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Distinct cellular effects and interactions of the Rho-family GTPase TC10
C L Neudauer1, G Joberty, N Tatsis
1Center for Cell Signaling University of Virginia Charlottesville, Virginia, 22908, USA.
Background:
Rho-family GTPases have central roles in cytoskeletal organization, proliferation, differentiation and apoptosis. Multiple factors possessing overlapping specificities for Rho GTPases have been identified. The Rho GTPases Cdc42 and Rac share many regulators and effectors, yet produce different phenotypes when expressed as gain-of-function mutants in cells. The Rho-family member TC10 has remained almost completely uncharacterized, so it was of interest to determine whether TC10 has unique cellular effects and interacts with the same targets as Cdc42 and Rac.
Results:
A gain-of-function TC10 mutant protein expressed in fibroblasts induced cell rounding, loss of stress fibers and formation of peripheral extensions. The extensions were longer than those induced by the analogous Cdc42 mutant protein. Cells expressing TC10 also possessed fewer membrane ruffles and stress fibers than those expressing Cdc42. TC10 mRNA was most highly expressed in heart and skeletal muscle. The GTPase activity of TC10 was lower than that of Cdc42, and TC10 possessed a lower affinity for, but greater responsiveness to, the p50Rho GTPase-activating protein (p50RhoGAP) than did Cdc42. TC10 stimulated Jun N-terminal kinase (JNK) and p21-activated kinase (PAK) activities and interacted with a set of effectors (alpha-, beta- and gammaPAK, MRCKalpha/beta, MLK2, N-WASP and MSE55) that overlaps with those for Cdc42 and Rac. TC10 did not interact with MLK3 or WASP, and interacted only weakly with ACK-1.
Conclusions:
TC10 possesses distinct features, but exhibits a phenotype most closely related to that of Cdc42. It interacts with a similar subset of effectors to Cdc42 but not with MLK3, WASP or ACK-1. It is regulated differentially by p50RhoGAP.
Insights
The Rho-family GTPase TC10 influences cell shape and cytoskeletal organization, showing distinct effects from Cdc42 and Rac. TC10 interacts with similar effectors to Cdc42 but is regulated differently by p50RhoGAP.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Rho-family GTPases are crucial for cell functions like cytoskeletal organization and proliferation.
- Cdc42 and Rac, though sharing regulators, induce different cellular phenotypes.
- TC10, a Rho-family member, remained largely uncharacterized, prompting investigation into its unique cellular effects and interactions.
Purpose of the Study:
- To investigate the unique cellular effects of TC10.
- To determine if TC10 interacts with the same molecular targets as Cdc42 and Rac.
- To characterize the regulation and effector interactions of TC10.
Main Methods:
- Expression of a gain-of-function TC10 mutant in fibroblasts.
- Analysis of cellular morphology, including cell rounding, stress fibers, and peripheral extensions.
- Assessing GTPase activity, affinity for p50RhoGAP, and interactions with known Cdc42/Rac effectors.
Main Results:
- TC10 gain-of-function induced cell rounding and peripheral extensions, distinct from Cdc42.
- TC10 expression led to fewer membrane ruffles and stress fibers compared to Cdc42.
- TC10 showed lower GTPase activity and differential regulation by p50RhoGAP compared to Cdc42, while interacting with a similar subset of effectors.
Conclusions:
- TC10 exhibits distinct cellular effects, most closely resembling Cdc42.
- TC10 interacts with a subset of Cdc42 effectors but not MLK3, WASP, or ACK-1.
- TC10's regulation by p50RhoGAP differs from that of Cdc42.