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Molecular and Cellular Biology, May 2004, p. 4128-4137, Vol. 24, No. 10
0270-7306/04/$08.00+0 DOI: 10.1128/MCB.24.10.4128-4137.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
-Dependent Phosphorylation of c-Jun
Bioscience Division, SRI International, Menlo Park, California 94025,1 Division of Biology, University of California, San Diego, La Jolla, California 921382
Received 13 December 2003/ Returned for modification 23 December 2003/ Accepted 23 February 2004
Hypoxia and anoxia are important microenvironmental stresses that contribute to pathological events such as solid-tumor development. We have been investigating the effects of hypoxia and anoxia on expression of the proto-oncogene c-jun and the regulation of c-Jun/AP-1 transcription factors. In earlier work using genetically manipulated mouse embryo fibroblasts (mEFs), we found a functional relationship among c-jun expression, c-Jun N-terminal phosphorylation, and the presence of hypoxia-inducible factor 1
(HIF-1
), the oxygen-regulated subunit of the HIF-1 transcription factor. Both the induction of c-jun mRNA expression and c-Jun N-terminal phosphorylation in cells exposed to hypoxia or anoxia were found to be dependent on the presence of HIF-1
, but this was not the case in cells exposed to less-severe hypoxia. Here we describe new findings concerning HIF-1-dependent c-Jun N-terminal phosphorylation in cells exposed to hypoxia or anoxia. Specifically, we report that hypoxia-inducible c-Jun N-terminal kinase (JNK) activity, which involves JNKs or stress-activated protein kinases (SAPKs), is dependent on enhanced glucose utilization mediated by HIF-1. These results suggest a model in which hypoxia-inducible JNK activity is connected to oxygen sensing through increased glucose absorption and/or glycolytic activity regulated by the HIF-1 system. We also found that basal threonine and tyrosine phosphorylation (within the TEY motif) of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and the corresponding ERK1/2 activity were defective in hypoxic HIF-1
-null mEFs but not in wild-type mEFs, independently of glucose uptake. Therefore, the activities of both JNKs/SAPKs and ERK1/2 are sensitive to HIF-1-dependent processes in cells exposed to hypoxia or anoxia.
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