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Horváth VB, Soltész-Katona E, Wisniewski É, Rajki A, Halász E, Enyedi B, Hunyady L, Tóth AD, Szanda G. Optimization of the Heterologous Expression of the Cannabinoid Type-1 (CB 1) Receptor. Front Endocrinol (Lausanne) 2021; 12:740913. [PMID: 34745007 PMCID: PMC8564136 DOI: 10.3389/fendo.2021.740913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 09/21/2021] [Indexed: 11/13/2022] Open
Abstract
The G protein-coupled type 1 cannabinoid receptor (CB1R) mediates virtually all classic cannabinoid effects, and both its agonists and antagonists hold major therapeutic potential. Heterologous expression of receptors is vital for pharmacological research, however, overexpression of these proteins may fundamentally alter their localization pattern, change the signalling partner preference and may also spark artificial clustering. Additionally, recombinant CB1Rs are prone to intense proteasomal degradation, which may necessitate substantial modifications, such as N-terminal truncation or signal sequence insertion, for acceptable cell surface expression. We report here that tuning down the expression intensity of the full-length CB1R reduces proteasomal degradation and offers receptor levels that are comparable to those of endogenous CB1 receptors. As opposed to high-efficiency expression with conventional promoters, weak promoter-driven CB1R expression provides ERK 1/2 and p38 MAPK signalling that closely resemble the activity of endogenous CB1Rs. Moreover, weakly expressed CB1R variants exhibit plasma membrane localization, preserve canonical Gi-signalling but prevent CB1R-Gs coupling observed with high-expression variants. Based on these findings, we propose that lowering the expression level of G protein-coupled receptors should always be considered in heterologous expression systems in order to reduce the pressure on the proteasomal machinery and to avoid potential signalling artefacts.
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Affiliation(s)
| | - Eszter Soltész-Katona
- Department of Physiology, Semmelweis University, Budapest, Hungary
- MTA-SE Laboratory of Molecular Physiology, Eötvös Loránd Research Network, Budapest, Hungary
| | - Éva Wisniewski
- Department of Physiology, Semmelweis University, Budapest, Hungary
| | - Anikó Rajki
- Department of Physiology, Semmelweis University, Budapest, Hungary
- MTA-SE Laboratory of Molecular Physiology, Eötvös Loránd Research Network, Budapest, Hungary
| | - Eszter Halász
- Department of Physiology, Semmelweis University, Budapest, Hungary
- MTA-SE Laboratory of Molecular Physiology, Eötvös Loránd Research Network, Budapest, Hungary
| | - Balázs Enyedi
- Department of Physiology, Semmelweis University, Budapest, Hungary
- MTA-SE Lendület Tissue Damage Research Group, Hungarian Academy of Sciences and Semmelweis University, Budapest, Hungary
- HCEMM-SE Inflammatory Signaling Research Group, Department of Physiology, Semmelweis University, Budapest, Hungary
| | - László Hunyady
- Department of Physiology, Semmelweis University, Budapest, Hungary
- MTA-SE Laboratory of Molecular Physiology, Eötvös Loránd Research Network, Budapest, Hungary
| | - András Dávid Tóth
- MTA-SE Laboratory of Molecular Physiology, Eötvös Loránd Research Network, Budapest, Hungary
- Department of Internal Medicine and Haematology, Semmelweis University, Budapest, Hungary
| | - Gergő Szanda
- Department of Physiology, Semmelweis University, Budapest, Hungary
- MTA-SE Laboratory of Molecular Physiology, Eötvös Loránd Research Network, Budapest, Hungary
- *Correspondence: Gergő Szanda,
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Niewiarowska-Sendo A, Polit A, Piwowar M, Tworzydło M, Kozik A, Guevara-Lora I. Bradykinin B2 and dopamine D2 receptors form a functional dimer. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1864:1855-1866. [PMID: 28757212 DOI: 10.1016/j.bbamcr.2017.07.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 07/19/2017] [Accepted: 07/25/2017] [Indexed: 01/11/2023]
Abstract
In recent years a wide range of studies have shown that G protein-coupled receptors modulate a variety of cell functions through the formation of dimers. For instance, there is growing evidence for the dimerization of bradykinin or dopamine receptors, both as homodimers and heterodimers. A discovery of direct interactions of angiotensin II receptors with bradykinin 2 receptor (B2R) or dopamine D2 (D2R) receptor has led to a hypothesis on a potential dimerization between two latter receptors. In this study, we have demonstrated a constitutive colocalization of receptors on the membranes of HEK293 cells transiently transfected with plasmid vectors encoding B2R and D2R, fused with fluorescent proteins. The receptor colocalization was significantly enhanced by specific agonists of B2R or D2R after 5min following the addition, whereas simultaneous stimulation with these agonists did not influence the B2R/D2R colocalization level. In addition, B2R-D2R heterodimerization was confirmed with FLIM-FRET technique. The most characteristic signaling pathways for B2R and D2R, dependent on intracellular Ca2+ and cAMP concentration, respectively, were analyzed in cells presenting similar endogenous expression of B2R and D2R. Significant changes in receptors' signaling were observed after simultaneous stimulation with agonists, suggesting transformations in proteins' conformation after dimerization. The evidence of B2R-D2R dimerization may open new perspectives in the modulation of diverse cellular functions which depend on their activation.
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Affiliation(s)
- Anna Niewiarowska-Sendo
- Department of Analytical Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Krakow, Poland
| | - Agnieszka Polit
- Department of Physical Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Krakow, Poland
| | - Monika Piwowar
- Department of Bioinformatics and Telemedicine, Medical College, Jagiellonian University in Krakow, Poland
| | - Magdalena Tworzydło
- Department of Physical Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Krakow, Poland
| | - Andrzej Kozik
- Department of Analytical Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Krakow, Poland
| | - Ibeth Guevara-Lora
- Department of Analytical Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Krakow, Poland.
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Enquist J, Sandén C, Skröder C, Mathis SA, Leeb-Lundberg LMF. Kinin-Stimulated B1 Receptor Signaling Depends on Receptor Endocytosis Whereas B2 Receptor Signaling Does Not. Neurochem Res 2013; 39:1037-47. [DOI: 10.1007/s11064-013-1126-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Revised: 07/31/2013] [Accepted: 08/03/2013] [Indexed: 12/11/2022]
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Faussner A, Schüssler S, Feierler J, Bermudez M, Pfeifer J, Schnatbaum K, Tradler T, Jochum M, Wolber G, Gibson C. Binding characteristics of [3H]-JSM10292: a new cell membrane-permeant non-peptide bradykinin B2 receptor antagonist. Br J Pharmacol 2013; 167:839-53. [PMID: 22646218 DOI: 10.1111/j.1476-5381.2012.02054.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND AND PURPOSE A (3) H-labelled derivative of the novel small-molecule bradykinin (BK) B(2) receptor antagonist JSM10292 was used to directly study its binding properties to human and animal B(2) receptors in intact cells and to closely define its binding site. EXPERIMENTAL APPROACH Equilibrium binding, dissociation and competition studies with various B(2) receptor ligands and [(3) H]-JSM10292 were performed at 4°C and 37°C. The experiments were carried out using HEK293 cells stably (over)expressing wild-type and mutant B(2) receptors of human and animal origin. KEY RESULTS [(3) H]-JSM10292 bound to B(2) receptors at 4°C and at 37°C with the same high affinity. Its dissociation strongly depended on the temperature and increased when unlabelled B(2) receptor agonists or antagonists were added. [(3) H]-JSM10292 is cell membrane-permeant and thus also bound to intracellular, active B(2) receptors, as indicated by the different 'nonspecific' binding in the presence of unlabelled JSM10292 or of membrane-impermeant BK. Equilibrium binding curves with [(3) H]-JSM10292 and competition experiments with unlabelled JSM10292 and [(3) H]-BK showed a different affinity profile for the wild-type B(2) receptor in different species (man, cynomolgus, rabbit, mouse, rat, dog, pig, guinea pig). Characterization of B(2) receptor mutants and species orthologues combined with homology modelling, using the CXCR4 as template, suggests that the binding site of JSM10292 is different from that of BK but overlaps with that of MEN16132, another small non-peptide B(2) receptor ligand. CONCLUSIONS AND IMPLICATIONS [(3) H]-JSM10292 is a novel, cell membrane-permeant, high-affinity B(2) receptor antagonist that allows direct in detail studies of active, surface and intracellularly located wild-type and mutant B(2) receptors.
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Affiliation(s)
- A Faussner
- Institute for Cardiovascular Prevention, Ludwig-Maximilians-University, Pettenkoferstrasse 8a and 9, Munich, Germany.
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Uchida Y, Endoh T, Tazaki M, Sueishi K. Chronic bradykinin treatment alters 1α,25-dihydroxyvitamin D3-induced calcium current modulation in pre-osteoblasts. Cell Calcium 2012; 51:383-92. [DOI: 10.1016/j.ceca.2011.12.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Revised: 12/21/2011] [Accepted: 12/24/2011] [Indexed: 11/29/2022]
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Feierler J, Wirth M, Welte B, Schüssler S, Jochum M, Faussner A. Helix 8 plays a crucial role in bradykinin B(2) receptor trafficking and signaling. J Biol Chem 2011; 286:43282-93. [PMID: 22016392 DOI: 10.1074/jbc.m111.256909] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Upon activation the human bradykinin B(2) receptor (B(2)R) acts as guanine nucleotide exchange factor for the G proteins G(q/11) and G(i). Thereafter, it gets phosphorylated by G protein-coupled receptor kinases (GRKs) and recruits β-arrestins, which block further G protein activation and promote B(2)R internalization via clathrin-coated pits. As for most G protein-coupled receptors of family A, an intracellular helix 8 after transmembrane domain 7 is also predicted for the B(2)R. We show here that disruption of helix 8 in the B(2)R by either C-terminal truncation or just by mutation of a central amino acid (Lys-315) to a helix-breaking proline resulted in strong reduction of surface expression. Interestingly, this malfunction could be overcome by the addition of the membrane-permeable B(2)R antagonist JSM10292, suggesting that helix 8 has a general role for conformational stabilization that can be accounted for by an appropriate antagonist. Intriguingly, an intact helix 8, but not the C terminus with its phosphorylation sites, was indispensable for receptor sequestration and for interaction of the B(2)R with GRK2/3 and β-arrestin2 as shown by co-immunoprecipitation. Recruitment of β-arrestin1, however, required the presence of the C terminus. Taken together, our results demonstrate that helix 8 of the B(2)R plays a crucial role not only in efficient trafficking to the plasma membrane or the activation of G proteins but also for the interaction of the B(2)R with GRK2/3 and β-arrestins. Additional data obtained with chimera of B(2)R with other G protein-coupled receptors of family A suggest that helix 8 might have similar functions in other GPCRs as well.
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Affiliation(s)
- Jens Feierler
- Abteilung für Klinische Chemie und Klinische Biochemie, Ludwig-Maximilians-Universität, Nussbaumstrasse 20, D-80336 München, Germany
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Li S, Duan P, You G. Regulation of human organic anion transporter 3 by peptide hormone bradykinin. J Pharmacol Exp Ther 2010; 333:970-5. [PMID: 20299424 DOI: 10.1124/jpet.110.165472] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Human organic anion transporter (hOAT) 3 belongs to a family of organic anion transporters that play critical roles in the body disposition of numerous clinically important drugs. In the current study, we examined the regulation of hOAT3 by peptide hormone bradykinin (BK) in COS-7 cells. BK (<or=500 nM) induced a concentration- and time-dependent stimulation of hOAT3 activity, kinetically revealed as an increased V(max). Such an increase in V(max) resulted from an increased cell surface expression without a change in total cell expression of the transporter. BK-induced stimulation of hOAT3 activity could be prevented by treating hOAT3-expressing cells with staurosporine, a general inhibitor for protein kinase C (PKC). To obtain further information on which PKC isoform mediates BK regulation of hOAT3 activity, cellular distribution of various PKC isoforms was examined in cells treated with BK. We showed that BK treatment resulted in a significant translocation of PKCdelta, PKCepsilon, and PKCzeta from cytosol to membrane. We further showed that BK treatment enhanced association of hOAT3 with PKCdelta, PKCepsilon, and PKCzeta and that isoform-specific inhibitor for PKCdelta, PKCepsilon, and PKCzeta reversed BK effect on hOAT3 activity. We therefore concluded that BK stimulated hOAT3 activity through activation of PKCdelta, PKCepsilon, and PKCzeta, which then led to the redistribution of hOAT3 from the intracellular compartments to the cell surface and to the up-regulation of hOAT3 activity.
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Affiliation(s)
- Shanshan Li
- Department of Pharmaceutics, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA
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Faussner A, Wennerberg G, Schüssler S, Feierler J, Seidl C, Jochum M, Proud D. Alanine screening of the intracellular loops of the human bradykinin B receptor--effects on receptor maintenance, G protein activation and internalization. FEBS J 2009; 276:3491-503. [PMID: 19456859 DOI: 10.1111/j.1742-4658.2009.07071.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The bradykinin B(2) receptor is coupled to G protein G(q/11) and becomes sequestered into intracellular compartments after activation. To more closely define the receptor sequences involved in these processes and their functions, we systematically mutated all three intracellular loops (ICLs), either as point mutations or in groups of three to five amino acids to Ala, obtaining a total of 14 mutants. All constructs were stably expressed in HEK 293 cells and, with the exception of triple mutant DRY --> AAA, retained the ability to specifically bind [(3)H]bradykinin. The binding affinities at 4 or 37 degrees C of several mutants differed considerably from those determined for the wild-type receptor, indicating an allosteric connection between the conformation of the binding site and that of the ICLs. Mutations in ICL-1 strongly reduced surface expression without affecting G protein signaling or [(3)H]bradykinin internalization. Two cluster mutants in the middle of ICL-2 containing basic residues displayed considerably reduced potencies, whereas two mutations in ICL-3 resulted in receptor conformations that were considered to be semi-active, based on the observation that they responded with phosphoinositide hydrolysis to compounds normally considered to be antagonists. This, and the fact that a cluster mutant at the C-terminal end of ICL-3 was signaling incompetent, hint at the involvement of ICL-2 and ICL-3 in G(q/11) activation, albeit with different functions. None of the mutants displayed reduced ligand-induced receptor internalization, indicating that the loops are not essential for this process. No conclusion could be drawn, however, with regard to the role of the DRY sequence, as the corresponding triplet mutation lacked binding capability.
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Affiliation(s)
- Alexander Faussner
- Ludwig-Maximilians-Universität München, Abteilung für Klinische Chemie und Klinische Biochemie, Muenchen, Germany.
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Kramarenko II, Bunni MA, Morinelli TA, Raymond JR, Garnovskaya MN. Identification of functional bradykinin B(2) receptors endogenously expressed in HEK293 cells. Biochem Pharmacol 2008; 77:269-76. [PMID: 18938142 DOI: 10.1016/j.bcp.2008.09.027] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2008] [Revised: 09/19/2008] [Accepted: 09/22/2008] [Indexed: 11/29/2022]
Abstract
The human embryonic kidney (HEK) 293 cell line is widely used in cell biology research. Although HEK293 cells have been meticulously studied, our knowledge about endogenous G protein-coupled receptors (GPCR) in these cells is incomplete. While studying the effects of bradykinin (BK), a potent growth factor for renal cells, we unexpectedly discovered that BK activates extracellular signal-regulated protein kinase 1 and 2 (ERK) in HEK293 cells. Thus, we hypothesized that HEK293 cells possess endogenous BK receptors. RT-PCR demonstrated the presence of mRNAs for BK B(1) and BK B(2) receptors in HEK293 cells. Western blotting with BK B(1) and BK B(2) receptor antibodies confirmed this result at the protein level. To establish that BK receptors are functional, we employed fluorescent measurements of intracellular Ca(2+), measured changes in extracellular acidification rate (ECAR) as a reflection of the Na(+)/H(+) exchange (NHE) with a Cytosensortrade microphysiometer, and assessed ERK activation by Western blotting with a phospho-specific ERK antibody. Exposure of HEK293 cells to BK produced a concentration-dependent rise in intracellular Ca(2+) (EC(50)=36.5+/-8.0 x 10(-9)M), a rapid increase in tyrosine phosphorylation of ERK (EC(50)=9.8+/-0.4 x 10(-9)M), and elevation in ECAR by approximately 20%. All of these signals were blocked by HOE-140 (B(2) receptor antagonist) but not by des-Arg(10)-HOE-140 (B(1) receptor antagonist). We conclude that HEK293 cells express endogenous functional BK B(2) receptors, which couple to the mobilization of intracellular Ca(2+), increases in ECAR and increases in ERK phosphorylation.
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Affiliation(s)
- Inga I Kramarenko
- Medical and Research Services of the Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC 29401, USA
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10
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Kalatskaya I, Schüssler S, Seidl C, Jochum M, Faussner A. C-terminal fusion of eGFP to the bradykinin B2 receptor strongly affects down-regulation but not receptor internalization or signaling. Biol Chem 2006; 387:603-10. [PMID: 16740132 DOI: 10.1515/bc.2006.077] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
A functional comparison was made between the wild-type bradykinin B2 receptor (B2wt) and the chimera B2eGFP (enhanced green-fluorescent protein fused to the C-terminus of B2wt), both stably expressed in HEK 293 cells. There was almost no difference in terms of ligand-inducible receptor phosphorylation and internalization, signal transduction (accumulation of inositol phosphates) or expression and affinity. However, stimulation for up to 8 h with 10 microM bradykinin (BK) resulted in a strong decrease in surface receptors (by 60% within 5 h) in B2wt, but not in B2eGFP. When the expression levels of both constructs where comparably reduced using a weaker promoter, long-term stimulation resulted in a reduction in surface receptors for B2wt(low) to less than 20% within 1 h, whereas the chimera B2eGFP(low) still displayed 50% binding activity after 2 h. A 1-h incubation in the absence of BK resulted in a recovery of 60% of the binding in B2wt(low) after 1-h stimulation with BK, but of only 20% after 7-h stimulation. In contrast, B2eGFP(low) levels were restored to more than 70%, even after 7-h stimulation. These data indicate that although the fusion of eGFP to B2wt does not affect its ligand-induced internalization, it strongly reduces the down-regulation, most likely by promoting receptor recycling over degradation.
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Affiliation(s)
- Irina Kalatskaya
- Abteilung für Klinische Chemie und Klinische Biochemie, Ludwig-Maximilians-Universität München, Nussbaumstrasse 20, D-80336 München, Germany
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Faussner A, Bauer A, Kalatskaya I, Schüssler S, Seidl C, Proud D, Jochum M. The role of helix 8 and of the cytosolic C-termini in the internalization and signal transduction of B(1) and B(2) bradykinin receptors. FEBS J 2005; 272:129-40. [PMID: 15634338 DOI: 10.1111/j.1432-1033.2004.04390.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Determinants for desensitization and sequestration of G protein-coupled receptors often contain serine or threonine residues located in their C-termini. The sequence context, however, in which these residues have to appear, and the receptor specificity of these motifs are largely unknown. Mutagenesis studies with the B(2) bradykinin receptor (B(2)wt), stably expressed in HEK 293 cells, identified a sequence distal to N338 (NSMGTLRTSI, including I347 but not the basally phosphorylated S348) and in particular the TSI sequence therein, as a major determinant for rapid agonist-inducible internalization and the prevention of receptor hypersensitivity. Chimeras of the noninternalizing B(1) bradykinin receptor (B(1)wt) containing these B(2)wt sequences sequestered poorly, however, suggesting that additional motifs more proximal to N338 are required. In fact, further substitution of the B(1)wt C-terminus with corresponding B(2)wt regions either at C330(7.71) following putative helix 8 (B(1)CB(2)) or at the preceding Y312(7.53) in the NPXXY sequence (B(1)YB(2)) resulted in chimeras displaying rapid internalization. Intriguingly, however, exchange performed at K322(7.63) within putative helix 8 generated a slowly internalizing chimera (B(1)KB(2)). Detailed mutagenesis analysis generating additional chimeras identified the change of V323 in B(1)wt to serine (as in B(2)wt) as being responsible for this effect. The slowly internalizing chimera as well as a B(1)wt point-mutant V323S displayed significantly reduced inositol phosphate accumulation as compared to B(1)wt or the other chimeras. The slow internalization of B(1)KB(2) was also accompanied by a lack of agonist-induced phosphorylation, that in contrast was observed for B(1)YB(2) and B(1)CB(2), suggesting that putative helix 8 is either directly or indirectly (e.g. via G protein activation) involved in the interaction between the receptor and receptor kinases.
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Affiliation(s)
- Alexander Faussner
- Ludwig-Maximilians-Universität, Abteilung für Klinische Chemie und Klinische Biochemie, München, Germany.
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Faussner A, Schuessler S, Seidl C, Jochum M. Inhibition of sequestration of human B2 bradykinin receptor by phenylarsine oxide or sucrose allows determination of a receptor affinity shift and ligand dissociation in intact cells. Biol Chem 2004; 385:835-43. [PMID: 15493879 DOI: 10.1515/bc.2004.109] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Depending on their interaction with intracellular proteins, G protein-coupled receptors (GPCR) often display different affinities for agonists at 37 degrees C. Determining the affinity at that temperature is often difficult in intact cells as most GPCRs are internalized after activation. When sequestration of the B2 bradykinin receptor (B2R) was inhibited by either 0.5 M sucrose or phenylarsine oxide (PAO), a shift in the affinity was detected when the incubation temperature was raised from 4 degrees C to 37 degrees C or lowered from 37 degrees C to 4 degrees C. In contrast, binding of the antagonist [3H]NPC 17731 was temperature-independent. B2R mutants displayed different affinity shifts allowing conclusions on the role of the involved amino acids. By inhibiting receptor sequestration it was possible to determine also dissociation of [3H]BK and of [3H]NPC 17731 from intact cells at 37 degrees C. Surprisingly, both dissociation rates were markedly enhanced by the addition of unlabeled ligand, most likely via prevention of reassociation of dissociated [3H]ligand. This suggests that dissociated [3H]ligand cannot move freely away from the receptor. In summary, our data demonstrate that inhibition of receptor internalization either by PAO or sucrose provides an excellent method to study receptor function and the effects of mutations in intact cells.
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Affiliation(s)
- Alexander Faussner
- Ludwig-Maximilians-Universität München, Abteilung für Klinische Chemie und Klinische Biochemie, Nussbaumstrasse 20, D-80336 München, Germany.
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Skidgel RA, Alhenc-Gelas F, Campbell WB. Prologue: kinins and related systems. New life for old discoveries. Am J Physiol Heart Circ Physiol 2003; 284:H1886-91. [PMID: 12742820 DOI: 10.1152/ajpheart.00164.2003] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Randal A Skidgel
- Department of Pharmaocolgy, University of Illinois College of Medicine, Chicago 60612, USA
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