title: MAGP2 controls Notch via interactions with RGD binding integrins: Identification of a novel ECM-integrin-Notch signaling axis.
abstract: Canonical Notch signaling involves Notch receptor activation via interaction with cell surface bound Notch ligand. Recent findings also indicate that Notch signaling may be modulated by cross-talk with other signaling mechanisms. The ECM protein MAGP2 was previously shown to regulate Notch in a cell type dependent manner, although the molecular details of this interaction have not been dissected. Here, we report that MAGP2 cell type specific control of Notch is independent of individual Notch receptor-ligand combinations but dependent on interaction with RGD binding integrins. Overexpressed MAGP2 was found to suppress transcriptional activity from the Notch responsive Hes1 promoter activity in endothelial cells, while overexpression of a RGD→RGE MAGP2 mutant increased Notch signaling in the same cell type. This effect was not unique to MAGP2 since the RGD domain of the ECM protein EGFL7 was also found to be an important modulator of Hes1 promoter activity. Independently of MAGP2 or EGFL7, inhibition of RGD-binding integrins with soluble RGD peptides also increased accumulation of active N1ICD fragments and Notch responsive promoter activity independently of changes in Notch1, Jag1, or Dll4 expression. Finally, β1 or β3 integrin blocking antibodies also enhanced Notch signaling. Collectively, these results answer the question of how MAGP2 controls cell type dependent Notch signaling, but more importantly uncover a new mechanism to understand how extracellular matrices and cellular environments impact Notch signaling.
authors.affiliation: Department of Biology, Boise State University, Boise, ID 83725, United States.
authors.forename: Peter
authors.initials: P
authors.lastname: Deford
authors.affiliation: Department of Biology, Indiana State University, Terre Haute, IN 47809, United States.
authors.forename: Kasey
authors.initials: K
authors.lastname: Brown
authors.affiliation: Department of Biology, Indiana State University, Terre Haute, IN 47809, United States.
authors.forename: Rae Lee
authors.initials: RL
authors.lastname: Richards
authors.affiliation: Department of Biology, Indiana State University, Terre Haute, IN 47809, United States.
authors.forename: Aric
authors.initials: A
authors.lastname: King
authors.affiliation: Department of Biology, Indiana State University, Terre Haute, IN 47809, United States.
authors.forename: Kristin
authors.initials: K
authors.lastname: Newburn
authors.affiliation: Department of Biology, Boise State University, Boise, ID 83725, United States.
authors.forename: Katherine
authors.initials: K
authors.lastname: Westover
authors.affiliation: Biomolecular Sciences PhD Program, Boise State University, Boise, ID 83725, United States; Department of Biology, Boise State University, Boise, ID 83725, United States. Electronic address: AllanAlbig@boisestate.edu.
authors.forename: Allan R
authors.initials: AR
authors.lastname: Albig
mesh_terms: D003285:Contractile Proteins / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins; D009842:Oligopeptides / Q000378:metabolism*; D051880:Receptors, Notch / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D003285:Contractile Proteins; D006023:Glycoproteins; D016023:Integrins; D036341:Intercellular Signaling Peptides and Proteins; C115627:MFAP5 protein, human; D009842:Oligopeptides; D051880:Receptors, Notch; C047981:arginyl-glycyl-aspartic acid
keywords: Cell signaling; Extracellular matrix; Integrin; Notch