercetin / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D017670:Sodium Compounds / Q000494:pharmacology; D013724:Teratoma; D014158:Transcription, Genetic / Q000187:drug effects / Q000528:radiation effects; D014212:Tretinoin / Q000494:pharmacology*; D014466:Ultraviolet Rays; D014965:X-Rays
chemical_list: D018053:Arsenites; D003517:Cyclopentanes; D004988:Ethers, Cyclic; D006360:Heat-Shock Proteins; D009419:Nerve Tissue Proteins; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D017670:Sodium Compounds; C052914:brain synaptic membrane glycoprotein gp 50; D019319:Okadaic Acid; D020126:Brefeldin A; C017947:sodium arsenite; D014212:Tretinoin; D011794:Quercetin; D006861:Hydrogen Peroxide; D017027:Protein Tyrosine Phosphatases