scholarly journals RAB-35 aids apoptotic cell clearance by regulating cell corpse recognition and phagosome maturation

2018 ◽  
Author(s):  
Ryan C. Haley ◽  
Ying Wang ◽  
Zheng Zhou
Keyword(s):  
Apoptotic Cell ◽  
Small Gtpases ◽  
Small Gtpase ◽  
Apoptotic Cells ◽  
Rab Gtpases ◽  
Phagosome Maturation ◽  
Apoptotic Cell Clearance ◽  
Cell Clearance ◽  
Early Endosomes ◽  
Cell Corpse

AbstractIn metazoans, apoptotic cells are swiftly engulfed by phagocytes and degraded inside phagosomes. Multiple small GTPases in the Rab family are known to function in phagosome maturation by regulating vesicle trafficking. We discovered rab-35 as a new gene important for apoptotic cell clearance using an RNAi screen targeting putative Rab GTPases in Caenorhabditis elegans. We further identified TBC-10 as a putative GTPase-activating protein (GAP), and FLCN-1 and RME-4 as two putative Guanine Nucleotide Exchange Factors (GEFs), for RAB-35. RAB-35 function was found to be required for the incorporation of early endosomes to phagosomes and for the timely degradation of apoptotic cell corpses. More specifically, RAB-35 facilitates the switch of phagosomal membrane phosphatidylinositol species from PtdIns(4,5)P2 to PtdIns(3)P and promotes the recruitment of the small GTPase RAB-5 to phagosomal surfaces, processes that are essential for phagosome maturation. Interestingly, we observed that CED-1 performs these same functions, and to a much larger extent than RAB-35. Remarkably, in addition to cell corpse degradation, RAB-35 also facilitates the recognition of cell corpses independently of the CED-1 and CED-5 pathways. RAB-35 localizes to extending pseudopods and is further enriched on nascent phagosomes, consistent with its dual roles in regulating cell corpse-recognition and phagosome maturation. Epistasis analyses indicate that rab-35 represents a novel third genetic pathway that acts in parallel to both of the canonical ced-1/6/7 and ced-2/5/10/12 engulfment pathways. We propose that RAB-35 acts as a robustness factor, leading a pathway that aids the canonical pathways for the engulfment and degradation of apoptotic cells.

scholarly journals GOP-1 promotes apoptotic cell degradation by activating the small GTPase Rab2 in C. elegans

2017 ◽  
Vol 216 (6) ◽  
pp. 1775-1794 ◽  
Author(s):  
Jianhua Yin ◽  
Yaling Huang ◽  
Pengfei Guo ◽  
Siqi Hu ◽  
Sawako Yoshina ◽  
...  
Keyword(s):  
Apoptotic Cell ◽  
Small Gtpase ◽  
Dense Core Vesicle ◽  
Rab Gtpases ◽  
Membrane Recruitment ◽  
C Elegans ◽  
Apoptotic Cell Clearance ◽  
Cell Clearance ◽  
Cell Corpse

Apoptotic cells generated by programmed cell death are engulfed by phagocytes and enclosed within plasma membrane–derived phagosomes. Maturation of phagosomes involves a series of membrane-remodeling events that are governed by the sequential actions of Rab GTPases and lead to formation of phagolysosomes, where cell corpses are degraded. Here we identified gop-1 as a novel regulator of apoptotic cell clearance in Caenorhabditis elegans. Loss of gop-1 affects phagosome maturation through the RAB-5–positive stage, causing defects in phagosome acidification and phagolysosome formation, phenotypes identical to and unaffected by loss of unc-108, the C. elegans Rab2. GOP-1 transiently associates with cell corpse–containing phagosomes, and loss of its function abrogates phagosomal association of UNC-108. GOP-1 interacts with GDP-bound and nucleotide-free UNC-108/Rab2, disrupts GDI-UNC-108 complexes, and promotes activation and membrane recruitment of UNC-108/Rab2 in vitro. Loss of gop-1 also abolishes association of UNC-108 with endosomes, causing defects in endosome and dense core vesicle maturation. Thus, GOP-1 is an activator of UNC-108/Rab2 in multiple processes.

scholarly journals Chemokines as phosphatidylserine-bound ‘find-me’ signals in apoptotic cell clearance

2020 ◽  
Author(s):  
Sergio M. Pontejo ◽  
Philip M. Murphy
Keyword(s):  
Extracellular Vesicles ◽  
Chemokine Receptors ◽  
Apoptotic Cell ◽  
Apoptotic Cells ◽  
Anionic Phospholipid ◽  
Apoptotic Cell Clearance ◽  
Cell Clearance ◽  
Cell Plasma ◽  
Signal Activity ◽  
Dying Cells

AbstractChemokines are positively charged cytokines that attract leukocytes by binding to anionic glycosaminoglycans (GAGs) on endothelial cells for efficient presentation to leukocyte G protein-coupled receptors (GPCRs). The atypical chemokine CXCL16 has been reported to also bind the anionic phospholipid phosphatidylserine (PS), but the biological relevance of this interaction remains poorly understood. Here we demonstrate that PS binding is in fact a widely shared property of chemokine superfamily members that, like GAG binding, induces chemokine oligomerization. PS is an essential phospholipid of the inner leaflet of the healthy cell plasma membrane but it is exposed in apoptotic cells to act as an ‘eat-me’ signal that promotes engulfment of dying cells by phagocytes. We found that chemokines can bind PS in pure form as well as in the context of liposomes and on the surface of apoptotic cells and extracellular vesicles released by apoptotic cells, which are known to act as ‘find-me’ signals that chemoattract phagocytes during apoptotic cell clearance. Importantly, we show that GAGs are severely depleted from the surface of apoptotic cells and that extracellular vesicles extracted from apoptotic mouse thymus bind endogenous thymic chemokines and activate cognate chemokine receptors. Together these results indicate that chemokines tethered to surface-exposed PS may be responsible for the chemotactic and find-me signal activity previously attributed to extracellular vesicles, and that PS may substitute for GAGs as the anionic scaffold that regulates chemokine oligomerization and presentation to GPCRs on the GAG-deficient membranes of apoptotic cells and extracellular vesicles. Here, we present a new mechanism by which extracellular vesicles, currently recognized as essential agents for intercellular communication in homeostasis and disease, can transport signaling cytokines.

scholarly journals Overexposure to apoptosis via disrupted glial specification perturbs Drosophila macrophage function and reveals roles of the CNS during injury

2020 ◽  
Author(s):  
Emma Louise Armitage ◽  
Hannah Grace Roddie ◽  
Iwan Robert Evans
Keyword(s):  
Inflammatory Responses ◽  
Apoptotic Cell ◽  
Calcium Waves ◽  
Apoptotic Cells ◽  
Phagocytic Cells ◽  
Macrophage Function ◽  
Apoptotic Cell Clearance ◽  
Cell Clearance ◽  
Wound Responses

AbstractApoptotic cell clearance by phagocytes is a fundamental process during development, homeostasis and the resolution of inflammation. However, the demands placed on phagocytic cells such as macrophages by this process, and the limitations these interactions impose on subsequent cellular behaviours are not yet clear. Here we seek to understand how apoptotic cells affect macrophage function in the context of a genetically-tractable Drosophila model in which macrophages encounter excessive amounts of apoptotic cells. We show that loss of the glial transcription factor repo, and corresponding removal of the contribution these cells make to apoptotic cell clearance, causes macrophages in the developing embryo to be challenged with large numbers of apoptotic cells. As a consequence, macrophages become highly vacuolated with cleared apoptotic cells and their developmental dispersal and migration is perturbed. We also show that the requirement to deal with excess apoptosis caused by a loss of repo function leads to impaired inflammatory responses to injury. However, in contrast to migratory phenotypes, defects in wound responses cannot be rescued by preventing apoptosis from occurring within a repo mutant background. In investigating the underlying cause of these impaired inflammatory responses, we demonstrate that wound-induced calcium waves propagate into surrounding tissues, including neurons and glia of the ventral nerve cord, which exhibit striking calcium waves on wounding, revealing a previously unanticipated contribution of these cells during responses to injury. Taken together these results demonstrate important insights into macrophage biology and how repo mutants can be used to study macrophage-apoptotic cell interactions in the fly embryo.Furthermore, this work shows how these multipurpose cells can be ‘overtasked’ to the detriment of their other functions, alongside providing new insights into which cells govern macrophage responses to injury in vivo.

scholarly journals Persistence of apoptotic cells without autoimmune disease or inflammation in CD14−/− mice

2004 ◽  
Vol 167 (6) ◽  
pp. 1161-1170 ◽  
Author(s):  
Andrew Devitt ◽  
Kate G. Parker ◽  
Carol Anne Ogden ◽  
Ceri Oldreive ◽  
Michael F. Clay ◽  
...  
Keyword(s):  
Autoimmune Disease ◽  
Apoptotic Cell ◽  
Apoptotic Cells ◽  
Autoantibody Production ◽  
Apoptotic Cell Clearance ◽  
Cell Clearance ◽  
Surface Receptor ◽  
Anti Inflammatory

Interaction of macrophages with apoptotic cells involves multiple steps including recognition, tethering, phagocytosis, and anti-inflammatory macrophage responses. Defective apoptotic cell clearance is associated with pathogenesis of autoimmune disease. CD14 is a surface receptor that functions in vitro in the removal of apoptotic cells by human and murine macrophages, but its mechanism of action has not been defined. Here, we demonstrate that CD14 functions as a macrophage tethering receptor for apoptotic cells. Significantly, CD14−/− macrophages in vivo are defective in clearing apoptotic cells in multiple tissues, suggesting a broad role for CD14 in the clearance process. However, the resultant persistence of apoptotic cells does not lead to inflammation or increased autoantibody production, most likely because, as we show, CD14−/− macrophages retain the ability to generate anti-inflammatory signals in response to apoptotic cells. We conclude that CD14 plays a broad tethering role in apoptotic cell clearance in vivo and that apoptotic cells can persist in the absence of proinflammatory consequences.

scholarly journals Find-me and eat-me signals in apoptotic cell clearance: progress and conundrums

2010 ◽  
Vol 207 (9) ◽  
pp. 1807-1817 ◽  
Author(s):  
Kodi S. Ravichandran
Keyword(s):  
Apoptotic Cell ◽  
Apoptotic Cells ◽  
Apoptotic Cell Clearance ◽  
Cell Clearance ◽  
New Information ◽  
Multiple Receptors ◽  
Dying Cells

Everyday we turnover billions of cells. The quick, efficient, and immunologically silent disposal of the dying cells requires a coordinated orchestration of multiple steps, through which phagocytes selectively recognize and engulf apoptotic cells. Recent studies have suggested an important role for soluble mediators released by apoptotic cells that attract phagocytes (“find-me” signals). New information has also emerged on multiple receptors that can recognize phosphatidylserine, the key “eat-me” signal exposed on the surface of apoptotic cells. This perspective discusses recent exciting progress, gaps in our understanding, and the conflicting issues that arise from the newly acquired knowledge.

scholarly journals Autophagosomes fuse to phagosomes and facilitate the degradation of apoptotic cells in Caenorhabditis elegans

eLife ◽  
2022 ◽  
Vol 11 ◽  
Author(s):  
Omar Peña-Ramos ◽  
Lucia Chiao ◽  
Xianghua Liu ◽  
Xiaomeng Yu ◽  
Tianyou Yao ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Apoptotic Cell ◽  
Adaptor Protein ◽  
Small Gtpase ◽  
Apoptotic Cells ◽  
Phagosome Maturation ◽  
Double Membrane ◽  
C Elegans ◽  
Intracellular Organelles ◽  
Cellular Components

Autophagosomes are double-membrane intracellular vesicles that degrade protein aggregates, intracellular organelles, and other cellular components. During the development of the nematode Caenorhabditis elegans, many somatic and germ cells undergo apoptosis. These cells are engulfed and degraded by their neighboring cells. We discovered a novel role of autophagosomes in facilitating the degradation of apoptotic cells using a real-time imaging technique. Specifically, the double-membrane autophagosomes in engulfing cells are recruited to the surfaces of phagosomes containing apoptotic cells and subsequently fuse to phagosomes, allowing the inner vesicle to enter the phagosomal lumen. Mutants defective in the production of autophagosomes display significant defects in the degradation of apoptotic cells, demonstrating the importance of autophagosomes to this process. The signaling pathway led by the phagocytic receptor CED-1, the adaptor protein CED-6, and the large GTPase dynamin (DYN-1) promotes the recruitment of autophagosomes to phagosomes. Moreover, the subsequent fusion of autophagosomes with phagosomes requires the functions of the small GTPase RAB-7 and the HOPS complex components. Further observations suggest that autophagosomes provide apoptotic cell-degradation activities in addition to and in parallel of lysosomes. Our findings reveal that, unlike the single-membrane, LC3-associated phagocytosis (LAP) vesicles reported for mammalian phagocytes, the canonical double-membrane autophagosomes facilitate the clearance of C. elegans apoptotic cells. These findings add autophagosomes to the collection of intracellular organelles that contribute to phagosome maturation, identify novel crosstalk between the autophagy and phagosome maturation pathways, and discover the upstream signaling molecules that initiate this crosstalk.

scholarly journals C4d Deposition after Allogeneic Renal Transplantation in Rats Is Involved in Initial Apoptotic Cell Clearance

Cells ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 3499
Author(s):  
Stefan Reuter ◽  
Dominik Kentrup ◽  
Alexander Grabner ◽  
Gabriele Köhler ◽  
Konrad Buscher ◽  
...  
Keyword(s):  
Complement Activation ◽  
Apoptotic Cell ◽  
Human Kidney ◽  
Positive Staining ◽  
Apoptotic Cells ◽  
Complement Factors ◽  
Antibody Mediated Rejection ◽  
Apoptotic Cell Clearance ◽  
Cell Clearance ◽  
Renal Transplantations

In the context of transplantation, complement activation is associated with poor prognosis and outcome. While complement activation in antibody-mediated rejection is well-known, less is known about complement activation in acute T cell-mediated rejection (TCMR). There is increasing evidence that complement contributes to the clearance of apoptotic debris and tissue repair. In this regard, we have analysed published human kidney biopsy transcriptome data clearly showing upregulated expression of complement factors in TCMR. To clarify whether and how the complement system is activated early during acute TCMR, experimental syngeneic and allogeneic renal transplantations were performed. Using an allogeneic rat renal transplant model, we also observed upregulation of complement factors in TCMR in contrast to healthy kidneys and isograft controls. While staining for C4d was positive, staining with a C3d antibody showed no C3d deposition. FACS analysis of blood showed the absence of alloantibodies that could have explained the C4d deposition. Gene expression pathway analysis showed upregulation of pro-apoptotic factors in TCMR, and apoptotic endothelial cells were detected by ultrastructural analysis. Monocytes/macrophages were found to bind to and phagocytise these apoptotic cells. Therefore, we conclude that early C4d deposition in TCMR may be relevant to the clearance of apoptotic cells.

scholarly journals Opsonization of Early Apoptotic Cells by IgG from Lupus Nephritis Amplifies Activation of Early Complement Components and Promotes Inflammatory Phagocytosis

2020 ◽  
Author(s):  
Chenghua Wang ◽  
Bing Zhao ◽  
Xiang Liu ◽  
Xiaowei Yang
Keyword(s):  
Lupus Nephritis ◽  
Proinflammatory Cytokines ◽  
Complement Activation ◽  
Apoptotic Cell ◽  
Apoptotic Cells ◽  
Complement Components ◽  
Early Apoptotic Cell ◽  
Apoptotic Cell Clearance ◽  
Cell Clearance ◽  
Terminal Complement

Abstract Background SSA/Ro 60 has been reported to be exposed on the surface of early apoptotic cells and recognized by autoantibodies from lupus. The aim of this study was to explore the subsequent effects of the binding of IgG from anti-SSA positive LN patients on the fate of early apoptotic cells. Results IgG which have been confirmed with extensive binding to early apoptotic cells were purified from three anti-SSA positive LN patients. Opsonization of early apoptotic cells by IgG from LN augmented C3c deposition without influence on the assembly of the terminal complement components or cell lysis. IgG from LN enhanced opsonization and phagocytosis of early apoptotic cells by macrophages directly or dependent on complement activation, with massive TNF-a and IL-1β secretions. Conclusions IgG from anti-SSA positive LN facilitates early apoptotic cell clearance by macrophages and triggers proinflammatory cytokines release, possibly exacerbating underlying pathogenic mechanisms in lupus nephritis.

Abstract 457: CD36, but not G2A, Modulates Efferocytosis, Inflammation and Fibrosis Following Bleomycin-induced Lung Injury

2013 ◽  
Vol 33 (suppl_1) ◽  
Author(s):  
Leland L Black ◽  
Brian W Parks ◽  
Kurt A Zimmerman ◽  
Allison E Metz ◽  
Chad Steele ◽  
...  
Keyword(s):  
Lung Injury ◽  
Apoptotic Cell ◽  
Atherosclerotic Lesion ◽  
M2 Macrophage ◽  
Apoptotic Cells ◽  
Alveolar Cells ◽  
Lesion Development ◽  
Apoptotic Cell Clearance ◽  
Arginase 1 ◽  
Cell Clearance

Oxidatively modified lipids and their by-products presented or released by cells undergoing apoptosis are thought to regulate phagocytic uptake of apoptotic cells by macrophages (efferocytosis) through CD36 scavenger and G2A chemotactic receptors. Although the ability of these receptors to mediate clearance of apoptotic cells in the context of atherosclerosis may have significant impact on lesion development and progression/stability, an overabundance of the lipid ligands for these receptors (CD36: oxidized phospholipids, G2A: lysophosphatidylcholine) as a result of oxidative processes associated with atherogenesis could conceivably impair these clearance mechanisms. Because the indolent nature of atherosclerotic lesion development precludes an accurate assessment of the spatial and kinetic features of lesional efferocytosis, we employed a bleomycin-induced model of lung injury to assess the requirement for G2A and CD36 in efferocytosis. This is a model which, similarly to atherogenesis, is associated with oxidative stress, but in which local apoptosis can be induced and efferocytosis subsequently measured over time. As there is substantial in vivo evidence that ApoE has a role in efferocytosis, we included ApoE knock-out mice as controls. Loss of CD36 (similarly to ApoE deficiency) delayed the clearance of apoptotic alveolar cells, potentiated inflammation (increase in lung neutrophils, lung KC [CXCL1] levels, and lung macrophages) and reduced lung fibrosis following bleomycin-induced lung injury. Reduced fibrosis in CD36-/- mice was associated with lower levels of pro-fibrotic TH2 cytokines (IL-9, IL-13, IL-4), decreased expression of the M2 macrophage marker Arginase-1 and reduced interstitial myofibroblasts. Despite the widely held notion that G2A mediates an LPC dependent “find me” signal in macrophages facilitating apoptotic cell clearance, G2A deficiency had no significant effect on the clearance of apoptotic cells in the bleomycin-induced lung injury model. Our results show that CD36 and ApoE (but not G2A) are important for apoptotic cell clearance following lung injury and subsequently modulate inflammatory and fibrotic processes that could impact not only inflammatory lung disease but also atherosclerosis.

Sign in / Sign up

Export Citation Format

Share Document