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The Journal of Cell Biology Jul 2021Actin organization underpins conserved functions at the leading edge of cells. In this issue, Yang et al. (2021. J. Cell Biol.https://doi.org/10.1083/jcb.202010096)...
Actin organization underpins conserved functions at the leading edge of cells. In this issue, Yang et al. (2021. J. Cell Biol.https://doi.org/10.1083/jcb.202010096) characterize Leep1 as a bi-functional regulator of migration and macropinocytosis through PIP3 and the Scar/WAVE complex.
Topics: Actins; Pinocytosis
PubMed: 34128957
DOI: 10.1083/jcb.202105141 -
Biomedicine & Pharmacotherapy =... Sep 2020Human epidermal growth factor receptor 2 (HER2) is overexpressed in 15-20% of patients with breast cancer. HER2 overexpression is the result of a genetic alteration and... (Review)
Review
PURPOSE
Human epidermal growth factor receptor 2 (HER2) is overexpressed in 15-20% of patients with breast cancer. HER2 overexpression is the result of a genetic alteration and this marker is associated with poor clinical outcomes. HER2-targeted therapy can significantly improve the prognosis of patients with either early or advanced HER2-positive breast cancer. One such therapy is the antibody drug conjugate (ADC) trastuzumab emtansine (T-DM1), a combination of trastuzumab and the cytotoxic antimicrotubule agent DM1. After T-DM1 binds HER2, DM1 is subsequently released into the cell. T-DM1 is generally well tolerated and has a relatively low incidence of adverse events. However, there are clinical concerns regarding T-DM1-induced high-grade thrombocytopenia.
METHODS
Here, we summarize the incidence of thrombocytopenia from several clinical trials and review experimental studies to explore the causes for T-DM1-induced thrombocytopenia. Progress in several other ADCs targeting HER2-positive breast cancer was also reviewed.
CONCLUSIONS
We conclude that T-DM1 uptake by megakaryocytes occurs through either Fcγ receptor binding or through pinocytosis, and we suggest several methods through which these processes could be interrupted to potentially improve the clinical safety of T-DM1. More generally, we recommend that toxicity should be carefully addressed during the development of ADCs.
Topics: Ado-Trastuzumab Emtansine; Animals; Antineoplastic Agents, Immunological; Breast Neoplasms; Female; Humans; Immunoconjugates; Incidence; Megakaryocytes; Pinocytosis; Receptors, IgG; Thrombocytopenia; Treatment Outcome
PubMed: 32570117
DOI: 10.1016/j.biopha.2020.110407 -
Molecular Cell Jun 2024Circular RNAs (circRNAs) are stable RNAs present in cell-free RNA, which may comprise cellular debris and pathogen genomes. Here, we investigate the phenomenon and...
Circular RNAs (circRNAs) are stable RNAs present in cell-free RNA, which may comprise cellular debris and pathogen genomes. Here, we investigate the phenomenon and mechanism of cellular uptake and intracellular fate of exogenous circRNAs. Human myeloid cells and B cells selectively internalize extracellular circRNAs. Macrophage uptake of circRNA is rapid, energy dependent, and saturable. CircRNA uptake can lead to translation of encoded sequences and antigen presentation. The route of internalization influences immune activation after circRNA uptake, with distinct gene expression programs depending on the route of RNA delivery. Genome-scale CRISPR screens and chemical inhibitor studies nominate macrophage scavenger receptor MSR1, Toll-like receptors, and mTOR signaling as key regulators of receptor-mediated phagocytosis of circRNAs, a dominant pathway to internalize circRNAs in parallel to macropinocytosis. These results suggest that cell-free circRNA serves as an "eat me" signal and danger-associated molecular pattern, indicating orderly pathways of recognition and disposal.
Topics: RNA, Circular; Humans; Macrophages; Signal Transduction; Phagocytosis; TOR Serine-Threonine Kinases; Animals; Toll-Like Receptors; B-Lymphocytes; Scavenger Receptors, Class A; Antigen Presentation; Pinocytosis; Mice
PubMed: 38761795
DOI: 10.1016/j.molcel.2024.04.022 -
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 -
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 -
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 -
Science Signaling Nov 2022The lipid kinase VPS34 orchestrates autophagy, endocytosis, and metabolism and is implicated in cancer and metabolic disease. The proximal tubule in the kidney is a key...
The lipid kinase VPS34 orchestrates autophagy, endocytosis, and metabolism and is implicated in cancer and metabolic disease. The proximal tubule in the kidney is a key metabolic organ that controls reabsorption of nutrients such as fatty acids, amino acids, sugars, and proteins. Here, by combining metabolomics, proteomics, and phosphoproteomics analyses with functional and superresolution imaging assays of mice with an inducible deficiency in proximal tubular cells, we revealed that VPS34 controlled the metabolome of the proximal tubule. In addition to inhibiting pinocytosis and autophagy, VPS34 depletion induced membrane exocytosis and reduced the abundance of the retromer complex necessary for proper membrane recycling and lipid retention, leading to a loss of fuel and biomass. Integration of omics data into a kidney cell metabolomic model demonstrated that VPS34 deficiency increased β-oxidation, reduced gluconeogenesis, and enhanced the use of glutamine for energy consumption. Furthermore, the omics datasets revealed that VPS34 depletion triggered an antiviral response that included a decrease in the abundance of apically localized virus receptors such as ACE2. VPS34 inhibition abrogated SARS-CoV-2 infection in human kidney organoids and cultured proximal tubule cells in a glutamine-dependent manner. Thus, our results demonstrate that VPS34 adjusts endocytosis, nutrient transport, autophagy, and antiviral responses in proximal tubule cells in the kidney.
Topics: Humans; Animals; Mice; Glutamine; COVID-19; SARS-CoV-2; Kidney; Nutrients; Antiviral Agents; Lipids
PubMed: 36445937
DOI: 10.1126/scisignal.abo7940