title: Regulation of TGF-β receptor hetero-oligomerization and signaling by endoglin.
abstract: Complex formation among transforming growth factor-β (TGF-β) receptors and its modulation by coreceptors represent an important level of regulation for TGF-β signaling. Oligomerization of ALK5 and the type II TGF-β receptor (TβRII) has been thoroughly investigated, both in vitro and in intact cells. However, such studies, especially in live cells, are missing for the endothelial cell coreceptor endoglin and for the ALK1 type I receptor, which enables endothelial cells to respond to TGF-β by activation of both Smad2/3 and Smad1/5/8. Here we combined immunoglobulin G-mediated immobilization of one cell-surface receptor with lateral mobility studies of a coexpressed receptor by fluorescence recovery after photobleaching (FRAP) to demonstrate that endoglin forms stable homodimers that function as a scaffold for binding TβRII, ALK5, and ALK1. ALK1 and ALK5 bind to endoglin with differential dependence on TβRII, which plays a major role in recruiting ALK5 to the complex. Signaling data indicate a role for the quaternary receptor complex in regulating the balance between TGF-β signaling to Smad1/5/8 and to Smad2/3.
authors.affiliation: Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: Leslie
authors.initials: L
authors.lastname: Pomeraniec
authors.affiliation: Department of Medicine, Duke University Medical Center, Durham, NC 27708.
authors.forename: Melissa
authors.initials: M
authors.lastname: Hector-Greene
authors.affiliation: Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Ehrlich
authors.affiliation: Department of Medicine, Duke University Medical Center, Durham, NC 27708.
authors.forename: Gerard C
authors.initials: GC
authors.lastname: Blobe
authors.affiliation: Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel henis@post.tau.ac.il.
authors.forename: Yoav I
authors.initials: YI
authors.lastname: Henis
mesh_terms: D030301:Activin Receptors, Type II / Q000378:metabolism; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D019556:COS Cells; D002522:Chlorocebus aethiops; D000071063:Endoglin; D042783:Endothelial Cells / Q000378:metabolism; D036681:Fluorescence Recovery After Photobleaching / Q000379:methods; D006801:Humans; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D000077293:Receptor, Transforming Growth Factor-beta Type I; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D015398:Signal Transduction; D051785:Smad Proteins / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism
chemical_list: D015703:Antigens, CD; C064206:ENG protein, human; D000071063:Endoglin; D011956:Receptors, Cell Surface; D018125:Receptors, Transforming Growth Factor beta; D051785:Smad Proteins; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; C425364:ACVRL1 protein, human; D030301:Activin Receptors, Type II; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625841:TGFBR1 protein, human