Mechanism of Ras Activation by TGF beta
Abstract
Transforming growth factor beta (TGF beta) is a potent growth inhibitor for epithelial cells, often displaying tumor-suppressor activity. As described in our last Progress Report we have identified km23 as a novel TGF beta receptor-interacting protein. Here we show that km23 is ubiquitously expressed in human tissues and that cell-type specific differences in endogenous km23 is TGF beta-dependent. Further, the kinase activity of both TGF beta receptors appears to play a role in TGF beta-mediated phosphorylation of km23. Subcellular fractionation analyses revealed that km23 is a cytoplasmic protein. In addition, immunofluorescence analyses indicate that km23 is colocalized with the TGF beta signaling component Smad2, either in the absence of TGF beta treatment, or during early time periods after its addition. km23 also interacted with Smad2 in glutathione-S-transferase (GST) pull-down and immunoprecipitation (IP)/blot assays. Blockade of kra23 using small interfering RNA (siRNA) significantly decreased the ability of TGF beta to inhibit thymidine incorporation. Our findings suggest that km23 is necessary, but not sufficient, for TGF beta-mediated inhibition of DNA synthesis. The data also indicate that kra23 is co-localized with TGF beta signaling components shortly after TGF beta stimulation, but prior to translocation of the signaling complexes to the nucleus.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 2003
- Accession Number
- ADA419253
Entities
People
- Kathleen M. Mulder
Organizations
- Pennsylvania State University