scholarly journals The translatome of adult cortical axons is regulated by learning in vivo

2018 ◽  
Author(s):  
Linnaea E. Ostroff ◽  
Emanuela Santini ◽  
Robert Sears ◽  
Zachary Deane ◽  
Joseph E. LeDoux ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Synaptic Plasticity ◽  
Associative Memory ◽  
Memory Consolidation ◽  
Affinity Purification ◽  
Local Translation ◽  
Translation Machinery ◽  
Adult Rat ◽  
Neuronal Processes

SummaryLocal translation can support memory consolidation by supplying new proteins to synapses undergoing plasticity. Translation in adult forebrain dendrites is an established mechanism of synaptic plasticity and is regulated by learning, yet there is no evidence for learning-regulated protein synthesis in adult forebrain axons, which have traditionally been believed to be incapable of translation. Here we show that axons in the adult rat amygdala contain translation machinery, and use translating ribosome affinity purification (TRAP) with RNASeq to identify mRNAs in cortical axons projecting to the amygdala, over 1200 of which were regulated during consolidation of associative memory. Mitochondrial and translation-related genes were upregulated, whereas synaptic, cytoskeletal, and myelin-related genes were downregulated; the opposite effects were observed in the cortex. Our results demonstrate that learning-regulated axonal translation occurs in the adult forebrain, and support the likelihood that local translation is more a rule than an exception in neuronal processes.

scholarly journals Axon TRAP reveals learning-associated alterations in cortical axonal mRNAs in the lateral amygdala

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Linnaea E Ostroff ◽  
Emanuela Santini ◽  
Robert Sears ◽  
Zachary Deane ◽  
Rahul N Kanadia ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Synaptic Plasticity ◽  
Associative Memory ◽  
Memory Consolidation ◽  
Affinity Purification ◽  
Local Translation ◽  
Lateral Amygdala ◽  
Translation Machinery ◽  
Adult Rat ◽  
Neuronal Processes

Local translation can support memory consolidation by supplying new proteins to synapses undergoing plasticity. Translation in adult forebrain dendrites is an established mechanism of synaptic plasticity and is regulated by learning, yet there is no evidence for learning-regulated protein synthesis in adult forebrain axons, which have traditionally been believed to be incapable of translation. Here, we show that axons in the adult rat amygdala contain translation machinery, and use translating ribosome affinity purification (TRAP) with RNASeq to identify mRNAs in cortical axons projecting to the amygdala, over 1200 of which were regulated during consolidation of associative memory. Mitochondrial and translation-related genes were upregulated, whereas synaptic, cytoskeletal, and myelin-related genes were downregulated; the opposite effects were observed in the cortex. Our results demonstrate that axonal translation occurs in the adult forebrain and is altered after learning, supporting the likelihood that local translation is more a rule than an exception in neuronal processes.

scholarly journals Inhibition of protein synthesis by N-methyl-N-nitrosourea in vivo

1973 ◽  
Vol 136 (2) ◽  
pp. 303-309 ◽  
Author(s):  
P. Kleihues ◽  
P. N. Magee
Keyword(s):  
Protein Synthesis ◽  
Direct Consequence ◽  
Maximum Effect ◽  
Adult Rat ◽  
Mechanism Of Inhibition ◽  
Weanling Rats ◽  
Inhibition Of Protein Synthesis ◽  
Hepatic Protein Synthesis

1. The intraperitoneal injection of N-methyl-N-nitrosourea (100mg/kg) caused a partial inhibition of protein synthesis in several organs of the rat, the maximum effect occurring after 2–3h. 2. In the liver the inhibition of protein synthesis was paralleled by a marked disaggregation of polyribosomes and an increase in ribosome monomers and ribosomal subunits. No significant breakdown of polyribosomes was found in adult rat brains although N-methyl-N-nitrosourea inhibited cerebral and hepatic protein synthesis to a similar extent. In weanling rats N-methyl-N-nitrosourea caused a shift in the cerebral polyribosome profile similar to but less marked than that in rat liver. 3. Reaction of polyribosomal RNA with N-[14C]methyl-N-nitrosourea in vitro did not lead to a disaggregation of polyribosomes although the amounts of 7-methylguanine produced were up to twenty times higher than those found after administration of sublethal doses in vivo. 4. It was concluded that changes in the polyribosome profile induced by N-methyl-N-nitrosourea may reflect the mechanism of inhibition of protein synthesis rather than being a direct consequence of the methylation of polyribosomal mRNA.

scholarly journals Inhibition by cycloheximide of degradation of cytochrome P-450 in primary cultures of adult rat liver parenchymal cells and in vivo

1979 ◽  
Vol 180 (3) ◽  
pp. 621-630 ◽  
Author(s):  
Philip S. Guzelian ◽  
Joyce L. Barwick
Keyword(s):  
Cell Culture ◽  
Protein Synthesis ◽  
Total Protein ◽  
Cultured Cells ◽  
Liver Parenchymal ◽  
Adult Rat ◽  
Haem Oxygenase ◽  
Parenchymal Cells ◽  
Cytochrome P 450

Degradation of cytochrome P-450 was studied in adult rat liver parenchymal cells in primary monolayer culture. In cells incubated in standard culture medium, the amount of cytochrome P-450 decreased at an accelerated rate relative to either the rate of degradation of total protein in the cells or the turnover of cytochrome P-450 in vivo. This change was succeeded by a spontaneous increase in the activity of haem oxygenase, an enzyme system that converts haem into bilirubin in vitro, measured in extracts from the cultured cells. This finding suggests that the rate of cytochrome P-450 breakdown may be controlled by factor(s) other than the activity of haem oxygenase. The decline in cytochrome P-450 and the subsequent increase in haem oxygenase activity was prevented by incubation of hepatocytes in medium containing an inhibitor of protein synthesis such as cycloheximide, puromycin, actinomycin D, or azaserine. The effect of cycloheximide appeared to be due to decreased breakdown of microsomal 14C-labelled haem. By contrast, cycloheximide was without effect on the degradation of total protein, measured either in homogenates or in microsomal fractions prepared from the cultured cells. These results suggest that the conditions of cell culture stimulate selective degradation of cytochrome P-450 by a process that is inhibited by cycloheximide and hence may require protein synthesis. The findings in culture were verified in parallel studies of cytochrome P-450 degradation in vivo. After administration of bromobenzene, the degradation of the haem moiety of cytochrome P-450 was accelerated in vivo in a manner resembling that observed in cultured hepatocytes. Administration of cycloheximide to either bromobenzene-treated rats or to untreated rats decreased the degradation of the haem moiety of cytochrome P-450. However, the drug failed to affect degradation of haem not associated with cytochrome P-450, suggesting that cycloheximide is not a general inhibitor of haem oxidation in the liver. These findings confirm that the catabolism of hepatic cytochrome P-450 haem is controlled by similar cycloheximide-sensitive processes in the basal steady state in vivo, as stimulated by bromobenzene in vivo, or in hepatocytes under the conditions of cell culture. We conclude that the rate-limiting step in this process appears to require protein synthesis and precedes cleavage of the haem ring.

scholarly journals MoniTORing neuronal excitability at the synapse

2013 ◽  
Vol 202 (1) ◽  
pp. 7-9 ◽  
Author(s):  
Inge Kepert ◽  
Michael A. Kiebler
Keyword(s):  
Protein Synthesis ◽  
Synaptic Plasticity ◽  
Potassium Channel ◽  
Molecular Mechanism ◽  
Neuronal Excitability ◽  
Mammalian Target Of Rapamycin ◽  
Target Of Rapamycin ◽  
Local Translation ◽  
Local Protein Synthesis ◽  
Local Protein

Mammalian target of rapamycin (mTOR) is a key player at the synapse regulating local translation and long-lasting synaptic plasticity. Now, a new study by Sosanya et al. (2013. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201212089) investigates the molecular mechanism of how mTOR suppresses local protein synthesis of a key potassium channel at activated synapses.

scholarly journals The eIF4E homolog 4EHP (eIF4E2) regulates hippocampal long-term depression and impacts social behavior

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Shane Wiebe ◽  
Xiang Qi Meng ◽  
Sung-Hoon Kim ◽  
Xu Zhang ◽  
Jean-Claude Lacaille ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Synaptic Plasticity ◽  
Social Behavior ◽  
Translational Control ◽  
Affinity Purification ◽  
Social Behaviors ◽  
Autism Spectrum ◽  
Repetitive Behaviors ◽  
Physical Interaction ◽  
Excitatory Neurons

Abstract Background The regulation of protein synthesis is a critical step in gene expression, and its dysfunction is implicated in autism spectrum disorder (ASD). The eIF4E homologous protein (4EHP, also termed eIF4E2) binds to the mRNA 5′ cap to repress translation. The stability of 4EHP is maintained through physical interaction with GRB10 interacting GYF protein 2 (GIGYF2). Gene-disruptive mutations in GIGYF2 are linked to ASD, but causality is lacking. We hypothesized that GIGYF2 mutations cause ASD by disrupting 4EHP function. Methods Since homozygous deletion of either gene is lethal, we generated a cell-type-specific knockout model where Eif4e2 (the gene encoding 4EHP) is deleted in excitatory neurons of the forebrain (4EHP-eKO). In this model, we investigated ASD-associated synaptic plasticity dysfunction, ASD-like behaviors, and global translational control. We also utilized mice lacking one copy of Gigyf2, Eif4e2 or co-deletion of one copy of each gene to further investigate ASD-like behaviors. Results 4EHP is expressed in excitatory neurons and synaptosomes, and its amount increases during development. 4EHP-eKO mice display exaggerated mGluR-LTD, a phenotype frequently observed in mouse models of ASD. Consistent with synaptic plasticity dysfunction, the mice displayed social behavior impairments without being confounded by deficits in olfaction, anxiety, locomotion, or motor ability. Repetitive behaviors and vocal communication were not affected by loss of 4EHP in excitatory neurons. Heterozygous deletion of either Gigyf2, Eif4e2, or both genes in mice did not result in ASD-like behaviors (i.e. decreases in social behavior or increases in marble burying). Interestingly, exaggerated mGluR-LTD and impaired social behaviors were not attributed to changes in hippocampal global protein synthesis, which suggests that 4EHP and GIGYF2 regulate the translation of specific mRNAs to mediate these effects. Limitations This study did not identify which genes are translationally regulated by 4EHP and GIGYF2. Identification of mistranslated genes in 4EHP-eKO mice might provide a mechanistic explanation for the observed impairment in social behavior and exaggerated LTD. Future experiments employing affinity purification of translating ribosomes and mRNA sequencing in 4EHP-eKO mice will address this relevant issue. Conclusions Together these results demonstrate an important role of 4EHP in regulating hippocampal plasticity and ASD-associated social behaviors, consistent with the link between mutations in GIGYF2 and ASD.

scholarly journals The Coordination of Local Translation, Membranous Organelle Trafficking, and Synaptic Plasticity in Neurons

2021 ◽  
Vol 9 ◽  
Author(s):  
Dipen Rajgor ◽  
Theresa M. Welle ◽  
Katharine R. Smith
Keyword(s):  
Protein Synthesis ◽  
Synaptic Plasticity ◽  
Mrna Translation ◽  
Synaptic Function ◽  
Synaptic Proteins ◽  
Local Translation ◽  
Local Protein Synthesis ◽  
Regulatory Processes ◽  
Regulation Of Activity ◽  
Activity Dependent

Neurons are highly complex polarized cells, displaying an extraordinary degree of spatial compartmentalization. At presynaptic and postsynaptic sites, far from the cell body, local protein synthesis is utilized to continually modify the synaptic proteome, enabling rapid changes in protein production to support synaptic function. Synapses undergo diverse forms of plasticity, resulting in long-term, persistent changes in synapse strength, which are paramount for learning, memory, and cognition. It is now well-established that local translation of numerous synaptic proteins is essential for many forms of synaptic plasticity, and much work has gone into deciphering the strategies that neurons use to regulate activity-dependent protein synthesis. Recent studies have pointed to a coordination of the local mRNA translation required for synaptic plasticity and the trafficking of membranous organelles in neurons. This includes the co-trafficking of RNAs to their site of action using endosome/lysosome “transports,” the regulation of activity-dependent translation at synapses, and the role of mitochondria in fueling synaptic translation. Here, we review our current understanding of these mechanisms that impact local translation during synaptic plasticity, providing an overview of these novel and nuanced regulatory processes involving membranous organelles in neurons.

scholarly journals Effect of maternal ethanol consumption on foetal and neonatal rat hepatic protein synthesis

1976 ◽  
Vol 160 (3) ◽  
pp. 653-661 ◽  
Author(s):  
A K Rawat
Keyword(s):  
Protein Synthesis ◽  
Ribosomal Protein ◽  
Ethanol Consumption ◽  
Neonatal Rat ◽  
Adult Rat ◽  
Liver Slices ◽  
Foetal Liver ◽  
Hepatic Proteins

Effects of maternal ethanol consumption were investigated on the rates of protein synthehsis by livers of foetal and neonatal rats both in vivo and in vitro, and on the activities of enzymes involved in protein synthesis and degradation. The rates of general protein synthesis by ribosomes in vitro studied by measuring the incorporation of [14C]leucine into ribosomal protein showed that maternal ethanol consumption resulted in an inhibition of the rates of protein synthesis by both foetal and neonatal livers from the ethanol-fed group. The rates of incorporation of intravenously injected [14C]leucine into hepatic proteins were also significantly lower in the foetal, neonatal and adult livers from the ethanol-fed group. Incubation of adult-rat liver slices with ethanol resulted in an inhibition of the incorporation of [14C]leucine into hepatic proteins; however, this effect was not observed in the foetal liver slices. This effect of externally added ethanol was at least partially prevented by the addition of pyrazole to the adult liver slices. Pyrazole addition to foetal liver slices was without significant effect on the rates of protein synthesis. Cross-mixing experiments showed that the capacity of both hepatic ribosomes and pH5 enzyme fractions to synthesize proteins was decreased in the foetal liver from the ethanol-fed group. Maternal ethanol consumption resulted in a decrease in hepatic total RNA content, RNA/DNA ratio and ribosomal protein content in the foetal liver. Foetal hepatic DNA content was not significantly affected. Ethanol consumption resulted in a significant decrease in proteolytic activity and the activity of tryptophan oxygenase in the foetal, neonatal and adult livers. It is possible that the mechanisms of inhibition of protein synthesis observed here in the foetal liver after maternal ethanol consumption may be responsible for at least some of the changes observed in ‘foetal alcohol syndrome’.

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