Activation of c-Jun N-terminal kinase in A549 lung carcinoma cells by sodium dichromate: role of dissociation of apoptosis signal regulating kinase-1 from its physiological inhibitor thioredoxin.
Changes in the components of the Jun N-terminal kinase (JNK) signalling pathway were investigated in human A549 lung carcinoma cells treated with sodium dichromate. Sodium dichromate (100 microM, 0-6h) failed to activate nuclear factor kappa B (NF-kappaB) as determined by a lack of nuclear translocation of p65 but resulted in Jun N-terminal kinase activation as assessed by phospho-Jun N-terminal kinase Western blotting in a dose-dependent (>25 microM) and time-dependent (>1h) manner. In addition, c-Jun, a downstream target of Jun N-terminal kinase signalling was also activated with a similar dose- and time-dependency at the level of both protein expression and degree of phosphorylation. In contrast, sodium dichromate treatment had no effect on levels of phospho-p38. Immunoprecipitation demonstrated that apoptosis signal regulating kinase-1 (ASK-1), an upstream activator of Jun N-terminal kinase was dissociated from its inhibitory partner thioredoxin (Trx) in response to sodium dichromate (100 microM, 4h) treatment. This treatment was also associated with a transient (2h) increase in cytosolic levels of thioredoxin but no nuclear translocation of thioredoxin was observed. In conclusion, sodium dichromate had a stimulatory effect on the Jun N-terminal kinase signalling pathway in A549 cells, resulting in activation of downstream effector molecules. We hypothesise that dissociation of apoptosis signal regulating kinase-1 from thioredoxin may be at least partially responsible for Jun N-terminal kinase activation.
School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. n.hodges@bham.ac.uk
N J
NJ
Hodges
D
D
Smart
A J
AJ
Lee
N A
NA
Lewis
J K
JK
Chipman
D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology; D002470:Cell Survival / Q000187:drug effects; D002840:Chromates / Q000633:toxicity*; D003600:Cytosol / Q000187:drug effects / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D008175:Lung Neoplasms / Q000201:enzymology / Q000473:pathology; D048848:MAP Kinase Kinase Kinase 5; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects*; D013879:Thioredoxins / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D002840:Chromates; D013879:Thioredoxins; C016104:sodium bichromate; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048848:MAP Kinase Kinase Kinase 5; D020930:MAP Kinase Kinase Kinases; C482858:MAP3K5 protein, human