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Originally published In Press as doi:10.1074/jbc.M402572200 on March 19, 2004

J. Biol. Chem., Vol. 279, Issue 21, 22102-22107, May 21, 2004
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Spontaneous Formation of a Proteolytic B1 and B2 Bradykinin Receptor Complex with Enhanced Signaling Capacity*

Dong Soo Kang{ddagger}§, Kristina Ryberg{ddagger}, Matthias Mörgelin¶, and L. M. Fredrik Leeb-Lundberg{ddagger}§||

From the {ddagger}Division of Molecular Neurobiology, Department of Physiological Sciences and Division of Molecular Pathogenesis, Department of Cell and Molecular Biology, Lund University, Lund SE-22184, Sweden and §Department of Biochemistry, The University of Texas Health Science Center, San Antonio, Texas 78229-3900

Received for publication, March 8, 2004


    ABSTRACT
 TOP
 ABSTRACT
 INTRODUCTION
 EXPERIMENTAL PROCEDURES
 RESULTS
 DISCUSSION
 REFERENCES
 
B1 bradykinin receptor (B1R) induction is critical in the adaptation of the kinin-mediated inflammatory response from a B2 bradykinin receptor (B2R) subtype to a B1R subtype that occurs during chronic insult. Here, we show that B1R spontaneously forms a proteolytic plasma membrane complex with B2R along with increased receptor signaling capacity. Co-expression of hemagglutinin-tagged B2R with FLAG-tagged B1R in HEK293 cells resulted in degradation of B2R as determined by the diminution of the intact 65-kDa B2R species and the appearance of proteolytic B2R products at 30–40 kDa and by the reduction in B2R bradykinin binding sites. On the other hand, the 35-kDa B1R remained intact. Receptor co-expression also led to an increase in constitutive and agonist-stimulated receptor signaling. Selective immunoprecipitation with epitope-specific antibodies revealed a spontaneously formed heterologous receptor complex, which was composed of the intact 35-kDa B1R and the B2R degradation products. Cellular fractionation, cell surface biotinylation, and immunoelectron microscopy showed that B2R·B1R complexes were present on the cell surface. This is the first evidence that a heterologous G protein-coupled receptor complex in the plasma membrane is linked to proteolytic degradation of a participating receptor, and this mechanism may contribute to the adaptation of the kinin response from a B2 type to a B1 type during chronic insult.


    INTRODUCTION
 TOP
 ABSTRACT
 INTRODUCTION
 EXPERIMENTAL PROCEDURES
 RESULTS
 DISCUSSION
 REFERENCES
 
Kinins are potent agonists who participate in the inflammatory and pain responses to insults by acting through two receptor subtypes named B1 and B2 (1). During sustained insult, the kinin-mediated response adapts from a B2 type in the acute phase to a B1 type in the chronic phase (2). This adaptation is explained in part by an induction of B1R1 from essentially a null level, which is triggered by pro-inflammatory cytokines (3) and important in the chronic response (4, 5). B1R induction may be necessary to prolong the kinin response because it has been observed that the cellular B2 response desensitizes rapidly, whereas the B1 response is sustained (6). Indeed, B1R is constitutively active, i.e. active in the absence of agonist (7).

It is now well established that G protein-coupled receptors are capable of hetero-oligomerizing in the cell (8), but in only a few cases has a direct causal relationship been established between a hetero-oligomer and a functional outcome. The best described hetero-oligomeric G protein-coupled receptor system is the GABAB receptor, in which the type 1 receptor is responsible for recognizing GABA, the type 2 receptor for agonist-dependent receptor G protein coupling, and expression of both receptors is required for proper trafficking to the plasma membrane (911). Other heterologous G protein-coupled receptor combinations have revealed receptor trans-activation and changes in pharmacological profiles, agonist efficacy, and receptor internalization.

B1R and B2R subtypes are co-expressed on many cell structures on which B1R induction may be readily observed including primary sensory neurons, which are critical for the pain response (1216). Furthermore, cellular cross-talk between B1R and B2R occurs via bradykinin (BK) stimulation of B2R, which leads to an autocrine up-regulation of B1R through an interleukin-1{beta}-mediated mechanism (16). Also, in some cells that co-express the receptors, such as PC3 prostate cancer cells, the pharmacological profile of kinin signaling through each receptor subtype suggests the co-engagement of the other subtype in the response (15).

On this basis, we hypothesized that in cells that co-express B1R and B2R, these receptors directly interact to enhance signaling. In this report we investigated the effect of heterologous co-expression of B1R and B2R. Our results show that B1R promotes the formation of a plasma membrane complex with B2R, which involves proteolytic degradation of B2R along with increased constitutive and agonist-stimulated kinin receptor signaling. This event may be part of a cellular adaptation of kinin signaling in the inflammatory and pain response from a B2 type to a B1 type that occurs during sustained insult.


    EXPERIMENTAL PROCEDURES
 TOP
 ABSTRACT
 INTRODUCTION
 EXPERIMENTAL PROCEDURES
 RESULTS
 DISCUSSION
 REFERENCES
 
Cell Culture, Mutation, and Transfection—HEK293 cells were grown, and mutations and transfections were done as described previously (7). The FLAG and HA epitopes were inserted at the receptor N terminus immediately following the initial methionine.

Plasma Membrane Fractionation—Enrichment of plasma membranes followed the procedure by Smart et al. (17), with a few modifications as described previously by us (18).

Functional Receptor Assays—Receptor activities were assayed by monitoring PI hydrolysis in cells transfected with a series of receptor cDNA amounts and labeled with 1 µCi/ml myo-[3H]inositol as described previously (7). B1R and B2R densities were determined using saturating concentrations (2–3 nM) of [3H]DK and [3H]BK (PerkinElmer Life Sciences), respectively. The slope factors of the increases in basal cellular PI hydrolysis and agonist-stimulated PI hydrolysis as a function of the level of receptor expression were used as parameters of constitutive and agonist-dependent receptor activity.

Cell Surface Biotinylation—Cells were biotinylated with 4 ml of 0.3 mg/ml non-permeable polyethylene oxide-maleimide activated biotin (Pierce) for 30 min at 4 °C, washed two times with ice-cold phosphatebuffered saline, and quenched with 1 mM dithiothreitol/phosphate-buffered saline for 10 min at 4 °C. After washing three times with ice-cold phosphate-buffered saline, cells were immunoprecipitated and electroblotted as described below. Biotinylated receptors were detected with streptavidin conjugated to horseradish peroxidase (Vector Laboratories).

Immunoprecipitation and Immunoblotting—Cells were subjected to immunoprecipitation and/or immunoblotting essentially as described previously (7). For immunoprecipitation, the lysate was incubated with anti-FLAG M2 antibody (1:300; Stratagene), anti-HA antibody (1:300; Covance), or polyclonal antibodies raised against the B1R and B2R C-terminal tail residues 317–353 (anti-B1R-(317–353)) and 310–364 (anti-B2R-(310–364)), respectively (18), followed by incubation with protein A-Sepharose beads with or without precoupled rabbit antimouse IgG. For immunoblotting, samples were subjected to SDS-PAGE under reducing conditions (6% {beta}-mercaptoethanol) on 12% gels, electroblotted onto nitrocellulose membranes, and then stained with anti-FLAG M2 antibody (1:1000) or anti-HA antibody (1:1000). Immunoreactive bands were visualized with a chemiluminescence immunodetection kit using peroxidase-labeled sheep anti-mouse antibody according to the procedure described by the supplier (PerkinElmer Life Sciences).

Immunoelectron Microscopy—The FLAG and HA antibodies were labeled with colloidal gold of different sizes (5 and 11 nm, respectively), as described previously (19). Cells co-expressing FLAG-tagged B1R (FB1) and HA-tagged B2 receptor (HB2) were incubated with the gold-labeled antibodies for 30 min at 4 °C. The cells were fixed for 1 h at room temperature and then fixed overnight at 4 °C in 2.5% glutaraldehyde in 0.15 M sodium cacodylate, pH 7.4 (cacodylate buffer). The fixed samples were washed with cacodylate buffer and postfixed for 1 h at room temperature in 1% osmium tetroxide in cacodylate buffer. The samples were then dehydrated in a graded series of ethanol and embedded in Epon 812 using acetone as intermediate solvent. Specimens were sectioned with a diamond knife into 50-nm-thick, ultrathin sections on an LKB ultramicrotome. The sections were then stained with uranyl acetate and lead citrate. Specimens were observed in a Jeol JEM 1230 electron microscope operated at 80 kV accelerating voltage. Images were recorded with a Gatan Multiscan 791 charge-coupled device camera.

Data Analysis—Where indicated, data are presented as the mean ± S.E. and were compared using Student's t test.


    RESULTS
 TOP
 ABSTRACT
 INTRODUCTION
 EXPERIMENTAL PROCEDURES
 RESULTS
 DISCUSSION
 REFERENCES
 
Identification of Human B1R and B2R and Their Relative Level of Glycosylation—To study the consequence of B1R and B2R co-expression, the respective receptors were structurally modified with the FLAG and HA epitopes at their N termini and then expressed in HEK293 cells. The 35-kDa FB1 (Fig. 1A, lane 2) and 65-kDa hemagglutinin-tagged B2R (HB2) (Fig. 1B, lane 2) were then monitored with epitope-specific antibodies and antibodies against human B1R C-terminal residues 317–353 (anti-B1R-(317–353)) and human B2R C-terminal tail residues 310–364 (anti-B2R-(310–364)). The different relative molecular mass of intact B2R and B1R was due to differential N-linked glycosylation. As shown in Fig. 1B, lanes 3 and 4, treatment of anti-B2R-(310–364) immunoprecipitates with 2 units of PNGase F for 2 h at 37 °C promoted a decrease in the relative mass of HB2 from 65 kDa to ~40 kDa. On the other hand, treatment of anti-FLAG immunoprecipitates did not change the relative mass of FB1 (Fig. 1A, lanes 3 and 4).



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FIG. 1.
Identification of B1R and B2R and their level of N-glycosylation. A, cells transfected with pcDNA3 vector (-; lane 1) and FB1 (lanes 2–4) were immunoprecipitated (IP) with anti-B1R-(317–353) antibody (lanes 1 and 2) and anti-FLAG antibody (lanes 3 and 4) and immunoblotted (IB) with anti-FLAG antibody. The anti-FLAG immunoprecipitates were treated without (lane 3) and with (lane 4) PNGase F for 2 h at 37 °C before immunoblotting. B, cells transfected with pcDNA3 vector (-; lane 1) and HB2 (lanes 2–4) were immunoprecipitated (IP) with anti-B2R-(310–364) antibody and immunoblotted (IB) with anti-HA antibody. The immunoprecipitates were treated without (lane 3) and with (lane 4) 2 units of PNGase F for 2 h at 37 °C before immunoblotting.

 
B1R-promoted Proteolytic Processing of B2R—Co-expression of HB2 and WT B1R resulted in the diminution of the intact 65-kDa HB2 species and the appearance of heterogeneous products at 30–40 kDa (Fig. 2A, lane 3). The B1R-promoted effect on B2R was also observed in a highly enriched plasma membrane fraction of the cell (Fig. 2C, top panel, lane 4). The effect of B1R on B2R was dose-dependent (Fig. 2B, lanes 2–6) and was paralleled by the loss of cell surface binding sites for the selective B2R agonist [3H]BK (Fig. 2D) (69 ± 8% of control binding at 2 µg of B1R DNA). On the other hand, B2R did not alter either the integrity of the 35-kDa FB1 (Fig. 2C, bottom panel, lanes 4 and 5) or the cell surface binding sites for the selective B1R agonist [3H]DK (Fig. 2D). Neither the WT serotonin 5HT2A receptor nor the WT chemokine receptor CXCR4 had any apparent effect on B2R integrity (Fig. 2A, lanes 4 and 5) or [3H]BK binding (100 ± 2% of control binding at 2 µg of CXCR4 DNA). Furthermore, B1R had no apparent effect on the integrity of FLAG-tagged CXCR4 (data not shown). To directly address whether B2R was proteolytically degraded, we compared HB2 expressed alone and together with B1R, immunoprecipitated with anti-B2R-(310–364) antibody, and then immunoblotted with anti-HA antibody. Proteolytic cleavage would be indicated if, after introduction of B1R, the HA antibody, which recognizes the B2 receptor N-terminal tail, reacted less with the anti-B2R-(310–364) immunoprecipitate, which recognizes the B2 receptor C-terminal tail. Fig. 2E shows an almost complete loss of anti-HA reactivity after co-expression of HB2 with B1R. These results provide direct evidence that the decrease in B2R molecular mass is caused by proteolytic B2R cleavage.



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FIG. 2.
B1R-dependent proteolytic degradation of B2R. A, cells transfected with pcDNA3 (-; lane 1), HB2 (lane 2), HB2 + WT B1R (B1) (lane 3), HB2 + WT 5HT2A (2A) (lane 4), HB2 + WT CXCR4 (CXC) (lane 5), WT 5HT2A + WT B1R (lane 6), and WT CXCR4 + WT B1R (lane 7) were immunoblotted with anti-HA antibody. pcDNA3 was used to equalize the amount of DNA transfected. B, cells transfected with pcDNA3 and HB2 without and with increasing amounts of WT B1R were immunoblotted with HA antibody. C, cells transfected with pcDNA3 (-; lane 1), HB2 (lanes 2 and 3), and FB1 (lane 5), either individually or together (lane 4). A plasma membrane-enriched cellular fraction was immunoblotted with anti-HA antibody or anti-FLAG antibody. D, cells were transfected with HB2 and FB1 in the absence and presence of increasing amounts of WT B1R and B2R, respectively, and cell surface receptor binding was then analyzed. Data are presented as mean ± S.E. of at least three experiments. E, cells transfected with pcDNA3 vector (-; lane 1) and HB2 without (lane 2) and with WT B1R (lanes 3) were immunoprecipitated (IP) with anti-B2R-(310–364) antibody and immunoblotted (IB) with anti-HA antibody. In AC and E, molecular mass standards (in kDa) (left side arrows) and major receptor species (right side arrows) are indicated, and the results are representative of experiments performed three times.

 
Spontaneous Formation of Proteolytic Hetero-oligomeric B1R and B2R Complexes—Relatively stable detergent-resistant homo-oligomeric B1R structures were readily apparent on gels (Fig. 1A, lane 2, and Fig. 2C, bottom panel, lanes 4 and 5). To determine whether the B1R-promoted degradation of B2R involved receptor hetero-oligomerization, attempts were made to co-immunoprecipitate the two receptors. Immunoprecipitation of HB2 with HA antibodies yielded the co-precipitation of FB1 (Fig. 3A, top panel, lane 4). Also, the FB1 immunoprecipitate contained HB2 activity whether FB1 had been captured with anti-FLAG (Fig. 3A, bottom panel, lane 3) or anti-B1R-(317–353) antibodies (Fig. 3B, lane 2). Interestingly, this HB2 activity was exclusively that of the degradation products. Mixing lysates from cells expressing each receptor individually did not yield any FB1 activity in the HB2 precipitate (Fig. 3C, lane 4). Furthermore, FLAG-tagged CXCR4 did not co-precipitate with HB2 (Fig. 3C, lane 5). These results show that B1R and B2R form a hetero-oligomeric complex in the cell, and this complex is specifically composed of the intact 35-kDa B1R and the proteolytically degraded B2R products. Fig. 3D shows that the B2R products were distinct from and smaller than the deglycosylated B2R, providing further evidence that the products are the result of proteolytic degradation. The degree of B1R-promoted B2R proteolysis is difficult to assess but assumed to be relatively extensive because (a) probably only a fraction of the cells is co-transfected with our transient transfection protocol and (b) very little, if any, intact B2R is complexed with B1R.



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FIG. 3.
Identification of proteolytic hetero-oligomeric B1R and B2R complexes. A, cells transfected with pcDNA3 (-; lanes 1 and 6), FB1 (lane 2), and HB2 (lane 5), either individually or together (lanes 3 and 4), were immunoprecipitated (IP) and immunoblotted (IB) with FLAG antibody or HA antibody. B, cells transfected with pcDNA3 (-; lanes 1 and 5) and HB2 without (lane 4) and with FB1 (lanes 2 and 3) were immunoprecipitated (IP) and immunoblotted (IB) with HA antibody or B1-(317–353) antibody. C, cells transfected with pcDNA3 (-; lane 1), FB1 (lane 2), FLAG-tagged CXCR4 (FCXC) (lane 6), and HB2 with FB1 (lane 3) or FCXC (lane 5) were immunoprecipitated (IP) and immunoblotted (IB) with HA antibody or FLAG antibody. In lane 4, lysates of cells transfected with FB1 and HB2 individually were mixed and immunoprecipitated with HA antibody and immunoblotted with FLAG antibody. D, cells transfected with pcDNA3 (lane 4) and HB2 without (lanes 1 and 2) and with B1R (lane 3) were immunoprecipitated with anti-B2-(310–364) antibody (lanes 1 and 2) and anti-B1-(317–353) antibody and immunoblotted with HA antibody. The immunoprecipitates in lanes 1 and 2 were treated with PNGase F as described in Fig. 1. In AD, molecular mass (in kDa) standards (left side arrows) and receptor species (right side arrows) are indicated, and the results are representative of experiments performed three times.

 
Plasma Membrane Localization of the Hetero-oligomeric B1R and B2R Complexes—To establish a plasma membrane localization of the proteolytic B1R·B2R complex beyond that of subcellular fractionation (see Fig. 2C), cell surface biotinylation with a membrane-impermeable biotin analogue was performed. Fig. 4, lane 2, clearly shows the presence of biotinylated cell surface FB1. Interestingly, a clearly detectable amount of these receptors was present in the HB2 precipitate (Fig. 4, lane 3). This association was cell-dependent because mixing lysates from biotinylated cells expressing each receptor individually did not result in biotinylated receptor co-precipitation (Fig. 4, lane 4).



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FIG. 4.
Identification of plasma membrane hetero-oligomeric B1R and B2R complexes by cell surface biotinylation. Cells transfected with pcDNA3 (-; lane 1), FB1 (lane 2), or FB1 with HB2 (lane 3) were biotinylated, immunoprecipitated (IP) with HA antibody or FLAG antibody, and stained with streptavidin conjugated to horseradish peroxidase. In lane 4, biotinylated cells transfected with FB1 and HB2 individually were mixed and immunoprecipitated with HA antibody. Molecular mass (in kDa) standards (left side arrows) and receptor species (right side arrows) are indicated, and the results are representative of experiments performed three times.

 
Plasma membrane-associated hetero-oligomeric B2R and B1R complexes were also investigated using immunoelectron microscopy. To do so, FLAG antibodies were labeled with 5-nm gold particles, whereas the HA antibodies were labeled with 11-nm gold particles. The antibodies were then incubated with cells co-expressing FB1 and HB2 at 4 °C. As shown in Fig. 5, the gold particles were located exclusively on the surface of the plasma membrane. Furthermore, the majority of the gold particles existed as dimeric combinations of one 5-nm particle and one 11-nm particle. These results provide direct evidence that B1R and B2R form dimers in the plasma membrane. No higher order complexes were identified. However, such complexes cannot be completely excluded because steric hindrance may prevent them from being labeled.



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FIG. 5.
Identification of plasma membrane hetero-oligomeric B1R and B2R complexes by immunoelectron microscopy. Cells were incubated with 5-nm gold-labeled FLAG antibodies and 11-nm gold-labeled HA antibodies for 30 min at 4 °C. The cells were then processed as described under "Experimental Procedures." The bar at the bottom indicates 0.2 µm. The arrows indicate some 5- and 11-nm gold heterodimer complexes. Inset, magnified area containing complexes.

 
Kinetics of Hetero-oligomeric B1R and B2R Complex Formation—To address which receptor is rate-limiting in the complex formation, FB1 and HB2 were first transfected at different DNA ratios (µg/µg) and co-precipitated with HA antibodies. Co-precipitation was dose-dependent because maintaining the ratio at 2 but increasing the total amount of transfected receptors from 2:1 to 4:2 increased the amount of FB1 in the HB2 precipitate (Fig. 6A). Increasing the amount of HB2 relative to FB1 by 2-fold (2:1 to 2:2 or 4:1 to 4:2) decreased the amount of FB1 in the precipitate, whereas increasing the amount of FB1 relative to HB2 by 2-fold (2:1 to 4:1 or 2:2 to 4:2) dramatically increased the amount. Thus, B1R is rate-limiting in complex formation. Furthermore, the complex forms spontaneously because neither the B1R agonist DK nor the B2 agonist BK nor kallidin, a less selective receptor agonist, had any apparent effect on the amount of FB1 in the precipitate (Fig. 6B).



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FIG. 6.
Kinetics of hetero-oligomeric B1R and B2R complex formation. A, cells transfected with FB1 and HB2 in ratios of 2:1 (lane 1), 2:2 (lane 2), 4:1 (lane 3), and 4:2 (lane 4) (µg DNA/µg DNA) were immunoprecipitated (IP) with HA antibody and immunoblotted (IB) with FLAG antibody. B, cells transfected with FB1 without (lane 1) and with HB2 (lanes 2–5) were incubated in the absence (lanes 1 and 2) and presence of DK (lane 3), BK (lane 4), and kallidin (KD) (lane 5) for 30 min at 37 °C, and immunoprecipitated (IP) with FLAG antibody or HA antibody and immunoblotted (IB) with FLAG antibody. Molecular mass (in kDa) standards (left side arrows) and receptor species (right side arrows) are indicated, and the results are representative of experiments performed three times.

 
Increased Signaling of the Hetero-oligomeric B1R and B2R Complexes—Next, we analyzed whether the spontaneous B1R and B2R interaction is also indicated at the functional level. We have shown previously that B1R is constitutively active because it dose-dependently increases PI hydrolysis in the absence of agonist (Fig. 7B, Mock), whereas B2R is essentially inactive on its own (Fig. 7A, Mock) (7). Interestingly, in the presence of a constant amount of B1R, which by itself partially increased PI hydrolysis, B2R dose-dependently increased basal PI hydrolysis with a slope that was at least 14-fold higher than that in the absence of B1R (Fig. 7A). An increase (2-fold) in constitutive signaling also occurred when B2R was held constant and B1R was varied (Fig. 7B). Neither mock-transfection with pcDNA3 nor co-transfection with CXCR4 caused a change in B2R activity (data not shown). Fig. 7C shows that B1R and B2R co-expression also increased the ability of B1R to be stimulated by 1 µM desArg9BK. This response remained B1R-specific because desArg10[Leu9]kallidin, a highly selective B1 antagonist, effectively inhibited the response, whereas the selective B2 inverse agonist NPC17731did not inhibit the response (data not shown). Furthermore, NPC17731had no effect on the increase in basal PI hydrolysis caused by coexpression, excluding the conversion of B2R to a more active conformational state as the source of this increase (20, 21). These results show that the spontaneous interaction of B1R and B2R is functionally significant and translates into an increased coupling efficacy of the receptor to Gq and subsequent phospholipase C{beta} activity.



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FIG. 7.
Spontaneous synergism in constitutive B1R and B2R signaling. In A and B, cells were transfected with varying amounts of WT B2R (A) and WT B1R (B) in the absence (•) and presence ({circ}) of a constant amount of WT B1R (A) and WT B2R (B) and assayed for PI hydrolysis. Note the difference in the y axis scale in A and B. The results are from four to eight independent experiments. C, cells were co-transfected with varying amounts of WT B2R and WT B1R and stimulated with 1 µM DK assayed for PI hydrolysis. Data are presented as the mean ± S.E. of at least three experiments where 100% control is agonist stimulation in cells transfected with B1R alone.

 

    DISCUSSION
 TOP
 ABSTRACT
 INTRODUCTION
 EXPERIMENTAL PROCEDURES
 RESULTS
 DISCUSSION
 REFERENCES
 
Our observation is, to our knowledge, the first to implicate proteolysis of a G protein-coupled receptor in its participation in an oligomeric plasma membrane receptor complex. Such complexes are novel species that may have broad significance in receptor signaling and regulation, and the complexes and the involved protease(s) could represent new targets for therapeutic intervention.

Multiple approaches were used to show spontaneously formed functional hetero-oligomeric B1R and B2R complexes. These include receptor co-immunoprecipitation using epitope-specific antibodies against both the N-terminal and C-terminal domains of the receptors, direct identification of complexes by immunoelectron microscopy using antibodies labeled with differently sized gold particles, and constitutive receptor activity. The immunoelectron microscopy indicated the presence of receptor dimers.

Regulated proteolytic degradation of plasma membrane receptors through endocytic targeting to lysosomes is well characterized (22). Recently, increased attention has been drawn to plasma membrane proteolysis in receptor function (2325). It is most likely that the degraded B2R products are formed after B1R and B2R complex formation rather than before it. Indeed, when in a complex with B1R, B2R may become susceptible to an intracellular or membrane-bound protease that may or may not have been recruited by B1R or to which B2R is recruited by B1R. Furthermore, hetero-oligomeric B2R may be more prone to degradation than homo-oligomeric B2R, which has been shown to exist (26). Whether or not an endocytic mechanism is involved in the proteolysis is not clear, but this possibility cannot be excluded because the complex may recycle from an intracellular degradative compartment back to the plasma membrane. Alternatively, proteolysis may occur while the receptors are in the endoplasmic reticulum or en route to the surface, if complexes are capable of forming at these points.

The presence of a spontaneously formed proteolytic receptor complex in the plasma membrane that correlates with increased constitutive and agonist-stimulated receptor signaling efficacy argues strongly that the complex is functionally significant. The lack of effect of the B2R inverse agonist NPC17731suggests that the increase involves an allosteric enhancement by the B2R fragment of the inherent signaling of B1R. Indeed, this effect may be related to that which B2R elicits by hetero-oligomerizing with the angiotensin II AT1 receptor (27).

The possibility that B2R and B1R are typical protease-activated receptors seems unlikely because kinins are their natural receptor ligands. It has been reported that B2R is activated in cell culture by some extracellular proteases, which could be released from neutrophils and bacteria during insult, but without any direct evidence for receptor proteolysis (28). Starving the cells in the absence of serum for 24 h had no effect on B2R degradation, suggesting a cell-associated plasma membrane-bound or intracellular protease rather than a serum-derived extracellular protease as the cause of the degradation.

Induction of B1R expression by pro-inflammatory cytokines such as interleukin-1{beta} is an important mechanism underlying the adaptation of the kinin-mediated inflammatory pain response from a B2 type to a B1 type during chronic insult. Considering that these receptor subtypes are co-expressed on numerous cellular structures including primary sensory neurons, which are critical for the pain response, a proteolytic B1R·B2R complex could be involved in assuring the fading of the B2-type response and in augmenting the kinin signal. Indeed, a proteolytic plasma membrane mechanism to remove B2R may be necessary because this receptor (a) recycles relatively rapidly after agonist-promoted internalization (29, 30) and (b) down-regulates to a very limited extent (if at all), even after prolonged agonist exposure (days) (30, 31).


    FOOTNOTES
 
* This work was supported by National Institutes of Health Grant GM41659, the Swedish Research Council, Alfred Österlunds Stiftelse, Crafordska Stiftelsen, Konung Gustav V:s 80-årsfond, Kocks Stiftelser, and the Faculty of Medicine, Lund University. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Back

|| To whom correspondence should be addressed: Division of Molecular Neurobiology, Wallenberg Neuroscience Center, Lund University, BMC, A12, Sölvegatan 17, SE-22184 Lund, Sweden. Tel.: 46-46-2223944; Fax: 46-46-2220568; E-mail: fredrik.leeb-lundberg{at}mphy.lu.se.

1 The abbreviations used are: B1R, B1 receptor; B2R, B2 receptor; FB1, FLAG-tagged B1 receptor; HB2, hemagglutinin-tagged B2 receptor; BK, bradykinin; DK, desArg10kallidin; PI, phosphoinositide; WT, wild-type; HA, hemagglutinin. Back



    REFERENCES
 TOP
 ABSTRACT
 INTRODUCTION
 EXPERIMENTAL PROCEDURES
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Couture, R., Harrisson, M., Vianna, R. M., and Cloutier, F. (2001) Eur. J. Pharmacol. 429, 161-176[CrossRef][Medline] [Order article via Infotrieve]
  2. Dray, A., and Perkins, M. (1993) Trends Neurosci. 16, 99-104[CrossRef][Medline] [Order article via Infotrieve]
  3. Marceau, F., Hess, J. F., and Bachvarov, D. R. (1998) Pharmacol. Rev. 50, 357-386[Abstract/Free Full Text]
  4. Pesquero, J. B., Araujo, R. C., Heppenstall, P. A., Stucky, C. L., Silva, J. A., Jr., Walther, T., Oliveira, S. M., Pesquero, J. L., Paiva, A. C., Calixto, J. B., Lewin, G. R., and Bader, M. (2000) Proc. Natl. Acad. Sci. U. S. A. 97, 8140-8145[Abstract/Free Full Text]
  5. Ni, A., Yin, H., Agata, J., Yang, Z., Chao, L., and Chao, J. (2003) J. Biol. Chem. 278, 219-225[Abstract/Free Full Text]
  6. Mathis, S. A., Criscimagna, N. L., and Leeb-Lundberg, L. M. F. (1996) Mol. Pharmacol. 50, 128-129[Abstract]
  7. Leeb-Lundberg, L. M. F., Kang D. S., Lamb, M. E., Mathis, S., and Fathy, D. B. (2001) J. Biol. Chem. 276, 8785-8792[Abstract/Free Full Text]
  8. Angers, S., Salahpour, A., and Bouvier, M. (2002) Annu. Rev. Pharmacol. Toxicol. 42, 409-435[CrossRef][Medline] [Order article via Infotrieve]
  9. Jones, K. A., Borowsky, B., Tamm, J. A., Craig, D. A., Durkin, M. M., Dai, M., Yao, W. J., Johnson, M., Gunwaldsen, C., Huang, L. Y., Tang, C., Shen, Q., Salon, J. A., Morse, K., Laz, T., Smith, K. E., Nagarathnam, D., Noble, S. A., Branchek, T. A., and Gerald, C. (1998) Nature 396, 674-679[CrossRef][Medline] [Order article via Infotrieve]
  10. Kaupmann, K., Malitschek, B., Schuler, V., Heid, J., Froestl, W., Beck, P., Mosbacher, J., Bischoff, S., Kulik, A., Shigemoto, R., Karschin, A., and Bettler, B. (1998) Nature 396, 683-687[CrossRef][Medline] [Order article via Infotrieve]
  11. White, J. H., Wise, A., Main, M. J., Green, A., Fraser, N. J., Disney, G. H., Barnes, A. A., Emson, P., Foord, S. M., and Marshall, F. H. (1998) Nature 396, 679-682[CrossRef][Medline] [Order article via Infotrieve]
  12. Wohlfart, P., Dedio, J., Wirth, K., Schölkens, B. A., and Wiemer, G. (1997) J. Pharmacol. Exp. Ther. 280, 1109-1116[Abstract/Free Full Text]
  13. Tropea, M. M., Gummelt, D., Herzig, M. C. S., and Leeb-Lundberg, L. M. F. (1993) J. Pharmacol. Exp. Ther. 264, 930-937[Abstract/Free Full Text]
  14. Ma, Q. P. (2001) Neuroscience 107, 665-673[CrossRef][Medline] [Order article via Infotrieve]
  15. Barki-Harrington, L., Bookout, A. L., Raj, G. V., Leeb-Lundberg, L. M. F., and Daaka, Y. (2003) Biochem. J. 371, 581-587[CrossRef][Medline] [Order article via Infotrieve]
  16. Phagoo, S. B., Poole, S., and Leeb-Lundberg, L. M. F. (1999) Mol. Pharmacol. 56, 325-333[Abstract/Free Full Text]
  17. Smart, E. J., Ying, Y. S., Mineo, C., and Anderson, R. G. (1995) Proc. Natl. Acad. Sci. U. S. A. 92, 10104-10108[Abstract/Free Full Text]
  18. Lamb, M. E, Zhang, C., Shea, T., Kyle, D. J., and Leeb-Lundberg, L. M. F. (2002) Biochemistry 41, 14340-14347[CrossRef][Medline] [Order article via Infotrieve]
  19. Baschong, W., and Wrigley, N. G. (1990) J. Electron Microsc. Technol. 14, 313-323[CrossRef][Medline] [Order article via Infotrieve]
  20. Leeb-Lundberg, L. M. F., Mathis, S. A., and Herzig, M. C. S. (1994) J. Biol. Chem. 269, 25970-25973[Abstract/Free Full Text]
  21. Fathy, D. B., Leeb, T., Mathis, S. A., and Leeb-Lundberg L. M. F. (1999) J. Biol. Chem. 274, 29603-29606[Abstract/Free Full Text]
  22. von Zastrow, M. (2001) Parkinsonism Relat. Disord. 7, 265-271[CrossRef][Medline] [Order article via Infotrieve]
  23. Brown, M., Ye, J., Rawson, R. B., and Goldstein, J. L. (2000) Cell 100, 391-398[CrossRef][Medline] [Order article via Infotrieve]
  24. Coughlin, S. (2000) Nature 407, 258-264[CrossRef][Medline] [Order article via Infotrieve]
  25. Prenzel, N., Zwick, E., Daub, H., Leserer, M., Abraham, R., Wallasch, C., and Ullrich, A. (1999) Nature 402, 884-888[Medline] [Order article via Infotrieve]
  26. AbdAlla, S., Zaki, E., Lother, H., and Quitterer, U. (1999) J. Biol. Chem. 274, 26079-26084[Abstract/Free Full Text]
  27. AbdAlla, S., Lother, H., and Quitterer, U. (2000) Nature 407, 94-98[CrossRef][Medline] [Order article via Infotrieve]
  28. Hecquet, C., Tan, F., Marcic, B. M., and Erdös, E. G. (2000) Mol. Pharmacol. 58, 828-836[Abstract/Free Full Text]
  29. Munoz, C. M., Cotecchia, S., and Leeb-Lundberg, L. M. F. (1993) Arch. Biochem. Biophys. 301, 336-344[CrossRef][Medline] [Order article via Infotrieve]
  30. Bachvarov, D. R., Houle, S., Bachvarova, M., Bouthillier, J., Adam, A., and Marceau, F. (2001) J. Pharmacol. Exp. Ther. 297, 19-26[Abstract/Free Full Text]
  31. Blaukat, A., Micke, P., Kalatskaya, I., Faussner, A., and Müller-Esterl, W. (2003) Am. J. Physiol. Heart Circ. Physiol. 284, H1909-H1916[Abstract/Free Full Text]

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