Cholesterol-mediated Neurite Outgrowth Is Differently Regulated between Cortical and Hippocampal Neurons

Mihee Ko,Kun Zou,Hirohisa Minagawa,Wenxin Yu,Jian-Sheng Gong,Katsuhiko Yanagisawa,Makoto Michikawa

doi:10.1074/jbc.m509164200

Mihee Ko, Kun Zou + Show 5 more

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https://doi.org/10.1074/jbc.m509164200

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Abstract

The acquisition of neuronal type-specific morphogenesis is a central feature of neuronal differentiation and has important consequences for region-specific nervous system functions. Here, we report that the cell type-specific cholesterol profile determines the differential modulation of axon and dendrite outgrowths in hippocampal and cerebral cortical neurons in culture. The extent of axon and dendrite outgrowths is greater and the polarity formation occurs earlier in cortical neurons than in hippocampal neurons. The cholesterol concentrations in total homogenate and the lipid rafts from hippocampal neurons are significantly higher than those from cortical neurons. Cholesterol depletion by beta-cyclodextrin markedly enhanced the neurite outgrowth and accelerated the establishment of neuronal polarity in hippocampal neurons, which were similarly observed in nontreated cortical neurons, whereas cholesterol loading had no effects. In contrast, both depletion and loading of cholesterol decreased the neurite outgrowths in cortical neurons. The stimulation of neurite outgrowth and polarity formation induced by cholesterol depletion was accompanied by an enhanced localization of Fyn, a Src kinase, in the lipid rafts of hippocampal neurons. A concomitant treatment with beta-cyclodextrin and a Src family kinase inhibitor, PP2, specifically blocked axon outgrowth but not dendrite outgrowth (both of which were enhanced by beta-cyclodextrin) in hippocampal neurons, suggesting that axon outgrowth modulated by cholesterol is induced in a Fyn-dependent manner. These results suggest that cellular cholesterol modulates axon and dendrite outgrowths and neuronal polarization under culture conditions and also that the difference in cholesterol profile between hippocampal and cortical neurons underlies the difference in neurite outgrowth between these two types of neurons.

Highlights

Requires the up-regulation of sphingomyelin synthesis [2, 3]
The longest-axon length and total dendrite length were greater in cortical neurons than in hippocampal neurons; these lengths increased with culture time in both types of neurons (Fig. 1, g and i)
The number of neurites per cortical neuron on culture day 5 was similar to the number of neurites per hippocampal neuron (Fig. 1j)

Summary

Introduction

Requires the up-regulation of sphingomyelin synthesis [2, 3]. Cholesterol plays a prominent role in raft-mediated trafficking and sorting, because cholesterol depletion by methyl-␤-cyclodextrin impedes trafficking from the trans-Golgi network to the apical membrane [4]. Previous studies have shown that glia-derived cholesterol is essential for synaptogenesis and synaptic plasticity [10, 11] These lines of evidence suggest that membrane lipids play essential roles in neurite outgrowth and the formation of synapse neuronal polarity. Other lines of evidence suggest that cholesterol plays essential roles in the modulation of tau phosphorylation [6, 18, 19], neurofibrillary tangle formation [20], and neuronal survival [21, 22] These lines of evidence suggest that Alzheimer disease pathologies preferentially developing in specific brain regions may be explained by a region-specific difference in the lipid profile. The present study was designed to determine whether there is any difference in the profiles of lipids in primary cultured neurons isolated from different regions, namely, the mouse cerebral cortices and hippocampus, and whether neuronal function, including neurite outgrowth and polarity formation, is modulated by cellular lipids

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