title: Study of staphylococcal toxic shock syndrome toxin in human epithelial cell culture.
abstract: Staphylococcal toxic shock syndrome toxin (TST) inhibited growth of normal human epithelial (Chang) cells in culture, increasing the generation time 28% and 64% at concentrations of 4 X 10(-7)M and 8 X 10(-7)M, respectively. Fluorescence and electron microscopy of the cells treated with TST revealed the location of TST in the coated pits, specialized areas of the cell membrane known to contain high-affinity receptors for other polypeptide ligands. TST was labeled with 125I without detectable damage to the molecule and was shown to bind specifically to epithelial cells. A 100-fold excess of unlabeled TST inhibited binding of 125I-labeled toxin to the cells. Binding data indicated 10(4) receptor sites per cell for TST and a dissociation constant of 4 X 10(-9)M. Specific high-affinity binding of 125I-labeled TST to epithelial cells and the location of receptor sites in coated pits implies a possibility that the toxin is internalized by receptor-mediated endocytosis.
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism / Q000633:toxicity*; D002478:Cells, Cultured; D004848:Epithelium / Q000187:drug effects / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D006801:Humans; D007457:Iodine Radioisotopes; D008854:Microscopy, Electron; D011817:Rabbits; D012772:Shock, Septic / Q000209:etiology*; D013203:Staphylococcal Infections / Q000209:etiology*
chemical_list: D001427:Bacterial Toxins; D007457:Iodine Radioisotopes