Induction of glucose-regulated proteins in Xenopus laevis A6 cells.
We have characterized the induction of glucose-regulated proteins (GRPs) in Xenopus laevis A6 cells, a kidney epithelial cell line. Exposure of A6 cells to medium in which 2-deoxyglucose replaced galactose resulted in enhanced synthesis of two proteins at 78 and 98 kd. The 78 kd protein was determined by two-dimensional PAGE to consist of two isoelectric variants with pls of 5.3 and 5.2 whereas the 98 kd protein resolved into a single spot with a pl of 5.1. The 78 kd protein cross-reacted with antiserum against chicken GRP78 (glucose-regulated protein), suggesting that the Xenopus protein shares homology with a previously characterized GRP. This was supported by the finding that a rat GRP78 probe hybridized with a 2-deoxyglucose-inducible mRNA. Synthesis of the two proteins was also induced by tunicamycin, 2-deoxygalactose, and dithiothreitol. However, the GRPs were not induced by glucosamine or calcium ionophore A23187 at concentrations and exposure periods that have previously been shown to elicit a GRP response in mammalian and avian cells. Enhanced synthesis of the two GRPs by 2-deoxyglucose was transient, reaching maximal levels by 12-24 h and decreasing to near control levels by 48 h. Removal of the stress at the point of peak synthesis resulted in decreased synthesis of both proteins within 6 h and a return to control levels within 24 h of recovery. These data suggest that Xenopus cells have a GRP response that is similar, but not identical, to that found in mammalian cells.
Winning
R S
RS
Department of Biology, University of Waterloo, Ontario, Canada.
Heikkila
J J
JJ
Bols
N C
NC
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002460:Cell Line; D003847:Deoxyglucose / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015180:Electrophoresis, Gel, Two-Dimensional; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D005643:Fucose / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D005944:Glucosamine / Q000494:pharmacology; D018840:HSP70 Heat-Shock Proteins; D015151:Immunoblotting; D007668:Kidney / Q000166:cytology* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D014415:Tunicamycin / Q000494:pharmacology; D014982:Xenopus laevis
D018840:HSP70 Heat-Shock Proteins; D008565:Membrane Proteins; C018551:glucose-regulated proteins; D014415:Tunicamycin; D005643:Fucose; D000001:Calcimycin; D003847:Deoxyglucose; D005944:Glucosamine; D004229:Dithiothreitol