The multidomain protooncogenic protein c-Cbl binds to tubulin and stabilizes microtubules
Anjali M Teckchandani1, Anna A Birukova, Krisztina Tar
1Department of Microbiology and Immunology, Temple University School of Medicine, 3400 N. Broad Street, Philadelphia, PA 19140, USA.
Abstract:
The protooncogenic protein c-Cbl is known to regulate the actin cytoskeleton. In this study, we present results indicating that c-Cbl can also regulate the microtubular network. We have shown that c-Cbl binds to tubulin and microtubules through its tyrosine kinase binding (TKB) domain. However, the character of the interactions described in this report is novel, since the G306E mutation, which disrupts the ability of c-Cbl's TKB to bind to tyrosine-phosphorylated proteins, does not affect the observed interaction between c-Cbl and microtubules. Furthermore, overexpression of c-Cbl in human pulmonary artery endothelial cells and COS-7 cells leads to microtubule stabilization. We demonstrate that this effect of c-Cbl is mediated by TKB, and, like c-Cbl binding to microtubules, is independent of the ability of TKB to bind to tyrosine-phosphorylated proteins. Finally, we have shown that c-Cbl directly polymerizes microtubules in vitro, and that TKB is necessary and sufficient for this effect of c-Cbl. In this last phenomenon, as well as in the previous ones, the effect of TKB is not sensitive to the inactivating G306E mutation. Overall, the results presented in this report suggest a novel function for c-Cbl-microtubule binding and stabilization.
Insights
The protooncogenic protein c-Cbl regulates microtubule networks by binding to tubulin. This interaction, mediated by its TKB domain, stabilizes microtubules independently of tyrosine phosphorylation.
Area of Science:
- Cell Biology
- Molecular Biology
- Protein Biochemistry
Background:
- The protooncogenic protein c-Cbl is a known regulator of the actin cytoskeleton.
- Its role in microtubule dynamics has not been previously established.
Purpose of the Study:
- To investigate the potential role of c-Cbl in regulating the microtubular network.
- To elucidate the mechanism of c-Cbl interaction with microtubules.
Main Methods:
- Co-immunoprecipitation assays to assess c-Cbl binding to tubulin.
- Microscopy to observe microtubule stabilization in cells overexpressing c-Cbl.
- In vitro microtubule polymerization assays.
Main Results:
- c-Cbl directly binds to tubulin and microtubules via its tyrosine kinase binding (TKB) domain.
- This interaction is independent of the TKB domain's ability to bind tyrosine-phosphorylated proteins, as shown by the G306E mutation.
- Overexpression of c-Cbl stabilizes microtubules in human pulmonary artery endothelial cells and COS-7 cells.
- c-Cbl directly polymerizes microtubules in vitro, with the TKB domain being necessary and sufficient for this activity.
Conclusions:
- c-Cbl possesses a novel function in regulating the microtubular network.
- c-Cbl binds to and stabilizes microtubules through its TKB domain in a manner independent of its tyrosine kinase binding activity.
- These findings suggest a new role for c-Cbl beyond actin cytoskeleton regulation.
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