TIE-2, Soluble (TIE-2) Mouse Recombinant Protein

Function: Tyrosine-protein kinase that acts as cell-surface receptor for ANGPT1, ANGPT2 and ANGPT4 and regulates angiogenesis, endothelial cell survival, proliferation, migration, adhesion and cell spreading, reorganization of the actin cytoskeleton, but also maintenance of vascular quiescence. Has anti-inflammatory effects by preventing the leakage of proinflammatory plasma proteins and leukocytes from blood vessels. Required for normal angiogenesis and heart development during embryogenesis. Required for post-natal hematopoiesis. After birth, activates or inhibits angiogenesis, depending on the context. Inhibits angiogenesis and promotes vascular stability in quiescent vessels, where endothelial cells have tight contacts. In quiescent vessels, ANGPT1 oligomers recruit TEK to cell-cell contacts, forming complexes with TEK molecules from adjoining cells, and this leads to preferential activation of phosphatidylinositol 3-kinase and the AKT1 signaling cascades. In migrating endothelial cells that lack cell-cell adhesions, ANGT1 recruits TEK to contacts with the extracellular matrix, leading to the formation of focal adhesion complexes, activation of PTK2/FAK and of the downstream kinases MAPK1/ERK2 and MAPK3/ERK1, and ultimately to the stimulation of sprouting angiogenesis. ANGPT1 signaling triggers receptor dimerization and autophosphorylation at specific tyrosine residues that then serve as binding sites for scaffold proteins and effectors. Signaling is modulated by ANGPT2 that has lower affinity for TEK, can promote TEK autophosphorylation in the absence of ANGPT1, but inhibits ANGPT1-mediated signaling by competing for the same binding site. Signaling is also modulated by formation of heterodimers with TIE1, and by proteolytic processing that gives rise to a soluble TEK extracellular domain. The soluble extracellular domain modulates signaling by functioning as decoy receptor for angiopoietins. TEK phosphorylates DOK2, GRB7, GRB14, PIK3R1, SHC1 and TIE1. Ref.8 Ref.9 Ref.10 Ref.11 Ref.13 Ref.15 Ref.16 Ref.18

Catalytic activity: ATP + a [protein]-L-tyrosine = ADP + a [protein]-L-tyrosine phosphate. Ref.8

Enzyme regulation: Angiopoietin binding leads to receptor dimerization and activation by autophosphorylation at Tyr-990 on the kinase activation loop

By similarity.

Subunit structure: Homodimer. Heterodimer with TIE1. Interacts with ANGPT1, ANGPT2 and ANGPT4. At cell-cell contacts in quiescent cells, forms a signaling complex composed of ANGPT1 plus TEK molecules from two adjoining cells. In the absence of endothelial cell-cell contacts, interaction with ANGPT1 mediates contacts with the extracellular matrix. Interacts (tyrosine phosphorylated) with TNIP2. Interacts (tyrosine phosphorylated) with SHC1 (via SH2 domain)

By similarity. Interacts with PTPRB; this promotes endothelial cell-cell adhesion. Interacts with DOK2, GRB2, GRB7, GRB14, PIK3R1 and PTPN11/SHP2. Colocalizes with DOK2 at contacts with the extracellular matrix in migrating cells. Ref.10 Ref.11 Ref.14 Ref.15 Ref.16 Ref.17 Ref.18

Subcellular location: Cell membrane; Single-pass type I membrane protein. Cell junction

By similarity. Cell junction › focal adhesion

By similarity. Cytoplasm › cytoskeleton

By similarity. Secreted

By similarity. Note: Recruited to cell-cell contacts in quiescent endothelial cells. Colocalizes with the actin cytoskeleton and at actin stress fibers during cell spreading. Recruited to the lower surface of migrating cells, especially the rear end of the cell. Proteolytic processing gives rise to a soluble extracellular domain that is secreted

By similarity.

Tissue specificity: Specifically expressed in developing vascular endothelial cells. Abundantly expressed in lung and heart, moderately in brain, liver and kidney, and weakly in thymus, spleen and testis. Ref.6

Developmental stage: Expression detectable in day 8.5 embryos.

Domain: The soluble extracellular domain is functionally active in angiopoietin binding and can modulate the activity of the membrane-bound form by competing for angiopoietins

By similarity. Ref.14

Post-translational modification: Proteolytic processing leads to the shedding of the extracellular domain (soluble TIE-2 alias sTIE-2)

By similarity.Autophosphorylated on tyrosine residues in response to ligand binding. Autophosphorylation occurs in trans, i.e. one subunit of the dimeric receptor phosphorylates tyrosine residues on the other subunit. Autophosphorylation occurs in a sequential manner, where Tyr-990 in the kinase activation loop is phosphorylated first, followed by autophosphorylation at Tyr-1106 and at additional tyrosine residues. ANGPT1-induced phosphorylation is impaired during hypoxia, due to increased expression of ANGPT2

By similarity. Phosphorylation is important for interaction with GRB14, PIK3R1 and PTPN11. Phosphorylation at Tyr-1100 is important for interaction with GRB2 and GRB7. Phosphorylation at Tyr-1106 is important for interaction with DOK2 and for coupling to downstream signal transduction pathways in endothelial cells. Dephosphorylated by PTPRB. Ref.12 Ref.15 Ref.16Ubiquitinated. The phosphorylated receptor is ubiquitinated and internalized, leading to its degradation

By similarity. Ref.12 Ref.15 Ref.16

Disruption phenotype: Embryonically lethal. Embryos die at about 10 dpc, due to strongly decreased numbers of blood vessel endothelial cells, leading to severe hemorrhaging, and due to defects in heart trabeculae development. Mice display a general malformation of the vascular network with defective sprouting and dilated blood vessels. Ref.8 Ref.9

Sequence similarities: Belongs to the protein kinase superfamily. Tyr protein kinase family. Tie subfamily.Contains 3 EGF-like domains.Contains 3 fibronectin type-III domains.Contains 2 Ig-like C2-type (immunoglobulin-like) domains.Contains 1 protein kinase domain.