Hand, R. | bioRxiv Science

bioRxiv2023

MAP1B Regulates Cortical Neuron Interstitial Axon Branching Through the Tubulin Tyrosination Cycle

Regulation of directed axon guidance and branching during development is essential for the generation of neuronal networks. However, the molecular mechanisms that underlie interstitial axon branching in the mammalian brain remain unresolved. Here, we investigate interstitial axon branching in vivo using an approach for precise labeling of layer 2/3 callosal projection neurons (CPNs), allowing for quantitative analysis of axonal morphology at high acuity and also manipulation of gene expression in well-defined temporal windows. We find that the GSK3{beta} serine/threonine kinase promotes interstitial axon branching in layer 2/3 CPNs by releasing MAP1B-mediated inhibition of axon branching. Further, we find that the tubulin tyrosination cycle is a key downstream component of GSK3{beta}/MAP1B signaling. We propose that MAP1B functions as a brake on axon branching that can be released by GSK3{beta} activation, regulating the tubulin code and thereby playing an integral role in sculpting cortical neuron axon morphology. HIGHLIGHTS- GSK3{beta} activation induces excessive interstitial axon branching in excitatory cortical neurons - MAP1B, acting as a brake, is a downstream effector of GSK3{beta}-mediated axon branching - MAP1B inhibition of axon branching is released by GSK3{beta} phosphorylation - GSK3{beta}/MAP1B regulation of interstitial axon branching is through modification of the tubulin code

neuroscience↗

bioRxiv2022

Palmitoylation regulates neuropilin-2 localization and function in cortical neurons and conveys specificity to semaphorin signaling via palmitoyl acyltransferases

Secreted semaphorin 3F (Sema3F) and semaphorin 3A (Sema3A) exhibit remarkably distinct effects on deep layer excitatory cortical pyramidal neurons; Sema3F mediates dendritic spine pruning, whereas Sema3A promotes the elaboration of basal dendrites. Sema3F and Sema3A signal through distinct holoreceptors that include neuropilin-2 (Nrp-2)/plexinA3 (PlexA3) and neuropilin-1 (Nrp-1)/PlexA4, respectively. We find that Nrp-2 and Nrp-1 are S-palmitoylated in cortical neurons and that palmitoylation of select Nrp-2 cysteines is required for its proper subcellular localization and also for Sema3F/Nrp-2-dependent dendritic spine pruning in cortical neurons, both in vitro and in vivo. Moreover, we show that the palmitoyl acyltransferase DHHC15 is required for Nrp-2 palmitoylation and Sema3F/Nrp-2-dependent dendritic spine pruning, but it is dispensable for Nrp-1 palmitoylation and Sema3A/Nrp-1-dependent basal dendritic elaboration. Therefore, palmitoyl acyltransferase-substrate specificity is essential for establishing compartmentalized neuronal structure and functional responses to extrinsic guidance cues. HIGHLIGHTSO_LINeuropilins (Nrps) are S-palmitoylated in vitro and in vivo in the central nervous system C_LIO_LIS-palmitoylation of select Nrp-2 cysteines confers subcellular localization specificity and is required for semaphorin 3F-dependent dendritic spine pruning in cortical neurons C_LIO_LIDistinct palmitoyl acyltransferases mediate Nrp-2 and Nrp-1 palmitoylation and function, imparting specificity to semaphorin signaling C_LI

neuroscience↗