title: Internalization of E. coli ST mediated by guanylyl cyclase C in T84 human colon carcinoma cells.
abstract: Internalization of Escherichia coli heat-stable enterotoxin (ST) mediated by guanylyl cyclase C was examined in T84 human colon carcinoma cells. Surface-associated, receptor-bound ST was quantitatively separated from intracellular ligand employing acidic guanidine-HCl. ST was internalized in a time-, temperature-, and ligand concentration-dependent fashion only by cells specifically expressing guanylyl cyclase C. Only receptors which bound reversibly to ST appeared to mediate endocytosis. The rate of internalization of ST empirically determined in these studies was 0.23 min-1. The density of surface receptors for ST was similar at 4 degrees C and 37 degrees C, suggesting that these receptors recycle back to the cell surface following internalization of ligand. Similarly, internalized ST was rapidly cleared from the intracellular compartment following endocytosis. These studies demonstrate that ST undergoes ligand-dependent receptor-mediated endocytosis in human colon carcinoma cells.
authors.affiliation: Department of Medicine and Pharmacology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: R
authors.initials: R
authors.lastname: Urbanski
authors.forename: S L
authors.initials: SL
authors.lastname: Carrithers
authors.forename: S A
authors.initials: SA
authors.lastname: Waldman
mesh_terms: D000595:Amino Acid Sequence; D001427:Bacterial Toxins / Q000378:metabolism*; D016384:Consensus Sequence; D004705:Endocytosis; D004768:Enterotoxins / Q000378:metabolism*; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D006162:Guanylate Cyclase / Q000378:metabolism*; D006801:Humans; D007457:Iodine Radioisotopes; D007700:Kinetics; D008969:Molecular Sequence Data; D011956:Receptors, Cell Surface / Q000378:metabolism; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D018000:Receptors, Peptide / Q000378:metabolism*; D013696:Temperature; D014407:Tumor Cells, Cultured
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D007457:Iodine Radioisotopes; D011956:Receptors, Cell Surface; D018000:Receptors, Peptide; C034151:heat stable toxin (E coli); D006162:Guanylate Cyclase; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled