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Apoptotic regulation by the Crk adapter protein mediated by interactions with Wee1 and Crm1/exportin
Jesse J Smith1, D Ashley Richardson, Jan Kopf
1Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Abstract:
The adapter protein Crk contains an SH2 domain and two SH3 domains. Through binding of particular ligands to the SH2 domain and the N-terminal SH3 domain, Crk has been implicated in a number of signaling processes, including regulation of cell growth, cell motility, and apoptosis. We report here that the C-terminal SH3 domain, never shown to bind any specific signaling molecules, contains a binding site for the nuclear export factor Crm1. We find that a mutant Crk protein, deficient in Crm1 binding, promotes apoptosis. Moreover, this nuclear export sequence mutant [NES(-) Crk] interacts strongly, through its SH2 domain, with the nuclear tyrosine kinase, Wee1. Collectively, these data suggest that a nuclear population of Crk bound to Wee1 promotes apoptotic death of mammalian cells.
Insights
The C-terminal SH3 domain of Crk binds nuclear export factor Crm1. A mutant Crk lacking this binding site promotes apoptosis by interacting with Wee1 kinase in the nucleus.
Area of Science:
- Cellular signaling
- Molecular biology
- Cancer research
Background:
- The adapter protein Crk plays roles in cell growth, motility, and apoptosis through its SH2 and N-terminal SH3 domains.
- The C-terminal SH3 domain of Crk has not been previously linked to specific molecular interactions.
Purpose of the Study:
- To investigate the function of the C-terminal SH3 domain of Crk.
- To identify binding partners and cellular roles of Crk's C-terminal SH3 domain.
Main Methods:
- Investigated Crk protein interactions using mutant proteins.
- Analyzed the role of Crk in apoptosis.
- Examined Crk's interaction with Crm1 and Wee1.
Main Results:
- Identified Crm1 (nuclear export factor) as a binding partner for the C-terminal SH3 domain of Crk.
- Demonstrated that a Crk mutant unable to bind Crm1 (NES(-) Crk) enhances apoptosis.
- Showed that NES(-) Crk interacts with the nuclear tyrosine kinase Wee1 via its SH2 domain.
Conclusions:
- The C-terminal SH3 domain of Crk mediates binding to Crm1, regulating its nuclear export.
- A nuclear pool of Crk, potentially bound to Wee1, promotes apoptosis in mammalian cells.
- Crk's interaction with Crm1 and Wee1 offers new insights into apoptosis regulation.