title: PAK1 modulates a PPARγ/NF-κB cascade in intestinal inflammation.
abstract: P21-activated kinases (PAKs) are multifunctional effectors of Rho GTPases with both kinase and scaffolding activity. Here, we investigated the effects of inflammation on PAK1 signaling and its role in colitis-driven carcinogenesis. PAK1 and p-PAK1 (Thr423) were assessed by immunohistochemistry, immunofluorescence, and Western blot. C57BL6/J wildtype mice were treated with a single intraperitoneal TNFα injection. Small intestinal organoids from these mice and from PAK1-KO mice were cultured with TNFα. NF-κB and PPARγ were analyzed upon PAK1 overexpression and silencing for transcriptional/translational regulation. PAK1 expression and activation was increased on the luminal intestinal epithelial surface in inflammatory bowel disease and colitis-associated cancer. PAK1 was phosphorylated upon treatment with IFNγ, IL-1β, and TNFα. In vivo, mice administered with TNFα showed increased p-PAK1 in intestinal villi, which was associated with nuclear p65 and NF-κB activation. p65 nuclear translocation downstream of TNFα was strongly inhibited in PAK1-KO small intestinal organoids. PAK1 overexpression induced a PAK1-p65 interaction as visualized by co-immunoprecipitation, nuclear translocation, and increased NF-κB transactivation, all of which were impeded by kinase-dead PAK1. Moreover, PAK1 overexpression downregulated PPARγ and mesalamine recovered PPARγ through PAK1 inhibition. On the other hand PAK1 silencing inhibited NF-κB, which was recovered using BADGE, a PPARγ antagonist. Altogether these data demonstrate that PAK1 overexpression and activation in inflammation and colitis-associated cancer promote NF-κB activity via suppression of PPARγ in intestinal epithelial cells.
authors.affiliation: Medical University of Vienna, Department of Internal Medicine III, Division of Gastroenterology and Hepatology, Christian Doppler Laboratory for Molecular Cancer Chemoprevention, Vienna, Austria.
authors.forename: Kyle
authors.initials: K
authors.lastname: Dammann
authors.affiliation: Medical University of Vienna, Department of Internal Medicine III, Division of Gastroenterology and Hepatology, Christian Doppler Laboratory for Molecular Cancer Chemoprevention, Vienna, Austria.
authors.forename: Vineeta
authors.initials: V
authors.lastname: Khare
authors.affiliation: Medical University of Vienna, Department of Internal Medicine III, Division of Gastroenterology and Hepatology, Christian Doppler Laboratory for Molecular Cancer Chemoprevention, Vienna, Austria.
authors.forename: Michaela
authors.initials: M
authors.lastname: Lang
authors.affiliation: Medical University of Vienna, Department of Internal Medicine III, Division of Gastroenterology and Hepatology, Hans Popper Laboratory for Molecular Hepatology, Vienna, Austria.
authors.forename: Thierry
authors.initials: T
authors.lastname: Claudel
authors.affiliation: Medical University of Vienna, Department of Internal Medicine III, Division of Gastroenterology and Hepatology, Christian Doppler Laboratory for Molecular Cancer Chemoprevention, Vienna, Austria.
authors.forename: Felix
authors.initials: F
authors.lastname: Harpain
authors.affiliation: Medical University of Vienna, Department of Internal Medicine III, Division of Gastroenterology and Hepatology, Christian Doppler Laboratory for Molecular Cancer Chemoprevention, Vienna, Austria.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Granofszky
authors.affiliation: Medical University of Vienna, Department of Internal Medicine III, Division of Gastroenterology and Hepatology, Christian Doppler Laboratory for Molecular Cancer Chemoprevention, Vienna, Austria.
authors.forename: Rayko
authors.initials: R
authors.lastname: Evstatiev
authors.affiliation: Department of Gastroenterology, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Williams
authors.affiliation: Department of Gastroenterology, University of Liverpool, Liverpool, United Kingdom.
authors.forename: D Mark
authors.initials: DM
authors.lastname: Pritchard
authors.affiliation: Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich, United Kingdom.
authors.forename: Alastair
authors.initials: A
authors.lastname: Watson
authors.affiliation: Medical University of Vienna, Department of Internal Medicine III, Division of Gastroenterology and Hepatology, Christian Doppler Laboratory for Molecular Cancer Chemoprevention, Vienna, Austria. Electronic address: christoph.gasche@meduniwien.ac.at.
authors.forename: Christoph
authors.initials: C
authors.lastname: Gasche
mesh_terms: D000818:Animals; D002460:Cell Line; D003092:Colitis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007249:Inflammation / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D015212:Inflammatory Bowel Diseases / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D007413:Intestinal Mucosa / Q000378:metabolism*; D007414:Intestinal Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D007422:Intestines / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D047495:PPAR gamma / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D054462:p21-Activated Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D016328:NF-kappa B; D009363:Neoplasm Proteins; D047495:PPAR gamma; C515903:PAK1 protein, human; C515905:Pak1 protein, mouse; D054462:p21-Activated Kinases
keywords: Colitis-associated cancer; Inflammation; NF-κB; PAK1; PPARγ; Ulcerative colitis