Biology subjects

Bourke, A. M.

Publications and source records attributed to Bourke, A. M..

4 recordsLinked to original sources

bioRxiv2026

Direct interaction of ribosomes with postsynaptic proteins gives rise to a privileged local synaptic translatome

Ribosomes and thousands of mRNAs are localized near synapses to support local protein synthesis. Little is known, however, about how ribosomes are positioned and maintained in dendritic spines- the primary postsynaptic sites of excitatory neurotransmission. Here, using proximity labeling-mass spectrometry, we mapped the interactome of postsynaptic ribosomes, and discovered an unexpected interaction with AMPA receptor complex proteins. Co-immunoprecipitation and crosslinking mass spectrometry using rat cortical synaptosomes showed a direct, mRNA-independent interaction between postsynaptic proteins and intact ribosomes. Immunoprecipitation-ribosome profiling (IP-Ribo-seq) revealed not only the complete synaptic translatome but also that the AMPA receptor-associated subpopulation of synaptic ribosomes preferentially translates mRNAs encoding proteins related to post-synaptic density (PSD) scaffolding and cytoskeletal dynamics. Translation of one of the mRNA targets, Camk2a, was reduced in spines following ER sequestration of endogenous GluA1. Together, these results reveal a role for PSD proteins in positioning ribosomes near the postsynaptic membrane, providing a mechanism to couple synaptic activity with the local production of proteins needed for structural remodeling.

neuroscience↗

bioRxiv2025

Exosome tethering requires tetherin homodimerisation

Exosomes are small extracellular vesicles that originate as intraluminal vesicles (ILVs) within multivesicular bodies (MVBs). Upon fusion of MVBs with the plasma membrane, ILVs are released into the extracellular environment as exosomes. While exosomes can diffuse away from their cells of origin, the expression of the antiviral restriction factor tetherin promotes their retention at the cell surface, thereby limiting their release into the extracellular milieu. Tetherin plays an analogous role in retaining other extracellular particles, including many enveloped viruses and midbody remnants. In this study, we examine the molecular basis of exosome tethering and define the mechanisms underlying tetherin-mediated retention. Using a combination of biochemical, live-cell and ultrastructural imaging approaches, we show that tetherin homodimerisation is essential for exosome tethering. Mutations in regions or motifs of tetherin predicted to impact tetherin traffic to ILVs have only minor impacts on exosome tethering, suggesting redundancy in the mechanisms of tetherin traffic to ILVs, and subsequently, to exosomes. Collectively, these findings provide the first molecular insights into the mechanism that govern exosome tethering.

cell biology↗

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↗

bioRxiv2020

Local neuronal secretory trafficking dynamics revealed with zapERtrap: a light-inducible ER release system

For normal synapse and circuit function, neurons must regulate the abundance and localization of transmembrane receptor, channel and adhesion proteins over vast cellular expanses, including remote sites in dendrites and axons. Whether the secretory network can support long-range trafficking of synaptic proteins synthesized in the cell body or precise trafficking of locally generated proteins at remote sites remains poorly characterized. We developed an approach for locally triggering secretory trafficking from specific subcellular domains to explore the rate, activity dependence and cargo-specificity of central and remote trafficking networks. Surprisingly, different postsynaptic proteins processed in the cell body were transported deep into dendrites, but with strikingly different kinetics, spatial distributions and activity dependencies. Proteins locally processed in dendrites were broadly dispersed prior to surface insertion, but could be directed locally to synapses. These results provide a novel interrogation of compartmentalized trafficking and reveal basic principles for protein targeting in complex cellular environments.

cell biology↗