Deleted in Colorectal Cancer Binding Netrin-1 Mediates Cell Substrate Adhesion and Recruits Cdc42, Rac1, Pak1, and N-WASP into an Intracellular Signaling Complex That Promotes Growth Cone Expansion

Abstract

Extracellular cues direct axon extension by regulating growth cone morphology. The netrin-1 receptor deleted in colorectal cancer (DCC) is required for commissural axon extension to the floor plate in the embryonic spinal cord. Here we demonstrate that challenging embryonic rat spinal commissural neurons with netrin-1, either in solution or as a substrate, causes DCC-dependent increases in growth cone surface area and filopodia number, which we term growth cone expansion. We provide evidence that DCC influences growth cone morphology by at least two mechanisms. First, DCC mediates an adhesive interaction with substrate-bound netrin-1. Second, netrin-1 binding to DCC recruits an intracellular signaling complex that directs the organization of actin. We show that netrin-1-induced growth cone expansion requires Cdc42 (cell division cycle 42), Rac1 (Ras-related C3 botulinum toxin substrate 1), Pak1 (p21-activated kinase), and N-WASP (neuronal Wiskott-Aldrich syndrome protein) and that the application of netrin-1 rapidly activates Cdc42, Rac1, and Pak1. Furthermore, netrin-1 recruits Cdc42, Rac1, Pak1, and N-WASP into a complex with the intracellular domain of DCC and Nck1. These findings suggest that DCC influences growth cone morphology by acting both as a transmembrane bridge that links extracellular netrin-1 to the actin cytoskeleton and as the core of a protein complex that directs the organization of actin.

Regulation of netrin-1 receptors by amphetamine in the adult brain

“…Based on these findings we propose that if netrin-1 signaling participates in the development of sensitization to AMPH, it may act in concert with bFGF to promote reorganization of VTA DA circuitry. Both bFGF and netrin-1 can induce reorganization of the actin cytoskeleton via receptor-mediated communication with the Rac1 member of the Rho family of small GTPases, key regulators of the actin cytoskeleton (Li et al, 2002;Shekarabi et al, 2005;Shin et al, 2002Shin et al, , 2004. Furthermore, it has been demonstrated that netrin-1 can induce reorganization of dendritic structure in mature neurons via Rac1 signaling (Nakayama et al, 2000).…”

A dual promoter lentiviral vector for the in vivo evaluation of gene therapeutic approaches to axon regeneration after spinal cord injury

“…There are several potential reasons for the lack of response of corticospinal and rubrospinal axons to myrDCCDP1 expression, including: (1) the elimination of Unc-34/enabled downstream signaling resulting from removal of the P1 domain of the DCC construct; 44,49,50 (2) a reduction in signaling through focal adhesion kinase in the adult CNS, 51-53 a protein that functions as a scaffold protein for src family kinase recruitment to the cytoplasmic domain of DCC and as a downstream signaling partner of activated src family kinases that may be required for axon outgrowth; and (3) an imbalance between activation of the small GTPases Rac1 and Cdc42 with RhoA in the adult CNS. Netrin-1 binding to DCC activates Cdc42 and Rac1 in spinal commissural neurons 54,55 and dominant-negative Rac1 and Cdc42 inhibit DCC-mediated neurite outgrowth in neuroblastoma cells, whereas inhibition of RhoA or its effector Rho kinase increases axon extension in response to netrin-1. 56 Predominance of RhoA activation resulting from the expression of myelin inhibitory proteins and their receptors in the adult CNS 57-59 may overwhelm effects of myrDCCDP1 expression.…”

Nétrine-1 et guidage axonal

“…L'activation de Cdc42 a lieu en amont de l'activation de Rac1, mais les mécanismes moléculaires sont encore mystérieux. Rac1 et Cdc42 ainsi activées vont phosphoryler la protéine Pak1 [13] (p21 activated kinase) connue pour favoriser la polymérisation de l'actine. Cette phosphorylation conduit à l'interaction de Pak1 avec Nck1 via son second domaine SH3 entraînant la formation d'un complexe moléculaire contenant DCC, Nck1, Rac1, Cdc42 et Pak1 et nécessaire à la croissance axonale.…”