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==Kinase Domain of Tyrosine-protein kinase receptor TIE-2 (PDB:6MWE)==
==Kinase Domain of Tyrosine-protein kinase receptor TIE-2 (PDB:6MWE)==
<StructureSection load='6MWE' size='340' side='right' caption='Caption for this structure' scene='' name='pp'>
<StructureSection load='6MWE' size='340' side='right' caption='Caption for this structure' scene='' name='pp'>
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The protein we are focusing one is a protein kinase receptor to a family of ligands called angiopoietins. This receptor is a Tyrosine Kinase TIE2. We are going to analyze the kinase domain of this protein
 
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The protein we are focusing one is a protein kinase receptor to a family of ligands called angiopoietins. This receptor is a Tyrosine Kinase TIE2.
It acts as cell-surface receptor for the ligands ANGPT1, ANGPT2 and ANGPT4 and regulates among others angiogenesis, endothelial cell survival and maintenance of vascular quiescence. It is important in the regulation of both normal physiologic and pathologic angiogenesis. The later is a fundamental step in the transition of tumors from a benign state to a malignant one.
It acts as cell-surface receptor for the ligands ANGPT1, ANGPT2 and ANGPT4 and regulates among others angiogenesis, endothelial cell survival and maintenance of vascular quiescence. It is important in the regulation of both normal physiologic and pathologic angiogenesis. The later is a fundamental step in the transition of tumors from a benign state to a malignant one.
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Angiogenesis is the process in which new blood vessels are formed from pre-existing blood vessels. The growth of these new blood vessels requires migration and proliferation of endothelial cells (ECs). It is an event controlled by angiogenic growth factors such as vascular endothelial growth factor (VEGF).
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While ANGPT1 is a TIE2 agonist and has a higher binding affinity to it than ANGPT2, ANGPT2 can act as a context-dependent agonist. Thus, the ANGPT/TIE2 kinase signaling pathway is an attractive anti-vascular target.
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Angiogenesis is the process in which new blood vessels are formed from pre-existing blood vessels. The growth of these new blood vessels requires migration and proliferation of endothelial cells (ECs). It is an event controlled by angiogenic growth factors such as vascular endothelial growth factor (VEGF).
 
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While ANGPT1 is a TIE2 agonist and has a higher binding affinity to it than ANGPT2, ANGPT2 can act as a context-dependent agonist. Thus, the ANGPT/TIE2 kinase signaling pathway is an attractive anti-vascular target.
 
Be careful with the &lt; and &gt; signs.
Be careful with the &lt; and &gt; signs.
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== Function ==
== Function ==
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In vascular development, cellular processes are controlled by molecular signal transduction pathways. Those are under the influence of growth factor receptors : the tyrosine kinases present on the surface of endothelial cells. When ligands bind to these receptors, in this case ANGPT1 or ANGPT2, there is oligomerization provoking the activation of the kinase and autophosphorylation.
 
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===• Ligands and their binding===
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== Structural highlights ==
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TIE2 maintains the vascular integrity of mature vessels by enhancing endothelial barrier function and inhibiting apoptosis of endothelial cells.
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ANGPT1 is a TIE2 agonist : in vitro, it binds to TIE2 and induces its activation via tyrosine phosphorylation. In vivo, it was proven that inactivation of ANGPT1 or over expression of ANGPT2 produce similar effects.
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This is a sample scene created with SAT to <scene name="/12/3456/Sample/1">color</scene> by Group, and another to make <scene name="/12/3456/Sample/2">a transparent representation</scene> of the protein. You can make your own scenes on SAT starting from scratch or loading and editing one of these sample scenes.
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ANGPT2 is a competitive antagonist of TIE2 or a partial agonist of TIE2 depending on the context. In stressed ECs, one recent report suggests that ANGPT2 may activate TIE2 signaling in the absence of ANGPT1 and in high concentrations.
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===• Signal transduction and kinase activity===
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===•Catalytic activation===
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Receptor tyrosine kinases are transmembrane proteins with a ligand-binding extracellular domain, a single membrane-spanning domain, a juxtamembrane region, a catalytic domain, and a C-terminal tail. In cell culture, ANGPT1 induces phosphorylation of TIE2 and stimulates endothelial cell migration and survival.
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ATP + L-tyrosyl-[protein] = ADP + H+ + O-phospho-L-tyrosyl-[protein]
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Angiopoietin binding leads to receptor dimerization and activation by autophosphorylation at Tyr-992 on the kinase activation loop.
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The activation of the receptor is due to a ligand-induced dimerization : the extracellular receptor domain dimerization brings the cytosolic kinase domains next to each other for intermolecular autophosphorylation. The latter occurs when one subunit of the dimeric receptor phosphorylates tyrosine residues on the other subunit. It happens in a sequential manner : Tyr-992 in the kinase activation loop is phosphorylated first, followed by autophosphorylation at Tyr-1108 and at additional tyrosine residues. Autophosphorylation also has multiple functions including recruitment of downstream signaling molecules.
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[[Image:Réaction Phosphorylation.jpg]]
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Looking more closely at the TIE2 intracellular domain, 1106 is found at the base of a loop formed between the C-terminus tail and the C-terminus lobe of the kinase. The OH group of Tyr-1106 is thus directly into the solvent and accessible to phosphorylation. However, Tyr-1100 is not solvent exposed : thereby implying that the carboxy-terminal tail must undergo a conformational change upon activation of the receptor to expose this tyrosine residue for phosphorylation.
 
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Consequent to ANGPT1 stimulation, the SH2 domain-containing p85 subunit of phosphatidylinositol (PI) 3-kinase is recruited to TIE via tyrosine residue 1100 in the C-end tail of the receptor, leading to activation of the enzyme.
 
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Interestingly, inhibition of PI 3′ kinase activity can only partially inhibit the chemotactic effect of ANGPT1 on endothelial cells, thereby implying that additional TIE2 binding partners may also contribute to ANGPT1-mediated endothelial cell migration. Phosphorylation of TIE2 further results in its association with a docking protein related to downstream of kinase (Dok), known as Dok-R, it allows Dok-R to serve as a substrate of TIE2 and thereby become tyrosine phosphorylated.
 
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== Structural highlights ==
 
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This is a sample scene created with SAT to <scene name="/12/3456/Sample/1">color</scene> by Group, and another to make <scene name="/12/3456/Sample/2">a transparent representation</scene> of the protein. You can make your own scenes on SAT starting from scratch or loading and editing one of these sample scenes.
 
== Disease ==
== Disease ==
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Arginine at position 849 is found in six residues upstream of the invariant lysine K855 in the kinase domain (sequence preserved among the human, bovine, murine and rat TIE2 sequences). This seems to prove that a basic amino acid is essential for this position. In addition, arginine located a few amino acids before invariant lysine is involved in stabilizing the kinase domain (hydrogen binding of arginine with a proline downstream). It is therefore possible that R849 may also be involved in the stabilization of the kinase domain. Thus, the substitution of R849 by a W could modify the conformation of the kinase domain, leading to a decrease in inhibitory mechanisms and involving autophosphorylation.
Arginine at position 849 is found in six residues upstream of the invariant lysine K855 in the kinase domain (sequence preserved among the human, bovine, murine and rat TIE2 sequences). This seems to prove that a basic amino acid is essential for this position. In addition, arginine located a few amino acids before invariant lysine is involved in stabilizing the kinase domain (hydrogen binding of arginine with a proline downstream). It is therefore possible that R849 may also be involved in the stabilization of the kinase domain. Thus, the substitution of R849 by a W could modify the conformation of the kinase domain, leading to a decrease in inhibitory mechanisms and involving autophosphorylation.
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'''''Diagram : Comparison of the Kinase Activities of Normal and Mutant TIE2 Receptors'''''
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With this mutation, Venous Malformations (VMs) contain a Disproportionately high ratio of Endothelial Cells (ECs) to Smooth Muscle Cells (SMCs)
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(B) Cells infected with wild-type baculovirus (wt) or virus expressing normal TIE2 (R2) or mutant TIE2 (W2). Cells expressing the mutation at position 849 (Arginine → Tryptophan) have an autophosphorylation activity 6 to 10 times higher than wild cells.
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[[Image:Venous Malformations Diagram.jpg]]
[[Image:Venous Malformations Diagram.jpg]]
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''Fig 1 : Comparison of the Kinase Activities of Normal and Mutant TIE2 Receptors''
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''(B) Cells infected with wild-type baculovirus (wt) or virus expressing normal TIE2 (R2) or mutant TIE2 (W2). Cells expressing the mutation at position 849 (Arginine → Tryptophan) have an autophosphorylation activity 6 to 10 times higher than wild cells.''
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[[Image:Venous Malformations Immunohistochemistry.jpg]]
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''Fig 2 : Immunohistochemistry of VMs with Antibodies against Smooth Muscle Cells 𝛂-Actin''
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With this mutation, Venous Malformations (VMs) contain a Disproportionately high ratio of Endothelial Cells (ECs) to Smooth Muscle Cells (SMCs)
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''B = Abnormal channels''
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'''''Pictures of immunohistochemistry of VMs with Antibodies against Smooth Muscle Cells 𝛂-Actin'''''
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''C = Normal veins (v) and arteries (a)''
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B = Abnormal channels
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''Scale bars, 200 𝛍m''
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C = Normal veins (v) and arteries (a)
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''Antibodies directed against SMCs 𝛂-Actin from cells with VMs show that the vessels have a specific and abnormal staining (B) compared to normal vessels (C)''
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Scale bars, 200 𝛍m.
 
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Antibodies directed against SMCs 𝛂-Actin from cells with VMs show that the vessels have a specific and abnormal staining (B) compared to normal vessels (C)
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– '''Mutation in position 897''' : Tyrosine → Cystéine. Change from large size and aromatic (Y) to medium size and polar (C). An error of vascular morphogenesis characterized by dilated, serpiginous channels
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– '''Mutation in position 897''' : Tyrosine → Sérine. Change from large size and aromatic (Y) to small size and polar (S). An error of vascular morphogenesis characterized by dilated, serpiginous channels.
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– '''Mutation in position 915''' : Arginine → Histidine. Change from large size and basic (R) to medium size and polar (H). An error of vascular morphogenesis characterized by dilated, serpiginous channels.
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– '''Mutation in position 918''' : Arginine → Cystéine. Change from large size and basic (R) to medium size and polar (C). An error of vascular morphogenesis characterized by dilated, serpiginous channels.
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– '''Mutation in position 919''' : Valine → Leucine. Similar physico-chemical property. Both residues are medium size and hydrophobic. An error of vascular morphogenesis characterized by dilated, serpiginous channels.
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– '''Mutation in position 925''' : Alanine → Sérine. Change from small size and hydrophobic (A) to small size and polar (S). Increased ligand-independent autophosphorylation and kinase activation.
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– '''Mutation in position 1100''' : Lysine → Asparagine. Change from large size and basic (K) to medium size and polar (N). Increased ligand-independent autophosphorylation and kinase activation.
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===•Mutagénèse===
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– '''Transfer in position 855''' : Loss of kinase activity
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– '''Transfer in position 1102''' : Deletes interaction with CHS1
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[[Image:Venous Malformations Immunohistochemistry.jpg]]
 
== Relevance ==
== Relevance ==

Revision as of 15:51, 10 January 2019

This Sandbox is Reserved from 06/12/2018, through 30/06/2019 for use in the course "Structural Biology" taught by Bruno Kieffer at the University of Strasbourg, ESBS. This reservation includes Sandbox Reserved 1480 through Sandbox Reserved 1543.
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Kinase Domain of Tyrosine-protein kinase receptor TIE-2 (PDB:6MWE)

Caption for this structure

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References

  1. Hanson, R. M., Prilusky, J., Renjian, Z., Nakane, T. and Sussman, J. L. (2013), JSmol and the Next-Generation Web-Based Representation of 3D Molecular Structure as Applied to Proteopedia. Isr. J. Chem., 53:207-216. doi:http://dx.doi.org/10.1002/ijch.201300024
  2. Herraez A. Biomolecules in the computer: Jmol to the rescue. Biochem Mol Biol Educ. 2006 Jul;34(4):255-61. doi: 10.1002/bmb.2006.494034042644. PMID:21638687 doi:10.1002/bmb.2006.494034042644
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