Localization of a β-Actin Messenger Ribonucleoprotein Complex with Zipcode-Binding Protein Modulates the Density of Dendritic Filopodia and Filopodial Synapses
ABSTRACT The dendritic transport and local translation of mRNA may be an essential mechanism to regulate synaptic growth and plasticity. We investigated the molecular mechanism and function of beta-actin mRNA localization in dendrites of cultured hippocampal neurons. Previous studies have shown that beta-actin mRNA localization to the leading edge of fibroblasts or the growth cones of developing neurites involved a specific interaction between a zipcode sequence in the 3' untranslated region and the mRNA-binding protein zipcode-binding protein-1 (ZBP1). Here, we show that ZBP1 is required for the localization of beta-actin mRNA to dendrites. Knock-down of ZBP1 using morpholino antisense oligonucleotides reduced dendritic levels of ZBP1 and beta-actin mRNA and impaired growth of dendritic filopodia in response to BDNF treatment. Transfection of an enhanced green fluorescent protein (EGFP)-beta-actin construct, which contained the zipcode, increased the density of dendritic filopodia and filopodial synapses. Transfection of an EGFP construct, also with the zipcode, resulted in recruitment of endogenous ZBP1 and beta-actin mRNA into dendrites and similarly increased the density of dendritic filopodia. However, the beta-actin zipcode did not affect filopodial length or the density of mature spines. These results reveal a novel function for an mRNA localization element and its binding protein in the regulation of dendritic morphology and synaptic growth via dendritic filopodia.
Full-textDOI: · Available from: Taesun Eom, Nov 17, 2014
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ABSTRACT: The highly conserved, RNA binding VICKZ proteins help regulate RNA localization, stability, and translation in many eukaryotes. These proteins are also required for cell migration in embryos and cultured cells. In adults, many tumors overexpress VICKZ homologs, and it has been hypothesized that the proteins can mediate cell motility and invasion. How these proteins facilitate cell movement and, in particular, whether their ability to bind RNA plays a role in their function remain unclear. Using HPLC and mass spectrometry to identify a region of Xenopus Vg1 RBP (xVICKZ3) that binds the vegetal localization element of Vg1 RNA, we generated a deletion construct that functions in a dominant-negative manner. The construct associates with full-length xVICKZ3 and severely reduces binding to target RNAs. This dominant-negative construct phenocopies the effect of down-regulating xVICKZ3 in Xenopus embryos. A corresponding deletion in the human homolog hVICKZ1 similarly functions in a dominant-negative fashion to reduce the ability of full-length hVICKZ protein to bind RNA. Expression of the dominant-negative construct in human carcinoma cells inhibits cell movement by several criteria. We conclude that the ability of VICKZ proteins to mediate cell migration, in vitro and in vivo, requires their RNA binding activity.RNA 10/2007; 13(9):1558-69. DOI:10.1261/rna.559507 · 4.62 Impact Factor
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ABSTRACT: Protein synthesis-dependent late-long term potentiation (L-LTP) is an enduring form of synaptic plasticity that has been shown to rely on, at least partly, protein synthesis at synaptic and/or dendritic sites. Evidence suggests that somatic transcription of new mRNAs may provide a significant contribution to the availability of mRNAs at synaptic sites where they are made available for dendritic translation. Transport of mRNAs from somatic to dendritic sites might be expected to involve movement along a microtubule network. In this study we examined whether it was possible to maintain L-LTP in hippocampal slices with destabilized microtubule networks. Extracellular field excitatory postsynaptic potentials (fEPSPs) were recorded from rat hippocampal slices and following a period of baseline recording, stimuli were given that induced LTP. LTP was monitored for 5 h in both control slices and slices treated with vincristine to depolymerize tubulin. L-LTP was induced and maintained in vincristine-treated slices. Four hours after tetanic stimulation fEPSPs were 196+/-19% of baseline values. The magnitude of potentiation was similar to that seen in untreated slices (175+/-15%). L-LTP in vincristine-treated slices was, however, not maintained in the presence of the protein synthesis inhibitor, rapamycin. Immunohistochemistry and confocal microscopy of vincristine-treated slices verified that the microtubule network had been destabilized. Communication between somatic and synaptic sites through protein and/or mRNA trafficking via an intact microtubule network is not required for protein synthesis dependent L-LTP.British Journal of Pharmacology 09/2007; 151(7):1071-7. DOI:10.1038/sj.bjp.0707314 · 4.99 Impact Factor
Article: RNA localizationJournal of Cell Science 10/2005; 118(Pt 18):4077-81. DOI:10.1242/jcs.02543 · 5.33 Impact Factor