Fig. 3. LOS is required for cortactin tyrosine phosphorylation but not for ErbB2 or Src kinase activation. HBMECs (starved for 24 hours) were either not infected (–) or infected for 3 hours with the wild-type (WT) or isogenic rfaC (rfaC), lgtA (lgtA), lgtE (lgtE) or mtrC (mtrC) defective mutants of the 2C43 or ROU strains of N. meningitidis, as indicated. Inocula were adjusted to obtain similar adhesion events between wild-type and mutant bacteria. After lysis, ErbB2 receptor was immunoprecipitated and immunoblotted with an anti-phosphotyrosine antibody (PY) (A, top), Src was immunoprecipitated and subjected to an in-vitro kinase assay using acid-denatured enolase as a substrate (A, middle), or cortactin was immunoprecipitated and immunoblotted with an anti-phosphotyrosine antibody and the blot was reprobed with an anti-cortactin antibody to confirm that similar protein levels were immunoprecipitated (A, bottom, B). (C) Quantification by densitometry analysis (using NIH Image software) of cortactin phosphorylation induced by the wild-type and mutants of the 2C43 strain. Average values (± s.e.m.) are presented from four independent experiments.