AKAP9 regulation of microtubule dynamics promotes Epac1-induced endothelial barrier properties.
Adhesive forces at endothelial cell-cell borders maintain vascular integrity. cAMP enhances barrier properties and controls cellular processes through protein kinase A bound to A-kinase anchoring proteins (AKAPs). It also activates exchange protein directly activated by cAMP (Epac1), an exchange factor for Ras-related protein 1 (Rap1) GTPases that promotes cadherin- and integrin-mediated adhesion through effects on the actin cytoskeleton. We demonstrate that AKAP9 facilitates the microtubule polymerization rate in endothelial cells, interacts with Epac1, and is required for Epac1-stimulated microtubule growth. AKAP9 is not required for maintaining barrier properties under steady-state conditions. Rather, it is essential when the cell is challenged to make new adhesive contacts, as is the case when Epac activation enhances barrier function through a mechanism that, surprisingly, requires integrin adhesion at cell-cell contacts. In the present study, defects in Epac-induced responses in AKAP9-silenced cells were evident despite an intact Epac-induced increase in Rap activation, cortical actin, and vascular endothelial-cadherin adhesion. We describe a pathway that integrates Epac-mediated signals with AKAP9-dependent microtubule dynamics to coordinate integrins at lateral borders.
Department of Pathology, Brigham and Women's Hospital, Boston, MA, USA.
Seema
S
Sehrawat
Thomas
T
Ernandez
Xavier
X
Cullere
Mikiko
M
Takahashi
Yoshitaka
Y
Ono
Yulia
Y
Komarova
Tanya N
TN
Mayadas
D054758:A Kinase Anchor Proteins / Q000378:metabolism*; D015153:Blotting, Western; D002448:Cell Adhesion / Q000502:physiology*; D002469:Cell Separation; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D042783:Endothelial Cells / Q000378:metabolism*; D005434:Flow Cytometry; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D020033:Protein Isoforms; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology
D054758:A Kinase Anchor Proteins; C119719:AKAP9 protein, human; D003598:Cytoskeletal Proteins; D020662:Guanine Nucleotide Exchange Factors; D020033:Protein Isoforms; C116122:RAPGEF3 protein, human