Neural migration. Structures of netrin-1 bound to two receptors provide insight into its axon guidance mechanism

Science (Impact Factor: 33.61). 06/2014; 344(6189):1275-1279. DOI: 10.1126/science.1255149


Netrins are secreted proteins that regulate axon guidance and neuronal migration. Deleted in colorectal cancer (DCC) is a
well-established netrin-1 receptor mediating attractive responses. We provide evidence that its close relative neogenin is
also a functional netrin-1 receptor that acts with DCC to mediate guidance in vivo. We determined the structures of a functional
netrin-1 region, alone and in complexes with neogenin or DCC. Netrin-1 has a rigid elongated structure containing two receptor-binding
sites at opposite ends through which it brings together receptor molecules. The ligand/receptor complexes reveal two distinct
architectures: a 2:2 heterotetramer and a continuous ligand/receptor assembly. The differences result from different lengths
of the linker connecting receptor domains fibronectin type III domain 4 (FN4) and FN5, which differs among DCC and neogenin
splice variants, providing a basis for diverse signaling outcomes.

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Available from: Nicolas Renier, Jul 08, 2014
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    • "Interestingly, the third EGF domain of Ntn1a corresponds to one of the two sites required for binding to Netrin receptors (Finci et al., 2014; Xu et al., 2014). Hence, Draxin and Netrin receptors are likely to compete for binding to the third EGF domain in Netrin-1, providing an explanation for the observed results in the competition assay. "
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    ABSTRACT: Floor-plate-derived extracellular signaling molecules, including canonical axon guidance cues of the Netrin family, control neuronal circuit organization. Despite the importance of the floor plate as an essential signaling center in the developing vertebrate central nervous system, no systematic approach to identify binding partners for floor-plate-expressed cell-surface and secreted proteins has been carried out. Here, we used a high-throughput assay to discover extracellular protein-protein interactions, which likely take place in the zebrafish floor-plate microenvironment. The assembled floor-plate network contains 47 interactions including the hitherto-not-reported interaction between Netrin-1 and Draxin. We further characterized this interaction, narrowed down the binding interface, and demonstrated that Draxin competes with Netrin receptors for binding to Netrin-1. Our results suggest that Draxin functions as an extracellular Netrin signaling modulator in vertebrates. A reciprocal gradient of Draxin might shape or sharpen the active Netrin gradient, thereby critically modulating its effect. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
    Full-text · Article · Jul 2015 · Cell Reports
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    • "ly , three binding sites on the netrin - 1 / DCC complex have been identified by crystal structure analysis ( Finci et al . , 2014 ; Xu et al . , 2014 ) . Among those binding sites , the laminin VI domain and LE3 domain of netrin - 1 bind to DCC FN5 and FN4 domains , respectively , resulting in a continuous netrin - 1 / DCC assembly as proposed by Xu et al . ( 2014 ) . Furthermore , Kruger et al . ( 2004 ) mapped netrin - 1 / Unc5c binding sites and found multiple binding sites on netrin - 1 , including the C345C domain . Therefore , the LE3 domain and C345C domain of netrin - 5 might bind to DCC and to Unc5s , respectively . Those binding analyses should be performed in the future to identify the"
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    ABSTRACT: Mammalian netrin family proteins are involved in targeting of axons, neuronal migration, and angiogenesis and act as repulsive and attractive guidance molecules. Netrin-5 is a new member of the netrin family with homology to the C345C domain of netrin-1. Unlike other netrin proteins, murine netrin-5 consists of two EGF motifs of the laminin V domain (LE) and the C345C domain, but lacks the N-terminal laminin VI domain and one of the three LE motifs. We generated a specific antibody against netrin-5 to investigate its expression pattern in the rodent adult brain. Strong netrin-5 expression was observed in the olfactory bulb (OB), rostral migrate stream (RMS), the subventricular zone (SVZ), and the subgranular zone (SGZ) of the dentate gyrus in the hippocampus, where neurogenesis occurs in the adult brain. In the SVZ and RMS, netrin-5 expression was observed in Mash1-positive transit-amplifying cells and in Doublecortin (DCX)-positive neuroblasts, but not in GFAP-positive astrocytes. In the OB, netrin-5 expression was maintained in neuroblasts, but its level was decreased in NeuN-positive mature neurons. In the hippocampal SGZ, netrin-5 was observed in Mash1-positive cells and in DCX-positive neuroblasts, but not in GFAP-positive astrocytes, suggesting that netrin-5 expression occurs from type 2a to type 3 cells. These data suggest that netrin-5 is produced by both transit-amplifying cells and neuroblasts to control neurogenesis in the adult brain.
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    ABSTRACT: Netrin-1 is a guidance cue that can trigger either attraction or repulsion effects on migrating axons of neurons, depending on the repertoire of receptors available on the growth cone. How a single chemotropic molecule can act in such contradictory ways has long been a puzzle at the molecular level. Here we present the crystal structure of netrin-1 in complex with the Deleted in Colorectal Cancer (DCC) receptor. We show that one netrin-1 molecule can simultaneously bind to two DCC molecules through a DCC-specific site and through a unique generic receptor binding site, where sulfate ions staple together positively charged patches on both DCC and netrin-1. Furthermore, we demonstrate that UNC5A can replace DCC on the generic receptor binding site to switch the response from attraction to repulsion. We propose that the modularity of binding allows for the association of other netrin receptors at the generic binding site, eliciting alternative turning responses.
    Full-text · Article · Aug 2014 · Neuron
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