From Proteopedia

proteopedia linkproteopedia link

Revision as of 06:39, 13 May 2014 (edit) Student (Talk | contribs) ← Previous diff		Revision as of 07:35, 13 May 2014 (edit) (undo) Student (Talk | contribs) Next diff →
Line 13:		Line 13:
	oncostatin M <ref name="Wang2012">PMID: 22182585</ref>.		oncostatin M <ref name="Wang2012">PMID: 22182585</ref>.
-	<StructureSection>	+	<StructureSection load='1CNT_trunc.pdb' size='350' frame='true' side='right' caption='Dimeric structure of CNTF' scene='57/579704/Dimer_basic_view/3' />
		+
		+
	==Receptor for CNTF and the biological role of CNTF==		==Receptor for CNTF and the biological role of CNTF==

---

Revision as of 07:35, 13 May 2014

This Sandbox is Reserved from 01/04/2014, through 30/06/2014 for use in the course "510042. Protein structure, function and folding" taught by Prof Adrian Goldman, Tommi Kajander, Taru Meri, Konstantin Kogan and Juho Kellosalo at the University of Helsinki. This reservation includes Sandbox Reserved 923 through Sandbox Reserved 947.

To get started: Click the edit this page tab at the top. Save the page after each step, then edit it again. Click the 3D button (when editing, above the wikitext box) to insert Jmol. show the Scene authoring tools, create a molecular scene, and save it. Copy the green link into the page. Add a description of your scene. Use the buttons above the wikitext box for bold, italics, links, headlines, etc. More help: Help:Editing

Contents 1 Introduction 2 Receptor for CNTF and the biological role of CNTF 3 Structure 4 Disease and Clinical applications 5 Additional Resources 6 References

Introduction

Human Ciliary Neurotrophic Factor (CNTF) is a roughly 23 kDa protein consisting of a single polypeptide chain of 200 amino acid residues. It is a nerve growth factor belonging to the Interleukin-6 (IL-6) family of neuropoietic cytokines. Other members of this family include leukemia inhibitory factor (LIF), IL-6, IL-11 and oncostatin M ^[1].

spinqualitylabelsall models Dimeric structure of CNTF Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Receptor for CNTF and the biological role of CNTF

CNTF exerts its biological function by binding into a tripartite receptor complex consisting of a specific CNTF receptor subunit α (CNTFRα) linked to the cell membrane with a glycosyl-phosphatidylinositol linkage, and two signal-transducing transmembrane subunits LIF receptor beta (LIFRβ) and gp130. Binding of a hCNTF dimer to CNTFRα is the absolute first requirement to initiate a signal transduction cascade, which ultimately results in the enhanced transcription of genes encoding e.g. acute phase plasma proteins, and suppressors of cytokine signaling. CNTFRα has been observed to exist also as a soluble receptor (sCNTFRα) ^[2], attributed to a phospholipase C-mediated cleavage ^[3]. Additionally, hCNTF has been observed to be able to bind both to membrane-bound and soluble human Interleukin-6 receptor (IL-6R) and use as a substitute it to form the receptor complex necessary for signal transduction ^{[4] [5]}. These observations are considered to offer explanation as to why cells expressing LIFRβ and gp130 but not CNTFRα, are nonetheless responsive to CNTF.

CNTF's known biological functions involve affecting the growth, differentiation, survival and repair of various types of neurons and glial cells in both the central and peripheral nervous systems (^{[6] [5]}; evidence also suggests CNTF to be expressed in other tissues, such as adipocytes and hepatocytes among others (). As the transcription of CNTF mRNA and CNTF distribution have been noticed to be altered upon neural injury, it has been suggested, that CNTF is not an absolute requirement for neural development, but in fact mainly acts in response to neural injuries and stresses . Furthermore, mice homozygous for an inactived CNTF gene have been observed to develop normally, and to display losses in motor neurons only later during adulthood. Although humans homozygous for an inactivated CNTF gene caused by a mutation have not been observed to suffer from major neurological abnormalities ^[1], this has been linked with early onset of amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS) ^[5]. However, mice that have a CNTFRα knock-out die already during the perinatal stage and exhibit severe motor neuron deficits ^[6], suggesting that CNTFRα might have a second ligand.

Structure

Overview

spinqualitylabelsall models Dimeric structure of CNTF Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Like with many other cytokines, the tertiary structure of CNTF consists of four anti-parallel α-helices (A-D), where helices A-B and C-D are connected by two cross-over loops and helices B-C by one short loop. A partial crystal structure of a truncated form of hCNTF (2-187) is displayed here ^[7].

The CNTFRα-binding surface epitope of CNTF was identified to consist of residues Arg²⁵, Arg²⁸, Gln⁶³, Trp⁶⁴, Gln⁷⁴, Asp¹⁷⁵ and Arg¹⁷⁷. These residues are located in helix A, the loop between helices A-B, helix B and helix D ^[8]. In addition, the LIFR-binding epitope of CNTF was identified to consist of Glu³⁶-Met⁵⁶, Leu⁹¹-Ile¹⁰⁹ and Gly¹⁴⁷-Leu^{162 [9]}.

Gln⁶³ (ability of human CNTF to bind both CNTFRα and IL-6R).

"A structural analysis of CNTF suggested that amino acid residues situated in the C-terminal A-helix (Glu36-Gln42) and N-terminal AB loop (Gly43-Met56) form site IIIA, while the BC loop (His97-Asp104) with adjacent residues of the B- (Leu91- Val96) and C-helix (Phe105-Ile109) represents site IIIB. Together with site IIIC which closely corresponds to Bazan’s D1 motif (10) and consists of the C-terminal CD loop (Gly147-Leu151) and the N-terminal D-helix (Phe152-Leu162) they constitute the putative LIFR-binding epitope on CNTF (site III)."

(^[7]) Two water molecules are buried at the interface which form hydrogen bonds to the side chain of His84 and Tyrl21 (Figure IC). Nearly all interface side chains are conserved amongst CNTF sequences from different species (except Gln95).

Disease and Clinical applications

A frameshift mutation in exon 2 of the CNTF gene affecting some 2-3 % of the population (Takahashi 1994) causes earlier onset of the disease and quicker declination of motor neuron function in MS patients (Giess 2002). MS patients with functional CNTF show 1,7-fold increase of CNTF mRNA expression in the cortex, suggesting CNTF secretion as an innate response to progressing neuronal damage (Duetta 2007).

While not directly linked to disease, CNTF has been shown to inhibit the secretion of VEGF in the human retina, alleviating the symptoms of some ocular diseases ^[10]. It has been proposed that treatment with CNTF could counteract vision loss caused by age-related macular degeneration, retinitis pigmentosa and retinitis pigmentosa linked to Usher syndrome. In these cases the alleviating effect is produced by CNTF inducing regeneration of outer segments of cone cells in the retina ^[11]. Using encapsulated cells transfected with the human CNTF gene has been studied as a delivery method in clinical studies^[12], ^[13]. </StructureSection>

Additional Resources

[1]

References

1. ↑ ^{1.0 1.1} Wen R, Tao W, Li Y, Sieving PA. CNTF and retina. Prog Retin Eye Res. 2012 Mar;31(2):136-51. doi: 10.1016/j.preteyeres.2011.11.005., Epub 2011 Dec 10. PMID:22182585 doi:http://dx.doi.org/10.1016/j.preteyeres.2011.11.005
2. ↑ Panayotatos N, Everdeen D, Liten A, Somogyi R, Acheson A. Recombinant human CNTF receptor alpha: production, binding stoichiometry, and characterization of its activity as a diffusible factor. Biochemistry. 1994 May 17;33(19):5813-8. PMID:8180210
3. ↑ Davis S, Aldrich TH, Ip NY, Stahl N, Scherer S, Farruggella T, DiStefano PS, Curtis R, Panayotatos N, Gascan H, et al.. Released form of CNTF receptor alpha component as a soluble mediator of CNTF responses. Science. 1993 Mar 19;259(5102):1736-9. PMID:7681218
4. ↑ Schuster B, Kovaleva M, Sun Y, Regenhard P, Matthews V, Grotzinger J, Rose-John S, Kallen KJ. Signaling of human ciliary neurotrophic factor (CNTF) revisited. The interleukin-6 receptor can serve as an alpha-receptor for CTNF. J Biol Chem. 2003 Mar 14;278(11):9528-35. PMID:12643274
5. ↑ ^{5.0 5.1 5.2} Cognet I, Guilhot F, Chevalier S, Guay-Giroux A, Bert A, Elson GC, Gascan H, Gauchat JF. Expression of biologically active mouse ciliary neutrophic factor (CNTF) and soluble CNTFRalpha in Escherichia coli and characterization of their functional specificities. Eur Cytokine Netw. 2004 Jul-Sep;15(3):255-62. PMID:15542451
6. ↑ ^{6.0 6.1} Sleeman MW, Anderson KD, Lambert PD, Yancopoulos GD and Wiegand SJ. "The ciliary neurotrophic factor and its receptor, CNTFRα". Pharm Acta Helv 74: 265-272 (2000). http://dx.doi.org/10.1016/S0165-7208(00)80028-8
7. ↑ ^{7.0 7.1} McDonald NQ, Panayotatos N, Hendrickson WA. Crystal structure of dimeric human ciliary neurotrophic factor determined by MAD phasing. EMBO J. 1995 Jun 15;14(12):2689-99. PMID:7796798
8. ↑ Panayotatos N, Radziejewska E, Acheson A, Somogyi R, Thadani A, Hendrickson WA, McDonald NQ. Localization of functional receptor epitopes on the structure of ciliary neurotrophic factor indicates a conserved, function-related epitope topography among helical cytokines. J Biol Chem. 1995 Jun 9;270(23):14007-14. PMID:7539796
9. ↑ doi: https://dx.doi.org/10.1074/jbc.274.17.11859
10. ↑ Li R, Wen R, Banzon T, Maminishkis A, Miller SS. CNTF mediates neurotrophic factor secretion and fluid absorption in human retinal pigment epithelium. PLoS One. 2011;6(9):e23148. doi: 10.1371/journal.pone.0023148. Epub 2011 Sep 2. PMID:21912637 doi:http://dx.doi.org/10.1371/journal.pone.0023148
11. ↑ Li Y, Tao W, Luo L, Huang D, Kauper K, Stabila P, Lavail MM, Laties AM, Wen R. CNTF induces regeneration of cone outer segments in a rat model of retinal degeneration. PLoS One. 2010 Mar 2;5(3):e9495. doi: 10.1371/journal.pone.0009495. PMID:20209167 doi:http://dx.doi.org/10.1371/journal.pone.0009495
12. ↑ Sieving PA, Caruso RC, Tao W, Coleman HR, Thompson DJ, Fullmer KR, Bush RA. Ciliary neurotrophic factor (CNTF) for human retinal degeneration: phase I trial of CNTF delivered by encapsulated cell intraocular implants. Proc Natl Acad Sci U S A. 2006 Mar 7;103(10):3896-901. Epub 2006 Feb 27. PMID:16505355 doi:http://dx.doi.org/10.1073/pnas.0600236103
13. ↑ Talcott KE, Ratnam K, Sundquist SM, Lucero AS, Lujan BJ, Tao W, Porco TC, Roorda A, Duncan JL. Longitudinal study of cone photoreceptors during retinal degeneration and in response to ciliary neurotrophic factor treatment. Invest Ophthalmol Vis Sci. 2011 Apr 6;52(5):2219-26. doi: 10.1167/iovs.10-6479. PMID:21087953 doi:http://dx.doi.org/10.1167/iovs.10-6479

Richardson PM: Ciliary neurotrophic factor: A review. Pharmac Ther 63: 187-198 (1994).

Wen R, Song Y, Kjellstrom S, Tanikawa A, Liu Y, Li Y, Zhao L, Bush RA, Laties AM and Sieving PA: Regulation of rod phototransduction machinery by ciliary neurotrophic factor. J Neurosci 26: 13523-13530 (2006).