HIF-1α mRNA and protein upregulation involves Rho GTPase expression during hypoxia in renal cell carcinoma
- 1 June 2003
- journal article
- Published by The Company of Biologists in Journal of Cell Science
- Vol. 116 (11), 2247-2260
- https://doi.org/10.1242/jcs.00427
Abstract
The small G proteins of the Rho family are involved in reorganization of the actin cytoskeleton, cell migration and in the regulation of gene transcription. Hypoxia-induced ATP depletion results in the disruption of actin organization which could affect Rho functions. In solid tumors, regions with low oxygen tension stimulate angiogenesis in order to increase oxygen and nutrient supply. This process is mediated by stabilization of the transcriptional factor hypoxia inducible factor 1 (HIF-1), which increases vascular endothelial growth factor (VEGF) production. In this study, we investigated the activities of Rho proteins, which are key regulators of cytoskeleton organization during hypoxia in renal cell carcinoma. Caki-1 cells were exposed to hypoxia (1% O2) and exhibited increased Cdc42, Rac1 and RhoA protein expression. Immunoprecipitation of metabolically labelled RhoA showed that overexpression was at least due to neo-synthesis. The Rho GTPases overexpressed during hypoxia were mainly located at membranes and pull-down assays demonstrated that they were active since they bound GTP. RT-PCR analysis indicated that the increase in RhoA protein expression was also reflected at the mRNA level. Overexpression and activation of Rho proteins were downstream of, and dependent on, the production of reactive oxygen species (ROS) since, in the presence of an inhibitor, both the rise of ROS and upregulation of Rho proteins were abolished. Importantly, preincubation of cells with the toxin C3, which inhibits RhoA, reduced HIF-1α protein accumulation by 84% during hypoxia. Together, these results support a model where ROS upregulate Rho protein expression and where active RhoA is required for HIF-1α accumulation during hypoxia.Keywords
This publication has 48 references indexed in Scilit:
- Role of Phosphoinositide 3-Kinase in the Aggressive Tumor Growth of HT1080 Human Fibrosarcoma CellsMolecular and Cellular Biology, 2001
- Rac1 Activity Is Required for the Activation of Hypoxia-inducible Factor 1Published by Elsevier BV ,2001
- Hypoxia promotes oxidative base modifications in the pulmonary artery endothelial cell VEGF geneThe FASEB Journal, 2001
- Dual mechanism of vascular endothelial growth factor upregulation by hypoxia in human hepatocellular carcinomaGut, 2001
- Identification of Alternative Spliced Variants of Human Hypoxia-inducible Factor-1αPublished by Elsevier BV ,2000
- Antagonising the expression of VEGF in pathological angiogenesisExpert Opinion on Therapeutic Patents, 1998
- Hypoxia Response Elements in the Aldolase A, Enolase 1, and Lactate Dehydrogenase A Gene Promoters Contain Essential Binding Sites for Hypoxia-inducible Factor 1Published by Elsevier BV ,1996
- Regulation of cytoskeletal functions by Rho small GTP-binding proteins in normal and cancer cellsCanadian Journal of Physiology and Pharmacology, 1996
- Purification and Characterization of Hypoxia-inducible Factor 1Journal of Biological Chemistry, 1995
- The small GTP-binding protein rho regulates the assembly of focal adhesions and actin stress fibers in response to growth factorsCell, 1992