title: Potentiation of platelet-derived growth factor receptor-β signaling mediated by integrin-associated MFG-E8.
abstract: OBJECTIVE
  Pericytes/pericyte precursors produce milk fat globule-associated protein with epidermal growth factor and factor VIII-like domains (MFG-E8) in vivo, and this α(v) integrin ligand enhances angiogenesis in tumors and in oxygen-induced retinopathy in mice. Inhibition of MFG-E8 production or function attenuates platelet-derived growth factor-BB (PDGF-BB)-induced migration of pericyte/pericyte precursor-like 10T1/2 cells in vitro. Herein, we describe mechanisms by which MFG-E8 modulates PDGF-BB:PDGF receptor β (PDGFRβ) signaling in 10T1/2 cells.
  
  
  RESULTS
  Small interfering RNA depletion of MFG-E8 from 10T1/2 cells or antibody inhibition of MFG-E8 action enhanced PDGF-BB-dependent degradation of PDGFRβ and attenuated signaling. Coimmunoprecipitation revealed transient association of MFG-E8 with PDGFRβ in PDGF-BB-treated 10T1/2 cells and reduced PDGFRβ-focal adhesion kinase association in MFG-E8-depleted cells. Confocal microscopy demonstrated that MFG-E8 binding to 10T1/2 cells was RGD motif and α(v) dependent but PDGF-BB treatment independent, whereas colocalization of MFG-E8 with PDGFRβ was enhanced by PDGF-BB. Ubiquitination of PDGFRβ was also increased in MFG-E8 small interfering RNA-transfected cells.
  
  
  CONCLUSIONS
  Integrin α(v)-bound MFG-E8 associates with PDGFRβ and focal adhesion kinase after PDGF-BB treatment, results in cell surface retention of PDGFRβ, delays receptor degradation, potentiates downstream signaling, and enhances migration of 10T1/2 cells. MFG-E8 may promote angiogenesis, in part, via cell autonomous actions on pericytes or pericyte precursors that result in enhanced PDGF-BB:PDGFRβ signaling mediated via integrin-growth factor receptor cross-talk.
authors.affiliation: Dermatology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20802-1908, USA.
authors.forename: Sei-ichiro
authors.initials: S
authors.lastname: Motegi
authors.forename: Susan
authors.initials: S
authors.lastname: Garfield
authors.forename: Xu
authors.initials: X
authors.lastname: Feng
authors.forename: Miklós
authors.initials: M
authors.lastname: Sárdy
authors.forename: Mark C
authors.initials: MC
authors.lastname: Udey
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000187:drug effects / Q000378:metabolism*; D000077214:Becaplermin; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D053595:Embryonic Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism; D039564:Integrin alphaV / Q000378:metabolism*; D051379:Mice; D008809:Mice, Inbred C3H; D008894:Milk Proteins / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D023421:Models, Animal; D020286:Pericytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D010982:Platelet-Derived Growth Factor / Q000378:metabolism / Q000494:pharmacology; D020574:Proto-Oncogene Proteins c-sis; D034741:RNA, Small Interfering / Q000494:pharmacology; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D000954:Antigens, Surface; D039564:Integrin alphaV; C490919:Mfge8 protein, mouse; D008894:Milk Proteins; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D034741:RNA, Small Interfering; D000077214:Becaplermin; D020797:Receptor, Platelet-Derived Growth Factor beta; D051417:Focal Adhesion Kinase 1; C496051:Ptk2 protein, mouse; D048049:Extracellular Signal-Regulated MAP Kinases