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Qi W, Zhang Y, Li M, Zhang P, Xing J, Chen Y, Zhang L. Endocytic recycling in plants: pathways and regulation. JOURNAL OF EXPERIMENTAL BOTANY 2024; 75:4712-4728. [PMID: 38655916 DOI: 10.1093/jxb/erae188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Accepted: 04/23/2024] [Indexed: 04/26/2024]
Abstract
Endocytic recycling is an intracellular trafficking pathway that returns endocytosed molecules to the plasma membrane via the recycling endosome. This pathway plays a crucial role in remodelling plasma membrane composition and is thus essential for cellular homeostasis. In plants, endocytic recycling regulates the localization and abundance of receptors, transporters, and channels at the plasma membrane that are involved in many aspects of plant growth and development. Despite its importance, the recycling endosome and the underlying sorting mechanisms for cargo recycling in plants remain understudied in comparison to the endocytic recycling pathways in animals. In this review, we focus on the cumulative evidence suggesting the existence of endosomes decorated by regulators that contribute to recycling in plant cells. We summarize the chemical inhibitors used for analysing cargo recycling and discuss recent advances in our understanding of how endocytic recycling participates in various plant cellular and physiological events.
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Affiliation(s)
- Wencai Qi
- College of Life Science, Henan Normal University, Xinxiang 453007, China
| | - Yu Zhang
- College of Life Science, Henan Normal University, Xinxiang 453007, China
| | - Mengting Li
- College of Life Science, Henan Normal University, Xinxiang 453007, China
| | - Peipei Zhang
- College of Life Science, Henan Normal University, Xinxiang 453007, China
| | - Jingjing Xing
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng 475004, China
| | - Yanmei Chen
- State Key Laboratory of Plant Environmental Resilience, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Liang Zhang
- College of Life Science, Henan Normal University, Xinxiang 453007, China
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2
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Kourkoulou A, Martzoukou O, Fischer R, Amillis S. A type II phosphatidylinositol-4-kinase coordinates sorting of cargo polarizing by endocytic recycling. Commun Biol 2024; 7:855. [PMID: 38997419 PMCID: PMC11245547 DOI: 10.1038/s42003-024-06553-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 07/04/2024] [Indexed: 07/14/2024] Open
Abstract
Depending on their phosphorylation status, derivatives of phosphatidylinositol play important roles in vesicle identity, recognition and intracellular trafficking processes. In eukaryotic cells, phosphatidylinositol-4 phosphate pools generated by specific kinases are key determinants of the conventional secretion pathways. Earlier work in yeast has classified phosphatidylinositol-4 kinases in two types, Stt4p and Pik1p belonging to type III and Lsb6p to type II, with distinct cellular localizations and functions. Eurotiomycetes appear to lack Pik1p homologues. In Aspergillus nidulans, unlike homologues in other fungi, AnLsb6 is associated to late Golgi membranes and when heterologously overexpressed, it compensates for the thermosensitive phenotype in a Saccharomyces cerevisiae pik1 mutant, whereas its depletion leads to disorganization of Golgi-associated PHOSBP-labelled membranes, that tend to aggregate dependent on functional Rab5 GTPases. Evidence provided herein, indicates that the single type II phosphatidylinositol-4 kinase AnLsb6 is the main contributor for decorating secretory vesicles with relevant phosphatidylinositol-phosphate species, which navigate essential cargoes following the route of apical polarization via endocytic recycling.
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Affiliation(s)
- Anezia Kourkoulou
- National and Kapodistrian University of Athens, Department of Biology, Athens, Hellas, Greece
| | - Olga Martzoukou
- National and Kapodistrian University of Athens, Department of Biology, Athens, Hellas, Greece
| | - Reinhard Fischer
- Karlsruhe Institute of Technology - South Campus, Institute for Applied Biosciences, Department of Microbiology, Karlsruhe, Germany
| | - Sotiris Amillis
- National and Kapodistrian University of Athens, Department of Biology, Athens, Hellas, Greece.
- Karlsruhe Institute of Technology - South Campus, Institute for Applied Biosciences, Department of Microbiology, Karlsruhe, Germany.
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3
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Georgiou X, Dimou S, Diallinas G, Samiotaki M. The interactome of the UapA transporter reveals putative new players in anterograde membrane cargo trafficking. Fungal Genet Biol 2023; 169:103840. [PMID: 37730157 DOI: 10.1016/j.fgb.2023.103840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 09/01/2023] [Accepted: 09/15/2023] [Indexed: 09/22/2023]
Abstract
Neosynthesized plasma membrane (PM) proteins co-translationally translocate to the ER, concentrate at regions called ER-exit sites (ERes) and pack into COPII secretory vesicles which are sorted to the early-Golgi through membrane fusion. Following Golgi maturation, membrane cargoes reach the late-Golgi, from where they exit in clathrin-coated vesicles destined to the PM, directly or through endosomes. Post-Golgi membrane cargo trafficking also involves the cytoskeleton and the exocyst. The Golgi-dependent secretory pathway is thought to be responsible for the trafficking of all major membrane proteins. However, our recent findings in Aspergillus nidulans showed that several plasma membrane cargoes, such as transporters and receptors, follow a sorting route that seems to bypass Golgi functioning. To gain insight on membrane trafficking and specifically Golgi-bypass, here we used proximity dependent biotinylation (PDB) coupled with data-independent acquisition mass spectrometry (DIA-MS) for identifying transient interactors of the UapA transporter. Our assays, which included proteomes of wild-type and mutant strains affecting ER-exit or endocytosis, identified both expected and novel interactions that might be physiologically relevant to UapA trafficking. Among those, we validated, using reverse genetics and fluorescence microscopy, that COPI coatomer is essential for ER-exit and anterograde trafficking of UapA and other membrane cargoes. We also showed that ArfAArf1 GTPase activating protein (GAP) Glo3 contributes to UapA trafficking at increased temperature. This is the first report addressing the identification of transient interactions during membrane cargo biogenesis using PDB and proteomics coupled with fungal genetics. Our work provides a basis for dissecting dynamic membrane cargo trafficking via PDB assays.
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Affiliation(s)
- Xenia Georgiou
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, Athens 15784, Greece
| | - Sofia Dimou
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, Athens 15784, Greece
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, Athens 15784, Greece; Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, Heraklion 70013, Greece.
| | - Martina Samiotaki
- Biomedical Sciences Research Center "Alexander Fleming", Institute for Bioinnovation, Vari 16672, Greece.
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4
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Wu C, Chen H, Yuan M, Zhang M, Abubakar YS, Chen X, Zhong H, Zheng W, Zheng H, Zhou J. FgAP1 σ Is Critical for Vegetative Growth, Conidiation, Virulence, and DON Biosynthesis in Fusarium graminearum. J Fungi (Basel) 2023; 9:jof9020145. [PMID: 36836259 PMCID: PMC9962196 DOI: 10.3390/jof9020145] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 01/17/2023] [Accepted: 01/19/2023] [Indexed: 01/24/2023] Open
Abstract
The AP1 complex is a highly conserved clathrin adaptor that plays important roles in regulating cargo protein sorting and intracellular vesicle trafficking in eukaryotes. However, the functions of the AP1 complex in the plant pathogenic fungi including the devastating wheat pathogen Fusarium graminearum are still unclear. In this study, we investigated the biological functions of FgAP1σ, a subunit of the AP1 complex in F. graminearum. Disruption of FgAP1σ causes seriously impaired fungal vegetative growth, conidiogenesis, sexual development, pathogenesis, and deoxynivalenol (DON) production. The ΔFgap1σ mutants were found to be less sensitive to KCl- and sorbitol-induced osmotic stresses but more sensitive to SDS-induced stress than the wild-type PH-1. Although the growth inhibition rate of the ΔFgap1σ mutants was not significantly changed under calcofluor white (CFW) and Congo red (CR) stresses, the protoplasts released from ΔFgap1σ hyphae were decreased compared with the wild-type PH-1, suggesting that FgAP1σ is necessary for cell wall integrity and osmotic stresses in F. graminearum. Subcellular localization assays showed that FgAP1σ was predominantly localized to endosomes and the Golgi apparatus. In addition, FgAP1β-GFP, FgAP1γ-GFP, and FgAP1μ-GFP also localize to the Golgi apparatus. FgAP1β interacts with FgAP1σ, FgAP1γ, and FgAP1μ, while FgAP1σ regulates the expression of FgAP1β, FgAP1γ, and FgAP1μ in F. graminearum. Furthermore, the loss of FgAP1σ blocks the transportation of the v-SNARE protein FgSnc1 from the Golgi to the plasma membrane and delays the internalization of FM4-64 dye into the vacuole. Taken together, our results demonstrate that FgAP1σ plays vital roles in vegetative growth, conidiogenesis, sexual reproduction, DON production, pathogenicity, cell wall integrity, osmotic stress, exocytosis, and endocytosis in F. graminearum. These findings unveil the functions of the AP1 complex in filamentous fungi, most notably in F. graminearum, and lay solid foundations for effective prevention and control of Fusarium head blight (FHB).
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Affiliation(s)
- Congxian Wu
- Fujian Universities Key Laboratory for Plant-Microbe Interaction, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Public Technology Service Center, Fujian Medical University, Fuzhou 350122, China
| | - Huilin Chen
- Fujian Universities Key Laboratory for Plant-Microbe Interaction, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Mingyue Yuan
- Fujian Universities Key Laboratory for Plant-Microbe Interaction, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Meiru Zhang
- Fujian Universities Key Laboratory for Plant-Microbe Interaction, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Yakubu Saddeeq Abubakar
- Fujian Universities Key Laboratory for Plant-Microbe Interaction, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Department of Biochemistry, Faculty of Life Sciences, Ahmadu Bello University, Zaria 810107, Nigeria
| | - Xin Chen
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Haoming Zhong
- Fujian Universities Key Laboratory for Plant-Microbe Interaction, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Wenhui Zheng
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Huawei Zheng
- Fujian Universities Key Laboratory for Plant-Microbe Interaction, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Institute of Oceanography, College of Geography and Oceanography, Minjiang University, Fuzhou 350108, China
- Correspondence: (H.Z.); (J.Z.)
| | - Jie Zhou
- Fujian Universities Key Laboratory for Plant-Microbe Interaction, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Correspondence: (H.Z.); (J.Z.)
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5
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Dionysopoulou M, Yan N, Wang B, Pliotas C, Diallinas G. Genetic and cellular characterization of MscS-like putative channels in the filamentous fungus Aspergillus nidulans. Channels (Austin) 2022; 16:148-158. [PMID: 35941834 PMCID: PMC9367656 DOI: 10.1080/19336950.2022.2098661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mechanosensitive ion channels are integral membrane proteins ubiquitously present in bacteria, archaea, and eukarya. They act as molecular sensors of mechanical stress to serve vital functions such as touch, hearing, osmotic pressure, proprioception and balance, while their malfunction is often associated with pathologies. Amongst them, the structurally distinct MscL and MscS channels from bacteria are the most extensively studied. MscS-like channels have been found in plants and Schizosaccharomyces pombe, where they regulate intracellular Ca2+ and cell volume under hypo-osmotic conditions. Here we characterize two MscS-like putative channels, named MscA and MscB, from the model filamentous fungus Aspergillus nidulans. Orthologues of MscA and MscB are present in most fungi, including relative plant and animal pathogens. MscA/MscB and other fungal MscS-like proteins share the three transmembrane helices and the extended C-terminal cytosolic domain that form the structural fingerprint of MscS-like channels with at least three additional transmembrane segments than Escherichia coli MscS. We show that MscA and MscB localize in Endoplasmic Reticulum and the Plasma Membrane, respectively, whereas their overexpression leads to increased CaCl2 toxicity or/and reduction of asexual spore formation. Our findings contribute to understanding the role of MscS-like channels in filamentous fungi and relative pathogens.
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Affiliation(s)
- Mariangela Dionysopoulou
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds, LS2 9JT, Leeds, United Kingdom.,Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, 15784 Athens, Greece
| | - Nana Yan
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds, LS2 9JT, Leeds, United Kingdom
| | - Bolin Wang
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds, LS2 9JT, Leeds, United Kingdom
| | - Christos Pliotas
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds, LS2 9JT, Leeds, United Kingdom
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, 15784 Athens, Greece.,Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, 70013 Heraklion, Greece
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Chitin Synthesis in Yeast: A Matter of Trafficking. Int J Mol Sci 2022; 23:ijms232012251. [PMID: 36293107 PMCID: PMC9603707 DOI: 10.3390/ijms232012251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 10/11/2022] [Accepted: 10/11/2022] [Indexed: 01/24/2023] Open
Abstract
Chitin synthesis has attracted scientific interest for decades as an essential part of fungal biology and for its potential as a target for antifungal therapies. While this interest remains, three decades ago, pioneering molecular studies on chitin synthesis regulation identified the major chitin synthase in yeast, Chs3, as an authentic paradigm in the field of the intracellular trafficking of integral membrane proteins. Over the years, researchers have shown how the intracellular trafficking of Chs3 recapitulates all the steps in the intracellular trafficking of integral membrane proteins, from their synthesis in the endoplasmic reticulum to their degradation in the vacuole. This trafficking includes specific mechanisms for sorting in the trans-Golgi network, regulated endocytosis, and endosomal recycling at different levels. This review summarizes the work carried out on chitin synthesis regulation, mostly focusing on Chs3 as a molecular model to study the mechanisms involved in the control of the intracellular trafficking of proteins.
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7
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Dimakis D, Pyrris Y, Diallinas G. Transmembrane helices 5 and 12 control transport dynamics, substrate affinity, and specificity in the elevator-type UapA transporter. Genetics 2022; 222:6650625. [PMID: 35894659 PMCID: PMC9434233 DOI: 10.1093/genetics/iyac107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 07/11/2022] [Indexed: 01/17/2023] Open
Abstract
An increasing number of solute transporters have been shown to function with the so-called sliding-elevator mechanism. Despite structural and functional differences, all elevator-type transporters use a common mechanism of substrate translocation via reversible movements of a mobile core domain (the elevator) hosting the substrate binding site along a rigid scaffold domain stably anchored in the plasma membrane via homodimerization. One of the best-studied elevator transporters is the UapA uric acid-xanthine/H+ symporter of the filamentous fungus Aspergillus nidulans. Here, we present a genetic analysis for deciphering the role of transmembrane segments (TMS) 5 and 12 in UapA transport function. We show that specific residues in both TMS5 and TMS12 control, negatively or positively, the dynamics of transport, but also substrate binding affinity and specificity. More specifically, mutations in TMS5 can lead not only to increased rate of transport but also to an inactive transporter due to high-affinity substrate-trapping, whereas mutations in TMS12 lead to apparently uncontrolled sliding and broadened specificity, leading in specific cases to UapA-mediated purine toxicity. Our findings shed new light on how elevator transporters function and how this knowledge can be applied to genetically modify their transport characteristics.
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Affiliation(s)
- Dimitris Dimakis
- Department of Biology, National and Kapodistrian University of Athens, 15784 Athens, Greece
| | - Yiannis Pyrris
- Department of Biology, National and Kapodistrian University of Athens, 15784 Athens, Greece
| | - George Diallinas
- Corresponding author: Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, 15784 Athens, Greece.
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8
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Xu M, Yan X, Wang Y, Liu C, Yang Q, Tian D, Bednarek SY, Pan J, Wang C. ADAPTOR PROTEIN-1 complex-mediated post-Golgi trafficking is critical for pollen wall development in Arabidopsis. THE NEW PHYTOLOGIST 2022; 235:472-487. [PMID: 35451504 PMCID: PMC9545562 DOI: 10.1111/nph.18170] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 03/09/2022] [Indexed: 05/16/2023]
Abstract
Primexine deposition is essential for the formation of pollen wall patterns and is precisely regulated by the tapetum and microspores. While tapetum- and/or microspore-localized proteins are required for primexine biosynthesis, how their trafficking is established and controlled is poorly understood. In Arabidopsis thaliana, AP1σ1 and AP1σ2, two genes encoding the σ subunit of the trans-Golgi network/early endosome (TGN/EE)-localized ADAPTOR PROTEIN-1 complex (AP-1), are partially redundant for plant viability, and the loss of AP1σ1 function reduces male fertility due to defective primexine formation. Here, we investigated the role of AP-1 in pollen wall formation. The deposition of Acyl-CoA SYNTHETASE5 (ACOS5) and type III LIPID TRANSFER PROTEINs (LTPs) secreted from the anther tapetum, which are involved in exine formation, were impaired in ap1σ1 mutants. In addition, the microspore plasma membrane (PM) protein RUPTURED POLLEN GRAIN1 (RPG1), which regulates primexine deposition, accumulated abnormally at the TGN/EE in ap1σ1 mutants. We show that AP-1μ recognizes the YXXΦ motif of RPG1, thereby regulating its PM abundance through endocytic trafficking, and that loss of AP1σ1 decreases the levels of other AP-1 subunits at the TGN/EE. Our observations show that AP-1-mediated post-Golgi trafficking plays a vital role in pollen wall development by regulating protein transport in tapetal cells and microspores.
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Affiliation(s)
- Mei Xu
- Ministry of Education Key Laboratory of Cell Activities and Stress AdaptationsSchool of Life SciencesLanzhou UniversityLanzhou730000China
| | - Xu Yan
- Ministry of Education Key Laboratory of Cell Activities and Stress AdaptationsSchool of Life SciencesLanzhou UniversityLanzhou730000China
| | - Yutong Wang
- Ministry of Education Key Laboratory of Cell Activities and Stress AdaptationsSchool of Life SciencesLanzhou UniversityLanzhou730000China
| | - Chan Liu
- Ministry of Education Key Laboratory of Cell Activities and Stress AdaptationsSchool of Life SciencesLanzhou UniversityLanzhou730000China
| | - Qian Yang
- Ministry of Education Key Laboratory of Cell Activities and Stress AdaptationsSchool of Life SciencesLanzhou UniversityLanzhou730000China
| | - Dan Tian
- Ministry of Education Key Laboratory of Cell Activities and Stress AdaptationsSchool of Life SciencesLanzhou UniversityLanzhou730000China
| | | | - Jianwei Pan
- Ministry of Education Key Laboratory of Cell Activities and Stress AdaptationsSchool of Life SciencesLanzhou UniversityLanzhou730000China
| | - Chao Wang
- Ministry of Education Key Laboratory of Cell Activities and Stress AdaptationsSchool of Life SciencesLanzhou UniversityLanzhou730000China
- College of Life SciencesShaoxing UniversityShaoxingZhejiang312000China
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9
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Duncan MC. New directions for the clathrin adaptor AP-1 in cell biology and human disease. Curr Opin Cell Biol 2022; 76:102079. [DOI: 10.1016/j.ceb.2022.102079] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 03/02/2022] [Accepted: 03/03/2022] [Indexed: 11/03/2022]
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10
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Dimou S, Dionysopoulou M, Sagia GM, Diallinas G. Golgi-Bypass Is a Major Unconventional Route for Translocation to the Plasma Membrane of Non-Apical Membrane Cargoes in Aspergillus nidulans. Front Cell Dev Biol 2022; 10:852028. [PMID: 35465316 PMCID: PMC9021693 DOI: 10.3389/fcell.2022.852028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Accepted: 03/03/2022] [Indexed: 11/13/2022] Open
Abstract
Nutrient transporters have been shown to translocate to the plasma membrane (PM) of the filamentous fungus Aspergillus nidulans via an unconventional trafficking route that bypasses the Golgi. This finding strongly suggests the existence of distinct COPII vesicle subpopulations, one following Golgi-dependent conventional secretion and the other directed towards the PM. Here, we address whether Golgi-bypass concerns cargoes other than nutrient transporters and whether Golgi-bypass is related to cargo structure, size, abundance, physiological function, or polar vs. non-polar distribution in the PM. To address these questions, we followed the dynamic subcellular localization of two selected membrane cargoes differing in several of the aforementioned aspects. These are the proton-pump ATPase PmaA and the PalI pH signaling component. Our results show that neosynthesized PmaA and PalI are translocated to the PM via Golgi-bypass, similar to nutrient transporters. In addition, we showed that the COPII-dependent exit of PmaA from the ER requires the alternative COPII coat subunit LstA, rather than Sec24, whereas PalI requires the ER cargo adaptor Erv14. These findings strengthen the evidence of distinct cargo-specific COPII subpopulations and extend the concept of Golgi-independent biogenesis to essential transmembrane proteins, other than nutrient transporters. Overall, our findings point to the idea that Golgi-bypass might not constitute a fungal-specific peculiarity, but rather a novel major and cargo-specific sorting route in eukaryotic cells that has been largely ignored.
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Affiliation(s)
- Sofia Dimou
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, Athens, Greece
| | - Mariangela Dionysopoulou
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, Athens, Greece
| | - Georgia Maria Sagia
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, Athens, Greece
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, Athens, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, Heraklion, Greece
- *Correspondence: George Diallinas,
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11
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Yan X, Wang Y, Xu M, Dahhan DA, Liu C, Zhang Y, Lin J, Bednarek SY, Pan J. Cross-talk between clathrin-dependent post-Golgi trafficking and clathrin-mediated endocytosis in Arabidopsis root cells. THE PLANT CELL 2021; 33:3057-3075. [PMID: 34240193 PMCID: PMC8462817 DOI: 10.1093/plcell/koab180] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 06/30/2021] [Indexed: 05/26/2023]
Abstract
Coupling of post-Golgi and endocytic membrane transport ensures that the flow of materials to/from the plasma membrane (PM) is properly balanced. The mechanisms underlying the coordinated trafficking of PM proteins in plants, however, are not well understood. In plant cells, clathrin and its adaptor protein complexes, AP-2 and the TPLATE complex (TPC) at the PM, and AP-1 at the trans-Golgi network/early endosome (TGN/EE), function in clathrin-mediated endocytosis (CME) and post-Golgi trafficking. Here, we utilized mutants with defects in clathrin-dependent post-Golgi trafficking and CME, in combination with other cytological and pharmacological approaches, to further investigate the machinery behind the coordination of protein delivery and recycling to/from the TGN/EE and PM in Arabidopsis (Arabidopsis thaliana) root cells. In mutants with defective AP-2-/TPC-dependent CME, we determined that clathrin and AP-1 recruitment to the TGN/EE as well as exocytosis are significantly impaired. Likewise, defects in AP-1-dependent post-Golgi trafficking and pharmacological inhibition of exocytosis resulted in the reduced association of clathrin and AP-2/TPC subunits with the PM and a reduction in the internalization of cargoes via CME. Together, these results suggest that post-Golgi trafficking and CME are coupled via modulation of clathrin and adaptor protein complex recruitment to the TGN/EE and PM.
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Affiliation(s)
- Xu Yan
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Yutong Wang
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Mei Xu
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Dana A. Dahhan
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin 53706
| | - Chan Liu
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Yan Zhang
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai’an 271018, China
| | - Jinxing Lin
- College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing 100083, China
| | - Sebastian Y. Bednarek
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin 53706
| | - Jianwei Pan
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
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12
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Anton-Plagaro C, Sanchez N, Valle R, Mulet JM, Duncan MC, Roncero C. Exomer complex regulates protein traffic at the TGN through differential interactions with cargos and clathrin adaptor complexes. FASEB J 2021; 35:e21615. [PMID: 33978245 DOI: 10.1096/fj.202002610r] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 04/01/2021] [Accepted: 04/07/2021] [Indexed: 12/16/2022]
Abstract
Protein sorting at the trans-Golgi network (TGN) usually requires the assistance of cargo adaptors. However, it remains to be examined how the same complex can mediate both the export and retention of different proteins or how sorting complexes interact among themselves. In Saccharomyces cerevisiae, the exomer complex is involved in the polarized transport of some proteins from the TGN to the plasma membrane (PM). Intriguingly, exomer and its cargos also show a sort of functional relationship with TGN clathrin adaptors that is still unsolved. Here, using a wide range of techniques, including time-lapse and BIFC microscopy, we describe new molecular implications of the exomer complex in protein sorting and address its different layers of functional interaction with clathrin adaptor complexes. Exomer mutants show impaired amino acid uptake because it facilitates not only the polarized delivery of amino acid permeases to the PM but also participates in their endosomal traffic. We propose a model for exomer where it modulates the recruitment of TGN clathrin adaptors directly or indirectly through the Arf1 function. Moreover, we describe an in vivo competitive relationship between the exomer and AP-1 complexes for the model cargo Chs3. These results highlight a broad role for exomer in regulating protein sorting at the TGN that is complementary to its role as cargo adaptor and present a model to understand the complexity of TGN protein sorting.
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Affiliation(s)
- Carlos Anton-Plagaro
- Instituto de Biología Funcional y Genómica (IBFG) and Departamento de Microbiología y Genética, CSIC-Universidad de Salamanca, Salamanca, Spain
| | - Noelia Sanchez
- Instituto de Biología Funcional y Genómica (IBFG) and Departamento de Microbiología y Genética, CSIC-Universidad de Salamanca, Salamanca, Spain
| | - Rosario Valle
- Instituto de Biología Funcional y Genómica (IBFG) and Departamento de Microbiología y Genética, CSIC-Universidad de Salamanca, Salamanca, Spain
| | - Jose Miguel Mulet
- Instituto de Biología Molecular y Celular de Plantas, CSIC-Universitat Politècnica de València, Valencia, Spain
| | - Mara C Duncan
- Cell and Developmental Biology Department, University of Michigan, Ann Arbor, MI, USA
| | - Cesar Roncero
- Instituto de Biología Funcional y Genómica (IBFG) and Departamento de Microbiología y Genética, CSIC-Universidad de Salamanca, Salamanca, Spain
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13
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Impact of Membrane Lipids on UapA and AzgA Transporter Subcellular Localization and Activity in Aspergillus nidulans. J Fungi (Basel) 2021; 7:jof7070514. [PMID: 34203131 PMCID: PMC8304608 DOI: 10.3390/jof7070514] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 06/24/2021] [Accepted: 06/24/2021] [Indexed: 12/21/2022] Open
Abstract
Recent biochemical and biophysical evidence have established that membrane lipids, namely phospholipids, sphingolipids and sterols, are critical for the function of eukaryotic plasma membrane transporters. Here, we study the effect of selected membrane lipid biosynthesis mutations and of the ergosterol-related antifungal itraconazole on the subcellular localization, stability and transport kinetics of two well-studied purine transporters, UapA and AzgA, in Aspergillus nidulans. We show that genetic reduction in biosynthesis of ergosterol, sphingolipids or phosphoinositides arrest A. nidulans growth after germling formation, but solely blocks in early steps of ergosterol (Erg11) or sphingolipid (BasA) synthesis have a negative effect on plasma membrane (PM) localization and stability of transporters before growth arrest. Surprisingly, the fraction of UapA or AzgA that reaches the PM in lipid biosynthesis mutants is shown to conserve normal apparent transport kinetics. We further show that turnover of UapA, which is the transporter mostly sensitive to membrane lipid content modification, occurs during its trafficking and by enhanced endocytosis, and is partly dependent on autophagy and Hect-type HulARsp5 ubiquitination. Our results point out that the role of specific membrane lipids on transporter biogenesis and function in vivo is complex, combinatorial and transporter-dependent.
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14
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Pinar M, Peñalva MA. The fungal RABOME: RAB GTPases acting in the endocytic and exocytic pathways of Aspergillus nidulans (with excursions to other filamentous fungi). Mol Microbiol 2021; 116:53-70. [PMID: 33724562 DOI: 10.1111/mmi.14716] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 03/04/2021] [Accepted: 03/11/2021] [Indexed: 10/21/2022]
Abstract
RAB GTPases are major determinants of membrane identity that have been exploited as highly specific reporters to study intracellular traffic in vivo. A score of fungal papers have considered individual RABs, but systematic, integrated studies on the localization and physiological role of these regulators and their effectors have been performed only with Aspergillus nidulans. These studies have influenced the intracellular trafficking field beyond fungal specialists, leading to findings such as the maturation of trans-Golgi (TGN) cisternae into post-Golgi RAB11 secretory vesicles, the concept that these RAB11 secretory carriers are loaded with three molecular nanomotors, the understanding of the role of endocytic recycling mediated by RAB6 and RAB11 in determining the hyphal mode of life, the discovery that early endosome maturation and the ESCRT pathway are essential, the identification of specific adaptors of dynein-dynactin to RAB5 endosomes, the exquisite dependence that autophagy displays on RAB1 activity, the role of TRAPPII as a GEF for RAB11, or the conclusion that the RAB1-to-RAB11 transition is not mediated by TRAPP maturation. A remarkable finding was that the A. nidulans Spitzenkörper contains four RABs: RAB11, Sec4, RAB6, and RAB1. How these RABs cooperate during exocytosis represents an as yet outstanding question.
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Affiliation(s)
- Mario Pinar
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas Margarita Salas, CSIC, Madrid, Spain
| | - Miguel A Peñalva
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas Margarita Salas, CSIC, Madrid, Spain
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15
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Endocytosis of nutrient transporters in fungi: The ART of connecting signaling and trafficking. Comput Struct Biotechnol J 2021; 19:1713-1737. [PMID: 33897977 PMCID: PMC8050425 DOI: 10.1016/j.csbj.2021.03.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Revised: 03/14/2021] [Accepted: 03/14/2021] [Indexed: 12/11/2022] Open
Abstract
Plasma membrane transporters play pivotal roles in the import of nutrients, including sugars, amino acids, nucleobases, carboxylic acids, and metal ions, that surround fungal cells. The selective removal of these transporters by endocytosis is one of the most important regulatory mechanisms that ensures a rapid adaptation of cells to the changing environment (e.g., nutrient fluctuations or different stresses). At the heart of this mechanism lies a network of proteins that includes the arrestin‐related trafficking adaptors (ARTs) which link the ubiquitin ligase Rsp5 to nutrient transporters and endocytic factors. Transporter conformational changes, as well as dynamic interactions between its cytosolic termini/loops and with lipids of the plasma membrane, are also critical during the endocytic process. Here, we review the current knowledge and recent findings on the molecular mechanisms involved in nutrient transporter endocytosis, both in the budding yeast Saccharomyces cerevisiae and in some species of the filamentous fungus Aspergillus. We elaborate on the physiological importance of tightly regulated endocytosis for cellular fitness under dynamic conditions found in nature and highlight how further understanding and engineering of this process is essential to maximize titer, rate and yield (TRY)-values of engineered cell factories in industrial biotechnological processes.
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Key Words
- AAs, amino acids
- ACT, amino Acid/Choline Transporter
- AP, adaptor protein
- APC, amino acid-polyamine-organocation
- Arg, arginine
- Arrestins
- Arts, arrestin‐related trafficking adaptors
- Asp, aspartic acid
- Aspergilli
- Biotechnology
- C, carbon
- C-terminus, carboxyl-terminus
- Cell factories
- Conformational changes
- Cu, copper
- DUBs, deubiquitinating enzymes
- EMCs, eisosome membrane compartments
- ER, endoplasmic reticulum
- ESCRT, endosomal sorting complex required for transport
- Endocytic signals
- Endocytosis
- Fe, iron
- Fungi
- GAAC, general amino acid control
- Glu, glutamic acid
- H+, proton
- IF, inward-facing
- LAT, L-type Amino acid Transporter
- LID, loop Interaction Domain
- Lys, lysine
- MCCs, membrane compartments containing the arginine permease Can1
- MCCs/eisosomes
- MCPs, membrane compartments of Pma1
- MFS, major facilitator superfamily
- MVB, multi vesicular bodies
- Met, methionine
- Metabolism
- Mn, manganese
- N, nitrogen
- N-terminus, amino-terminus
- NAT, nucleobase Ascorbate Transporter
- NCS1, nucleobase/Cation Symporter 1
- NCS2, nucleobase cation symporter family 2
- NH4+, ammonium
- Nutrient transporters
- OF, outward-facing
- PEST, proline (P), glutamic acid (E), serine (S), and threonine (T)
- PM, plasma membrane
- PVE, prevacuolar endosome
- Saccharomyces cerevisiae
- Signaling pathways
- Structure-function
- TGN, trans-Golgi network
- TMSs, transmembrane segments
- TORC1, target of rapamycin complex 1
- TRY, titer, rate and yield
- Trp, tryptophan
- Tyr, tyrosine
- Ub, ubiquitin
- Ubiquitylation
- VPS, vacuolar protein sorting
- W/V, weight per volume
- YAT, yeast Amino acid Transporter
- Zn, Zinc
- fAATs, fungal AA transporters
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16
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Buelto D, Hung CW, Aoh QL, Lahiri S, Duncan MC. Plasma membrane to vacuole traffic induced by glucose starvation requires Gga2-dependent sorting at the trans-Golgi network. Biol Cell 2020; 112:349-367. [PMID: 32761633 DOI: 10.1111/boc.202000058] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 07/27/2020] [Indexed: 12/17/2022]
Abstract
BACKGROUND INFORMATION In the yeast Saccharomyces cerevisiae, acute glucose starvation induces rapid endocytosis followed by vacuolar degradation of many plasma membrane proteins. This process is essential for cell viability, but the regulatory mechanisms that control it remain poorly understood. Under normal growth conditions, a major regulatory decision for endocytic cargo occurs at the trans-Golgi network (TGN) where proteins can recycle back to the plasma membrane or can be recognized by TGN-localised clathrin adaptors that direct them towards the vacuole. However, glucose starvation reduces recycling and alters the localization and post-translational modification of TGN-localised clathrin adaptors. This raises the possibility that during glucose starvation endocytosed proteins are routed to the vacuole by a novel mechanism that bypasses the TGN or does not require TGN-localised clathrin adaptors. RESULTS Here, we investigate the role of TGN-localised clathrin adaptors in the traffic of several amino acid permeases, including Can1, during glucose starvation. We find that Can1 transits through the TGN after endocytosis in both starved and normal conditions. Can1 and other amino acid permeases require TGN-localised clathrin adaptors for maximal delivery to the vacuole. Furthermore, these permeases are actively sorted to the vacuole, because ectopically forced de-ubiquitination at the TGN results in the recycling of the Tat1 permase in starved cells. Finally, we report that the Mup1 permease requires the clathrin adaptor Gga2 for vacuolar delivery. In contrast, the clathrin adaptor protein complex AP-1 plays a minor role, potentially in retaining permeases in the TGN, but it is otherwise dispensable for vacuolar delivery. CONCLUSIONS AND SIGNIFICANCE This work elucidates one membrane trafficking pathway needed for yeast to respond to acute glucose starvation. It also reveals the functions of TGNlocalised clathrin adaptors in this process. Our results indicate that the same machinery is needed for vacuolar protein sorting at the GN in glucose starved cells as is needed in the presence of glucose. In addition, our findings provide further support for the model that the TGN is a transit point for many endocytosed proteins, and that Gga2 and AP-1 function in distinct pathways at the TGN.
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Affiliation(s)
- Destiney Buelto
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.,Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Chao-Wei Hung
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.,Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Quyen L Aoh
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Sagar Lahiri
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Mara C Duncan
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
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17
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Dimou S, Diallinas G. Life and Death of Fungal Transporters under the Challenge of Polarity. Int J Mol Sci 2020; 21:ijms21155376. [PMID: 32751072 PMCID: PMC7432044 DOI: 10.3390/ijms21155376] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 07/24/2020] [Accepted: 07/27/2020] [Indexed: 12/14/2022] Open
Abstract
Eukaryotic plasma membrane (PM) transporters face critical challenges that are not widely present in prokaryotes. The two most important issues are proper subcellular traffic and targeting to the PM, and regulated endocytosis in response to physiological, developmental, or stress signals. Sorting of transporters from their site of synthesis, the endoplasmic reticulum (ER), to the PM has been long thought, but not formally shown, to occur via the conventional Golgi-dependent vesicular secretory pathway. Endocytosis of specific eukaryotic transporters has been studied more systematically and shown to involve ubiquitination, internalization, and sorting to early endosomes, followed by turnover in the multivesicular bodies (MVB)/lysosomes/vacuole system. In specific cases, internalized transporters have been shown to recycle back to the PM. However, the mechanisms of transporter forward trafficking and turnover have been overturned recently through systematic work in the model fungus Aspergillus nidulans. In this review, we present evidence that shows that transporter traffic to the PM takes place through Golgi bypass and transporter endocytosis operates via a mechanism that is distinct from that of recycling membrane cargoes essential for fungal growth. We discuss these findings in relation to adaptation to challenges imposed by cell polarity in fungi as well as in other eukaryotes and provide a rationale of why transporters and possibly other housekeeping membrane proteins ‘avoid’ routes of polar trafficking.
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18
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Dimou S, Martzoukou O, Dionysopoulou M, Bouris V, Amillis S, Diallinas G. Translocation of nutrient transporters to cell membrane via Golgi bypass in Aspergillus nidulans. EMBO Rep 2020; 21:e49929. [PMID: 32452614 DOI: 10.15252/embr.201949929] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 04/15/2020] [Accepted: 04/24/2020] [Indexed: 02/06/2023] Open
Abstract
Nutrient transporters, being polytopic membrane proteins, are believed, but not formally shown, to traffic from their site of synthesis, the ER, to the plasma membrane through Golgi-dependent vesicular trafficking. Here, we develop a novel genetic system to investigate the trafficking of a neosynthesized model transporter, the well-studied UapA purine transporter of Aspergillus nidulans. We show that sorting of neosynthesized UapA to the plasma membrane (PM) bypasses the Golgi and does not necessitate key Rab GTPases, AP adaptors, microtubules or endosomes. UapA PM localization is found to be dependent on functional COPII vesicles, actin polymerization, clathrin heavy chain and the PM t-SNARE SsoA. Actin polymerization proved to primarily affect COPII vesicle formation, whereas the essential role of ClaH seems indirect and less clear. We provide evidence that other evolutionary and functionally distinct transporters of A. nidulans also follow the herein identified Golgi-independent trafficking route of UapA. Importantly, our findings suggest that specific membrane cargoes drive the formation of distinct COPII subpopulations that bypass the Golgi to be sorted non-polarly to the PM, and thus serving house-keeping cell functions.
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Affiliation(s)
- Sofia Dimou
- Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
| | - Olga Martzoukou
- Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
| | | | - Vangelis Bouris
- Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
| | - Sotiris Amillis
- Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
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19
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Diallinas G, Martzoukou O. Transporter membrane traffic and function: lessons from a mould. FEBS J 2019; 286:4861-4875. [DOI: 10.1111/febs.15078] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 08/26/2019] [Accepted: 09/30/2019] [Indexed: 12/16/2022]
Affiliation(s)
- George Diallinas
- Department of Biology National and Kapodistrian University of Athens Greece
| | - Olga Martzoukou
- Department of Biology National and Kapodistrian University of Athens Greece
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20
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Aspergillus nidulans in the post-genomic era: a top-model filamentous fungus for the study of signaling and homeostasis mechanisms. Int Microbiol 2019; 23:5-22. [DOI: 10.1007/s10123-019-00064-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 01/30/2019] [Accepted: 02/04/2019] [Indexed: 02/07/2023]
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21
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Hernández-González M, Bravo-Plaza I, de Los Ríos V, Pinar M, Pantazopoulou A, Peñalva MA. COPI localizes to the early Golgi in Aspergillus nidulans. Fungal Genet Biol 2018; 123:78-86. [PMID: 30550852 DOI: 10.1016/j.fgb.2018.12.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 12/07/2018] [Accepted: 12/08/2018] [Indexed: 01/21/2023]
Abstract
Coatomer-I (COPI) is a heteromeric protein coat that facilitates the budding of membranous carriers mediating Golgi-to-ER and intra-Golgi transport. While the structural features of COPI have been thoroughly investigated, its physiological role is insufficiently understood. Here we exploit the amenability of A. nidulans for studying intracellular traffic, taking up previous studies by Breakspear et al. (2007) with the α-COP/CopA subunit of COPI. Endogenously tagged α-COP/CopA largely localizes to SedVSed5 syntaxin-containing early Golgi cisterna, and acute inactivation of ER-to-Golgi traffic delocalizes COPI to a haze, consistent with the cisternal maturation model. In contrast, the Golgi localization of COPI is independent of the TGN regulators HypBSec7 and HypATrs120, implying that COPI budding predominates at the SedVSed5 early Golgi, with lesser contribution of the TGN. This finding agrees with the proposed role of COPI-mediated intra-Golgi retrograde traffic in driving cisternal maturation, which predicts that the capacity of the TGN to generate COPI carriers is low. The COPI early Golgi compartments intimately associates with Sec13-containing ER exit sites. Characterization of the heat-sensitive copA1ts (sodVIC1) mutation showed that it results in a single residue substitution in the ε-COP-binding Carboxyl-Terminal-Domain of α-COP that likely destabilizes its folding. However, we show that Golgi disorganization by copA1ts necessitates >150 min-long incubation at 42 °C. This weak subcellular phenotype makes it unsuitable for inactivating COPI traffic acutely for microscopy studies, and explains the aneuploidy-stabilizing role of the mutation at subrestrictive temperatures.
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Affiliation(s)
- Miguel Hernández-González
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas CSIC, Ramiro de Maeztu 9, Madrid 28040, Spain; Centre for Mechanochemical Cell Biology, Gibbet Hill Road, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK(1)
| | - Ignacio Bravo-Plaza
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas CSIC, Ramiro de Maeztu 9, Madrid 28040, Spain
| | - Vivian de Los Ríos
- Proteomics and Genomics Facility, Centro de Investigaciones Biológicas CSIC, Ramiro de Maeztu 9, Madrid 28040, Spain
| | - Mario Pinar
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas CSIC, Ramiro de Maeztu 9, Madrid 28040, Spain
| | - Areti Pantazopoulou
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas CSIC, Ramiro de Maeztu 9, Madrid 28040, Spain; Department of Molecular Genetics and Cell Biology, Biological Sciences Division, The University of Chicago, United States(1).
| | - Miguel A Peñalva
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas CSIC, Ramiro de Maeztu 9, Madrid 28040, Spain.
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