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A collagen IV–derived peptide disrupts α5β1 integrin and potentiates Ang2/Tie2 signaling
Adam C. Mirando, … , Aleksander S. Popel, Niranjan B. Pandey
Adam C. Mirando, … , Aleksander S. Popel, Niranjan B. Pandey
Published January 22, 2019
Citation Information: JCI Insight. 2019;4(4):e122043. https://doi.org/10.1172/jci.insight.122043.
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Research Article Ophthalmology Vascular biology

A collagen IV–derived peptide disrupts α5β1 integrin and potentiates Ang2/Tie2 signaling

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Abstract

The angiopoietin (Ang)/Tie2 signaling pathway is essential for maintaining vascular homeostasis, and its dysregulation is associated with several diseases. Interactions between Tie2 and α5β1 integrin have emerged as part of this control; however, the mechanism is incompletely understood. AXT107, a collagen IV–derived peptide, has strong antipermeability activity and has enabled the elucidation of this previously undetermined mechanism. Previously, AXT107 was shown to inhibit VEGFR2 and other growth factor signaling via receptor tyrosine kinase association with specific integrins. AXT107 disrupts α5β1 and stimulates the relocation of Tie2 and α5 to cell junctions. In the presence of Ang2 and AXT107, junctional Tie2 is activated, downstream survival signals are upregulated, F-actin is rearranged to strengthen junctions, and, as a result, endothelial junctional permeability is reduced. These data suggest that α5β1 sequesters Tie2 in nonjunctional locations in endothelial cell membranes and that AXT107-induced disruption of α5β1 promotes clustering of Tie2 at junctions and converts Ang2 into a strong agonist, similar to responses observed when Ang1 levels greatly exceed those of Ang2. The potentiation of Tie2 activation by Ang2 even extended to mouse models in which AXT107 induced Tie2 phosphorylation in a model of hypoxia and inhibited vascular leakage in an Ang2-overexpression transgenic model and an LPS-induced inflammation model. Because Ang2 levels are very high in ischemic diseases, such as diabetic macular edema, neovascular age-related macular degeneration, uveitis, and cancer, targeting α5β1 with AXT107 provides a potentially more effective approach to treat these diseases.

Authors

Adam C. Mirando, Jikui Shen, Raquel Lima e Silva, Zenny Chu, Nicholas C. Sass, Valeria E. Lorenc, Jordan J. Green, Peter A. Campochiaro, Aleksander S. Popel, Niranjan B. Pandey

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Figure 8

Model for AXT107-mediated activation of Tie2.

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Model for AXT107-mediated activation of Tie2.
Top: In diseased neovascul...
Top: In diseased neovasculature (1) the lack of pericyte coverage skews the ratio of angiopoietins towards Ang2, which (2) weakly activates Tie2 in complex with integrin α5β1 heterodimers at the cell-ECM interface, (3) preferentially activating proliferative signals (i.e., ERK1/2). (4) The MLC kinase (MLCK) phosphorylates MLC2 and leads to formation of radial actin stress fibers within the cell and tension at EC-EC junctions. Bottom: In the presence of AXT107 (5) a fraction of α5 integrin separates from β1 integrin and (6) migrates to EC-EC junctions along with Tie2 to form large complexes and trans-interactions across junctions. (7) These complexes potentiate the phosphorylation of Tie2 by Ang2, thereby activating Akt-mediated survival pathways while maintaining basal levels of phospho-ERK1/2. (8) Additionally, MLC phosphatase is activated via the RAP1 or RAC1 pathway, which leads to reduced MLC2 activity, increased cortical actin, and stabilized junctions.

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ISSN 2379-3708

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