Ligand-independent Tie2 Dimers Mediate Kinase Activity Stimulated by High Dose Angiopoietin-1

Yamakawa, Daishi; Kidoya, Hiroyasu; Sakimoto, Susumu; Jia, Wei‐Hua; Naito, Hisamichi; Takakura, Nobuyuki

doi:10.1074/jbc.m112.433979

Cited by 12 publications

(10 citation statements)

References 37 publications

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“…Orientational restriction will further enhance interactions between receptors in the membrane (27), and, by analogy with other RTKs, additional regions are likely to cooperate in driving Tie2 dimerization (13). Consistent with this suggestion, immunogold electron microscopy (35) and bimolecular fluorescence complementation (BiFC) assays (36) have argued that Tie2 forms ligand-independent dimers in the membranes of both endothelial cells and HEK-293 cells. Our crystal structure of FNIIIa-c suggests two possible modes of FNIII domainmediated dimerization (Fig.…”

Section: Discussionmentioning

confidence: 53%

Dimerization of Tie2 mediated by its membrane-proximal FNIII domains

Moore

Lemmon

Ferguson

2017

Proc. Natl. Acad. Sci. U.S.A.

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Tie1 and Tie2, members of the tyrosine kinase family with immunoglobulin and EGF homology domains, are receptor tyrosine kinases found primarily in endothelial cells with key roles in development and maintenance of the vasculature and in angiogenesis. They are attractive targets for therapeutic intervention in tumor angiogenesis, inflammation, and sepsis. Tie2 is regulated directly by the multimeric angiopoietin (Ang) ligands, with Ang1 being its primary activator. Structural studies have shown how Angs bind to the Tie2 ligand-binding region, but do not explain Tie2 activation and suggest a passive role for the Tie2 extracellular region (ECR) in ligand-induced receptor dimerization. Here we show that the Tie2 ECR forms strong dimers even in the absence of bound ligand. Dimerization is mediated by membrane-proximal fibronectin type III (FNIII) domains that were omitted in previous structural studies. We describe a 2.5-Å resolution X-ray crystal structure of the membrane-proximal three Tie2 FNIII domains, Tie2(FNIIIa-c), revealing two possible dimerization modes that primarily involve the third FNIII domain, FNIIIc. Mutating these dimer interfaces implicates one of them (dimer 1) in soluble Tie2 (sTie2) dimerization in solution but suggests that both could play a role in Ang1-induced Tie2 activation, possibly modulated by Tie1. Through small-angle X-ray scattering studies of sTie2 dimers in solution and modeling based on crystal structures, we suggest that Ang1 binding may cross-link Tie2 dimers into higher-order oligomers, potentially explaining how Tie2 is differentially clustered following ligand engagement in different cellular contexts. Our results also firmly implicate FNIII domain-mediated interactions in Tie2 activation, identifying a potential Achilles' heel for therapeutic inhibition.receptor tyrosine kinase | dimerization | angiopoietin | Tie | crystallography

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Section: Discussionmentioning

confidence: 53%

Dimerization of Tie2 mediated by its membrane-proximal FNIII domains

Moore

Lemmon

Ferguson

2017

Proc. Natl. Acad. Sci. U.S.A.

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“…Premature dimerization of insulin receptors leads to less efficient maturation and intracellular retention of dimeric or aggregated receptors (24). In addition, bimolecular fluorescence complementation assays in transfected HEK293T cells indicate that TIE2-R849W may ligand-independently form dimers more efficiently than TIE2-WT (28). To investigate if prematurely clustered TIE2 shows intracellular retention, we co-expressed TIE2-WT and Ang-1 ligand in HUVECs.…”

Section: Defective Glycosylation and Abnormal Intracellular Clusterinmentioning

confidence: 99%

Common and specific effects of TIE2 mutations causing venous malformations

et al. 2015

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Venous malformations (VMs) are localized defects in vascular morphogenesis frequently caused by mutations in the gene for the endothelial tyrosine kinase receptor TIE2. Here, we report the analysis of a comprehensive collection of 22 TIE2 mutations identified in patients with VM, either as single amino acid substitutions or as double-mutations on the same allele. Using endothelial cell (EC) cultures, mouse models and ultrastructural analysis of tissue biopsies from patients, we demonstrate common as well as mutation-specific cellular and molecular features, on the basis of which mutations cluster into categories that correlate with data from genetic studies. Comparisons of double-mutants with their constituent single-mutant forms identified the pathogenic contributions of individual changes, and their compound effects. We find that defective receptor trafficking and subcellular localization of different TIE2 mutant forms occur via a variety of mechanisms, resulting in attenuated response to ligand. We also demonstrate, for the first time, that TIE2 mutations cause chronic activation of the MAPK pathway resulting in loss of normal EC monolayer due to extracellular matrix (ECM) fibronectin deficiency and leading to upregulation of plasminogen/plasmin proteolytic pathway. Corresponding EC and ECM irregularities are observed in affected tissues from mouse models and patients. Importantly, an imbalance between plasminogen activators versus inhibitors would also account for high d-dimer levels, a major feature of unknown cause that distinguishes VMs from other vascular anomalies.

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“…Intriguing genetic and biochemical evidence suggests that tonic Tie-2 activation in the mature quiescent vasculature could be a ligand-independent phenomenon 53 , 54 . Nonetheless, Angpt-1 is poised to mediate this effect since it is made and secreted by platelets and by cells adjacent to the endothelium.…”

Section: Proof-of-concept Studies In Humansmentioning

confidence: 99%

Dysregulation of the angiopoietin–Tie-2 axis in sepsis and ARDS

Parikh

2013

Virulence

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Dynamic changes in microvascular endothelial structure and function are pivotal in the acute inflammatory response, the body’s rapid, coordinated effort to localize, sequester, and eliminate microbial invaders at their portal of entry. To achieve this, the endothelium becomes leaky and inflamed, providing innate immune cells and humoral effector molecules access to the site of infection. During sepsis this locally adaptive response becomes manifest throughout the body, leading to dangerous host consequences. Increased leakiness in the pulmonary circulation contributes to acute respiratory distress syndrome (ARDS), a complication of sepsis associated with 40% mortality. Understanding the molecular governance of vascular leak and inflammation has major diagnostic, prognostic, and potentially therapeutic implications for this common and pernicious disease. This review summarizes results from cell-based experiments, animal models, and observational human studies; together, these studies suggest that an endothelial receptor called Tie2 and its ligands, called angiopoietins, form a signaling axis key to the vascular dyshomeostasis that underlies sepsis.

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Ligand-independent Tie2 Dimers Mediate Kinase Activity Stimulated by High Dose Angiopoietin-1

Cited by 12 publications

References 37 publications

Dimerization of Tie2 mediated by its membrane-proximal FNIII domains

Dimerization of Tie2 mediated by its membrane-proximal FNIII domains

Common and specific effects of TIE2 mutations causing venous malformations

Dysregulation of the angiopoietin–Tie-2 axis in sepsis and ARDS

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