title: Microtubule dynamics and Rac-1 signaling independently regulate barrier function in lung epithelial cells.
abstract: Cadherin-mediated cell-cell adhesion controls the morphology and function of epithelial cells and is a critical component of the pathology of chronic inflammatory disorders. Dynamic interactions between cadherins and the actin cytoskeleton are required for stable cell-cell contact. Besides actin, microtubules also target intercellular, cadherin-based junctions and contribute to their formation and stability. Here, we studied the role of microtubules in conjunction with Rho-like GTPases in the regulation of lung epithelial barrier function using real-time monitoring of transepithelial electrical resistance. Unexpectedly, we found that disruption of microtubules promotes epithelial cell-cell adhesion. This increase in epithelial barrier function is accompanied by the accumulation of beta-catenin at cell-cell junctions, as detected by immunofluorescence. Moreover, we found that the increase in cell-cell contact, induced by microtubule depolymerization, requires signaling through a RhoA/Rho kinase pathway. The Rac-1 GTPase counteracts this pathway, because inhibition of Rac-1 signaling rapidly promotes epithelial barrier function, in a microtubule- and RhoA-independent fashion. Together, our data suggest that microtubule-RhoA-mediated signaling and Rac-1 control lung epithelial integrity through counteracting independent pathways.
authors.affiliation: Sanquin Research and Landsteiner Laboratory, Academic Medical Centre, Univ. of Amsterdam, Plesmanlaan 125, 1066 CX Amsterdam, The Netherlands.
authors.forename: Magdalena J
authors.initials: MJ
authors.lastname: Lorenowicz
authors.forename: Mar
authors.initials: M
authors.lastname: Fernandez-Borja
authors.forename: Anne-Marieke D
authors.initials: AM
authors.lastname: van Stalborch
authors.forename: Marian A J A
authors.initials: MA
authors.lastname: van Sterkenburg
authors.forename: Pieter S
authors.initials: PS
authors.lastname: Hiemstra
authors.forename: Peter L
authors.initials: PL
authors.lastname: Hordijk
mesh_terms: D000818:Animals; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D017097:Electric Impedance; D005455:Fluorescent Antibody Technique; D008168:Lung / Q000166:cytology / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000166:cytology; D020545:Respiratory Mucosa / Q000378:metabolism*; D015398:Signal Transduction; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism