Specific autoantigens in experimental autoimmunity-associated atherosclerosis.

Higher cardiovascular morbidity in patients with a wide range of autoimmune diseases highlights the importance of autoimmunity in promoting atherosclerosis. Our purpose was to investigate the mechanisms of accelerated atherosclerosis and identified vascular autoantigens targeted by autoimmunity. We created a mouse model of autoimmunity-associated atherosclerosis by transplanting bone marrow from FcγRIIB knockout (FcRIIB(-/-)) mice into LDL receptor knockout mice. We characterized the cellular and molecular mechanisms of atherogenesis and identified specific aortic autoantigens using serologic proteomic studies. En face lesion area analysis showed more aggressive atherosclerosis in autoimmune mice compared with control mice (0.64 ± 0.12 vs 0.32 ± 0.05 mm(2); P < 0.05, respectively). At the cellular level, FcRIIB(-/-) macrophages showed significant reduction (46-72%) in phagocytic capabilities. Proteomic analysis revealed circulating autoantibodies in autoimmune mice that targeted 25 atherosclerotic lesion proteins, including essential components of adhesion complex, cytoskeleton, and extracellular matrix, and proteins involved in critical functions and pathways. Microscopic examination of atherosclerotic plaques revealed essential colocalization of autoantibodies with endothelial cells, their adherence to basement membranes, the internal elastica lamina, and necrotic cores. The new vascular autoimmunosome may be a useful target for diagnostic and immunotherapeutic interventions in autoimmunity-associated diseases that have accelerated atherosclerosis.-Merched, A. J., Daret, D., Li, L., Franzl, N., Sauvage-Merched, M. Specific autoantigens in experimental autoimmunity-associated atherosclerosis.

Kif26b controls endothelial cell polarity through the Dishevelled/Daam1-dependent planar cell polarity-signaling pathway.

Angiogenesis involves the coordinated growth and migration of endothelial cells (ECs) toward a proangiogenic signal. The Wnt planar cell polarity (PCP) pathway, through the recruitment of Dishevelled (Dvl) and Dvl-associated activator of morphogenesis (Daam1), has been proposed to regulate cell actin cytoskeleton and microtubule (MT) reorganization for oriented cell migration. Here we report that Kif26b--a kinesin--and Daam1 cooperatively regulate initiation of EC sprouting and directional migration via MT reorganization. First, we find that Kif26b is recruited within the Dvl3/Daam1 complex. Using a three-dimensional in vitro angiogenesis assay, we show that Kif26b and Daam1 depletion impairs tip cell polarization and destabilizes extended vascular processes. Kif26b depletion specifically alters EC directional migration and mislocalized MT organizing center (MTOC)/Golgi and myosin IIB cell rear enrichment. Therefore the cell fails to establish a proper front-rear polarity. Of interest, Kif26b ectopic expression rescues the siDaam1 polarization defect phenotype. Finally, we show that Kif26b functions in MT stabilization, which is indispensable for asymmetrical cell structure reorganization. These data demonstrate that Kif26b, together with Dvl3/Daam1, initiates cell polarity through the control of PCP signaling pathway-dependent activation.

The ubiquitin ligase PDZRN3 is required for vascular morphogenesis through Wnt/planar cell polarity signalling.

Development and stabilization of a vascular plexus requires the coordination of multiple signalling processes. Wnt planar cell polarity (PCP) signalling is critical in vertebrates for diverse morphogenesis events, which coordinate cell orientation within a tissue-specific plane. However, its functional role in vascular morphogenesis is not well understood. Here we identify PDZRN3, an ubiquitin ligase, and report that Pdzrn3 deficiency impairs embryonic angiogenic remodelling and postnatal retinal vascular patterning, with a loss of two-dimensional polarized orientation of the intermediate retinal plexus. Using in vitro and ex vivo Pdzrn3 loss-of-function and gain-of-function experiments, we demonstrate a key role of PDZRN3 in endothelial cell directional and coordinated extension. PDZRN3 ubiquitinates Dishevelled 3 (Dvl3), to promote endocytosis of the Frizzled/Dvl3 complex, for PCP signal transduction. These results highlight the role of PDZRN3 to direct Wnt PCP signalling, and broadly implicate this pathway in the planar orientation and highly branched organization of vascular plexuses.

Frizzled7 controls vascular permeability through the Wnt-canonical pathway and cross-talk with endothelial cell junction complexes.

AIMS: Vascular permeability is essential for the health of normal tissues and is an important characteristic of many disease states. The role of the Wnt/frizzled pathway in vascular biology has recently been reported. The objectives of this study are to analyse the role of Frizzled7 (Fzd7) receptor in the control of vascular integrity. METHODS AND RESULTS: Fzd7 is expressed in endothelial cells and accumulates at the points of cell-cell contact in association with VE-cadherin and ß-catenin, two major adherens junction molecules. To selectively delete fzd7 in the vasculature, we developed gene targeting approaches using CreLox strategy in mice. Genetic fzd7 inhibition in the endothelium increases vascular permeability in basal and factor-induced conditions. On the cellular level, fzd7 knockdown or depletion leads to an increase in paracellular permeability with a loss of adherens junction organization. These impairments are associated with a decrease in both VE-Cadherin and ß-catenin expression, a decrease in their association and an increase of tyrosine phosphorylation of VE-cadherin/ß-catenin. Fzd7 transduces a Wnt/ß-catenin signalling cascade that is required to regulate ß-catenin and canonical target gene expression. Finally, LiCl, a GSK3 inhibitor, and ß-catenin overexpression rescued endothelial integrity and adherens junction organization, induced by fzd7 deletion. CONCLUSION: These findings establish that Fzd7 is a new partner of adherens junctional complex and represents a novel molecular switch for the control of vascular permeability via activation of the Wnt-canonical pathway.