C-terminal SH3 domain of CrkII regulates the assembly and function of the DOCK180/ELMO Rac-GEF.

Genetic studies in Caenorhabditis elegans identified an evolutionarily conserved CED-2 (CrkII), CED-5 (DOCK180), CED-12 (ELMO), CED-10 (Rac1) module important for cell migration and phagocytosis of apoptotic cells. Previous studies have shown that DOCK180 and ELMO comprise an unconventional bipartite Dbl homology domain-independent Rac guanine nucleotide exchange factor (Rac-GEF); but it is still unclear how CrkII functions in Rac-GEF activity. In this study, we have characterized a unique function of CrkII in phagocytosis and Rac activation mediated by the C-terminal SH3 domain, a region of CrkII that has no clear cellular or biochemical function. We found that mutations that disrupt the C-terminal SH3 domain of CrkII (CrkII-SH3-C) abrogate engulfment of apoptotic cells and impair cell spreading on extracellular matrix. Surprisingly, despite the effects on engulfment, W276K CrkII strongly potentiated Rac-GTP loading when ectopically expressed in HEK 293T cells. Contrary to the effects of the true dominant negative SH2 domain mutants (R38K CrkII) and SH3-N domain mutants (W170K CrkII) that prevent macromolecular assembly of signaling proteins, W276K CrkII increases association between DOCK180 and CrkII as well as constitutive tethering of the Crk/DOCK180/ELMO protein complex that interacted with RhoG. Our results indicate that while N-terminal SH3 of CrkII promotes assembly between CrkII and DOCK180, the C-terminal SH3 of CrkII regulates the stability and turnover of the DOCK180/ELMO complex. Studies with W276K CrkII may offer a unique opportunity to study the structure and function of the DOCK180/ELMO Rac-GEF.

Akakura S ，Kar B ，Singh S ，Cho L ，Tibrewal N ，Sanokawa-Akakura R ，Reichman C ，Ravichandran KS ，Birge RB ... -  《JOURNAL OF CELLULAR PHYSIOLOGY》

Identification of two signaling submodules within the CrkII/ELMO/Dock180 pathway regulating engulfment of apoptotic cells.

Tosello-Trampont AC ，Kinchen JM ，Brugnera E ，Haney LB ，Hengartner MO ，Ravichandran KS ... -  《CELL DEATH AND DIFFERENTIATION》

Unconventional Rac-GEF activity is mediated through the Dock180-ELMO complex.

Brugnera E ，Haney L ，Grimsley C ，Lu M ，Walk SF ，Tosello-Trampont AC ，Macara IG ，Madhani H ，Fink GR ，Ravichandran KS ... -  《NATURE CELL BIOLOGY》

PH domain of ELMO functions in trans to regulate Rac activation via Dock180.

Lu M ，Kinchen JM ，Rossman KL ，Grimsley C ，deBakker C ，Brugnera E ，Tosello-Trampont AC ，Haney LB ，Klingele D ，Sondek J ，Hengartner MO ，Ravichandran KS ... -  《-》

Ankyrin repeat domain 28 (ANKRD28), a novel binding partner of DOCK180, promotes cell migration by regulating focal adhesion formation.

Tachibana M ，Kiyokawa E ，Hara S ，Iemura S ，Natsume T ，Manabe T ，Matsuda M ... -  《-》