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Zuliani JP, Yamanouye N, Gutiérrez JM, Teixeira C. PKC-α is involved in the signaling of phagocytosis induced by two snake venom secretory PLA 2S in macrophages. Toxicon 2024; 247:107824. [PMID: 38908525 DOI: 10.1016/j.toxicon.2024.107824] [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: 04/23/2024] [Revised: 06/18/2024] [Accepted: 06/19/2024] [Indexed: 06/24/2024]
Abstract
Phagocytosis, an essential process for host defense, requires the coordination of a variety of signaling reactions. MT-II, an enzymatically inactive Lys49 phospholipase A2 (PLA2) homolog, and MT-III, a catalytically-active Asp49 PLA2, are known to activate phagocytosis in macrophages. In this study, the signaling pathways mediating phagocytosis, focusing on protein kinases, were investigated. Macrophages from male Swiss mice peritoneum were obtained 96 h after intraperitoneal thioglycolate injection. Phagocytosis was evaluated using non-opsonized zymosan particles in the presence or absence of specific inhibitors, as well as PKC and PKC-α localization by confocal microscopy. Moreover, protein kinase C (PKC) activity was assessed by γP32 ATP in macrophages stimulated by both PLA2s. Data showed that both sPLA2s increased phagocytosis. Cytochalasin D, staurosporine/H7, wortmannin, and herbimycin, inhibitors of actin polymerization, PKC, phosphoinositide 3-kinase (PI3K), and protein tyrosine kinase (PTK), respectively, significantly reduced phagocytosis induced by both PLA2s. PKC activity was increased in macrophages stimulated by both PLA2s. Actin polymerization and talin were evidenced by immunofluorescence and talin was recruited 5 min after both PLA2s stimulation. PKC and PKC-α localization within the cell were increased after 60 min of MT-II and MT-III stimulation. These data suggest that the effect of both PLA2s depends on actin cytoskeleton rearrangements and the activation of PKC, PI3K, and PTK signaling events required for phagocytosis.
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Affiliation(s)
- Juliana Pavan Zuliani
- Laboratório de Farmacologia - Instituto Butantan, São Paulo, Brazil; Laboratório de Imunologia Celular Aplicada à Saúde, Fundação Oswaldo Cruz Rondônia/FIOCRUZ-RO, Porto Velho, RO, Brazil; Dep. Medicina, Universidade Federal de Rondônia, UNIR, Porto Velho, RO, Brazil.
| | - Norma Yamanouye
- Laboratório de Farmacologia - Instituto Butantan, São Paulo, Brazil.
| | - José María Gutiérrez
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Catarina Teixeira
- Laboratório de Farmacologia - Instituto Butantan, São Paulo, Brazil.
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2
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Le T, Ferling I, Qiu L, Nabaile C, Assunção L, Roskelley CD, Grinstein S, Freeman SA. Redistribution of the glycocalyx exposes phagocytic determinants on apoptotic cells. Dev Cell 2024; 59:853-868.e7. [PMID: 38359833 DOI: 10.1016/j.devcel.2024.01.020] [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: 04/12/2023] [Revised: 11/08/2023] [Accepted: 01/23/2024] [Indexed: 02/17/2024]
Abstract
Phagocytes remove dead and dying cells by engaging "eat-me" ligands such as phosphatidylserine (PtdSer) on the surface of apoptotic targets. However, PtdSer is obscured by the bulky exofacial glycocalyx, which also exposes ligands that activate "don't-eat-me" receptors such as Siglecs. Clearly, unshielding the juxtamembrane "eat-me" ligands is required for the successful engulfment of apoptotic cells, but the mechanisms underlying this process have not been described. Using human and murine cells, we find that apoptosis-induced retraction and weakening of the cytoskeleton that anchors transmembrane proteins cause an inhomogeneous redistribution of the glycocalyx: actin-depleted blebs emerge, lacking the glycocalyx, while the rest of the apoptotic cell body retains sufficient actin to tether the glycocalyx in place. Thus, apoptotic blebs can be engaged by phagocytes and are targeted for engulfment. Therefore, in cells with an elaborate glycocalyx, such as mucinous cancer cells, this "don't-come-close-to-me" barrier must be removed to enable clearance by phagocytosis.
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Affiliation(s)
- Trieu Le
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Iuliia Ferling
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Lanhui Qiu
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Clement Nabaile
- Department of Learning and Research in Biology, Ecole Normale Supérieure Paris-Saclay, Gif-sur-Yvette, France
| | - Leonardo Assunção
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Calvin D Roskelley
- Department of Cellular and Physiological Sciences, the Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Sergio Grinstein
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Spencer A Freeman
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada.
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3
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Barreda D, Grinstein S, Freeman SA. Target lysis by cholesterol extraction is a rate limiting step in the resolution of phagolysosomes. Eur J Cell Biol 2024; 103:151382. [PMID: 38171214 DOI: 10.1016/j.ejcb.2023.151382] [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: 11/14/2023] [Revised: 12/22/2023] [Accepted: 12/25/2023] [Indexed: 01/05/2024] Open
Abstract
The ongoing phagocytic activity of macrophages necessitates an extraordinary capacity to digest and resolve incoming material. While the initial steps leading to the formation of a terminal phagolysosome are well studied, much less is known about the later stages of this process, namely the degradation and resolution of the phagolysosomal contents. We report that the degradation of targets such as splenocytes and erythrocytes by phagolysosomes occurs in a stepwise fashion, requiring lysis of their plasmalemmal bilayer as an essential initial step. This is achieved by the direct extraction of cholesterol facilitated by Niemann-Pick protein type C2 (NPC2), which in turn hands off cholesterol to NPC1 for export from the phagolysosome. The removal of cholesterol ulimately destabilizes and permeabilizes the membrane of the phagocytic target, allowing access of hydrolases to its internal compartments. In contrast, we found that saposins, which activate the hydrolysis of sphingolipids, are required for lysosomal tubulation, yet are dispensable for the resolution of targets by macrophages. The extraction of cholesterol by NPC2 is therefore envisaged as rate-limiting in the clearance of membrane-bound targets such as apoptotic cells. Selective cholesterol removal appears to be a primary mechanism that enables professional phagocytes to distinguish the target membrane from the phagolysosomal membrane and may be conserved in the resolution of autolysosomes.
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Affiliation(s)
- Dante Barreda
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Sergio Grinstein
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Biochemistry and the University of Toronto, Toronto, ON M5S 1A8, Canada; Institute of Medical Science, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Spencer A Freeman
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Biochemistry and the University of Toronto, Toronto, ON M5S 1A8, Canada.
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4
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Drexhage LZ, Zhang S, Dupont M, Ragaller F, Sjule E, Cabezas-Caballero J, Deimel LP, Robertson H, Russell RA, Dushek O, Sezgin E, Karaji N, Sattentau QJ. Apoptosis-mediated ADAM10 activation removes a mucin barrier promoting T cell efferocytosis. Nat Commun 2024; 15:541. [PMID: 38225245 PMCID: PMC10789802 DOI: 10.1038/s41467-023-44619-8] [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: 04/19/2023] [Accepted: 12/22/2023] [Indexed: 01/17/2024] Open
Abstract
Efferocytic clearance of apoptotic cells in general, and T cells in particular, is required for tissue and immune homeostasis. Transmembrane mucins are extended glycoproteins highly expressed in the cell glycocalyx that function as a barrier to phagocytosis. Whether and how mucins may be regulated during cell death to facilitate efferocytic corpse clearance is not well understood. Here we show that normal and transformed human T cells express a subset of mucins which are rapidly and selectively removed from the cell surface during apoptosis. This process is mediated by the ADAM10 sheddase, the activity of which is associated with XKR8-catalyzed flipping of phosphatidylserine to the outer leaflet of the plasma membrane. Mucin clearance enhances uptake of apoptotic T cells by macrophages, confirming mucins as an enzymatically-modulatable barrier to efferocytosis. Together these findings demonstrate a glycocalyx regulatory pathway with implications for therapeutic intervention in the clearance of normal and transformed apoptotic T cells.
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Affiliation(s)
- Linnea Z Drexhage
- The Sir William Dunn School of Pathology, The University of Oxford, Oxford, OX13RE, UK
| | - Shengpan Zhang
- The Sir William Dunn School of Pathology, The University of Oxford, Oxford, OX13RE, UK
| | - Maeva Dupont
- The Sir William Dunn School of Pathology, The University of Oxford, Oxford, OX13RE, UK
- Immunocore Ltd., 92 Park Dr, Milton, Abingdon, OX14 4RY, UK
| | - Franziska Ragaller
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, 17165, Solna, Sweden
| | - Ellen Sjule
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, 17165, Solna, Sweden
| | | | - Lachlan P Deimel
- The Sir William Dunn School of Pathology, The University of Oxford, Oxford, OX13RE, UK
| | - Helen Robertson
- The Sir William Dunn School of Pathology, The University of Oxford, Oxford, OX13RE, UK
| | - Rebecca A Russell
- The Sir William Dunn School of Pathology, The University of Oxford, Oxford, OX13RE, UK
- SpyBiotech Ltd.; 7600 Quorum, Oxford Business Park North, Oxford, OX4 2JZ, UK
| | - Omer Dushek
- The Sir William Dunn School of Pathology, The University of Oxford, Oxford, OX13RE, UK
| | - Erdinc Sezgin
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, 17165, Solna, Sweden
| | - Niloofar Karaji
- The Sir William Dunn School of Pathology, The University of Oxford, Oxford, OX13RE, UK.
- Oxford Biomedica plc.; Windrush Court, Transport Way, Oxford, OX4 6LT, UK.
| | - Quentin J Sattentau
- The Sir William Dunn School of Pathology, The University of Oxford, Oxford, OX13RE, UK.
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association; Berlin-Buch, 13125, Berlin, Germany.
- Experimental and Clinical Research Center (ECRC), Charité Universitätsmedizin Berlin and Max-Delbrück-Center for Molecular Medicine, Lindenberger Weg 80, 13125, Berlin, Germany.
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5
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Mylvaganam S, Freeman SA. The resolution of phagosomes. Immunol Rev 2023; 319:45-64. [PMID: 37551912 DOI: 10.1111/imr.13260] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 07/18/2023] [Indexed: 08/09/2023]
Abstract
Phagocytosis is a fundamental immunobiological process responsible for the removal of harmful particulates. While the number of phagocytic events achieved by a single phagocyte can be remarkable, exceeding hundreds per day, the same phagocytic cells are relatively long-lived. It should therefore be obvious that phagocytic meals must be resolved in order to maintain the responsiveness of the phagocyte and to avoid storage defects. In this article, we discuss the mechanisms involved in the resolution process, including solute transport pathways and membrane traffic. We describe how products liberated in phagolysosomes support phagocyte metabolism and the immune response. We also speculate on mechanisms involved in the redistribution of phagosomal metabolites back to circulation. Finally, we highlight the pathologies owed to impaired phagosome resolution, which range from storage disorders to neurodegenerative diseases.
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Affiliation(s)
- Sivakami Mylvaganam
- Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Spencer A Freeman
- Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
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6
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Tan LX, Germer CJ, Thamban T, La Cunza N, Lakkaraju A. Optineurin tunes outside-in signaling to regulate lysosome biogenesis and phagocytic clearance in the retina. Curr Biol 2023; 33:3805-3820.e7. [PMID: 37586372 PMCID: PMC10529777 DOI: 10.1016/j.cub.2023.07.031] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 06/16/2023] [Accepted: 07/19/2023] [Indexed: 08/18/2023]
Abstract
Balancing the competing demands of phagolysosomal degradation and autophagy is a significant challenge for phagocytic tissues. Yet how this plasticity is accomplished in health and disease is poorly understood. In the retina, circadian phagocytosis and degradation of photoreceptor outer segments by the postmitotic retinal pigment epithelium (RPE) are essential for healthy vision. Disrupted autophagy due to mechanistic target of rapamycin (mTOR) overactivation in the RPE is associated with blinding macular degenerations; however, outer segment degradation is unaffected in these diseases, indicating that distinct mechanisms regulate these clearance mechanisms. Here, using advanced imaging and mouse models, we identify optineurin as a key regulator that tunes phagocytosis and lysosomal capacity to meet circadian demands and helps prioritize outer segment clearance by the RPE in macular degenerations. High-resolution live-cell imaging implicates optineurin in scissioning outer segment tips prior to engulfment, analogous to microglial trogocytosis of neuronal processes. Optineurin is essential for recruiting light chain 3 (LC3), which anchors outer segment phagosomes to microtubules and facilitates phagosome maturation and fusion with lysosomes. This dynamically activates transcription factor EB (TFEB) to induce lysosome biogenesis in an mTOR-independent, transient receptor potential-mucolipin 1 (TRPML1)-dependent manner. RNA-seq analyses show that expression of TFEB target genes temporally tracks with optineurin recruitment and that lysosomal and autophagy genes are controlled by distinct transcriptional programs in the RPE. The unconventional plasma membrane-to-nucleus signaling mediated by optineurin ensures outer segment degradation under conditions of impaired autophagy in macular degeneration models. Independent regulation of these critical clearance mechanisms would help safeguard the metabolic fitness of the RPE throughout the organismal lifespan.
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Affiliation(s)
- Li Xuan Tan
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Colin J Germer
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Pharmaceutical Sciences and Pharmacogenomics Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Thushara Thamban
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Nilsa La Cunza
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Pharmaceutical Sciences and Pharmacogenomics Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Aparna Lakkaraju
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Pharmaceutical Sciences and Pharmacogenomics Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Anatomy, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA.
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7
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Umapathy A, Torten G, Paniagua AE, Chung J, Tomlinson M, Lim C, Williams DS. Spatiotemporal Live-Cell Analysis of Photoreceptor Outer Segment Membrane Ingestion by the Retinal Pigment Epithelium Reveals Actin-Regulated Scission. J Neurosci 2023; 43:2653-2664. [PMID: 36878726 PMCID: PMC10089248 DOI: 10.1523/jneurosci.1726-22.2023] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 01/16/2023] [Accepted: 01/18/2023] [Indexed: 03/08/2023] Open
Abstract
The photoreceptor outer segment (OS) is the phototransductive organelle in the vertebrate retina. OS tips are regularly ingested and degraded by the adjacent retinal pigment epithelium (RPE), offsetting the addition of new disk membrane at the base of the OS. This catabolic role of the RPE is essential for photoreceptor health, with defects in ingestion or degradation underlying different forms of retinal degeneration and blindness. Although proteins required for OS tip ingestion have been identified, spatiotemporal analysis of the ingestion process in live RPE cells is lacking; hence, the literature reflects no common understanding of the cellular mechanisms that affect ingestion. We imaged live RPE cells from mice (both sexes) to elucidate the ingestion events in real time. Our imaging revealed roles for f-actin dynamics and specific dynamic localizations of two BAR (Bin-Amphiphysin-Rvs) proteins, FBP17 and AMPH1-BAR, in shaping the RPE apical membrane as it surrounds the OS tip. Completion of ingestion was observed to occur by scission of the OS tip from the remainder of the OS, with a transient concentration of f-actin forming around the site of imminent scission. Actin dynamics were also required for regulating the size of the ingested OS tip, and the time course of the overall ingestion process. The size of the ingested tip is consistent with the term "phagocytosis." However, phagocytosis usually refers to engulfment of an entire particle or cell, whereas our observations of OS tip scission indicate a process that is more specifically described as "trogocytosis," in which one cell "nibbles" another cell.SIGNIFICANCE STATEMENT The ingestion of the photoreceptor outer segment (OS) tips by the retinal pigment epithelium (RPE) is a dynamic cellular process that has fascinated scientists for 60 years. Yet its molecular mechanisms had not been addressed in living cells. We developed a live-cell imaging approach to investigate OS tip ingestion, and focused on the dynamic participation of actin filaments and membrane-shaping BAR proteins. We observed scission of OS tips for the first time, and were able to monitor local changes in protein concentration preceding, during, and following scission. Our approach revealed that actin filaments were concentrated at the site of OS scission and were required for regulating the size of the ingested OS tip and the time course of the ingestion process.
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Affiliation(s)
- Ankita Umapathy
- Department of Ophthalmology and Stein Eye Institute, and Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - Gil Torten
- Department of Ophthalmology and Stein Eye Institute, and Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - Antonio E Paniagua
- Department of Ophthalmology and Stein Eye Institute, and Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - Julie Chung
- Department of Ophthalmology and Stein Eye Institute, and Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - Madeline Tomlinson
- Department of Ophthalmology and Stein Eye Institute, and Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - Caleb Lim
- Department of Ophthalmology and Stein Eye Institute, and Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - David S Williams
- Department of Ophthalmology and Stein Eye Institute, and Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
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8
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Ghasempour S, Freeman SA. The glycocalyx and immune evasion in cancer. FEBS J 2023; 290:55-65. [PMID: 34665926 DOI: 10.1111/febs.16236] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 09/27/2021] [Accepted: 10/18/2021] [Indexed: 01/14/2023]
Abstract
In order to establish malignant lesions, tumors must first evade their detection by immune cells. Tumors achieve this by embellishing and tailoring their glycocalyx, a network of polysaccharides and glycosylated proteins that refracts the phagocytic efforts of myeloid cells, shrouds neoantigens and other ligands from cells of the acquired immune system, and skews immune responses. The barriers imposed by the glycocalyx are biophysical and also linked to the inhibitory receptor signaling pathways of immune cells that engage tumor sialic acids as markers of healthy "self". This would explain the pressure for cancers to upregulate the synthases, transmembrane mucins, and other heavily sialylated glycoproteins involved in establishing a repulsive glycocalyx. Accordingly, individual tumor cells that are best capable of constructing a shielding glycocalyx on their surface show higher metastatic potential in immunocompetent mice. Reciprocally, therapeutics have recently been devised to edit and dismantle the glycocalyx barrier in an effort to invigorate an immune response aimed at tumor destruction. We discuss the features of the tumor-associated glycocalyx that afford immune evasion of cancers and how strategies that target this barrier may potentiate antitumor immunity.
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Affiliation(s)
- Sina Ghasempour
- Program in Cell Biology, Hospital for Sick Children, Toronto, Canada.,Department of Biochemistry, University of Toronto, Canada
| | - Spencer A Freeman
- Program in Cell Biology, Hospital for Sick Children, Toronto, Canada.,Department of Biochemistry, University of Toronto, Canada
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9
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Efferocytosis requires periphagosomal Ca 2+-signaling and TRPM7-mediated electrical activity. Nat Commun 2022; 13:3230. [PMID: 35680919 PMCID: PMC9184625 DOI: 10.1038/s41467-022-30959-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 05/26/2022] [Indexed: 11/21/2022] Open
Abstract
Efficient clearance of apoptotic cells by phagocytosis, also known as efferocytosis, is fundamental to developmental biology, organ physiology, and immunology. Macrophages use multiple mechanisms to detect and engulf apoptotic cells, but the signaling pathways that regulate the digestion of the apoptotic cell cargo, such as the dynamic Ca2+ signals, are poorly understood. Using an siRNA screen, we identify TRPM7 as a Ca2+-conducting ion channel essential for phagosome maturation during efferocytosis. Trpm7-targeted macrophages fail to fully acidify or digest their phagosomal cargo in the absence of TRPM7. Through perforated patch electrophysiology, we demonstrate that TRPM7 mediates a pH-activated cationic current necessary to sustain phagosomal acidification. Using mice expressing a genetically-encoded Ca2+ sensor, we observe that phagosome maturation requires peri-phagosomal Ca2+-signals dependent on TRPM7. Overall, we reveal TRPM7 as a central regulator of phagosome maturation during macrophage efferocytosis. Efficient removal of apoptotic cells by phagocytosis underlies tissue development, wound repair, host defense and organ homeostasis. Here, authors identify TRPM7 as a regulator of cargo acidification and Ca2+ signaling during apoptotic cell clearance.
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10
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Davis LC, Morgan AJ, Galione A. Acidic Ca 2+ stores and immune-cell function. Cell Calcium 2021; 101:102516. [PMID: 34922066 DOI: 10.1016/j.ceca.2021.102516] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 12/03/2021] [Accepted: 12/04/2021] [Indexed: 12/11/2022]
Abstract
Acidic organelles act as intracellular Ca2+ stores; they actively sequester Ca2+ in their lumina and release it to the cytosol upon activation of endo-lysosomal Ca2+ channels. Recent data suggest important roles of endo-lysosomal Ca2+ channels, the Two-Pore Channels (TPCs) and the TRPML channels (mucolipins), in different aspects of immune-cell function, particularly impacting membrane trafficking, vesicle fusion/fission and secretion. Remarkably, different channels on the same acidic vesicles can couple to different downstream physiology. Endo-lysosomal Ca2+ stores can act under different modalities, be they acting alone (via local Ca2+ nanodomains around TPCs/TRPMLs) or in conjunction with the ER Ca2+ store (to either promote or suppress global ER Ca2+ release). These different modalities impinge upon functions as broad as phagocytosis, cell-killing, anaphylaxis, immune memory, thrombostasis, and chemotaxis.
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Affiliation(s)
- Lianne C Davis
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, OX1 3QT, UK.
| | - Anthony J Morgan
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, OX1 3QT, UK
| | - Antony Galione
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, OX1 3QT, UK.
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