Editors' ChoiceCell Biology

Signal Scaffolds

Sci. Signal.  21 May 2013:
Vol. 6, Issue 276, pp. ec115
DOI: 10.1126/scisignal.2004332

Scaffolds in cellular signaling pathways are turning out to do way more than just hold proteins together in a complex. Kim et al. showed the importance of the scaffold protein Axin as an active participant controlling the kinetics of activation of signaling through the pathways. Axin is part of two protein complexes that have opposing actions that may regulate the timing of signaling—either activating Wnt signaling, thus protecting β-catenin from destruction, or causing proteolytic destruction of β-catenin. Rock et al. characterized the role of the scaffold protein Nud1 in the mitotic exit network and found that the kinase that produces the output from the signaling complex only interacts with a scaffold that is primed by its activator protein kinase, already bound to the scaffold and creating a docking site.

S.-E. Kim, H. Huang, M. Zhao, X. Zhang, A. Zhang, M. V. Semonov, B. T. MacDonald, X. Zhang, J. G. Abreu, L. Peng, X. He, Wnt stabilization of β-catenin reveals principles for morphogen receptor-scaffold assemblies. Science 340, 867–870 (2013). [Abstract] [Full Text]

J. M. Rock, D. Lim, L. Stach, R. W. Ogrodowicz, J. M. Keck, M. H. Jones, C. C. L. Wong, J. R. Yates III, M. Winey, S. J. Smerdon, M. B. Yaffe, A. Amon, Activation of the yeast Hippo pathway by phosphorylation-dependent assembly of signaling complexes. Science 340, 871–875 (2013). [Abstract] [Full Text]