SILAC-based phosphoproteomics reveals an inhibitory role of KSR1 in p53 transcriptional activity via modulation of DBC1.

Abstract

BACKGROUND:

We have previously identified kinase suppressor of ras-1 (KSR1) as a potential regulatory gene in breast cancer. KSR1, originally described as a novel protein kinase, has a role in activation of mitogen-activated protein kinases. Emerging evidence has shown that KSR1 may have dual functions as an active kinase as well as a scaffold facilitating multiprotein complex assembly. Although efforts have been made to study the role of KSR1 in certain tumour types, its involvement in breast cancer remains unknown.

METHODS:

A quantitative mass spectrometry analysis using stable isotope labelling of amino acids in cell culture (SILAC) was implemented to identify KSR1-regulated phosphoproteins in breast cancer. In vitro luciferase assays, co-immunoprecipitation as well as western blotting experiments were performed to further study the function of KSR1 in breast cancer.

RESULTS:

Of significance, proteomic analysis reveals that KSR1 overexpression decreases deleted in breast cancer-1 (DBC1) phosphorylation. Furthermore, we show that KSR1 decreases the transcriptional activity of p53 by reducing the phosphorylation of DBC1, which leads to a reduced interaction of DBC1 with sirtuin-1 (SIRT1); this in turn enables SIRT1 to deacetylate p53.

CONCLUSION:

Our findings integrate KSR1 into a network involving DBC1 and SIRT1, which results in the regulation of p53 acetylation and its transcriptional activity.

• Authors: H Zhang, Y Xu, A Filipovic, L C Lit, C-Y Koo, J Stebbing, G Giamas
• Journal: British journal of cancer (Br J Cancer) Vol. 109 Issue 10 Pg. 2675-84 (Nov 12 2013) ISSN: 1532-1827 [Electronic] England
• PMID: 24129246 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Adaptor Proteins, Signal Transducing
• Amino Acids
• CCAR2 protein, human
• Phosphoproteins
• TP53 protein, human
• Tumor Suppressor Protein p53
• Protein Kinases
• KSR-1 protein kinase
• SIRT1 protein, human
• Sirtuin 1

Topics

• Adaptor Proteins, Signal Transducing (genetics, metabolism)
• Amino Acids (analysis)
• Breast Neoplasms (genetics, metabolism)
• Cell Culture Techniques (methods)
• Down-Regulation
• Female
• Gene Expression Regulation, Neoplastic
• HCT116 Cells
• Humans
• Isotope Labeling (methods)
• Phosphoproteins (analysis)
• Protein Kinases (physiology)
• Proteomics (methods)
• Sirtuin 1 (metabolism)
• Transcriptional Activation
• Tumor Cells, Cultured
• Tumor Suppressor Protein p53 (physiology)