Interaction between Dab1 and CrkII is promoted by Reelin signaling

Abstract

Reelin-induced Dab1 tyrosine phosphorylation has been implicated in the regulation of neuronal positioning during brain development. The downstream consequences of Dab1 tyrosine phosphorylation are not fully understood, however. Here we identify CrkII, CrkL and Dock1 in complexes bound to tyrosine-phosphorylated Dab1, through mass spectrometry. The CrkII-Dab1 interaction requires tyrosine phosphorylation of Dab1 at residues 220 or 232 and is promoted by Reelin treatment of embryonic forebrain neurons. Unlike other CrkII binding proteins, such as paxillin and p130Cas, expression of Dab1 interfered with CrkII-dependent cell migration of Nara Bladder Tumor II (NBT-II) cells, in a tyrosine phosphorylation-site dependent manner. Overexpression of CrkIIGFP rescued the migration of these cells, suggesting that Dab1 makes Crk a limiting factor for migration. The Dock1-Dab1 association is indirect and requires CrkII. In organisms such as Drosophila melanogaster and Caenorhabditis elegans, signaling complexes, which contain Crk and Dock1 family members are conserved and act through Rac. We show that a rough-eye phenotype in Drosophila caused by exogenous expression of tyrosine-phosphorylated mouse Dab1RFP is partially rescued by a loss-of-function mutation in myoblast city, a Dock1-like gene in Drosophila. We propose a model that tyrosine-phosphorylated Dab1 engages the conserved Crk-Dock1-Rac signaling cassette, but when bound to Dab1 this signaling complex does not support migration.

Hierarchical Disabled-1 Tyrosine Phosphorylation in Src family Kinase Activation and Neurite Formation

“…proteins associated with Dab1 phosphotyrosine-198 include SFKs (Fyn, Src and Yes), phosphoinositol 3′-kinase (PI3K) and phospholipase C-gamma1 (PLCγ1), while those associated with Dab1 phosphotyrosine-220/232 include the Crk and Nck families of adaptor proteins (CrkII, CrkL and Nckβ). 12,15,[29][30][31][32] Recent data indicate that phosphorylation of Y220 and Y232 is required for the release of neurons from radial glial fibers and may be required for the regulation of α3 integrin levels which are critical for the detachment of migrating neurons from the radial glia. 13 It is noteworthy that the dynein/ dynactin-associated protein, Lis1, requires phosphorylation at both Y198 and Y220 in order to interact with Dab1, 14 indicating that some downstream effectors require phosphorylation at both SFK and Abl/Crk/Nck tyrosine phosphorylation/recognition sites.…”

Reelin-Disabled-1 signaling in neuronal migration: splicing takes the stage

“…Tyrosine-phosphorylated Dab1 acts as a hub to recruit different Src homology 2 (SH2) domain-containing proteins, including the p85 regulatory subunit of phosphatidylinositide-3-kinase (PI3K), cellular adaptors CrkL, Crk, Nckβ and SOCS (suppressor of cytokine signaling) [30,[33][34][35][36][37]. Different tyrosine residues appear to interact with distinct SH2 domains: Y 220 and Y 232 are required for the recruitment of SH2 domains from Crk, CrkL and Nckβ adaptor proteins [30,[35][36][37], whereas Y 185 and Y 198 are necessary for the recruitment of PI3K and SOCS SH2 domains [33][34].…”

“…Different tyrosine residues appear to interact with distinct SH2 domains: Y 220 and Y 232 are required for the recruitment of SH2 domains from Crk, CrkL and Nckβ adaptor proteins [30,[35][36][37], whereas Y 185 and Y 198 are necessary for the recruitment of PI3K and SOCS SH2 domains [33][34]. Tyrosine-phosphorylated Dab1 also interacts with the microtubule associated protein, Lis1, albeit in a SH2 domain-independent manner [38].…”

“…Dab1-Crk-C3G-Rap1-cadherin pathway Reelin promotes Dab1 (at Y220 and Y232 tyrosine phosphorylation sites)-Crk interaction, induces tyrosine phosphorylation of C3G (a guanine nucleotide exchange factor for Rap1) and activates the small GTPase Rap1 [30,34,[36][37]. Ablation of CrkII −/− CrkL −/− in mouse cortex generates a reeler-like phenotype without affecting Reelin-induced Dab1 tyrosine phosphorylation [39].…”

“…YQXI motifs are important for both turning on and turning off downstream pathways by activating PI3K-Akt and triggering Cul5-mediated proteasome degradation of Dab1 [33][34]. YQVP motifs appear to be critical in recruiting Crk and Nck adaptors to form a signaling scaffold complex [30,[34][35][36][37].…”