Dataset Information

BDNF stimulation of protein synthesis in cortical neurons requires the eIF4E kinase Mnk1

ABSTRACT: Although the Mnks have been known for >15 years, their roles in the regulation of protein synthesis have remained obscure. Here we explore how BDNF stimulates protein synthesis in cortical neurons. Using a combination of pharmacological and genetic approaches, we show that this effect depends on MEK/ERK signaling and on the downstream kinase, Mnk1, which phosphorylates eIF4E. Translation initiation is mediated by the interaction of eIF4E with the m7GTP cap of mRNA and with eIF4G. The latter interaction is inhibited by the interactions of eIF4E with partner proteins such as CYFIP1, which together with its partner, FMRP acts as a translational repressor. We find that BDNF induces the release of CYFIP1 from eIF4E, and that this depends on Mnk1. Finally, using a novel combination of BONCAT and SILAC, we identify the a subset of proteins whose synthesis is upregulated by BDNF signalling via Mnk1 in neurons. The This subset of Mnk1-sensitive proteins are enriched for functions involved in neurotransmission and synaptic plasticity. Additionally, we find significant overlap between our subset of Mnk1 Mnk1-sensitive proteins and proteins encoded by known FMRP-binding mRNAs. Taken together, our data implicate Mnk1 as a key component of BDNF-mediated translational regulation in neurons.

INSTRUMENT(S): LTQ Orbitrap Elite

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Brain, Electrically Active Cell

DISEASE(S): Fragile X Syndrome

SUBMITTER: Harvey Johnston

LAB HEAD: Spiro D. Garbis

PROVIDER: PXD001074 | Pride | 2014-11-06

REPOSITORIES: Pride

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Publications

BDNF stimulation of protein synthesis in cortical neurons requires the MAP kinase-interacting kinase MNK1.

Genheden Maja M Kenney Justin W JW Johnston Harvey E HE Manousopoulou Antigoni A Garbis Spiros D SD Proud Christopher G CG

The Journal of neuroscience : the official journal of the Society for Neuroscience 20150101 3

Although the MAP kinase-interacting kinases (MNKs) have been known for >15 years, their roles in the regulation of protein synthesis have remained obscure. Here, we explore the involvement of the MNKs in brain-derived neurotrophic factor (BDNF)-stimulated protein synthesis in cortical neurons from mice. Using a combination of pharmacological and genetic approaches, we show that BDNF-induced upregulation of protein synthesis requires MEK/ERK signaling and the downstream kinase, MNK1, which phosph ...[more]

PMID: 25609615

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Project description:FMRP loss-of-function causes Fragile X Syndrome (FXS) and autistic features. FMRP is a polyribosome-associated neuronal RNA-binding protein, suggesting that it plays a key role in regulating neuronal translation, but there has been little consensus regarding either its RNA targets or mechanism of action. Here we use high throughput sequencing of RNAs isolated by crosslinking immunoprecipitation (HITS-CLIP) to identify FMRP interactions with mouse brain polyribosomal mRNAs. FMRP interacts with the coding region of transcripts encoding pre- and postsynaptic proteins, and transcripts implicated in autism spectrum disorders Polyribosomes were prepared from UV254-crosslinked pooled littermate FVB mouse brains as described in detail in published paper PMID 21784246. Polyribosomes were dissociated under denaturing conditions using two different protocols to disrupt ribonucleoprotein complexes. In most experiments Fmr1-null littermates were used in parallel to confirm FMRP specificity. After mild RNAse treatment to reduce the size of RNA to 60-100 nucleotides, endogenous FMRP was immunoprecipitated with one of two antibody combinations, either mixed monoclonal antibodies 7G1-1 and 2F5, or polyclonal antibody ab17722 (Abcam). The ages of the mice were P11, P13, P14, P15, and P25. In addition, to assess a different neuronal polysome-associated protein, as another control, lysates prepared from two samples, the P11 and P13 mice, were split in half and one half IPed with a human anti-Hu antisera as the neuronal Hu proteins are polysome-associated in brain. In sum, 7 FMRP HITS-CLIP experiments were performed including (1) P14 mouse polysomes prepared by Protocol 1 and IPed with 7G1-1/2F5 (2) P14 mouse polysomes prepared by Protocol 1 and IPed with ab17722 (3) P15 mouse polysomes prepared by Protocol 1 and IPed with 7G1-1/2F5 (4) P25 mouse polysomes prepared by Protocol 1 and IPed with 7G1-1/2F5 (5) P25 mouse polysomes prepared by Protocol 1 and IPed with ab17722 (6) P11 mouse polysomes prepared by Protocol 2 and IPed with ab17722 and (7) P13 mouse polysomes prepared by Protocol 2 and IPed with ab17722. FMRP-bound or Hu-bound RNA tags were cloned and submitted for high throughput sequencing on the Life Science 454 platform (samples 1-5) or the Illumina platform (samples 6 and 7 and the 2 Hu samples processed in parallel with samples 6 and 7). Full details are given in PMID 21784246.

Project description:Local translation at the synapse plays key roles in neuron development and activity-dependent synaptic plasticity. mRNAs are translocated from the neuronal soma to the distant synapses as compacted ribonucleoparticles referred to as RNA granules. These contain many RNA-binding proteins, including the Fragile X Mental Retardation Protein (FMRP), the absence of which results in Fragile X Syndrome, the most common inherited form of intellectual disability and the leading genetic cause of autism. Using FMRP as a tracer, we purified a specific population of RNA granules from mouse brain homogenates. Protein composition analyses revealed a strong relationship between polyribosomes and RNA granules. However, the latter have distinct architectural and structural properties, since they are detected as close compact structures as observed by electron microscopy, and converging evidence point to the possibility that these structures emerge from stalled polyribosomes. Time-lapse video microscopy indicated that single granules merge to form cargoes that are transported from the soma to distal locations. Transcriptomic analyses showed that a subset of mRNAs involved in cytoskeleton remodelling and neural development is selectively enriched in RNA granules. One third of the putative mRNA targets described for FMRP appear to be transported in granules and FMRP is more abundant in granules than in polyribosomes. This observation supports a primary role for FMRP in granules biology. Our findings open new avenues for the study of RNA granule dysfunctions in animal models of nervous system disorders, such as Fragile X syndrome. Fragile X syndrome is the most common form of inherited mental retardation affecting approximately 1 female out of 7000 and 1 male out of 4000 worldwide. The syndrome is due to the silencing of a single gene, the Fragile Mental Retardation 1 (FMR1), that codes for the Fragile X mental retardation protein (FMRP). This protein is highly expressed in brain and controls local protein synthesis essential for neuronal development and maturation as well as the formation of neural circuits. Several studies suggest a role for FMRP in the regulation of mRNA transport along axons and dendrites to distant synaptic locations in structures called RNA granules. Here we report the isolation of a particular subpopulation of these structures and the analysis of their architecture and composition in terms of RNA and protein. Also, using time-lapse video microscopy, we monitored granule transport and fusion throughout neuronal processes. These findings open new avenues for the study of RNA transport dysfunctions in animal models of nervous system disorders. The control or reference structure or subcellular fraction are the neuronal polyribosomes while the experimental or test structure or subcellular fraction are the neuronal granules. Three independant replicates were done for each structure. Microarray hybridization was done using a two-color design in full dye-swap.

Dataset Information

BDNF stimulation of protein synthesis in cortical neurons requires the eIF4E kinase Mnk1

Publications

BDNF stimulation of protein synthesis in cortical neurons requires the MAP kinase-interacting kinase MNK1.

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