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A novel strategy for specifically down-regulating individual Rho GTPase activity in tumor cells
Lei Wang1, Linda Yang, Yongneng Luo
1Division of Experimental Hematology and Molecular Developmental Biology Program, Children's Hospital Research Foundation, University of Cincinnati, Cincinnati, Ohio 45229, USA.
Abstract:
The Rho family GTPases RhoA, RhoB, and RhoC regulate the actin cytoskeleton, cell movement, and cell growth. Unlike Ras, up-regulation or overexpression of these GDP/GTP binding molecular switches, but not activating point mutations, has been associated with human cancer. Although they share over 85% sequence identity, RhoA, RhoB, and RhoC appear to play distinct roles in cell transformation and metastasis. In NIH 3T3 cells, RhoA or RhoB overexpression causes transformation whereas RhoC increases the cell migration rate. To specifically target RhoA, RhoB, or RhoC function, we have generated a set of chimeric molecules by fusing the RhoGAP domain of p190, a GTPase-activating protein that accelerates the intrinsic GTPase activity of all three Rho GTPases, with the C-terminal hypervariable sequences of RhoA, RhoB, or RhoC. The p190-Rho chimeras were active as GTPase-activating proteins toward RhoA in vitro, co-localized with the respective active Rho proteins, and specifically down-regulated Rho protein activities in cells depending on which Rho GTPase sequences were included in the chimeras. In particular, the p190-RhoA-C chimera specifically inhibited RhoA-induced transformation whereas p190-RhoC-C specifically reversed the migration phenotype induced by the active RhoC. In human mammary epithelial-RhoC breast cancer cells, p190-RhoC-C, but not p190-RhoA-C or p190-RhoB-C, reversed the anchorage-independent growth and invasion phenotypes caused by RhoC overexpression. In the highly metastatic A375-M human melanoma cells, p190-RhoC-C specifically reversed migration, and invasion phenotypes attributed to RhoC up-regulation. Thus, we have developed a novel strategy utilizing RhoGAP-Rho chimeras to specifically down-regulate individual Rho activity and demonstrate that this approach may be applied to multiple human tumor cells to reverse the growth and/or invasion phenotypes associated with disregulation of a distinct subtype of Rho GTPase.
Insights
Researchers developed novel RhoGAP-Rho chimeras to specifically target Rho GTPases involved in cancer. These chimeras effectively reversed cancer cell growth and migration phenotypes by down-regulating distinct Rho subtypes, offering a new therapeutic strategy.
Area of Science:
- Molecular Biology
- Cell Biology
- Oncology
Background:
- Rho family GTPases (RhoA, RhoB, RhoC) regulate crucial cellular processes like actin cytoskeleton dynamics, cell movement, and growth.
- Overexpression of Rho GTPases, unlike activating mutations, is linked to human cancers, suggesting distinct roles in tumorigenesis and metastasis.
- RhoA/RhoB overexpression induces cell transformation, while RhoC enhances migration, highlighting subtype-specific functions.
Purpose of the Study:
- To develop a novel strategy for specifically targeting individual Rho GTPase functions in cancer.
- To create and validate RhoGAP-Rho chimeras capable of selectively inhibiting RhoA, RhoB, or RhoC activity.
- To assess the efficacy of these chimeras in reversing cancer-associated phenotypes in relevant cell models.
Main Methods:
- Generation of chimeric molecules by fusing the p190 RhoGAP domain with RhoA, RhoB, or RhoC C-terminal hypervariable sequences.
- In vitro characterization of chimeras' GTPase-activating protein (GAP) activity towards RhoA.
- In cellulo validation of chimera-mediated Rho GTPase down-regulation and phenotypic reversal in cancer cell lines (NIH 3T3, human mammary epithelial, A375-M melanoma).
Main Results:
- p190-Rho chimeras exhibited specific GAP activity and co-localized with their respective active Rho proteins.
- Chimeras specifically down-regulated target Rho GTPase activities, with p190-RhoA-C inhibiting transformation and p190-RhoC-C reversing RhoC-induced migration.
- In human breast cancer and melanoma cells, p190-RhoC-C reversed RhoC overexpression-induced anchorage-independent growth, invasion, and migration phenotypes.
Conclusions:
- Novel RhoGAP-Rho chimeras provide a strategy for specifically down-regulating individual Rho GTPase activities.
- This approach demonstrates potential for reversing cancer cell growth and invasion phenotypes driven by distinct Rho GTPase subtypes.
- The findings support the therapeutic application of subtype-specific Rho GTPase inhibition in human cancers.