Analysis of the LKB1-STRAD-MO25 complex
Author:
Boudeau Jérôme1, Scott John W.2, Resta Nicoletta3, Deak Maria1, Kieloch Agnieszka1, Komander David14, Hardie D. Grahame2, Prescott Alan R.5, van Aalten Daan M. F.4, Alessi Dario R.1
Affiliation:
1. MRC Protein Phosphorylation Unit, MSI/WTB complex, University of Dundee, Dow Street, Dundee, DD1 5EH, Scotland 2. Division of Molecular Physiology, MSI/WTB complex, University of Dundee, Dow Street, Dundee, DD1 5EH, Scotland 3. Sez, Genetica Medica DIMIMP, Università di Bari, Piazza G. Cesare 11, 70124 Bari, Italy 4. Division of Biological Chemistry and Molecular Microbiology, MSI/WTB complex, University of Dundee, Dow Street, Dundee, DD1 5EH, Scotland 5. Division of Cell Biology and Immunology, MSI/WTB complex, University of Dundee, Dow Street, Dundee, DD1 5EH, Scotland
Abstract
Mutations in the LKB1 tumour suppressor threonine kinase cause the inherited Peutz-Jeghers cancer syndrome and are also observed in some sporadic cancers. Recent work indicates that LKB1 exerts effects on metabolism, polarity and proliferation by phosphorylating and activating protein kinases belonging to the AMPK subfamily. In vivo, LKB1 forms a complex with STRAD, an inactive pseudokinase, and MO25, an armadillo repeat scaffolding-like protein. Binding of LKB1 to STRAD-MO25 activates LKB1 and re-localises it from the nucleus to the cytoplasm. To learn more about the inherent properties of the LKB1-STRAD-MO25 complex, we first investigated the activity of 34 point mutants of LKB1 found in human cancers and their ability to interact with STRAD and MO25. Interestingly, 12 of these mutants failed to interact with STRAD-MO25. Performing mutagenesis analysis, we defined two binding sites located on opposite surfaces of MO25α, which are required for the assembly of MO25α into a complex with STRADα and LKB1. In addition, we demonstrate that LKB1 does not require phosphorylation of its own T-loop to be activated by STRADα-MO25α, and discuss the possibility that this unusual mechanism of regulation arises from LKB1 functioning as an upstream kinase. Finally, we establish that STRADα, despite being catalytically inactive, is still capable of binding ATP with high affinity, but that this is not required for activation of LKB1. Taken together, our findings reinforce the functional importance of the binding of LKB1 to STRAD, and provide a greater understanding of the mechanism by which LKB1 is regulated and activated through its interaction with STRAD and MO25.
Publisher
The Company of Biologists
Reference51 articles.
1. Alessi, D. R., Cohen, P., Ashworth, A., Cowley, S., Leevers, S. J. and Marshall, C. J. (1995). Assay and expression of mitogen-activated protein kinase, MAP kinase kinase, and Raf. Methods Enzymol.255, 279-290. 2. Alessi, D. R., Andjelkovic, M., Caudwell, B., Cron, P., Morrice, N., Cohen, P. and Hemmings, B. A. (1996). Mechanism of activation of protein kinase B by insulin and IGF-1. EMBO J.15, 6541-6551. 3. Baas, A. F., Boudeau, J., Sapkota, G. P., Smit, L., Medema, R., Morrice, N. A., Alessi, D. R. and Clevers, H. C. (2003). Activation of the tumour suppressor kinase LKB1 by the STE20-like pseudokinase STRAD. EMBO J.22, 3062-3072. 4. Baas, A. F., Kuipers, J., van der Wel, N. N., Batlle, E., Koerten, H. K., Peters, P. J. and Clevers, H. C. (2004). Complete polarization of single intestinal epithelial cells upon activation of LKB1 by STRAD. Cell116, 457-466. 5. Berger, M. B., Mendrola, J. M. and Lemmon, M. A. (2004). ErbB3/HER3 does not homodimerize upon neuregulin binding at the cell surface. FEBS Lett.569, 332-336.
Cited by
125 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献
|
|