title: MAGI-1 is required for Rap1 activation upon cell-cell contact and for enhancement of vascular endothelial cadherin-mediated cell adhesion.
abstract: Rap1 is a small GTPase that regulates adherens junction maturation. It remains elusive how Rap1 is activated upon cell-cell contact. We demonstrate for the first time that Rap1 is activated upon homophilic engagement of vascular endothelial cadherin (VE-cadherin) at the cell-cell contacts in living cells and that MAGI-1 is required for VE-cadherin-dependent Rap1 activation. We found that MAGI-1 localized to cell-cell contacts presumably by associating with beta-catenin and that MAGI-1 bound to a guanine nucleotide exchange factor for Rap1, PDZ-GEF1. Depletion of MAGI-1 suppressed the cell-cell contact-induced Rap1 activation and the VE-cadherin-mediated cell-cell adhesion after Ca2+ switch. In addition, relocation of vinculin from cell-extracellular matrix contacts to cell-cell contacts after the Ca2+ switch was inhibited in MAGI-1-depleted cells. Furthermore, inactivation of Rap1 by overexpression of Rap1GAPII impaired the VE-cadherin-dependent cell adhesion. Collectively, MAGI-1 is important for VE-cadherin-dependent Rap1 activation upon cell-cell contact. In addition, once activated, Rap1 upon cell-cell contacts positively regulate the adherens junction formation by relocating vinculin that supports VE-cadherin-based cell adhesion.
authors.affiliation: Department of Structural Analysis, National Cardiovascular Center Research Institute, Suita, Osaka 565-8565, Japan.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Sakurai
authors.forename: Shigetomo
authors.initials: S
authors.lastname: Fukuhara
authors.forename: Akiko
authors.initials: A
authors.lastname: Yamagishi
authors.forename: Keisuke
authors.initials: K
authors.lastname: Sako
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kamioka
authors.forename: Michitaka
authors.initials: M
authors.lastname: Masuda
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Nakaoka
authors.forename: Naoki
authors.initials: N
authors.lastname: Mochizuki
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D015820:Cadherins / Q000378:metabolism*; D002417:Cattle; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules; D015816:Cell Adhesion Molecules, Neuronal; D002460:Cell Line; D004285:Dogs; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D004789:Enzyme Activation; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D051528:Guanylate Kinases; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D009419:Nerve Tissue Proteins / Q000378:metabolism; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D015820:Cadherins; D015815:Cell Adhesion Molecules; D015816:Cell Adhesion Molecules, Neuronal; D020662:Guanine Nucleotide Exchange Factors; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C403525:RAPGEF2 protein, human; D051528:Guanylate Kinases; C113338:MAGI1 protein, human; D020827:rap1 GTP-Binding Proteins