Biomaterial Database

Receptor-mediated endocytosis of diphtheria toxin by cells in culture. 1982

J H Keen, and F R Maxfield, and M C Hardegree, and W H Habig

The binding and uptake of fluorescently labeled diphtheria toxin by cells in culture has been examined by using epifluorescence video intensification microscopy. Rhodamine-labeled diphtheria toxin retained significant toxicity on bioassay and in cell culture and was tested for uptake by human WI-38 and mouse 3T3 fibroblasts grown in culture. When added to cells at 37 degrees C, toxin was observed to become concentrated and internalized in discrete vesicles in both cell lines. The appearance of fluorescent clusters could be prevented by addition of excess unlabeled diphtheria toxin to the medium or by addition of ATP (which has been shown to block toxin binding to cells), indicating that the rhodamine-labeled toxin was binding to diphtheria toxin-specific cell surface binding sites. When the simultaneous uptake of rhodamine-labeled diphtheria toxin and fluorescein-labeled alpha 2-macroglobulin was monitored, the two proteins appeared in the same clusters indicating that the toxin undergoes receptor-mediated endocytosis. Despite the difference in susceptibility to diphtheria toxin of cells derived from sensitive (human) and resistant (mouse) tissues, the behavior of the rhodamine-labeled derivative in both cell lines was indistinguishable in terms of toxin required for formation of clusters or inhibition by unlabeled toxin or by ATP. These results demonstrate that diphtheria toxin-specific cell surface binding sites occur on both insensitive and sensitive cells and suggest that toxin is processed similarly by both cell types during its initial cell surface binding and internalization by this pathway. The possible involvement of this uptake system in the mechanism of action of diphtheria toxin in cells is discussed.

UI	MeSH Term	Description	Entries
D011950	Receptors, Cholinergic	Cell surface proteins that bind acetylcholine with high affinity and trigger intracellular changes influencing the behavior of cells. Cholinergic receptors are divided into two major classes, muscarinic and nicotinic, based originally on their affinity for nicotine and muscarine. Each group is further subdivided based on pharmacology, location, mode of action, and/or molecular biology.	ACh Receptor,Acetylcholine Receptor,Acetylcholine Receptors,Cholinergic Receptor,Cholinergic Receptors,Cholinoceptive Sites,Cholinoceptor,Cholinoceptors,Receptors, Acetylcholine,ACh Receptors,Receptors, ACh,Receptor, ACh,Receptor, Acetylcholine,Receptor, Cholinergic,Sites, Cholinoceptive
D011956	Receptors, Cell Surface	Cell surface proteins that bind signalling molecules external to the cell with high affinity and convert this extracellular event into one or more intracellular signals that alter the behavior of the target cell (From Alberts, Molecular Biology of the Cell, 2nd ed, pp693-5). Cell surface receptors, unlike enzymes, do not chemically alter their ligands.	Cell Surface Receptor,Cell Surface Receptors,Hormone Receptors, Cell Surface,Receptors, Endogenous Substances,Cell Surface Hormone Receptors,Endogenous Substances Receptors,Receptor, Cell Surface,Surface Receptor, Cell
D002478	Cells, Cultured	Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.	Cultured Cells,Cell, Cultured,Cultured Cell
D004167	Diphtheria Toxin	An ADP-ribosylating polypeptide produced by CORYNEBACTERIUM DIPHTHERIAE that causes the signs and symptoms of DIPHTHERIA. It can be broken into two unequal domains: the smaller, catalytic A domain is the lethal moiety and contains MONO(ADP-RIBOSE) TRANSFERASES which transfers ADP RIBOSE to PEPTIDE ELONGATION FACTOR 2 thereby inhibiting protein synthesis; and the larger B domain that is needed for entry into cells.	Corynebacterium Diphtheriae Toxin,Toxin, Corynebacterium Diphtheriae
D004351	Drug Resistance	Diminished or failed response of an organism, disease or tissue to the intended effectiveness of a chemical or drug. It should be differentiated from DRUG TOLERANCE which is the progressive diminution of the susceptibility of a human or animal to the effects of a drug, as a result of continued administration.	Resistance, Drug
D004705	Endocytosis	Cellular uptake of extracellular materials within membrane-limited vacuoles or microvesicles. ENDOSOMES play a central role in endocytosis.	Endocytoses
D005456	Fluorescent Dyes	Chemicals that emit light after excitation by light. The wave length of the emitted light is usually longer than that of the incident light. Fluorochromes are substances that cause fluorescence in other substances, i.e., dyes used to mark or label other compounds with fluorescent tags.	Flourescent Agent,Fluorescent Dye,Fluorescent Probe,Fluorescent Probes,Fluorochrome,Fluorochromes,Fluorogenic Substrates,Fluorescence Agents,Fluorescent Agents,Fluorogenic Substrate,Agents, Fluorescence,Agents, Fluorescent,Dyes, Fluorescent,Probes, Fluorescent,Substrates, Fluorogenic
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000511	alpha-Macroglobulins	Glycoproteins with a molecular weight of approximately 620,000 to 680,000. Precipitation by electrophoresis is in the alpha region. They include alpha 1-macroglobulins and alpha 2-macroglobulins. These proteins exhibit trypsin-, chymotrypsin-, thrombin-, and plasmin-binding activity and function as hormonal transporters.	Slow alpha 2-Macroglobulins,alpha 2-Acute Phase Globulins,alpha-Macrofetoproteins,45S RNP,Acute-Phase alpha 1-Protein,Slow alpha 2-Globulin,alpha 1-Acute Phase Globulin,alpha 1-Acute Phase Protein,alpha 1-Macroglobulin,alpha 2-Acute Phase Globulin,alpha-Macrofetoprotein,Acute Phase alpha 1 Protein,RNP, 45S,Slow alpha 2 Globulin,Slow alpha 2 Macroglobulins,alpha 1 Acute Phase Globulin,alpha 1 Acute Phase Protein,alpha 1 Macroglobulin,alpha 1-Protein, Acute-Phase,alpha 2 Acute Phase Globulin,alpha 2 Acute Phase Globulins,alpha 2-Globulin, Slow,alpha 2-Macroglobulins, Slow,alpha Macrofetoprotein,alpha Macrofetoproteins,alpha Macroglobulins
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia