HuR-dependent SOD2 protein synthesis is an early adaptation to anchorage-independence
Yeon Soo Kim,
Priscilla W. Tang,
Jaclyn E. Welles,
Weihua Pan,
Zaineb Javed,
Amal Taher Elhaw,
Karthikeyan Mythreye,
Scot R. Kimball,
Nadine Hempel
Affiliations
Yeon Soo Kim
Department of Pharmacology, College of Medicine, Pennsylvania State University, Hershey, PA, USA
Priscilla W. Tang
Department of Pharmacology, College of Medicine, Pennsylvania State University, Hershey, PA, USA; Department of Medicine, Division of Hematology/Oncology, UPMC Hillman Cancer Center, University of Pittsburgh, PA, USA
Jaclyn E. Welles
Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey, PA, USA
Weihua Pan
Department of Medicine, Division of Hematology/Oncology, UPMC Hillman Cancer Center, University of Pittsburgh, PA, USA
Zaineb Javed
Department of Pharmacology, College of Medicine, Pennsylvania State University, Hershey, PA, USA; Department of Medicine, Division of Hematology/Oncology, UPMC Hillman Cancer Center, University of Pittsburgh, PA, USA
Amal Taher Elhaw
Department of Pharmacology, College of Medicine, Pennsylvania State University, Hershey, PA, USA; Department of Medicine, Division of Hematology/Oncology, UPMC Hillman Cancer Center, University of Pittsburgh, PA, USA
Karthikeyan Mythreye
Department of Pathology, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
Scot R. Kimball
Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey, PA, USA
Nadine Hempel
Department of Pharmacology, College of Medicine, Pennsylvania State University, Hershey, PA, USA; Department of Medicine, Division of Hematology/Oncology, UPMC Hillman Cancer Center, University of Pittsburgh, PA, USA; Corresponding author. University of Pittsburgh School of Medicine, Division of Hematology/Oncology, UPMC Hillman Cancer Center, Magee-Womens Research Institute, A410, 204 Craft Ave, Pittsburgh, PA, 15213, USA.
During metastasis cancer cells must adapt to survive loss of anchorage and evade anoikis. An important pro-survival adaptation is the ability of metastatic tumor cells to increase their antioxidant capacity and restore cellular redox balance. Although much is known about the transcriptional regulation of antioxidant enzymes in response to stress, how cells acutely adapt to alter antioxidant enzyme levels is less well understood. Using ovarian cancer cells as a model, we demonstrate that an increase in mitochondrial superoxide dismutase SOD2 protein expression is a very early event initiated in response to detachment, an important step during metastasis that has been associated with increased oxidative stress. SOD2 protein synthesis is rapidly induced within 0.5–2 h of matrix detachment, and polyribosome profiling demonstrates an increase in the number of ribosomes bound to SOD2 mRNA, indicating an increase in SOD2 mRNA translation in response to anchorage-independence. Mechanistically, we find that anchorage-independence induces cytosolic accumulation of the RNA binding protein HuR/ELAVL1 and promotes HuR binding to SOD2 mRNA. Using HuR siRNA-mediated knockdown, we show that the presence of HuR is necessary for the increase in SOD2 mRNA association with the heavy polyribosome fraction and consequent nascent SOD2 protein synthesis in anchorage-independence. Cellular detachment also activates the stress-response mitogen-activated kinase p38, which is necessary for HuR-SOD2 mRNA interactions and induction of SOD2 protein output. These findings illustrate a novel translational regulatory mechanism of SOD2 by which ovarian cancer cells rapidly increase their mitochondrial antioxidant capacity as an acute stress response to anchorage-independence.
