Reovirus Oncolysis: The Ras/RalGEF/p38 Pathway Dictates Host Cell Permissiveness to Reovirus Infection

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 101; no. 30; pp. 11099 - 11104
• Main Authors: Norman, Kara L., Hirasawa, Kensuke, Yang, An-Dao, Shields, Michael A., Patrick W. K. Lee, Joklik, Wolfgang K.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 27.07.2004; National Acad Sciences
• Subjects: 3T3 Cells; Animals; Biological Sciences; Cancer; Cell lines; DNA, Viral - genetics; GTP Phosphohydrolases - metabolism; Infections; L Cells; Medical research; Medical treatment; Mice; Mitogen-Activated Protein Kinases - metabolism; NIH 3T3 cells; Oncology; p38 Mitogen-Activated Protein Kinases; Permissiveness; Protein synthesis; ral Guanine Nucleotide Exchange Factor - metabolism; ras Proteins - metabolism; Reoviridae; Reoviridae - genetics; Reoviridae - pathogenicity; Reoviridae - physiology; Reoviridae infections; Reoviridae Infections - physiopathology; Reovirus; Reverse Transcriptase Polymerase Chain Reaction; RNA; Signal Transduction - physiology; Transfection; Virus Replication; Viruses
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0404310101

Reovirus is a benign human virus that was recently found to have oncolytic properties and is currently in clinical trials as a potential cancer therapy. We have previously demonstrated that activation of Ras signaling, a common event in cancer, renders cells susceptible to reovirus oncolysis. In this study, we investigate which elements downstream of Ras are important in reovirus infection. By using a panel of NIH 3T3 cells transformed with activated Ras mutated in the effector-binding domain, we found that only the RasV12G37 mutant, which was unable to signal to Raf or phosphatidylinositol 3-kinase but retained signaling capability to guanine nucleotide-exchange factors (GEFs) for the small G protein, Ral (known as RalGEFs), was permissive to reovirus. Expression of the activated mutant of the RalGEF, Rlf, also allowed reovirus replication. Specific inhibition of the Ral pathway by using dominant-negative RalA rendered normally permissive H-Ras cells (cells expressing activated Ras) resistant to reovirus. To further identify elements downstream of RalGEF that promote reovirus infection, we used chemical inhibitors of the downstream signaling elements p38 and JNK. We found that reovirus infection was blocked in the presence of the p38 inhibitor but not the JNK inhibitor. Together, these results implicate a Ras/RalGEF/p38 pathway in the regulation of reovirus replication and oncolysis.