Advanced

The G-protein coupled receptor CMKLR1/ChemR23: Studies on gene regulation, receptor ligand activation, and HIV/SIV co-receptor function

Mårtensson, Ulrika LU (2005)
Abstract (Swedish)
Popular Abstract in Swedish

För att en organism ska fungera är det nödvändigt att alla de celler som bygger upp organismen kommunicerar med varandra. Denna kommunikation sker genom att speciella proteiner på cellens yta, s.k. receptorer, tar emot signaler från andra celler.



G-proteinkopplade receptorer (GPCR) är den vanligaste typen av receptorer. Då en signalmolekyl binder till en GPCR ändrar den form vilket medför att den kan binda ett G-protein på insidan av cellmembranet. G-proteinet förmedlar signalen vidare till



effektorproteiner inne i cellen och ett cellsvar uppkommer. GPCRs medverkar i de flesta fysiologiska funktioner som t.ex. immunförsvar eller uppfattning av ljus och lukt.... (More)
Popular Abstract in Swedish

För att en organism ska fungera är det nödvändigt att alla de celler som bygger upp organismen kommunicerar med varandra. Denna kommunikation sker genom att speciella proteiner på cellens yta, s.k. receptorer, tar emot signaler från andra celler.



G-proteinkopplade receptorer (GPCR) är den vanligaste typen av receptorer. Då en signalmolekyl binder till en GPCR ändrar den form vilket medför att den kan binda ett G-protein på insidan av cellmembranet. G-proteinet förmedlar signalen vidare till



effektorproteiner inne i cellen och ett cellsvar uppkommer. GPCRs medverkar i de flesta fysiologiska funktioner som t.ex. immunförsvar eller uppfattning av ljus och lukt. GPCRs är involverade i många sjukdomar t.ex. HIV/AIDS där viruset använder sig av G-proteinkopplade receptorer för att ta sig in i kroppens immunförsvarsceller. Av de närmare 800 GPCRs som finns i vår kropp är dock cirka 160 fortfarande okända, dvs man vet ej deras funktion i kroppen eller signalmolekylerna som aktiverar dem.



Vi har fokuserat på en GPCR som kallas CMKLR1/ChemR23. Receptorn är strukturellt lik andra receptorer involverade i immunförsvaret. CMKLR1/ChemR23 uttrycks bl.a. i ben, brosk och i immunförsvarsceller men dess fysiologiska roll i kroppen är nästan helt okänd. I sjukdomssammanhang har CMKLR1/ChemR23 visat sig ha betydelse vid HIV-infektion där viruset binder till receptorn för att sedan ta sig in i kroppens immunförsvarsceller. Signalmolekylen som aktiverar CMKLR1/ChemR23 har under större delen av mitt avhandlingsarbete varit okänd men nyligen identifierades molekylen, "TIG2" eller "chemerin", i inflammatoriska vätskor och i blodfiltrat. TIG2/chemerin är liksom dess receptor aktiv i inflammatoriska processer och verkar också ha en funktion i benbildning.



I syfte att öka kunskapen om denna länge okända receptor har vi studerat CMKLR1/ChemR23 i mus och människa. Med hjälp av molekylärbiologiska metoder har vi kartlagt hur receptorgenen i mus ser ut i jämförelse med människa. Receptorgenen i mus kan se ut på två olika sätt och systemet som reglerar receptorns bildning kan också se ut på två olika sätt beroende på i vilken cell receptorn bildas.



I en studie av hur signalmolekylen TIG2/chemerin interagerar med CMKLR1/ChemR23 kan vi visa att mus TIG2/chemerin aktiverar musreceptorn i lägre grad än i människa.



Vi kan visa att HIV-1, HIV-2 och SIV (motsvarigheten till HIV i apa) binder CMKLR1/ChemR23 för att sedan infektera människans immunförsvarsceller. Av ett antal olika testade HIV-1 stammar är det endast två stammar som använder CMKLR1/ChemR23 för infektion. Flera HIV-1 isolat som använder den etablerade receptorn CCR3 kan utnyttja CMKLR1/ChemR23. HIV-2 och SIV använder CMKLR1/ChemR23 mer generellt. Vi har kunnat konstatera att vid infektion binder de olika virustyperna olika extracellulära receptorregioner. (Less)
Abstract
In all higher organisms, there is a need for intercellular communication. G-protein coupled receptors (GPCRs), located on the cell surface, play an important role in this communication. Cells synthesize and release signalling molecules (ligands), which produce a specific response only in those cells that have a receptor for that ligand. The total number of GPCRs is estimated to be around 800 where approximately 160 still are "orphans", meaning that the endogenous ligands are unknown.



CMKLR1/ChemR23 is a GPCR that was recently "de-orphanized" when the endogenous ligand, TIG2/chemerin, was isolated from inflammatory fluids and hemofiltrate. The receptor displays a high homology to chemoattractant-like receptors involved in... (More)
In all higher organisms, there is a need for intercellular communication. G-protein coupled receptors (GPCRs), located on the cell surface, play an important role in this communication. Cells synthesize and release signalling molecules (ligands), which produce a specific response only in those cells that have a receptor for that ligand. The total number of GPCRs is estimated to be around 800 where approximately 160 still are "orphans", meaning that the endogenous ligands are unknown.



CMKLR1/ChemR23 is a GPCR that was recently "de-orphanized" when the endogenous ligand, TIG2/chemerin, was isolated from inflammatory fluids and hemofiltrate. The receptor displays a high homology to chemoattractant-like receptors involved in inflammation processes. Sequence is implicated in osseous and cartilage development, and the receptor is also suggested to have a pathophysiological role as one of the co-receptors involved in human and simian immunodeficiency virus (HIV-1 and SIV)-infection of CD4+ immune cells. We have described the genomic organization of cmklr1 in mouse and analysed the regulatory mechanism behind the corresponding receptor expression. Two transcripts of mouse cmklr1 have been identified, cmklr1a and b, which utilize alternative promoters for transcription. We show that four Sp1 transcription factors are involved in cmklr1a promoter activation in mouse NB4 1A3 cells, whereas the transcription factor NFY is important for transcription of cmklr1b in mouse BV2 cells. Cmklr1a shows expression in organs such as heart and lung whereas cmklr1b is suggested to be an inducible transcript up-regulated by stimulation with all-trans retinoic acid (ATRA).



The interaction between CMKLR1/ChemR23 and TIG2/chemerin in mouse has been studied. Mouse TIG2/chemerin was found to activate the mouse receptor, although to a lower degree than for the human receptor. Peptides corresponding to the C-terminus of mouse TIG2/chemerin could activate mouse CMKLR1/ChemR23 but to a lower extent than the human receptor. The



results indicate that the peptide domains necessary for receptor activation differ for human and mouse TIG2/chemerin or that the maximal response of the mouse receptor is lower than in human.



The importance of human CMKLR1/ChemR23 as a co-receptor for HIV and SIV has been investigated. We show that CMKLR1/ChemR23 can function as a minor co-receptor for select HIV-1 isolates as well as more generally for HIV-2 and SIV isolates. Among certain better-characterized co-receptors, the HIV-1 co-receptor function of



CMKLR1/ChemR23 resembles that of the chemokine receptor, CCR3. Using a "humanized" hybrid rat CMKLR1/ChemR23 receptor as model, it was shown that the major determinants for HIV-1 and HIV-2 interaction with the receptor reside to a varying degree in the N-terminus and second extracellular loop, whereas the viral interaction in the case of SIV primarily involves the second extracellular loop. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Melhus, Håkan, Department of Medical Sciences, Uppsala University, Sweden
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Medicin (människa och djur), Medicine (human and vertebrates), HIV/SIV, TIG2/chemerin, transcriptional regulation, ligand activation, Co-receptor, GPCR, ChemR23/CMKLR1
pages
162 pages
publisher
Elsevier
defense location
BioMedical Center (BMC), Segerfalksalen, Sölvegatan 17, Lund
defense date
2005-04-02 09:15
ISSN
1652-8220
ISBN
91-85439-24-x
language
English
LU publication?
yes
id
1ebec080-ce40-401e-88e9-1f32f9accce4 (old id 544455)
date added to LUP
2007-10-13 12:41:52
date last changed
2016-09-23 15:15:25
@phdthesis{1ebec080-ce40-401e-88e9-1f32f9accce4,
  abstract     = {In all higher organisms, there is a need for intercellular communication. G-protein coupled receptors (GPCRs), located on the cell surface, play an important role in this communication. Cells synthesize and release signalling molecules (ligands), which produce a specific response only in those cells that have a receptor for that ligand. The total number of GPCRs is estimated to be around 800 where approximately 160 still are "orphans", meaning that the endogenous ligands are unknown.<br/><br>
<br/><br>
CMKLR1/ChemR23 is a GPCR that was recently "de-orphanized" when the endogenous ligand, TIG2/chemerin, was isolated from inflammatory fluids and hemofiltrate. The receptor displays a high homology to chemoattractant-like receptors involved in inflammation processes. Sequence is implicated in osseous and cartilage development, and the receptor is also suggested to have a pathophysiological role as one of the co-receptors involved in human and simian immunodeficiency virus (HIV-1 and SIV)-infection of CD4+ immune cells. We have described the genomic organization of cmklr1 in mouse and analysed the regulatory mechanism behind the corresponding receptor expression. Two transcripts of mouse cmklr1 have been identified, cmklr1a and b, which utilize alternative promoters for transcription. We show that four Sp1 transcription factors are involved in cmklr1a promoter activation in mouse NB4 1A3 cells, whereas the transcription factor NFY is important for transcription of cmklr1b in mouse BV2 cells. Cmklr1a shows expression in organs such as heart and lung whereas cmklr1b is suggested to be an inducible transcript up-regulated by stimulation with all-trans retinoic acid (ATRA).<br/><br>
<br/><br>
The interaction between CMKLR1/ChemR23 and TIG2/chemerin in mouse has been studied. Mouse TIG2/chemerin was found to activate the mouse receptor, although to a lower degree than for the human receptor. Peptides corresponding to the C-terminus of mouse TIG2/chemerin could activate mouse CMKLR1/ChemR23 but to a lower extent than the human receptor. The<br/><br>
<br/><br>
results indicate that the peptide domains necessary for receptor activation differ for human and mouse TIG2/chemerin or that the maximal response of the mouse receptor is lower than in human.<br/><br>
<br/><br>
The importance of human CMKLR1/ChemR23 as a co-receptor for HIV and SIV has been investigated. We show that CMKLR1/ChemR23 can function as a minor co-receptor for select HIV-1 isolates as well as more generally for HIV-2 and SIV isolates. Among certain better-characterized co-receptors, the HIV-1 co-receptor function of<br/><br>
<br/><br>
CMKLR1/ChemR23 resembles that of the chemokine receptor, CCR3. Using a "humanized" hybrid rat CMKLR1/ChemR23 receptor as model, it was shown that the major determinants for HIV-1 and HIV-2 interaction with the receptor reside to a varying degree in the N-terminus and second extracellular loop, whereas the viral interaction in the case of SIV primarily involves the second extracellular loop.},
  author       = {Mårtensson, Ulrika},
  isbn         = {91-85439-24-x},
  issn         = {1652-8220},
  keyword      = {Medicin (människa och djur),Medicine (human and vertebrates),HIV/SIV,TIG2/chemerin,transcriptional regulation,ligand activation,Co-receptor,GPCR,ChemR23/CMKLR1},
  language     = {eng},
  pages        = {162},
  publisher    = {Elsevier},
  school       = {Lund University},
  title        = {The G-protein coupled receptor CMKLR1/ChemR23: Studies on gene regulation, receptor ligand activation, and HIV/SIV co-receptor function},
  year         = {2005},
}