CED-12/ELMO, a Novel Member of the CrkII/Dock180/Rac Pathway, Is Required for Phagocytosis and Cell Migration

Abstract

The C. elegans genes ced-2, ced-5, and ced-10, and their mammalian homologs crkII, dock180, and rac1, mediate cytoskeletal rearrangements during phagocytosis of apoptotic cells and cell motility. Here, we describe an additional member of this signaling pathway, ced-12, and its mammalian homologs, elmo1 and elmo2. In C. elegans, CED-12 is required for engulfment of dying cells and for cell migrations. In mammalian cells, ELMO1 functionally cooperates with CrkII and Dock180 to promote phagocytosis and cell shape changes. CED-12/ELMO-1 binds directly to CED-5/Dock180; this evolutionarily conserved complex stimulates a Rac-GEF, leading to Rac1 activation and cytoskeletal rearrangements. These studies identify CED-12/ELMO as an upstream regulator of Rac1 that affects engulfment and cell migration from C. elegans to mammals.

Identification of Tyrosine Residues on ELMO1 That Are Phosphorylated by the Src-Family Kinase Hck

“…Dock180 and ELMO1 have previously been shown to associate directly (19,22). We coexpressed M45-tagged ELMO1 and FLAG-Dock180 together with Hck in 293T cells.…”

“…(For reasons that are not clear, we were unable to express the Y395F ELMO1 mutant in these cells under a variety of conditions.) A two-color flow cytometry assay was carried out to determine the fraction of GFP-positive cells that can engulf red fluorescent latex beads (19). The expression of Dock180 or ELMO1 alone did not promote phagocytosis of the beads ( Figure 3).…”

“…ELMO1/ ced-12 was identified as an upstream regulator of Rac that functions genetically at the same step as Dock180/ced-5 in the engulfment of apoptotic cells and in cell migration (19). Overexpression of mammalian ELMO1 rescues the distal tip cell migration defect of the ced-12 mutant C. elegans (19). In mammalian fibroblasts, the ELMO1/Crk/Dock180 complex functions upstream of Rac during phagocytosis and cell migration.…”

“…The Dock180-ELMO1 complex functions as an unconventional two-component exchange factor for Rac, and ELMO1 directly participates in the stimulation of Rac GEF activity and Rac GTP loading (20,21). ELMO1 has no discernible catalytic domain, but at its C-terminus it possesses a pleckstrin homology (PH) domain, a putative leucine zipper motif, and a proline-rich motif (19,22). The C-terminal 100 amino acids of ELMO1 are essential for the interaction with Dock180 (20), while the Nterminus of ELMO1 is important for mediating cell migration via the ELMO1-Dock180 complex (23).…”

Involvement of adaptor protein Crk in malignant feature of human ovarian cancer cell line MCAS

“…The activation of Rho was also reported (Tsuda et al, 2002;Iwahara et al, 2003). Dock180 and its binding molecule ELMO cooperatively regulate Rac activity and are thought to be involved in the phagocytosis of apoptotic cells (Albert et al, 2000;Gumienny et al, 2001;Brugnera et al, 2002). C3G regulates the MAP kinase and JNK pathway by activating Rap and R-Ras, respectively, following phosphorylation on tyrosine residue 504 (Tanaka et al, 1997;Tanaka and Hanafusa, 1998;Mochizuki et al, 2000).…”