SummaryIn neurons, transport of a subset of mRNAs to subcellular regions and their translation has a role in synaptic plasticity. Recent studies have suggested a control mechanism of this local translation through mRNA compartmentalization or degradation. Here we report that processing bodies (P-bodies), which are involved in mRNA degradation or storage, are transported to dendrites by conventional kinesin (KIF5A) as a motor protein. Neuronal activation induced by depolarization increased the colocalization of P-bodies with PSD-95 in dendrites. This neuronal activity increased the release of Nd1 and Arp2 mRNA from the P-bodies and, consequently, reversed the decrease of F-actin (induced by overexpression of Dcp1a) in the dendrites. Our data suggest that the activity-induced redistribution of Pbodies and mRNA release from P-bodies might have a role in synaptic structural plasticity by altering levels of mRNAs that are involved in the dynamics of the actin cytoskeleton in dendrites.
BackgroundAlthough the roles of p21-activated serine/threonine kinase 1 (PAK1) have been reported in some neurodegenerative diseases, details regarding neurodegeneration are still limited. Hence, we tried to determine the role of PAK1 and molecular mechanisms of neuronal death involved in neurodegeneration.ResultsExpression of a dominant-negative form of PAK1 (PAK1H83,86L, K229R, PAK1-DN) decreased the cell viability and increased cell death induced by oxidative stress. Indeed, oxidative stress decreased the phosphorylation of PAK1 in neuroblastoma cells, cultured dopamine (DA) neurons, or rat midbrains. PAK1-DN reduced the level of Bcl-2 protein, through an ubiquitin/proteasome-dependent mechanism. The level of Bcl-2 may be regulated by PAK1-ERK signaling and/or PAK1, directly. Conversely, expression of an active form of PAK1 (PAK1T423E, PAK1-CA) could recover both loss of DA neurons in the substantia nigra (SN) and behavioral defects in a 6-OHDA-induced hemiparkinsonian rat model.ConclusionsOur data suggest that the oxidative stress-induced down-regulation of PAK1 activity could be involved in the loss of mesencephalic DA neurons through modulation of neuronal death, suggesting a novel role of PAK1 as a molecular determinant and mechanisms in the pathogenesis of Parkinson’s disease.Electronic supplementary materialThe online version of this article (doi:10.1186/s13041-016-0230-6) contains supplementary material, which is available to authorized users.
J. Neurochem. (2010) 114, 685–696. Abstract Although the dendritic localization and translation of a subset of mRNAs plays a pivotal role in synaptic plasticity, the dendritic mRNAs and their functions have been only minimally characterized thus far. In this study, we isolated mRNAs from Staufen2‐containing ribonucleoprotein complexes, which function as modules for the transport of mRNA to the dendrites, and then constructed a cDNA library. Apolipoprotein E gene (APOE) mRNA was isolated from the dendritic mRNA‐specific cDNA library. The specific localization of APOE mRNA was evaluated via in situ hybridization. The specific regions involved in the dendritic transport of APOE mRNA were determined using a visualization system employing green fluorescent protein‐tagged bacteriophage MS2 RNA‐binding protein. As a result, the proximal N‐terminal or C‐terminal regions of the ApoE‐coding sequences were determined to be sufficient for dendritic transport. The level of dendritic APOE mRNA was significantly increased by depolarization‐induced neuronal activity, but was reduced in the cell body regions. We assessed the functions of neuronal ApoE. The reduction of ganglioside GM1 by cholesterol depletion was completely blocked by ApoE over‐expression. In addition, ApoE over‐expression increased the immunoreactivity of the post‐synaptic density 95 kDa antibody in the dendrites. These findings indicate that neuronal ApoE may be relevant to lipid rafts or synaptic structural plasticity.
Kv4.2, a pore-forming α-subunit of voltage-gated A-type potassium channels, is expressed abundantly in the soma and dendrites of hippocampal neurons, and is responsible for somatodendritic IA current. Recent studies have suggested that changes in the surface levels of Kv4.2 potassium channels might be relevant to synaptic plasticity. Although the function and expression of Kv4.2 protein have been extensively studied, the dendritic localization of Kv4.2 mRNA is not well described. In this study, Kv4.2 mRNAs were shown to be localized in the dendrites near postsynaptic regions. The dendritic transport of Kv4.2 mRNAs were mediated by microtubule-based movement. The 500 nucleotides of specific regions within the 3'-untranslated region of Kv4.2 mRNA were found to be necessary and sufficient for its dendritic localization. Collectively, these results suggest that the dendritic localization of Kv4.2 mRNAs might regulate the dendritic surface level of Kv4.2 channels and synaptic plasticity. [BMB reports 2010; 43(10): 677-682]
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