title: Cdc42- and Rac1-mediated endothelial lumen formation requires Pak2, Pak4 and Par3, and PKC-dependent signaling.
abstract: Rho GTPases regulate a diverse spectrum of cellular functions involved in vascular morphogenesis. Here, we show that Cdc42 and Rac1 play a key role in endothelial cell (EC) lumen and tube formation as well as in EC invasion in three-dimensional (3D) collagen matrices and that their regulation is mediated by various downstream effectors, including Pak2, Pak4, Par3 and Par6. RNAi-mediated or dominant-negative suppression of Pak2 or Pak4, two major regulators of cytoskeletal signaling downstream of Cdc42 or Rac1, markedly inhibits EC lumen and tube formation. Both Pak2 and Pak4 phosphorylation strongly correlate with the lumen formation process in a manner that depends on protein kinase C (PKC)-mediated signaling. We identify PKCepsilon and PKCzeta as regulators of EC lumenogenesis in 3D collagen matrices. Two polarity proteins, Par3 and Par6, are also required for EC lumen and tube formation, as they establish EC polarity through their association with Cdc42 and atypical PKC. In our model, disruption of any member in the Cdc42-Par3-Par6-PKCzeta polarity complex impairs EC lumen and tube formation in 3D collagen matrices. This work reveals novel regulators that control the signaling events mediating the crucial lumen formation step in vascular morphogenesis.
authors.affiliation: Department of Medical Pharmacology and Physiology, School of Medicine, Dalton Cardiovascular Research Center, University of Missouri-Columbia, Columbia, MO 65212, USA.
authors.forename: Wonshill
authors.initials: W
authors.lastname: Koh
authors.forename: Rachel D
authors.initials: RD
authors.lastname: Mahan
authors.forename: George E
authors.initials: GE
authors.lastname: Davis
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*; D054462:p21-Activated Kinases / Q000235:genetics / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; D008565:Membrane Proteins; C509689:PARD3 protein, human; D034741:RNA, Small Interfering; C116367:PAK4 protein, human; C515907:PAK2 protein, human; D054462:p21-Activated Kinases; D011493:Protein Kinase C; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein