title: Staphylococcus aureus keratinocyte invasion is mediated by integrin-linked kinase and Rac1.
abstract: Staphylococcus aureus is a major component of the skin microbiota and causes a large number of serious infections. S. aureus first interacts with epidermal keratinocytes to breach the epidermal barrier through mechanisms not fully understood. By use of primary keratinocytes from mice with epidermis-restricted Ilk gene inactivation and control integrin-linked kinase (ILK)-expressing littermates, we investigated the role of ILK in epidermal S. aureus invasion. Heat-killed, but not live, bacteria were internalized to Rab5- and Rab7-positive phagosomes, and incubation with keratinocyte growth factor increased their uptake 2.5-fold. ILK-deficient mouse keratinocytes internalized bacteria 2- to 4-fold less efficiently than normal cells. The reduced invasion by live S. aureus of ILK-deficient cells was restored in the presence of exogenous, constitutively active Rac1. Thus, Rac1 functions downstream from ILK during invasion. Further, invasion by S. aureus of Rac1-deficient cells was 2.5-fold lower than in normal cells. Paradoxically, staphylococcal cutaneous penetration of mouse skin explants with ILK-deficient epidermis was 35-fold higher than that of normal skin, indicating defects in epidermal barrier function in the absence of ILK. Thus, we identified an ILK-Rac1 pathway essential for bacterial invasion of keratinocytes, and established ILK as a key contributor to prevent invasive staphylococcal cutaneous infection.
authors.affiliation: *Department of Physiology and Pharmacology, Children's Health Research Institute and Lawson Health Research Institute, London, Ontario, Canada; and Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Samar
authors.initials: S
authors.lastname: Sayedyahossein
authors.affiliation: *Department of Physiology and Pharmacology, Children's Health Research Institute and Lawson Health Research Institute, London, Ontario, Canada; and Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Stacey X
authors.initials: SX
authors.lastname: Xu
authors.affiliation: *Department of Physiology and Pharmacology, Children's Health Research Institute and Lawson Health Research Institute, London, Ontario, Canada; and Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Alena
authors.initials: A
authors.lastname: Rudkouskaya
authors.affiliation: *Department of Physiology and Pharmacology, Children's Health Research Institute and Lawson Health Research Institute, London, Ontario, Canada; and Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: McGavin
authors.affiliation: *Department of Physiology and Pharmacology, Children's Health Research Institute and Lawson Health Research Institute, London, Ontario, Canada; and Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada.
authors.forename: John K
authors.initials: JK
authors.lastname: McCormick
authors.affiliation: *Department of Physiology and Pharmacology, Children's Health Research Institute and Lawson Health Research Institute, London, Ontario, Canada; and Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada ldagnino@uwo.ca.
authors.forename: Lina
authors.initials: L
authors.lastname: Dagnino
mesh_terms: D000818:Animals; D002469:Cell Separation; D004817:Epidermis / Q000378:metabolism; D051523:Fibroblast Growth Factor 7 / Q000378:metabolism; D005434:Flow Cytometry; D005839:Gentamicins / Q000737:chemistry; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism / Q000382:microbiology*; D051379:Mice; D064307:Microbiota; D008856:Microscopy, Fluorescence; D009479:Neuropeptides / Q000378:metabolism*; D010587:Phagocytosis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012867:Skin / Q000382:microbiology; D013203:Staphylococcal Infections / Q000378:metabolism; D013211:Staphylococcus aureus / Q000472:pathogenicity*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000378:metabolism; D020696:rab5 GTP-Binding Proteins / Q000378:metabolism; D000090802:rab7 GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D000099200:Scaffold Protein ILK
chemical_list: D051523:Fibroblast Growth Factor 7; D005839:Gentamicins; D009479:Neuropeptides; D017346:Protein Serine-Threonine Kinases; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D020691:rab GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins; D000090802:rab7 GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein; D000099200:Scaffold Protein ILK; C484602:Rac1 protein, mouse; C000716463:rab7 GTP-binding proteins, human; C000716465:rab7 GTP-binding proteins, mouse
keywords: bacterial invasion; epidermis; staphylococcal colonization