A New Invasion and Metastasis Molecule, Tiaml and Its Interaction with the Cytoskeleton are Involved in Human Breast Cancer Progression.
Abstract
In this study we have examined the interaction between the guanine nucleotide exchange factor, Tiam1, and the cytoskeletal protein, ankyrin, in metastatic breast cancer cells (Met-1 cell line). Immunoblot assay using anti-Tiam1-specific antibody shows that Tiam1 is a 200 kDa polypeptide in Met-1 cells. Structural analysis indicates that the amino acid sequence, "(717)GEGTDAVKRS(727)L", in Tiam1 shares a great deal of structural homology with the ankyrin-binding domain located in CD44 isoforms. Most importantly, we have determined that ankyrin binding to Tiam1 activates GDP-GTP exchange on RhoA. In addition, overexpression of Tiam1 (by transfecting Met-1 cell with Tiam1 cDNAs) induces ankyrin-linked cytoskeletal changes and membrane motility (e.g., membrane spikes and ruffling), tumor cell invasion and migration. Finally, we have constructed a Tiam1 deletion mutant lacking the ankyrin binding site. This truncated cDNA was then transiently transfected into Met-1 cells. Our results indicate that this Tiam1 deletion mutant (lacking an ankyrin binding and displaying a reduced GDP-GTP exchange activity for RhoA) functions as a potent dominant-negative form of Tiam1 which effectively inhibits metastatic tumor cell behaviors. These findings strongly suggest that the ankyrin binding site located within Tiam1 plays a pivotal role in RhoA activation required for ankyrin-based cytoskeleton function and oncogenic signaling (e.g., membrane motility, tumor cell invasion and migration) during metastatic breast tumor cell progression.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1998
- Accession Number
- ADA365476
Entities
People
- Lilly Y. Bourguignon
Organizations
- University of Miami