Biology subjects

Fusco, C. M.

Publications and source records attributed to Fusco, C. M..

4 recordsLinked to original sources

bioRxiv2025

Neuronal processes contain the essential components for the late steps of ribosome biogenesis

Neurons rely on spatial and temporal control of protein synthesis to respond rapidly and locally to external stimuli, a process facilitated by the dynamic localization and modification of ribosomes. While previous research has shown that neuronal activity can regulate ribosome localization and modify translation rates, little is known about ribosomal assembly within neuronal processes. Here, we investigated the potential for local ribosome maturation in rat neurons using proteomics, RNA sequencing, and imaging methods. We detected an abundance of ribosome biogenesis factors (RBFs) in distal neuronal compartments, particularly those associated with the late stages of ribosome assembly. Moreover, we detected cytosolic pre-rRNA species in dendrites, alongside the enzymes necessary for their processing, suggesting that local ribosome maturation can occur far from the nucleus. These findings challenge conventional models that confine ribosome biogenesis to nuclear and perinuclear regions and suggest that neurons may fine-tune local protein synthesis by regulating ribosome assembly near synaptic sites. This mechanism may enable rapid modulation of the translational capacity in response to physiological changes, regulating synaptic plasticity and local protein synthesis in neurons. Significance StatementNeurons require precise spatial and temporal regulation of protein synthesis to adapt rapidly to external stimuli, particularly at synapses. Our study challenges the view that new ribosomes can be made exclusively near the nucleus and reveals that ribosome biogenesis factors and pre-rRNA processing enzymes are present in distal neuronal compartments. These findings suggest that ribosome maturation can occur locally in dendrites, enabling rapid, spatially targeted modulation of translational capacity. This mechanism provides a different framework for understanding how neurons regulate synaptic plasticity and adapt to physiological changes. By demonstrating that ribosome assembly may extend beyond the nucleus, this work highlights a previously unrecognized layer of neuronal protein synthesis control, potentially transforming our understanding of how neurons orchestrate local responses to environmental cues.

cell biology↗

bioRxiv2021

Co-translational assembly counteracts promiscuous interactions

During the co-translational assembly of protein complexes, a fully synthesized subunit engages with the nascent chain of a newly synthesized interaction partner. Such events are thought to contribute to productive assembly, but their exact physiological relevance remains underexplored. Here, we examined structural motifs contained in nucleoporins for their potential to facilitate co-translational assembly. We experimentally tested candidate structural motifs and identified several previously unknown co-translational interactions. We demonstrate by selective ribosome profiling that domain invasion motifs of beta-propellers, coiled-coils, and short linear motifs act as co-translational assembly domains. Such motifs are often contained in proteins that are members of multiple complexes (moonlighters) and engage with closely related paralogs. Surprisingly, moonlighters and paralogs assembled co-translationally in only one but not all of the relevant assembly pathways. Our results highlight the regulatory complexity of assembly pathways.

molecular biology↗

bioRxiv2021

Neuronal ribosomes dynamically exchange ribosomal proteins in a context-dependent manner.

Owing to their morphological complexity and dense network connections, neurons modify their proteomes locally, using mRNAs and ribosomes present in the neuropil (tissue enriched for dendrites and axons). Although ribosome biogenesis largely takes place in the nucleus and perinuclear region, neuronal ribosomal protein (RP) mRNAs have been frequently detected remotely, in dendrites and axons. Here, using imaging and ribosome profiling, we directly detected the RP mRNAs and their translation in the neuropil. Combining brief metabolic labeling with mass spectrometry, we found that a group of RPs quickly associated with translating ribosomes in the cytoplasm and that this incorporation is independent of canonical ribosome biogenesis. Moreover, the incorporation probability of some RPs was regulated by location (neurites vs. cell bodies) and changes in the cellular environment (in response to oxidative stress). Our results suggest new mechanisms for the local activation, repair and/or specialization of the translational machinery within neuronal processes, potentially allowing remote neuronal synapses a rapid solution to the relatively slow and energy-demanding requirement of nuclear ribosome biogenesis.

molecular biology↗

bioRxiv2019

Neuronal Proteostasis is mediated by the switch-like expression of Heme-regulated Kinase 1, acting as both a sensor and effector

All cells, including neurons, have regulatory feedback mechanisms that couple protein synthesis and degradation to maintain and optimize protein concentrations in the face of intra- and extracellular perturbations. We examined the feedback between the major protein degradation pathway, the ubiquitin-proteasome system (UPS), and protein synthesis in neurons. When protein degradation by the UPS was inhibited we observed a coordinate dramatic reduction in nascent protein synthesis in both neuronal cell bodies and dendrites. The mechanism for translation inhibition involved the phosphorylation of eIF2a, surprisingly mediated by eIF2a kinase 1, or heme-regulated kinase inhibitor (HRI), known for its sensitivity to heme levels in erythrocyte precursors (Han et al., 2001). Under basal conditions, neuronal expression of HRI is barely detectable. Following proteasome inhibition, HRI protein levels increase owing to stabilization of the short-lived HRI protein and enhanced translation via the increased availability of tRNAs for rare codons. Once expressed, HRI is constitutively active in neurons because endogenous heme levels are so low; HRI activity results in eIF2a phosphorylation and the resulting inhibition of translation. These data demonstrate a novel role for HRI in neurons, acting as an \"immediate early protein\" that senses and responds to compromised function of the proteasome to restore proteostasis.\n\nOne sentence summaryProteasome inhibition leads to a compensatory reduction in neuronal protein synthesis via the stabilization and enhanced translation of short-lived HRI kinase, which is constitutively active upon expression owing to low neuronal heme levels.

neuroscience↗