Related Experiment Videos
A novel oncogene, ost, encodes a guanine nucleotide exchange factor that potentially links Rho and Rac signaling
Y Horii1, J F Beeler, K Sakaguchi
1Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
Abstract:
Transfection of NIH3T3 cells with an osteosarcoma expression cDNA library led to the appearance of foci of morphologically transformed cells which were found to harbor a novel oncogene, ost. The ost product was activated by truncation of the N-terminal domain of the ost proto-oncogene and was highly tumorigenic in nude mouse assays. The proto-ost cDNA, isolated subsequently, encodes a predicted protein of 100 kDa containing DH (Db1 homology) and PH (pleckstrin homology) domains. Ost is mainly phosphorylated on serine and localized in the cytoplasm. Purified Ost protein catalyzed guanine nucleotide exchange on RhoA and Cdc42 among the Rho and Ras family members tested, indicating that Ost can activate these small GTP-binding proteins. Ost did not detectably associate with RhoA or Cdc42, but interacted specifically with the GTP-bound form of Rac1, suggesting that Ost can function as an effector of Rac1. These results suggest that Ost is a critical regulatory component which links pathways that signal through Rac1, RhoA and Cdc42. Of the tissues examined, expression of ost was the highest in brain and could be localized to neurons and alpha-tanycytes, suggesting that Ost may participate in axonal transport in these specialized cells.
Insights
A novel oncogene, ost, was discovered in osteosarcoma cells. Activated Ost protein is tumorigenic and regulates small GTP-binding proteins, potentially linking Rac1, RhoA, and Cdc42 signaling pathways.
Area of Science:
- Molecular Biology
- Oncology
- Cell Signaling
Background:
- Osteosarcoma is a primary bone cancer with limited treatment options.
- Identification of novel oncogenes is crucial for understanding cancer development and therapeutic strategies.
Purpose of the Study:
- To identify and characterize novel oncogenes involved in osteosarcoma.
- To elucidate the molecular mechanisms and cellular functions of the identified oncogene, Ost.
Main Methods:
- Transfection of NIH3T3 cells with an osteosarcoma cDNA library.
- Tumorigenicity assays in nude mice.
- Protein characterization, including domain analysis, phosphorylation, and subcellular localization.
- Guanine nucleotide exchange assays and protein-protein interaction studies.
Main Results:
- A novel oncogene, Ost, was identified and found to be highly tumorigenic upon N-terminal truncation.
- Ost protein contains DH and PH domains, is phosphorylated on serine, and localizes to the cytoplasm.
- Ost activates RhoA and Cdc42 and interacts with GTP-bound Rac1, suggesting a role as a Rac1 effector.
- Ost is highly expressed in the brain, particularly in neurons and alpha-tanycytes.
Conclusions:
- Ost is a novel oncogene that plays a significant role in tumorigenesis.
- Ost acts as a critical regulatory component linking Rac1, RhoA, and Cdc42 signaling pathways.
- Ost's expression in the brain suggests a potential role in neuronal function, such as axonal transport.