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Mediation of the DCC apoptotic signal by DIP13 alpha
Jiayou Liu1, Fayi Yao, Ruping Wu
1Department of Pathology, Wayne State University, Detroit, Michigan 48201, USA.
Abstract:
DCC (deleted in colorectal cancer) is a candidate tumor suppressor gene. However the function of DCC remains elusive. Previously, we demonstrated that forced expression of DCC induces apoptosis or cell cycle arrest (Chen, Y. Q., Hsieh, J. T., Yao, F., Fang, B., Pong, R. C., Cipriano, S. C. & Krepulat, F. (1999) Oncogene 18, 2747-2754). To delineate the DCC-induced apoptotic pathway, we have identified a protein, DIP13 alpha, which interacts with DCC. The DIP13 alpha protein has a pleckstrin homology domain and a phosphotyrosine binding domain. It interacts with a region on the DCC cytoplasmic domain that is required for the induction of apoptosis. Although ectopic expression of DIP13 alpha alone causes only a slight increase in apoptosis, co-expression of DCC and DIP13 alpha results in an approximately 5-fold increase in apoptosis. Removal of the DCC-interacting domain on DIP13 alpha abolishes its ability to enhance DCC-induced apoptosis. Inhibition of endogenous DIP13 alpha expression by small interfering RNA blocks DCC-induced apoptosis. Our data suggest that DIP13 alpha is a mediator of the DCC apoptotic pathway.
Insights
Deleted in colorectal cancer (DCC) is a tumor suppressor. Researchers found DIP13 alpha interacts with DCC, mediating DCC-induced apoptosis and cell cycle arrest.
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Biology
Background:
- The Deleted in Colorectal Cancer (DCC) gene is a candidate tumor suppressor, but its precise function remains unclear.
- Previous studies indicated that DCC expression can induce apoptosis or cell cycle arrest.
- Understanding the molecular mechanisms underlying DCC's tumor suppressor activity is crucial.
Purpose of the Study:
- To identify proteins that interact with DCC and mediate its apoptotic function.
- To elucidate the role of the identified protein in the DCC-induced apoptotic pathway.
- To investigate the functional interaction between DCC and DIP13 alpha.
Main Methods:
- Protein-protein interaction studies to identify DCC-binding partners.
- Expression analysis of DCC and identified interacting proteins.
- Apoptosis assays, including ectopic expression and small interfering RNA (siRNA) knockdown.
- Site-directed mutagenesis to map interaction domains.
Main Results:
- A protein, DIP13 alpha, containing a pleckstrin homology domain and a phosphotyrosine binding domain, was identified as interacting with DCC.
- DIP13 alpha interacts with a DCC cytoplasmic domain region critical for apoptosis induction.
- Co-expression of DCC and DIP13 alpha significantly enhanced apoptosis (approximately 5-fold) compared to DIP13 alpha alone.
- Disruption of the DCC-binding domain on DIP13 alpha abolished its ability to enhance DCC-induced apoptosis.
- Inhibition of endogenous DIP13 alpha using siRNA blocked DCC-induced apoptosis.
Conclusions:
- DIP13 alpha is a key mediator in the apoptotic pathway induced by the Deleted in Colorectal Cancer (DCC) tumor suppressor.
- The interaction between DCC and DIP13 alpha is essential for DCC's tumor-suppressive function via apoptosis.
- These findings provide new insights into the molecular mechanisms of DCC in cancer suppression.