A novel role for calcium and membrane-binding proteins in regulation of respiratory burst in Ehrlich ascites tumour cells.
The effect of the signals, dexamethasone and phorbol-ester (TPA) and their interplay on the respiratory burst in Ehrlich ascites tumour (EAT) cells and the effect of this interplay has on the phosphorylation state and thus function of EAT cell cytosolic calcium and membrane-binding proteins (CaMBPs) was studied. Dexamethasone (1 mg/kg body weight) inhibited basal and TPA-activated EAT cell respiratory burst. CaMBPs isolated from EAT cells under the influence of either or both signals by a membrane-affinity binding technique showed similar profiles on SDS-PAGE. Autoradiography showed that only an 11,000 M(r) protein is subject to phosphorylation and that dexamethasone brings down the extent of phosphorylation of CaMBPs isolated from control and TPA-treated EAT cells. Phosphorylated CaMBPs from control and TPA-treated cells could activate the respiratory burst in Triton-permeabilized EAT cells in a dose-dependent manner (four- and six-fold activations, respectively, at 16 micrograms protein concentration) when included in the assay, whereas dephosphorylated CaMBPs from EAT cells from mice treated with dexamethasone alone, or later activated with TPA, could not. A phosphatase activity was detected in EAT cell cytosol receiving the dual-signal, dexamethasone and TPA.
Department of Biochemistry, University of Mysore, India.
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Sharma
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Salimath
D000818:Animals; D017302:Annexins / Q000302:isolation & purification / Q000502:physiology*; D002118:Calcium / Q000502:physiology*; D002286:Carcinoma, Ehrlich Tumor / Q000473:pathology*; D003907:Dexamethasone / Q000494:pharmacology; D051379:Mice; D009363:Neoplasm Proteins / Q000302:isolation & purification / Q000502:physiology*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D016897:Respiratory Burst / Q000187:drug effects / Q000502:physiology*; D013482:Superoxide Dismutase / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects
D017302:Annexins; D009363:Neoplasm Proteins; D003907:Dexamethasone; D013482:Superoxide Dismutase; D011494:Protein Kinases; D010749:Phosphoprotein Phosphatases; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium