Fig 1: Model for Nrp1 Regulation of α5β1 Integrin Traffic and Function in ECs(A) At adhesive sites of ECs spreading on FN, Nrp1, via its cytoplasmic association with oligomers of the endocytic adaptor GIPC1, promotes the Rab5/Rab21-dependent internalization of active α5β1 integrin. Once endocytosed, active α5β1 is then recycled back from Nrp1-positive vesicles to the cell surface, thus favoring the dynamic rehandling of newly forming adhesion sites. GIPC1 oligomers could facilitate the association of the α5 integrin subunit with the Bin-Amphiphysin-Rvs (BAR) protein and Rab5/Rab21 interactor APPL1. Myo6 associates with and assists GIPC1 in promoting active α5β1 endocytosis and the ensuing postendocytic traffic.(B) Moreover, in adherent cells a steady endo-exocytic flow of (active) α5β1 integrins from and toward existing ECM adhesions could allow cells to rapidly adjust polarity and cell–ECM contacts in response to extracellular stimuli.(C) In addition, Myo6 can translocate to the EC nucleus, where it stimulates the RNA-polymerase-II-dependent transcription of the FN1 gene.
Fig 2: In ECs GIPC1 and Myo6 Regulate α5β1 Integrin Traffic and Function(A) Western blot analysis of protein expression in ECs silenced for human GIPC1 (sihGIPC1) or Myo6 (sihMyo6) or transfected with control siRNA (siCtl) reveals an efficient silencing of GIPC1 or Myo6 at 96 h after the second oligofection.(B) Comparison between siCtl (black) and either sihGIPC1 (red) or sihMyo6 (green) transfected ECs adhering to FN.(C) Time-course analysis reveals an impairment of both total and active α5β1 integrin internalization in ECs silenced for hGIPC1 in comparison with control cells (siCtl).(D,E) Relative quantification of time-lapse endocytosis assay (shown in (C)) of total (D) or active (E) α5β1 integrin in ECs silenced for hGIPC1.(F) Time-course analysis reveals a significant impairment of active but not total α5β1 integrin internalization in ECs silenced for hMyo6 in comparison with control cells (siCtl).(G,H) Relative quantification of time-course endocytosis assay (shown in (F)) of total (G) or active (H) α5β1 integrin in ECs silenced for hMyo6.
Supplier Page from Abcam for Anti-GIPC1 antibody