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Induction of glucose‐regulated proteins in Xenopus laevis A6 Cells
Author(s) -
Winning R. S.,
Heikkila J. J.,
Bols N. C.
Publication year - 1989
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041400208
Subject(s) - xenopus , tunicamycin , biology , deoxyglucose , protein biosynthesis , isoelectric point , microbiology and biotechnology , dithiothreitol , cell culture , biochemistry , gene , unfolded protein response , enzyme , genetics
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.