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Blood Jun 1999Lipopolysaccharide (LPS) is a mediator of inflammation and septic shock during bacterial infection. Although monocytes and macrophages are highly responsive to LPS, the...
Lipopolysaccharide (LPS) is a mediator of inflammation and septic shock during bacterial infection. Although monocytes and macrophages are highly responsive to LPS, the biological effects of LPS in these cell types are only partially understood. We decided, therefore, to investigate the influence of LPS on macrophage pinocytosis and Fc receptor-mediated endocytosis, two prominent and related macrophage effector functions. We observed that LPS did not greatly influence endocytosis in either macrophages or monocytes, but did exert a dual action on pinocytosis: at lower concentrations (0.1 to 100 ng/mL), LPS caused a decrease in pinocytosis in both macrophages and monocytes, whereas at higher LPS concentrations, enhanced pinocytosis in macrophages was observed. Detoxified LPS was two orders of magnitude less potent in producing these effects. After inhibition of the LPS receptor CD14, the LPS-induced decrease in pinocytosis was absent, and stimulation of pinocytosis at lower LPS concentrations was unmasked. We conclude that LPS can influence pinocytosis via CD14-dependent and CD14-independent signaling pathways. Furthermore, as addition of LPS to macrophages effected pinocytosis but not Fc receptor-mediated endocytosis, these two processes are independently regulated in macrophages.
Topics: Animals; Cells, Cultured; Lipopolysaccharide Receptors; Lipopolysaccharides; Macrophages; Mice; Pinocytosis; Signal Transduction
PubMed: 10339511
DOI: No ID Found -
Archives of Ophthalmology (Chicago,... Dec 1961
Topics: Animals; Cornea; Endothelium, Corneal; Pinocytosis; Rabbits
PubMed: 13887227
DOI: 10.1001/archopht.1961.00960010837011 -
Biological Research For Nursing Oct 2003Endocytosis can be separated into the categories of phagocytosis and pinocytosis. Phagocytosis can be distinguished from pinocytosis primarily by the size of particle... (Review)
Review
Endocytosis can be separated into the categories of phagocytosis and pinocytosis. Phagocytosis can be distinguished from pinocytosis primarily by the size of particle ingested and by its dependence on actin polymerization as a key step in particle ingestion. Several specific forms of pinocytosis have been identified that can be distinguished based on their dependence on clathrin or caveolin. Both clathrin- and caveolin-dependent pinocytosis appear to require the participation of dynamin to internalize the plasma membrane. Other, less well-characterized forms of pinocytosis have also been described. Although endocytosis has long been known to affect receptor density, recent studies have demonstrated that endocytosis through clathrin- and caveolin-dependent processes plays a key role in receptor-mediated signal transduction. In some cases, blockade of these processes attenuates, or even prevents, signal transduction from taking place. This information, coupled with a better understanding of endocytosis mechanisms, will help advance the field of cell biology as well as present new targets for drug development and disease treatment.
Topics: Actins; Caveolin 1; Caveolins; Clathrin; Down-Regulation; Dynamins; Endocytosis; Endosomes; Humans; Particle Size; Phagocytosis; Phosphorylation; Pinocytosis; Signal Transduction
PubMed: 14531216
DOI: 10.1177/1099800403256860 -
Chemico-biological Interactions Nov 1980Trypan blue at 50 microgram/ml stimulates the pinocytic uptake of 125I-labelled PVP, but not of colloidal 198Au or formaldehyde-denatured 125I-labelled bovine serum...
Trypan blue at 50 microgram/ml stimulates the pinocytic uptake of 125I-labelled PVP, but not of colloidal 198Au or formaldehyde-denatured 125I-labelled bovine serum albumin, by the 17.5-day rat visceral yolk sac incubated in vitro. Neither Trypan blue nor a combination of the dye with 125I-labelled PVP stimulated the rate of pinocytosis of liquid by the tissue. Trypan blue itself was shown to enter the yolk-sac cells by adsorptive pinocytosis. It is proposed that an interaction between Trypan blue and 125I-labelled PVP enables the latter substrate to enter the cells adsorptively by so-called 'piggy-back' pinocytosis.
Topics: Animals; Female; Gold Colloid, Radioactive; Pinocytosis; Povidone-Iodine; Pregnancy; Rats; Serum Albumin, Bovine; Trypan Blue; Yolk Sac
PubMed: 6253090
DOI: 10.1016/0009-2797(80)90097-6 -
Current Opinion in Cell Biology Aug 1995Receptor-mediated endocytosis via clathrin-coated vesicles is by far the best characterized example of pinocytosis. It has been suggested that clathrin-coated vesicles... (Review)
Review
Receptor-mediated endocytosis via clathrin-coated vesicles is by far the best characterized example of pinocytosis. It has been suggested that clathrin-coated vesicles mediate all pinocytosis in mammalian cells. This is still a matter of debate, however, and recent results provide strong evidence for 'clathrin-independent' pinocytic pathways. The selective regulation of these alternate endocytic pathways and the identification of receptors targeted to them provide new tools for the functional and mechanistic characterization of clathrin-independent pinocytosis.
Topics: Animals; Carbohydrate Sequence; Clathrin; Coated Vesicles; Dynamins; GTP Phosphohydrolases; Humans; Molecular Sequence Data; Pinocytosis; Up-Regulation
PubMed: 7495578
DOI: 10.1016/0955-0674(95)80015-8 -
Autophagy May 2017Macroautophagy/autophagy is vital for cellular homeostasis and helps cells respond to various stress situations. Macropinocytosis enables cells to nonselectively engulf... (Review)
Review
Macroautophagy/autophagy is vital for cellular homeostasis and helps cells respond to various stress situations. Macropinocytosis enables cells to nonselectively engulf and take up large volumes of fluid and is known to supply amino acids to cells. The stem cell-enriched limbal epithelium has the machinery necessary to carry out both autophagy and macropinocytosis; however, both processes are relatively understudied in this tissue. We have demonstrated that these processes are linked via MIR103-MIR107, a microRNA family that is limbal epithelial-preferred. Loss of MIR103-MIR107 causes the accumulation of large vacuoles that originate, in part, from a dysregulation in macropinocytosis via activation of SRC-RAS signaling. We found that these vacuoles were autophagic in nature and retained in cells due to inappropriate regulation of end-stage autophagy. Specifically, MIR103-MIR107 regulates diacylglycerol-PRKC/protein kinase C and CDK5 (cyclin dependent kinase 5) signaling, which enables DNM1 (dynamin 1) to function in vacuole clearance.
Topics: Animals; Autophagy; Epithelial Cells; Humans; MicroRNAs; Pinocytosis; Stem Cells; Vacuoles
PubMed: 28402214
DOI: 10.1080/15548627.2017.1287658 -
Seminars in Hematology Apr 1970
Review
Topics: Adenosine Triphosphate; Animals; Binding Sites; Glycolysis; Immune Sera; Immunoglobulin G; Immunoglobulin M; Leukocytes; Macrophages; Mice; Microscopy, Electron; Opsonin Proteins; Phagocytosis; Pinocytosis
PubMed: 4910218
DOI: No ID Found -
The Journal of Physiological Sciences :... Mar 2019Pinocytosis is an important fundamental cellular process that is used by the cell to transport fluid and solutes. Phosphoinositide 3-kinases (PI3Ks) regulate a diverse...
Pinocytosis is an important fundamental cellular process that is used by the cell to transport fluid and solutes. Phosphoinositide 3-kinases (PI3Ks) regulate a diverse array of dynamic membrane events. However, it is not well-understood which PI3K isoforms are involved in specific mechanisms of pinocytosis. We performed knockdown studies of endogenous PI3K isoforms and clathrin heavy chain (CHC) mediated by small interfering RNA (siRNA). The results demonstrated that the class II PI3K PI3K-C2α and PI3K-C2β, but not the class I or III PI3K, were required for pinocytosis, based on an evaluation of fluorescein-5-isothiocyanate (FITC)-dextran uptake in endothelial cells. Pinocytosis was partially dependent on both clathrin and dynamin, and both PI3K-C2α and PI3K-C2β were required for clathrin-mediated-but not clathrin-non-mediated-FITC-dextran uptake at the step leading up to its delivery to early endosomes. Both PI3K-C2α and PI3K-C2β were co-localized with clathrin-coated pits and vesicles. However, PI3K-C2β, but not PI3K-C2α, was highly co-localized with actin filament-associated clathrin-coated structures and required for actin filament formation at the clathrin-coated structures. These results indicate that PI3K-C2α and PI3K-C2β play differential, indispensable roles in clathrin-mediated pinocytosis.
Topics: Actin Cytoskeleton; Animals; Cells, Cultured; Class II Phosphatidylinositol 3-Kinases; Clathrin; Endothelial Cells; Human Umbilical Vein Endothelial Cells; Humans; Phosphatidylinositol 3-Kinases; Pinocytosis; RNA, Small Interfering
PubMed: 30374841
DOI: 10.1007/s12576-018-0644-2 -
Biological Chemistry Aug 2009The maintenance of peroxisome function depends on the formation of the peroxisomal membrane and the subsequent import of both membrane and matrix proteins. Without... (Review)
Review
The maintenance of peroxisome function depends on the formation of the peroxisomal membrane and the subsequent import of both membrane and matrix proteins. Without exception, peroxisomal matrix proteins are nuclear encoded, synthesized on free ribosomes and subsequently imported post-translationally. In contrast to other translocation systems that transport unfolded polypeptide chains, the peroxisomal import apparatus can facilitate the transport of folded and oligomeric proteins across the peroxisomal membrane. The peroxisomal protein import is mediated by cycling receptors that shuttle between the cytosol and peroxisomal lumen and depends on ATP and ubiquitin. In this brief review, we will summarize our current knowledge on the import of soluble proteins into the peroxisomal matrix.
Topics: Animals; Humans; Intracellular Membranes; Membrane Proteins; Peroxisomal Disorders; Peroxisomal Targeting Signal 2 Receptor; Peroxisome-Targeting Signal 1 Receptor; Peroxisomes; Pinocytosis; Protein Transport; Receptors, Cytoplasmic and Nuclear; Ubiquitination
PubMed: 19558328
DOI: 10.1515/BC.2009.104 -
Clinics in Chest Medicine Jun 1998The lung and heart, the vital organs, have to be protected and also have to move and change volume continuously to function. For the best protection and function of the... (Review)
Review
The lung and heart, the vital organs, have to be protected and also have to move and change volume continuously to function. For the best protection and function of the lung, the thorax is shaped almost like a bellows with the diaphragm as the moving part. Furthermore, the outer surface of the lung and the inner surface of the protective thoracic cage are covered by an elastic, serous, and lubricating membrane to form the pleural cavity. This is almost like inserting a sealed-wet and stretchable-plastic bag between the lung and the thoracic wall and diaphragm to decrease friction. The lubrication is accomplished by the facing mesothelial cells that have bushy-surface microvilli enmeshing hyaluronic acid-rich glycoproteins. The amount of fluid in the pleural cavity is regulated by the hydrostatic-osmotic pressure relationship and pleuro-lymphatic drainage. Excess fluid, large particles, and cells in the pleural cavity are removed through preformed stomas assisted by respiratory movements. The stoma is found only in the anterior lower thoracic wall and diaphragm and is like the drain of a sink. Finally, clinical and subclinical injuries of the pleura appear to occur often. Reactive mesothelial cells constantly repair the damages and keep the pleural cavity open. Without mesothelial cells, the lung cannot function properly and the pleural cavity will be quickly obliterated by fibrosis.
Topics: Animals; Epithelium; Glycoproteins; Humans; Hyaluronic Acid; Lymphatic System; Microscopy, Electron; Microvilli; Pinocytosis; Pleura; Water-Electrolyte Balance
PubMed: 9646978
DOI: 10.1016/s0272-5231(05)70074-5