Regulation of Patterned Dynamics of Local Exocytosis in Growth Cones by Netrin-1

Abstract

Axonal guidance and synaptic specification depends on specific signaling mechanisms that occur in growth cones. While several signaling pathways implicated in cone navigation have been identified, membrane dynamics in growth cones remains largely unknown. We took advantage of SynaptopHluorin and high-speed optical recordings to monitor the patterns of membrane dynamics in rat hippocampal growth cones. We show that exocytosis occurs both at the peripheral and central domains, including filopodia, and that SynaptopHluorin signals occur as spontaneous patterned peaks. Such transients average approximately two per minute and last ϳ30 s. We also demonstrate that the chemoattractant Netrin-1 elicits increases in the frequency and slopes of these transients, with peaks averaging up to six per minute in the peripheral domain. Netrin-1-dependent regulation of exocytotic events requires the activation of the Erk1/2 and SFK pathways. Furthermore, we show that domains with high SynaptopHluorin signals correlate with high local calcium concentrations and that local, spontaneous calcium increases are associated with higher SynaptopHluorin signals. These findings demonstrate highly stereotyped, spontaneous transients of local exocytosis in growth cones and that these transients are positively regulated by chemoattractant molecules such as Netrin-1.

Non-proliferative adult neurogenesis in neural crest-derived stem cells isolated from human periodontal ligament

“…3E). These finding are consistent with a previous study reporting that membrane addition and extension in growth cones is mediated by diverse mechanism, including exocytosis of vesicular components [52]. Microtubule-associated proteins Tau and MAP2 were also found in hPDLSCs-derived neurons (Fig.…”

Exocytic and endocytic membrane trafficking in axon development

“…VAMP7-positive vesicles are transported from the soma to the growth cone in a microtubule-dependent manner, and then exocytosed at the growth cone . It is also observed that VAMP2-mediated exocytosis occurs at the growth cone periphery including filopodia (Sabo & Mcallister 2003;Tojima et al 2007;Ros et al 2015). In addition to VAMPs, SNAP25 (Osen-Sand et al 1993;Morihara et al 1999;Shirasu et al 2000) and syntaxins 1, 6, and 13 (Igarashi et al 1996;Hirling et al 2000;Zhou et al 2000;Kabayama et al 2008) are reported to be needed for axon outgrowth.…”

Membrane turnover and receptor trafficking in regenerating axons

“…Membrane trafficking must be maintained until axons re-establish target contact and stop growing. Vesicle exocytosis occurs at both the peripheral and central domains, including filopodia, and is stimulated by chemoattractants such as netrin-1 (Ros et al, 2015). Furthermore, growth cones continuously recycle membrane proteins, such as cell adhesion molecules, by vesicle endocytosis at the centre, and send them back to the advancing edge of the cone (Kamiguchi & Lemmon, 2000).…”