Netrin signal transduction and the guanine nucleotide exchange factor DOCK180 in attractive signaling

Abstract

Netrins are prototypical axon guidance cues whose attractive signaling requires the small GTPase Rac1. It remains unclear how Rac1 is regulated in the netrin pathway. DOCK180 is a member of a new family of guanine nucleotide exchange factors for Rho GTPases. Here we provide evidence implicating DOCK180 in netrin signal transduction. Netrin promoted the formation of a protein-protein interaction complex that included DOCK180 and the netrin receptor deleted in colorectal carcinoma (DCC). Inhibition of DOCK180 reduced activation of Rac1 by netrin. Both axon outgrowth and axon attraction induced by netrin were inhibited after DOCK180 knockdown in vertebrate neurons. The in vivo functional role of DOCK180 was demonstrated by its requirement for projection of commissural axons in the neural tube. These findings indicate that netrin stimulation recruits DOCK180 through DCC, which then activates small GTPases, suggesting an essential role for DOCK180 in mediating attractive responses by neurons to netrin-1.

Neogenin Regulates Skeletal Myofiber Size and Focal Adhesion Kinase and Extracellular Signal-regulated Kinase Activities In Vivo and In Vitro

“…Several signaling pathways are activated by netrin signaling through DCC/UNC40 family members, although neogenin is understudied compared with its mammalian paralogue DCC (Forcet et al, 2002;Campbell and Holt, 2003;Li et al, , 2008Liu et al, 2004;Ren et al, 2004;Xie et al, 2005;Zhu et al, 2007). Both FAK and ERK are activated by, and required for, netrin-1/DCC signaling in axon guidance (Forcet et al, 2002;Campbell and Holt, 2003;Li et al, 2004;Liu et al, 2004;Ren et al, 2004).…”

“…Netrin-1 treatment of neurons also leads to DCC-dependent activation of ERK mitogen-activated protein kinase (MAPK) and inhibition of ERK signaling blocks neurite outgrowth and growth cone turning in response to a netrin gradient in vitro (Forcet et al, 2002;Campbell and Holt, 2003). Additional signaling pathways are also activated by netrin-1 signaling via DCC and neogenin (Xie et al, 2005;Zhu et al, 2007;Li et al, 2008).…”

“…Netrin-1 treatment of neurons also leads to DCC-dependent activation of ERK mitogen-activated protein kinase (MAPK) and inhibition of ERK signaling blocks neurite outgrowth and growth cone turning in response to a netrin gradient in vitro (Forcet et al, 2002;Campbell and Holt, 2003). Additional signaling pathways are also activated by netrin-1 signaling via DCC and neogenin (Xie et al, 2005;Zhu et al, 2007;Li et al, 2008).Although neogenin and DCC are similar in their signaling responses to netrin-1 (although not identical, see Xie et al, 2006;Ren et al, 2008), neogenin plays a broader role in development than DCC. First, neogenin, but not DCC, binds to members of a second family of ligands, the GPI-anchored repulsive guidance molecules (RGMa, RGMb, and RGMc) (Rajagopalan et al, 2004;Zhang et al, 2005).…”

c-Jun N-terminal Kinase 1 (JNK1) Is Required for Coordination of Netrin Signaling in Axon Guidance

“…Explants with similar size (200 m) were cultured in the collagen gel as described previously (20,43,44,46). After polymerization, explants were cultured overnight in DMEM ϩ B27 ϩ penicillin/streptomycin with or without purified Netrin-1 in the absence or presence of SP600125.…”

DSCAM functions as a netrin receptor in commissural axon pathfinding

“…The numbers of axons and total axon length were measured using the National Institutes of Health Image J software. Electroporation, open-book preparation, co-culture with control or netrin-secreting cell aggregates, immunostaining, and quantitative analyses of axon turning were performed as described previously (31,35,42). The percentage of turning axons was calculated from the numbers of YFP expressing axons turning toward the HEK cell aggregate divided by the total numbers of YFP expressing axons within 300 m of the HEK cell aggregates.…”