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Frontiers in Immunology 2022Integrins are a large group of cell-surface proteins that are classified as transmembrane proteins. Integrins are classified into different types based on sequence... (Review)
Review
Integrins are a large group of cell-surface proteins that are classified as transmembrane proteins. Integrins are classified into different types based on sequence variations, leading to structural and functional diversity. They are broadly distributed in animals and have a wide range of biological functions such as cell-to-cell communication, intracellular cytoskeleton organization, cellular signaling, immune responses, etc. Integrins are among the most abundant cell surface proteins in insects, exhibiting their indispensability in insect physiology. Because of their critical biological involvement in physiological processes, they appear to be a novel target for designing effective pest control strategies. In the current literature review, we first discuss the discovery and expression responses of integrins against various types of pathogens. Secondly, we examine the specific biological roles of integrins in controlling microbial pathogens, such as phagocytosis, encapsulation, nodulation, immune signaling, and so on. Finally, we describe the possible uses of integrins to control agricultural insect pests.
Topics: Animals; Insecta; Integrins; Phagocytosis; Signal Transduction
PubMed: 35757717
DOI: 10.3389/fimmu.2022.906294 -
Journal of Cerebral Blood Flow and... Mar 2023Myelination is an important process in the central nervous system (CNS). Oligodendrocytes (OLs) extend multiple layers to densely sheath on axons, composing the myelin... (Review)
Review
Myelination is an important process in the central nervous system (CNS). Oligodendrocytes (OLs) extend multiple layers to densely sheath on axons, composing the myelin to achieve efficient electrical signal conduction. The myelination during developmental stage maintains a balanced state. However, numerous CNS diseases including neurodegenerative and cerebrovascular diseases cause demyelination and disrupt the homeostasis, resulting in inflammation and white matter deficits. Effective clearance of myelin debris is needed in the region of demyelination, which is a key step for remyelination and tissue regeneration. Microglia and astrocytes are the major resident phagocytic cells in the brain, which may play different or collaborative roles in myelination. Microglia and astrocytes participate in developmental myelination through engulfing excessive unneeded myelin. They are also involved in the clearance of degenerated myelin debris for accelerating remyelination, or engulfing healthy myelin sheath for inhibiting remyelination. This review focuses on the roles of microglia and astrocytes in phagocytosing myelin in the developmental brain and diseased brain. In addition, the interaction between microglia and astrocytes to mediate myelin engulfment is also summarized.
Topics: Humans; Myelin Sheath; Astrocytes; Microglia; Demyelinating Diseases; Oligodendroglia; White Matter; Phagocytosis
PubMed: 36324281
DOI: 10.1177/0271678X221137762 -
Frontiers in Cellular and Infection... 2021Cells of the innate immune system continuously patrol the extracellular environment for potential microbial threats that are to be neutralized by phagocytosis and... (Review)
Review
Cells of the innate immune system continuously patrol the extracellular environment for potential microbial threats that are to be neutralized by phagocytosis and delivery to lysosomes. In addition, phagocytes employ autophagy as an innate immune mechanism against pathogens that succeed to escape the phagolysosomal pathway and invade the cytosol. In recent years, LC3-associated phagocytosis (LAP) has emerged as an intermediate between phagocytosis and autophagy. During LAP, phagocytes target extracellular microbes while using parts of the autophagic machinery to label the cargo-containing phagosomes for lysosomal degradation. LAP contributes greatly to host immunity against a multitude of bacterial pathogens. In the pursuit of survival, bacteria have developed elaborate strategies to disarm or circumvent the LAP process. In this review, we will outline the nature of the LAP mechanism and discuss recent insights into its interplay with bacterial pathogens.
Topics: Autophagy; Bacteria; Microtubule-Associated Proteins; Phagocytosis; Phagosomes
PubMed: 35047422
DOI: 10.3389/fcimb.2021.809121 -
Frontiers in Neural Circuits 2021Müller glia of the retina share many features with astroglia located throughout the brain including maintenance of homeostasis, modulation of neurotransmitter... (Review)
Review
Müller glia of the retina share many features with astroglia located throughout the brain including maintenance of homeostasis, modulation of neurotransmitter spillover, and robust response to injury. Here we present the molecular factors and signaling events that govern Müller glial specification, patterning, and differentiation. Next, we discuss the various roles of Müller glia in retinal development, which include maintaining retinal organization and integrity as well as promoting neuronal survival, synaptogenesis, and phagocytosis of debris. Finally, we review the mechanisms by which Müller glia integrate into retinal circuits and actively participate in neuronal signaling during development.
Topics: Astrocytes; Neurogenesis; Neuroglia; Phagocytosis; Retina
PubMed: 35185477
DOI: 10.3389/fncir.2021.815923 -
Journal of Pharmacological Sciences Mar 2021In the central nervous system, microglia are regarded as the main cells responsible for phagocytosis, contributing to neural circuit refinement and homeostasis through... (Review)
Review
In the central nervous system, microglia are regarded as the main cells responsible for phagocytosis, contributing to neural circuit refinement and homeostasis through synapse elimination. However, recent findings have shown that astrocytes also actively participate in synapse homeostasis through phagocytosing synapses, neuronal debris, axonal mitochondria, and pathological protein aggregates. In addition, it has been also suggested that astrocytes may regulate microglial phagocytosis by secreting molecules such as IL-33 and C3. Here, we have introduced key findings regarding direct and indirect astrocyte-mediated phagocytosis in CNS development, the sleep/wake cycle, and aging. We have also discussed current information about reactive astrocytes and their phagocytic function in the diseased brain, focusing on ischemia and Alzheimer's disease. Through this review, we aim to provide an overview of the current status as well as future perspectives regarding the important role of astrocytic control of phagocytosis.
Topics: Aging; Alzheimer Disease; Astrocytes; Brain; Brain Ischemia; Complement C3; Homeostasis; Humans; Interleukin-33; Microglia; Phagocytosis; Protein Aggregation, Pathological; Synapses
PubMed: 33602502
DOI: 10.1016/j.jphs.2020.12.007 -
Developmental Cell Jul 2016The phagocytic clearance of dying cells in a tissue is a highly orchestrated series of intercellular events coordinated by a complex signaling network. Recent data from... (Review)
Review
The phagocytic clearance of dying cells in a tissue is a highly orchestrated series of intercellular events coordinated by a complex signaling network. Recent data from genetic, biochemical, and live-imaging approaches have greatly enhanced our understanding of the dynamics of cell clearance and how the process is orchestrated at the cellular and tissue levels. We discuss how networks regulating apoptotic cell clearance are integrated to enable a rapid, efficient, and high-capacity clearance system within tissues.
Topics: Animals; Apoptosis; Humans; Phagocytosis; Signal Transduction
PubMed: 27459067
DOI: 10.1016/j.devcel.2016.06.029 -
Journal of Anatomy Oct 2017Müller cells are the predominant glial cell type in the retina of vertebrates. They play a wide variety of roles in both the developing and the mature retina that have... (Review)
Review
Müller cells are the predominant glial cell type in the retina of vertebrates. They play a wide variety of roles in both the developing and the mature retina that have been widely reported in the literature. However, less attention has been paid to their role in phagocytosis of cell debris under physiological, pathological or experimental conditions. Müller glia have been shown to phagocytose apoptotic cell bodies originated during development of the visual system. They also engulf foreign molecules that are injected into the eye, cone outer segments and injured photoreceptors. Phagocytosis of photoreceptor cell debris in the light-damaged teleost retina is primarily carried out by Müller cells. Once the microglial cells become activated and migrate to the photoreceptor cell layer, the phagocytic activity of Müller cells progressively decreases, suggesting a possible mechanism of communication between Müller cells and neighbouring microglia and photoreceptors. Additionally, it has been shown that phagocytic Müller cells acquire proliferating activity in the damaged teleost retina, suggesting that engulfment of apoptotic photoreceptor debris might stimulate the Müller glia to proliferate during the regenerative response. These findings highlight Müller glia phagocytosis as an underlying mechanism contributing to degeneration and regeneration under pathological conditions.
Topics: Animals; Ependymoglial Cells; Humans; Phagocytosis
PubMed: 28695619
DOI: 10.1111/joa.12653 -
Microbiology Spectrum Nov 2016Myeloid cells make extensive use of the complement system in the context of recruitment, phagocytosis, and other effector functions. There are several types of... (Review)
Review
Myeloid cells make extensive use of the complement system in the context of recruitment, phagocytosis, and other effector functions. There are several types of complement receptors on myeloid cells, including G protein-coupled receptors for localizing the source of complement activation, and three sets of type I transmembrane proteins that link complement to phagocytosis: complement receptor 1, having an extracellular domain with tandem complement regulatory repeats; complement receptors 3 and 4, which are integrin family receptors comprising heterodimers of type I transmembrane subunits; and VSIG4, a member of the Ig superfamily. This review will focus on the role of the different classes of complement receptors and how their activities are integrated in the setting of immune tolerance and inflammatory responses.
Topics: Animals; Cell Adhesion; Humans; Myeloid Cells; Phagocytosis; Receptors, Complement
PubMed: 27809953
DOI: 10.1128/microbiolspec.MCHD-0034-2016 -
Frontiers in Immunology 2023Intestinal epithelial cells (IECs) are the first to encounter luminal microorganisms and actively participate in intestinal immunity. We reported that IECs express the...
BACKGROUND
Intestinal epithelial cells (IECs) are the first to encounter luminal microorganisms and actively participate in intestinal immunity. We reported that IECs express the β-glucan receptor Dectin-1, and respond to commensal fungi and β-glucans. In phagocytes, Dectin-1 mediates LC3-associated phagocytosis (LAP) utilizing autophagy components to process extracellular cargo. Dectin-1 can mediate phagocytosis of β-glucan-containing particles by non-phagocytic cells. We aimed to determine whether human IECs phagocytose β-glucan-containing fungal particles LAP.
METHODS
Colonic (n=18) and ileal (n=4) organoids from individuals undergoing bowel resection were grown as monolayers. Fluorescent-dye conjugated zymosan (β-glucan particle), heat-killed- and UV inactivated were applied to differentiated organoids and to human IEC lines. Confocal microscopy was used for live imaging and immuno-fluorescence. Quantification of phagocytosis was carried out with a fluorescence plate-reader.
RESULTS
zymosan and particles were phagocytosed by monolayers of human colonic and ileal organoids and IEC lines. LAP was identified by LC3 and Rubicon recruitment to phagosomes and lysosomal processing of internalized particles was demonstrated by co-localization with lysosomal dyes and LAMP2. Phagocytosis was significantly diminished by blockade of Dectin-1, actin polymerization and NAPDH oxidases.
CONCLUSIONS
Our results show that human IECs sense luminal fungal particles and internalize them LAP. This novel mechanism of luminal sampling suggests that IECs may contribute to the maintenance of mucosal tolerance towards commensal fungi.
Topics: Humans; beta-Glucans; Epithelial Cells; Fungi; Phagocytosis; Zymosan
PubMed: 36969163
DOI: 10.3389/fimmu.2023.1142492 -
The FEBS Journal Oct 2018It was previously thought that neurons were phagocytosed only when dead or dying. However, it is increasingly clear that viable synapses, dendrites, axons and whole... (Review)
Review
It was previously thought that neurons were phagocytosed only when dead or dying. However, it is increasingly clear that viable synapses, dendrites, axons and whole neurons can be phagocytosed alive (defined here as neurophagy), and this may contribute to a wide range of developmental, physiological and pathological processes. Phagocytosis of live synapses, dendrites and axons by glia contributes to experience-dependent sculpting of neuronal networks during development, but excessive phagocytosis of synapses may contribute to pathology in Alzheimer's disease, schizophrenia and ageing. Neurons can expose phosphatidylserine or calreticulin, which act as 'eat me' signals provoking phagocytosis via microglial receptors, whereas sialylation of neuronal surfaces acts as a 'don't eat me' signal that inhibits phagocytosis and desialylation can provoke phagocytosis. Opsonins, such as complement components and apolipoproteins, are released during inflammation and enhance engulfment. Phagocytosis of neurons is seen in multiple human diseases, but it is as yet unclear whether inhibition of phagocytosis will be beneficial in treating neurological diseases. Here we review the signals regulating glial phagocytosis of live neurons and synapses, and the involvement of this phagocytosis in development and disease.
Topics: Animals; Brain Diseases; Cell Death; Humans; Inflammation; Neuroglia; Neurons; Phagocytosis; Synapses
PubMed: 29125686
DOI: 10.1111/febs.14323