title: Role of Epac1, an exchange factor for Rap GTPases, in endothelial microtubule dynamics and barrier function.
abstract: Rap1 GTPase activation by its cAMP responsive nucleotide exchange factor Epac present in endothelial cells increases endothelial cell barrier function with an associated increase in cortical actin. Here, Epac1 was shown to be responsible for these actin changes and to colocalize with microtubules in human umbilical vein endothelial cells. Importantly, Epac activation with a cAMP analogue, 8-pCPT-2'O-Me-cAMP resulted in a net increase in the length of microtubules. This did not require cell-cell interactions or Rap GTPase activation, and it was attributed to microtubule growth as assessed by time-lapse microscopy of human umbilical vein endothelial cell expressing fluorophore-linked microtubule plus-end marker end-binding protein 3. An intact microtubule network was required for Epac-mediated changes in cortical actin and barrier enhancement, but it was not required for Rap activation. Finally, Epac activation reversed microtubule-dependent increases in vascular permeability induced by tumor necrosis factor-alpha and transforming growth factor-beta. Thus, Epac can directly promote microtubule growth in endothelial cells. This, together with Rap activation leads to an increase in cortical actin, which has functional significance for vascular permeability.
authors.affiliation: Center of Excellence in Vascular Biology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Seema
authors.initials: S
authors.lastname: Sehrawat
authors.forename: Xavier
authors.initials: X
authors.lastname: Cullere
authors.forename: Sunita
authors.initials: S
authors.lastname: Patel
authors.forename: Joseph
authors.initials: J
authors.lastname: Italiano
authors.forename: Tanya N
authors.initials: TN
authors.lastname: Mayadas
mesh_terms: D000199:Actins / Q000378:metabolism; D002450:Cell Communication / Q000187:drug effects; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D008870:Microtubules / Q000187:drug effects / Q000201:enzymology*; D008954:Models, Biological; D021381:Protein Transport / Q000187:drug effects; D014404:Tubulin / Q000378:metabolism; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism* / Q000502:physiology
chemical_list: C473217:8-(4-chloro-phenylthio)-2'-O-methyladenosine-3'-5'-cyclic monophosphate; D000199:Actins; D020662:Guanine Nucleotide Exchange Factors; C116122:RAPGEF3 protein, human; D014404:Tubulin; D000242:Cyclic AMP; D020827:rap1 GTP-Binding Proteins