Human GSTA1-1 reduces c-Jun N-terminal kinase signalling and apoptosis in Caco-2 cells.
The effect of GSTA1-1 (glutathione S-transferase Alpha 1-1) on JNK (c-Jun N-terminal kinase) activation was investigated in Caco-2 cells in which GSTA1 expression increases with degree of confluency, and in MEF3T3 cells with Tet-Off-inducible GSTA1 expression. Comparison of GSTA1 expression in pre-confluent, confluent and 8-day post-confluent Caco-2 cells revealed progressively increasing mRNA and protein levels at later stages of confluency. Exposure of pre-confluent cells to stress conditions including IL-1beta (interleukin-1beta), H2O2 or UV irradiation resulted in marked increases in JNK activity as indicated by c-Jun phosphorylation. However, JNK activation was significantly reduced in post-confluent cells exposed to the same stresses. Western-blot analysis of GSTA1-1 protein bound to JNK protein pulled down from cellular extracts showed approx. 4-fold higher GSTA1-1-JNK complex formation in post-confluent cells compared with pre-confluent cells. However, stress conditions did not alter the amount of GSTA1-1 bound to JNK. The role of GSTA1-1 in JNK suppression was more specifically revealed in Tet-Off-inducible MEF3T3-GSTA1-1 cells in which GSTA1 overexpression significantly reduced phosphorylation of c-Jun following exposure to IL-1beta, H2O2 and UV irradiation. Finally, the incidence of tumour necrosis factor alpha/butyrate-induced apoptosis was significantly higher in pre-confluent Caco-2 cells expressing low levels of GSTA1 compared with post-confluent cells. These results indicate that GSTA1 suppresses activation of JNK signalling by a pro-inflammatory cytokine and oxidative stress and suggests a protective role for GSTA1-1 in JNK-associated apoptosis.
Romero
Laura
L
Department of Biomedical Sciences, University of Guelph, Guelph, ON, Canada N1G 2W1.
Andrews
Kimberly
K
Ng
Lorraine
L
O'Rourke
Kelly
K
Maslen
Ann
A
Kirby
Gordon
G
D016475:3T3 Cells; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D015153:Blotting, Western; D002087:Butyrates / Q000494:pharmacology; D018938:Caco-2 Cells; D004789:Enzyme Activation / Q000187:drug effects / Q000528:radiation effects; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D020287:In Situ Nick-End Labeling; D053583:Interleukin-1beta / Q000494:pharmacology; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D051379:Mice; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D002087:Butyrates; D053583:Interleukin-1beta; D007527:Isoenzymes; D014409:Tumor Necrosis Factor-alpha; D006861:Hydrogen Peroxide; D005982:Glutathione Transferase; C119995:glutathione S-transferase alpha; D048031:JNK Mitogen-Activated Protein Kinases