scholarly journals Autophagy genes function sequentially to promote apoptotic cell corpse degradation in the engulfing cell

2012 ◽  
Vol 197 (1) ◽  
pp. 27-35 ◽  
Author(s):  
Wei Li ◽  
Wei Zou ◽  
Yihong Yang ◽  
Yongping Chai ◽  
Baohui Chen ◽  
...  
Keyword(s):  
Autoimmune Disease ◽  
Live Cell Imaging ◽  
Cell Imaging ◽  
Apoptotic Cell ◽  
Imaging Techniques ◽  
Time Lapse ◽  
Apoptotic Cell Clearance ◽  
Cell Clearance ◽  
Fundamental Process ◽  
Cell Corpse

Apoptotic cell degradation is a fundamental process for organism development, and impaired clearance causes inflammatory or autoimmune disease. Although autophagy genes were reported to be essential for exposing the engulfment signal on apoptotic cells, their roles in phagocytes for apoptotic cell removal are not well understood. In this paper, we develop live-cell imaging techniques to study apoptotic cell clearance in the Caenorhabditis elegans Q neuroblast lineage. We show that the autophagy proteins LGG-1/LC3, ATG-18, and EPG-5 were sequentially recruited to internalized apoptotic Q cells in the phagocyte. In atg-18 or epg-5 mutants, apoptotic Q cells were internalized but not properly degraded; this phenotype was fully rescued by the expression of autophagy genes in the phagocyte. Time-lapse analysis of autophagy mutants revealed that recruitment of the small guanosine triphosphatases RAB-5 and RAB-7 to the phagosome and the formation of phagolysosome were all significantly delayed. Thus, autophagy genes act within the phagocyte to promote apoptotic cell degradation.

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 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 Impaired Clearance of Apoptotic Cells Promotes Synergy between Atherogenesis and Autoimmune Disease

2004 ◽  
Vol 199 (8) ◽  
pp. 1121-1131 ◽  
Author(s):  
Tamar Aprahamian ◽  
Ian Rifkin ◽  
Ramon Bonegio ◽  
Bénédicte Hugel ◽  
Jean-Marie Freyssinet ◽  
...  
Keyword(s):  
Autoimmune Disease ◽  
Apoptotic Cell ◽  
Low Density Lipoprotein ◽  
Atherosclerotic Lesion ◽  
Density Lipoprotein ◽  
High Cholesterol Diet ◽  
Apoptotic Cells ◽  
Apoptotic Cell Clearance ◽  
Reduced Frequency ◽  
Cell Clearance

To clarify the link between autoimmune disease and hypercholesterolemia, we created the gld.apoE−/− mouse as a model of accelerated atherosclerosis. Atherosclerotic lesion area was significantly increased in gld.apoE−/− mice compared with apoE−/− mice. gld.apoE−/− mice also displayed increases in lymphadenopathy, splenomegaly, and autoantibodies compared with gld mice, and these effects were exacerbated by high cholesterol diet. gld.apoE−/− mice exhibited higher levels of apoptotic cells, yet a reduced frequency of engulfed apoptotic nuclei within macrophages. Infusion of lysophosphatidylcholine, a component of oxidized low density lipoprotein, markedly decreased apoptotic cell clearance in gld mice, indicating that hypercholesterolemia promotes autoimmune disease in this background. These data suggest that defects in apoptotic cell clearance promote synergy between atherosclerotic and autoimmune diseases.

scholarly journals GRK6 deficiency in mice causes autoimmune disease due to impaired apoptotic cell clearance

2013 ◽  
Vol 4 (1) ◽  
Author(s):  
Michio Nakaya ◽  
Mitsuru Tajima ◽  
Hidetaka Kosako ◽  
Takeo Nakaya ◽  
Akiko Hashimoto ◽  
...  
Keyword(s):  
Autoimmune Disease ◽  
Apoptotic Cell ◽  
Apoptotic Cell Clearance ◽  
Cell Clearance

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 Time-Lapse, Live-Cell Imaging of Potassium Efflux in Cell Exposed to Nanosecond Pulsed Electric Fields

2021 ◽  
Vol 120 (3) ◽  
pp. 223a
Author(s):  
Flavia Mazzarda ◽  
Esin B. Sozer ◽  
Julia L. Pittaluga ◽  
Claudia Muratori ◽  
P. Thomas Vernier
Keyword(s):  
Electric Fields ◽  
Live Cell Imaging ◽  
Cell Imaging ◽  
Pulsed Electric Fields ◽  
Time Lapse ◽  
Live Cell ◽  
Potassium Efflux ◽  
Nanosecond Pulsed Electric Fields

Dye selection for live cell imaging of intact siRNA

2012 ◽  
Vol 393 (1-2) ◽  
pp. 23-35 ◽  
Author(s):  
Markus Hirsch ◽  
Dennis Strand ◽  
Mark Helm
Keyword(s):  
Live Cell Imaging ◽  
Cell Imaging ◽  
Fluorescent Dyes ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Time Lapse ◽  
Live Cell ◽  
High Yield ◽  
Ph Variation ◽  
Rnai Efficiency

Abstract Investigations into the fate of small interfering RNA (siRNA) after transfection may unravel new ways to improve RNA interference (RNAi) efficiency. Because intracellular degradation of RNA may prevent reliable observation of fluorescence-labeled siRNA, new tools for fluorescence microscopy are warranted to cover the considerable duration of the RNAi effect. Here, the characterization and application of new fluorescence resonance energy transfer (FRET) dye pairs for sensing the integrity of duplex siRNA is reported, which allows an assessment of the degradation status of an siRNA cell population by live cell imaging. A panel of high-yield fluorescent dyes has been investigated for their suitability as FRET pairs for the investigation of RNA inside the cell. Nine dyes in 13 FRET pairs were evaluated based on the performance in assays of photostability, cross-excitation, bleed-through, as well as on quantified changes of fluorescence as a consequence of, e.g., RNA strand hybridization and pH variation. The Atto488/Atto590 FRET pair has been applied to live cell imaging, and has revealed first aspects of unusual trafficking of intact siRNA. A time-lapse study showed highly dynamic movement of siRNA in large perinuclear structures. These and the resulting optimized FRET labeled siRNA are expected to have significant impact on future observations of labeled RNAs in living cells.

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