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Updated: Aug 18, 2025
RhoC GTPase Activation Assay
Published on: August 22, 2010
Characterization of mutant versions of the R-RAS2/TC21 GTPase found in tumors
Laura Clavaín1,2,3, Isabel Fernández-Pisonero1,2,3, Nieves Movilla4
1Molecular Mechanisms of Cancer Program, Centro de Investigación del Cáncer, CSIC and University of Salamanca, 37007, Salamanca, Spain.
Abstract:
The R-RAS2 GTP hydrolase (GTPase) (also known as TC21) has been traditionally considered quite similar to classical RAS proteins at the regulatory and signaling levels. Recently, a long-tail hotspot mutation targeting the R-RAS2/TC21 Gln72 residue (Q72L) was identified as a potent oncogenic driver. Additional point mutations were also found in other tumors at low frequencies. Despite this, little information is available regarding the transforming role of these mutant versions and their relevance for the tumorigenic properties of already-transformed cancer cells. Here, we report that many of the RRAS2 mutations found in human cancers are highly transforming when expressed in immortalized cell lines. Moreover, the expression of endogenous R-RAS2Q72L is important for maintaining optimal levels of PI3K and ERK activities as well as for the adhesion, invasiveness, proliferation, and mitochondrial respiration of ovarian and breast cancer cell lines. Endogenous R-RAS2Q72L also regulates gene expression programs linked to both cell adhesion and inflammatory/immune-related responses. Endogenous R-RAS2Q72L is also quite relevant for the in vivo tumorigenic activity of these cells. This dependency is observed even though these cancer cell lines bear concurrent gain-of-function mutations in genes encoding RAS signaling elements. Finally, we show that endogenous R-RAS2, unlike the case of classical RAS proteins, specifically localizes in focal adhesions. Collectively, these results indicate that gain-of-function mutations of R-RAS2/TC21 play roles in tumor initiation and maintenance that are not fully redundant with those regulated by classical RAS oncoproteins.
Insights
Gain-of-function mutations in R-RAS2 GTPase (TC21), particularly Q72L, drive cancer by regulating key cell functions. These R-RAS2 mutations are crucial for tumor growth and are not redundant with classical RAS proteins.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- R-RAS2 GTPase (TC21) was traditionally viewed as similar to classical RAS proteins.
- A Q72L mutation in R-RAS2/TC21 is a newly identified potent oncogenic driver.
- Limited information exists on the oncogenic roles of R-RAS2 mutations in cancer progression.
Purpose of the Study:
- To investigate the transforming potential of R-RAS2 mutations found in human cancers.
- To determine the role of endogenous R-RAS2(Q72L) in maintaining cancer cell phenotypes and tumorigenicity.
- To elucidate the subcellular localization of R-RAS2 and its functional implications.
Main Methods:
- Expression of RRAS2 mutations in immortalized cell lines.
- Analysis of PI3K and ERK signaling pathway activities.
- Assessment of cell adhesion, invasiveness, proliferation, and mitochondrial respiration.
- Gene expression profiling.
- In vivo tumorigenicity assays.
- Immunofluorescence microscopy to determine subcellular localization.
Main Results:
- Many RRAS2 mutations identified in human cancers exhibit high transforming activity in cell lines.
- Endogenous R-RAS2(Q72L) is essential for maintaining PI3K/ERK activity, cell adhesion, invasiveness, proliferation, and mitochondrial respiration in ovarian and breast cancer cells.
- R-RAS2(Q72L) regulates gene expression programs related to cell adhesion and inflammatory/immune responses.
- Endogenous R-RAS2(Q72L) is critical for in vivo tumor formation, even in the presence of other RAS pathway mutations.
- Unlike classical RAS proteins, endogenous R-RAS2 specifically localizes to focal adhesions.
Conclusions:
- Gain-of-function R-RAS2/TC21 mutations play significant roles in tumor initiation and maintenance.
- The functions of R-RAS2 mutations are not entirely redundant with those of classical RAS oncoproteins.
- R-RAS2's specific localization to focal adhesions may contribute to its unique oncogenic functions.
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