B-Catenin Stability in Breast Cancer
Abstract
Beta Catenin is a critical signaling molecule that participates in differentiation and proliferation pathways. Cytoplasmic beta-catenin participates in intracellular signaling via the LEF/TCF family of transcriptional activators. Mutations that lead directly or indirectly to stabilization of cytoplasmic beta-catenin are oncogenic. We hypothesize that the cytoplasmic, signaling" pool of Beta-catenin is regulated at the level of protein stability by the ubiquitin- proteasome degradation pathway. The tumor suppressor adenomatous polyposis coli (APC) gene product has been reported to associate with beta-catenin and effect its down-regulation by an unknown mechanism. We hypothesize that APC is an ubiquitin-ligase (E3 enzyme) that helps ubiquitinate beta-catenin and target it to the proteasome for degradation. We propose to test our hypotheses in vitro using cell-free reconstitution assays. In vivo studies include transient transfections with APC constructs that possess or lack the free-cysteine HECT consensus which is characteristic of ubiquitin ligases. Cytoplasmic beta-catenin levels in the transfectants will be monitored in response to specific proteasomal inhibitors that will cause the beta-catenin to accumulate as ubiquitinated conjugates. Finally, the physiological activity of GSK3 beta on APC phosphorylation, and beta-catenin ubiquitination and stability will be addressed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1997
- Accession Number
- ADA345312
Entities
People
- Stephen Byers
- Vijay Easwaran
Organizations
- Georgetown University