The members of the Dock180 superfamily of proteins are novel guanine nucleotide exchange factors (GEF) for Rho family GTPases and are linked to multiple biological processes from worms to mammals. ELMO is a critical regulator of Dock180, and the Dock180–ELMO complex functions as a bipartite GEF for Rac. We identified a mechanism wherein the PH domain of ELMO, by binding the Dock180–Rac complex in trans, stabilizes Rac in the nucleotide-free transition state. Mutagenesis studies reveal that this ELMO PH domain–dependent regulation is essential for the Dock180–ELMO complex to function in phagocytosis and cell migration. Genetic rescue studies in Caenorhabditis elegans using ELMO and its homolog CED-12 support the above observations in vivo. These data reveal a new mode of action of PH domains and a novel, evolutionarily conserved mechanism by which a bipartite GEF can activate Rac.
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We thank A. Bouton and J. Casanova for comments on the manuscript and V. Yajnik, as well as members of the Ravichandran laboratory, for helpful discussions. We also thank M. Matsuda for original Dock180 plasmids and I. Macara for the His-tagged bacterially produced Rac. This work was supported by a US National Institutes of Health (NIH) grant GM-64709 (to K.S.R.) and grants from the Swiss National Science Foundation, The Ernst Hadorn Foundation, and the European Union (FP5 project APOCLEAR) to M.O.H. C.G. was supported by an Infectious Diseases Training grant from the NIH.
The authors declare no competing financial interests.
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Lu, M., Kinchen, J., Rossman, K. et al. PH domain of ELMO functions in trans to regulate Rac activation via Dock180. Nat Struct Mol Biol 11, 756–762 (2004). https://doi.org/10.1038/nsmb800
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