Protein synthesis in the developing neocortex at near-atomic resolution reveals Ebp1-mediated neuronal proteostasis at the 60S tunnel exit
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE157425 | GEO | 2021/03/23
REPOSITORIES: GEO
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Project description:Protein synthesis must be finely tuned in the developing nervous system as the final essential step of gene expression. This study investigates the architecture of ribosomes from the neocortex during neurogenesis, revealing Ebp1 as a high-occupancy 60S peptide tunnel exit (TE) factor during protein synthesis at near-atomic resolution by cryoelectron microscopy (cryo-EM). Ribosome profiling demonstrated Ebp1-60S binding is highest during start codon initiation and N-terminal peptide elongation, regulating ribosome occupancy of these codons. Membrane-targeting domains emerging from the 60S tunnel, which recruit SRP/Sec61 to the shared binding site, displace Ebp1. Ebp1 is particularly abundant in the early-born neural stem cell (NSC) lineage and regulates neuronal morphology. Ebp1 especially impacts the synthesis of membrane-targeted cell adhesion molecules (CAMs), measured by pulsed stable isotope labeling by amino acids in cell culture (pSILAC)/bioorthogonal noncanonical amino acid tagging (BONCAT) mass spectrometry (MS). Therefore, Ebp1 is a central component of protein synthesis, and the ribosome TE is a focal point of gene expression control in the molecular specification of neuronal morphology during development.
| S-EPMC8163098 | biostudies-literature
Project description:Proteostasis must be finely tuned in the nervous system, as it represents an essential feature of neurodevelopment, and dominant pathology in neurodegenerative disease. At the gateway of proteostasis is the ribosome; however, the architecture of ribosomal complexes in the developing mammalian brain has not been visualized. In this study, we analyze the molecular architecture of ex vivo embryonic and perinatal mouse neocortical ribosomes, revealing Ebp1 as a 60S peptide tunnel exit binding factor at near-atomic resolution by multiparticle cryo-electron microscopy. The impact of Ebp1 on the neuronal proteome was analyzed by pSILAC and BONCAT coupled mass spectrometry, implicating Ebp1 in neurite outgrowth proteostasis, with in vivo embryonic Ebp1 knockdown resulting in neurite outgrowth dysregulation. This study constitutes the first near-atomic resolution structure of actively translating ribosomes ex vivo from the nervous system, and visualizes Ebp1 as a chaperone of protein synthesis at the 60S peptide tunnel exit in neocortical neurogenesis.
2021-01-04 | PXD014740 | Pride
Project description:Proteostasis must be finely tuned in the nervous system, as it represents an essential feature of neurodevelopment, and dominant pathology in neurodegenerative disease. At the gateway of proteostasis is the ribosome; however, the architecture of ribosomal complexes in the developing mammalian brain has not been visualized. In this study, we analyze the molecular architecture of ex vivo embryonic and perinatal mouse neocortical ribosomes, revealing Ebp1 as a 60S peptide tunnel exit binding factor at near-atomic resolution by multiparticle cryo-electron microscopy. The impact of Ebp1 on the neuronal proteome was analyzed by pSILAC and BONCAT coupled mass spectrometry, implicating Ebp1 in neurite outgrowth proteostasis, with in vivo embryonic Ebp1 knockdown resulting in neurite outgrowth dysregulation. This study constitutes the first near-atomic resolution structure of actively translating ribosomes ex vivo from the nervous system, and visualizes Ebp1 as a chaperone of protein synthesis at the 60S peptide tunnel exit in neocortical neurogenesis.
2021-01-04 | PXD014841 | Pride
Project description:Protein synthesis in the developing neocortex at near-atomic resolution reveals Ebp1-mediated neuronal proteostasis at the 60S tunnel exit
| PRJNA661272 | ENA
Project description:Human Ebp1 is a member of the proliferation-associated 2G4 (PA2G4) family and plays an important role in cancer regulation. Ebp1 shares the methionine aminopeptidase (MetAP) fold and binds to mature 80S ribosomes for translational control. Here, we present a cryo-EM single particle analysis reconstruction of Ebp1 bound to non-translating human 80S ribosomes at a resolution range from 3.3 to ~8 Å. Ebp1 blocks the tunnel exit with major interactions to the general uL23/uL29 docking site for nascent chain-associated factors complemented by eukaryote-specific eL19 and rRNA helix H59. H59 is defined as dynamic adaptor undergoing significant remodeling upon Ebp1 binding. Ebp1 recruits rRNA expansion segment ES27L to the tunnel exit via specific interactions with rRNA consensus sequences. The Ebp1-ribosome complex serves as a template for MetAP binding and provides insights into the structural principles for spatial coordination of co-translational events and molecular triage at the ribosomal tunnel exit.
| S-EPMC7005732 | biostudies-literature
Project description:Preribosomal particles evolve in the nucleus through transient interaction with biogenesis factors before export to the cytoplasm. Here, we report the architecture of the late pre-60S particle, purified from Saccharomyces cerevisiae, through Arx1, a nuclear export factor with structural homology to methionine aminopeptidases, or its binding partner Alb1. Cryo-EM reconstruction of the Arx1 particle at 11.9-Å resolution reveals regions of extra density on the pre-60S particle attributed to associated biogenesis factors, confirming the immature state of the nascent subunit. One of these densities could be unambiguously assigned to Arx1. Immunoelectron microscopy and UV cross-linking localize Arx1 close to the ribosomal exit tunnel, in direct contact with ES27, a highly dynamic eukaryotic rRNA expansion segment. The binding of Arx1 at the exit tunnel may position this export factor to prevent premature recruitment of ribosome-associated factors active during translation.
| S-EPMC3678077 | biostudies-literature
Project description:The influence of the ribosome on nascent chains is poorly understood, especially in the case of proteins devoid of signal or arrest sequences. Here, we provide explicit evidence for the interaction of specific ribosomal proteins with ribosome-bound nascent chains (RNCs). We target RNCs pertaining to the intrinsically disordered protein PIR and a number of mutants bearing a variable net charge. All the constructs analyzed in this work lack N-terminal signal sequences. By a combination chemical crosslinking and Western-blotting, we find that all RNCs interact with ribosomal protein L23 and that longer nascent chains also weakly interact with L29. The interacting proteins are spatially clustered on a specific region of the large ribosomal subunit, close to the exit tunnel. Based on chain-length-dependence and mutational studies, we find that the interactions with L23 persist despite drastic variations in RNC sequence. Importantly, we also find that the interactions are highly Mg+2-concentration-dependent. This work is significant because it unravels a novel role of the ribosome, which is shown to engage with the nascent protein chain even in the absence of signal or arrest sequences.
| S-EPMC8556260 | biostudies-literature
Project description:Although tertiary folding of whole protein domains is prohibited by the cramped dimensions of the ribosomal tunnel, dynamic tertiary interactions may permit folding of small elementary units within the tunnel. To probe this possibility, we used a beta-hairpin and an alpha-helical hairpin from the cytosolic N terminus of a voltage-gated potassium channel and determined a probability of folding for each at defined locations inside and outside the tunnel. Minimalist tertiary structures can form near the exit port of the tunnel, a region that provides an entropic window for initial exploration of local peptide conformations. Tertiary subdomains of the nascent peptide fold sequentially, but not independently, during translation. These studies offer an approach for diagnosing the molecular basis for folding defects that lead to protein malfunction and provide insight into the role of the ribosome during early potassium channel biogenesis.
| S-EPMC2670549 | biostudies-literature
Project description:Reelin is a large extracellular matrix protein abundantly expressed in the developing neocortex of mammals. During embryonic and early postnatal stages in mice, Reelin is secreted by a transient neuronal population, the Cajal-Retzius neurons (CRs), and is mostly known to insure the inside-out migration of neurons and the formation of cortical layers. During the first 2 postnatal weeks, CRs disappear from the neocortex and a subpopulation of GABAergic neurons takes over the expression of Reelin, albeit in lesser amounts. Although Reelin expression requires a tight regulation in a time- and cell-type specific manner, the mechanisms regulating the expression and secretion of this protein are poorly understood. In this study, we establish a cell-type specific profile of Reelin expression in the marginal zone of mice neocortex during the first 3 postnatal weeks. We then investigate whether electrical activity plays a role in the regulation of Reelin synthesis and/or secretion by cortical neurons during the early postnatal period. We show that increased electrical activity promotes the transcription of reelin via the brain-derived neurotrophic factor/TrkB pathway, but does not affect its translation or secretion. We further demonstrate that silencing the neuronal network promotes the translation of Reelin without affecting the transcription or secretion. We conclude that different patterns of activity control various stages of Reelin synthesis, whereas its secretion seems to be constitutive.
| S-EPMC10393496 | biostudies-literature
Project description:At what point during translation do proteins fold? It is well established that proteins can fold cotranslationally outside the ribosome exit tunnel, whereas studies of folding inside the exit tunnel have so far detected only the formation of helical secondary structure and collapsed or partially structured folding intermediates. Here, using a combination of cotranslational nascent chain force measurements, inter-subunit fluorescence resonance energy transfer studies on single translating ribosomes, molecular dynamics simulations, and cryoelectron microscopy, we show that a small zinc-finger domain protein can fold deep inside the vestibule of the ribosome exit tunnel. Thus, for small protein domains, the ribosome itself can provide the kind of sheltered folding environment that chaperones provide for larger proteins.
| S-EPMC4571824 | biostudies-literature