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Ras uses the novel tumor suppressor RASSF1 as an effector to mediate apoptosis
1Department of Cell and Cancer Biology, NCI, National Institutes of Health, Rockville, Maryland 20850-3300, USA.
Abstract:
Although activated Ras proteins are usually associated with driving growth and transformation, they may also induce senescence, apoptosis, and terminal differentiation. The subversion of these anti-neoplastic effects during Ras-dependent tumor development may be as important as the acquisition of the pro-neoplastic effects. None of the currently identified potential Ras effector proteins can satisfactorily explain the apoptotic action of Ras. Consequently, we have sought to identify novel Ras effectors that may be responsible for apoptosis induction. By examining the EST data base, we identified a potential Ras association domain in the tumor suppressor RASSF1. We now show that RASSF1 binds Ras in a GTP-dependent manner, both in vivo and directly in vitro. Moreover, activated Ras enhances and dominant negative Ras inhibits the cell death induced by transient transfection of RASSF1 into 293-T cells. This cell death appears to be apoptotic in nature, as RASSF1-transfected 293-T cells exhibit membrane blebbing and can be rescued by the addition of a caspase inhibitor. Thus, the RASSF1 tumor suppressor may serve as a novel Ras effector that mediates the apoptotic effects of oncogenic Ras.
Insights
Ras proteins can induce cell death, but this effect is not well understood. Researchers identified the RASSF1 tumor suppressor as a novel Ras effector protein that mediates Ras-induced apoptosis, offering new insights into cancer development.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Activated Ras proteins are typically linked to cancer promotion but can also induce anti-neoplastic effects like apoptosis.
- The precise mechanisms by which Ras induces apoptosis are not fully elucidated, and known effector proteins do not adequately explain this function.
Purpose of the Study:
- To identify novel Ras effector proteins responsible for mediating Ras-induced apoptosis.
- To investigate the role of the tumor suppressor RASSF1 as a potential Ras effector in apoptosis induction.
Main Methods:
- Bioinformatic analysis of the EST database to identify potential Ras-binding domains.
- In vivo and in vitro binding assays to confirm RASSF1-Ras interaction.
- Transient transfection assays in 293-T cells to assess RASSF1-induced cell death and its apoptotic nature.
Main Results:
- A potential Ras association domain was identified in the tumor suppressor RASSF1.
- RASSF1 was shown to bind Ras in a GTP-dependent manner, both in vivo and in vitro.
- Activated Ras enhanced RASSF1-induced cell death, while dominant-negative Ras inhibited it. The cell death exhibited characteristics of apoptosis, including membrane blebbing and caspase-dependent inhibition.
Conclusions:
- The RASSF1 tumor suppressor functions as a novel Ras effector.
- RASSF1 mediates the apoptotic effects of oncogenic Ras.
- Understanding this pathway is crucial for comprehending Ras-dependent tumor development and identifying new therapeutic targets.