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Tempes A, Bogusz K, Brzozowska A, Weslawski J, Macias M, Tkaczyk O, Orzoł K, Lew A, Calka-Kresa M, Bernas T, Szczepankiewicz AA, Mlostek M, Kumari S, Liszewska E, Machnicka K, Bakun M, Rubel T, Malik AR, Jaworski J. Autophagy initiation triggers p150 Glued-AP-2β interaction on the lysosomes and facilitates their transport. Cell Mol Life Sci 2024; 81:218. [PMID: 38758395 PMCID: PMC11101406 DOI: 10.1007/s00018-024-05256-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Revised: 01/25/2024] [Accepted: 04/15/2024] [Indexed: 05/18/2024]
Abstract
The endocytic adaptor protein 2 (AP-2) complex binds dynactin as part of its noncanonical function, which is necessary for dynein-driven autophagosome transport along microtubules in neuronal axons. The absence of this AP-2-dependent transport causes neuronal morphology simplification and neurodegeneration. The mechanisms that lead to formation of the AP-2-dynactin complex have not been studied to date. However, the inhibition of mammalian/mechanistic target of rapamycin complex 1 (mTORC1) enhances the transport of newly formed autophagosomes by influencing the biogenesis and protein interactions of Rab-interacting lysosomal protein (RILP), another dynein cargo adaptor. We tested effects of mTORC1 inhibition on interactions between the AP-2 and dynactin complexes, with a focus on their two essential subunits, AP-2β and p150Glued. We found that the mTORC1 inhibitor rapamycin enhanced p150Glued-AP-2β complex formation in both neurons and non-neuronal cells. Additional analysis revealed that the p150Glued-AP-2β interaction was indirect and required integrity of the dynactin complex. In non-neuronal cells rapamycin-driven enhancement of the p150Glued-AP-2β interaction also required the presence of cytoplasmic linker protein 170 (CLIP-170), the activation of autophagy, and an undisturbed endolysosomal system. The rapamycin-dependent p150Glued-AP-2β interaction occurred on lysosomal-associated membrane protein 1 (Lamp-1)-positive organelles but without the need for autolysosome formation. Rapamycin treatment also increased the acidification and number of acidic organelles and increased speed of the long-distance retrograde movement of Lamp-1-positive organelles. Altogether, our results indicate that autophagy regulates the p150Glued-AP-2β interaction, possibly to coordinate sufficient motor-adaptor complex availability for effective lysosome transport.
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Affiliation(s)
- Aleksandra Tempes
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, Ks. Trojdena St. 4, 02-109, Warsaw, Poland
| | - Karolina Bogusz
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, Ks. Trojdena St. 4, 02-109, Warsaw, Poland
| | - Agnieszka Brzozowska
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, Ks. Trojdena St. 4, 02-109, Warsaw, Poland
| | - Jan Weslawski
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, Ks. Trojdena St. 4, 02-109, Warsaw, Poland
| | - Matylda Macias
- Microscopy and Flow Cytometry Core Facility, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Oliver Tkaczyk
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, Ks. Trojdena St. 4, 02-109, Warsaw, Poland
| | - Katarzyna Orzoł
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, Ks. Trojdena St. 4, 02-109, Warsaw, Poland
| | - Aleksandra Lew
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, Ks. Trojdena St. 4, 02-109, Warsaw, Poland
| | | | - Tytus Bernas
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
- Microscopy Facility, Department of Anatomy and Neurology, Virginia Commonwealth University School of Medicine, Richmond, VA, USA
| | | | - Magdalena Mlostek
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, Ks. Trojdena St. 4, 02-109, Warsaw, Poland
| | - Shiwani Kumari
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, Ks. Trojdena St. 4, 02-109, Warsaw, Poland
| | - Ewa Liszewska
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, Ks. Trojdena St. 4, 02-109, Warsaw, Poland
| | - Katarzyna Machnicka
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, Ks. Trojdena St. 4, 02-109, Warsaw, Poland
| | - Magdalena Bakun
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - Tymon Rubel
- Institute of Radioelectronics and Multimedia Technology, Warsaw University of Technology, Warsaw, Poland
| | - Anna R Malik
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, Ks. Trojdena St. 4, 02-109, Warsaw, Poland.
- Cellular Neurobiology Research Group, Institute of Developmental Biology and Biomedical Sciences, Faculty of Biology, University of Warsaw, Miecznikowa St. 1, 02-096, Warsaw, Poland.
| | - Jacek Jaworski
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, Ks. Trojdena St. 4, 02-109, Warsaw, Poland.
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Cirillo S, Zhang B, Brown S, Zhao X. Antimicrobial peptide A 9K as a gene delivery vector in cancer cells. Eur J Pharm Biopharm 2024; 198:114244. [PMID: 38467336 DOI: 10.1016/j.ejpb.2024.114244] [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: 12/11/2023] [Revised: 02/24/2024] [Accepted: 03/04/2024] [Indexed: 03/13/2024]
Abstract
Designed peptides are promising biomaterials for biomedical applications. The amphiphilic cationic antimicrobial peptide (AMP), A9K, can self-assemble into nano-rod structures and has shown cancer cell selectivity and could therefore be a promising candidate for therapeutic delivery into cancer cells. In this paper, we investigate the selectivity of A9K for cancer cell models, examining its effect on two human cancer cell lines, A431 and HCT-116. Little or no activity was observed on the control, human dermal fibroblasts (HDFs). In the cancer cell lines the peptide inhibited cellular growth through changes in mitochondrial morphology and membrane potential while remaining harmless towards HDFs. In addition, the peptide can bind to and protect nucleic acids while transporting them into both 2D cultures and 3D spheroids of cancer cells. A9K showed high efficiency in delivering siRNA molecules into the centre of the spheroids. A9K was also explored in vivo, using a zebrafish (Danio rerio) development toxicity assay, showing that the peptide is safe at low doses. Finally, a high-content imaging screen, using RNA interference (RNAi) targeted towards cellular uptake, in HCT-116 cells was carried out. Our findings suggest that active cellular uptake is involved in peptide internalisation, mediated through clathrin-mediated endocytosis. These new discoveries make A9K attractive for future developments in clinical and biotechnological applications.
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Affiliation(s)
- Silvia Cirillo
- Department of Chemical and Biological Engineering, University of Sheffield, Sheffield S1 3JD, UK
| | - Bo Zhang
- School of Pharmacy, Changzhou University, Changzhou 213164, China
| | - Stephen Brown
- The Sheffield RNAi Screening Facility, Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK
| | - Xiubo Zhao
- Department of Chemical and Biological Engineering, University of Sheffield, Sheffield S1 3JD, UK; School of Pharmacy, Changzhou University, Changzhou 213164, China.
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Fisher CG, Falk MM. Endocytosis and Endocytic Motifs across the Connexin Gene Family. Int J Mol Sci 2023; 24:12851. [PMID: 37629031 PMCID: PMC10454166 DOI: 10.3390/ijms241612851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 08/11/2023] [Accepted: 08/13/2023] [Indexed: 08/27/2023] Open
Abstract
Proteins fated to be internalized by clathrin-mediated endocytosis require an endocytic motif, where AP-2 or another adaptor protein can bind and recruit clathrin. Tyrosine and di-leucine-based sorting signals are such canonical motifs. Connexin 43 (Cx43) has three canonical tyrosine-based endocytic motifs, two of which have been previously shown to recruit clathrin and mediate its endocytosis. In addition, di-leucine-based motifs have been characterized in the Cx32 C-terminal domain and shown to mediate its endocytosis. Here, we examined the amino acid sequences of all 21 human connexins to identify endocytic motifs across the connexin gene family. We find that although there is limited conservation of endocytic motifs between connexins, 14 of the 21 human connexins contain one or more canonical tyrosine or di-leucine-based endocytic motif in their C-terminal or intracellular loop domain. Three connexins contain non-canonical (modified) di-leucine motifs. However, four connexins (Cx25, Cx26, Cx31, and Cx40.1) do not harbor any recognizable endocytic motif. Interestingly, live cell time-lapse imaging of different GFP-tagged connexins that either contain or do not contain recognizable endocytic motifs readily undergo endocytosis, forming clearly identifiable annular gap junctions when expressed in HeLa cells. How connexins without defined endocytic motifs are endocytosed is currently not known. Our results demonstrate that an array of endocytic motifs exists in the connexin gene family. Further analysis will establish whether the sites we identified in this in silico analysis are legitimate endocytic motifs.
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Affiliation(s)
| | - Matthias M. Falk
- Department of Biological Sciences, Lehigh University, 111 Research Drive, Bethlehem, PA 18015, USA
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Henke W, Kalamvoki M, Stephens EB. The Role of the Tyrosine-Based Sorting Signals of the ORF3a Protein of SARS-CoV-2 on Intracellular Trafficking, Autophagy, and Apoptosis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.24.550379. [PMID: 37547007 PMCID: PMC10402054 DOI: 10.1101/2023.07.24.550379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
The open reading frame 3a (ORF3a) is an accessory transmembrane protein that is important to the pathogenicity of SARS-CoV-2. The cytoplasmic domain of ORF3a has three canonical tyrosine-based sorting signals (YxxΦ; where x is any amino acid and Φ is a hydrophobic amino acid with a bulky -R group). They have been implicated in the trafficking of membrane proteins to the cell plasma membrane and to intracellular organelles. Previous studies have indicated that mutation of the 160YSNV163 motif abrogated plasma membrane expression and inhibited ORF3a-induced apoptosis. However, two additional canonical tyrosine-based sorting motifs (211YYQL213, 233YNKI236) exist in the cytoplasmic domain of ORF3a that have not been assessed. We removed all three potential tyrosine-based motifs and systematically restored them to assess the importance of each motif or combination of motifs that restored efficient trafficking to the cell surface and lysosomes. Our results indicate that the YxxΦ motif at position 160 was insufficient for the trafficking of ORF3a to the cell surface. Our studies also showed that ORF3a proteins with an intact YxxΦ at position 211 or at 160 and 211 were most important. We found that ORF3a cell surface expression correlated with the co-localization of ORF3a with LAMP-1 near the cell surface. These results suggest that YxxΦ motifs within the cytoplasmic domain may act cooperatively in ORF3a transport to the plasma membrane and endocytosis to lysosomes. Further, our results indicate that certain tyrosine mutants failed to activate caspase 3 and did not correlate with autophagy functions associated with this protein.
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Affiliation(s)
- Wyatt Henke
- Department of Microbiology, Molecular Genetics, and Immunology, 2000 Hixon Hall, University of Kansas Medical Center, 3901 Rainbow Blvd., Kansas City, Kansas 66160
| | - Maria Kalamvoki
- Department of Microbiology, Molecular Genetics, and Immunology, 2000 Hixon Hall, University of Kansas Medical Center, 3901 Rainbow Blvd., Kansas City, Kansas 66160
| | - Edward B Stephens
- Department of Microbiology, Molecular Genetics, and Immunology, 2000 Hixon Hall, University of Kansas Medical Center, 3901 Rainbow Blvd., Kansas City, Kansas 66160
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Xuan Z, Yang S, Clark B, Hill SE, Manning L, Colón-Ramos DA. The active zone protein Clarinet regulates synaptic sorting of ATG-9 and presynaptic autophagy. PLoS Biol 2023; 21:e3002030. [PMID: 37053235 PMCID: PMC10101500 DOI: 10.1371/journal.pbio.3002030] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 02/08/2023] [Indexed: 04/14/2023] Open
Abstract
Autophagy is essential for cellular homeostasis and function. In neurons, autophagosome biogenesis is temporally and spatially regulated to occur near presynaptic sites, in part via the trafficking of autophagy transmembrane protein ATG-9. The molecules that regulate autophagy by sorting ATG-9 at synapses remain largely unknown. Here, we conduct forward genetic screens at single synapses of C. elegans neurons and identify a role for the long isoform of the active zone protein Clarinet (CLA-1L) in regulating sorting of autophagy protein ATG-9 at synapses, and presynaptic autophagy. We determine that disrupting CLA-1L results in abnormal accumulation of ATG-9 containing vesicles enriched with clathrin. The ATG-9 phenotype in cla-1(L) mutants is not observed for other synaptic vesicle proteins, suggesting distinct mechanisms that regulate sorting of ATG-9-containing vesicles and synaptic vesicles. Through genetic analyses, we uncover the adaptor protein complexes that genetically interact with CLA-1 in ATG-9 sorting. We also determine that CLA-1L extends from the active zone to the periactive zone and genetically interacts with periactive zone proteins in ATG-9 sorting. Our findings reveal novel roles for active zone proteins in the sorting of ATG-9 and in presynaptic autophagy.
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Affiliation(s)
- Zhao Xuan
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and Cell Biology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Sisi Yang
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and Cell Biology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Benjamin Clark
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and Cell Biology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Sarah E. Hill
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and Cell Biology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Laura Manning
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and Cell Biology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Daniel A. Colón-Ramos
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and Cell Biology, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Instituto de Neurobiología, Recinto de Ciencias Médicas, Universidad de Puerto Rico, San Juan,Puerto Rico
- Wu Tsai Institute, Yale University, New Haven, Connecticut, United States of America
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Mani I, Singh V. An overview of receptor endocytosis and signaling. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2023; 194:1-18. [PMID: 36631188 DOI: 10.1016/bs.pmbts.2022.06.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Endocytosis is a cellular process which mediates receptor internalization, nutrient uptake, and the regulation of cell signaling. Microorganisms (many bacteria and viruses) and toxins also use the same process and enter the cells. Generally, endocytosis is considered in the three forms such as phagocytosis (cell eating), pinocytosis (cell drinking), and highly selective receptor-mediated endocytosis (clathrin-dependent and independent). Several endocytic routes exist in an analogous, achieving diverse functions. Most studies on endocytosis have used transformed cells in culture. To visualize the receptor internalization, trafficking, and signaling in subcellular organelles, a green fluorescent protein-tagged receptor has been utilized. It also helps to visualize the endocytosis effects in live-cell imaging. Confocal laser microscopy increases our understanding of receptor endocytosis and signaling. Site-directed mutagenesis studies demonstrated that many short-sequence motifs of the cytoplasmic domain of receptors significantly play a vital role in receptor internalization, subcellular trafficking, and signaling. However, other factors also regulate receptor internalization through clathrin-coated vesicles. Receptor endocytosis can occur through clathrin-dependent and clathrin-independent pathways. This chapter briefly discusses the internalization, trafficking, and signaling of various receptors in normal conditions. In addition, it also highlights the malfunction of the receptor in disease conditions.
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Affiliation(s)
- Indra Mani
- Department of Microbiology, Gargi College, University of Delhi, New Delhi, India.
| | - Vijai Singh
- Department of Biosciences, School of Science, Indrashil University, Rajpur, Mehsana, Gujarat, India
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Ragini, Sakshi, Saini A, Mani I. Endocytosis and signaling of 5-HT1A receptor. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2023; 196:113-123. [PMID: 36813354 DOI: 10.1016/bs.pmbts.2022.11.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The neurotransmitter serotonin (also known as 5-hydroxytryptamine, 5-HT) regulates many important physiological as well as pathological functions in the body like psychoemotional, sensation, blood circulation, food intake, autonomic, memory, sleep, pain, etc. 5-HT binds to its receptor 5-HT1A to initiate GTP exchange at the Gi/o protein, which activates the receptor G protein complex. G protein subunits attach to different effectors and generate various responses, such as inhibition of adenyl cyclase enzyme and regulates the opening of Ca++ and K+ ion channels. Activated signalling cascades activate protein kinase C (PKC) (a second messenger), which further induces the detachment of Gβγ-dependent receptor signaling and leads to 5-HT1A internalization. After internalization, 5-HT1A receptor attaches to the Ras-ERK1/2 pathway. The receptor further trafficks to the lysosome for degradation. Receptor skips the trafficking to the lysosomal compartments and undergoes dephosphorylation. Dephosphorylated receptors now recycled back to the cell membrane. In this chapter, we have discussed the internalization, trafficking and signaling of the 5-HT1A receptor.
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Affiliation(s)
- Ragini
- Department of Biotechnology, Regional Centre for Biotechnology, Faridabad, Haryana, India
| | - Sakshi
- Department of Biotechnology, Regional Centre for Biotechnology, Faridabad, Haryana, India
| | - Ashok Saini
- Department of Microbiology, Institute of Home Economics, University of Delhi, New Delhi, India
| | - Indra Mani
- Department of Microbiology, Gargi College, University of Delhi, New Delhi, India.
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Sharma P, Sharma BS, Raval H, Singh V. Endocytosis of GABA receptor: Signaling in nervous system. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2023; 196:125-139. [PMID: 36813355 DOI: 10.1016/bs.pmbts.2022.06.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
GABA (ᵞ-aminobutyric acid), is the principal neurotransmitter known for its inhibitory role in chemical synapses. Being localized primarily in the central nervous system (CNS) it maintains a balance between excitatory (regulated by another neurotransmitter, glutamate) and inhibitory impulses. GABA acts by binding to their specific receptors GABAA and GABAB when released into the post-synaptic nerve terminal. Both of these receptors are responsible for fast and slow inhibition of neurotransmission, respectively. GABAA is a ligand-gated ionopore receptor which opens the Cl- ion channel and decreases the resting potential of the membrane resulting into inhibition of the synapse. On the other hand, GABAB is a metabotropic receptor which increases the K+ ion levels preventing Ca+ ion release inhibiting the release of other neurotransmitters into the presynaptic membrane. The internalization and trafficking of these receptors is also conducted through distinct pathways and mechanism, discussed in detail in the chapter. Without the desired levels of GABA in the body, the psychological and neurological states of brain get hard to maintain. Various neurodegenerative diseases/disorders have been associated to low levels of GABA, such as anxiety, mood disorders, fear, schizophrenia, hungtington's chorea, seizures, epilepsy, etc. The allosteric sites present on GABA receptors have been proved to be potent drug targets to pacify the pathological states of these brain related disorders to an extent. Further in depth studies focussing on the subtypes of GABA receptors and their comprehensive mechanism are required to explore new drug targets and therapeutic avenues for effectual management of GABA related neurological diseases.
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Affiliation(s)
- Preeti Sharma
- Shree Vipratech Diagnostics, Dehgam, Gujarat, India.
| | - B Sharan Sharma
- Rivaara Labs, KD Hospital, Vaishnodevi Circle, Ahmedabad, Gujarat, India
| | - Hardik Raval
- Shree Vipratech Diagnostics, Dehgam, Gujarat, India
| | - Vijai Singh
- Department of Biosciences, School of Science, Indrashil University, Rajpur, Mehsana, Gujarat, India
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The LDL receptor: Traffic and function in trophoblast cells under normal and pathological conditions. Placenta 2022; 127:12-19. [DOI: 10.1016/j.placenta.2022.07.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 07/11/2022] [Accepted: 07/15/2022] [Indexed: 12/18/2022]
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Ganapathy AS, Saha K, Suchanec E, Singh V, Verma A, Yochum G, Koltun W, Nighot M, Ma T, Nighot P. AP2M1 mediates autophagy-induced CLDN2 (claudin 2) degradation through endocytosis and interaction with LC3 and reduces intestinal epithelial tight junction permeability. Autophagy 2022; 18:2086-2103. [PMID: 34964704 PMCID: PMC9466623 DOI: 10.1080/15548627.2021.2016233] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The intestinal epithelial tight junctions (TJs) provide barrier against paracellular permeation of lumenal antigens. Defects in TJ barrier such as increased levels of pore-forming TJ protein CLDN2 (claudin-2) is associated with inflammatory bowel disease. We have previously reported that starvation-induced macroautophagy/autophagy enhances the TJ barrier by degrading pore-forming CLDN2. In this study, we examined the molecular mechanism underlying autophagy-induced CLDN2 degradation. CLDN2 degradation was persistent in multiple modes of autophagy induction. Immunolocalization, membrane fractionation, and pharmacological inhibition studies showed increased clathrin-mediated CLDN2 endocytosis upon starvation. Inhibition of clathrin-mediated endocytosis negated autophagy-induced CLDN2 degradation and enhancement of the TJ barrier. The co-immunoprecipitation studies showed increased association of CLDN2 with clathrin and adaptor protein AP2 (AP2A1 and AP2M1 subunits) as well as LC3 and lysosomes upon starvation, signifying the role of clathrin-mediated endocytosis in autophagy-induced CLDN2 degradation. The expression and phosphorylation of AP2M1 was increased upon starvation. In-vitro, in-vivo (mouse colon), and ex-vivo (human colon) inhibition of AP2M1 activation prevented CLDN2 degradation. AP2M1 knockout prevented autophagy-induced CLDN2 degradation via reduced CLDN2-LC3 interaction. Site-directed mutagenesis revealed that AP2M1 binds to CLDN2 tyrosine motifs (YXXФ) (67-70 and 148-151). Increased baseline expression of CLDN2 and TJ permeability along with reduced CLDN2-AP2M1-LC3 interactions in ATG7 knockout cells validated the role of autophagy in modulation of CLDN2 levels. Acute deletion of Atg7 in mice increased CLDN2 levels and the susceptibility to experimental colitis. The autophagy-regulated molecular mechanisms linking CLDN2, AP2M1, and LC3 may provide therapeutic tools against intestinal inflammation.Abbreviations: Amil: amiloride; AP2: adaptor protein complex 2; AP2A1: adaptor related protein complex 2 subunit alpha 1; AP2M1: adaptor related protein complex 2 subunit mu 1; ATG7: autophagy related 7; CAL: calcitriol; Cas9: CRISPR-associated protein 9; Con: control; CPZ: chlorpromazine; DSS: dextran sodium sulfate; EBSS: Earle's balanced salt solution; IBD: inflammatory bowel disease; TER: trans-epithelial resistance; KD: knockdown; KO: knockout; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MβCD: Methyl-β-cyclodextrin; MET: metformin; MG132: carbobenzoxy-Leu-Leu-leucinal; MTOR: mechanistic target of rapamycin kinase; NT: non target; RAPA: rapamycin; RES: resveratrol; SMER: small-molecule enhancer 28; SQSTM1: sequestosome 1; ST: starvation; ULK1: unc-51 like autophagy activating kinase 1; WT: wild type.
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Affiliation(s)
| | - Kushal Saha
- Division of Gastroenterology and Hepatology, Department of Medicine, Pennsylvania State College of Medicine, Hershey, PA, USA
| | - Eric Suchanec
- Division of Gastroenterology and Hepatology, Department of Medicine, Pennsylvania State College of Medicine, Hershey, PA, USA
| | - Vikash Singh
- Division of Hematology and Oncology, Department of Pediatrics, Pennsylvania State College of Medicine, Hershey, Pa, USA
| | - Aayush Verma
- Division of Gastroenterology and Hepatology, Department of Medicine, Pennsylvania State College of Medicine, Hershey, PA, USA
| | - Gregory Yochum
- Division of Colon and Rectal Surgery, Department of Surgery, Pennsylvania State College of Medicine, Hershey, PA, USA
| | - Walter Koltun
- Division of Colon and Rectal Surgery, Department of Surgery, Pennsylvania State College of Medicine, Hershey, PA, USA
| | - Meghali Nighot
- Division of Gastroenterology and Hepatology, Department of Medicine, Pennsylvania State College of Medicine, Hershey, PA, USA
| | - Thomas Ma
- Division of Gastroenterology and Hepatology, Department of Medicine, Pennsylvania State College of Medicine, Hershey, PA, USA
| | - Prashant Nighot
- Division of Gastroenterology and Hepatology, Department of Medicine, Pennsylvania State College of Medicine, Hershey, PA, USA,CONTACT Prashant Nighot Department of Medicine, College of Medicine, Penn State University, Hershey, PA17033, USA
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11
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Endocytosis in the axon initial segment maintains neuronal polarity. Nature 2022; 609:128-135. [PMID: 35978188 PMCID: PMC9433327 DOI: 10.1038/s41586-022-05074-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 07/05/2022] [Indexed: 11/09/2022]
Abstract
Neurons are highly polarized cells that face the fundamental challenge of compartmentalizing a vast and diverse repertoire of proteins in order to function properly1. The axon initial segment (AIS) is a specialized domain that separates a neuron’s morphologically, biochemically and functionally distinct axon and dendrite compartments2,3. How the AIS maintains polarity between these compartments is not fully understood. Here we find that in Caenorhabditis elegans, mouse, rat and human neurons, dendritically and axonally polarized transmembrane proteins are recognized by endocytic machinery in the AIS, robustly endocytosed and targeted to late endosomes for degradation. Forcing receptor interaction with the AIS master organizer, ankyrinG, antagonizes receptor endocytosis in the AIS, causes receptor accumulation in the AIS, and leads to polarity deficits with subsequent morphological and behavioural defects. Therefore, endocytic removal of polarized receptors that diffuse into the AIS serves as a membrane-clearance mechanism that is likely to work in conjunction with the known AIS diffusion-barrier mechanism to maintain neuronal polarity on the plasma membrane. Our results reveal a conserved endocytic clearance mechanism in the AIS to maintain neuronal polarity by reinforcing axonal and dendritic compartment membrane boundaries. Endocytosis and degradation of plasma membrane proteins in the axon initial segment, together with the diffusion-barrier mechanism, maintain a polarized distribution of plasma membrane proteins in Caenorhabditis elegans, mouse, rat and human neurons.
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12
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Matsuoka H, Harada K, Sugawara A, Kim D, Inoue M. Expression of p11 and heteromeric TASK channels in mouse adrenal cortical cells and H295R cells. Acta Histochem 2022; 124:151898. [PMID: 35526370 DOI: 10.1016/j.acthis.2022.151898] [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: 03/07/2022] [Revised: 04/21/2022] [Accepted: 04/21/2022] [Indexed: 11/30/2022]
Abstract
TWIK-related acid-sensitive K+ (TASK) channels are thought to contribute to the resting membrane potential in adrenal cortical (AC) cells. However, the molecular identity of TASK channels in AC cells have not yet been elucidated. Thus, immunocytochemical and molecular biological approaches were employed to investigate the expression and intracellular distribution of TASK1 and TASK3 in mouse AC cells and H295R cells derived from human adrenocortical carcinoma. Immunocytochemical study revealed that immunoreactive materials were mainly located in the cytoplasm for TASK1 and at the cell periphery for TASK3 in mouse AC cells. A similar pattern of localization was observed when GFP-TASK1 and GFP-TASK3 were exogenously expressed in H295R cells. In addition, p11 that is known to suppress the endoplasmic reticulum exit of TASK1 was localized in the cytoplasm in mouse AC and H295R cells, but not in adrenal medullary cells. Proximity ligation assay (PLA) suggested formation of heteromeric TASK1-3 channels that were found predominantly in the cytoplasm and weakly at the cell periphery. A similar distribution was observed following exogenous expression of tandem TASK1-3 channels in H295R cells. When stimulated by angiotensin II, however, tandem TASK1-3 channels were present mainly in the cytoplasm in all H295R cells. In contrast to that in H295R cells, tandem channels were exclusively located at the cell periphery in all non-stimulated and exclusively in the cytoplasm in stimulated PC12 cells, respectively. From these results, we conclude that TASK1 proteins are present mainly in the cytoplasm and minimally at the cell periphery as a heteromeric channel with TASK3, whereas the majority of TASK3 is at the cell periphery as homomeric and heteromeric channels.
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Affiliation(s)
- Hidetada Matsuoka
- Department of Cell and Systems Physiology, University of Occupational and Environmental Health School of Medicine, Kitakyushu 807-8555, Japan
| | - Keita Harada
- Department of Cell and Systems Physiology, University of Occupational and Environmental Health School of Medicine, Kitakyushu 807-8555, Japan
| | - Akira Sugawara
- Department of Molecular Endocrinology, Tohoku University Graduate School of Medical Science, Sendai 980-8575, Japan
| | - Donghee Kim
- Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL 60064-3095, USA
| | - Masumi Inoue
- Department of Cell and Systems Physiology, University of Occupational and Environmental Health School of Medicine, Kitakyushu 807-8555, Japan.
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13
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Endocytic trafficking of GAS6-AXL complexes is associated with sustained AKT activation. Cell Mol Life Sci 2022; 79:316. [PMID: 35622156 PMCID: PMC9135597 DOI: 10.1007/s00018-022-04312-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 03/27/2022] [Accepted: 04/15/2022] [Indexed: 11/18/2022]
Abstract
AXL, a TAM receptor tyrosine kinase (RTK), and its ligand growth arrest-specific 6 (GAS6) are implicated in cancer metastasis and drug resistance, and cellular entry of viruses. Given this, AXL is an attractive therapeutic target, and its inhibitors are being tested in cancer and COVID-19 clinical trials. Still, astonishingly little is known about intracellular mechanisms that control its function. Here, we characterized endocytosis of AXL, a process known to regulate intracellular functions of RTKs. Consistent with the notion that AXL is a primary receptor for GAS6, its depletion was sufficient to block GAS6 internalization. We discovered that upon receptor ligation, GAS6–AXL complexes were rapidly internalized via several endocytic pathways including both clathrin-mediated and clathrin-independent routes, among the latter the CLIC/GEEC pathway and macropinocytosis. The internalization of AXL was strictly dependent on its kinase activity. In comparison to other RTKs, AXL was endocytosed faster and the majority of the internalized receptor was not degraded but rather recycled via SNX1-positive endosomes. This trafficking pattern coincided with sustained AKT activation upon GAS6 stimulation. Specifically, reduced internalization of GAS6–AXL upon the CLIC/GEEC downregulation intensified, whereas impaired recycling due to depletion of SNX1 and SNX2 attenuated AKT signaling. Altogether, our data uncover the coupling between AXL endocytic trafficking and AKT signaling upon GAS6 stimulation. Moreover, our study provides a rationale for pharmacological inhibition of AXL in antiviral therapy as viruses utilize GAS6–AXL-triggered endocytosis to enter cells.
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14
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Duan D, Hanson M, Holland DO, Johnson ME. Integrating protein copy numbers with interaction networks to quantify stoichiometry in clathrin-mediated endocytosis. Sci Rep 2022; 12:5413. [PMID: 35354856 PMCID: PMC8967901 DOI: 10.1038/s41598-022-09259-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 03/21/2022] [Indexed: 11/25/2022] Open
Abstract
Proteins that drive processes like clathrin-mediated endocytosis (CME) are expressed at copy numbers within a cell and across cell types varying from hundreds (e.g. auxilin) to millions (e.g. clathrin). These variations contain important information about function, but without integration with the interaction network, they cannot capture how supply and demand for each protein depends on binding to shared and distinct partners. Here we construct the interface-resolved network of 82 proteins involved in CME and establish a metric, a stoichiometric balance ratio (SBR), that quantifies whether each protein in the network has an abundance that is sub- or super-stoichiometric dependent on the global competition for binding. We find that highly abundant proteins (like clathrin) are super-stoichiometric, but that not all super-stoichiometric proteins are highly abundant, across three cell populations (HeLa, fibroblast, and neuronal synaptosomes). Most strikingly, within all cells there is significant competition to bind shared sites on clathrin and the central AP-2 adaptor by other adaptor proteins, resulting in most being in excess supply. Our network and systematic analysis, including response to perturbations of network components, show how competition for shared binding sites results in functionally similar proteins having widely varying stoichiometries, due to variations in both abundance and their unique network of binding partners.
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Affiliation(s)
- Daisy Duan
- TC Jenkins Department of Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD, 21218, USA
| | - Meretta Hanson
- TC Jenkins Department of Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD, 21218, USA
| | | | - Margaret E Johnson
- TC Jenkins Department of Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD, 21218, USA.
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15
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Host-Adapted Gene Families Involved in Murine Cytomegalovirus Immune Evasion. Viruses 2022; 14:v14010128. [PMID: 35062332 PMCID: PMC8781790 DOI: 10.3390/v14010128] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 01/08/2022] [Accepted: 01/10/2022] [Indexed: 12/12/2022] Open
Abstract
Cytomegaloviruses (CMVs) are host species-specific and have adapted to their respective mammalian hosts during co-evolution. Host-adaptation is reflected by “private genes” that have specialized in mediating virus-host interplay and have no sequence homologs in other CMV species, although biological convergence has led to analogous protein functions. They are mostly organized in gene families evolved by gene duplications and subsequent mutations. The host immune response to infection, both the innate and the adaptive immune response, is a driver of viral evolution, resulting in the acquisition of viral immune evasion proteins encoded by private gene families. As the analysis of the medically relevant human cytomegalovirus by clinical investigation in the infected human host cannot make use of designed virus and host mutagenesis, the mouse model based on murine cytomegalovirus (mCMV) has become a versatile animal model to study basic principles of in vivo virus-host interplay. Focusing on the immune evasion of the adaptive immune response by CD8+ T cells, we review here what is known about proteins of two private gene families of mCMV, the m02 and the m145 families, specifically the role of m04, m06, and m152 in viral antigen presentation during acute and latent infection.
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16
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Proskura AL, Islamova MY, Vechkapova SO. Cross-Talk of the Glutamate and Leptin Receptor Pathways. Mol Biol 2021. [DOI: 10.1134/s0026893321020291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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17
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Sutherland CJ, Henrici RC, Artavanis-Tsakonas K. Artemisinin susceptibility in the malaria parasite Plasmodium falciparum: propellers, adaptor proteins and the need for cellular healing. FEMS Microbiol Rev 2021; 45:fuaa056. [PMID: 33095255 PMCID: PMC8100002 DOI: 10.1093/femsre/fuaa056] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 10/21/2020] [Indexed: 12/12/2022] Open
Abstract
Studies of the susceptibility of Plasmodium falciparum to the artemisinin family of antimalarial drugs provide a complex picture of partial resistance (tolerance) associated with increased parasite survival in vitro and in vivo. We present an overview of the genetic loci that, in mutant form, can independently elicit parasite tolerance. These encode Kelch propeller domain protein PfK13, ubiquitin hydrolase UBP-1, actin filament-organising protein Coronin, also carrying a propeller domain, and the trafficking adaptor subunit AP-2μ. Detailed studies of these proteins and the functional basis of artemisinin tolerance in blood-stage parasites are enabling a new synthesis of our understanding to date. To guide further experimental work, we present two major conclusions. First, we propose a dual-component model of artemisinin tolerance in P. falciparum comprising suppression of artemisinin activation in early ring stage by reducing endocytic haemoglobin capture from host cytosol, coupled with enhancement of cellular healing mechanisms in surviving cells. Second, these two independent requirements limit the likelihood of development of complete artemisinin resistance by P. falciparum, favouring deployment of existing drugs in new schedules designed to exploit these biological limits, thus extending the useful life of current combination therapies.
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Affiliation(s)
- Colin J Sutherland
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel St, London WC1E 7HT, UK
| | - Ryan C Henrici
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel St, London WC1E 7HT, UK
- Center for Global Health, Perelman School of Medicine, University of Pennsylvania, Philadelphia 19104, PA, USA
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18
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Dissecting the structural features of β-arrestins as multifunctional proteins. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2021; 1869:140603. [PMID: 33421644 DOI: 10.1016/j.bbapap.2021.140603] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 12/21/2020] [Accepted: 01/04/2021] [Indexed: 02/08/2023]
Abstract
β-arrestins bind active G protein-coupled receptors (GPCRs) and play a crucial role in receptor desensitization and internalization. The classical paradigm of arrestin function has been expanded with the identification of many non-receptor-binding partners, which indicated the multifunctional role of β-arrestins in cellular functions. To elucidate the molecular mechanism of β-arrestin-mediated signaling, the structural features of β-arrestins were investigated using X-ray crystallography and cryogenic electron microscopy (cryo-EM). However, the intrinsic conformational flexibility of β-arrestins hampers the elucidation of structural interactions between β-arrestins and their binding partners using conventional structure determination tools. Therefore, structural information obtained using complementary structure analysis techniques would be necessary in combination with X-ray crystallography and cryo-EM data. In this review, we describe how β-arrestins interact with their binding partners from a structural point of view, as elucidated by both traditional methods (X-ray crystallography and cryo-EM) and complementary structure analysis techniques.
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19
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Giangreco G, Malabarba MG, Sigismund S. Specialised endocytic proteins regulate diverse internalisation mechanisms and signalling outputs in physiology and cancer. Biol Cell 2020; 113:165-182. [PMID: 33617023 DOI: 10.1111/boc.202000129] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 11/26/2020] [Accepted: 11/27/2020] [Indexed: 12/20/2022]
Abstract
Although endocytosis was first described as the process mediating macromolecule or nutrient uptake through the plasma membrane, it is now recognised as a critical component of the cellular infrastructure involved in numerous processes, ranging from receptor signalling, proliferation and migration to polarity and stem cell regulation. To realise these varying roles, endocytosis needs to be finely regulated. Accordingly, multiple endocytic mechanisms exist that require specialised molecular machineries and an array of endocytic adaptor proteins with cell-specific functions. This review provides some examples of specialised functions of endocytic adaptors and other components of the endocytic machinery in different cell physiological processes, and how the alteration of these functions is linked to cancer. In particular, we focus on: (i) cargo selection and endocytic mechanisms linked to different adaptors; (ii) specialised functions in clathrin-mediated versus non-clathrin endocytosis; (iii) differential regulation of endocytic mechanisms by post-translational modification of endocytic proteins; (iv) cell context-dependent expression and function of endocytic proteins. As cases in point, we describe two endocytic protein families, dynamins and epsins. Finally, we discuss how dysregulation of the physiological role of these specialised endocytic proteins is exploited by cancer cells to increase cell proliferation, migration and invasion, leading to anti-apoptotic or pro-metastatic behaviours.
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Affiliation(s)
| | - Maria Grazia Malabarba
- IEO, Istituto Europeo di Oncologia IRCCS, Milan, Italy.,Università degli Studi di Milano, Dipartimento di Oncologia ed Emato-oncologia, , Milan, Italy
| | - Sara Sigismund
- IEO, Istituto Europeo di Oncologia IRCCS, Milan, Italy.,Università degli Studi di Milano, Dipartimento di Oncologia ed Emato-oncologia, , Milan, Italy
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20
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Tobys D, Kowalski LM, Cziudaj E, Müller S, Zentis P, Pach E, Zigrino P, Blaeske T, Höning S. Inhibition of clathrin-mediated endocytosis by knockdown of AP-2 leads to alterations in the plasma membrane proteome. Traffic 2020; 22:6-22. [PMID: 33225555 DOI: 10.1111/tra.12770] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 11/19/2020] [Accepted: 11/19/2020] [Indexed: 01/05/2023]
Abstract
In eukaryotic cells, clathrin-mediated endocytosis (CME) is a central pathway for the internalization of proteins from the cell surface, thereby contributing to the maintenance of the plasma membrane protein composition. A key component for the formation of endocytic clathrin-coated vesicles (CCVs) is AP-2, as it sequesters cargo membrane proteins, recruits a multitude of other endocytic factors and initiates clathrin polymerization. Here, we inhibited CME by depletion of AP-2 and explored the consequences for the plasma membrane proteome. Quantitative analysis revealed accumulation of major constituents of the endosomal-lysosomal system reflecting a block in retrieval by compensatory CME. The noticeable enrichment of integrins and blockage of their turnover resulted in severely impaired cell migration. Rare proteins such as the anti-cancer drug target CA9 and tumor markers (CD73, CD164, CD302) were significantly enriched. The AP-2 knockdown attenuated the global endocytic capacity, but clathrin-independent entry pathways were still operating, as indicated by persistent internalization of specific membrane-spanning and GPI-anchored receptors (PVR, IGF1R, CD55, TNAP). We hypothesize that blocking AP-2 function and thus inhibiting CME may be a novel approach to identify new druggable targets, or to increase their residence time at the plasma membrane, thereby increasing the probability for efficient therapeutic intervention.
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Affiliation(s)
- David Tobys
- Institute for Biochemistry, Medical Faculty, University of Cologne, Cologne, Germany
| | - Lisa Maria Kowalski
- Institute for Biochemistry, Medical Faculty, University of Cologne, Cologne, Germany
| | - Eva Cziudaj
- Institute for Biochemistry, Medical Faculty, University of Cologne, Cologne, Germany
| | - Stefan Müller
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
| | - Peter Zentis
- CECAD Cluster of Excellence, University of Cologne, Cologne, Germany
| | - Elke Pach
- Department of Dermatology, Medical Faculty, University of Cologne, Cologne, Germany
| | - Paola Zigrino
- Department of Dermatology, Medical Faculty, University of Cologne, Cologne, Germany
| | - Tobias Blaeske
- Department of Plant Physiology and Biochemistry, University of Constance, Constance, Germany
| | - Stefan Höning
- Institute for Biochemistry, Medical Faculty, University of Cologne, Cologne, Germany
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21
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Cui K, Dong Y, Wang B, Cowan DB, Chan SL, Shyy J, Chen H. Endocytic Adaptors in Cardiovascular Disease. Front Cell Dev Biol 2020; 8:624159. [PMID: 33363178 PMCID: PMC7759532 DOI: 10.3389/fcell.2020.624159] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 11/23/2020] [Indexed: 12/11/2022] Open
Abstract
Endocytosis is the process of actively transporting materials into a cell by membrane engulfment. Traditionally, endocytosis was divided into three forms: phagocytosis (cell eating), pinocytosis (cell drinking), and the more selective receptor-mediated endocytosis (clathrin-mediated endocytosis); however, other important endocytic pathways (e.g., caveolin-dependent endocytosis) contribute to the uptake of extracellular substances. In each, the plasma membrane changes shape to allow the ingestion and internalization of materials, resulting in the formation of an intracellular vesicle. While receptor-mediated endocytosis remains the best understood pathway, mammalian cells utilize each form of endocytosis to respond to their environment. Receptor-mediated endocytosis permits the internalization of cell surface receptors and their ligands through a complex membrane invagination process that is facilitated by clathrin and adaptor proteins. Internalized vesicles containing these receptor-ligand cargoes fuse with early endosomes, which can then be recycled back to the plasma membrane, delivered to other cellular compartments, or destined for degradation by fusing with lysosomes. These intracellular fates are largely determined by the interaction of specific cargoes with adaptor proteins, such as the epsins, disabled-homolog 2 (Dab2), the stonin proteins, epidermal growth factor receptor substrate 15, and adaptor protein 2 (AP-2). In this review, we focus on the role of epsins and Dab2 in controlling these sorting processes in the context of cardiovascular disease. In particular, we will focus on the function of epsins and Dab2 in inflammation, cholesterol metabolism, and their fundamental contribution to atherogenicity.
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Affiliation(s)
- Kui Cui
- Vascular Biology Program, Boston Children's Hospital, Boston, MA, United States.,Department of Surgery, Harvard Medical School, Boston, MA, United States
| | - Yunzhou Dong
- Vascular Biology Program, Boston Children's Hospital, Boston, MA, United States.,Department of Surgery, Harvard Medical School, Boston, MA, United States
| | - Beibei Wang
- Vascular Biology Program, Boston Children's Hospital, Boston, MA, United States.,Department of Surgery, Harvard Medical School, Boston, MA, United States
| | - Douglas B Cowan
- Vascular Biology Program, Boston Children's Hospital, Boston, MA, United States.,Department of Surgery, Harvard Medical School, Boston, MA, United States.,Department of Cardiology, Boston Children's Hospital, Boston, MA, United States
| | - Siu-Lung Chan
- Vascular Biology Program, Boston Children's Hospital, Boston, MA, United States.,Department of Surgery, Harvard Medical School, Boston, MA, United States
| | - John Shyy
- Division of Cardiology, Department of Medicine, University of California, San Diego, San Diego, CA, United States
| | - Hong Chen
- Vascular Biology Program, Boston Children's Hospital, Boston, MA, United States.,Department of Surgery, Harvard Medical School, Boston, MA, United States
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22
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Kell MJ, Ang SF, Pigati L, Halpern A, Fölsch H. Novel function for AP-1B during cell migration. Mol Biol Cell 2020; 31:2475-2493. [PMID: 32816642 PMCID: PMC7851849 DOI: 10.1091/mbc.e20-04-0256] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The epithelial cell-specific clathrin adaptor protein (AP)-1B has a well-established role in polarized sorting of cargos to the basolateral membrane. Here we show that β1 integrin was dependent on AP-1B and its coadaptor, autosomal recessive hypercholesterolemia protein (ARH), for sorting to the basolateral membrane. We further demonstrate an unprecedented role for AP-1B at the basal plasma membrane during collective cell migration of epithelial sheets. During wound healing, expression of AP-1B (and ARH in AP–1B-positive cells) slowed epithelial-cell migration. We show that AP-1B colocalized with β1 integrin in focal adhesions during cell migration using confocal microscopy and total internal reflection fluorescence microscopy on fixed specimens. Further, AP-1B labeling in cell protrusions was distinct from labeling for the endocytic adaptor complex AP-2. Using stochastic optical reconstruction microscopy we identified numerous AP–1B-coated structures at or close to the basal plasma membrane in cell protrusions. In addition, immunoelectron microscopy showed AP-1B in coated pits and vesicles at the plasma membrane during cell migration. Lastly, quantitative real-time reverse transcription PCR analysis of human epithelial-derived cell lines revealed a loss of AP-1B expression in highly migratory metastatic cancer cells suggesting that AP-1B’s novel role at the basal plasma membrane during cell migration might be an anticancer mechanism.
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Affiliation(s)
- Margaret Johnson Kell
- Department of Cell and Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | - Su Fen Ang
- Department of Cell and Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | - Lucy Pigati
- Department of Cell and Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | - Abby Halpern
- Department of Cell and Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | - Heike Fölsch
- Department of Cell and Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
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23
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Moore R, Vogt K, Acosta-Martin AE, Shire P, Zeidler M, Smythe E. Integration of JAK/STAT receptor-ligand trafficking, signalling and gene expression in Drosophila melanogaster cells. J Cell Sci 2020; 133:jcs246199. [PMID: 32917740 DOI: 10.1242/jcs.246199] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 09/02/2020] [Indexed: 12/18/2022] Open
Abstract
The JAK/STAT pathway is an essential signalling cascade required for multiple processes during development and for adult homeostasis. A key question in understanding this pathway is how it is regulated in different cell contexts. Here, we have examined how endocytic processing contributes to signalling by the single cytokine receptor in Drosophila melanogaster cells, Domeless. We identify an evolutionarily conserved di-leucine (di-Leu) motif that is required for Domeless internalisation and show that endocytosis is required for activation of a subset of Domeless targets. Our data indicate that endocytosis both qualitatively and quantitatively regulates Domeless signalling. STAT92E, the single STAT transcription factor in Drosophila, appears to be the target of endocytic regulation, and our studies show that phosphorylation of STAT92E on Tyr704, although necessary, is not always sufficient for target transcription. Finally, we identify a conserved residue, Thr702, which is essential for Tyr704 phosphorylation. Taken together, our findings identify previously unknown aspects of JAK/STAT pathway regulation likely to play key roles in the spatial and temporal regulation of signalling in vivo.
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Affiliation(s)
- Rachel Moore
- Centre for Membrane Interactions and Dynamics, Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK
| | - Katja Vogt
- Centre for Membrane Interactions and Dynamics, Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK
| | - Adelina E Acosta-Martin
- biOMICS Facility, Faculty of Science Mass Spectrometry Centre, University of Sheffield, Sheffield S10 2TN, UK
| | - Patrick Shire
- Centre for Membrane Interactions and Dynamics, Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK
| | - Martin Zeidler
- Centre for Membrane Interactions and Dynamics, Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK
| | - Elizabeth Smythe
- Centre for Membrane Interactions and Dynamics, Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK
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24
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Negahdaripour M, Owji H, Eskandari S, Zamani M, Vakili B, Nezafat N. Small extracellular vesicles (sEVs): discovery, functions, applications, detection methods and various engineered forms. Expert Opin Biol Ther 2020; 21:371-394. [PMID: 32945228 DOI: 10.1080/14712598.2021.1825677] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
INTRODUCTION Extracellular vesicles (EVs) are cell-created delivery systems of proteins, lipids, or nucleic acids, and means of extracellular communication. Though sEVs were initially considered to be the waste disposal mechanism, today they are at the forefront of research with different biological and pathological functions. Such EVs play a key role in the immunoregulation, CNS development, nervous system physiology, mammary gland development, induction of immunosuppression in pregnancy, the developmental signaling pathways, regeneration of different tissues, inflammation, angiogenesis, coagulation, apoptosis, stem cell differentiation, and extracellular matrix turnover. AREAS COVERED SEVs contribute to the pathogenesis of different cancers and the progression of various neurodegenerative diseases, infections, as well as metabolic and cardiovascular diseases. Expert Opinion: There is no exact classification for EVs; however, according to size, density, morphological features, content, and biogenesis, they can be categorized into three major classes: microvesicles (ectosomes or microparticles), apoptotic bodies, and sEVs. SEVs, as an important class of EVs, have a crucial role in distinct biological functions. Moreover, shedding light on different structural and molecular aspects of sEV has led to their application in various therapeutic, diagnostic, and drug delivery fields. In this review, we have endeavored to elaborate on different aspects of EVs, especially sEVs.
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Affiliation(s)
- Manica Negahdaripour
- Department of Pharmaceutical Biotechnology, School of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Iran.,Pharmaceutical Sciences Research Center, Shiraz University of Medical Science, Shiraz, Iran
| | - Hajar Owji
- Pharmaceutical Sciences Research Center, Shiraz University of Medical Science, Shiraz, Iran
| | - Sedigheh Eskandari
- Pharmaceutical Sciences Research Center, Shiraz University of Medical Science, Shiraz, Iran
| | - Mozhdeh Zamani
- Colorectal Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Bahareh Vakili
- Pharmaceutical Sciences Research Center, Shiraz University of Medical Science, Shiraz, Iran
| | - Navid Nezafat
- Department of Pharmaceutical Biotechnology, School of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Iran.,Pharmaceutical Sciences Research Center, Shiraz University of Medical Science, Shiraz, Iran
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25
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Fischer K, Groschup MH, Diederich S. Importance of Endocytosis for the Biological Activity of Cedar Virus Fusion Protein. Cells 2020; 9:cells9092054. [PMID: 32911832 PMCID: PMC7565975 DOI: 10.3390/cells9092054] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 09/03/2020] [Accepted: 09/04/2020] [Indexed: 01/02/2023] Open
Abstract
Endocytosis plays a particular role in the proteolytic activation of highly pathogenic henipaviruses Hendra (HeV) and Nipah virus (NiV) fusion (F) protein precursors. These proteins require endocytic uptake from the cell surface to be cleaved by cellular proteases within the endosomal compartment, followed by recycling to the plasma membrane for incorporation into budding virions or mediation of cell-cell fusion. This internalization largely depends on a tyrosine-based consensus motif for endocytosis present in the cytoplasmic tail of HeV and NiV F. Given the large number of tyrosine residues present in the F protein cytoplasmic domain of Cedar virus (CedV), a closely related but low pathogenic henipavirus, we aimed to investigate whether CedV F protein undergoes signal-mediated endocytosis from the cell surface controlled by tyrosine-based motifs present in its cytoplasmic tail and whether endocytosis is relevant for its biological activity. Therefore, tyrosine-based signals were mutated, and mutations were assessed for their effect on F cell surface expression, endocytosis, and biological activity. A membrane-proximal YXXΦ motif and a C-terminal di-tyrosine motif are of particular importance for cell surface expression and endocytosis rate. Furthermore, our data strongly indicate the pivotal role of endocytosis for the biological activity of the CedV F protein.
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The Plasmodium falciparum Artemisinin Susceptibility-Associated AP-2 Adaptin μ Subunit is Clathrin Independent and Essential for Schizont Maturation. mBio 2020; 11:mBio.02918-19. [PMID: 32098816 PMCID: PMC7042695 DOI: 10.1128/mbio.02918-19] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The efficacy of current antimalarial drugs is threatened by reduced susceptibility of Plasmodium falciparum to artemisinin, associated with mutations in pfkelch13 Another gene with variants known to modulate the response to artemisinin encodes the μ subunit of the AP-2 adaptin trafficking complex. To elucidate the cellular role of AP-2μ in P. falciparum, we performed a conditional gene knockout, which severely disrupted schizont organization and maturation, leading to mislocalization of key merozoite proteins. AP-2μ is thus essential for blood-stage replication. We generated transgenic P. falciparum parasites expressing hemagglutinin-tagged AP-2μ and examined cellular localization by fluorescence and electron microscopy. Together with mass spectrometry analysis of coimmunoprecipitating proteins, these studies identified AP-2μ-interacting partners, including other AP-2 subunits, the K10 kelch-domain protein, and PfEHD, an effector of endocytosis and lipid mobilization, but no evidence was found of interaction with clathrin, the expected coat protein for AP-2 vesicles. In reverse immunoprecipitation experiments with a clathrin nanobody, other heterotetrameric AP-complexes were shown to interact with clathrin, but AP-2 complex subunits were absent.IMPORTANCE We examine in detail the AP-2 adaptin complex from the malaria parasite Plasmodium falciparum In most studied organisms, AP-2 is involved in bringing material into the cell from outside, a process called endocytosis. Previous work shows that changes to the μ subunit of AP-2 can contribute to drug resistance. Our experiments show that AP-2 is essential for parasite development in blood but does not have any role in clathrin-mediated endocytosis. This suggests that a specialized function for AP-2 has developed in malaria parasites, and this may be important for understanding its impact on drug resistance.
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Jadli AS, Ballasy N, Edalat P, Patel VB. Inside(sight) of tiny communicator: exosome biogenesis, secretion, and uptake. Mol Cell Biochem 2020; 467:77-94. [PMID: 32088833 DOI: 10.1007/s11010-020-03703-z] [Citation(s) in RCA: 137] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 02/14/2020] [Indexed: 01/07/2023]
Abstract
Discovered in the late 1980s as an extracellular vesicle of endosomal origin secreted from reticulocytes, exosomes recently gained scientific attention due to its role in intercellular communication. Exosomes have now been identified to carry cell-specific cargo of nucleic acids, proteins, lipids, and other biologically active molecules. Exosomes can be selectively taken up by neighboring or distant cells, which has shown to result in structural and functional responses in the recipient cells. Recent advances indicate the regulation of exosomes at various steps, including their biogenesis, selection of their cargo, as well as cell-specific uptake. This review will shed light on the differences between the type of extracellular vesicles. In this review, we discuss the recent progress in our understanding of the regulation of exosome biogenesis, secretion, and uptake.
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Affiliation(s)
- Anshul S Jadli
- Department of Physiology and Pharmacology, Cumming School of Medicine, The University of Calgary, HMRB-53, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada.,Libin Cardiovascular Institute of Alberta, The University of Calgary, HMRB-71, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada
| | - Noura Ballasy
- Department of Physiology and Pharmacology, Cumming School of Medicine, The University of Calgary, HMRB-53, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada.,Libin Cardiovascular Institute of Alberta, The University of Calgary, HMRB-71, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada
| | - Pariya Edalat
- Department of Physiology and Pharmacology, Cumming School of Medicine, The University of Calgary, HMRB-53, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada.,Libin Cardiovascular Institute of Alberta, The University of Calgary, HMRB-71, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada
| | - Vaibhav B Patel
- Department of Physiology and Pharmacology, Cumming School of Medicine, The University of Calgary, HMRB-53, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada. .,Libin Cardiovascular Institute of Alberta, The University of Calgary, HMRB-71, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada.
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Rópolo AS, Feliziani C, Touz MC. Unusual proteins in Giardia duodenalis and their role in survival. ADVANCES IN PARASITOLOGY 2019; 106:1-50. [PMID: 31630755 DOI: 10.1016/bs.apar.2019.07.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The capacity of the parasite Giardia duodenalis to perform complex functions with minimal amounts of proteins and organelles has attracted increasing numbers of scientists worldwide, trying to explain how this parasite adapts to internal and external changes to survive. One explanation could be that G. duodenalis evolved from a structurally complex ancestor by reductive evolution, resulting in adaptation to its parasitic lifestyle. Reductive evolution involves the loss of genes, organelles, and functions that commonly occur in many parasites, by which the host renders some structures and functions redundant. However, there is increasing data that Giardia possesses proteins able to perform more than one function. During recent decades, the concept of moonlighting was described for multitasking proteins, which involves only proteins with an extra independent function(s). In this chapter, we provide an overview of unusual proteins in Giardia that present multifunctional properties depending on the location and/or parasite requirement. We also discuss experimental evidence that may allow some giardial proteins to be classified as moonlighting proteins by examining the properties of moonlighting proteins in general. Up to date, Giardia does not seem to require the numerous redundant proteins present in other organisms to accomplish its normal functions, and thus this parasite may be an appropriate model for understanding different aspects of moonlighting proteins, which may be helpful in the design of drug targets.
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Affiliation(s)
- Andrea S Rópolo
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Constanza Feliziani
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
| | - María C Touz
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina.
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Hou X, Wu Q, Rajagopalan C, Zhang C, Bouhamdan M, Wei H, Chen X, Zaman K, Li C, Sun X, Chen S, Frizzell RA, Sun F. CK19 stabilizes CFTR at the cell surface by limiting its endocytic pathway degradation. FASEB J 2019; 33:12602-12615. [PMID: 31450978 DOI: 10.1096/fj.201901050r] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Protein interactions that stabilize the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) at the apical membranes of epithelial cells have not yet been fully elucidated. We identified keratin 19 (CK19 or K19) as a novel CFTR-interacting protein. CK19 overexpression stabilized both wild-type (WT)-CFTR and Lumacaftor (VX-809)-rescued F508del-CFTR (where F508del is the deletion of the phenylalanine residue at position 508) at the plasma membrane (PM), promoting Cl- secretion across human bronchial epithelial (HBE) cells. CK19 prevention of Rab7A-mediated lysosomal degradation was a key mechanism in apical CFTR stabilization. Unexpectedly, CK19 expression was decreased by ∼40% in primary HBE cells from homogenous F508del patients with CF relative to non-CF controls. CK19 also positively regulated multidrug resistance-associated protein 4 expression at the PM, suggesting that this keratin may regulate the apical expression of other ATP-binding cassette proteins as well as CFTR.-Hou, X., Wu, Q., Rajagopalan, C., Zhang, C., Bouhamdan, M., Wei, H., Chen, X., Zaman, K., Li, C., Sun, X., Chen, S., Frizzell, R. A., Sun, F. CK19 stabilizes CFTR at the cell surface by limiting its endocytic pathway degradation.
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Affiliation(s)
- Xia Hou
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, USA.,Department of Biochemistry and Molecular Biology, Jiamusi University School of Basic Medicine, Jiamusi, China
| | - Qingtian Wu
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, USA.,Department of Biochemistry and Molecular Biology, Jiamusi University School of Basic Medicine, Jiamusi, China
| | - Carthic Rajagopalan
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Chunbing Zhang
- Department of Biochemistry and Molecular Biology, Jiamusi University School of Basic Medicine, Jiamusi, China
| | - Mohamad Bouhamdan
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Hongguang Wei
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Xuequn Chen
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Khalequz Zaman
- Department of Pediatric Respiratory Medicine, University of Virginia School of Medicine, Charlottesville, Virginia, USA
| | - Chunying Li
- Center for Molecular and Translational Medicine, Georgia State University, Atlanta, Georgia, USA
| | - Xiaonan Sun
- Center for Molecular and Translational Medicine, Georgia State University, Atlanta, Georgia, USA
| | - Song Chen
- Institute of Medical Biotechnology, Jiangsu College of Nursing, Huai'an, China
| | - Raymond A Frizzell
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.,Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Fei Sun
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, USA
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Marcoux AA, Slimani S, Tremblay LE, Frenette-Cotton R, Garneau AP, Isenring P. Endocytic recycling of Na + -K + -Cl - cotransporter type 2: importance of exon 4. J Physiol 2019; 597:4263-4276. [PMID: 31216057 DOI: 10.1113/jp278024] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 06/05/2019] [Indexed: 01/29/2023] Open
Abstract
KEY POINTS Na+ -K+ -Cl- cotransporter type 2 (NKCC2) is a 27-exon membrane protein that is expressed in the thick ascending limb (TAL) of Henle where it is involved in reabsorption of the ultrafiltered NaCl load. It comes as three splice variants that are identical to each other except for the residue composition of exon 4 and that differ in their transport characteristics, functional roles and distributions along the TAL. In this report, it is shown that the variants also differ in their trafficking properties and that two residues in exon 4 play a key role in this regard. One of these residues was also shown to sustain carrier internalization. Through these results, a novel function for the alternatively spliced exon of NKCC2 has been identified and a domain that is involved in carrier trafficking has been uncovered for the first time in a cation-Cl- cotransporter family member. ABSTRACT Na+ -K+ -Cl- cotransporter type 2 (NKCC2) is a 12-transmembrane (TM) domain cell surface glycoprotein that is expressed in the thick ascending limb (TAL) of Henle and stimulated during cell shrinkage. It comes as three splice variants (A, B and F) that are identical to each other except for TM2 and the following connecting segment (CS2). Yet, these variants do not share the same localization, transport characteristics and physiological roles along the TAL. We have recently found that while cell shrinkage could exert its activating effect by increasing NKCC2 expression at the cell surface, the variants also responded differentially to this stimulus. In the current work, a mutagenic approach was exploited to determine whether CS2 could play a role in carrier trafficking and identify the residues potentially involved. We found that when the residue of position 238 in NKCC2A (F) and NKCC2B (Y) was replaced by the corresponding residue in NKCC2F (V), carrier activity increased by over 3-fold and endocytosis decreased concomitantly. We also found that when the residue of position 230 in NKCC2F (M) was replaced by the one in NKCC2B (T), carrier activity and affinity for ions both increased substantially whereas expression at the membrane decreased. Taken together, these results suggest that CS2 is involved in carrier trafficking and that two of its residues, those of positions 238 and 230, are part of an internalization motif. They also indicate that the divergent residue of position 230 plays the dual role of specifying ion affinity and sustaining carrier internalization.
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Affiliation(s)
- Andrée-Anne Marcoux
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University, Québec, QC, Canada, G1R 2J6
| | - Samira Slimani
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University, Québec, QC, Canada, G1R 2J6
| | - Laurence E Tremblay
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University, Québec, QC, Canada, G1R 2J6
| | - Rachelle Frenette-Cotton
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University, Québec, QC, Canada, G1R 2J6
| | - Alexandre P Garneau
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University, Québec, QC, Canada, G1R 2J6.,Cardiometabolic Research Group, Department of Kinesiology, Faculty of Medicine, University of Montréal, Montréal, QC, Canada, H3T 1J4
| | - Paul Isenring
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University, Québec, QC, Canada, G1R 2J6
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31
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Mani I, Pandey KN. Emerging concepts of receptor endocytosis and concurrent intracellular signaling: Mechanisms of guanylyl cyclase/natriuretic peptide receptor-A activation and trafficking. Cell Signal 2019; 60:17-30. [PMID: 30951863 DOI: 10.1016/j.cellsig.2019.03.022] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 03/27/2019] [Accepted: 03/28/2019] [Indexed: 12/15/2022]
Abstract
Endocytosis is a prominent clathrin-mediated mechanism for concentrated uptake and internalization of ligand-receptor complexes, also known as cargo. Internalization of cargo is the fundamental mechanism for receptor-dependent regulation of cell membrane function, intracellular signal transduction, and neurotransmission, as well as other biological and physiological activities. However, the intrinsic mechanisms of receptor endocytosis and contemporaneous intracellular signaling are not well understood. We review emerging concepts of receptor endocytosis with concurrent intracellular signaling, using a typical example of guanylyl cyclase/natriuretic peptide receptor-A (NPRA) internalization, subcellular trafficking, and simultaneous generation of second-messenger cGMP and signaling in intact cells. We highlight the role of short-signal motifs located in the carboxyl-terminal regions of membrane receptors during their internalization and subsequent receptor trafficking in organelles that are not traditionally studied in this context, including nuclei and mitochondria. This review sheds light on the importance of future investigations of receptor endocytosis and trafficking in live cells and intact animals in vivo in physiological context.
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Affiliation(s)
- Indra Mani
- Department of Physiology, Tulane University Health Sciences Center and School of Medicine, 1430 Tulane Avenue, New Orleans, Louisiana 70112, United States
| | - Kailash N Pandey
- Department of Physiology, Tulane University Health Sciences Center and School of Medicine, 1430 Tulane Avenue, New Orleans, Louisiana 70112, United States.
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32
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Murine Leukemia Virus Glycosylated Gag Reduces Murine SERINC5 Protein Expression at Steady-State Levels via the Endosome/Lysosome Pathway to Counteract SERINC5 Antiretroviral Activity. J Virol 2019; 93:JVI.01651-18. [PMID: 30355687 DOI: 10.1128/jvi.01651-18] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 10/17/2018] [Indexed: 11/20/2022] Open
Abstract
Glycosylated Gag (glycoGag) is an accessory protein expressed by most gammaretroviruses, including murine leukemia virus (MLV). MLV glycoGag not only enhances MLV replication and disease progression but also increases human immunodeficiency virus type 1 (HIV-1) infectivity as Nef does. Recently, SERINC5 (Ser5) was identified as the target for Nef, and the glycoGag Nef-like activity has been attributed to the Ser5 antagonism. Here, we investigated how glycoGag antagonizes Ser5 using MLV glycoMA and murine Ser5 proteins. We confirm previous observations that glycoMA relocalizes Ser5 from plasma membrane to perinuclear punctated compartments and the important role of its Y36XXL39 motif in this process. We find that glycoMA decreases Ser5 expression at steady-state levels and identify two other glycoGag crucial residues, P31 and R63, for the Ser5 downregulation. The glycoMA and Ser5 interaction is detected in live cells using a bimolecular fluorescence complementation assay. Ser5 is internalized via receptor-mediated endocytosis and relocalized to Rab5+ early, Rab7+ late, and Rab11+ recycling endosomes by glycoMA. Although glycoMA is not polyubiquitinated, the Ser5 downregulation requires Ser5 polyubiquitination via the K48- and K63-linkage, resulting in Ser5 destruction in lysosomes. Although P31, Y36, L39, and R63 are not required for glycoMA interaction with Ser5, they are required for Ser5 relocalization to lysosomes for destruction. In addition, although murine Ser1, Ser2, and Ser3 exhibit very poor antiviral activity, they are also targeted by glycoMA for lysosomal destruction. We conclude that glycoGag has a broad activity to downregulate SERINC proteins via the cellular endosome/lysosome pathway, which promotes viral replication.IMPORTANCE MLV glycoGag not only enhances MLV replication but also increases HIV-1 infectivity similarly as Nef. Recent studies have discovered that both glycoGag and Nef antagonize a novel host restriction factor Ser5 and promote viral replication. Compared to Nef, the glycoGag antagonism of Ser5 is still poorly understood. MLV glycoGag is a transmembrane version of the structural Gag protein with an extra 88-amino-acid leader region that determines its activity. We now show that glycoGag interacts with Ser5 in live cells and internalizes Ser5 via receptor-mediated endocytosis. Ser5 is polyubiquitinated and relocalized to endosomes and lysosomes for massive destruction. In addition to the previously identified tyrosine-based sorting signal, we find two more important residues for Ser5 relocalization and downregulation. We also find that the Ser5 sensitivity to glycoGag is conserved in the SERINC family. Together, our findings highlight the important role of endosome/lysosome pathway in the enhancement of viral replication by viral proteins.
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33
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Robinson M, Schor S, Barouch-Bentov R, Einav S. Viral journeys on the intracellular highways. Cell Mol Life Sci 2018; 75:3693-3714. [PMID: 30043139 PMCID: PMC6151136 DOI: 10.1007/s00018-018-2882-0] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 07/01/2018] [Accepted: 07/19/2018] [Indexed: 12/24/2022]
Abstract
Viruses are obligate intracellular pathogens that are dependent on cellular machineries for their replication. Recent technological breakthroughs have facilitated reliable identification of host factors required for viral infections and better characterization of the virus-host interplay. While these studies have revealed cellular machineries that are uniquely required by individual viruses, accumulating data also indicate the presence of broadly required mechanisms. Among these overlapping cellular functions are components of intracellular membrane trafficking pathways. Here, we review recent discoveries focused on how viruses exploit intracellular membrane trafficking pathways to promote various stages of their life cycle, with an emphasis on cellular factors that are usurped by a broad range of viruses. We describe broadly required components of the endocytic and secretory pathways, the Endosomal Sorting Complexes Required for Transport pathway, and the autophagy pathway. Identification of such overlapping host functions offers new opportunities to develop broad-spectrum host-targeted antiviral strategies.
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Affiliation(s)
- Makeda Robinson
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Lane Building, Rm L127, Stanford, CA, 94305, USA
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA
| | - Stanford Schor
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Lane Building, Rm L127, Stanford, CA, 94305, USA
| | - Rina Barouch-Bentov
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Lane Building, Rm L127, Stanford, CA, 94305, USA
| | - Shirit Einav
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Lane Building, Rm L127, Stanford, CA, 94305, USA.
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA.
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Zanoni P, Velagapudi S, Yalcinkaya M, Rohrer L, von Eckardstein A. Endocytosis of lipoproteins. Atherosclerosis 2018; 275:273-295. [PMID: 29980055 DOI: 10.1016/j.atherosclerosis.2018.06.881] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 06/04/2018] [Accepted: 06/22/2018] [Indexed: 02/06/2023]
Abstract
During their metabolism, all lipoproteins undergo endocytosis, either to be degraded intracellularly, for example in hepatocytes or macrophages, or to be re-secreted, for example in the course of transcytosis by endothelial cells. Moreover, there are several examples of internalized lipoproteins sequestered intracellularly, possibly to exert intracellular functions, for example the cytolysis of trypanosoma. Endocytosis and the subsequent intracellular itinerary of lipoproteins hence are key areas for understanding the regulation of plasma lipid levels as well as the biological functions of lipoproteins. Indeed, the identification of the low-density lipoprotein (LDL)-receptor and the unraveling of its transcriptional regulation led to the elucidation of familial hypercholesterolemia as well as to the development of statins, the most successful therapeutics for lowering of cholesterol levels and risk of atherosclerotic cardiovascular diseases. Novel limiting factors of intracellular trafficking of LDL and the LDL receptor continue to be discovered and to provide drug targets such as PCSK9. Surprisingly, the receptors mediating endocytosis of high-density lipoproteins or lipoprotein(a) are still a matter of controversy or even new discovery. Finally, the receptors and mechanisms, which mediate the uptake of lipoproteins into non-degrading intracellular itineraries for re-secretion (transcytosis, retroendocytosis), storage, or execution of intracellular functions, are largely unknown.
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Affiliation(s)
- Paolo Zanoni
- Institute for Clinical Chemistry, University and University Hospital Zurich, Zurich, Switzerland; Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Srividya Velagapudi
- Institute for Clinical Chemistry, University and University Hospital Zurich, Zurich, Switzerland; Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Mustafa Yalcinkaya
- Institute for Clinical Chemistry, University and University Hospital Zurich, Zurich, Switzerland; Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Lucia Rohrer
- Institute for Clinical Chemistry, University and University Hospital Zurich, Zurich, Switzerland; Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Arnold von Eckardstein
- Institute for Clinical Chemistry, University and University Hospital Zurich, Zurich, Switzerland; Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
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Matsuoka H, Inoue M. Molecular mechanism for muscarinic M 1 receptor-mediated endocytosis of TWIK-related acid-sensitive K + 1 channels in rat adrenal medullary cells. J Physiol 2017; 595:6851-6867. [PMID: 28944482 DOI: 10.1113/jp275039] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 09/15/2017] [Indexed: 01/25/2023] Open
Abstract
KEY POINTS The muscarinic acetylcholine receptor (mAChR)-mediated increase in excitability in rat adrenal medullary cells is at least in part due to inhibition of TWIK (tandem of P domains in a weak inwardly rectifying K+ channel)-related acid-sensitive K+ (TASK)1 channels. In this study we focused on the molecular mechanism of mAChR-mediated inhibition of TASK1 channels. Exposure to muscarine resulted in a clathrin-dependent endocytosis of TASK1 channels following activation of the muscarinic M1 receptor (M1 R). This muscarinic signal for the endocytosis was mediated in sequence by phospholipase C (PLC), protein kinase C (PKC), and then the non-receptor tyrosine kinase Src with the consequent tyrosine phosphorylation of TASK1. The present results establish that TASK1 channels are tyrosine phosphorylated and internalized in a clathrin-dependent manner in response to M1 R stimulation and this translocation is at least in part responsible for muscarinic inhibition of TASK1 channels in rat AM cells. ABSTRACT Activation of muscarinic receptor (mAChR) in rat adrenal medullary (AM) cells induces depolarization through the inhibition of TWIK-related acid-sensitive K+ (TASK)1 channels. Here, pharmacological and immunological approaches were used to elucidate the molecular mechanism for this mAChR-mediated inhibition. TASK1-like immunoreactive (IR) material was mainly located at the cell periphery in dissociated rat AM cells, and its majority was internalized in response to muscarine. The muscarine-induced inward current and translocation of TASK1 were suppressed by dynasore, a dynamin inhibitor. The muscarinic translocation was suppressed by MT7, a specific M1 antagonist, and the dose-response curves for muscarinic agonist-induced translocation were similar to those for the muscarinic inhibition of TASK1 currents. The muscarine-induced inward current and/or translocation of TASK1 were suppressed by inhibitors for phospholipase C (PLC), protein kinase C (PKC), and/or Src. TASK1 channels in AM cells and PC12 cells were transiently associated with Src and were tyrosine phosphorylated in response to muscarinic stimulation. After internalization, TASK1 channels were quickly dephosphorylated even while they remained in the cytoplasm. The cytoplasmic TASK1-like IR material quickly recycled back to the cell periphery after muscarine stimulation for 0.5 min, but not 10 min. We conclude that M1 R stimulation results in internalization of TASK1 channels through the PLC-PKC-Src pathway with the consequent phosphorylation of tyrosine and that this M1 R-mediated internalization is at least in part responsible for muscarinic inhibition of TASK1 channels in rat AM cells.
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Affiliation(s)
- Hidetada Matsuoka
- Department of Cell and Systems Physiology, University of Occupational and Environmental Health School of Medicine, Kitakyushu, 807-8555, Japan
| | - Masumi Inoue
- Department of Cell and Systems Physiology, University of Occupational and Environmental Health School of Medicine, Kitakyushu, 807-8555, Japan
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36
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Proteomic Analysis Reveals Dab2 Mediated Receptor Endocytosis Promotes Liver Sinusoidal Endothelial Cell Dedifferentiation. Sci Rep 2017; 7:13456. [PMID: 29044176 PMCID: PMC5647404 DOI: 10.1038/s41598-017-13917-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 09/29/2017] [Indexed: 01/16/2023] Open
Abstract
Sinusoidal dedifferentiation is a complicated process induced by several factors, and exists in early stage of diverse liver diseases. The mechanism of sinusoidal dedifferentiation is poorly unknown. In this study, we established a NaAsO2-induced sinusoidal dedifferentiation mice model. Liver sinusoidal endothelial cells were isolated and isobaric tag for relative and absolute quantitation (iTRAQ) based proteomic approach was adopted to globally examine the effects of arsenic on liver sinusoidal endothelial cells (LSECs) during the progression of sinusoidal dedifferentiation. In all, 4205 proteins were identified and quantified by iTRAQ combined with LC-MS/MS analysis, of which 310 proteins were significantly changed in NaAsO2 group, compared with the normal control. Validation by western blot showed increased level of clathrin-associated sorting protein Disabled 2 (Dab2) in NaAsO2 group, indicating that it may regulate receptor endocytosis, which served as a mechanism to augment intracellular VEGF signaling. Moreover, we found that knockdown of Dab2 reduced the uptake of VEGF in LSECs, furthermore blocking VEGF-mediated LSEC dedifferentiation and angiogenesis.
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Ong T, Solecki DJ. Seven in Absentia E3 Ubiquitin Ligases: Central Regulators of Neural Cell Fate and Neuronal Polarity. Front Cell Neurosci 2017; 11:322. [PMID: 29081737 PMCID: PMC5646344 DOI: 10.3389/fncel.2017.00322] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 09/26/2017] [Indexed: 12/31/2022] Open
Abstract
During neural development, neural precursors transition from a proliferative state within their germinal niches to a migratory state as they relocate to their final laminar positions. Transitions across these states are coupled with dynamic alterations in cellular polarity. This key feature can be seen throughout the developing vertebrate brain, in which neural stem cells give rise to multipolar or unpolarized transit-amplifying progenitors. These transit-amplifying progenitors then expand to give rise to mature neuronal lineages that become polarized as they initiate radial migration to their final laminar positions. The conventional understanding of the cellular polarity regulatory program has revolved around signaling cascades and transcriptional networks. In this review, we discuss recent discoveries concerning the role of the Siah2 ubiquitin ligase in initiating neuronal polarity during cerebellar development. Given the unique features of Siah ubiquitin ligases, we highlight some of the key substrates that play important roles in cellular polarity and propose a function for the Siah ubiquitin proteasome pathway in mediating a post-translational regulatory network to control the onset of polarization.
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Affiliation(s)
- Taren Ong
- Cancer and Developmental Biology Track, Integrated Biomedical Sciences Graduate Program, University of Tennessee Health Science Center, Memphis, TN, United States.,Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN, United States
| | - David J Solecki
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN, United States
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38
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Wall MJ, Corrêa SAL. The mechanistic link between Arc/Arg3.1 expression and AMPA receptor endocytosis. Semin Cell Dev Biol 2017; 77:17-24. [PMID: 28890421 DOI: 10.1016/j.semcdb.2017.09.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 09/06/2017] [Accepted: 09/06/2017] [Indexed: 02/06/2023]
Abstract
The activity-regulated cytoskeleton associated protein (Arc/Arg3.1) plays a key role in determining synaptic strength through facilitation of AMPA receptor (AMPAR) endocytosis. Although there is considerable data on the mechanism by which Arc induction controls synaptic plasticity and learning behaviours, several key mechanistic questions remain. Here we review data on the link between Arc expression and the clathrin-mediated endocytic pathway which internalises AMPARs and discuss the significance of Arc binding to the clathrin adaptor protein 2 (AP-2) and to endophilin/dynamin. We consider which AMPAR subunits are selected for Arc-mediated internalisation, implications for synaptic function and consider Arc as a therapeutic target.
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Affiliation(s)
- Mark J Wall
- School of Life Sciences, University of Warwick, United Kingdom.
| | - Sonia A L Corrêa
- School of Pharmacy and Medical Sciences, Faculty of Life Sciences, University of Bradford, United Kingdom.
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Kumari V, Desai S, Ameen NA. AP2 α modulates cystic fibrosis transmembrane conductance regulator function in the human intestine. J Cyst Fibros 2017; 16:327-334. [PMID: 28438500 PMCID: PMC5502754 DOI: 10.1016/j.jcf.2017.03.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Revised: 02/15/2017] [Accepted: 03/21/2017] [Indexed: 11/15/2022]
Abstract
BACKGROUND AP2 is a clathrin-based endocytic adaptor complex comprising α, β2, μ2 and σ2 subunits. μ2 regulates CFTR endocytosis. The α subunit interacts with CFTR in the intestine but its physiologic significance is unclear. METHODS CFTR short circuit current was measured in intestinal T84 cells following shRNA knock down of AP2α (AP2αKD). Clathrin-coated structures (CCS) were immunolabeled and quantified in AP2αKD intestinal Caco2BBe (C2BBe) cells. GST tagged human AP2α appendage domain was cloned and its interaction with CFTR determined by GST pull down assay. RESULT AP2αKD in T84 cells resulted in higher CFTR current (57%) compared to control, consistent with increased functional CFTR and delayed endocytosis. Depletion of AP2α reduced CCS in C2BBe cells. Pull down assays revealed an interaction between human AP2α appendage domain and CFTR. CONCLUSION AP2 α interacts with and modulates CFTR function in the intestine by participating in clathrin assembly and recruitment of CFTR to CCS.
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Affiliation(s)
- Vandana Kumari
- Department of Pediatrics/Gastroenterology and Hepatology, Yale School of Medicine, New Haven, CT, United States
| | - Shruti Desai
- Department of Pediatrics/Gastroenterology and Hepatology, Yale School of Medicine, New Haven, CT, United States
| | - Nadia A Ameen
- Department of Pediatrics/Gastroenterology and Hepatology, Yale School of Medicine, New Haven, CT, United States; Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT, United States.
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Sochacki KA, Dickey AM, Strub MP, Taraska JW. Endocytic proteins are partitioned at the edge of the clathrin lattice in mammalian cells. Nat Cell Biol 2017; 19:352-361. [PMID: 28346440 DOI: 10.1038/ncb3498] [Citation(s) in RCA: 132] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 02/23/2017] [Indexed: 12/15/2022]
Abstract
Dozens of proteins capture, polymerize and reshape the clathrin lattice during clathrin-mediated endocytosis (CME). How or if this ensemble of proteins is organized in relation to the clathrin coat is unknown. Here, we map key molecules involved in CME at the nanoscale using correlative super-resolution light and transmission electron microscopy. We localize 19 different endocytic proteins (amphiphysin1, AP2, β2-arrestin, CALM, clathrin, DAB2, dynamin2, EPS15, epsin1, epsin2, FCHO2, HIP1R, intersectin, NECAP, SNX9, stonin2, syndapin2, transferrin receptor, VAMP2) on thousands of individual clathrin structures, generating a comprehensive molecular architecture of endocytosis with nanoscale precision. We discover that endocytic proteins distribute into distinct spatial zones in relation to the edge of the clathrin lattice. The presence or concentrations of proteins within these zones vary at distinct stages of organelle development. We propose that endocytosis is driven by the recruitment, reorganization and loss of proteins within these partitioned nanoscale zones.
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Affiliation(s)
- Kem A Sochacki
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Andrea M Dickey
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Marie-Paule Strub
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Justin W Taraska
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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41
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Brüser L, Bogdan S. Adherens Junctions on the Move-Membrane Trafficking of E-Cadherin. Cold Spring Harb Perspect Biol 2017; 9:cshperspect.a029140. [PMID: 28096264 DOI: 10.1101/cshperspect.a029140] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cadherin-based adherens junctions are conserved structures that mediate epithelial cell-cell adhesion in invertebrates and vertebrates. Despite their pivotal function in epithelial integrity, adherens junctions show a remarkable plasticity that is a prerequisite for tissue architecture and morphogenesis. Epithelial cadherin (E-cadherin) is continuously turned over and undergoes cycles of endocytosis, sorting and recycling back to the plasma membrane. Mammalian cell culture and genetically tractable model systems such as Drosophila have revealed conserved, but also distinct, mechanisms in the regulation of E-cadherin membrane trafficking. Here, we discuss our current knowledge about molecules and mechanisms controlling endocytosis, sorting and recycling of E-cadherin during junctional remodeling.
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Affiliation(s)
- Lena Brüser
- Institut für Neurobiologie, Universität Münster, Badestraße 9, 48149 Münster, Germany
| | - Sven Bogdan
- Institut für Neurobiologie, Universität Münster, Badestraße 9, 48149 Münster, Germany.,Institut für Physiologie und Pathophysiologie, Abteilung Molekulare Zellphysiologie, Phillips-Universität Marburg, Emil-Mannkopff-Straße 2, 35037 Marburg, Germany
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42
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Tao W, Moore R, Smith ER, Xu XX. Endocytosis and Physiology: Insights from Disabled-2 Deficient Mice. Front Cell Dev Biol 2016; 4:129. [PMID: 27933291 PMCID: PMC5122593 DOI: 10.3389/fcell.2016.00129] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 10/27/2016] [Indexed: 01/29/2023] Open
Abstract
Disabled-2 (Dab2) is a clathrin and cargo binding endocytic adaptor protein, and cell biology studies revealed that Dab2 plays a role in cellular trafficking of a number of transmembrane receptors and signaling proteins. A PTB/PID domain located in the N-terminus of Dab2 binds the NPXY motif(s) present at the cytoplasmic tails of certain transmembrane proteins/receptors. The membrane receptors reported to bind directly to Dab2 include LDL receptor and its family members LRP1 and LRP2 (megalin), growth factor receptors EGFR and FGFR, and the cell adhesion receptor beta1 integrin. Dab2 also serves as an adaptor in signaling pathways. Particularly, Dab2 facilitates the endocytosis of the Ras activating Grb2/Sos1 signaling complex, controls its disassembly, and thereby regulates the Ras/MAPK signaling pathway. Cellular analyses have suggested several diverse functions for the widely expressed proteins, and Dab2 is also considered a tumor suppressor, as loss or reduced expression is found in several cancer types. Dab2 null mutant mice were generated and investigated to determine if the findings from cellular studies might be important and relevant in intact animals. Dab2 conditional knockout mice mediated through a Sox2-Cre transgene have no obvious developmental defects and have a normal life span despite that the Dab2 protein is essentially absent in the mutant mice. The conditional knockout mice were grossly normal, though more recent investigation of the Dab2-deficient mice revealed several phenotypes, which can be accounted for by several previously suggested mechanisms. The studies of mutant mice established that Dab2 plays multiple physiological roles through its endocytic functions and modulation of signal pathways.
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Affiliation(s)
- Wensi Tao
- Sylvester Comprehensive Cancer Center and Department of Cell Biology, Graduate Program in Cell and Developmental Biology, University of Miami School of Medicine Miami, FL, USA
| | - Robert Moore
- Sylvester Comprehensive Cancer Center and Department of Cell Biology, Graduate Program in Cell and Developmental Biology, University of Miami School of Medicine Miami, FL, USA
| | - Elizabeth R Smith
- Sylvester Comprehensive Cancer Center and Department of Cell Biology, Graduate Program in Cell and Developmental Biology, University of Miami School of Medicine Miami, FL, USA
| | - Xiang-Xi Xu
- Sylvester Comprehensive Cancer Center and Department of Cell Biology, Graduate Program in Cell and Developmental Biology, University of Miami School of Medicine Miami, FL, USA
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Cadwell CM, Su W, Kowalczyk AP. Cadherin tales: Regulation of cadherin function by endocytic membrane trafficking. Traffic 2016; 17:1262-1271. [PMID: 27624909 DOI: 10.1111/tra.12448] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 09/09/2016] [Accepted: 09/09/2016] [Indexed: 12/17/2022]
Abstract
Cadherins are the primary adhesion molecules in adherens junctions and desmosomes and play essential roles in embryonic development. Although significant progress has been made in understanding cadherin structure and function, we lack a clear vision of how cells confer plasticity upon adhesive junctions to allow for cellular rearrangements during development, wound healing and metastasis. Endocytic membrane trafficking has emerged as a fundamental mechanism by which cells confer a dynamic state to adhesive junctions. Recent studies indicate that the juxtamembrane domain of classical cadherins contains multiple endocytic motifs, or "switches," that can be used by cellular membrane trafficking machinery to regulate adhesion. The cadherin-binding protein p120-catenin (p120) appears to be the master regulator of access to these switches, thereby controlling cadherin endocytosis and turnover. This review focuses on p120 and other cadherin-binding proteins, ubiquitin ligases, and growth factors as key modulators of cadherin membrane trafficking.
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Affiliation(s)
- Chantel M Cadwell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia
| | - Wenji Su
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia.,Biochemistry, Cell, and Developmental Biology Graduate Training Program, Emory University, Atlanta, Georgia
| | - Andrew P Kowalczyk
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia.,Department of Dermatology, Emory University School of Medicine, Atlanta, Georgia.,Winship Cancer Institute, Emory University, Atlanta, Georgia
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44
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Disabled-2 Determines Commitment of a Pre-adipocyte Population in Juvenile Mice. Sci Rep 2016; 6:35947. [PMID: 27779214 PMCID: PMC5078790 DOI: 10.1038/srep35947] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 10/06/2016] [Indexed: 01/01/2023] Open
Abstract
Disabled-2 (Dab2) is a widely expressed clathrin binding endocytic adaptor protein and known for the endocytosis of the low-density lipoprotein (LDL) family receptors. Dab2 also modulates endosomal Ras/MAPK (Erk1/2) activity by regulating the disassembly of Grb2/Sos1 complexes associated with clathrin-coated vesicles. We found that the most prominent phenotype of Dab2 knockout mice was their striking lean body composition under a high fat and high caloric diet, although the weight of the mutant mice was indistinguishable from wild-type littermates on a regular chow. The remarkable difference in resistance to high caloric diet-induced weight gain of the dab2-deleted mice was presented only in juvenile but not in mature mice. Investigation using Dab2-deficient embryonic fibroblasts and mesenchymal stromal cells indicated that Dab2 promoted adipogenic differentiation by modulation of MAPK (Erk1/2) activity, which otherwise suppresses adipogenesis through the phosphorylation of PPARγ. The results suggest that Dab2 is required for the excessive calorie-induced differentiation of an adipocyte progenitor cell population that is present in juvenile but depleted in mature animals. The finding provides evidence for a limited pre-adipocyte population in juvenile mammals and the requirement of Dab2 in the regulation of Ras/MAPK signal in the commitment of the precursor cells to adipose tissues.
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45
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Hung WS, Ling P, Cheng JC, Chang SS, Tseng CP. Disabled-2 is a negative immune regulator of lipopolysaccharide-stimulated Toll-like receptor 4 internalization and signaling. Sci Rep 2016; 6:35343. [PMID: 27748405 PMCID: PMC5066213 DOI: 10.1038/srep35343] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 09/28/2016] [Indexed: 12/15/2022] Open
Abstract
Toll-like receptor 4 (TLR4) plays a pivotal role in the host response to lipopolysaccharide (LPS), a major cell wall component of Gram-negative bacteria. Here, we elucidated whether the endocytic adaptor protein Disabled-2 (Dab2), which is abundantly expressed in macrophages, plays a role in LPS-stimulated TLR4 signaling and trafficking. Molecular analysis and transcriptome profiling of RAW264.7 macrophage-like cells expressing short-hairpin RNA of Dab2 revealed that Dab2 regulated the TLR4/TRIF pathway upon LPS stimulation. Knockdown of Dab2 augmented TRIF-dependent interferon regulatory factor 3 activation and the expression of subsets of inflammatory cytokines and interferon-inducible genes. Dab2 acted as a clathrin sponge and sequestered clathrin from TLR4 in the resting stage of macrophages. Upon LPS stimulation, clathrin was released from Dab2 to facilitate endocytosis of TLR4 for triggering the TRIF-mediated pathway. Dab2 functions as a negative immune regulator of TLR4 endocytosis and signaling, supporting a novel role for a Dab2-associated regulatory circuit in controlling the inflammatory response of macrophages to endotoxin.
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Affiliation(s)
- Wei-Shan Hung
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Kwei-Shan, Taoyuan 333, Taiwan, Republic of China
| | - Pin Ling
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan, Republic of China.,Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan, Republic of China
| | - Ju-Chien Cheng
- Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung 404, Taiwan, Republic of China
| | - Shy-Shin Chang
- Department of Family Medicine, Chang Gung Memorial Hospital, Kweishan, Taoyuan 333, Taiwan, Republic of China
| | - Ching-Ping Tseng
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Kwei-Shan, Taoyuan 333, Taiwan, Republic of China.,Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Kwei-Shan, Taoyuan 333, Taiwan, Republic of China.,Molecular Medicine Research Center, Chang Gung University, Kwei-Shan, Taoyuan 333, Taiwan, Republic of China.,Department of Laboratory Medicine, Chang Gung Memorial Hospital, Kwei-Shan, Taoyuan 333, Taiwan, Republic of China
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46
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Song K, Wu H, Rahman HNA, Dong Y, Wen A, Brophy ML, Wong S, Kwak S, Bielenberg DR, Chen H. Endothelial epsins as regulators and potential therapeutic targets of tumor angiogenesis. Cell Mol Life Sci 2016; 74:393-398. [PMID: 27572288 DOI: 10.1007/s00018-016-2347-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 08/17/2016] [Accepted: 08/22/2016] [Indexed: 12/16/2022]
Abstract
VEGF-driven tumor angiogenesis has been validated as a central target in several tumor types deserving of continuous and further considerations to improve the efficacy and selectivity of the current therapeutic paradigms. Epsins, a family of endocytic clathrin adaptors, have been implicated in regulating endothelial cell VEGFR2 signaling, where its inactivation leads to nonproductive leaky neo-angiogenesis and, therefore, impedes tumor development and progression. Targeting endothelial epsins is of special significance due to its lack of affecting other angiogenic-signaling pathways or disrupting normal quiescent vessels, suggesting a selective modulation of tumor angiogenesis. This review highlights seminal findings on the critical role of endothelial epsins in tumor angiogenesis and their underlying molecular events, as well as strategies to prohibit the normal function of endogenous endothelial epsins that capitalize on these newly understood mechanisms.
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Affiliation(s)
- Kai Song
- Vascular Biology Program, Karp Family Research Laboratory, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 12.214, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Hao Wu
- Vascular Biology Program, Karp Family Research Laboratory, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 12.214, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - H N Ashiqur Rahman
- Vascular Biology Program, Karp Family Research Laboratory, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 12.214, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Yunzhou Dong
- Vascular Biology Program, Karp Family Research Laboratory, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 12.214, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Aiyun Wen
- Vascular Biology Program, Karp Family Research Laboratory, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 12.214, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Megan L Brophy
- Vascular Biology Program, Karp Family Research Laboratory, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 12.214, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Scott Wong
- Vascular Biology Program, Karp Family Research Laboratory, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 12.214, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Sukyoung Kwak
- Vascular Biology Program, Karp Family Research Laboratory, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 12.214, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Diane R Bielenberg
- Vascular Biology Program, Karp Family Research Laboratory, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 12.214, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Hong Chen
- Vascular Biology Program, Karp Family Research Laboratory, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 12.214, 300 Longwood Avenue, Boston, MA, 02115, USA.
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Pucadyil TJ, Holkar SS. Comparative analysis of adaptor-mediated clathrin assembly reveals general principles for adaptor clustering. Mol Biol Cell 2016; 27:3156-3163. [PMID: 27559129 PMCID: PMC5063622 DOI: 10.1091/mbc.e16-06-0399] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 08/19/2016] [Indexed: 11/30/2022] Open
Abstract
Clathrin-mediated endocytosis sorts the bulk of membrane proteins and is a process that starts with adaptor-induced clathrin assembly. Real-time fluorescence analysis shows that adaptor sorting is determined not by the extent of clathrin recruited or the degree of clathrin clustered but instead by the rate of clathrin assembly. Clathrin-mediated endocytosis (CME) manages the sorting and uptake of the bulk of membrane proteins (or cargo) from the plasma membrane. CME is initiated by the formation of clathrin-coated pits (CCPs), in which adaptors nucleate clathrin assembly. Clathrin adaptors display diversity in both the type and number of evolutionarily conserved clathrin-binding boxes. How this diversity relates to the process of adaptor clustering as clathrin assembles around a growing pit remains unclear. Using real-time, fluorescence microscopy–based assays, we compare the formation kinetics and distribution of clathrin assemblies on membranes that display five unique clathrin adaptors. Correlations between equilibrium and kinetic parameters of clathrin assembly to the eventual adaptor distribution indicate that adaptor clustering is determined not by the amount of clathrin recruited or the degree of clathrin clustered but instead by the rate of clathrin assembly. Together our results emphasize the need to analyze kinetics of protein interactions to better understand mechanisms that regulate CME.
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Affiliation(s)
- Thomas J Pucadyil
- Indian Institute of Science Education and Research, Pune, Maharashtra 411 008, India
| | - Sachin S Holkar
- Indian Institute of Science Education and Research, Pune, Maharashtra 411 008, India
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48
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de León N, Valdivieso MH. The long life of an endocytic patch that misses AP-2. Curr Genet 2016; 62:765-770. [PMID: 27126383 DOI: 10.1007/s00294-016-0605-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 04/15/2016] [Indexed: 10/21/2022]
Abstract
Endocytosis is the process by which cells regulate extracellular fluid uptake and internalize molecules bound to their plasma membrane. This process requires the generation of protein-coated vesicles. In clathrin-mediated endocytosis (CME) the assembly polypeptide 2 (AP-2) adaptor facilitates rapid endocytosis of some plasma membrane receptors by mediating clathrin recruitment to the endocytic site and by connecting cargoes to the clathrin coat. While this adaptor is essential for early embryonic development in mammals, initial results suggested that it is dispensable for endocytosis in unicellular eukaryotes. The drastic effect of depleting AP-2 in metazoa and the mild effect of deleting AP-2 subunits in Saccharomyces cerevisiae have prevented a detailed analysis of the dynamics of endocytic patches in the absence of this adaptor. Using live-cell imaging of Schizosaccharomyces pombe endocytic sites we have shown that eliminating AP-2 perturbs the dynamics of endocytic patches beyond the moment of coat assembly. These perturbations affect the cell growth pattern and cell wall synthesis. Our results highlight the importance of using different model organisms to address the study of conserved aspects of CME.
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Affiliation(s)
- Nagore de León
- Departamento de Microbiología y Genética/Instituto de Biología Funcional y Genómica (IBFG), University of Salamanca/CSIC, Calle Zacarías González 2, 37007, Salamanca, Spain.,Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK
| | - M-Henar Valdivieso
- Departamento de Microbiología y Genética/Instituto de Biología Funcional y Genómica (IBFG), University of Salamanca/CSIC, Calle Zacarías González 2, 37007, Salamanca, Spain.
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Akita H, Fujiwara T, Santiwarangkool S, Hossen N, Kajimoto K, El-Sayed A, Tabata Y, Harashima H. Transcytosis-Targeting Peptide: A Conductor of Liposomal Nanoparticles through the Endothelial Cell Barrier. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2016; 12:1212-1221. [PMID: 26426116 DOI: 10.1002/smll.201500909] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Revised: 07/19/2015] [Indexed: 06/05/2023]
Abstract
The ultimate goal in the area of drug-delivery systems is the development of a nanoparticle that can penetrate the endothelial cell monolayer for the targeting of tissue parenchyma. In the present study, we identify a transcytosis-targeting peptide (TTP) that permits polyethyleneglycol (PEG)-modified liposomes (PEG-LPs) to penetrate through monolayers of brain-derived endothelial cells. These endothelial cells were layered on a gelatin nanofiber sheet, a nanofiber meshwork that allows the evaluation of transcellular transport of nanosized particles (ca. 100 nm). Systematic modification of the sequences results in the identification of the consensus sequence of TTP as L(R/K)QZZZL, where Z denotes hydrophilic amino acids (R/K/S and partially D). The TTP-modified liposomes are bound on the heparin sulfate proteoglycan, and are then taken up via lipid raft-mediated endocytosis. Subsequent intracellular imaging of the particles reveals a unique intracellular sorting of TTP-modified PEG liposomes (TTP-PEG-LPs); namely the TTP-LPs are not localized with the lysosomes, whereas this co-localization is dominant in the unmodified PEG liposomes (PEG-LPs). The in vivo endothelial penetration of liposomes in adipose tissue is conferred by the dual modification of the particles with TTP and tissue-targeting ligands. This technology promises innovations in intravenously available delivery system to tissue parenchyma.
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Affiliation(s)
- Hidetaka Akita
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita12 Nishi6, Kita-ku, Sapporo City, Hokkaido, 060-0812, Japan
| | - Takahiro Fujiwara
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita12 Nishi6, Kita-ku, Sapporo City, Hokkaido, 060-0812, Japan
| | - Sarochin Santiwarangkool
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita12 Nishi6, Kita-ku, Sapporo City, Hokkaido, 060-0812, Japan
| | - Nazir Hossen
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita12 Nishi6, Kita-ku, Sapporo City, Hokkaido, 060-0812, Japan
| | - Kazuaki Kajimoto
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita12 Nishi6, Kita-ku, Sapporo City, Hokkaido, 060-0812, Japan
| | - Ayman El-Sayed
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita12 Nishi6, Kita-ku, Sapporo City, Hokkaido, 060-0812, Japan
| | - Yasuhiko Tabata
- Institute for Frontier Medical Sciences, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Hideyoshi Harashima
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita12 Nishi6, Kita-ku, Sapporo City, Hokkaido, 060-0812, Japan
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σ2-Adaptin Facilitates Basal Synaptic Transmission and Is Required for Regenerating Endo-Exo Cycling Pool Under High-Frequency Nerve Stimulation in Drosophila. Genetics 2016; 203:369-85. [PMID: 26920756 DOI: 10.1534/genetics.115.183863] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 02/21/2016] [Indexed: 11/18/2022] Open
Abstract
The functional requirement of adapter protein 2 (AP2) complex in synaptic membrane retrieval by clathrin-mediated endocytosis is not fully understood. Here we isolated and functionally characterized a mutation that dramatically altered synaptic development. Based on the aberrant neuromuscular junction (NMJ) synapse, we named this mutation angur (a Hindi word meaning "grapes"). Loss-of-function alleles of angur show more than twofold overgrowth in bouton numbers and a dramatic decrease in bouton size. We mapped the angur mutation to σ2-adaptin, the smallest subunit of the AP2 complex. Reducing the neuronal level of any of the subunits of the AP2 complex or disrupting AP2 complex assembly in neurons phenocopied the σ2-adaptin mutation. Genetic perturbation of σ2-adaptin in neurons leads to a reversible temperature-sensitive paralysis at 38°. Electrophysiological analysis of the mutants revealed reduced evoked junction potentials and quantal content. Interestingly, high-frequency nerve stimulation caused prolonged synaptic fatigue at the NMJs. The synaptic levels of subunits of the AP2 complex and clathrin, but not other endocytic proteins, were reduced in the mutants. Moreover, bone morphogenetic protein (BMP)/transforming growth factor β (TGFβ) signaling was altered in these mutants and was restored by normalizing σ2-adaptin in neurons. Thus, our data suggest that (1) while σ2-adaptin facilitates synaptic vesicle (SV) recycling for basal synaptic transmission, its activity is also required for regenerating SVs during high-frequency nerve stimulation, and (2) σ2-adaptin regulates NMJ morphology by attenuating TGFβ signaling.
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