RNA Localization and Local Translation in Glia in Neurological and Neurodegenerative Diseases: Lessons from Neurons

Cell polarity is crucial for almost every cell in our body to establish distinct structural and functional domains. Polarized cells have an asymmetrical morphology and therefore their proteins need to be asymmetrically distributed to support their function. Subcellular protein distribution is typically achieved by localization peptides within the protein sequence. However, protein delivery to distinct cellular compartments can rely, not only on the transport of the protein itself but also on the transport of the mRNA that is then translated at target sites. This phenomenon is known as local protein synthesis. Local protein synthesis relies on the transport of mRNAs to subcellular domains and their translation to proteins at target sites by the also localized translation machinery. Neurons and glia specially depend upon the accurate subcellular distribution of their proteome to fulfil their polarized functions. In this sense, local protein synthesis has revealed itself as a crucial mechanism that regulates proper protein homeostasis in subcellular compartments. Thus, deregulation of mRNA transport and/or of localized translation can lead to neurological and neurodegenerative diseases. Local translation has been more extensively studied in neurons than in glia. In this review article, we will summarize the state-of-the art research on local protein synthesis in neuronal function and dysfunction, and we will discuss the possibility that local translation in glia and deregulation thereof contributes to neurological and neurodegenerative diseases.

Download Full-text

Object-based analyses in FIJI/ImageJ to measure local RNA translation sites in neurites in response to Aβ1-42 oligomers

10.1101/2020.01.27.921494 ◽

2020 ◽

Author(s):

María Gamarra ◽

Maite Blanco-Urrejola ◽

Andreia F.R. Batista ◽

Josune Imaz ◽

Jimena Baleriola

Keyword(s):

Protein Synthesis ◽

Protein Delivery ◽

Hippocampal Neurons ◽

Rna Localization ◽

Laplacian Operator ◽

Local Translation ◽

Local Protein Synthesis ◽

Rna Translation ◽

Object Based ◽

Local Protein

AbstractSubcellular protein delivery is especially important in signal transduction and cell behavior, and is typically achieved by localization signals within the protein. However, protein delivery can also rely on localization of mRNAs that are translated at target sites. Although once considered heretical, RNA localization has proven to be highly conserved in eukaryotes.RNA localization and localized translation are especially relevant in polarized cells like neurons where neurites extend dozens to hundreds of centimeters away from the soma. Local translation confers dendrites and axons the capacity to respond to their environment in an acute manner without fully relying on somatic signals. The relevance of local protein synthesis in neuron development, maintenance and disease has not been fully acknowledged until recent years, partly due to the limited amount of locally produced proteins. For instance, in hippocampal neurons levels of newly-synthesized somatic proteins can be more than 20-30 times greater than translation levels of neuritic proteins. Thus local translation events can be easily overlooked under the microscope.Here we describe an object-based analysis used to visualize and quantify local RNA translation sites in neurites. Newly-synthesized proteins are tagged with puromycin and endogenous RNAs labelled with SYTO. After imaging, signals corresponding to neuritic RNAs and proteins are filtered with a Laplacian operator to enhance the edges. Resulting pixels are converted into objects and selected by automatic masking followed by signal smoothing. Objects corresponding to RNA or protein and colocalized objects (RNA and protein) are quantified along individual neurites. Colocalization between RNA and protein in neurites correspond to newly-synthesized proteins arising from localized RNAs and represent localized translation sites. To test the validity of our analyses we have compared control neurons to Aβ1-42-treated neurons. Aβ is involved in the pathology of Alzheimer’s disease and was previously reported to induce local translation in axons and dendrites which in turn contributes to the disease. We have observed that Aβ increases the synthesis of neuritic proteins as well as the fraction of translating RNAs in distal sites of the neurite, suggesting an induction of local protein synthesis. Our results thus confirm previous reports and validate our quantification method.

Download Full-text

Microglia perform local protein synthesis at perisynaptic and phagocytic structures

10.1101/2021.01.13.426577 ◽

2021 ◽

Author(s):

Michael J. Vasek ◽

Jelani D. Deajon-Jackson ◽

Yating Liu ◽

Haley W. Crosby ◽

Jiwon Yi ◽

...

Keyword(s):

Protein Synthesis ◽

De Novo ◽

Protein Translation ◽

Local Translation ◽

Slice Preparation ◽

Local Protein Synthesis ◽

Phagocytic Cups ◽

Regulate Protein ◽

Lysosomal Proteins ◽

Local Protein

AbstractRecent studies have illuminated the importance of several key signaling pathways in regulating the dynamic surveillance and phagocytic activity of microglia. Yet little is known about how these signals result in the assembly of phagolysosomal machinery near targets of phagocytosis, especially in processes distal from the microglial soma. Neurons, astrocytes, and oligodendrocytes locally regulate protein translation within distal processes. Therefore, we tested whether there is regulated local translation within peripheral microglia processes (PeMPs). We show that PeMPs contain ribosomes which engage in de novo protein synthesis, and these associate with a subpool of transcripts involved in pathogen defense, motility, and phagocytosis. Using a live slice preparation, we further show that acute translation blockade impairs the formation of PeMP phagocytic cups, the localization of lysosomal proteins within them, and phagocytosis. Collectively, these data argue for a regulated local translation in PeMPs and indicate a need for new translation to support dynamic microglial function.

Download Full-text

Local Translation in Nervous System Pathologies

Frontiers in Integrative Neuroscience ◽

10.3389/fnint.2021.689208 ◽

2021 ◽

Vol 15 ◽

Author(s):

María Gamarra ◽

Aida de la Cruz ◽

Maite Blanco-Urrejola ◽

Jimena Baleriola

Keyword(s):

Nervous System ◽

Protein Synthesis ◽

Rna Binding ◽

Rna Binding Proteins ◽

Local Translation ◽

Transcriptional Responses ◽

Local Protein Synthesis ◽

Genes Encoding ◽

Sense And Respond ◽

Local Protein

Dendrites and axons can extend dozens to hundreds of centimeters away from the cell body so that a single neuron can sense and respond to thousands of stimuli. Thus, for an accurate function of dendrites and axons the neuronal proteome needs to be asymmetrically distributed within neurons. Protein asymmetry can be achieved by the transport of the protein itself or the transport of the mRNA that is then translated at target sites in neuronal processes. The latter transport mechanism implies local translation of localized mRNAs. The role of local translation in nervous system (NS) development and maintenance is well established, but recently there is growing evidence that this mechanism and its deregulation are also relevant in NS pathologies, including neurodegenerative diseases. For instance, upon pathological signals disease-related proteins can be locally synthesized in dendrites and axons. Locally synthesized proteins can exert their effects at or close to the site of translation, or they can be delivered to distal compartments like the nucleus and induce transcriptional responses that lead to neurodegeneration, nerve regeneration and other cell-wide responses. Relevant key players in the process of local protein synthesis are RNA binding proteins (RBPs), responsible for mRNA transport to neurites. Several neurological and neurodegenerative disorders, including amyotrophic lateral sclerosis or spinal motor atrophy, are characterized by mutations in genes encoding for RBPs and consequently mRNA localization and local translation are impaired. In other diseases changes in the local mRNA repertoire and altered local protein synthesis have been reported. In this review, we will discuss how deregulation of localized translation at different levels can contribute to the development and progression of nervous system pathologies.

Download Full-text

MoniTORing neuronal excitability at the synapse

The Journal of Cell Biology ◽

10.1083/jcb.201304183 ◽

2013 ◽

Vol 202 (1) ◽

pp. 7-9 ◽

Cited By ~ 1

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.

Download Full-text