title: Laminin-5-integrin interaction signals through PI 3-kinase and Rac1b to promote assembly of adherens junctions in HT-29 cells.
abstract: Human intestinal cell differentiation is mediated by signaling pathways that remain largely undefined. We and others have shown that cell migration and differentiation along the crypt-villus axis is associated with temporal and spatial modulations of the repertoire, as well as with the function of integrins and E-cadherins and their substrates. Cross-talk between integrin and cadherin signaling was previously described and seems to coordinate this differentiation process. Here, we report that engagement of alpha6 and, to a lesser extent, alpha3 integrin subunits after HT-29 cell adhesion on laminin 5 increases the expression of E-cadherin, which then organizes into nascent adherens junctions. We further identify that phosphoinositide 3-kinase (PI 3-kinase) activation plays a key role in this cross-talk. Indeed, integrin-dependent adhesion on laminin 5 stimulates PI 3-kinase activity. Immunofluorescence and immunoprecipitation experiments revealed that activated PI 3-kinase is recruited at cell-cell contacts. Using LY294002, an inhibitor of PI 3-kinase activity, we found that this activation is essential for E-cadherin connection with the cytoskeleton and for biogenesis of adherens junctions. Finally, we demonstrated that PI 3-kinase could signal through Rac1b activation to control adherens junction assembly. Our results provide a mechanistic insight into integrin-cadherin cross-talk and identify a novel role for PI 3-kinase in the establishment of adherens junctions.
authors.affiliation: Laboratoire d'Etude de la Différenciation et de l'Adhérence Cellulaires, UMR UJF/CNRS 5538, Institut Albert Bonniot, Faculté de Médecine de Grenoble, Domaine de la Merci, 38706 La Tronche Cedex, France.
authors.forename: Nicolas T
authors.initials: NT
authors.lastname: Chartier
authors.forename: Michèle
authors.initials: M
authors.lastname: Lainé
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Gout
authors.forename: Géraldine
authors.initials: G
authors.lastname: Pawlak
authors.forename: Christiane A
authors.initials: CA
authors.lastname: Marie
authors.forename: Paulo
authors.initials: P
authors.lastname: Matos
authors.forename: Marc R
authors.initials: MR
authors.lastname: Block
authors.forename: Muriel R
authors.initials: MR
authors.lastname: Jacquier-Sarlin
mesh_terms: D022005:Adherens Junctions / Q000378:metabolism*; D015820:Cadherins / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D048430:Cell Shape; D002867:Chromones / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D019073:HT29 Cells; D006801:Humans; D039422:Integrin alpha3 / Q000378:metabolism*; D039503:Integrin alpha6 / Q000378:metabolism*; D009025:Morpholines / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D021122:Protein Subunits / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D000097794:Kalinin
chemical_list: D015820:Cadherins; D015815:Cell Adhesion Molecules; D002867:Chromones; D004791:Enzyme Inhibitors; D039422:Integrin alpha3; D039503:Integrin alpha6; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D020830:rac1 GTP-Binding Protein; D000097794:Kalinin; C107953:RAC1 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one