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Event: 1539

Key Event Title

A descriptive phrase which defines a discrete biological change that can be measured. More help

Endocytotic lysosomal uptake

Short name
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Biological Context

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Level of Biological Organization

Cell term

The location/biological environment in which the event takes place.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help
Cell term
eukaryotic cell

Organ term

The location/biological environment in which the event takes place.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help

Key Event Components

The KE, as defined by a set structured ontology terms consisting of a biological process, object, and action with each term originating from one of 14 biological ontologies (Ives, et al., 2017; Biological process describes dynamics of the underlying biological system (e.g., receptor signalling).Biological process describes dynamics of the underlying biological system (e.g., receptor signaling).  The biological object is the subject of the perturbation (e.g., a specific biological receptor that is activated or inhibited). Action represents the direction of perturbation of this system (generally increased or decreased; e.g., ‘decreased’ in the case of a receptor that is inhibited to indicate a decrease in the signaling by that receptor).  Note that when editing Event Components, clicking an existing Event Component from the Suggestions menu will autopopulate these fields, along with their source ID and description.  To clear any fields before submitting the event component, use the 'Clear process,' 'Clear object,' or 'Clear action' buttons.  If a desired term does not exist, a new term request may be made via Term Requests.  Event components may not be edited; to edit an event component, remove the existing event component and create a new one using the terms that you wish to add.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help
Process Object Action
endocytosis lysosomal membrane increased

Key Event Overview

AOPs Including This Key Event

All of the AOPs that are linked to this KE will automatically be listed in this subsection. This table can be particularly useful for derivation of AOP networks including the KE.Clicking on the name of the AOP will bring you to the individual page for that AOP. More help
AOP Name Role of event in AOP Point of Contact Author Status OECD Status
lysosomal uptake induced liver fibrosis MolecularInitiatingEvent Marina Kuburic (send email) Under development: Not open for comment. Do not cite Under Review
Cellular uptake leads to intestinal barrier disruption via mitochondrial dysfunction MolecularInitiatingEvent Laure-Alix Clerbaux (send email) Under development: Not open for comment. Do not cite

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KE.In many cases, individual species identified in these structured fields will be those for which the strongest evidence used in constructing the AOP was available in relation to this KE. More help
Term Scientific Term Evidence Link
human Homo sapiens NCBI
rat Rattus norvegicus NCBI
mouse Mus musculus NCBI

Life Stages

An indication of the the relevant life stage(s) for this KE. More help
Life stage Evidence
All life stages

Sex Applicability

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Term Evidence

Key Event Description

A description of the biological state being observed or measured, the biological compartment in which it is measured, and its general role in the biology should be provided. More help

Endocytosis was discovered by the Belgian Nobel laureate Christian De Duve in 1963.

Endocytosis is a form of active transport in which molecules are transported into the cell by engulfing them in an energy-using process. In endocytosis, the material to be internalized is surrounded by an area of plasma membrane, which then buds off inside the cell to form a vesicle containing the ingested material. The ingestion of large particles (generally >250 nm in diameter) is termed phagocytosis (cell eating); phagocytosis is actin-dependent and restricted to professional phagocytes. The non-specific receptor-independent process to internalize fluids and solutes is called  pinocytosis (cell drinking; via small vesicles of about 100 nm in diameter) and found in all cells (Cooper, 2000; Alberts et al., 2002; Oh and Park, 2014).

Receptor-mediated endocytosis can be clathrin-, and caveolin-dependent; these proteins mediate the invagination of the cell membrane.

The clathrin-mediated endocytotic pathway produces small (approx. 100 nm in diameter) vesicles coated with the cytosolic protein clathrin, forming clathrin-coated pits in the plasma membrane.

Caveolae-mediated endocytosis produces small (approximately. 50 nm in diameter) caveolae, flask-shape pits in the membrane coated with the protein caveolin, derived from lipid rafts (rigid membrane microdomains enriched with phospholipids, sphingolipids, and cholesterol). Clathrin- and caveolae-independent endocytosis is further sub-classified as Arf6- dependent, flotillin-dependent, Cdc42-dependent and RhoA-dependent endocytosis (Cleal et al., 2013; Villamil Giraldo et al., 2014; Iversen et al., 2011; Sahay et al., 2010; Kirkham and Parton, 2005; Mailaender and Landfester, 2009).

Vesicles rapidly lose their coats and fuse to form larger compartments, known as endosomes.

Early endosomes are the first compartment of the endocytic pathway and receive most types of vesicles coming from the cell surface. Endocytosed material is transferred to late endosomes and further to lysosomes, vacuoles of 1-2 µm in diameter containing hydrolytic enzymes in an acid milieu. Their main task is the degradation of ingested material (Villamil Giraldo et al., 2014).

Substances that are taken up selectively into lysosomes are called lysosomotropic agents (De Duve et al., 1974). These agents tend to have both lipophilic or amphiphilic compounds with basic moieties and accumulate in the acidic intracellular compartment, where they become protonated, therefore cannot diffuse back into the cytosol and accumulate within lysosomes, a phenomenon called "acid trapping" (Villamil Giraldo et al., 2014).

Although structurally and pharmacologically diverse, lysosomotropic compounds share certain

physicochemical properties, namely a ClogP > 2 (partition coefficient of the neutral species of a compound between octanol and water) and a basic pKa (the negative base-10 logarithm of the acid dissociation constant of a solution; the lower the pKa value, the stronger the acid) between 6.5 and 11 (Nadanaciva et al., 2010; Lu et al., 2017).


How It Is Measured or Detected

A description of the type(s) of measurements that can be employed to evaluate the KE and the relative level of scientific confidence in those measurements.These can range from citation of specific validated test guidelines, citation of specific methods published in the peer reviewed literature, or outlines of a general protocol or approach (e.g., a protein may be measured by ELISA). Do not provide detailed protocols. More help
  • Lysosomal Trapping assay: A fluorescent dye, LysoTracker Red DND-99, which accumulates in lysosomes, is used for detecting lysosomotropism. There is a gradual decrease in the LysoTracker staining with increasing concentrations of lysosomotropic compounds. This assay is commercially available (Nadanaciva et al., 2011).
  • The most widespread method for studying intracellular trafficking involves attaching different fluorescent probes to the protein and nanomaterial that allows analyzing distribution of colour or fluorescence resonance energy transfer (FRET) throughout the cell compartments. The advantage of such approach is that it allows using live cell imaging by confocal microscopy (Sahay et al., 2010).
  • Cells can be transfected with constructs containing proteins that reside in specific endocytosis vesicles or intracellular organelles, which are fused with fluorescent proteins, such as the Green Fluorescent Protein (GFP) (Sahay et al., 2010).
  • Apart from confocal microscopy, the electron microscopy is also highly useful as it allows visualizing nanomaterials coupled with electron dense labels in different vesicular structures under very high resolution. Atomic Force Microscopy (AFM) has also been used recently to demonstrate the interactions of nanomaterials with the cell membrane (Sahay et al., 2010).
  • Exclusion of specific endocytosis mechanisms is a distinct and powerful technique to elucidate endocytosis. This can be achieved, for example, using various pharmacologic inhibitors of endocytosis that include chemical or biological agents or cell mutants (Sahay et al., 2010).
  • Co-localization studies of nanomaterials with specific endocytosis markers and structures “pulse-chase” design: proteins, such as transferrin or cholera toxin B (CTB), with known trafficking pathways are exposed to cells simultaneously or before the nanomaterial (“pulse”) and their inclusion or exclusion from the same vesicles is detected at different time points (“chase”) (Sahay et al., 2010).
  • Another way of studying co-localization is immunocytochemistry applied to fixed cells. This method allows employing specific antibodies to different proteins present along the endocytic vesicles and organelles (Sahay et al., 2010).
  • Transmission electron microscopy (TEM) is an appropriate technique to use for visualizing NPs inside cells, since light microscopy fails to resolve them at a single particle level. TEM is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image (Brandenberger et al., 2010; Villamil Giraldo et al., 2016).
  • Fluorescence Correlation Spectroscopy is a correlation analysis of fluctuation of the fluorescence intensity (Villamil Giraldo et al., 2016).
  • Evaluation of NP cellular uptake by confocal laser scanning microscopy (CLSM). CLSM combines high-resolution optical imaging with depth selectivity which allows optical sectioning.  The CLSM works by passing a laser beam through a light source aperture which is focused by an objective lens into a small area on the surface of the sample and an image is built up pixel-by-pixel by collecting the emitted photons from the fluorophores in the sample (Harush-Frenkel et al., 2006; Zhang and Monteiro-Riviere, 2009).
  • Fluorescence-activated cell sorter (FACS) analysis of NP cellular uptake. FACS is a specialized type of flow cytometry. It provides a method for sorting a heterogeneous mixture of biological based upon the specific light scattering and fluorescent characteristics of each cell (Harush-Frenkel et al., 2006; Zhang and Monteiro-Riviere, 2009).
  • Quantitative cellular uptake of AuNPs was performed by inductively coupled plasma mass spectrometry (ICPMS), a type of mass spectrometry capable of detecting metals and several non-metals at very low concentrations. This is achieved by ionizing the sample with inductively coupled plasma and then using a mass spectrometer to separate and quantify those ions (Ng et al., 2015).
  • We describe a single-step density gradient subcellular fractionation method combined with fluorescent detection analysis that provides a new tool for characterisation of endocytic traffic of polymer therapeutics for an understanding of intracellular trafficking pathways (Manunta et al., 2007).

Domain of Applicability

A description of the scientific basis for the indicated domains of applicability and the WoE calls (if provided).  More help

Endocytosis is an universal internalization route in eukaryotes (Dergai et al., 2016). In most animal cells, clathrin-coated pits and vesicles provide an efficient pathway for taking up specific macromolecules from the extracellular fluid (Cooper, 2000) and it is also a mechanism for uptaking extracellular molecules in plant cells (Fan et al., 2015).

The experimental studies have been done on mice in vivo, primary human and rat cells, and human and animal (rat, mouse)-derived cell lines (Harusch Fraenkel et al., 2007; Ng et al., 2015; Nadanaciva et al., 2011; Lu et al., 2017; Xie et al., 2007; Verma and Stellacci, 2010; Zhang and Monteiro-Riviere, 2009).


List of the literature that was cited for this KE description. More help
  • Alberts B, Johnson A, Lewis J, et al. Molecular Biology of the Cell. 4th edition New York: Garland Science; (2002).
  • Ashoor R, Yafawi R, Jessen B, Lu S. The Contribution of Lysosomotropism to Autophagy Perturbation. (2013) PLoS ONE 8(11): e82481
  • Brandenberger C, Clift MJ, Vanhecke D, Mühlfeld C, Stone V, Gehr P, Rothen-Rutishauser B. Intracellular imaging of nanoparticles: is it an elemental mistake to believe what you see? Part Fibre Toxicol. (2010) 7:15.
  • Brandenberger C,  Mühlfeld C,  Ali Z,  Lenz AG, Otmar Schmid,  Parak WJ, Gehr P,  Rothen-Rutishauser B. Quantitative evaluation of cellular uptake and trafficking of plain and polyethylene glycol-coated gold nanoparticles, Small. (2010) 6(15): 1669–1678.
  • Chakraborty A, Jana NR. Clathrin to Lipid Raft-Endocytosis via Controlled Surface Chemistry and Efficient Perinuclear Targeting of Nanoparticle,  J. Phys.  Chem.  Lett. (2015) 6(18): 3688-3697
  • Cleal K, He L, Watson PD, Jones AT. Endocytosis, intracellular traffic and fate of cell penetrating peptide based conjugates and nanoparticles, Curr Pharm Des. (2013)19(16):2878-94.
  • Cooper GM. The Cell: A Molecular Approach. 2nd edition. Sunderland (MA): Sinauer Associates; (2000).
  • De Duve Ch, De Barsy T, Poole B, Trouet A, Tulkens P, van Hoof F. Lysosomotropic agents, Biochemical Pharmacology, (1974)  Volume 23, 18: 2495-2510.
  • Dergai M, Iershov A, Novokhatska O, Pankivskyi S, Rynditch A. Evolutionary Changes on the Way to Clathrin-Mediated Endocytosis in Animals, Genome Biol Evol. (2016) 8(3):588-606.
  • Doherty GJ, McMahon HT.  Mechanisms of endocytosis, Annu Rev Biochem. (2009) 78:857-902.
  • Fan L, Li R, Pan J3, Ding Z4, Lin J. Endocytosis and its regulation in plants, Trends Plant Sci. (2015) 20(6):388-97.
  • Dykman LA, Khlebtsov NG. Uptake of engineered gold nanoparticles into mammalian cells. Chem Rev. (2014) 114(2):1258-88.
  • Gilleron J, Querbes W, Zeigerer A, Borodovsky A, Marsico G, Schubert U, Manygoats K, Seifert S, Andree C, Stöter M, Epstein-Barash H, Zhang L, Koteliansky V, Fitzgerald K, Fava E, Bickle M, Kalaidzidis Y, Akinc A, Maier M, Zerial M. Image-based analysis of lipid nanoparticle-mediated siRNA delivery, intracellular trafficking and endosomal escape, Nat Biotechnol. (2013) 31(7):638-46.
  • Harush-Frenkel O, Debotton N, Benita S, Altschuler Y. Targeting of nanoparticles to the clathrin-mediated endocytic pathway, Biochem Biophys Res Commun. (2007) 353(1):26-32.
  • Iversen TG, Skotland T, Sandvig K. Endocytosis and intracellular transport of nanoparticles: Present knowledge and need for future studies, Nanotoday, (2011) Volume 6, 2: 176-185.
  • Jin CY, Zhu BS, Wang XF, Lu QH. Cytotoxicity of Titanium Dioxide Nanoparticles in Mouse Fibroblast Cells, Chem Res Toxicol. (2008) 21(9):1871-7.
  • Kirkham M, Parton RG. Clathrin-independent endocytosis: new insights into caveolae and non-caveolar lipid raft carriers, Biochim Biophys Acta. (2005) 1746(3):349-63.
  • Lu F, Wu SH, Hung Y, Mou CY. Size effect on cell uptake in well-suspended, uniform mesoporous silica nanoparticles, Small. (2009) 5(12):1408-13.
  • Lu S, Sung T, Lin N, Abraham RT, Jessen BA. Lysosomal adaptation: How cells respond to lysosomotropic compounds. (2017) PLoS ONE 12(3): e0173771.
  • Mailänder V, Landfester K. Interaction of nanoparticles with cells, Biomacromolecules. (2009) 10(9):2379-400.
  • Manunta M, Izzo L, Duncan R, Jones AT. Establishment of subcellular fractionation techniques to monitor the intracellular fate of polymer therapeutics II. Identification of endosomal and lysosomal compartments in HepG2 cells combining single-step subcellular fractionation with fluorescent imaging. J Drug Target. (2007) 15(1):37-50.
  • Nadanaciva S, Lu S, Gebhard DF, Jessen BA, Pennie WD, Will Y. A high content screening assay for identifying lysosomotropic compounds, Toxicol In Vitro. (2011) 25(3):715-23.
  • Ng CT, Tang FM, Li JJ, Ong C, Yung LL, Bay BH. Clathrin-mediated endocytosis of gold nanoparticles in vitro, Anat Rec (Hoboken). (2015) 298(2):418-27.
  • Oh N, Park JH. Endocytosis and exocytosis of nanoparticles in mammalian cells, Int J Nanomedicine. (2014) 9 Suppl 1:51-63.
  • Ouedraogo G, Morliere P, Maziere C, Maziere JC, Santus R. Alteration of the Endocytotic Pathway by Photosensitization with Fluoroquinolones, Photochemistry and Photobiology, (2000) 72(4): 458–463.
  • Rejman  J, Bragonzi  A,Conese M. Role of Clathrin- and Caveolae-Mediated Endocytosis in Gene Transfer Mediated by Lipo- and Polyplexes Mol. Ther. (2005) (12): 468– 474.
  • Sahay G, Alakhova DY, Kabanov AV. Endocytosis of Nanomedicines, J Control Release. (2010) 145(3):182-95.
  • Saw WS,  Ujihara M,  Chong WY, Voon SH, Imae T,  Kiew L V,  Lee HB, Sim KS,  Chung LY. Size-dependent effect of cystine/citric acid-capped confeito-like gold nanoparticles on cellular uptake and photothermal cancer therapy, Colloids Surf B Biointerfaces. (2017) 161: 365–374.
  • Schütz I, Lopez-Hernandez T, Gao Q, Puchkov D, Jabs S, Nordmeyer D, Schmudde M, Rühl E, Graf CM, Haucke V. Lysosomal Dysfunction Caused by Cellular Accumulation of Silica Nanoparticles, J Biol Chem. (2016) 291(27):14170-84
  • van Nierop K, Muller FJ, Stap J, Van Noorden CJ, van Eijk M, de Groot C. Lysosomal destabilization contributes to apoptosis of germinal center B-lymphocytes, J Histochem Cytochem. (2006) 54(12):1425-35.
  • Verma A, Stellacci F. Effect of Surface Properties on Nanoparticle–Cell Interactions, Small. (2010) 6(1):12-21. 
  • Villamil Giraldo AM, Appelqvist H, Ederth T, Öllinger K. Lysosomotropic agents: impact on lysosomal membrane permeabilization and cell death, Biochem Soc Trans. (2014) 42(5):1460-4.
  • Villamil Giraldo AM, Fyrner T, Wennmalm S, Parikh AN, Öllinger K, Ederth T. Spontaneous Vesiculation and pH-Induced Disassembly of a Lysosomotropic Detergent: Impacts on Lysosomotropism and Lysosomal Delivery, Langmuir (2016) 32: 13566−13575.
  • Xie J, Xu Ch, Kohler N, Hou Y, Sun S. Controlled PEGylation of Monodisperse Fe3O4 Nanoparticles for Reduced Non-Specific Uptake by Macrophage Cells, Adv. Mater. (2007) 19: 3163–3166.
  • Yang L, Shang L, Nienhaus GU. Mechanistic aspects of fluorescent gold nanocluster internalization by live HeLa cells, Nanoscale. (2013) 5(4):1537-43.
  • Yang ND, Tan SH, Ng S1, Shi Y, Zhou J, Tan KS, Wong WS, Shen HM. Artesunate induces cell death in human cancer cells via enhancing lysosomal function and lysosomal degradation of ferritin, J Biol Chem. (2014) 289(48):33425-41.
  • Yu Z, Li W, Brunk UT. 3-Aminopropanal is a lysosomotropic aldehyde that causes oxidative stress and apoptosis by rupturing lysosomes, APMIS.  82003) 111(6):643-52.
  • Zhang LW, Monteiro-Riviere NA. Mechanisms of quantum dot nanoparticle cellular uptake, Toxicol Sci. (2009) 110(1):138-55.
  • Zhang S, Gao H, Bao G. Physical Principles of Nanoparticle Cellular Endocytosis, ACS Nano. (2015) 9(9):8655-71.