title: Neovascularization in the pulmonary endothelium is regulated by the endosome: Rab4-mediated trafficking and p18-dependent signaling.
abstract: Neovascularization, the formation of new blood vessels, requires multiple processes including vascular leak, migration, and adhesion. Endosomal proteins, such as Rabs, regulate trafficking of key signaling proteins involved in neovascularization. The novel endosome protein, p18, enhances vascular endothelial (VE)-cadherin recycling from early endosome to cell junction to improve pulmonary endothelial barrier function. Since endothelial barrier integrity is vital in neovascularization, we sought to elucidate the role for endosome proteins p18 and Rab4, Rab7, and Rab9 in the process of vessel formation within the pulmonary vasculature. Overexpression of wild-type p18 (p18(wt)), but not the nonendosomal-binding mutant (p18(N39)), significantly increased lung microvascular endothelial cell migration, adhesion, and both in vitro and in vivo tube formation. Chemical inhibition of mTOR or p38 attenuated the proneovascularization role of p18(wt). Similar to the effect of p18(wt), overexpression of prorecycling wild-type (Rab4(WT)) and endosome-anchored (Rab4(Q67L)) Rab4 enhanced neovascularization processes, whereas molecular inhibition of Rab4, by using the nonendosomal-binding mutant (Rab4(S22N)) attenuated VEGF-induced neovascularization. Unlike p18, Rab4-induced neovascularization was independent of mTOR or p38 inhibition but was dependent on p18 expression. This study shows for the first time that neovascularization within the pulmonary vasculature is dependent on the prorecycling endocytic proteins Rab4 and p18.
authors.affiliation: Vascular Research Laboratory, Providence Veterans Affairs Medical Center, and Department of Medicine, Alpert Medical School of Brown University, Providence, Rhode Island havovi.chichger@anglia.ac.uk.
authors.forename: Havovi
authors.initials: H
authors.lastname: Chichger
authors.affiliation: Vascular Research Laboratory, Providence Veterans Affairs Medical Center, and Department of Medicine, Alpert Medical School of Brown University, Providence, Rhode Island.
authors.forename: Julie
authors.initials: J
authors.lastname: Braza
authors.affiliation: Vascular Research Laboratory, Providence Veterans Affairs Medical Center, and Department of Medicine, Alpert Medical School of Brown University, Providence, Rhode Island.
authors.forename: Huetran
authors.initials: H
authors.lastname: Duong
authors.affiliation: Vascular Research Laboratory, Providence Veterans Affairs Medical Center, and Department of Medicine, Alpert Medical School of Brown University, Providence, Rhode Island.
authors.forename: Myranda
authors.initials: M
authors.lastname: Stark
authors.affiliation: Vascular Research Laboratory, Providence Veterans Affairs Medical Center, and Department of Medicine, Alpert Medical School of Brown University, Providence, Rhode Island.
authors.forename: Elizabeth O
authors.initials: EO
authors.lastname: Harrington
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D011992:Endosomes / Q000235:genetics / Q000378:metabolism*; D004727:Endothelium / Q000166:cytology / Q000378:metabolism*; D008168:Lung / Q000378:metabolism*; D009154:Mutation; D018919:Neovascularization, Physiologic / Q000502:physiology*; D051381:Rats; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D020695:rab4 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; C546845:mTOR protein, rat; D058570:TOR Serine-Threonine Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020695:rab4 GTP-Binding Proteins
keywords: LAMTOR; endocytosis; endothelium; mTOR; neovascularization; p38; pulmonary