Sandbox reserved 1169

From Proteopedia

(Difference between revisions)
Jump to: navigation, search
Current revision (07:06, 19 April 2016) (edit) (undo)
 
(4 intermediate revisions not shown.)
Line 14: Line 14:
Like other G protein-coupled receptors, the neurotensin receptor is composed of 3 distinct regions. An <scene name='72/727765/Overall_structure/5'>extracellular binding site</scene> where neurotensin binds and causes a conformational change of the protein. A region containing <scene name='72/727765/Overall_structure/4'>7 transmembrane alpha helices</scene> (PDB code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4GRV 4GRV)] that transduce the signal from the extracellular side of the cell membrane to the intracellular side. Lastly, an intracellular region, that when activated by a conformational change in the protein, activates a [https://en.wikipedia.org/wiki/G_protein G-protein] associated with this receptor. Currently no crystal structures of the inactive form of the neurotensin receptor are available. Without a representation of the inactive form, the conformational changes caused by agonist binding are still not completely known.
Like other G protein-coupled receptors, the neurotensin receptor is composed of 3 distinct regions. An <scene name='72/727765/Overall_structure/5'>extracellular binding site</scene> where neurotensin binds and causes a conformational change of the protein. A region containing <scene name='72/727765/Overall_structure/4'>7 transmembrane alpha helices</scene> (PDB code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4GRV 4GRV)] that transduce the signal from the extracellular side of the cell membrane to the intracellular side. Lastly, an intracellular region, that when activated by a conformational change in the protein, activates a [https://en.wikipedia.org/wiki/G_protein G-protein] associated with this receptor. Currently no crystal structures of the inactive form of the neurotensin receptor are available. Without a representation of the inactive form, the conformational changes caused by agonist binding are still not completely known.
=== Neurotensin Binding Site ===
=== Neurotensin Binding Site ===
-
Binding of NTS to the binding site on NTSR1 is enriched by <scene name='72/721539/Binding_pocket_surface/4'>charge complementarity</scene> (PDB code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4GRV 4GRV)]between the positive NTS arginine side chains and the [https://en.wikipedia.org/wiki/Electronegativity electronegative] pocket. The protein is colored by charge: <font color='#FF0000'>negative</font> and <font color='#0000CD'>positive</font>. Two of NTS's arginine residues are colored <font color='#0000CD'>blue</font>. In addition, the C-terminus of <font color='#32CD32'>NTS</font> forms a <scene name='72/721539/Binding_site_charges/4'>salt bridge</scene> (PDB code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4GRV 4GRV)] with Arg328 of <font color='#A9A9A9'>NTSR1</font>. Three [https://en.wikipedia.org/wiki/Hydrogen_bond hydrogen bonds] are made between the side chains of NTS and the receptor while most of the interactions are a result of [https://en.wikipedia.org/wiki/Van_der_Waals_force Van der Waals] interactions. The binding pocket is partially capped by a <scene name='72/721539/B-hairpin_loop/1'>Β-hairpin loop</scene> at the proximal end of the receptor's N-terminus.<ref name="White"/> The interactions in the binding site cause a wide spread conformational change in the receptor leading to the receptor to adopt an active conformation. This active conformation allows for the activating of the associated intracellular G-protein.
+
Binding of NTS to the binding site on NTSR1 is enriched by <scene name='72/721539/Binding_pocket_surface/4'>charge complementarity</scene> (PDB code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4GRV 4GRV)]between the positive NTS arginine side chains and the [https://en.wikipedia.org/wiki/Electronegativity electronegative] pocket. The protein is colored by charge: <font color='#FF0000'>negative</font> and <font color='#0000CD'>positive</font>. Two of NTS's arginine residues are colored <font color='#0000CD'>blue</font>. In addition, the C-terminus of <font color='#32CD32'>NTS</font> forms a <scene name='72/721539/Binding_site_charges/4'>salt bridge</scene> (PDB code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4GRV 4GRV)] with Arg328 of <font color='#A9A9A9'>NTSR1</font>. Three [https://en.wikipedia.org/wiki/Hydrogen_bond hydrogen bonds] are made between the side chains of NTS and the receptor while most of the interactions are a result of [https://en.wikipedia.org/wiki/Van_der_Waals_force Van der Waals] interactions. The binding pocket is partially capped by a <scene name='72/721539/B-hairpin_loop/1'>Β-hairpin loop</scene> at the proximal end of the receptor's N-terminus.<ref name="White"/> The interactions in the binding site cause a wide spread conformational change in the receptor leading to the receptor to adopt an active conformation. This active conformation allows for the activation of the associated intracellular G-protein.
=== Hydrophobic Stacking ===
=== Hydrophobic Stacking ===
-
A major player in the transduction of the extracellular signal to the intracellular G protein is the <scene name='72/727765/Hydrogen_bonding_network/4'>hydrogen bonding network</scene> (PDB code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4GRV 4GRV)]that links the bound <font color='#32CD32'>hormone</font> with the [https://en.wikipedia.org/wiki/Hydrophobe hydrophobic] core of the <font color='#A9A9A9'>neurotensin receptor</font>. The carboxylate of Leu13 of NTS forms a hydrogen bond network with R327, R328, and Y324. The Tyr324, in turn, is brought into an orientation to make the formation of a <scene name='72/727765/Hydrophobic_stacking_4xee/2'>hydrophobic stacking</scene> (PDB Code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4XEE 4XEE]) network between F358, W321, A157, and F317 possible.<ref name="Krumm">PMID:23051748</ref> The effects that this network has on the activation of the intracellular G-protein was examined by the [https://en.wikipedia.org/wiki/Mutagenesis mutagenesis] of amino acids involved in this network. Mutagenesis of <scene name='72/727765/Overall_structure/12'>A86L</scene>, <scene name='72/727765/Overall_structure/13'>E166A</scene>, <scene name='72/727765/Overall_structure/14'>G125L</scene>, <scene name='72/727765/Overall_structure/15'>L310A</scene>, <scene name='72/727765/Overall_structure/16'>F358A</scene>, and <scene name='72/727765/Overall_structure/17'>V360A</scene> (PDB code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4GRV 4GRV)] showed that when this interaction was disrupted, the receptor no longer was able to activate the G-protein. <ref name="Krumm"/> This discovery lead to the conclusion that the conformational changes caused by this stacking allows for the signal to be moved from the extracellular binding site through the transmembrane helices of the receptor to the intracellular region activating the G-protein.
+
A major player in the transduction of the extracellular signal to the intracellular G-protein is the <scene name='72/727765/Hydrogen_bonding_network/4'>hydrogen bonding network</scene> (PDB code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4GRV 4GRV)]that links the bound <font color='#32CD32'>hormone</font> with the [https://en.wikipedia.org/wiki/Hydrophobe hydrophobic] core of the <font color='#A9A9A9'>neurotensin receptor</font>. The carboxylate of Leu13 of NTS forms a hydrogen bond network with R327, R328, and Y324. The Tyr324, in turn, is brought into an orientation to make the formation of a <scene name='72/727765/Hydrophobic_stacking_4xee/2'>hydrophobic stacking</scene> (PDB Code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4XEE 4XEE]) network between F358, W321, A157, and F317 possible.<ref name="Krumm">PMID:23051748</ref> The effects that this network has on the activation of the intracellular G-protein was examined by the [https://en.wikipedia.org/wiki/Mutagenesis mutagenesis] of amino acids that disrupted the formation of this network. Mutagenesis of <scene name='72/727765/Overall_structure/12'>A86L</scene>, <scene name='72/727765/Overall_structure/13'>E166A</scene>, <scene name='72/727765/Overall_structure/14'>G125L</scene>, <scene name='72/727765/Overall_structure/15'>L310A</scene>, <scene name='72/727765/Overall_structure/16'>F358A</scene>, and <scene name='72/727765/Overall_structure/17'>V360A</scene> (PDB code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4GRV 4GRV)] showed that when this interaction was disrupted, the receptor no longer was able to activate the G-protein. <ref name="Krumm"/> This discovery lead to the conclusion that the conformational changes caused by this stacking allows for the signal to be moved from the extracellular binding site through the transmembrane helices of the receptor to the intracellular region activating the G-protein.
== Sodium Binding Pocket ==
== Sodium Binding Pocket ==
[[Image:4XEE closed sodium pocket.png|100 px|left|thumb|Figure 2: Closed form of sodium binding pocket that caps the entrance of sodium into the top of the binding pocket. (PDB Code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4XEE 4XEE])]]
[[Image:4XEE closed sodium pocket.png|100 px|left|thumb|Figure 2: Closed form of sodium binding pocket that caps the entrance of sodium into the top of the binding pocket. (PDB Code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4XEE 4XEE])]]
-
[[Image:4GRV open binding pocket.png|100 px|left|thumb|Figure 3: Open form of sodium binding pocket that does not cap the entrance of sodium into the top of the binding pocket. (PDB code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4GRV 4GRV])]] Conserved across all class A GPCRs, a <scene name='72/727765/Sodium_binding_pocket_final/1'>sodium binding pocket</scene> PDB code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4GRV 4GRV] is seen in the middle of TM2 helix. The sodium ion is coordinated with a highly conserved Asp113 and four other oxygen contacts from a combination of water molecules. For G-protein activation to be possible, a hydrogen bond coordination with T156, S362, and N365 of the NPxxY [https://en.wikipedia.org/wiki/Structural_motif motif] must occur. Trp321 helps to maintain the active conformation of the receptor by occluding the top of the binding pocket using [https://en.wikipedia.org/wiki/Van_der_Waals_force Van der Waals] interactions (Figure 2). The form of the binding pocket where Trp321 does not occlude the top of the pocket can be seen when mutations to A86L, G215A, and V360A are present (Figure 3). This form of the receptor would allow more sodium into the binding pocket. The binding of sodium within this site disrupts the coordination of the hydrogen bonds and places the receptor in its uncollapsed, inactive form. <ref name="Katritch">PMID:24767681</ref>
+
[[Image:4GRV open binding pocket.png|100 px|left|thumb|Figure 3: Open form of sodium binding pocket that does not cap the entrance of sodium into the top of the binding pocket. (PDB code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4GRV 4GRV])]] Conserved across all class A GPCRs, a <scene name='72/727765/Sodium_binding_pocket_final/1'>sodium binding pocket</scene> (PDB code:[http://www.rcsb.org/pdb/explore/explore.do?structureId=4GRV 4GRV]) is seen in the middle of TM2 helix. The sodium ion is coordinated with a highly conserved Asp113 and four other oxygen contacts from a combination of water molecules. For G-protein activation to be possible, a hydrogen bond coordination with T156, S362, and N365 of the NPxxY [https://en.wikipedia.org/wiki/Structural_motif motif] must occur. Trp321 helps to maintain the active conformation of the receptor by occluding the top of the binding pocket using [https://en.wikipedia.org/wiki/Van_der_Waals_force Van der Waals] interactions (Figure 2). This occlusion stops sodium ions from entering the top of the binding pocket and helps NTSR1 remain in its active conformation. The conformation of the binding pocket where Trp321 does not occlude the top can be seen when mutations to A86L, G215A, and V360A are present (Figure 3). This form of the receptor would allow more sodium into the binding pocket and therefor stabilize the inactive receptor form. <ref name="Katritch">PMID:24767681</ref>
=== Allosteric Effects ===
=== Allosteric Effects ===
-
Sodium ions are a negative [https://en.wikipedia.org/wiki/Allosteric_regulation allosteric] inhibitor to the binding of the neurotensin [https://en.wikipedia.org/wiki/Agonist agonist] to the binding site on the neurotensin receptor. Sodium's binding causes for the receptor to favor its inactive state. Asp113 of the highly conserved D/RY motif and Asn365 of the highly conserved NPxxY motif form a substantial hydrogen bonding network with T156 and S362.<ref name="Krumm"/> This hydrogen bonding network prevents the incorporation of the sodium ion by collapsing upon itself and filling the sodium binding pocket. Trp321 also works to inhibit the incorporation of the sodium ion by capping off the sodium binding pocket to not allow sodium to enter from the top. Trp321 uses Van der Waals interactions to place it in the conformation necessary to block sodium from entering the site. By not allowing for sodium to enter this binding site, the receptor is able to conform to its active state and activate the G-protein that is associated with it.
+
Sodium ions are a negative [https://en.wikipedia.org/wiki/Allosteric_regulation allosteric] inhibitor to the binding of the neurotensin [https://en.wikipedia.org/wiki/Agonist agonist] to the binding site on the neurotensin receptor. Sodium's binding causes for the receptor to favor its inactive state by disrupting the hydrogen bond network between nearby amino acids. This disruption in the hydrogen bond network causes the pocket to be in its uncollapsed form. Asp113 of the highly conserved D/RY motif and Asn365 of the highly conserved NPxxY motif form a substantial hydrogen bonding network with T156 and S362.<ref name="Krumm"/> This hydrogen bonding network prevents the incorporation of the sodium ion by collapsing upon itself and filling the sodium binding pocket. Trp321 also works to inhibit the incorporation of the sodium ion by capping off the sodium binding pocket to not allow sodium to enter from the top. Trp321 uses Van der Waals interactions to place it in the conformation necessary to block sodium from entering the site. By not allowing for sodium to enter this binding site, the receptor is able to conform to its active state and activate the G-protein that is associated with it.
==Clinical Relevance==
==Clinical Relevance==
NTSR1 is commonly expressed in various invasive [https://en.wikipedia.org/wiki/Cancer cancer] cell lines making it a promising cancer drug target. It is prevalent in [https://en.wikipedia.org/wiki/Colorectal_cancer colon cancer] [https://en.wikipedia.org/wiki/Adenocarcinoma adenocarcinoma], but is not found in adult colon cell types.<ref name="Valerie">PMID:21903767</ref> NTSR1 is also found in aggressive [https://en.wikipedia.org/wiki/Prostate_cancer prostate cancer] cells, but not [https://en.wikipedia.org/wiki/Epithelium epithelial] prostate cells. In prostate cancer cells, binding of NTS results in [https://en.wikipedia.org/wiki/Mitogen-activated_protein_kinase mitogen-activated protein kinase (PKB)], [https://en.wikipedia.org/wiki/Phosphoinositide_3-kinase phosphoinositide-3 kinase (PI-3K)], [https://en.wikipedia.org/wiki/Epidermal_growth_factor_receptor epidermal growth factor receptor (EGFR)], [https://en.wikipedia.org/wiki/Proto-oncogene_tyrosine-protein_kinase_Src SRC], and [https://en.wikipedia.org/wiki/STAT5 STAT5] phosphorylation.<ref name="Valerie"/> These all result in increased DNA synthesis, [https://en.wikipedia.org/wiki/Cell_growth cell proliferation], and survival. Inhibition of NTSR1 and its downstream signaling represents a target for [https://en.wikipedia.org/wiki/Radiation_therapy radiotherapy], which uses radiation to target malignant cells. [[Image: Meclinerant.jpg |100 px|left|thumb|Figure 4: Meclinerant: An inhibitor of NTSR1 found to enhance selectivity of radiotherapy in cancer treatment (PubMed).]]NTSR1 can be inhibited by agonist [https://en.wikipedia.org/wiki/Meclinertant meclinertant] which inhibits proliferation and prosurvival of cancer cells. Combination treatment of radiation and meclinerant provides selective treatment of cancer cells over normal cells, indicating the need for clinical trials of this approach. <ref name="Kisfalvi">PMID:19679549</ref>
NTSR1 is commonly expressed in various invasive [https://en.wikipedia.org/wiki/Cancer cancer] cell lines making it a promising cancer drug target. It is prevalent in [https://en.wikipedia.org/wiki/Colorectal_cancer colon cancer] [https://en.wikipedia.org/wiki/Adenocarcinoma adenocarcinoma], but is not found in adult colon cell types.<ref name="Valerie">PMID:21903767</ref> NTSR1 is also found in aggressive [https://en.wikipedia.org/wiki/Prostate_cancer prostate cancer] cells, but not [https://en.wikipedia.org/wiki/Epithelium epithelial] prostate cells. In prostate cancer cells, binding of NTS results in [https://en.wikipedia.org/wiki/Mitogen-activated_protein_kinase mitogen-activated protein kinase (PKB)], [https://en.wikipedia.org/wiki/Phosphoinositide_3-kinase phosphoinositide-3 kinase (PI-3K)], [https://en.wikipedia.org/wiki/Epidermal_growth_factor_receptor epidermal growth factor receptor (EGFR)], [https://en.wikipedia.org/wiki/Proto-oncogene_tyrosine-protein_kinase_Src SRC], and [https://en.wikipedia.org/wiki/STAT5 STAT5] phosphorylation.<ref name="Valerie"/> These all result in increased DNA synthesis, [https://en.wikipedia.org/wiki/Cell_growth cell proliferation], and survival. Inhibition of NTSR1 and its downstream signaling represents a target for [https://en.wikipedia.org/wiki/Radiation_therapy radiotherapy], which uses radiation to target malignant cells. [[Image: Meclinerant.jpg |100 px|left|thumb|Figure 4: Meclinerant: An inhibitor of NTSR1 found to enhance selectivity of radiotherapy in cancer treatment (PubMed).]]NTSR1 can be inhibited by agonist [https://en.wikipedia.org/wiki/Meclinertant meclinertant] which inhibits proliferation and prosurvival of cancer cells. Combination treatment of radiation and meclinerant provides selective treatment of cancer cells over normal cells, indicating the need for clinical trials of this approach. <ref name="Kisfalvi">PMID:19679549</ref>

Current revision

Neurotensin Receptor (NTSR1)

Neurotensin G-Protein Coupled Receptor (PDB Codes 4GRV and 4XEE)

Drag the structure with the mouse to rotate

References

  1. ↑ Millar RP, Newton CL. The year in G protein-coupled receptor research. Mol Endocrinol. 2010 Jan;24(1):261-74. Epub 2009 Dec 17. PMID:20019124 doi:10.1210/me.2009-0473
  2. ↑ Gui X, Carraway RE. Enhancement of jejunal absorption of conjugated bile acid by neurotensin in rats. Gastroenterology. 2001 Jan;120(1):151-60. PMID:11208724
  3. ↑ Selivonenko VG. [The interrelationship between electrolytes and phase analysis of systole in toxic goiter]. Probl Endokrinol (Mosk). 1975 Jan-Feb;21(1):19-23. PMID:1173461
  4. ↑ Fang Y, Lahiri J, Picard L. G protein-coupled receptor microarrays for drug discovery. Drug Discov Today. 2004 Dec 15;9(24 Suppl):S61-7. PMID:23573662
  5. ↑ 5.0 5.1 White JF, Noinaj N, Shibata Y, Love J, Kloss B, Xu F, Gvozdenovic-Jeremic J, Shah P, Shiloach J, Tate CG, Grisshammer R. Structure of the agonist-bound neurotensin receptor. Nature. 2012 Oct 25;490(7421):508-13. doi: 10.1038/nature11558. Epub 2012 Oct 10. PMID:23051748 doi:http://dx.doi.org/10.1038/nature11558
  6. ↑ Carraway R, Leeman SE. The isolation of a new hypotensive peptide, neurotensin, from bovine hypothalami. J Biol Chem. 1973 Oct 10;248(19):6854-61. PMID:4745447
  7. ↑ Kitabgi P. Neurotensin modulates dopamine neurotransmission at several levels along brain dopaminergic pathways. Neurochem Int. 1989;14(2):111-9. PMID:20504406
  8. ↑ Mustain WC, Rychahou PG, Evers BM. The role of neurotensin in physiologic and pathologic processes. Curr Opin Endocrinol Diabetes Obes. 2011 Feb;18(1):75-82. doi:, 10.1097/MED.0b013e3283419052. PMID:21124211 doi:http://dx.doi.org/10.1097/MED.0b013e3283419052
  9. ↑ Vincent JP, Mazella J, Kitabgi P. Neurotensin and neurotensin receptors. Trends Pharmacol Sci. 1999 Jul;20(7):302-9. PMID:10390649
  10. ↑ 10.0 10.1 10.2 White JF, Noinaj N, Shibata Y, Love J, Kloss B, Xu F, Gvozdenovic-Jeremic J, Shah P, Shiloach J, Tate CG, Grisshammer R. Structure of the agonist-bound neurotensin receptor. Nature. 2012 Oct 25;490(7421):508-13. doi: 10.1038/nature11558. Epub 2012 Oct 10. PMID:23051748 doi:http://dx.doi.org/10.1038/nature11558
  11. ↑ Katritch V, Fenalti G, Abola EE, Roth BL, Cherezov V, Stevens RC. Allosteric sodium in class A GPCR signaling. Trends Biochem Sci. 2014 May;39(5):233-44. doi: 10.1016/j.tibs.2014.03.002. Epub , 2014 Apr 21. PMID:24767681 doi:http://dx.doi.org/10.1016/j.tibs.2014.03.002
  12. ↑ 12.0 12.1 Valerie NC, Casarez EV, Dasilva JO, Dunlap-Brown ME, Parsons SJ, Amorino GP, Dziegielewski J. Inhibition of neurotensin receptor 1 selectively sensitizes prostate cancer to ionizing radiation. Cancer Res. 2011 Nov 1;71(21):6817-26. doi: 10.1158/0008-5472.CAN-11-1646. Epub, 2011 Sep 8. PMID:21903767 doi:http://dx.doi.org/10.1158/0008-5472.CAN-11-1646
  13. ↑ Kisfalvi K, Eibl G, Sinnett-Smith J, Rozengurt E. Metformin disrupts crosstalk between G protein-coupled receptor and insulin receptor signaling systems and inhibits pancreatic cancer growth. Cancer Res. 2009 Aug 15;69(16):6539-45. doi: 10.1158/0008-5472.CAN-09-0418. PMID:19679549 doi:http://dx.doi.org/10.1158/0008-5472.CAN-09-0418
Retrieved from "http://52.214.119.220/wiki/index.php/Sandbox_reserved_1169"
Personal tools