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Frontiers in Immunology 2023Invariant chain (Ii, CD74) is a type II transmembrane glycoprotein that acts as a chaperone and facilitates the folding and transport of MHC II chains. By assisting the...
Invariant chain (Ii, CD74) is a type II transmembrane glycoprotein that acts as a chaperone and facilitates the folding and transport of MHC II chains. By assisting the assembly and subcellular targeting of MHC II complexes, Ii has a wide impact on the functions of antigen-presenting cells such as antigen processing, endocytic maturation, signal transduction, cell migration, and macropinocytosis. Ii is a multifunctional molecule that can alter endocytic traffic and has several interacting molecules. To understand more about Ii's function and to identify further Ii interactors, a yeast two-hybrid screening was performed. Retinoic Acid-Induced 14 (Rai14) was detected as a putative interaction partner, and the interaction was confirmed by co-immunoprecipitation. Rai14 is a poorly characterized protein, which is believed to have a role in actin cytoskeleton and membrane remodeling. In line with this, we found that Rai14 localizes to membrane ruffles, where it forms macropinosomes. Depletion of Rai14 in antigen-presenting cells delays MHC II internalization, affecting macropinocytic activity. Intriguingly, we demonstrated that, similar to Ii, Rai14 is a positive regulator of macropinocytosis and a negative regulator of cell migration, two antagonistic processes in antigen-presenting cells. This antagonism is known to depend on the interaction between myosin II and Ii. Here, we show that Rai14 also binds to myosin II, suggesting that Ii, myosin II, and Rai14 work together to coordinate macropinocytosis and cell motility.
Topics: Tretinoin; Histocompatibility Antigens Class II; Pinocytosis; Cytoskeletal Proteins; Myosin Type II
PubMed: 37545539
DOI: 10.3389/fimmu.2023.1182180 -
Philosophical Transactions of the Royal... Feb 2019In tumour cells, macropinocytosis functions as an amino acid supply route and supports cancer cell survival and proliferation. Initially demonstrated in oncogenic... (Review)
Review
In tumour cells, macropinocytosis functions as an amino acid supply route and supports cancer cell survival and proliferation. Initially demonstrated in oncogenic KRAS-driven models of pancreatic cancer, macropinocytosis triggers the internalization of extracellular proteins via discrete endocytic vesicles called macropinosomes. The incoming protein cargo is targeted for lysosome-dependent degradation, causing the intracellular release of amino acids. These protein-derived amino acids support metabolic fitness by contributing to the intracellular amino acid pools, as well as to the biosynthesis of central carbon metabolites. In this way, macropinocytosis represents a novel amino acid supply route that tumour cells use to survive the nutrient-poor conditions of the tumour microenvironment. Macropinocytosis has also emerged as an entry mechanism for a variety of nanomedicines, suggesting that macropinocytosis regulation in the tumour setting can be harnessed for the delivery of anti-cancer therapeutics. A slew of recent studies point to the possibility that macropinocytosis is a pervasive feature of many different tumour types. In this review, we focus on the role of this important uptake mechanism in a variety of cancers and highlight the main molecular drivers of macropinocytosis in these malignancies. This article is part of the Theo Murphy meeting issue 'Macropinocytosis'.
Topics: Humans; Neoplasms; Pinocytosis; Tumor Microenvironment
PubMed: 30967003
DOI: 10.1098/rstb.2018.0153 -
Sub-cellular Biochemistry 2022The distinct movements of macropinosome formation and maturation have corresponding biochemical activities which occur in a defined sequence of stages and transitions...
The distinct movements of macropinosome formation and maturation have corresponding biochemical activities which occur in a defined sequence of stages and transitions between those stages. Each stage in the process is regulated by variously phosphorylated derivatives of phosphatidylinositol (PtdIns) which reside in the cytoplasmic face of the membrane lipid bilayer. PtdIns derivatives phosphorylated at the 3' position of the inositol moiety, called 3' phosphoinositides (3'PIs), regulate different stages of the sequence. 3'PIs are synthesized by numerous phosphoinositide 3'-kinases (PI3K) and other lipid kinases and phosphatases, which are themselves regulated by small GTPases of the Ras superfamily. The combined actions of these enzymes localize four principal species of 3'PI to distinct domains of the plasma membrane or to discrete organelles, with distinct biochemical activities confined to those domains. Phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P) and phosphatidylinositol (3,4)-bisphosphate (PtdIns(3,4)P) regulate the early stages of macropinosome formation, which include cell surface ruffling and constrictions of circular ruffles which close into macropinosomes. Phosphatidylinositol 3-phosphate (PtdIns3P) regulates macropinosome fusion with other macropinosomes and early endocytic organelles. Phosphatidylinositol (3,5)-bisphosphate (PtdIns(3,5)P) mediates macropinosome maturation and shrinkage, through loss of ions and water, and subsequent traffic to lysosomes. The different characteristic rates of macropinocytosis in different cell types indicate levels of regulation which may be governed by the cell's capacity to generate 3'PIs.
Topics: Cell Membrane; Endosomes; Phosphatidylinositols; Phosphoric Monoester Hydrolases; Pinocytosis
PubMed: 35378706
DOI: 10.1007/978-3-030-94004-1_7 -
Arteriosclerosis, Thrombosis, and... Sep 2020Macrophages are immune cells, capable to remodel the extracellular matrix, which can harbor extracellular DNA incorporated into neutrophil extracellular traps (NETs). To... (Comparative Study)
Comparative Study
OBJECTIVE
Macrophages are immune cells, capable to remodel the extracellular matrix, which can harbor extracellular DNA incorporated into neutrophil extracellular traps (NETs). To study the breakdown of NETs we studied the capability of macrophage subsets to degrade these structures in vitro and in vivo in a murine thrombosis model. Furthermore, we analyzed human abdominal aortic aneurysm samples in support of our in vitro and in vivo results. Approach and Results: Macrophages were seeded onto blood clots or isolated NETs and polarized. All macrophages were capable to degrade NETs. For initial breakdown, macrophages relied on extracellular deoxyribonucleases. Proinflammatory polarization enhanced NET degradation. The boost in degradation was because of increased macropinocytosis, as inhibition by imipramine diminished their NET breakdown. Inhibition of macropinocytosis in a murine thrombosis model led to increased NET burden and reduced thrombus resolution in vivo. When analyzing abdominal aortic aneurysm samples, macrophage density furthermore corresponded negatively with the amount of local NETs in the intraluminal thrombi as well as in the vessel wall, as increased macrophage density was associated with a reduction in NET burden.
CONCLUSIONS
We provide evidence that macrophages degrade NETs by extracellular predigestion and subsequent uptake. Furthermore, we show that proinflammatory macrophages increase NET degradation through enhanced macropinocytosis, priming them for NET engulfment. Based on our findings, that inhibition of macropinocytosis in mice corresponded to increased NET amounts in thrombi and that local macrophage density in human abdominal aortic aneurysm is negatively associated with surrounding NETs, we hypothesize, that macrophages are able to degrade NETs in vivo.
Topics: Animals; Aortic Aneurysm, Abdominal; Cells, Cultured; Deoxyribonuclease I; Deoxyribonucleases; Disease Models, Animal; Endodeoxyribonucleases; Exodeoxyribonucleases; Extracellular Traps; Female; Humans; Imipramine; Interferon-gamma; Interleukin-13; Interleukin-4; Kinetics; Lipopolysaccharides; Macrophage Activation; Macrophages; Mice; Mice, Inbred C57BL; Muscle Proteins; Neutrophils; Phagocytosis; Phenotype; Phosphoproteins; Pinocytosis; Vena Cava, Inferior; Venous Thrombosis
PubMed: 32673525
DOI: 10.1161/ATVBAHA.120.314883 -
Molecules (Basel, Switzerland) Sep 2020The control of leishmaniases, a complex parasitic disease caused by the protozoan parasite , requires continuous innovation at the therapeutic and vaccination levels.... (Review)
Review
The control of leishmaniases, a complex parasitic disease caused by the protozoan parasite , requires continuous innovation at the therapeutic and vaccination levels. Chitosan is a biocompatible polymer administrable via different routes and possessing numerous qualities to be used in the antileishmanial strategies. This review presents recent progress in chitosan research for antileishmanial applications. First data on the mechanism of action of chitosan revealed an optimal in vitro intrinsic activity at acidic pH, high-molecular-weight chitosan being the most efficient form, with an uptake by pinocytosis and an accumulation in the parasitophorous vacuole of -infected macrophages. In addition, the immunomodulatory effect of chitosan is an added value both for the treatment of leishmaniasis and the development of innovative vaccines. The advances in chitosan chemistry allows pharmacomodulation on amine groups opening various opportunities for new polymers of different size, and physico-chemical properties adapted to the chosen routes of administration. Different formulations have been studied in experimental leishmaniasis models to cure visceral and cutaneous leishmaniasis, and chitosan can act as a booster through drug combinations with classical drugs, such as amphotericin B. The various architectural possibilities given by chitosan chemistry and pharmaceutical technology pave the way for promising further developments.
Topics: Amphotericin B; Animals; Antimony; Antiprotozoal Agents; Biocompatible Materials; Chitosan; Curcumin; Drug Carriers; Drug Compounding; Humans; Hydrogen-Ion Concentration; Leishmaniasis; Leishmaniasis Vaccines; Macrophages; Nanoparticles; Paromomycin; Pentacyclic Triterpenes; Polymers; Rifampin; Selenium; Thiomalates; Titanium; Triterpenes; Betulinic Acid; Ursolic Acid
PubMed: 32916994
DOI: 10.3390/molecules25184123 -
International Journal of Molecular... Feb 2023Endocytosis in mammalian cells is a fundamental cellular machinery that regulates vital physiological processes, such as the absorption of metabolites, release of... (Review)
Review
Endocytosis in mammalian cells is a fundamental cellular machinery that regulates vital physiological processes, such as the absorption of metabolites, release of neurotransmitters, uptake of hormone cellular defense, and delivery of biomolecules across the plasma membrane. A remarkable characteristic of the endocytic machinery is the sequential assembly of the complex proteins at the plasma membrane, followed by internalization and fusion of various biomolecules to different cellular compartments. In all eukaryotic cells, functional characterization of endocytic pathways is based on dynamics of the protein complex and signal transduction modules. To coordinate the assembly and functions of the numerous parts of the endocytic machinery, the endocytic proteins interact significantly within and between the modules. Clathrin-dependent and -independent endocytosis, caveolar pathway, and receptor mediated endocytosis have been attributed to a greater variety of physiological and pathophysiological roles such as, autophagy, metabolism, cell division, apoptosis, cellular defense, and intestinal permeabilization. Notably, any defect or alteration in the endocytic machinery results in the development of pathological consequences associated with human diseases such as cancer, cardiovascular diseases, neurological diseases, and inflammatory diseases. In this review, an in-depth endeavor has been made to illustrate the process of endocytosis, and associated mechanisms describing pathological manifestation associated with dysregulated endocytosis machinery.
Topics: Animals; Humans; Endocytosis; Caveolae; Cell Membrane; Signal Transduction; Biological Transport; Mammals
PubMed: 36769293
DOI: 10.3390/ijms24032971 -
Seminars in Cell & Developmental Biology Jul 2017A seamless tube is a very narrow-bore tube that is composed of a single cell with an intracellular lumen and no adherens or tight junctions along its length. Many... (Review)
Review
A seamless tube is a very narrow-bore tube that is composed of a single cell with an intracellular lumen and no adherens or tight junctions along its length. Many capillaries in the vertebrate vascular system are seamless tubes. Seamless tubes also are found in invertebrate organs, including the Drosophila trachea and the Caenorhabditis elegans excretory system. Seamless tube cells can be less than a micron in diameter, and they can adopt very simple "doughnut-like" shapes or very complex, branched shapes comparable to those of neurons. The unusual topology and varied shapes of seamless tubes raise many basic cell biological questions about how cells form and maintain such structures. The prevalence of seamless tubes in the vascular system means that answering such questions has significant relevance to human health. In this review, we describe selected examples of seamless tubes in animals and discuss current models for how seamless tubes develop and are shaped, focusing particularly on insights that have come from recent studies in Drosophila and C. elegans.
Topics: Animals; Caenorhabditis elegans; Capillaries; Cell Polarity; Cytoskeletal Proteins; Drosophila melanogaster; Endothelial Cells; Epithelial Cells; Exocytosis; Gene Expression Regulation; Humans; Models, Biological; Morphogenesis; Pinocytosis; Trachea; Vascular Diseases
PubMed: 27178486
DOI: 10.1016/j.semcdb.2016.05.006 -
Endocrine-related Cancer Dec 2019Genomic changes that drive cancer initiation and progression contribute to the co-evolution of the adjacent stroma. The nature of the stromal reprogramming involves... (Review)
Review
Genomic changes that drive cancer initiation and progression contribute to the co-evolution of the adjacent stroma. The nature of the stromal reprogramming involves differential DNA methylation patterns and levels that change in response to the tumor and systemic therapeutic intervention. Epigenetic reprogramming in carcinoma-associated fibroblasts are robust biomarkers for cancer progression and have a transcriptional impact that support cancer epithelial progression in a paracrine manner. For prostate cancer, promoter hypermethylation and silencing of the RasGAP, RASAL3 that resulted in the activation of Ras signaling in carcinoma-associated fibroblasts. Stromal Ras activity initiated a process of macropinocytosis that provided prostate cancer epithelia with abundant glutamine for metabolic conversion to fuel its proliferation and a signal to transdifferentiate into a neuroendocrine phenotype. This epigenetic oncogenic metabolic/signaling axis seemed to be further potentiated by androgen receptor signaling antagonists and contributed to therapeutic resistance. Intervention of stromal signaling may complement conventional therapies targeting the cancer cell.
Topics: Animals; Cancer-Associated Fibroblasts; Cell Differentiation; Chromatin; DNA Methylation; Epigenesis, Genetic; Histones; Humans; Neoplasms; Pinocytosis
PubMed: 31627186
DOI: 10.1530/ERC-19-0347 -
Experimental and Therapeutic Medicine Jun 2022Water-soluble polysaccharide isolated from soybean hull and fractionated using ion-exchange chromatography were investigated to determine their molecular characteristics...
Water-soluble polysaccharide isolated from soybean hull and fractionated using ion-exchange chromatography were investigated to determine their molecular characteristics and immunostimulating activity. In the present study, soybean hull polysaccharide (SHP) was separated and purified to obtain three main fractions (F1, F2 and F3), and their chemical and monosaccharide compositions were analyzed. SHP was mainly composed of carbohydrates (64.3%), proteins (16.2%) and sulfates (12.5%), with minor levels of uronic acid (3.2%), and predominantly contained glucose and mannose as monosaccharides. Moreover, when compared with cells treated with RPMI medium, SHP was revealed to promote the proliferation and pinocytosis of RAW264.7 cells, and to enhance the production of nitric oxide (NO), tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6. Furthermore, flow cytometry demonstrated that CD11b and CD40 were involved in the immune regulation of RAW264.7 cells by SHP. Moreover, western blotting and other experiments revealed that SHP, a type of pathogen-associated molecular pattern, was specifically recognized by the Toll-like receptor 2, which, in turn, upregulated the expression levels of proteins downstream of the mitogen-activated protein kinase and nuclear factor κB pathways. Notably, the immune activity of the F2 fraction was markedly higher than that of the crude polysaccharides. In summary, the purified F2 fraction of SHP may be an effective nutritional supplement for human disorders associated with low immunity.
PubMed: 35495602
DOI: 10.3892/etm.2022.11316 -
Cells Aug 2020Amino acid metabolism promotes cancer cell proliferation and survival by supporting building block synthesis, producing reducing agents to mitigate oxidative stress, and... (Review)
Review
Amino acid metabolism promotes cancer cell proliferation and survival by supporting building block synthesis, producing reducing agents to mitigate oxidative stress, and generating immunosuppressive metabolites for immune evasion. Malignant cells rewire amino acid metabolism to maximize their access to nutrients. Amino acid transporter expression is upregulated to acquire amino acids from the extracellular environment. Under nutrient depleted conditions, macropinocytosis can be activated where proteins from the extracellular environment are engulfed and degraded into the constituent amino acids. The demand for non-essential amino acids (NEAAs) can be met through de novo synthesis pathways. Cancer cells can alter various signaling pathways to boost amino acid usage for the generation of nucleotides, reactive oxygen species (ROS) scavenging molecules, and oncometabolites. The importance of amino acid metabolism in cancer proliferation makes it a potential target for therapeutic intervention, including via small molecules and antibodies. In this review, we will delineate the targets related to amino acid metabolism and promising therapeutic approaches.
Topics: Amino Acid Transport Systems; Amino Acids; Animals; Antineoplastic Agents; Cell Proliferation; Humans; Molecular Targeted Therapy; Neoplasms; Oxidative Stress; Pinocytosis; Reactive Oxygen Species; Signal Transduction
PubMed: 32824193
DOI: 10.3390/cells9081904