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The AP-1 adaptor complex is found in all eukaryotes, but it has been implicated in different pathways in different organisms. To look directly at AP-1 function, we generated stably transduced HeLa cells coexpressing tagged AP-1 and various tagged membrane proteins. Live cell imaging showed that AP-1 is recruited onto tubular carriers trafficking from the Golgi apparatus to the plasma membrane, as well as onto transferrin-containing early/recycling endosomes. Analysis of single AP-1 vesicles showed that they are a heterogeneous population, which starts to sequester cargo 30 min after exit from the ER. Vesicle capture showed that AP-1 vesicles contain transmembrane proteins found at the TGN and early/recycling endosomes, as well as lysosomal hydrolases, but very little of the anterograde adaptor GGA2. Together, our results support a model in which AP-1 retrieves proteins from post-Golgi compartments back to the TGN, analogous to COPI's role in the early secretory pathway. We propose that this is the function of AP-1 in all eukaryotes.
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http://dx.doi.org/10.1083/jcb.202310071 | DOI Listing |
J Allergy Clin Immunol
July 2025
Institute for Molecular Medicine Finland (FIMM), HiLIFE, University of Helsinki, Helsinki, Finland; Norwegian Centre for Molecular Biosciences and Medicine (NCMBM), University of Oslo, Oslo, Norway; Department of Medical Genetics, Oslo University Hospital, Oslo, Norway. Electronic address: j.s.saare
Background: MAP4K1 encodes hematopoietic progenitor kinase 1 (HPK1), a serine/threonine kinase that negatively regulates T-cell receptor signaling via phosphorylation of the adaptor proteins SLP-76 (Src homology 2 domain-containing leukocyte protein of 76 kDa) and Gads. While common MAP4K1 variants have been implicated in polygenic immune-mediated diseases, the impact of rare germline variants on human immunity remains undefined.
Objective: We investigated the immunologic and functional consequences of HPK1 deficiency in individuals with suspected inborn errors of immunity.
FEBS Lett
July 2025
MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, UK.
A signal transduction pathway has been defined in which ADP-heptose activates the mammalian protein kinase ALPK1, which phosphorylates the adaptor protein TIFA, inducing its polymerisation and interaction with the E3 ubiquitin ligases TRAF2/c-IAP1 and TRAF6. These E3 ligases drive activation of the transcription factors NF-κB and AP-1, culminating in the production and secretion of inflammatory mediators to combat microbial infection. TRAF6 is essential in this process, but how TRAF2 interacts with TIFA and its role in the pathway is unclear.
View Article and Find Full Text PDFCell Signal
November 2025
Department of Child Development and Molecular Brain Science, United Graduate School of Child Development, The University of Osaka, Suita, Osaka, Japan.
The primary cilium, an immotile protrusion of vertebrate cells, detects chemical and mechanical stimuli in the extracellular milieu and transduces them into the cell body, thereby contributing to cellular development and homeostasis. In the mammalian brain, serotonin receptor type 6 (Htr6) and other specific G protein-coupled receptors (GPCRs) localize preferentially to primary cilia and function in ciliary chemical detection; however, the molecular mechanism by which a subset of GPCRs is transported to primary cilia has not been fully elucidated. In the present study, we demonstrate that a region in the fourth intracellular domain of Htr6 (Htr6 i4) is sufficient for ciliary localization.
View Article and Find Full Text PDFACS Omega
May 2025
College of Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006, China.
Reptile reoviruses encode the p14 fusion-associated small transmembrane (FAST) protein, which induces cell-cell membrane fusion as a nonstructural protein. When the virus enters the host cell, the p14 protein is encoded, synthesized, and delivered to the plasma membrane via the endoplasmic reticulum-Golgi transport system. During this process, the polybasic motif (PBM) at the proximal membrane terminal of the p14 cytosolic endodomain interacts with Rab11 on the Golgi.
View Article and Find Full Text PDFPlant Physiol
April 2025
School of Life and Environmental Sciences, Shaoxing University, Shaoxing 312000, China.
Plant clathrin and its adaptor protein complexes-adaptor protein complex-1 (AP-1) at the trans-Golgi network/early endosome (TGN/EE) and the adaptor protein complex-2 (AP-2) at the plasma membrane (PM)-function in clathrin-mediated trafficking (CMT). This study reports the role of CMT in regulating copper (Cu) tolerance in plants. We found that high concentrations of exogenous Cu treatment increase the abundance of clathrin and adaptor protein complexes at the TGN/EE and/or the PM.
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