Biology subjects

Farias, G. G.

Publications and source records attributed to Farias, G. G..

8 recordsLinked to original sources

bioRxiv2026

TMEM55B promotes anterograde transport and distal axonal distribution of LAMP1-positive organelles

Lysosomal function throughout life is vital for the proper functioning and survival of post-mitotic neurons by mediating cellular signaling, degradation, and recycling processes. Their intracellular transport relies on microtubule-dependent mechanisms involving kinesin and dynein motors. While lysosomes were long thought absent from axons, recent studies have demonstrated the importance of LAMP1-positive endo-/lysosomal organelles in axonal compartments. This study investigates the physiological role of TMEM55B, a lysosomal membrane protein involved in lysosome positioning and motor coupling in neurons. TMEM55B is highly expressed in LAMP1-positive organelles in cortical neurons. We generated viable Tmem55b knockout mice that exhibited altered lysosomal positioning in neurons. Lysosomes clustered abnormally in the pre-axonal exclusion zone and the proximal axon, with many forming elongated tubular structures. Similarly, in primary rat neurons, TMEM55B depletion resulted in lysosomal tubulation and impaired bidirectional lysosomal transport, particularly in distal axon segments, without affecting lysosome velocity in the proximal and mid-axon. These transport defects were consistent with disrupted JIP4 function, a scaffold linking TMEM55B to both dynein and kinesin motors. TMEM55B deficiency did not result in neurodegeneration, behavioral deficits, or reduced lifespan in mice. As an orthogonal approach, we analyzed TMEM55B function in C. elegans. Worms lacking the TMEM55B homolog Y71H2AM.2 showed altered lysosomal dynamics in cholinergic neurons, supporting an evolutionarily conserved role. To test the involvement of TMEM55B's paralog, TMEM55A, in regulating neuronal lysosome positioning, we generated Tmem55a/b double-knockout mice, which exhibit impaired growth, premature death, and an overall aggravated phenotype. Collectively, our findings demonstrate that both TMEM55B and TMEM55A regulate lysosome distribution in neurons, particularly in axons, by influencing JIP4-dependent retro- and, notably, anterograde motor protein-mediated transport. This function is critical for spatial lysosomal homeostasis. Our study underscores the importance of TMEM55A/TMEM55B in regulating neuronal organelle dynamics and may be a factor considered in neurodegenerative diseases involving lysosomal trafficking defects.

cell biology↗

bioRxiv2026

Spatiotemporal proteomics elucidates trafficking and localization of Neuroligins to the axon initial segment plasma membrane

Neuronal development and function rely on precise sorting of membrane proteins to distinct neuronal domains, yet the underlying mechanisms remain incompletely understood. Here, we investigated the trafficking of two highly homologous NLGNs (NLGN1 and 2) which distinctly localize and function at excitatory and inhibitory synapses. By using spatiotemporal proteomics, genetic engineering and microscopy in CNS cultured neurons and organotypic slices, we dissected the itinerary of biosynthetic NLGNs, identifying co-cargoes and sorting routes to dendrites and the AIS. At the AIS, which contains only inhibitory synapses, both NLGN1 and NLGN2 are locally exocytosed. While NLGN2 is stably recruited to axo-axonic synapses by its extracellular domain and modulated by activity, NLGN1 is retrieved by endocytic mechanisms. We propose that biosynthetic NLGNs are co-sorted to the AIS PM where they detect pre-synaptic type. These findings may help to elucidate the role of AIS-localized NLGNs in shaping AIS structural and functional plasticity. HighlightsO_LISpatiotemporal proteomics elucidates interactome of biosynthetic NLGN1 in neurons C_LIO_LINLGN1 and NLGN2 are targeted to the AIS by kinesin-1 C_LIO_LINLGN2, but not NLGN1, is retained at axo-axonic synapses and modulated by activity C_LIO_LINLGN stability at the AIS plasma membrane is determined by the ectodomain C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=194 HEIGHT=200 SRC="FIGDIR/small/733123v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@a45909org.highwire.dtl.DTLVardef@1d171b0org.highwire.dtl.DTLVardef@17f132aorg.highwire.dtl.DTLVardef@1c33a8d_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

The axonal ER couples translation and secretion machineries for local delivery of axonal transmembrane proteins to promote axonal development

Neuronal development and function rely on the polarized sorting of transmembrane proteins (TMPs). Most TMPs follow a conventional secretory pathway confined to the cell soma, where ER-translated TMPs exit the ER through ERES to reach the Golgi, prior to PM delivery. We recently found that the axonal ER regulates local translation; however, how this is linked to secretion remains unknown. Here, we find that axonally translated TMPs exit the ER and reach the axonal PM via an ERES-dependent/Golgi-independent route. Intriguingly, we uncover a feedback loop linking translation and secretion at axonal ERES. HDLBP-dependent TMP synthesis regulates ERES formation, and axonal ERES in turn modulate TMP translation. Subsequently, the NRZ-SEC22B tethering complex links local TMP ER exit to PM delivery, dependent on ER-PM contacts. Axonal ERES and these associated molecular players support axon growth and bouton assembly. We propose a novel mechanism in which coupling of axonal TMP synthesis and secretion is essential for neuronal development.

cell biology↗

bioRxiv2025

The microcephaly-associated protein YIPF5 differentially regulates ER-export

YIPF5 is a small ER-membrane protein implicated in ER-Golgi transport. Mutations in YIPF5 cause MEDS2 (microcephaly with simplified gyral pattern, epilepsy, and neonatal diabetes syndrome), a fatal disorder manifesting in early childhood. We demonstrate that YIPF5 is involved in ER export of a subset of proteins, including cargoes of the ER-export receptor SURF4, with which it directly interacts. In YIPF5 knockout cells, we observe a shift in the cell surface and secretome composition, marked by reduced neuronal adhesion molecules and increased secretion of ER chaperones influencing cell migration. YIPF5 depletion enhances cell migration in a wound-healing assay and alters SURF4 localization, causing elongated ERGIC53- and Rab1-positive tubules from COPII-labeled ER exit sites. Kinetic analysis suggests that YIPF5 negatively regulates SURF4-mediated ER export. In utero knockdown of Yipf5 in embryonic mouse brains induces premature neuronal migration and abnormal neuronal morphology. These findings suggest that YIPF5 and SURF4 coordinate ER export, and disruption may underlie cortical development defects leading to microcephaly.

cell biology↗

bioRxiv2024

Spatiotemporal proteomics reveals the biosynthetic lysosomal membrane protein interactome in neurons

Lysosomes are membrane-bound organelles critical for maintaining cellular homeostasis. Delivery of biosynthetic lysosomal proteins to lysosomes is crucial to orchestrate proper lysosomal function. However, it remains unknown how the delivery of biosynthetic lysosomal proteins to lysosomes is ensured in neurons, which are highly polarized cells. Here, we developed Protein Origin, Trafficking And Targeting to Organelle Mapping (POTATOMap), by combining trafficking synchronization and proximity-labelling based proteomics, to unravel the trafficking routes and interactome of the biosynthetic lysosomal membrane protein LAMP1 at specified time points. This approach, combined with advanced microscopy, enabled us to identify the neuronal domain-specific trafficking machineries of biosynthetic LAMP1. We revealed a role in replenishing axonal lysosomes, in delivery of newly synthesized axonal synaptic proteins, and interactions with RNA granules to facilitate hitchhiking in the axon. POTATOMap offers a robust approach to map out dynamic biosynthetic protein trafficking and interactome from their origin to destination.

cell biology↗

bioRxiv2022

Axonal ER tubules regulate local translation via P180/RRBP1-mediated ribosome interactions

Local mRNA translation in axons is critical for the spatial and temporal regulation of the axonal proteome. A wide variety of mRNAs are localized and translated in axons, however how protein synthesis is regulated at specific subcellular sites in axons remains unclear. Here, we establish that the axonal endoplasmic reticulum (ER) supports axonal translation. Axonal ER tubule disruption impairs local translation and ribosome distribution. Using nanoscale resolution imaging, we find that ribosomes make frequent contacts with ER tubules in the axon in a translation-dependent manner and are influenced by specific extrinsic cues. We identify P180/RRBP1 as an axonally distributed ribosome receptor that regulates local translation in an mRNA-dependent manner. Our results establish an important role for the axonal ER in localizing mRNA translation and in dynamically regulating the axonal proteome in response to neuronal stimuli.

neuroscience↗

bioRxiv2022

Stress-induced phase separation of ERES components into Sec bodies precedes ER exit inhibition in mammalian cells.

Phase separation of ER-exit-sites (ERES) components into membraneless compartments, the Sec bodies, occurs in Drosophila cells upon specific cellular stressors, i.e., salt stress and amino acid starvation, and their formation is linked to the inhibition of the early secretory pathway. Here, we show Sec bodies also form in secretory mammalian INS-1 cells upon the same stress. These reversible and membraneless structures are positive for ERES components, including both isoforms of Sec16 (A and B) and COPII subunits. We find that Sec16A, but not Sec16B, is a driver for Sec body formation. We show that the coalescence of ERES components into Sec bodies occurs by fusion, in line with their liquid-droplet properties. Lastly, we demonstrate that stress-induced ER-exit inhibition is a consequence of the significant coalescence of Sec16A into Sec bodies, leading to its depletion from ERES that become non-functional. Stress relief causes an immediate dissolution of Sec bodies and the concomitant restoration of protein exit from the ER. We propose a model in which dynamic conversion between ERES and Sec body assembly, driven by Sec16A, regulates protein exit from the ER during stress and upon stress relief in mammalian cells, thus providing a conserved pro-survival mechanism in response to stress.

cell biology↗

bioRxiv2020

ER - lysosome contacts at a pre-axonal region regulate axonal lysosome availability

Neuronal function relies on careful coordination of organelle organization and transport. Kinesin-1 mediates transport of the ER and lysosomes into the axon and it is increasingly recognized that contacts between the ER and lysosomes influence organelle organization. However, it is unclear how organelle organization, inter-organelle communication and transport are linked and how this contributes to local organelle availability in neurons. Here, we show that somatic ER tubules are required for proper lysosome transport into the axon. Somatic ER tubule disruption causes accumulation of enlarged and less motile lysosomes at the soma. ER tubules regulate lysosome size and axonal translocation by promoting lysosome homo-fission. ER tubule - lysosome contacts often occur at a somatic pre-axonal region, where the kinesin-1-binding ER-protein P180 binds microtubules to promote kinesin-1-powered lysosome fission and subsequent axonal translocation. We propose that ER tubule - lysosome contacts at a pre-axonal region finely orchestrate axonal lysosome availability for proper neuronal function.

cell biology↗