-
The International Journal of... Jun 2022Autoimmune cytopenias are a consequence of autoantibodies that target blood cell lineages and mark them for their accelerated destruction, mostly through phagocytosis by... (Review)
Review
Autoimmune cytopenias are a consequence of autoantibodies that target blood cell lineages and mark them for their accelerated destruction, mostly through phagocytosis by monocytes and macrophages and complement activation. Neutrophils, although equipped with Fc and complement receptors and effector mechanisms that are critical in other autoimmune conditions, remained long overlooked. Recent reports, however, propose a new and possibly critical role of neutrophils. In this review, we gathered available evidence on the contribution of neutrophils to the development, onset, and consequences of autoantibody-dependent cytopenias.
Topics: Autoantibodies; Autoimmune Diseases; Humans; Macrophages; Neutrophils; Phagocytosis
PubMed: 35644471
DOI: 10.1016/j.biocel.2022.106231 -
Cell Host & Microbe Aug 2021Engagement of LC3-associated phagocytosis (LAP) in response to the uptake of certain particles modulates innate immune responses. Now in Cell Host and Microbe,...
Engagement of LC3-associated phagocytosis (LAP) in response to the uptake of certain particles modulates innate immune responses. Now in Cell Host and Microbe, Akoumianaki et al. (2021) show how a regulatory role of IL-6 on LAP may be at the core of susceptibility to secondary infection during severe sepsis.
Topics: Autophagy; Humans; Immunity, Innate; Microtubule-Associated Proteins; Phagocytosis; Phagosomes
PubMed: 34384524
DOI: 10.1016/j.chom.2021.07.010 -
Immunity Feb 2023β-glucosylceramide (β-GlcCer) accumulates in Gaucher disease, but how β-GlcCer, a Mincle ligand, causes characteristic neuroinflammation and neuronopathy is poorly...
β-glucosylceramide (β-GlcCer) accumulates in Gaucher disease, but how β-GlcCer, a Mincle ligand, causes characteristic neuroinflammation and neuronopathy is poorly understood. In this issue of Immunity, Shimizu et al. reveal that Mincle-dependent activation of microglia led to phagocytosis of neurons and neurologic symptoms.
Topics: Lectins; Microglia; Neurons; Phagocytosis; Selectins
PubMed: 36792566
DOI: 10.1016/j.immuni.2023.01.020 -
Frontiers in Immunology 2023Microglia are an integral part of central nervous system, but our understanding of microglial biology is limited due to the challenges in obtaining and culturing primary...
BACKGROUND
Microglia are an integral part of central nervous system, but our understanding of microglial biology is limited due to the challenges in obtaining and culturing primary human microglia. HMC3 is an important cell line for studying human microglia because it is readily accessible and straightforward to maintain in standard laboratories. Although HMC3 is widely used for microglial research, a robust genetic method has not been described. Here, we report a CRISPR genome editing platform, by the electroporation of Cas9 ribonucleoproteins (Cas9 RNP) and synthetic DNA repair templates, to enable rapid and precise genetic modifications of HMC3. For proof-of-concept demonstrations, we targeted the genes implicated in the regulation of amyloid beta (Aβ) and glioblastoma phagocytosis in microglia. We showed that CRISPR genome editing could enhance the phagocytic activities of HMC3.
METHODS
We performed CRISPR gene knockout (KO) in HMC3 by the electroporation of pre-assembled Cas9 RNP. Co-introduction of DNA repair templates allowed site-specific knock-in (KI) of an epitope tag, a synthetic promoter and a fluorescent reporter gene. The editing efficiencies were determined genotypically by DNA sequencing and phenotypically by immunofluorescent staining and flow cytometry. The gene-edited HMC3 cells were examined by fluorescent Aβ and glioblastoma phagocytosis assays.
RESULTS
Our platform enabled robust single (>90%) and double (>70%) KO without detectable off-target editing by high throughput DNA sequencing. We also inserted a synthetic SFFV promoter to efficiently upregulate the expression of endogenous and genes associated with microglial phagocytosis. The CRISPR-edited HMC3 showed stable phenotypes and enhanced phagocytosis of fluorescence-labeled Aβ1-42 peptides. Confocal microscopy further confirmed the localization of Aβ aggregates in the acidified lysosomes. HMC3 mutants also changed the phagocytic characteristic toward apoptotic glioblastoma cells.
CONCLUSION
CRISPR genome editing by Cas9 RNP electroporation is a robust approach to genetically modify HMC3 for functional studies such as the interrogation of Aβ and tumor phagocytosis, and is readily adoptable to investigate other aspects of microglial biology.
Topics: Humans; Gene Editing; CRISPR-Cas Systems; Microglia; Glioblastoma; Amyloid beta-Peptides; Phagocytosis
PubMed: 37483607
DOI: 10.3389/fimmu.2023.1169725 -
Frontiers in Immunology 2021Mammalian phagocytes can phagocytose (i.e. eat) other mammalian cells in the body if they display certain signals, and this phagocytosis plays fundamental roles in... (Review)
Review
Mammalian phagocytes can phagocytose (i.e. eat) other mammalian cells in the body if they display certain signals, and this phagocytosis plays fundamental roles in development, cell turnover, tissue homeostasis and disease prevention. To phagocytose the correct cells, phagocytes must discriminate which cells to eat using a 'phagocytic code' - a set of over 50 known phagocytic signals determining whether a cell is eaten or not - comprising find-me signals, eat-me signals, don't-eat-me signals and opsonins. Most opsonins require binding to eat-me signals - for example, the opsonins galectin-3, calreticulin and C1q bind asialoglycan eat-me signals on target cells - to induce phagocytosis. Some proteins act as 'self-opsonins', while others are 'negative opsonins' or 'phagocyte suppressants', inhibiting phagocytosis. We review known phagocytic signals here, both established and novel, and how they integrate to regulate phagocytosis of several mammalian targets - including excess cells in development, senescent and aged cells, infected cells, cancer cells, dead or dying cells, cell debris and neuronal synapses. Understanding the phagocytic code, and how it goes wrong, may enable novel therapies for multiple pathologies with too much or too little phagocytosis, such as: infectious disease, cancer, neurodegeneration, psychiatric disease, cardiovascular disease, ageing and auto-immune disease.
Topics: Animals; Calreticulin; Cellular Senescence; Humans; Intercellular Adhesion Molecule-3; Opsonin Proteins; Phagocytosis; Phosphatidylserines; Polysaccharides; Signal Transduction; Synapses
PubMed: 34177884
DOI: 10.3389/fimmu.2021.629979 -
Nature Communications Aug 2023The opportunistic fungal pathogen Cryptococcus neoformans causes lethal infections in immunocompromised patients. Macrophages are central to the host response to...
The opportunistic fungal pathogen Cryptococcus neoformans causes lethal infections in immunocompromised patients. Macrophages are central to the host response to cryptococci; however, it is unclear how C. neoformans is recognised and phagocytosed by macrophages. Here we investigate the role of TLR4 in the non-opsonic phagocytosis of C. neoformans. We find that loss of TLR4 function unexpectedly increases phagocytosis of non-opsonised cryptococci by murine and human macrophages. The increased phagocytosis observed in Tlr4 cells was dampened by pre-treatment of macrophages with oxidised-LDL, a known ligand of scavenger receptors. The scavenger receptor, macrophage scavenger receptor 1 (MSR1) (also known as SR-A1 or CD204) was upregulated in Tlr4 macrophages. Genetic ablation of MSR1 resulted in a 75% decrease in phagocytosis of non-opsonised cryptococci, strongly suggesting that it is a key non-opsonic receptor for this pathogen. We go on to show that MSR1-mediated uptake likely involves the formation of a multimolecular signalling complex involving FcγR leading to SYK, PI3K, p38 and ERK1/2 activation to drive actin remodelling and phagocytosis. Altogether, our data indicate a hitherto unidentified role for TLR4/MSR1 crosstalk in the non-opsonic phagocytosis of C. neoformans.
Topics: Animals; Humans; Mice; Cryptococcosis; Cryptococcus neoformans; Macrophages; Phagocytosis; Toll-Like Receptor 4; Scavenger Receptors, Class A
PubMed: 37580395
DOI: 10.1038/s41467-023-40635-w -
F1000Research 2020Despite their comparatively low abundance in biological membranes, phosphoinositides are key to the regulation of a diverse array of signaling pathways and direct... (Review)
Review
Despite their comparatively low abundance in biological membranes, phosphoinositides are key to the regulation of a diverse array of signaling pathways and direct membrane traffic. The role of phosphoinositides in the initiation and progression of endocytic pathways has been studied in considerable depth. Recent advances have revealed that distinct phosphoinositide species feature prominently in clathrin-dependent and -independent endocytosis as well as in phagocytosis and macropinocytosis. Moreover, a variety of intracellular and cell-associated pathogens have developed strategies to commandeer host cell phosphoinositide metabolism to gain entry and/or metabolic advantage, thereby promoting their survival and proliferation. Here, we briefly survey the current knowledge on the involvement of phosphoinositides in endocytosis, phagocytosis, and macropinocytosis and highlight several examples of molecular mimicry employed by pathogens to either "hitch a ride" on endocytic pathways endogenous to the host or create an entry path of their own.
Topics: Clathrin; Endocytosis; Phagocytosis; Phosphatidylinositols; Protein Transport
PubMed: 32494357
DOI: 10.12688/f1000research.22393.1 -
Communications Biology Jan 2022New research shows that disease-associated microglia in neurodegenerative brains present features of elevated phagocytosis, lysosomal functions, and lipid metabolism,...
New research shows that disease-associated microglia in neurodegenerative brains present features of elevated phagocytosis, lysosomal functions, and lipid metabolism, which benefit brain repair. The underlying mechanisms remain poorly understood. Intracellular pH (pH) is important for regulating aerobic glycolysis in microglia, where Na/H exchanger (NHE1) is a key pH regulator by extruding H in exchange of Na influx. We report here that post-stroke Cx3cr1-Cre;Nhe1 (Nhe1 cKO) brains displayed stimulation of microglial transcriptomes of rate-limiting enzyme genes for glycolysis, tricarboxylic acid cycle, and oxidative phosphorylation. The other upregulated genes included genes for phagocytosis and LXR/RXR pathway activation as well as the disease-associated microglia hallmark genes (Apoe, Trem2, Spp1). The cKO microglia exhibited increased oxidative phosphorylation capacity, and higher phagocytic activity, which likely played a role in enhanced synaptic stripping and remodeling, oligodendrogenesis, and remyelination. This study reveals that genetic blockade of microglial NHE1 stimulated oxidative phosphorylation immunometabolism, and boosted phagocytosis function which is associated with tissue remodeling and post-stroke cognitive function recovery.
Topics: Animals; Brain; Cells, Cultured; Cognition; Disease Models, Animal; Female; Male; Mice; Mice, Transgenic; Microglia; Neuronal Plasticity; Oxidative Phosphorylation; Phagocytosis; Recovery of Function; Stroke
PubMed: 35017668
DOI: 10.1038/s42003-021-02984-4 -
Genes Jan 2023is the enteric protozoan parasite responsible for amebiasis. Trophozoites of ingest human cells in the intestine and other organs, which is the hallmark of its... (Review)
Review
is the enteric protozoan parasite responsible for amebiasis. Trophozoites of ingest human cells in the intestine and other organs, which is the hallmark of its pathogenesis. Phagocytosis and trogocytosis are pivotal biological functions for its virulence and also contribute to the proliferation of nutrient uptake from the environment. We previously elucidated the role of a variety of proteins associated with phagocytosis and trogocytosis, including Rab small GTPases, Rab effectors, including retromer, phosphoinositide-binding proteins, lysosomal hydrolase receptors, protein kinases, and cytoskeletal proteins. However, a number of proteins involved in phagocytosis and trogocytosis remain to be identified, and mechanistic details of their involvement must be elucidated at the molecular level. To date, a number of studies in which a repertoire of proteins associated with phagosomes and potentially involved in phagocytosis have been conducted. In this review, we revisited all phagosome proteome studies we previously conducted in order to reiterate information on the proteome of phagosomes. We demonstrated the core set of constitutive phagosomal proteins and also the set of phagosomal proteins recruited only transiently or in condition-dependent fashions. The catalogs of phagosome proteomes resulting from such analyses can be a useful source of information for future mechanistic studies as well as for confirming or excluding a possibility of whether a protein of interest in various investigations is likely or is potentially involved in phagocytosis and phagosome biogenesis.
Topics: Humans; Entamoeba histolytica; Proteome; Proteomics; Phagocytosis; Phagosomes; rab GTP-Binding Proteins
PubMed: 36833306
DOI: 10.3390/genes14020379 -
International Journal of Molecular... Mar 2023Macrophages can be characterized as a very multifunctional cell type with a spectrum of phenotypes and functions being observed spatially and temporally in various... (Review)
Review
Macrophages can be characterized as a very multifunctional cell type with a spectrum of phenotypes and functions being observed spatially and temporally in various disease states. Ample studies have now demonstrated a possible causal link between macrophage activation and the development of autoimmune disorders. How these cells may be contributing to the adaptive immune response and potentially perpetuating the progression of neurodegenerative diseases and neural injuries is not fully understood. Within this review, we hope to illustrate the role that macrophages and microglia play as initiators of adaptive immune response in various CNS diseases by offering evidence of: (1) the types of immune responses and the processes of antigen presentation in each disease, (2) receptors involved in macrophage/microglial phagocytosis of disease-related cell debris or molecules, and, finally, (3) the implications of macrophages/microglia on the pathogenesis of the diseases.
Topics: Humans; Microglia; Macrophages; Central Nervous System Diseases; Phagocytosis; Neurodegenerative Diseases
PubMed: 36982999
DOI: 10.3390/ijms24065925