Post-endocytic sorting of Plexin-D1 controls signal transduction and development of axonal and vascular circuits

Abstract

Local endocytic events involving receptors for axon guidance cues play a central role in controlling growth cone behaviour. Yet, little is known about the fate of internalized receptors, and whether the sorting events directing them to distinct endosomal pathways control guidance decisions. Here, we show that the receptor Plexin-D1 contains a sorting motif that interacts with the adaptor protein GIPC1 to facilitate transport to recycling endosomes. This sorting process promotes colocalization of Plexin-D1 with vesicular pools of active R-ras, leading to its inactivation. In the absence of interaction with GIPC1, missorting of Plexin-D1 results in loss of signalling activity. Consequently, Gipc1 mutant mice show specific defects in axonal projections, as well as vascular structures, that rely on Plexin-D1 signalling for their development. Thus, intracellular sorting steps that occur after receptor internalization by endocytosis provide a critical level of control of cellular responses to guidance signals.

RhoJ integrates attractive and repulsive cues in directional migration of endothelial cells

“…Source data are available online for this figure. complex to perinuclear endosomes, protein levels of only VEGFR2, but not PlexinD1 and Nrp1, were decreased, indicating degradation of VEGFR2 and recycling of the PlexinD1-Nrp1 complex after the termination of signal transduction. Notably, this VEGFR2 degradation was accelerated and delayed by siRNA knockdown of PlexinD1 and Nrp1, respectively, suggesting that the C-terminal PDZ-binding motifs of PlexinD1 and Nrp1 may inversely regulate the endocytic trafficking of VEGFR2 via GIPC1 and myosin VI (Simons et al, 2016;Burk et al, 2017;Carretero-Ortega et al, 2019). In VEGF-stimulated ECs, RhoJ-mediated PlexinD1-VEGFR2 association was required for sustained activation of PLCc, Erk, and Akt, but not p38 MAPK, by preventing VEGFR2 degradation.…”

“…This suggests that PlexinD1 prevents EC contraction by sequestering GTP-RhoJ in the absence of Sema3E. In neurons, the repulsive actions of Sema3E require internalization and trafficking of PlexinD1 destined for recycling endosomes via interaction of its C-terminal PDZ-binding motifs with the adapter protein GIPC1 (Burk et al, 2017). This process may also occur in ECs, in which internalized PlexinD1 is ultimately recycled to the plasma membrane after Sema3E stimulation.…”

“…Semaphorin 3E (Sema3E) binding to the transmembrane receptor PlexinD1 mediates repulsive signals in ECs by inducing PlexinD1 internalization, actin depolymerization, and focal adhesion disassembly (Gu et al, 2005;Sakurai et al, 2010;Fukushima et al, 2011;Burk et al, 2017). Notably, both VEGFR2 and Nrp1 can directly associate with PlexinD1 (Gitler et al, 2004;Bellon et al, 2010).…”

Sensory Axon Growth Requires Spatiotemporal Integration of CaSR and TrkB Signaling

“…Surprisingly, but in line with the observation that the GSK3 inhibitor BIO had no effect on neurite growth, we did not find phosphorylation on GSK3␣ Tyr279, p-GSK3␤ Tyr216, or GSK3␤ Ser9. This result was unexpected since the PI3-kinase-Akt pathway has been reported to be upstream of GSK3␤ Ser9 (Yoshimura et al, 2005;Zhou et al, 2008;Bellon et al, 2010;Burk et al, 2017a), suggesting an uncoupled mechanism (Fig. 2C).…”

“…Because trafficking and signaling of receptors are tightly linked (Wu et al, 2001;Barford et al, 2017;Burk et al, 2017a), we next investigated the trafficking route of CaSR. Literature reports that CaSR is endocytosed and trafficked through Rab11-recycling endosomes, as well as being degraded through late endosomes (Holstein et al, 2004;Reyes-Ibarra et al, 2007;Zhuang et al, 2012;Ray, 2015).…”