51
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Effect of Specific Mutations in Cd300 Complexes Formation; Potential Implication of Cd300f in Multiple Sclerosis. Sci Rep 2017; 7:13544. [PMID: 29051512 PMCID: PMC5648872 DOI: 10.1038/s41598-017-12881-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 09/15/2017] [Indexed: 12/15/2022] Open
Abstract
Herein, we have used bioinformatics tools to predict five clusters defining ligand-binding sites on the extracellular domain of human CD300b receptor, presumably involved in the formation of both homodimers and heterodimers with other CD300 family members. Site-directed mutagenesis revealed residues glutamic acid 28 and glutamine 29 in cluster 5 to be necessary for the formation of CD300b complexes. Surprisingly, the disruption of cluster 2 and 4 reconstituted the binding capability lost by the mutation of residues glutamic acid 28 to alanine, glutamine 29 to alanine (E28A-Q29G). We identified a missense mutation arginine 33 to glutamine (R33Q) in CD300f by direct sequencing of exon 2 in peripheral blood samples from 50 patients with multiple sclerosis (MS). Levels of expression of CD300f were almost undetectable on monocytes from the patient bearing the R33Q mutation compared with healthy individuals. Whereas R33Q mutation had no effect in the formation of CD300f complexes, the inhibition of protein synthesis with cycloheximide indicated that CD300f R33Q is less stable than native CD300f. Finally, we report that the levels of expression of CD300f on the surface of classical and intermediate monocytes from MS patients are significantly lower when compared to the same cell populations in healthy individuals.
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52
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Vergadi E, Ieronymaki E, Lyroni K, Vaporidi K, Tsatsanis C. Akt Signaling Pathway in Macrophage Activation and M1/M2 Polarization. THE JOURNAL OF IMMUNOLOGY 2017; 198:1006-1014. [PMID: 28115590 DOI: 10.4049/jimmunol.1601515] [Citation(s) in RCA: 654] [Impact Index Per Article: 93.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 09/26/2016] [Indexed: 01/05/2023]
Abstract
Macrophages become activated initiating innate immune responses. Depending on the signals, macrophages obtain an array of activation phenotypes, described by the broad terms of M1 or M2 phenotype. The PI3K/Akt/mTOR pathway mediates signals from multiple receptors including insulin receptors, pathogen-associated molecular pattern receptors, cytokine receptors, adipokine receptors, and hormones. As a result, the Akt pathway converges inflammatory and metabolic signals to regulate macrophage responses modulating their activation phenotype. Akt is a family of three serine-threonine kinases, Akt1, Akt2, and Akt3. Generation of mice lacking individual Akt, PI3K, or mTOR isoforms and utilization of RNA interference technology have revealed that Akt signaling pathway components have distinct and isoform-specific roles in macrophage biology and inflammatory disease regulation, by controlling inflammatory cytokines, miRNAs, and functions including phagocytosis, autophagy, and cell metabolism. Herein, we review the current knowledge on the role of the Akt signaling pathway in macrophages, focusing on M1/M2 polarization and highlighting Akt isoform-specific functions.
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Affiliation(s)
- Eleni Vergadi
- Laboratory of Clinical Chemistry, School of Medicine, University of Crete, Heraklion 71003, Greece; and.,Laboratory of Intensive Care Medicine, School of Medicine, University of Crete, Heraklion 71003, Greece
| | - Eleftheria Ieronymaki
- Laboratory of Clinical Chemistry, School of Medicine, University of Crete, Heraklion 71003, Greece; and
| | - Konstantina Lyroni
- Laboratory of Clinical Chemistry, School of Medicine, University of Crete, Heraklion 71003, Greece; and
| | - Katerina Vaporidi
- Laboratory of Intensive Care Medicine, School of Medicine, University of Crete, Heraklion 71003, Greece
| | - Christos Tsatsanis
- Laboratory of Clinical Chemistry, School of Medicine, University of Crete, Heraklion 71003, Greece; and
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Abstract
The engulfment of apoptotic cells by phagocytes, a process referred to as efferocytosis, is essential for maintenance of normal tissue homeostasis and a prerequisite for the resolution of inflammation. Neutrophils are the predominant circulating white blood cell in humans, and contain an arsenal of toxic substances that kill and degrade microbes. Neutrophils are short-lived and spontaneously die by apoptosis. This review will highlight how the engulfment of apoptotic neutrophils by human phagocytes occurs, how heterogeneity of phagocyte populations influences efferocytosis signaling, and downstream consequences of efferocytosis. The efferocytosis of apoptotic neutrophils by macrophages promotes anti-inflammatory signaling, prevents neutrophil lysis, and dampens immune responses. Given the immunomodulatory properties of efferocytosis, understanding pathways that regulate and enhance efferocytosis could be harnessed to combat infection and chronic inflammatory conditions.
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Affiliation(s)
- Mallary C Greenlee-Wacker
- Inflammation Program, Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine University of Iowa, Veterans Administration Medical Center, Iowa City, IA, USA
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54
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Engulfment signals and the phagocytic machinery for apoptotic cell clearance. Exp Mol Med 2017; 49:e331. [PMID: 28496201 PMCID: PMC5454446 DOI: 10.1038/emm.2017.52] [Citation(s) in RCA: 105] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 12/15/2016] [Indexed: 02/07/2023] Open
Abstract
The clearance of apoptotic cells is an essential process for tissue homeostasis. To this end, cells undergoing apoptosis must display engulfment signals, such as ‘find-me' and ‘eat-me' signals. Engulfment signals are recognized by multiple types of phagocytic machinery in phagocytes, leading to prompt clearance of apoptotic cells. In addition, apoptotic cells and phagocytes release tolerogenic signals to reduce immune responses against apoptotic cell-derived self-antigens. Here we discuss recent advances in our knowledge of engulfment signals, the phagocytic machinery and the signal transduction pathways for apoptotic cell engulfment.
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55
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Zent CS, Elliott MR. Maxed out macs: physiologic cell clearance as a function of macrophage phagocytic capacity. FEBS J 2017; 284:1021-1039. [PMID: 27863012 PMCID: PMC5378628 DOI: 10.1111/febs.13961] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 11/01/2016] [Accepted: 11/10/2016] [Indexed: 12/28/2022]
Abstract
The phagocytic clearance of host cells is important for eliminating dying cells and for the therapeutic clearance of antibody-targeted cells. As ubiquitous, motile and highly phagocytic immune cells, macrophages are principal players in the phagocytic removal of host cells throughout the body. In recent years, great strides have been made in identifying the molecular mechanisms that control the recognition and phagocytosis of cells by macrophages. However, much less is known about the physical and metabolic constraints that govern the amount of cellular material macrophages can ingest and how these limitations affect the overall efficiency of host cell clearance in health and disease. In this review we will discuss, in the contexts of apoptotic cells and antibody-targeted malignant cells, how physical and metabolic factors associated with the internalization of host cells are relayed to the phagocytic machinery and how these signals can impact the overall efficiency of cell clearance. We also discuss how this information can be leveraged to increase cell clearance for beneficial therapeutic outcomes.
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Affiliation(s)
- Clive S. Zent
- Wilmot Cancer Institute, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Michael R. Elliott
- Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
- David H. Smith Center for Vaccine Biology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
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56
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Klei TRL, Meinderts SM, van den Berg TK, van Bruggen R. From the Cradle to the Grave: The Role of Macrophages in Erythropoiesis and Erythrophagocytosis. Front Immunol 2017; 8:73. [PMID: 28210260 PMCID: PMC5288342 DOI: 10.3389/fimmu.2017.00073] [Citation(s) in RCA: 154] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 01/17/2017] [Indexed: 12/13/2022] Open
Abstract
Erythropoiesis is a highly regulated process where sequential events ensure the proper differentiation of hematopoietic stem cells into, ultimately, red blood cells (RBCs). Macrophages in the bone marrow play an important role in hematopoiesis by providing signals that induce differentiation and proliferation of the earliest committed erythroid progenitors. Subsequent differentiation toward the erythroblast stage is accompanied by the formation of so-called erythroblastic islands where a central macrophage provides further cues to induce erythroblast differentiation, expansion, and hemoglobinization. Finally, erythroblasts extrude their nuclei that are phagocytosed by macrophages whereas the reticulocytes are released into the circulation. While in circulation, RBCs slowly accumulate damage that is repaired by macrophages of the spleen. Finally, after 120 days of circulation, senescent RBCs are removed from the circulation by splenic and liver macrophages. Macrophages are thus important for RBCs throughout their lifespan. Finally, in a range of diseases, the delicate interplay between macrophages and both developing and mature RBCs is disturbed. Here, we review the current knowledge on the contribution of macrophages to erythropoiesis and erythrophagocytosis in health and disease.
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Affiliation(s)
- Thomas R L Klei
- Department of Blood Cell Research, Sanquin Research and Landsteiner Laboratory, University of Amsterdam , Amsterdam , Netherlands
| | - Sanne M Meinderts
- Department of Blood Cell Research, Sanquin Research and Landsteiner Laboratory, University of Amsterdam , Amsterdam , Netherlands
| | - Timo K van den Berg
- Department of Blood Cell Research, Sanquin Research and Landsteiner Laboratory, University of Amsterdam , Amsterdam , Netherlands
| | - Robin van Bruggen
- Department of Blood Cell Research, Sanquin Research and Landsteiner Laboratory, University of Amsterdam , Amsterdam , Netherlands
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57
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Whitlock JM, Hartzell HC. Anoctamins/TMEM16 Proteins: Chloride Channels Flirting with Lipids and Extracellular Vesicles. Annu Rev Physiol 2016; 79:119-143. [PMID: 27860832 DOI: 10.1146/annurev-physiol-022516-034031] [Citation(s) in RCA: 109] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Anoctamin (ANO)/TMEM16 proteins exhibit diverse functions in cells throughout the body and are implicated in several human diseases. Although the founding members ANO1 (TMEM16A) and ANO2 (TMEM16B) are Ca2+-activated Cl- channels, most ANO paralogs are Ca2+-dependent phospholipid scramblases that serve as channels facilitating the movement (scrambling) of phospholipids between leaflets of the membrane bilayer. Phospholipid scrambling significantly alters the physical properties of the membrane and its landscape and has vast downstream signaling consequences. In particular, phosphatidylserine exposed on the external leaflet of the plasma membrane functions as a ligand for receptors vital for cell-cell communication. A major consequence of Ca2+-dependent scrambling is the release of extracellular vesicles that function as intercellular messengers by delivering signaling proteins and noncoding RNAs to alter target cell function. We discuss the physiological implications of Ca2+-dependent phospholipid scrambling, the extracellular vesicles associated with this activity, and the roles of ANOs in these processes.
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Affiliation(s)
- Jarred M Whitlock
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322;
| | - H Criss Hartzell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322;
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58
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Yamada M, Fujino N, Ichinose M. Inflammatory responses in the initiation of lung repair and regeneration: their role in stimulating lung resident stem cells. Inflamm Regen 2016; 36:15. [PMID: 29259688 PMCID: PMC5725654 DOI: 10.1186/s41232-016-0020-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 06/10/2016] [Indexed: 12/12/2022] Open
Abstract
The lungs are the primary organs for respiration, the process by which carbon dioxide and oxygen are exchanged. The alveolus, which is the site of gas exchange in the lungs, consists of multiple cell types including alveolar epithelial cells, lung capillary endothelial cells and fibroblasts. Because of their complexity, lung parenchymal cells including epithelial lineage have been thought to have a lower rate of cellular turnover in adult lung. However, accumulating observations suggest that the turnover of parenchymal cells in adult lungs is essential for maintaining homeostasis during the steady state as well as for the repair and regeneration after lung injury. After lung injury by harmful pathogens, inflammation occurs to protect the host. Although excessive inflammation damages lung tissue, inflammatory cells are essential for regeneration because they remove harmful pathogens as well as debris derived from apoptotic and necrotic cells. In addition, subsets of inflammatory cells, especially phagocytic monocytes, produce cytokines and growth factors to resolve inflammation and promote tissue regeneration by stimulating tissue-resident stem cells. Recent advances in the biology of lung-resident stem cells, especially those addressing epithelial lineage, have revealed that there are several cellular populations capable of self-renewal that can differentiate into airway and/or alveolar epithelial cells. A part of these populations does not exist in the steady state but emerges after lung injury, suggesting that signals induced by inflammation may play an important role in initiating the proliferation and differentiation of lung stem or progenitor cells. Understanding the interaction between inflammatory responses and tissue-resident stem cells would help elucidate the pathogenesis of inflammatory lung diseases and promote the discovery of new therapeutic targets.
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Affiliation(s)
- Mitsuhiro Yamada
- Department of Respiratory Medicine, Graduate School of Medicine, Tohoku University, 1-1 Seiryo-machi, Aoba-ku, Sendai, 980-8574 Japan
| | - Naoya Fujino
- Department of Respiratory Medicine, Graduate School of Medicine, Tohoku University, 1-1 Seiryo-machi, Aoba-ku, Sendai, 980-8574 Japan
| | - Masakazu Ichinose
- Department of Respiratory Medicine, Graduate School of Medicine, Tohoku University, 1-1 Seiryo-machi, Aoba-ku, Sendai, 980-8574 Japan
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59
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Hao S, Han X, Wang D, Yang Y, Li Q, Li X, Qiu C. Critical role of CCL22/CCR4 axis in the maintenance of immune homeostasis during apoptotic cell clearance by splenic CD8α(+) CD103(+) dendritic cells. Immunology 2016; 148:174-86. [PMID: 26868141 PMCID: PMC4863574 DOI: 10.1111/imm.12596] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Revised: 02/07/2016] [Accepted: 02/08/2016] [Indexed: 12/19/2022] Open
Abstract
Macrophages and dendritic cells (DCs) in murine spleen are essential for the maintenance of immune homeostasis by elimination of blood-borne foreign particles and organisms. It has been reported that splenic DCs, especially CD8α(+) CD103(+) DCs, are responsible for tolerance to apoptosis-associated antigens. However, the molecular mechanism by which these DCs maintain immune homeostasis by blood-borne apoptotic cell clearance remains elusive. Here, we found that the CCL22/CCR4 axis played a critical role in the maintenance of immune homeostasis during apoptotic cell clearance by splenic CD8α(+) CD103(+) DCs. The present results revealed that systemic administration of apoptotic cells rapidly induced a large number of CCL22 and CCR4(+) regulatory T (Treg) cells in the spleen of C57BL/6J mice. Further study demonstrated that CD8α(+) CD103(+) DCs dominantly produce much higher CCL22 than CD8α(+) CD103(-) DCs. Moreover, the transient deletion of CD8α(+) CD103(+) DCs caused a decrease in CCL22 levels together with CCR4(+) Treg cell percentage. Subsequently, the levels of some pro-inflammatory cytokines, such as interleukin-17 and interferon-γ in the spleen with the absence of CD8α(+) CD103(+) DCs increased in response to the administration of apoptotic cells. Hence, intravenous injection of apoptotic cells induced a subsequent increase in CCL22 expression and CCR4(+) Treg cells, which contribute to the maintenance of immune homeostasis at least partially by splenic CD8α(+) CD103(+) DCs.
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Affiliation(s)
- Shengyu Hao
- Department of Cell BiologyShandong University School of MedicineJinanShandongChina
| | - Xiaolei Han
- Department of Cell BiologyShandong University School of MedicineJinanShandongChina
| | - Dan Wang
- Department of Cell BiologyShandong University School of MedicineJinanShandongChina
| | - Yang Yang
- Department of Cell BiologyShandong University School of MedicineJinanShandongChina
| | - Qiuting Li
- Department of Cell BiologyShandong University School of MedicineJinanShandongChina
| | - Xiangzhi Li
- Department of Cell BiologyShandong University School of MedicineJinanShandongChina
| | - Chun‐Hong Qiu
- Department of Cell BiologyShandong University School of MedicineJinanShandongChina
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60
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Voss OH, Murakami Y, Pena MY, Lee HN, Tian L, Margulies DH, Street JM, Yuen PST, Qi CF, Krzewski K, Coligan JE. Lipopolysaccharide-Induced CD300b Receptor Binding to Toll-like Receptor 4 Alters Signaling to Drive Cytokine Responses that Enhance Septic Shock. Immunity 2016; 44:1365-78. [PMID: 27261276 DOI: 10.1016/j.immuni.2016.05.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Revised: 02/03/2016] [Accepted: 02/20/2016] [Indexed: 12/12/2022]
Abstract
Receptor CD300b is implicated in regulating the immune response to bacterial infection by an unknown mechanism. Here, we identified CD300b as a lipopolysaccharide (LPS)-binding receptor and determined the mechanism underlying CD300b augmentation of septic shock. In vivo depletion and adoptive transfer studies identified CD300b-expressing macrophages as the key cell type augmenting sepsis. We showed that CD300b, and its adaptor DAP12, associated with Toll-like receptor 4 (TLR4) upon LPS binding, thereby enhancing TLR4-adaptor MyD88- and TRIF-dependent signaling that resulted in an elevated pro-inflammatory cytokine storm. LPS engagement of the CD300b-TLR4 complex led to the recruitment and activation of spleen tyrosine kinase (Syk) and phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K). This resulted in an inhibition of the ERK1/2 protein kinase- and NF-κB transcription factor-mediated signaling pathways, which subsequently led to a reduced interleukin-10 (IL-10) production. Collectively, our data describe a mechanism of TLR4 signaling regulated by CD300b in myeloid cells in response to LPS.
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Affiliation(s)
- Oliver H Voss
- Receptor Cell Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD 20852, USA
| | - Yousuke Murakami
- Receptor Cell Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD 20852, USA
| | - Mirna Y Pena
- Receptor Cell Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD 20852, USA
| | - Ha-Na Lee
- Receptor Cell Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD 20852, USA
| | - Linjie Tian
- Receptor Cell Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD 20852, USA
| | - David H Margulies
- Molecular Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20814, USA
| | - Jonathan M Street
- Renal Diagnostics and Therapeutics Unit, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20814, USA
| | - Peter S T Yuen
- Renal Diagnostics and Therapeutics Unit, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20814, USA
| | - Chen-Feng Qi
- Pathology Core, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD 20852, USA
| | - Konrad Krzewski
- Receptor Cell Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD 20852, USA
| | - John E Coligan
- Receptor Cell Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD 20852, USA.
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61
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Bevers EM, Williamson PL. Getting to the Outer Leaflet: Physiology of Phosphatidylserine Exposure at the Plasma Membrane. Physiol Rev 2016; 96:605-45. [PMID: 26936867 DOI: 10.1152/physrev.00020.2015] [Citation(s) in RCA: 293] [Impact Index Per Article: 36.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Phosphatidylserine (PS) is a major component of membrane bilayers whose change in distribution between inner and outer leaflets is an important physiological signal. Normally, members of the type IV P-type ATPases spend metabolic energy to create an asymmetric distribution of phospholipids between the two leaflets, with PS confined to the cytoplasmic membrane leaflet. On occasion, membrane enzymes, known as scramblases, are activated to facilitate transbilayer migration of lipids, including PS. Recently, two proteins required for such randomization have been identified: TMEM16F, a scramblase regulated by elevated intracellular Ca(2+), and XKR8, a caspase-sensitive protein required for PS exposure in apoptotic cells. Once exposed at the cell surface, PS regulates biochemical reactions involved in blood coagulation, and bone mineralization, and also regulates a variety of cell-cell interactions. Exposed on the surface of apoptotic cells, PS controls their recognition and engulfment by other cells. This process is exploited by parasites to invade their host, and in specialized form is used to maintain photoreceptors in the eye and modify synaptic connections in the brain. This review discusses what is known about the mechanism of PS exposure at the surface of the plasma membrane of cells, how actors in the extracellular milieu sense surface exposed PS, and how this recognition is translated to downstream consequences of PS exposure.
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Affiliation(s)
- Edouard M Bevers
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands; and Department of Biology, Amherst College, Amherst, Massachusetts
| | - Patrick L Williamson
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands; and Department of Biology, Amherst College, Amherst, Massachusetts
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62
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Grabiec AM, Hussell T. The role of airway macrophages in apoptotic cell clearance following acute and chronic lung inflammation. Semin Immunopathol 2016; 38:409-23. [PMID: 26957481 PMCID: PMC4896990 DOI: 10.1007/s00281-016-0555-3] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 01/29/2016] [Indexed: 12/19/2022]
Abstract
Acute and chronic inflammatory responses in the lung are associated with the accumulation of large quantities of immune and structural cells undergoing apoptosis, which need to be engulfed by phagocytes in a process called ‘efferocytosis’. Apoptotic cell recognition and removal from the lung is mediated predominantly by airway macrophages, though immature dendritic cells and non-professional phagocytes, such as epithelial cells and mesenchymal cells, can also display this function. Efficient clearance of apoptotic cells from the airways is essential for successful resolution of inflammation and the return to lung homeostasis. Disruption of this process leads to secondary necrosis of accumulating apoptotic cells, release of necrotic cell debris and subsequent uncontrolled inflammatory activation of the innate immune system by the released ‘damage associated molecular patterns’ (DAMPS). To control the duration of the immune response and prevent autoimmune reactions, anti-inflammatory signalling cascades are initiated in the phagocyte upon apoptotic cell uptake, mediated by a range of receptors that recognise specific phospholipids or proteins externalised on, or secreted by, the apoptotic cell. However, prolonged activation of apoptotic cell recognition receptors, such as the family of receptor tyrosine kinases Tyro3, Axl and MerTK (TAM), may delay or prevent inflammatory responses to subsequent infections. In this review, we will discuss recent advances in our understanding of the mechanism controlling apoptotic cell recognition and removal from the lung in homeostasis and during inflammation, the contribution of defective efferocytosis to chronic inflammatory lung diseases, such as chronic obstructive pulmonary disease, asthma and cystic fibrosis, and implications of the signals triggered by apoptotic cells in the susceptibility to pulmonary microbial infections.
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Affiliation(s)
- Aleksander M Grabiec
- Manchester Collaborative Centre for Inflammation Research, Core Technology Facility, The University of Manchester, 46 Grafton Street, M13 9NT, Manchester, UK
| | - Tracy Hussell
- Manchester Collaborative Centre for Inflammation Research, Core Technology Facility, The University of Manchester, 46 Grafton Street, M13 9NT, Manchester, UK.
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63
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Tian L, Choi SC, Lee HN, Murakami Y, Qi CF, Sengottuvelu M, Voss O, Krzewski K, Coligan JE. Enhanced efferocytosis by dendritic cells underlies memory T-cell expansion and susceptibility to autoimmune disease in CD300f-deficient mice. Cell Death Differ 2016; 23:1086-96. [PMID: 26768664 DOI: 10.1038/cdd.2015.161] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Revised: 10/20/2015] [Accepted: 11/19/2015] [Indexed: 12/27/2022] Open
Abstract
Homeostasis requires the immunologically silent clearance of apoptotic cells before they become pro-inflammatory necrotic cells. CD300f (CLM-1) is a phosphatidylserine receptor known to positively regulate efferocytosis by macrophages, and CD300f gene-deficient mice are predisposed to develop a lupus-like disease. Here we show that, in contrast to CD300f function in macrophages, its expression inhibits efferocytosis by DC, and its deficiency leads to enhanced antigen processing and T-cell priming by these DC. The consequences are the expansion of memory T cells and increased ANA levels in aged CD300f-deficient mice, which predispose CD300f-deficient mice to develop an overt autoimmune disease when exposed to an overload of apoptotic cells, or an exacerbated autoimmunity when combined with FcγRIIB deficiency. Thus, our data demonstrates that CD300f helps to maintain immune homeostasis by promoting macrophage clearance of self-antigens, while conversely inhibiting DC uptake and presentation of self-antigens.
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Affiliation(s)
- L Tian
- Receptor Cell Biology Section, Laboratory of Immunogenetics, NIAID, NIH, Rockville, MD, USA
| | - S-C Choi
- Receptor Cell Biology Section, Laboratory of Immunogenetics, NIAID, NIH, Rockville, MD, USA
| | - H-N Lee
- Receptor Cell Biology Section, Laboratory of Immunogenetics, NIAID, NIH, Rockville, MD, USA
| | - Y Murakami
- Receptor Cell Biology Section, Laboratory of Immunogenetics, NIAID, NIH, Rockville, MD, USA
| | - C-F Qi
- Pathology Core, Laboratory of Immunogenetics, NIAID, NIH, Rockville, MD, USA
| | - M Sengottuvelu
- Receptor Cell Biology Section, Laboratory of Immunogenetics, NIAID, NIH, Rockville, MD, USA
| | - O Voss
- Receptor Cell Biology Section, Laboratory of Immunogenetics, NIAID, NIH, Rockville, MD, USA
| | - K Krzewski
- Receptor Cell Biology Section, Laboratory of Immunogenetics, NIAID, NIH, Rockville, MD, USA
| | - J E Coligan
- Receptor Cell Biology Section, Laboratory of Immunogenetics, NIAID, NIH, Rockville, MD, USA
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64
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The immunobiology of Campylobacter jejuni: Innate immunity and autoimmune diseases. Immunobiology 2015; 221:535-43. [PMID: 26709064 DOI: 10.1016/j.imbio.2015.12.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 12/05/2015] [Accepted: 12/06/2015] [Indexed: 12/26/2022]
Abstract
The Gram-negative bacterium Campylobacter jejuni causes gastroenteritis and Guillain-Barré syndrome in humans. Recent advances in the immunobiology of C. jejuni have been made. This review summarizes C. jejuni-binding innate receptors and highlights the role of innate immunity in autoimmune diseases. This human pathogen produces a variety of glycoconjugates, including human ganglioside-like determinants and multiple activators of Toll-like receptors (TLRs). Furthermore, C. jejuni targets MyD88, NLRP3 inflammasome, TIR-domain-containing adapter-inducing interferon-β (TRIF), sialic acid-binding immunoglobulin-like lectins (Siglecs), macrophage galactose-type lectin (MGL), and immunoglobulin-like receptors (TREM2, LMIR5/CD300b). The roles of these innate receptors and signaling molecules have been extensively studied. MyD88-mediated TLR activation or inflammasome-dependent IL-1β secretion is essential for autoimmune induction. TRIF mediates the production of type I interferons that promote humoral immune responses and immunoglobulin class-switching. Siglec-1 and Siglec-7 interact directly with gangliosides. Siglec-1 activation enhances phagocytosis and inflammatory responses. MGL internalizes GalNAc-containing glycoconjugates. TREM2 is well-known for its role in phagocytosis. LMIR5 recognizes C. jejuni components and endogenous sulfoglycolipids. Several lines of evidence from animal models of autoimmune diseases suggest that simultaneous activation of innate immunity in the presence of autoreactive lymphocytes or antigen mimicry may link C. jejuni to immunopathology.
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65
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Rysavy NM, Shimoda LMN, Dixon AM, Speck M, Stokes AJ, Turner H, Umemoto EY. Beyond apoptosis: the mechanism and function of phosphatidylserine asymmetry in the membrane of activating mast cells. BIOARCHITECTURE 2015; 4:127-37. [PMID: 25759911 DOI: 10.1080/19490992.2014.995516] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Loss of plasma membrane asymmetry is a hallmark of apoptosis, but lipid bilayer asymmetry and loss of asymmetry can contribute to numerous cellular functions and responses that are independent of programmed cell death. Exofacial exposure of phosphatidylserine occurs in lymphocytes and mast cells after antigenic stimulation and in the absence of apoptosis, suggesting that there is a functional requirement for phosphatidylserine exposure in immunocytes. In this review we examine current ideas as to the nature of this functional role in mast cell activation. Mechanistically, there is controversy as to the candidate proteins responsible for phosphatidylserine translocation from the internal to external leaflet, and here we review the candidacies of mast cell PLSCR1 and TMEM16F. Finally we examine the potential relationship between functionally important mast cell membrane perturbations and phosphatidylserine exposure during activation.
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Key Words
- ABCA, ABC binding cassette family A
- CRAC, calcium release activated channel
- GPMV, giant plasma membrane vesicle
- ITIM, immunoreceptor tyrosine based inhibitory motif
- PLA2, phospholipase A2
- PLSCR, phospholipid scramblase
- PMA, phorbol 12,13-myristate acetate
- RBL, rat basophilic leukemia
- RFU, relative fluorescence units
- ROI, region of interest
- TMEM, transmembrane protein
- TMEM16F
- WGA, wheat germ agglutinin
- mast cells
- membrane lipids
- phosphatidylserine
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Affiliation(s)
- Noel M Rysavy
- a Laboratory of Immunology and Signal Transduction ; Department of Biology; Chaminade University ; Honolulu , Hawai'i USA
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Segawa K, Nagata S. An Apoptotic 'Eat Me' Signal: Phosphatidylserine Exposure. Trends Cell Biol 2015; 25:639-650. [PMID: 26437594 DOI: 10.1016/j.tcb.2015.08.003] [Citation(s) in RCA: 481] [Impact Index Per Article: 53.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 08/08/2015] [Accepted: 08/17/2015] [Indexed: 12/19/2022]
Abstract
Apoptosis and the clearance of apoptotic cells are essential processes in animal development and homeostasis. For apoptotic cells to be cleared, they must display an 'eat me' signal, most likely phosphatidylserine (PtdSer) exposure, which prompts phagocytes to engulf the cells. PtdSer, which is recognized by several different systems, is normally confined to the cytoplasmic leaflet of the plasma membrane by a 'flippase'; apoptosis activates a 'scramblase' that quickly exposes PtdSer on the cell surface. The molecules that flip and scramble phospholipids at the plasma membrane have recently been identified. Here we discuss recent findings regarding the molecular mechanisms of apoptotic PtdSer exposure and the clearance of apoptotic cells.
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Affiliation(s)
- Katsumori Segawa
- Laboratory of Biochemistry and Immunology, WPI Immunology Frontier Research Center, Osaka University, 3-1 Yamada-oka, Suita 565-0871, Japan
| | - Shigekazu Nagata
- Laboratory of Biochemistry and Immunology, WPI Immunology Frontier Research Center, Osaka University, 3-1 Yamada-oka, Suita 565-0871, Japan.
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67
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Voss OH, Tian L, Murakami Y, Coligan JE, Krzewski K. Emerging role of CD300 receptors in regulating myeloid cell efferocytosis. Mol Cell Oncol 2015; 2:e964625. [PMID: 27308512 PMCID: PMC4905414 DOI: 10.4161/23723548.2014.964625] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 08/07/2014] [Accepted: 08/12/2014] [Indexed: 11/19/2022]
Abstract
Engulfment of apoptotic cells is predominantly executed by phagocytes via the recognition of “eat me” signals like phosphatidylserine (PS). Various PS-specific receptors exist on phagocytes, including Tyro3, Axl, and MerTK receptor tyrosine kinases (TAMs), T-cell immunoglobulin and mucin domain containing 1 and 4 (TIM1/4), and the newly identified CD300 family. The aim of the present auto-commentary is to highlight recent findings regarding the Cd300lf and Cd300lb receptors and their emerging roles in the development of autoimmune disease.
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Affiliation(s)
- Oliver H Voss
- Receptor Cell Biology Section; Laboratory of Immunogenetics; National Institute of Allergy and Infectious Diseases; National Institutes of Health; Rockville, MD, USA
| | - Linjie Tian
- Receptor Cell Biology Section; Laboratory of Immunogenetics; National Institute of Allergy and Infectious Diseases; National Institutes of Health; Rockville, MD, USA
| | - Yousuke Murakami
- Receptor Cell Biology Section; Laboratory of Immunogenetics; National Institute of Allergy and Infectious Diseases; National Institutes of Health; Rockville, MD, USA
| | - John E Coligan
- Receptor Cell Biology Section; Laboratory of Immunogenetics; National Institute of Allergy and Infectious Diseases; National Institutes of Health; Rockville, MD, USA
| | - Konrad Krzewski
- Receptor Cell Biology Section; Laboratory of Immunogenetics; National Institute of Allergy and Infectious Diseases; National Institutes of Health; Rockville, MD, USA
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Evidence for TLR4 and FcRγ-CARD9 activation by cholera toxin B subunit and its direct bindings to TREM2 and LMIR5 receptors. Mol Immunol 2015; 66:463-71. [PMID: 26021803 DOI: 10.1016/j.molimm.2015.05.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2015] [Revised: 04/08/2015] [Accepted: 05/10/2015] [Indexed: 11/23/2022]
Abstract
Cholera toxin (CTX) is a virulent factor of Vibrio cholerae that causes life-threatening diarrheal disease. Its non-toxic subunit CTB has been extensively studied for vaccine delivery. In immune cells, CTB induces a number of signaling molecules related to cellular activation and cytokine production. The mechanisms by which CTB exerts its immunological effects are not understood. We report here the immunological targets of CTB. The unexpected finding that GM1 ganglioside inhibited NF-κB activation in human monocytes stimulated with CTX and agonists of Toll-like receptors (TLR) suggests the possibility of CTX-TLR interaction. Indeed, CTX-induced IL-6 production was substantially reduced in MyD88(-/-) or TLR4(-/-) macrophages. Ectopic expression of TLR4 was required for CTX-induced NF-κB activation in HEK 293 cells. Furthermore, the inflammatory capacity of CTB was lost in the absence of TLR4, adaptor protein FcRγ, or its downstream signaling molecule CARD9. Attempts have been made to identify CTB-binding targets from various C-type lectin and immunoglobulin-like receptors. CTB targeted not only GM1 and TLR4 but also TREM2 and LMIR5/CD300b. CTB-TREM2 interaction initiated signal transduction through adaptor protein DAP12. The binding of CTB inhibited LMIR5 activation induced by its endogenous ligand 3-O-sulfo-β-d-galactosylceramide C24:1. In summary, CTB targets TLR4, FcRγ-CARD9, TREM2, and LMIR5. These findings provide new insights into the immunobiology of cholera toxin.
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Fang XY, Xu WD, Pan HF, Leng RX, Ye DQ. Novel insights into Tim-4 function in autoimmune diseases. Autoimmunity 2014; 48:189-95. [DOI: 10.3109/08916934.2014.983266] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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