title: Redundant roles for Met docking site tyrosines and the Gab1 pleckstrin homology domain in InlB-mediated entry of Listeria monocytogenes.
abstract: The bacterial pathogen Listeria monocytogenes causes food-borne illnesses leading to gastroenteritis, meningitis, or abortion. Listeria induces its internalization into some mammalian cells through interaction of the bacterial surface protein InlB with host Met receptor tyrosine kinase. Binding of InlB leads to phosphorylation of Met and the adapter Gab1 and to activation of host phosphoinositide (PI) 3-kinase. The mammalian ligand of Met, hepatocyte growth factor, promotes cell motility and morphogenesis in a manner dependent on phosphorylation of two docking site tyrosines at positions 1349 and 1356 in the receptor's cytoplasmic tail. Here we determined if these tyrosines were essential for Listeria entry. A derivative of the human cell line T47D stably expressing a truncated Met lacking most of its cytoplasmic domain was unable to support InlB-mediated signaling or entry. Surprisingly, cells expressing mutant Met containing phenylalanine substitutions in both tyrosines 1349 and 1356 (MetYF) allowed entry and InlB-induced Gab1 phosphorylation. However, in contrast to the situation in cells expressing wild-type Met, Gab1 phosphorylation in MetYF cells required PI 3-kinase activity. The Gab1 pleckstrin homology (PH) domain was constitutively associated with the plasma membrane of cells in a PI 3-kinase-dependent manner. Overexpression of the PH domain blocked entry of Listeria into cells expressing MetYF but not into cells expressing wild-type Met. Taken together, these results indicate that the docking site tyrosines are dispensable for internalization when membrane localization of Gab1 is constitutive. Distinct pathways of recruitment by phosphorylated tyrosines in Met and PH domain ligands in the membrane are redundant for bacterial entry.
authors.affiliation: Department of Medical Genetics and Microbiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Tumay
authors.initials: T
authors.lastname: Basar
authors.forename: Yang
authors.initials: Y
authors.lastname: Shen
authors.forename: Keith
authors.initials: K
authors.lastname: Ireton
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D001426:Bacterial Proteins; D001665:Binding Sites; D001798:Blood Proteins / Q000737:chemistry; D006801:Humans; D008089:Listeria monocytogenes / Q000472:pathogenicity*; D008565:Membrane Proteins / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D010750:Phosphoproteins / Q000737:chemistry / Q000502:physiology*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt; D019859:Proto-Oncogene Proteins c-met; D017978:Receptors, Growth Factor / Q000737:chemistry / Q000502:physiology*; D014443:Tyrosine / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D001426:Bacterial Proteins; D001798:Blood Proteins; D008565:Membrane Proteins; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019859:Proto-Oncogene Proteins c-met; D017978:Receptors, Growth Factor; D014443:Tyrosine; C098587:GAB1 protein, human; C095768:inlB protein, Listeria monocytogenes; C039077:platelet protein P47; C491743:MET protein, human