title: Endoglin promotes transforming growth factor beta-mediated Smad 1/5/8 signaling and inhibits endothelial cell migration through its association with GIPC.
abstract: Transforming growth factor beta (TGF-beta) signals through two distinct pathways to regulate endothelial cell proliferation, migration, and angiogenesis, the ALK-1/Smad 1/5/8 and ALK-5/Smad2/3 pathways. Endoglin is a co-receptor predominantly expressed in endothelial cells that participates in TGFbeta-mediated signaling with ALK-1 and ALK-5 and regulates critical aspects of cellular and biological responses. The embryonic lethal phenotype of knock-out mice because of defects in angiogenesis and disease-causing mutations resulting in human vascular diseases both support essential roles for endoglin, ALK-1, and ALK-5 in the vasculature. However, the mechanism by which endoglin mediates TGF-beta signaling through ALK-1 and ALK-5 has remained elusive. Here we describe a novel interaction between endoglin and GIPC, a scaffolding protein known to regulate cell surface receptor expression and trafficking. Co-immunoprecipitation and immunofluorescence confocal studies both demonstrate a specific interaction between endoglin and GIPC in endothelial cells, mediated by a class I PDZ binding motif in the cytoplasmic domain of endoglin. Subcellular distribution studies demonstrate that endoglin recruits GIPC to the plasma membrane and co-localizes with GIPC in a TGFbeta-independent manner, with GIPC-promoting cell surface retention of endoglin. Endoglin specifically enhanced TGF-beta1-induced phosphorylation of Smad 1/5/8, increased a Smad 1/5/8 responsive promoter, and inhibited endothelial cell migration in a manner dependent on the ability of endoglin to interact with GIPC. These studies define a novel mechanism for the regulation of endoglin signaling and function in endothelial cells and demonstrate a new role for GIPC in TGF-beta signaling.
authors.affiliation: Department of Medicine, Duke University Medical Center, Durham, North Carolina 27708, USA.
authors.forename: Nam Y
authors.initials: NY
authors.lastname: Lee
authors.forename: Bridgette
authors.initials: B
authors.lastname: Ray
authors.forename: Tam
authors.initials: T
authors.lastname: How
authors.forename: Gerard C
authors.initials: GC
authors.lastname: Blobe
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism*; D000071063:Endoglin; D042783:Endothelial Cells / Q000166:cytology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D051898:Smad1 Protein / Q000378:metabolism*; D051902:Smad5 Protein / Q000378:metabolism*; D051904:Smad8 Protein / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D015703:Antigens, CD; D002352:Carrier Proteins; C064206:ENG protein, human; D000071063:Endoglin; C502004:Eng protein, mouse; C492009:GIPC1 protein, human; C115271:Gipc1 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D011956:Receptors, Cell Surface; C497399:SMAD1 protein, human; C497797:SMAD5 protein, human; C107514:SMAD9 protein, human; D051898:Smad1 Protein; C497401:Smad1 protein, mouse; D051902:Smad5 Protein; C497798:Smad5 protein, mouse; D051904:Smad8 Protein; C491621:Smad9 protein, mouse; D016212:Transforming Growth Factor beta
references.citation: J Biol Chem. 1998 Dec 4;273(49):33011-9
references.pmid: 9830054
references.citation: J Biol Chem. 1988 Nov 15;263(32):16984-91
references.pmid: 2903157
references.citation: J Cell Physiol. 2007 Nov;213(2):484-9
references.pmid: 17620321
references.citation: J Cell Physiol. 2005 Aug;204(2):574-84
references.pmid: 15702480
references.citation: J Biol Chem. 2004 Jul 30;279(31):32858-68
references.pmid: 15148318
references.citation: Nature. 1994 Aug 4;370(6488):341-7
references.pmid: 8047140
references.citation: J Biol Chem. 1992 Sep 25;267(27):19027-30
references.pmid: 1326540
references.citation: Int J Mol Med. 2002 Jun;9(6):585-9
references.pmid: 12011974
references.citation: J Biol Chem. 2006 Sep 1;281(35):25110-23
references.pmid: 16785228
references.citation: EMBO J. 2004 Oct 13;23(20):4018-28
references.pmid: 15385967
references.citation: J Cell Biol. 1996 Jun;133(5):1109-21
references.pmid: 8655583
references.citation: Trends Cell Biol. 1994 May;4(5):172-8
references.pmid: 14731645
references.citation: J Biol Chem. 2005 Jul 29;280(30):27800-8
references.pmid: 15923183
references.citation: Science. 1999 May 28;284(5419):1534-7
references.pmid: 10348742
references.citation: J Biol Chem. 2007 Jul 20;282(29):21507-17
references.pmid: 17540773
references.citation: Blood. 2008 Jan 15;111(2):633-42
references.pmid: 17911384
references.citation: J Cell Physiol. 2002 Apr;191(1):1-16
references.pmid: 11920677
references.citation: J Clin Invest. 1999 Nov;104(10):1343-51
references.pmid: 10562296
references.citation: EMBO J. 2002 Apr 2;21(7):1743-53
references.pmid: 11927558
references.citation: Blood. 2007 Mar 1;109(5):1953-61
references.pmid: 17068149
references.citation: Annu Rev Biochem. 1998;67:753-91
references.pmid: 9759503
references.citation: J Biol Chem. 2004 Jun 25;279(26):27440-9
references.pmid: 15084601
references.citation: Development. 1999 Apr;126(8):1571-80
references.pmid: 10079220
references.citation: Proc Natl Acad Sci U S A. 2000 Mar 14;97(6):2626-31
references.pmid: 10716993
references.citation: N Engl J Med. 2000 May 4;342(18):1350-8
references.pmid: 10793168
references.citation: Mol Cell. 2003 Oct;12(4):817-28
references.pmid: 14580334
references.citation: J Cell Sci. 2007 Mar 15;120(Pt 6):964-72
references.pmid: 17311849
references.citation: EMBO J. 1997 Sep 1;16(17):5353-62
references.pmid: 9311995
references.citation: Oncogene. 2003 Sep 29;22(42):6557-63
references.pmid: 14528280
references.citation: J Biol Chem. 2002 Aug 9;277(32):29197-209
references.pmid: 12015308
references.citation: J Biol Chem. 1999 Jan 8;274(2):584-94
references.pmid: 9872992
references.citation: J Biol Chem. 2001 Oct 26;276(43):39608-17
references.pmid: 11546783