Science: in neuronal processes, monosome preferentially translates synaptic mRNA

February 7, 2020 BIOON / - -- RNA sequencing and in situ hybridization revealed an unexpected large number of RNA species in neuron dendrites and axons, and many studies have recorded local translation of proteins in these cells In the process of mRNA translation, multiple ribosomes can occupy a single mRNA (a complex called multiribosome) at the same time, resulting in multiple copies of the encoded protein Polyribosomes are usually identified in electron microscope images as clusters of three or more ribosomes Polyribosomes have been detected in the dendrites of neurons, but surprisingly, given the diversity of mRNA present in dendrites and axons, polyribosomes are not common In the process of neuron processes, the characteristics and mechanism of translation have not been discussed in detail, in part, because it is relatively difficult to approach dendrites and axons In a new study, researchers from the Max Planck Institute for brain research in Germany studied how a diverse set of neuronal proteins could be synthesized from a limited number of polysomes present in smaller synapses The relevant research results were published in the Science Journal on January 31, 2020, and the title of the paper is "Monosomes actively translate synthetic mRNAs in the national processes" The single ribosome translates synaptic mRNA in the neural network The picture is from science, 2020, DOI: 10.1126/science.aay4991 In order to adapt to the complex morphology of neurons, they locate mRNA and ribosome near the synapse in order to produce protein locally However, the relative scarcity of multiribosomes (active sites of protein translation) detected in electron microscope images of neuronal processes suggests that the ability of local protein synthesis is rather limited To visualize the ability of local protein production in the body, the researchers analyzed actively translated mRNA in the neurites of the hippocampus of rodents In order to analyze the neuron compartment, the researchers made microdissection of the neuron network and somata layer from the CA1 region of hippocampal slices, so as to obtain samples rich in dendrites and axons but not rich in somata Polysome profiling for microdissection regions can be used to determine the correlation between axon and / or dendrite and somatic mRNA transcripts and monosome and polysome Ribosome imprinting is then used to evaluate the translation activity of single and multi ribosomes Bioinformatics analysis is used to determine the characteristics of mRNA transcripts with monosome preference and the protein family encoded by mRNA transcripts with monosome preference The researchers also compared the monosome to polysome (M / P) preferences of mRNA transcripts in the soma and neural networks In order to estimate the abundance of proteins encoded by single ribosome preferred mRNA transcripts and multi ribosome preferred mRNA transcripts, they measured protein levels in the neural network using a mass spectrometry based proteomic method In the brains of adult rodents, these researchers detected a large amount of protein synthesis in the synaptic nerve fiber network (an area rich in neuron axons and dendrites), and provided direct evidence that single ribosomes preferentially translated a large number of presynaptic transcripts and postsynaptic transcripts Single ribosomes are involved in the extension of active peptides in dendrites and axons Most transcripts show similar M / P preference in cell body and nerve fiber network, which indicates that ribosome occupation is usually the intrinsic feature of transcripts Several mRNA transcripts show a preference for single ribosomes or multiribosomes, which depends on the neuron compartment where the transcripts are located; these mRNA encode some proteins related to synaptic plasticity In general, the neural network shows a preference for monosome translation Single ribosome preferred transcripts encode a series of proteins from low abundance to high abundance in the neural network In this new study, the researchers studied the translational landscape in neuronal processes and determined that the local translation of 80S ribosomes is an important source of synaptic proteins Transcripts located in the neural network (i.e., neural network transcripts) exhibit a higher monosome preference than cell transcripts, potentially allowing the production of a diverse set of proteins using a limited number of available ribosomes in the synapse Therefore, this finding bridged the gap between the relative scarcity of translation complexes visualized in neuronal processes and the actual measurement of local translation Considering the spatial limitation of dendritic spines and axonal boutons, synaptic activity can also regulate the translation of single ribosomes, which makes the local proteome diverse in time and space (bio Com) reference: Anne biever et al Monosomes actively translate synthetic mRNAs in national processes Science, 2020, DOI: 10.1126/science.aay4991