DOCK180 was identified, using a far-western blotting approach, as a binding partner of the adaptor proteinCrk that was able to induce morphological changes in 3T3 fibroblasts. Subsequently it was reported that DOCK180 was able to activate the small GTP-binding protein (G protein) Rac1 and this was later shown to happen via its ability to act as a GEF.
Structure and function
DOCK180 is part of a large class of proteins (GEFs) which contribute to cellular signalling events by activating small G proteins. In their resting state G proteins are bound to Guanosine diphosphate (GDP) and their activation requires the dissociation of GDP and binding of guanosine triphosphate (GTP). GEFs activate G proteins by promoting this nucleotide exchange.
DOCK180 and related proteins differ from other GEFs in that they do not possess the canonical structure of tandem DH-PH domains known to elicit nucleotide exchange. Instead they possess a DHR2 domain which mediates Rac activation by stabilising it in its nucleotide-free state. DOCK180-related proteins also possess a DHR1 domain which has been shown, in vitro, to bind phospholipids and which may be involved in their interaction with cellular membranes. Other structural features of Dock180 include an N-terminalSH3 domain involved in binding to ELMO proteins (see below) and a C-terminalproline-rich region which, in Myoblast city (the Drosophila melanogaster ortholog of DOCK180), was shown to bind DCrk (the Drosophila ortholog of Crk).
Regulation of DOCK180 Activity
Under physiological conditions DOCK180 alone is inefficient at promoting nucleotide exchange on Rac. Effective GEF activity requires an interaction between Dock180 and its binding partner ELMO. ELMO1 is the most comprehensively described isoform of this small family of non-catalytically active proteins which function to recruit Dock180 to the plasma membrane and induce conformational changes which increase GEF efficiency. ELMO1 has also been reported to inhibit ubiquitinylation of Dock180 and so prevent its degradation by proteasomes. Receptor-mediated activation of RhoG (a small G protein of the Rac subfamily) is perhaps the best known inducer of Dock180 GEF activity. Active (GTP-bound) RhoG recruits the ELMO/Dock180 complex to the plasma membrane thereby bringing Dock180 into contact with its substrate, Rac. In tumour cells DOCK180 is regulated by a complex containing Crk and p130Cas which is in turn regulated by cooperative signalling by β3-containingintegrin complexes and the membrane-bound protein uPAR.
12Côté JF, Vuori K (December 2002). "Identification of an evolutionarily conserved superfamily of DOCK180-related proteins with guanine nucleotide exchange activity". J. Cell Sci. 115 (Pt 24): 4901–13. doi:10.1242/jcs.00219. PMID12432077. S2CID14669715.
↑Brugnera E, Haney L, Grimsley C, Lu M, Walk SF, Tosello-Trampont AC, Macara IG, Madhani H, Fink GR, Ravichandran KS (Aug 2002). "Unconventional Rac-GEF activity is mediated through the Dock180-ELMO complex". Nat. Cell Biol. 4 (8): 574–82. doi:10.1038/ncb824. PMID12134158. S2CID36363774.
Further reading
Takai S, Hasegawa H, Kiyokawa E, etal. (1996). "Chromosomal mapping of the gene encoding DOCK180, a major Crk-binding protein, to 10q26.13-q26.3 by fluorescence in situ hybridization". Genomics. 35 (2): 403–4. doi:10.1006/geno.1996.0378. PMID8661160.
Albert ML, Kim JI, Birge RB (2001). "alphavbeta5 integrin recruits the CrkII-Dock180-rac1 complex for phagocytosis of apoptotic cells". Nat. Cell Biol. 2 (12): 899–905. doi:10.1038/35046549. PMID11146654. S2CID7535200.