17 beta-estradiol-induced increases in glucose-regulated protein 78kD and 94kD protect human breast cancer T47-D cells from thermal injury.
Heat shock alters the susceptibility of tumor cells to chemotherapeutic agents. We conducted experiments to study the regulation of expression of heat shock proteins (HSP) in 17 beta-estradiol-treated T47-D cells, a human breast cancer cell line. Cells exposed to 17 beta-estradiol for 24-48 h displayed increased expression of glucose regulated protein 78kD (GRP-78) and 94kD (GRP-94), as shown by [35S]methionine incorporation and Western blotting experiments. The increase was time (5 h to 48 h)-dependent at 1 nM and 1 microM 17 beta-estradiol. Cells overexpressing GRP-78 and -94 after treatment with 17 beta-estradiol displayed resistance against heat shock (47 degrees C for 50 min)-induced death. Removal of external Ca2+ or treatment of cells with BAPTA (a Ca2+ chelator) did not alter the synthesis of GRP-78 and -94, suggesting that the 17 beta-estradiol effect on the synthesis of GRP-78 and -94 is Ca(2+)-independent. In addition, exposure of cells to 17 beta-estradiol up to 100 microM did not increase [Ca2+]i, which further supports the view that the estrogen-induced GRPs are not regulated by [Ca2+]i. Treatment with H89 (a protein kinase A inhibitor, 1 microM, 30 min) or GF-109203X (a protein kinase C inhibitor, 1 microM, 30 min) also did not change the GRP synthesis, indicating that protein kinase A and C are not involved in regulation of GRP synthesis.
Kiang
J G
JG
Department of Clinical Physiology, Walter Reed Army Institute of Research, Washington, DC 20307-5100, USA. Dr._Juliann_Kiang@WRSMTP-ccmail.army.mil
Gist
I D
ID
Tsokos
G C
GC
D002118:Calcium / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D004958:Estradiol / Q000494:pharmacology*; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis*; D006358:Hot Temperature; D006801:Humans; D008565:Membrane Proteins / Q000096:biosynthesis*; D011493:Protein Kinase C / Q000502:physiology; D014407:Tumor Cells, Cultured
D018840:HSP70 Heat-Shock Proteins; D008565:Membrane Proteins; C018551:glucose-regulated proteins; D004958:Estradiol; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D002118:Calcium