Heparin binding domain in vitronectin is required for oligomerization and thus enhances integrin mediated cell adhesion and spreading

AbstractVitronectin is a multi-functional protein found predominantly as a monomer in blood and as an oligomer in the extracellular matrix. We have dissected the minimal regions of vitronectin protein needed for effective integrin dependent cell adhesion and spreading. A fragment of vitronectin containing the RGD integrin binding site showed similar binding affinity as that of full vitronectin protein to purified integrin αvβ3 but had diminished cell adhesion and spreading function in vivo. We demonstrate that the oligomeric state of the protein is responsible for this effect. We provide compelling evidence for the involvement of the heparin binding domain of vitronectin in the oligomerization process and show that such oligomerization reinforces the activity of vitronectin in cell adhesion and spreading.Structured summaryMINT-7905703: Vn (uniprotkb:P04004) and Vn (uniprotkb:P04004) bind (MI:0407) by molecular sieving (MI:0071

Orientation and surface coverage of adsorbed fibronectin cell binding domains and bound integrin α5β1 receptors

Integrin α5β1 binds the human 9th-10th type III fibronectin domain pair (FIII9-10) to mediate cell attachment and spreading. FIII9-10 mutants with increased conformational stability (FIII9010) or highly restricted interdomain mobility (FIII9010-CC) support cell spreading to greater and lesser extents, respectively. We have used neutron reflectivity to show that the surface adsorbed layers of the wild-type and mutant proteins are remarkably different. At bulk concentrations of protein equivalent to those used in cell spreading assays, the surface coverage of FIII9-10 was 14% compared to 31% for FIII9010 and 100% for FIII9010-CC. For FIII9010-CC, three distinct transitions in the packing and orientation of the domain pair were observed. No similar transitions were observed for FIII9-10 and only a transition to bilayer was observed for FIII9010. We discuss these observations by analogy to the surface pressure area isotherm of surfactants, with reference to the electrostatic surface potentials and conformational stabilities of the domain pairs. Data for the binding of purified integrin α5β1 receptors to adsorbed FIII9010-CC were fitted with an integrin layer thickness of 130 A ° . This indicates a movement of the integrin α5β1 headpiece away from its position in the compact 'bent' conformation. Thus, neutron reflectivity should prove to be a useful technique for the determination of the averaged integrin conformation upon binding to various ligands

The CD46-Jagged1 interaction is critical for human T(H)1 immunity

CD46 is a complement regulator with important roles related to the immune response. CD46 functions as a pathogen receptor and is a potent costimulator for the induction of interferon-γ (IFN-γ)-secreting effector T helper type 1 (TH1) cells and their subsequent switch into interleukin 10 (IL-10)-producing regulatory T cells. Here we identified the Notch family member Jagged1 as a physiological ligand for CD46. Furthermore, we found that CD46 regulated the expression of Notch receptors and ligands during T cell activation and that disturbance of the CD46-Notch crosstalk impeded induction of IFN-γ and switching to IL-10. Notably, CD4+ T cells from CD46-deficient patients and patients with hypomorphic mutations in the gene encoding Jagged1 (Alagille syndrome) failed to mount appropriate T H 1 responses in vitro and in vivo, which suggested that CD46-Jagged1 crosstalk is responsible for the recurrent infections in subpopulations of these patients. © 2012 Nature America, Inc. All rights reserved