Disabled-1 Binds to the Cytoplasmic Domain of Amyloid Precursor-Like Protein 1

Abstract

Disruption of the disabled-1 gene (Dab1) results in aberrant migration of neurons during development and disorganization of laminar structures throughout the brain. Dab1 is thought to function as an adapter molecule in signal transduction processes. It contains a protein-interaction (PI) domain similar to the phosphotyrosine-binding domain of the Shc oncoprotein, it is phosphorylated by the Src protein tyrosine kinase, and it binds to SH2 domains in a phosphotyrosine-dependent manner. To investigate the function of Dab1, we searched for binding proteins using the yeast two-hybrid system. We found that the PI domain of Dab1 interacts with the amyloid precursor-like protein 1 (APLP1). The association of Dab1 with APLP1 was confirmed in biochemical assays, and the site of interaction was localized to a cytoplasmic region of APLP1 containing the amino acid sequence motif Asn-Pro-x-Tyr (NPxY). NPxY motifs are involved in clathrin-mediated endocytosis, and they have been shown to bind to PI domains present in several proteins. This region of APLP1 is conserved among all members of the amyloid precursor family of proteins. Indeed, we found that Dab1 also interacts with amyloid precursor protein (APP) and APLP2 in biochemical association experiments. In transiently transfected cells, Dab1 and APLP1 colocalized in membrane ruffles and vesicular structures. Cotransfection assays in cultured cells indicated that APP family members increased serine phosphorylation of Dab1. Dab1 and APLP1 are expressed in similar cell populations in developing and adult brain tissue. These results suggest that Dab1 may function, at least in part, through association with APLP1 in the brain. Key words: reeler; scrambler; neuronal migration; phosphorylation; APLP1; signal transductionThe mutant mouse strains reeler (Falconer, 1951), scrambler (Sweet et al., 1996), and yotari and the mouse strain created by targeted disruption of the disabled-1 (Dab1) gene (Howell et al., 1997a,b) exhibit motor defects and ataxia associated with severe hypoplasia of the cerebellum (for review, see D' Arcangelo and Curran, 1998;Goldowitz and Hamre, 1998). In these mice, neuronal migration is disrupted throughout the brain, resulting in disorganization of many laminar structures, including the hippocampus, cerebral cortex, and cerebellum. Similar, but not identical, defects have been reported in two mutant mouse strains created by targeted disruption of the genes for cyclin-dependent kinase 5 (C dk5) and its neuronalspecific activator p35 (Ohshima et al., 1996;Chae et al., 1997). Characterization of the genes responsible for these mutations has provided a collection of molecules that participate in the signaling cascades responsible for choreographing neuronal migration in the developing brain. The task now facing the field is to understand how these proteins f unction and to elucidate their biochemical and biological relationships.The gene disrupted in reeler mice, reelin (D'Arcangelo et al., 1995), encodes a large extracellular protein that is secreted by pio...

Mutant mice with scrambled brains: understanding the signaling pathways that control cell positioning in the CNS

“…Sev is expressed in R7 precursor cells and it is activated by the ligand, bride of sevenless (Bos), which is expressed on R8 Trommsdorff et al (1998Trommsdorff et al ( , 1999; Homayouni et al (1999); Howell et al (1997aHowell et al ( , 1999b (Xu et al 1995). The function of Dab2 is unknown, but it is phosphorylated on serine residues in response to mitogenic growth factor stimulation.…”

“…Protein interaction screens in yeast and coprecipitation experiments in vitro identified APP and the related proteins, amyloid precursor-like proteins 1 and 2 (APLP1 and APLP2) as binding partners of Dab1 (Trommsdorff et al 1998;Homayouni et al 1999;Howell et al 1999b). The interaction of Dab1 with NPxY motifs present in the cytoplasmic domains of the APP family of proteins does not require tyrosine phosphorylation.…”

“…The association of APLP1 with Dab1 in cotransfected mammalian cells results in enhanced serine phosphorylation of Dab1, suggesting that Dab1 may be part of a signaling mechanism involving multiple protein kinases . Dab1 associates preferentially with APLP1 compared with APP and APLP2, whereas, FE65 binds strongly to APP (Bressler et al 1996;Homayouni et al 1999). Fe65 contains two protein interaction motifs arranged in a linear fashion.…”

Frame‐shifted amyloid precursor protein found in Alzheimer's disease and Down's syndrome increases levels of secreted amyloid β40

“…These proteins, which all bind to the intracellular C-terminal part of APP, are Fe65 (Guenette et al 1999;Sabo et al 1999), X11 Sastre et al 1998), mammalian disabled, mDab1 (Trommsdorff et al 1998;Homayouni et al 1999), JNKinteracting protein-1, JIP-1b (Matsuda et al 2001), a major brain GTP-binding protein, G o (Nishimoto et al 1993), a microtubule-interacting protein, PAT-1 (Zheng et al 1998) and APP-BP1 (Chow et al 1996). Fe65, X11, mDab1 and JIP-1b are adaptor proteins that have a phosphotyrosinebinding domain responsible for the interaction with the YENPTY motif in the cytoplasmic tail of APP.…”

Both the phosphoinositide and receptor binding activities of Dab1 are required for Reelin-stimulated Dab1 tyrosine phosphorylation

“…Dab1 tyrosine phosphorylation increases in response to Reelin stimulation, and the tyrosine phosphorylation sites are required for Dab1 function in vivo [1]. In addition to tyrosine phosphorylation sites, the Dab1 protein contains an N-terminal phosphotyrosinebinding/protein interaction (PTB/PI) domain which can bind to phosphatidylinositol-4,5-bisphosphate and to the FXNPXY endocytosis signals found in various transmembrane proteins [3][4][5][6]. Both peptides and phosphoinositide head groups bind specifically and with micromolar affinity [3,7].…”