Search bioRxiv⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.64898/2026.10.21.760840

The AP-1 clathrin adaptor has a conserved role in recycling resident proteins of the trans-Golgi network

Valbuena, F. M.·Lessard, M.·Krahn, A. H.·Pantazopoulou, A.·Lee-Smith, C. F.·Adarska, P.·Bottanelli, F.·Glick, B. S.
View original source ↗Export metadata ↓

Abstract

Although the AP-1 clathrin adaptor has been studied for decades, its role in membrane trafficking has been ambiguous. Here, we systematically investigated the localization and function of mammalian AP-1. This adaptor associates with the trans-Golgi network (TGN) and with TGN-related recycling endosomes. Disruption of the 1A subunit of AP-1 has only a mild effect on the Golgi export of secretory cargoes, but it causes depletion from the Golgi of multiple transmembrane TGN proteins. Live-cell imaging and a cell surface labeling assay indicate that when TGN proteins are unable to bind AP-1, they exit the Golgi to the plasma membrane. Our interpretation is that the vesicles generated with AP-1 recycle transmembrane TGN proteins, thereby keeping those proteins in the Golgi during cisternal maturation. The clathrin adaptor epsinR seems to function as a partner for AP-1 in recycling a subset of TGN proteins. These results closely align with studies of AP-1 function in yeast, suggesting that the conserved core role of AP-1 is the intra-Golgi recycling of TGN proteins.

Explore related subjects

cell biologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Valbuena, F. M., Lessard, M., Krahn, A. H., Pantazopoulou, A., Lee-Smith, C. F., Adarska, P., Bottanelli, F., Glick, B. S.. 2026-10-22. The AP-1 clathrin adaptor has a conserved role in recycling resident proteins of the trans-Golgi network. https://doi.org/10.64898/2026.10.21.760840

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

The Structural Basis of Genome Silencing: The Inactive X Chromosome Resolved by Electron Spectroscopic Imaging

The eukaryotic nucleus has a hierarchical organization that permits genomic regulation. The genome is packaged as chromatin, which is silenced conditionally as facultative heterochromatin, or more stably silenced as constitutive heterochromatin. The smaller fractions of the genome that contain gene-rich sequences are organized into open chromatin conformations known as euchromatin. The inactive X (Xi) chromosome territory presents a uniquely powerful model system to investigate chromosome-scale gene silencing, as the entire chromosome undergoes coordinated epigenetic repression. The unique chromosome-wide silencing event provides a tractable system for investigating how molecular mechanisms of gene repression are translated into mesoscale structural features. This work builds on previous structural studies of the Xi that have leveraged conventional electron microscopy (EM) and cryo-EM, which have led to remarkable insights into the structural underpinnings of genome silencing. These approaches, however, are unable to directly distinguish chromatin from RNA and protein features. To resolve the molecular composition of the Xi chromosome territory and to provide a model of the structural organization of the chromatin, RNA and protein we analyzed the Xi using Electron Spectroscopic Imaging (ESI). We are able to resolve structural features without the use of contrast enhancing stains, using the distinct elemental signatures of chromatin, RNA and protein and combining them into composite images. By coupling ESI and electron tomography, we can circumvent the projection limitation of EM and provide an unprecedented view of the spatial organization of chromatin fibres in relation to structural features including RNA and proteins in 3D. Additionally, we employed correlative light-microscopy with ESI in physical serial sections and computationally assembled a structural model of the entire Xi chromosome territory revealing an intricate spatial network with distinct chromatin domains, distributed RNA-protein clusters, and identified a large, and previously uncharacterized mesoscale non-chromatin structure. Together, these observations provide new insights into the architecture of the Xi chromosome territory and shed electrons on the structural basis of chromosome-scale genome organization.

cell biology↗
bioRxiv2026

STRIPAK associates with Rabex5-Rabaptin5 to promote Rab5-dependent early endosome formation and EGFR transport

His Domain Protein Tyrosine Phosphatase (HD-PTP) is required for multivesicular body (MVB) formation and endosome maturation, with Rab5-GTP levels raised upon HD-PTP depletion (Parkinson et al., 2021. doi: 10/1242/jcs.259192). Mass Spectrometry-based interactomics revealed that HD-PTP depletion increased association of Rabaptin5, a component of the early endosome Rabex5-Rabaptin5 Rab5-GEF, with multiple components of STRIPAK (striatin-interacting phosphatase and kinase). Native IPs and co-expression studies confirmed association between STRIPAK and Rabex5-Rabaptin5, including Strip1-Rabex5 and SLMAP-Rabaptin5 interactions. Consistent with functional Rabaptin5-STRIPAK links, co-depletion of Strip1 or Rabaptin5 with HD-PTP restored normal early endosome positioning and Rab5 distribution. Strip1 depletion impaired formation of central, Rab5-positive early endosomes, reduced cellular Rab5-GTP levels, and prevented the accumulation of internalised EGF-EGFR into centrally located endosomes. SLMAP depletion accentuated the central clustering of early endosomes and other endosomal compartments while also retarding the generation of new, EGFR-containing endosomes and EGFR lysosomal transport. We conclude that STRIPAK is a novel co-assembly factor of Rabex5-Rabaptin5, exerting subunit-specific effects on early endosomes.

cell biology↗
bioRxiv2026

Oncostatin M-driven leak in human endothelial cells with preserved tight junctions

Blood vessels must preserve blood volume while permitting exchange of nutrients. Endothelial cells line the lumen of all blood vessels and form the intercellular junctions that govern vascular permeability. In acute critical illness the barrier fails, fluid escapes into tissues, and the resulting loss of volume and impaired nutrient exchange cause organ failure. Several inflammatory cytokines are known to disrupt junctions in cultured cells, yet therapies targeting these models have failed. How blood vessels respond to critical illness has remained largely elusive because endothelial cells are generally inaccessible. Here we profile endothelial cells recovered directly from critically ill children to show that oncostatin M drives a previously unrecognized mode of vascular leak. Oncostatin M increases permeability by forming narrow, nanoscale channels within the overlapping borders of adjacent cells, around intact tight junctions. These channels permit passage of small and intermediate sized solutes. Their formation depends on non-canonical signaling in which the kinase JAK1 activates two required parallel pathways (via ERK1 and AKT1) that converge on the transcription factor c-Fos. Inhibiting JAK1, either parallel pathway or depleting c-Fos, prevents oncostatin M-induced loss of barrier function. These results identify a permeability mechanism distinct from the junction disassembly driven by the cytokines that have dominated this field and implicate kinases already targeted by approved drugs as potential points of intervention. More broadly, vascular barriers are transiently loosened during immune-cell trafficking and metastasis, raising the possibility that diverse forms of vascular permeability arise through regulated nanoscale remodeling rather than junctional breakdown.

cell biology↗