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Frontiers in Immunology 2018Macropinocytosis has received increasing attention in recent years for its various roles in nutrient acquisition, immune surveillance, and virus and cancer pathologies.... (Review)
Review
Macropinocytosis has received increasing attention in recent years for its various roles in nutrient acquisition, immune surveillance, and virus and cancer pathologies. In most cases macropinocytosis is initiated by the sudden increase in an external stimulus such as a growth factor. This "induced" form of macropinocytosis has been the subject of much of the work addressing its mechanism and function over the years. An alternative, "constitutive" form of macropinocytosis restricted to primary innate immune cells also exists, although its mechanism has remained severely understudied. This mini-review focuses on the very recent advances that have shed new light on the initiation, formation and functional relevance of constitutive macropinocytosis in primary innate immune cells. An emphasis is placed on how this new understanding of constitutive macropinocytosis is helping to define the sentinel function of innate immune cells including polarized macrophages and dendritic cells.
Topics: Animals; Antigen Presentation; Biomarkers; Dendritic Cells; Humans; Immunity, Innate; Immunologic Surveillance; Macrophages; Pinocytosis; Receptors, Pattern Recognition; Signal Transduction
PubMed: 30333835
DOI: 10.3389/fimmu.2018.02286 -
International Journal of Molecular... Nov 2020Pancreatic ductal adenocarcinoma (PDAC), an extremely aggressive invasive cancer, is the fourth most common cause of cancer-related death in the United States. The... (Review)
Review
Pancreatic ductal adenocarcinoma (PDAC), an extremely aggressive invasive cancer, is the fourth most common cause of cancer-related death in the United States. The higher mortality in PDAC is often attributed to the inability to detect it until it has reached advanced stages. The major challenge in tackling PDAC is due to its elusive pathology, minimal effectiveness, and resistance to existing therapeutics. The aggressiveness of PDAC is due to the capacity of tumor cells to alter their metabolism, utilize the diverse available fuel sources to adapt and grow in a hypoxic and harsh environment. Therapeutic resistance is due to the presence of thick stroma with poor angiogenesis, thus making drug delivery to tumor cells difficult. Investigating the metabolic mediators and enzymes involved in metabolic reprogramming may lead to the identification of novel therapeutic targets. The metabolic mediators of glucose, glutamine, lipids, nucleotides, amino acids and mitochondrial metabolism have emerged as novel therapeutic targets. Additionally, the role of autophagy, macropinocytosis, lysosomal transport, recycling, amino acid transport, lipid transport, and the role of reactive oxygen species has also been discussed. The role of various pro-inflammatory cytokines and immune cells in the pathogenesis of PDAC and the metabolites involved in the signaling pathways as therapeutic targets have been previously discussed. This review focuses on the therapeutic potential of metabolic mediators in PDAC along with stemness due to metabolic alterations and their therapeutic importance.
Topics: Adenocarcinoma; Amino Acids; Animals; Autophagy; Carcinoma, Pancreatic Ductal; Cytokines; Humans; Pancreatic Neoplasms; Pinocytosis; Reactive Oxygen Species; Signal Transduction
PubMed: 33198082
DOI: 10.3390/ijms21228502 -
Frontiers in Immunology 2019There are several lines of evidence indicating that the physiopathological bases of bullous pemphigoid (BP), the most common subepidermal autoimmune bullous disease, are... (Review)
Review
There are several lines of evidence indicating that the physiopathological bases of bullous pemphigoid (BP), the most common subepidermal autoimmune bullous disease, are hallmarked by the production of autoantibodies directed against the hemidesmosomal anchoring proteins BP180 and BP230. In contrast to the robustness of the latter assumption, the multifaceted complexity of upstream and downstream mechanisms implied in the pathogenesis of BP remains an area of intense speculation. So far, an imbalance between T regulatory cells and autoreactive T helper (Th) cells has been regarded as the main pathogenic factor triggering the autoimmune response in BP patients. However, the contributory role of signaling pathways fostering the B cell stimulation, such as Toll-like receptor activation, as well as that of ancillary inflammatory mechanisms responsible for blister formation, such as Th17 axis stimulation and the activation of the coagulation cascade, are still a matter of debate. In the same way, the pathomechanisms implied in the loss of dermal-epidermal adhesion secondary to autoantibodies binding are not fully understood. Herein, we review in detail the current concepts and controversies on the complex pathogenesis of BP, shedding light on the most recent theories emerging from the literature.
Topics: Autoantibodies; Autoantigens; Autoimmunity; Blood Coagulation; Comorbidity; Complement Activation; Dystonin; Humans; Leukocytes; Neurodegenerative Diseases; Non-Fibrillar Collagens; Pemphigoid, Bullous; Pinocytosis; Thrombosis; Vitamin D Deficiency; Collagen Type XVII
PubMed: 31312206
DOI: 10.3389/fimmu.2019.01506 -
Current Biology : CB Aug 2020Macropinocytic cups enable cells to take up droplets of medium into internal vesicles. These cups are formed by the actin cytoskeleton around signaling patches of Ras,...
Macropinocytic cups enable cells to take up droplets of medium into internal vesicles. These cups are formed by the actin cytoskeleton around signaling patches of Ras, Rac and the phosphoinositide PIP3 in the plasma membrane. New work now describes a Ras regulator that controls both the size and efficiency of these patches.
Topics: Bacteria; Cell Membrane Structures; Endocytosis; Phagocytosis; Pinocytosis
PubMed: 32750349
DOI: 10.1016/j.cub.2020.06.050 -
Theranostics 2022KRAS mutations are one of the most common gene mutations linked to cancer, presenting in approximately 25% of all tumors, especially pancreatic, lung, and colorectal... (Review)
Review
KRAS mutations are one of the most common gene mutations linked to cancer, presenting in approximately 25% of all tumors, especially pancreatic, lung, and colorectal cancers. Mutant KRAS has long been considered an undruggable target, stalling progress in direct KRAS targeting for many years, while targeted drug delivery into KRAS mutant cells utilizing their transformed metabolic behavior might present an alternative opportunity. Macropinocytosis, a nonselective, fluid-phase, endocytic route, was found to be upregulated as a metabolic feature in KRAS-driven tumors and plays a critical role in nutrient acquisition from extracellular fluids. With the observation that a variety of drug delivery systems could be internalized by KRAS mutant cancer cells through macropinocytosis, exploiting macropinocytosis for intracellular delivery of therapeutics into KRAS mutant tumor cells is emerging as a new drug delivery expedition. In this article, we summarized cancer biology studies that examined KRAS mutation-induced macropinocytosis, reviewed recent studies exploiting macropinocytosis enhancement for KRAS mutant cancer cell-selective drug delivery, and discussed the potential opportunities, challenges and pitfalls of this strategy.
Topics: Cell Line, Tumor; Drug Delivery Systems; Humans; Mutation; Neoplasms; Pinocytosis; Proto-Oncogene Proteins p21(ras)
PubMed: 35154489
DOI: 10.7150/thno.67889 -
Journal of Visualized Experiments : JoVE May 2021Membrane ruffling is the formation of motile plasma membrane protrusions containing a meshwork of newly polymerized actin filaments. Membrane ruffles may form...
Membrane ruffling is the formation of motile plasma membrane protrusions containing a meshwork of newly polymerized actin filaments. Membrane ruffles may form spontaneously or in response to growth factors, inflammatory cytokines, and phorbol esters. Some of the membrane protrusions may reorganize into circular membrane ruffles that fuse at their distal margins and form cups that close and separate into the cytoplasm as large, heterogeneous vacuoles called macropinosomes. During the process, ruffles trap extracellular fluid and solutes that internalize within macropinosomes. High-resolution scanning electron microscopy (SEM) is a commonly used imaging technique to visualize and quantify membrane ruffle formation, circular protrusions, and closed macropinocytic cups on the cell surface. The following protocol describes the cell culture conditions, stimulation of the membrane ruffle formation in vitro, and how to fix, dehydrate, and prepare cells for imaging using SEM. Quantification of membrane ruffling, data normalization, and stimulators and inhibitors of membrane ruffle formation are also described. This method can help answer key questions about the role of macropinocytosis in physiological and pathological processes, investigate new targets that regulate membrane ruffle formation, and identify yet uncharacterized physiological stimulators as well as novel pharmacological inhibitors of macropinocytosis.
Topics: Actin Cytoskeleton; Cell Membrane; Cell Surface Extensions; Microscopy, Electron, Scanning; Pinocytosis
PubMed: 34125102
DOI: 10.3791/62658 -
Physiological Reports Feb 2021Piglets must acquire passive immunity through colostrum within hours after birth to survive. How colostral macromolecules traverse the small intestinal epithelium may...
Piglets must acquire passive immunity through colostrum within hours after birth to survive. How colostral macromolecules traverse the small intestinal epithelium may include nonselective pinocytosis and paracellular transport through tight junction proteins located between epithelial cells. Claudin proteins-3 and -4 contribute to the epithelial tight junctions (TJs) on the apical aspect of lateral surfaces of intestinal epithelial cells (IECs) where they help regulate ion and macromolecule movement across the intestinal epithelium. Throughout the small intestine of newborn piglets, Claudin-3 was localized to the lateral and basolateral surface of intestinal epithelial cells as well as the membrane of large vacuoles. In the duodenum and jejunum, Claudin-4 was localized to the apical surface independent of tight junction regions. In the ileum, Claudin-4 was localized to the lateral and basolateral surfaces indicating region-specific differences and noncanonical patterns of Claudin-4 localization independent of tight junction regions. Understanding the timing of changes in surface localization of Claudin-3 and Claudin-4 and how they may coincide with changes in small intestinal permeability may help develop new protective strategies against infectious diseases within newborn piglets.
Topics: Animals; Animals, Newborn; Biological Transport; Claudin-3; Claudin-4; Colostrum; Immunity; Intestinal Mucosa; Intestine, Small; Permeability; Sus scrofa; Tight Junctions
PubMed: 33523589
DOI: 10.14814/phy2.14717 -
FEBS Letters Apr 2016The constitutive anabolism of cancer cells not only supports proliferation but also addicts tumor cells to a steady influx of exogenous nutrients. Limiting access to... (Review)
Review
The constitutive anabolism of cancer cells not only supports proliferation but also addicts tumor cells to a steady influx of exogenous nutrients. Limiting access to metabolic substrates could be an effective and selective means to block cancer growth. In this review, we define the pathways by which cancer cells acquire the raw materials for anabolism, highlight the actionable proteins in each pathway, and discuss the status of therapeutic interventions that disrupt nutrient acquisition. Critical open questions to be answered before apical metabolic inhibitors can be successfully and safely deployed in the clinic are also outlined. In summary, recent studies provide strong support that substrate limitation is a powerful therapeutic strategy to effectively, and safely, starve cancer cells to death.
Topics: Animals; Antineoplastic Agents; Autophagy; Caloric Restriction; Energy Metabolism; Enzyme Inhibitors; Humans; Lysosomes; Membrane Transport Modulators; Models, Biological; Neoplasm Proteins; Neoplasms; Neoplastic Stem Cells; Pinocytosis
PubMed: 26938658
DOI: 10.1002/1873-3468.12121 -
The Korean Journal of Physiology &... Jul 2022Severe bacterial infections are frequently accompanied by depressed neutrophil functions. Thus, agents that increase the microbicidal activity of neutrophils could add...
Severe bacterial infections are frequently accompanied by depressed neutrophil functions. Thus, agents that increase the microbicidal activity of neutrophils could add to a direct antimicrobial therapy. Lysophosphatidylcholine augments neutrophil bactericidal activity the glycine (Gly)/glycine receptor (GlyR) α2/TRPM2/p38 mitogen-activated protein kinase (MAPK) pathway. However, the direct effect of glycine on neutrophil bactericidal activity was not reported. In this study, the effect of glycine on neutrophil bactericidal activity was examined. Glycine augmented bactericidal activity of human neutrophils (EC = 238 μM) in a strychnine (a GlyR antagonist)-sensitive manner. Glycine augmented bacterial clearance in mice, which was also blocked by strychnine (0.4 mg/kg, s.c.). Glycine enhanced NADPH oxidase-mediated reactive oxygen species (ROS) production and TRPM2-mediated [Ca] increase in neutrophils that had taken up E. coli . Glycine augmented Lucifer yellow uptake (fluid-phase pinocytosis) and azurophil granule-phagosome fusion in neutrophils that had taken up E. coli in an SB203580 (a p38 MAPK inhibitor)-sensitive manner. These findings indicate that glycine augments neutrophil microbicidal activity by enhancing azurophil granule-phagosome fusion the GlyRα2/ROS/calcium/p38 MAPK pathway. We suggest that glycine could be a useful agent for increasing neutrophil bacterial clearance.
PubMed: 35766001
DOI: 10.4196/kjpp.2022.26.4.229 -
Journal of Virology Apr 2023Porcine enteric alphacoronavirus (PEAV) is a new bat HKU2-like porcine coronavirus, and its endemic outbreak has caused severe economic losses to the pig industry. Its...
Porcine enteric alphacoronavirus (PEAV) is a new bat HKU2-like porcine coronavirus, and its endemic outbreak has caused severe economic losses to the pig industry. Its broad cellular tropism suggests a potential risk of cross-species transmission. A limited understanding of PEAV entry mechanisms may hinder a rapid response to potential outbreaks. This study analyzed PEAV entry events using chemical inhibitors, RNA interference, and dominant-negative mutants. PEAV entry into Vero cells depended on three endocytic pathways: caveolae, clathrin, and macropinocytosis. Endocytosis requires dynamin, cholesterol, and a low pH. Rab5, Rab7, and Rab9 GTPases (but not Rab11) regulate PEAV endocytosis. PEAV particles colocalize with EEA1, Rab5, Rab7, Rab9, and Lamp-1, suggesting that PEAV translocates into early endosomes after internalization, and Rab5, Rab7, and Rab9 regulate trafficking to lysosomes before viral genome release. PEAV enters porcine intestinal cells (IPI-2I) through the same endocytic pathway, suggesting that PEAV may enter various cells through multiple endocytic pathways. This study provides new insights into the PEAV life cycle. Emerging and reemerging coronaviruses cause severe human and animal epidemics worldwide. PEAV is the first bat-like coronavirus to cause infection in domestic animals. However, the PEAV entry mechanism into host cells remains unknown. This study demonstrates that PEAV enters into Vero or IPI-2I cells through caveola/clathrin-mediated endocytosis and macropinocytosis, which does not require a specific receptor. Subsequently, Rab5, Rab7, and Rab9 regulate PEAV trafficking from early endosomes to lysosomes, which is pH dependent. The results advance our understanding of the disease and help to develop potential new drug targets against PEAV.
Topics: Virus Internalization; Alphacoronavirus; rab GTP-Binding Proteins; Endosomes; Coronavirus Infections; Hydrogen-Ion Concentration; Dynamins; Caveolae; Cholesterol; Clathrin; Pinocytosis; Vero Cells; Chlorocebus aethiops; Animals
PubMed: 36975780
DOI: 10.1128/jvi.00210-23