scholarly journals Presynaptic FMRP and local protein synthesis support structural and functional plasticity of glutamatergic axon terminals

2021 ◽  
Author(s):  
Hannah R Monday ◽  
Shivani C Kharod ◽  
Young J Yoon ◽  
Robert H Singer ◽  
Pablo E Castillo
Keyword(s):  
Protein Synthesis ◽  
Rna Binding ◽  
Mossy Fiber ◽  
Fragile X ◽  
Long Term Potentiation ◽  
Local Protein Synthesis ◽  
Axon Terminals ◽  
Local Protein

Learning and memory critically rely on long-lasting, synapse-specific modifications. While postsynaptic forms of plasticity typically require local protein synthesis, whether and how local protein synthesis contributes to presynaptic changes remains unclear. Here, we examined the hippocampal mossy fiber (MF)-CA3 synapse which expresses both structural and functional presynaptic plasticity. We report that MF boutons synthesize protein locally and contain ribosomes. Long-term potentiation of MF-CA3 synaptic transmission (MF-LTP) was associated with translation-dependent enlargement of MF boutons. Moreover, increasing in vitro and in vivo MF activity enhanced protein synthesis in MFs. Remarkably, deletion of presynaptic Fragile X mental retardation protein (FMRP), an RNA-binding protein expressed in MF boutons and previously implicated in local postsynaptic protein synthesis-dependent plasticity, blocked structural and functional MF-LTP, suggesting that FMRP is a critical regulator of presynaptic function. Thus, presynaptic FMRP and protein synthesis dynamically control presynaptic structure and function in the mature brain.

scholarly journals ESCRT-II controls retinal axon growth by regulating DCC receptor levels and local protein synthesis

Open Biology ◽  
2016 ◽  
Vol 6 (4) ◽  
pp. 150218 ◽  
Author(s):  
Filip A. Konopacki ◽  
Hovy Ho-Wai Wong ◽  
Asha Dwivedy ◽  
Anaïs Bellon ◽  
Michael D. Blower ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Axon Growth ◽  
Endocytic Pathway ◽  
Loss Of Function ◽  
Gradient Sensing ◽  
Deleted In Colorectal Cancer ◽  
Local Protein Synthesis ◽  
Local Protein

Endocytosis and local protein synthesis (LPS) act coordinately to mediate the chemotropic responses of axons, but the link between these two processes is poorly understood. The endosomal sorting complex required for transport (ESCRT) is a key regulator of cargo sorting in the endocytic pathway, and here we have investigated the role of ESCRT-II, a critical ESCRT component, in Xenopus retinal ganglion cell (RGC) axons. We show that ESCRT-II is present in RGC axonal growth cones (GCs) where it co-localizes with endocytic vesicle GTPases and, unexpectedly, with the Netrin-1 receptor, deleted in colorectal cancer (DCC). ESCRT-II knockdown (KD) decreases endocytosis and, strikingly, reduces DCC in GCs and leads to axon growth and guidance defects. ESCRT-II-depleted axons fail to turn in response to a Netrin-1 gradient in vitro and many axons fail to exit the eye in vivo . These defects, similar to Netrin-1/DCC loss-of-function phenotypes, can be rescued in whole ( in vitro ) or in part ( in vivo ) by expressing DCC. In addition, ESCRT-II KD impairs LPS in GCs and live imaging reveals that ESCRT-II transports mRNAs in axons. Collectively, our results show that the ESCRT-II-mediated endocytic pathway regulates both DCC and LPS in the axonal compartment and suggest that ESCRT-II aids gradient sensing in GCs by coupling endocytosis to LPS.

scholarly journals Local protein synthesis is a ubiquitous feature of neuronal pre- and postsynaptic compartments

2018 ◽  
Author(s):  
Anne-Sophie Hafner ◽  
Paul G. Donlin-Asp ◽  
Beulah Leitch ◽  
Etienne Herzog ◽  
Erin M. Schuman
Keyword(s):  
Protein Synthesis ◽  
Mouse Brain ◽  
Brain Slices ◽  
Metabolic Labeling ◽  
Presynaptic Terminals ◽  
Ample Evidence ◽  
Local Protein Synthesis ◽  
Axon Terminals ◽  
Neuronal Dendrites ◽  
Local Protein

AbstractThere is ample evidence for localized mRNAs and protein synthesis in neuronal dendrites, however, demonstrations of these processes in presynaptic terminals are limited. We used expansion microscopy to resolve pre- and postsynaptic compartments in brain slices. Most presynaptic terminals in the hippocampus and forebrain contained mRNA and ribosomes. We sorted fluorescently labeled synaptosomes from mouse brain and then sequenced hundreds of mRNA species present within excitatory boutons. After brief metabolic labeling, more them 30% of all presynaptic terminals exhibited a signal, providing evidence for ongoing protein synthesis. We tested different classic plasticity paradigms and observed unique patterns of rapid pre- and/or postsynaptic translation. Thus presynaptic terminals are translationally competent and local protein synthesis is differentially recruited to drive compartment-specific phenotypes that underlie different forms of plasticity.One sentence summaryProtein synthesis occurs in all synaptic compartments, including excitatory and inhibitory axon terminals.

scholarly journals Kinase pathway inhibition restores PSD95 induction in neurons lacking fragile X mental retardation protein

2019 ◽  
pp. 201812056
Author(s):  
Ying Yang ◽  
Yang Geng ◽  
Dongyun Jiang ◽  
Lin Ning ◽  
Hyung Joon Kim ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Mental Retardation ◽  
Rna Binding ◽  
Fragile X ◽  
Alternative Pathways ◽  
Fragile X Mental Retardation ◽  
Mrna Targets ◽  
Mental Retardation Protein ◽  
Pathway Inhibition

Fragile X syndrome (FXS) is the leading monogenic cause of autism and intellectual disability. FXS is caused by loss of expression of fragile X mental retardation protein (FMRP), an RNA-binding protein that regulates translation of numerous mRNA targets, some of which are present at synapses. While protein synthesis deficits have long been postulated as an etiology of FXS, how FMRP loss affects distributions of newly synthesized proteins is unknown. Here we investigated the role of FMRP in regulating expression of new copies of the synaptic protein PSD95 in an in vitro model of synaptic plasticity. We find that local BDNF application promotes persistent accumulation of new PSD95 at stimulated synapses and dendrites of cultured neurons, and that this accumulation is absent in FMRP-deficient mouse neurons. New PSD95 accumulation at sites of BDNF stimulation does not require known mechanisms regulating FMRP–mRNA interactions but instead requires the PI3K-mTORC1-S6K1 pathway. Surprisingly, in FMRP-deficient neurons, BDNF induction of new PSD95 accumulation can be restored by mTORC1-S6K1 blockade, suggesting that constitutively high mTORC1-S6K1 activity occludes PSD95 regulation by BDNF and that alternative pathways exist to mediate induction when mTORC1-S6K1 is inhibited. This study provides direct evidence for deficits in local protein synthesis and accumulation of newly synthesized protein in response to local stimulation in FXS, and supports mTORC1-S6K1 pathway inhibition as a potential therapeutic approach for FXS.

scholarly journals FUS-ALS mutants alter FMRP phase separation equilibrium and impair protein translation

2021 ◽  
Vol 7 (30) ◽  
pp. eabf8660
Author(s):  
Nicol Birsa ◽  
Agnieszka M. Ule ◽  
Maria Giovanna Garone ◽  
Brian Tsang ◽  
Francesca Mattedi ◽  
...  
Keyword(s):  
Phase Separation ◽  
Motor Neurons ◽  
Rna Binding ◽  
Fragile X ◽  
Protein Translation ◽  
Fused In Sarcoma ◽  
Mental Retardation Protein ◽  
Lateral Sclerosis

FUsed in Sarcoma (FUS) is a multifunctional RNA binding protein (RBP). FUS mutations lead to its cytoplasmic mislocalization and cause the neurodegenerative disease amyotrophic lateral sclerosis (ALS). Here, we use mouse and human models with endogenous ALS-associated mutations to study the early consequences of increased cytoplasmic FUS. We show that in axons, mutant FUS condensates sequester and promote the phase separation of fragile X mental retardation protein (FMRP), another RBP associated with neurodegeneration. This leads to repression of translation in mouse and human FUS-ALS motor neurons and is corroborated in vitro, where FUS and FMRP copartition and repress translation. Last, we show that translation of FMRP-bound RNAs is reduced in vivo in FUS-ALS motor neurons. Our results unravel new pathomechanisms of FUS-ALS and identify a novel paradigm by which mutations in one RBP favor the formation of condensates sequestering other RBPs, affecting crucial biological functions, such as protein translation.

scholarly journals Selective role of the translin/trax RNase complex in hippocampal synaptic plasticity

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Alan Jung Park ◽  
Mahesh Shivarama Shetty ◽  
Jay M. Baraban ◽  
Ted Abel
Keyword(s):  
Protein Synthesis ◽  
Synaptic Plasticity ◽  
Molecular Mechanisms ◽  
Metabotropic Glutamate Receptor ◽  
Fragile X ◽  
Local Protein Synthesis ◽  
Hippocampal Synaptic Plasticity ◽  
Behavioral Abnormalities ◽  
Local Protein

Abstract Activity-dependent local protein synthesis is critical for synapse-specific, persistent plasticity. Abnormalities in local protein synthesis have been implicated in psychiatric disorders. We have recently identified the translin/trax microRNA-degrading enzyme as a novel mediator of protein synthesis at activated synapses. Additionally, translin knockout (KO) mice, which lack translin/trax, exhibit some of the behavioral abnormalities found in a mouse model of fragile X syndrome (fragile X mental retardation protein-FMRP-KO mice). Therefore, identifying signaling pathways interacting with translin/trax to support persistent synaptic plasticity is a translationally relevant goal. Here, as a first step to achieve this goal, we have assessed the requirement of translin/trax for multiple hippocampal synaptic plasticity paradigms that rely on distinct molecular mechanisms. We found that mice lacking translin/trax exhibited selective impairment in a form of persistent hippocampal plasticity, which requires postsynaptic protein kinase A (PKA) activity. In contrast, enduring forms of plasticity that are dependent on presynaptic PKA were unaffected. Furthermore, these mice did not display exaggerated metabotropic glutamate receptor-mediated long-term synaptic depression (mGluR-LTD), a hallmark of the FMRP KO mice. On the contrary, translin KO mice exhibited deficits in N-methyl-d-aspartate receptor (NMDAR) dependent LTD, a phenotype not observed in the FMRP knockouts. Taken together, these findings demonstrate that translin/trax mediates long-term synaptic plasticity that is dependent on postsynaptic PKA signaling and suggest that translin/trax and FMRP play distinct roles in hippocampal synaptic plasticity.

Early regeneration in vitro of adult mouse sciatic axons is dependent on local protein synthesis but may not involve neurotrophins

1994 ◽  
Vol 168 (1-2) ◽  
pp. 37-40 ◽  
Author(s):  
Magnus Edbladh ◽  
David Tonge ◽  
Jon Golding ◽  
Per A.R. Ekström ◽  
Anders Edström
Keyword(s):  
Protein Synthesis ◽  
Adult Mouse ◽  
Local Protein Synthesis ◽  
Regeneration In Vitro ◽  
Early Regeneration ◽  
Local Protein

scholarly journals Selective role of the translin/trax RNase complex in hippocampal synaptic plasticity

2020 ◽  
Author(s):  
Alan Jung Park ◽  
Mahesh Shivarama Shetty ◽  
Jay M. Baraban ◽  
Ted Abel
Keyword(s):  
Protein Synthesis ◽  
Synaptic Plasticity ◽  
Molecular Mechanisms ◽  
Metabotropic Glutamate Receptor ◽  
Fragile X ◽  
Local Protein Synthesis ◽  
Hippocampal Synaptic Plasticity ◽  
Behavioral Abnormalities ◽  
Local Protein

Abstract Activity-dependent local protein synthesis is critical for synapse-specific, persistent plasticity. Abnormalities in local protein synthesis have been implicated in psychiatric disorders. We have recently identified the translin/trax microRNA-degrading enzyme as a novel mediator of protein synthesis at activated synapses. Additionally, translin knockout (KO) mice, which lack translin/trax, exhibit some of the behavioral abnormalities found in a mouse model of fragile X syndrome (fragile X mental retardation protein-FMRP-KO mice). Therefore, identifying signaling pathways interacting with translin/trax to support persistent synaptic plasticity is a translationally relevant goal. Here, as a first step to achieve this goal, we have assessed the requirement of translin/trax for multiple hippocampal synaptic plasticity paradigms that rely on distinct molecular mechanisms. We found that mice lacking translin/trax exhibited selective impairment in a form of persistent hippocampal plasticity, which requires postsynaptic protein kinase A (PKA) activity. In contrast, enduring forms of plasticity that are dependent on presynaptic PKA were unaffected. Furthermore, these mice did not display exaggerated metabotropic glutamate receptor-mediated long-term synaptic depression (mGluR-LTD), a hallmark of the FMRP KO mice. . On the contrary, translin KO mice exhibited deficits in N-methyl-D-aspartate receptor (NMDAR) dependent LTD, a phenotype not observed in the FMRP knockouts. Taken together, these findings demonstrate that translin/trax mediates long-term synaptic plasticity that is dependent on postsynaptic PKA signaling and suggest that translin/trax and FMRP play distinct roles in hippocampal synaptic plasticity.

scholarly journals The RNA binding protein FXR1 is a new driver in the 3q26-29 amplicon and predicts poor prognosis in human cancers

2015 ◽  
Vol 112 (11) ◽  
pp. 3469-3474 ◽  
Author(s):  
Jun Qian ◽  
Mohamed Hassanein ◽  
Megan D. Hoeksema ◽  
Bradford K. Harris ◽  
Yong Zou ◽  
...  
Keyword(s):  
Rna Binding ◽  
Rna Binding Proteins ◽  
Fragile X ◽  
Lung Squamous Cell Carcinoma ◽  
Regulatory Function ◽  
Driver Gene ◽  
Aberrant Expression ◽  
Human Cancers

Aberrant expression of RNA-binding proteins has profound implications for cellular physiology and the pathogenesis of human diseases such as cancer. We previously identified the Fragile X-Related 1 gene (FXR1) as one amplified candidate driver gene at 3q26-29 in lung squamous cell carcinoma (SCC). FXR1 is an autosomal paralog of Fragile X mental retardation 1 and has not been directly linked to human cancers. Here we demonstrate that FXR1 is a key regulator of tumor progression and its overexpression is critical for nonsmall cell lung cancer (NSCLC) cell growth in vitro and in vivo. We identified the mechanisms by which FXR1 executes its regulatory function by forming a novel complex with two other oncogenes, protein kinase C, iota and epithelial cell transforming 2, located in the same amplicon via distinct binding mechanisms. FXR1 expression is a candidate biomarker predictive of poor survival in multiple solid tumors including NSCLCs. Because FXR1 is overexpressed and associated with poor clinical outcomes in multiple cancers, these results have implications for other solid malignancies.

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