title: Mutations in the cytoplasmic domain of the integrin beta1 chain indicate a role for endocytosis factors in bacterial internalization.
abstract: Mutations that result in defective beta1-integrin focal adhesion formation were analyzed for effects on bacterial internalization. Mutations in the cytoplasmic domain of the beta1 chain that disrupt the sequence NPIY resulted in integrins deficient in bacterial uptake. Other mutations in the beta1 chain that reduced cytoskeletal association showed enhanced bacterial uptake. Replacement of the NPIY sequence of the beta1 subunit by the endocytosis internalization sequence PPGY resulted in integrin receptors highly proficient in bacterial internalization, yet severely defective in focal contact localization. Electron microscopy indicated that coated structures associated specifically with bacteria-binding beta1-integrins, with an apparent recruitment of coated pits from ventral cell surfaces to apical surfaces corresponding to nascent bacterial phagosomes. Clathrin inhibition studies indicated a role for the adaptor molecule AP2 as well as clathrin in integrin-mediated bacterial internalization. These results indicate that association of beta1-integrins with the cytoskeleton at focal contacts interferes with integrin-mediated bacterial internalization. Also, although actin polymerization is required for bacterial uptake, clathrin is probably involved in bacterial uptake promoted by beta-1-integrins.
authors.affiliation: Howard Hughes Medical Institute, Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
authors.forename: G T
authors.initials: GT
authors.lastname: Van Nhieu
authors.forename: E S
authors.initials: ES
authors.lastname: Krukonis
authors.forename: A A
authors.initials: AA
authors.lastname: Reszka
authors.forename: A F
authors.initials: AF
authors.lastname: Horwitz
authors.forename: R R
authors.initials: RR
authors.lastname: Isberg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D001483:Base Sequence; D001692:Biological Transport; D002460:Cell Line; D002645:Chickens; D002966:Clathrin / Q000276:immunology / Q000502:physiology; D003034:Coated Pits, Cell-Membrane / Q000502:physiology* / Q000648:ultrastructure; D003593:Cytoplasm / Q000378:metabolism; D017931:DNA Primers; D004705:Endocytosis; D004926:Escherichia coli; D015870:Gene Expression; D006801:Humans; D019012:Integrin beta1 / Q000096:biosynthesis / Q000502:physiology*; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010957:Plasmids; D012486:Salmonella typhimurium; D013211:Staphylococcus aureus; D014162:Transfection; D014168:Transferrin / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D002966:Clathrin; D017931:DNA Primers; D019012:Integrin beta1; D046911:Macromolecular Substances; D014168:Transferrin