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-Chain Interaction1
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* Immunotherapy Laboratory, Department of Immunology, University Medical Center Utrecht, Utrecht, The Netherlands;
Department Experimental Immunohematology, Sanquin Research at CLB and Landsteiner Laboratory of the Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands;
Department of Molecular Cell Biology and Immunology, Free University Medical Center, Amsterdam, The Netherlands;
Department of Surgical Oncology, Free University Medical Center, Amsterdam, The Netherlands; and
¶ Genmab, Utrecht, The Netherlands
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Abstract |
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RI, CD89) is expressed on myeloid cells and can trigger phagocytosis, tumor cell lysis, and release of inflammatory mediators. The functions of FcRI and activating receptors for IgG (Fc
RI and FcRIII) are dependent on the FcR -chain dimer. This study increases our understanding of the molecular basis of the FcRI-FcR -chain transmembrane interaction, which is distinct from that of other activatory FcRs. FcRI is unique in its interaction with the common FcR -chain, because it is based on a positively charged residue at position 209, which associates with a negatively charged amino acid of FcR -chain. We explored the importance of the position of this positive charge within human FcRI for FcR -chain association and FcRI functioning with the use of site-directed mutagenesis. In an FcRI R209L/A213H mutant, which represents a vertical relocation of the positive charge, proximal and distal FcR -chain-dependent functions, such as calcium flux, MAPK phosphorylation, and IL-2 release, were similar to those of wild-type FcRI. A lateral transfer of the positive charge, however, completely abrogated FcR -chain-dependent functions in an FcRI R209L/M210R mutant. By coimmunoprecipitation, we have demonstrated the loss of a physical interaction between FcR -chain and FcRI M210R mutant, thus explaining the loss of FcR -chain-dependent functions. In conclusion, not only the presence of a basic residue in the transmembrane region of FcRI, but also the orientation of FcRI toward the FcR -chain dimer is essential for FcR -chain association. This suggests the involvement of additional amino acids in the FcRI-FcR -chain interaction. |
Introduction |
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RI or CD89, is expressed on neutrophils, monocytes, eosinophils, macrophages, dendritic cells, and Kupffer cells (1, 2, 3, 4, 5). FcRI plays an important role in protection against infections. Activation of the receptor by IgA-immune complexes initiates numerous immune effector functions, including phagocytosis, oxidative burst, cytokine release, and degranulation (6, 7, 8). FcRI is also capable of Ab-dependent cell-mediated cytotoxicity in cooperation with complement receptor CR3 (9, 10). FcRI is not only important in host defense, but may also be valuable as a target for Ab therapy (11, 12, 13).
FcRI is a type I transmembrane receptor with two extracellular Ig-like domains, a hydrophobic transmembrane domain, and a short cytoplasmic tail (14, 15). For several functions, including calcium mobilization and cytokine production, the receptor critically depends on the associated FcR -chain dimer (16, 17, 18), although FcRI unassociated with the FcR -chain can retain some functions (19, 20).
The FcR -chain contains a so-called ITAM. FcRI ligation initiates ITAM phosphorylation, which mediates signaling further downstream (21, 22, 23, 24). A stable complex of FcRI and FcR -chain is important for FcR -chain-dependent functions. This association is based on oppositely charged amino acids in the transmembrane region of both molecules (17).
Unlike other activating FcRs (FcRI, FcRIII, and Fc
RI), a positively charged arginine at position 209 is unique for FcRI (25). This arginine at position 209 in the transmembrane region of FcRI can be replaced by a positively charged histidine without losing FcR -chain-dependent functions (17). It was recently shown that FcRI has an exclusive feature to exert a dual function: activatory function, shared by other FcRs, and an unique capacity to trigger inhibitory functions (26). Although FcRI is clearly an FcR, it is more related to members of the leukocyte receptor cluster (LRC),3 including the leukocyte Ig-like receptors and killer Ig-like receptors, based on amino acid sequence identity (27, 28). Within the LRC family, an N-terminal positively charged arginine is highly conserved among all activatory receptors (27, 29), with the exception of the killer activatory receptors (KARs), which bear a positively charged lysine in the center of their transmembrane region (27). Interestingly, the KARs interact with DAP12 (30), whereas other LRC stimulatory receptors associate with the common FcR -chain (31), suggesting that a positive charge located at the N-terminal part is required for FcR -chain association. Furthermore, FcR -chain association of the other activating FcRs is based on nonbasic, polar residues in the C-terminal part of the transmembrane region (32).
Taken together, a basic amino acid in the transmembrane region of FcRI is essential for FcR -chain-dependent functions. Given the conserved N-terminal position of the positively charged residue within the LRC family, we wondered whether optimal FcRI functioning requires this basic residue to be at position 209. To better define the nature of this interaction, FcRI mutants were generated in which the positive charge was relocated to new positions within the N-terminal part of its transmembrane region. Our data support the idea that the vertical position of this positively charged amino acid is crucial for functional assembly of the FcRI-FcR -chain complex, and these findings can possibly be extrapolated to other activating LRC members.
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Materials and Methods |
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RI cDNAs
The insertion of human FcRI cDNA into pCAV vector and murine FcR -chain cloned into pNUT vector were described previously (17). Construction of the FcRI R209L mutant was also described (17). The same strategy, based on overlap-extension PCR with mutated oligonucleotide primers, was used for the construction of both the FcRI R209L/A213H and the R209L/M210R mutant using FcRI-R209L cDNA as a template.
Generation of stable transfectants
Generation of stable cell lines expressing the mutant FcR was performed as described previously (17). Briefly, the transfectants were made by electroporation of IIA1.6 cells with the mutant FcRI and the FcR -chain and subsequent selection with methotrexate (Pharmachemie); several subclones were tested in the described assays. The expression of FcRI was confirmed by flow cytometry, and FcR -chain was detected by Western blotting (see below).
Cells
The murine CD5+ B cell/macrophage cell line IIA1.6 (33) was cultured in RPMI 1640 (Invitrogen Life Technologies; 2 mM glutamine and 25 mM HEPES) supplemented with 10% heat-inactivated FCS (Integro), 100 U/ml penicillin (Invitrogen Life Technologies), and 100 µg/ml streptomycin (Invitrogen Life Technologies). FcRI transfectants were maintained in the same medium supplemented with methotrexate (10 µM).
Flow cytometry
FcRI expression was measured by incubating the cells with mAb A59-PE (BD Pharmingen) or with an isotype control (mIgG1-RPE; DakoCytomation) for 30 min at 4°C. Cells were washed twice with PBS, 1% BSA, and 0.1% NaN3 and were analyzed by FACSCalibur (BD Pharmingen).
Western blotting
Total lysates of the transfectants were prepared in reducing Laemmli sample buffer and analyzed by SDS-PAGE on 15% polyacrylamide gels for detection of FcR -chain. The polyacrylamide gels were transferred on polyvinylidene difluoride membranes (Immobilon-P; Millipore), blocked with 5% low fat milk powder in PBS for 1 h at room temperature. For FcR -chain detection, the membranes were probed with a rabbit polyclonal anti-human -chain (1:1000; Upstate Biotechnology) for 1 h at room temperature, followed by incubation for 45 min with goat anti-rabbit IgG (H+L)-HRP (1:10,000; Pierce). After extensive washing in PBS and 0.05% Tween 20, bound Ab was detected by chemiluminescence (Amersham Biosciences).
Ligand binding assay
As ligand, IgA-coated, 96-well plates were used to assess binding of the transfectants to IgA. Briefly, 96-well plates were coated overnight at 4°C with 100 µl of human IgA serum (ITK Diagnostics; 10 µg/ml) or 100 µl BSA (10 µg/ml; Roche) as a negative control. The next day, the plates were washed twice with PBS and 1% BSA. Cells (5 x 106) were prepared by incubation with 1 µl of calcein-AM (20 mM; Molecular Probes) for 30 min at 37°C. After washing, 2 x 105 cells were added per well of the coated plates. After incubation for 30–60 min at 4°C, plates were directly measured on a Fluoriscan (Molecular Probes) at 485 nm; this reading was designated input. Next, plates were washed to remove nonadherent cells until the fluorescence of the BSA-coated wells was reduced to the background level. Subsequently, adhesion of the transfectants to IgA was expressed as fluorescence after washing the plate divided by fluorescence before washing the plate (method adapted from Ref.34). The ligand binding capacity of the FcRI wild-type (Wt) transfectant was set at 100%. The ligand binding capacity of the FcRI mutant receptor was calculated as a percentage compared with the FcRI Wt receptor. Data are shown as the mean ± SD.
FcRI internalization
Cells (2 x 105) were loaded with mAb anti-human CD89 or mIgG1 isotype control for 60 min at 4°C. After washing, the cells were incubated with a second Ab, goat F(ab')2 anti-mouse IgG1. At this point the samples were split in two. One sample was kept at 4°C to measure the total surface expression of FcRI, and the other sample was kept at 37°C for the indicated time periods. After these incubation periods, the surface FcRI expression was measured by staining the retained surface receptors with a third Ab ((RG-IgG(H+L)-FITC conjugated; Jackson ImmunoResearch Laboratories) for 30 min at 4°C. After washing, the samples were analyzed for FcRI surface expression on a FACSCalibur. Internalization of FcRI in the 37°C samples was calculated as a percentage of the total FcRI expression measured in the 4°C samples.
Calcium mobilization assay
Intracellular-free calcium levels were measured using cells simultaneously labeled with 1,5-(and-6)-carboxyseminaphtorhoda fluor 1-acetoxymethyl ester, acetate (2.8 µM), and fluo 3-AM (1.4 µM; Molecular Probes) by incubation for 30 min at 37°C in RPMI 1640 (2 mM glutamine and 25 mM HEPES) supplemented with 1% heat-inactivated FCS, 100 U/ml penicillin, and 100 µg/ml streptomycin. Cells were washed and incubated with anti-human CD89 Ab or mIgG1 isotype control Ab, incubated for 30 min at 4°C, washed, and resuspended in RPMI 1640 (2 mM glutamine and 25 mM HEPES) supplemented with 1% FCS. Calcium mobilization was measured on a FACSCalibur. In the first 20 s, a baseline value for the intracellular-free calcium concentration was measured. Subsequently, FcRI-specific calcium mobilization was measured by adding 6 µl of goat F(ab')2 anti-mouse IgG1 (Southern Biotechnology). In parallel, for each cell line the release of calcium after BCR cross-linking was assessed by addition of goat F(ab')2 anti-mouse IgG (Jackson ImmunoResearch Laboratories).
MAPK phosphorylation assay
Cells (2 x 105) were incubated with anti-FcRI (A77) for 30 min at room temperature. After washing twice with RPMI 1640, F(ab')2 of goat anti-mouse IgG1 Ab was added for the indicated time periods at 37°C to cross-link FcRI. Reactions were stopped by addition of 70 µl of reducing SDS-PAGE sample buffer. Cross-linking of the BCR by addition of goat F(ab')2 anti-mouse IgG for 2 min at 37°C served as a positive control. Background levels of MAPK phosphorylation were determined by omitting the cross-linking Ab or by omitting all Abs. Western blotting of these samples is described above. Membranes were blocked in 5% BSA (Roche) and probed with anti-phospho-p44/42 MAPK or anti-total MAPK Ab for 2 h (Cell Signaling Technology). After washing, membranes were incubated for 45 min with peroxidase-conjugated goat anti-rabbit Ab.
IL-2 production
Transfectants were incubated for 30 min at 4°C with mAb anti-human CD89 or with mIgG1 isotype Ab as a control. After washing with PBS, goat F(ab')2 anti-mouse IgG1 in complete medium was added to the cells and incubated overnight at 37°C. As a positive control, goat F(ab')2 anti-mouse IgG was used to trigger the BCR. After overnight incubation, supernatants were isolated, and IL-2 production was measured by ELISA. For this purpose, a 96-well plate was coated overnight with the capture mAb, rat anti-mouse IL-2 (BD Pharmingen; 0.5 mg/ml) in 100 µl of binding buffer (0.1 M Na2HPO4 (pH 9.0)). Subsequently, the plate was blocked with 100 µl of 1% BSA in PBS for 1 h at room temperature, and 1/3 diluted samples were incubated for 2 h at room temperature. Next, a mixture of detecting Abs was added (biotin-rat anti-mouse IL-2 (BD Pharmingen) and streptavidin-peroxidase conjugated (Roche)). IL-2 production was measured at 405 nm on a MultiscanRC (Thermo Labsystems). Each supernatant was measured individually in the IL-2 ELISA.
Coimmunoprecipitation
Protein A/G agarose beads (Santa Cruz Biotechnology) were incubated with 3 µg of purified anti-human CD89 (0.5 mg/ml; BD Biosciences) or mIgG1 isotype control Ab (Sigma-Aldrich) in PBS and 1% BSA at 4°C for a minimum of 2 h for each immunoprecipitation. IIA1.6 cells (1 x 107 cells/immunoprecipitation) were collected by centrifugation and lysed in a digitonin lysis buffer (1% digitonin, 150 mM NaCl, 0.12% Triton X-100, and 20 mM triethanolamine) for 30 min at 4°C. The lysate was clarified by centrifugation at 15,000 rpm for 10 min at 4°C, and the supernatant was transferred to the Ab-coated beads. This mixture was incubated overnight at 4°C, then beads were isolated by centrifugation at 4,000 rpm for 10 min at 4°C and washed twice in digitonin lysis buffer. Precipitates were resuspended in Laemmli sample buffer and checked for FcR -chain by Western blotting.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionDisclosuresReferences |
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RI transmembrane mutants
A functional association between FcRI and FcR -chain occurs when a positively charged residue (R209 or R209H) is present within the FcRI transmembrane domain, whereas a negative (R209D) or uncharged (R209L) amino acid at position 209 results in loss of FcRI functioning (17, 26). To investigate whether not only the presence of a positive charge, but also its localization in the transmembrane region of FcRI, is a prerequisite for functional FcR -chain association, we constructed two double mutants, FcRI R209L/M210R (M210R) and FcRI R209L/A213H (A213H; Fig. 1A). We relocated the positive charge from position 209 to either position 210 or 213 in the N-terminal part. We focused on the N-terminal region because more C-terminal-located positively charged amino acid would probably interact with DAP12 rather than FcR -chain (18, 27). The functionality of a lateral or vertical relocation of a positive charge was determined in FcRI M210R and FcRI A213H (Fig. 1B). We decided to replace the methionine (M210) and the alanine (A213) with positively charged arginine and histidine, respectively, to minimally change the size of the amino acid side chains. Stable transfectants were generated by cotransfecting individual FcRI constructs with the murine FcR -chain in the murine IIA1.6 cell line. FACS analyses showed all transfectants to express similar levels of FcRI (Fig. 2A). Protein expression of FcR -chain was detected by Western blotting in the transfectants at similar levels (Fig. 2B).
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RI mutants mediate FcRI ligand binding and receptor internalization
To exclude the possibility of a conformational change in the extracellular FcRI part by introduction of mutations in the transmembrane region of the FcR and differences in the activation state of the receptor (35), we tested ligand binding and internalization of FcRI. First, the FcRI ligand binding capacity was determined using plates coated with human serum IgA and fluorescence-labeled cells (34). Both FcRI A213H and FcRI M210R cells bound to IgA-coated plates with similar capacity as FcRI Wt (Fig. 3A). Second, we examined FcRI internalization upon receptor cross-linking. As shown in Fig. 3B, FcRI Wt and FcRI mutants internalized with similar kinetics. These data demonstrate that both FcRI mutants retain intact -chain properties.
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RI M210R mutant signaling is abrogated
FcRI cross-linking is known to trigger calcium release from intracellular stores (36). To test FcRI functioning after relocation of the positive charge, we assessed the ability of both FcRI mutants to trigger intracellular calcium release. We measured FcRI-specific calcium flux after cross-linking with anti-FcRI mAb (A59) and goat anti-mouse IgG1 (Fig. 4, A and B). Using an isotype control mIgG1 Ab and the secondary Ab, goat anti-mouse IgG1 (negative), did not result in a calcium flux. The FcRI Wt transfectant showed a maximum calcium flux at 100 s (Fig. 4A). By triggering the FcRI A213H mutant, we observed a Wt-like phenotype (Fig. 4A). In contrast, the FcRI M210R mutant was severely hampered in calcium mobilization upon FcRI triggering (Fig. 4B). IIA1.6 cells endogenously express the BCR (surface IgG2a) (37). All FcRI transfectants expressed BCRs at similar levels (data not shown; n = 2). As shown in Fig. 4, C and D, all transfectants were capable of calcium mobilization upon BCR triggering.
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RI can also induce RAS/MAPK kinase/MAPK activation, eventually leading to activation of several FcRI functions (7, 13, 35, 38, 39), we next investigated MAPK phosphorylation upon FcRI cross-linking. The FcRI Wt (Fig. 5A) and the FcRI A213H (Fig. 5B) mutants induced MAPK phosphorylation at 5 min, which lasted until at least 20 min, whereas MAPK phosphorylation for the FcRI M210R (Fig. 5C) mutant was less prominent and faded quickly. BCR triggering induced MAPK phosphorylation, measured at 2 min.
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RI is IL-2 production (17). For all transfectants, IL-2 secretion was triggered by FcRI cross-linking. As shown in Fig. 6A (data shown in duplicate), FcRI Wt and FcRI A213H were capable of producing significant levels of IL-2. In contrast, the FcRI M210R mutant displayed a reduced capacity to produce IL-2 upon FcRI stimulation. No IL-2 release was measured using an isotype control Ab (data not shown). BCR triggering resulted in normal IL-2 production for all transfectants (Fig. 6B).
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RI M210R does not associate with FcR -chain
Because calcium mobilization, MAPK phosphorylation, and IL-2 production are dependent on interaction between FcRI and FcR -chain, we next tested this interaction in the FcRI mutants. Coimmunoprecipitations were performed for each cell line with FcRI specific-A59 Ab and mIgG1 as an isotype control. Coimmunoprecipitation of FcR -chain was comparable for FcRI Wt and FcRI A213H (Fig. 7). The FcRI M210R mutant, however, did not coimmunoprecipitate FcR -chain. No immunoprecipitation was detected using isotype control Ab. Besides loss of interaction in this stably transfected cell line, we confirmed the inability of the FcRI M210R mutant to bind the FcR -chain in a transient transfection system in HEK 293T cells (data not shown). FcRI Wt, however, was fully capable of FcR -chain association under these conditions. This suggests that the physical interaction between the FcRI M210R mutant and the FcR -chain is disrupted.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionDisclosuresReferences |
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R, the FcR forms a complex with an FcR -chain homodimer in myeloid cells (17, 40, 41). However, unlike FcR, the molecular basis of this interaction involves a positively charged arginine residue (R) at position 209 in the transmembrane domain of FcRI and a negatively charged aspartic acid (D) in the FcR -chain transmembrane domain (17). We studied the influence of the position of the positive charge in the transmembrane region of FcRI in two FcRI transmembrane mutants, thereby testing the spatial requirements for FcR -chain association. A vertical relocation of the positive charge in the -helical transmembrane of FcRI was realized in the FcRI A213H mutant. The FcRI M210R mutant represents a lateral transfer of the positive charge. These FcRI mutants were tested for FcR -chain-dependent and -independent functions and compared with the FcRI Wt.
Although it is difficult to exclude subtle conformational changes in the FcR after introducing point mutations in its transmembrane region, no indications of conformational changes were obtained after replacement of the arginine by a leucine (R209L), as shown previously (17). By substitution of the methionine, and alanine for a positively charged arginine (R) and histidine (H), respectively, we changed the amino acids to a minimal extent; in addition, the arginine and histidine were interchangeable without affecting FcRI functioning, as previously described (17). We can exclude major conformational changes of the -chain because we found FcRI surface expression (Fig. 2A), normal IgA binding ability of the FcRI mutants, and the capacity to internalize FcRI in both mutant receptors (Fig. 3).
In the present report, we found that the positive charge can be relocated within the transmembrane region of FcRI without losing FcR -chain-dependent functions, as shown for the FcRI A213H mutant. Lateral relocation, however, of the positive charge in the FcRI M210R mutant had a major impact on FcR -chain-dependent functionality. After lateral translocation, no FcR -chain association was found under mild lysis conditions (Fig. 7), resulting in the loss of signaling via the PI3K and Ras-ERK pathways. This was shown for calcium mobilization (Fig. 4), MAPK phosphorylation (Fig. 5), and IL-2 production (Fig. 6). Although FcRI transgenic mice are dependent on the FcR -chain for FcRI surface expression (9), a number of other studies showed FcRI surface expression not to be dependent on FcR -chain association (17, 19, 20), in line with our findings for the FcRI M210R mutant, which expressed FcRI at similar levels as FcRI Wt.
Because the crystal structure of FcRI has only been elucidated for the extracellular part of the receptor (42, 43), we propose a model to clarify the vertical and lateral relocations of the positive charge and its outcome on FcRI functioning. The transmembrane sequence was tested in different prediction programs, resulting in the same -helical wheel model (Fig. 8A) (44, 45). In this model, R209 and H213 in the FcRI A213H both face the FcR -chain, whereas M210R turns sideways (Fig. 8B).
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RI A213H support this model; i.e., this mutant receptor probably associates with FcR -chain in the same orientation as FcRI Wt, parallel to the original arginine to aspartic acid interaction. Relocation of the positive charge laterally in the FcRI M210R (Fig. 8A) results in transfer of the positive charge outside the interface of FcRI and FcR -chains, although still N-terminally and in close proximity with the original positive charge (Figs. 1 and 8B). This resulted in loss of FcR -chain-dependent functions due to an inability to assemble with the FcR -chain. Several factors may underlie these data. First, as recently described (18), not a single -chain, but dimerization of two -chains, is essential for FcRI assembly, resulting in a three-helical interface. Second, the cysteines that form the disulfide bond between the two FcR -chains may also contribute to the assembly of all three subunits. Third, recent observations (44) demonstrated that in addition to the aspartic acid at position 11 within the FcR -chain, a tyrosine at position 25 (Y25) and a cysteine at position 26 (C26) contribute to stabilization of the FcRI-FcR -chain complex. Which FcRI amino acids are involved in these interactions is unknown. However, by replacing the methionine at position 210 with an arginine, we cannot exclude the possibility of disrupting an unknown interaction between methionine and FcR -chain.
Taken together, the assembly of FcRI and FcR -chain is not exclusively based on the arginine to aspartic acid interaction. Several other residues play an essential role in the formation of the three-helical interface. Replacement of the positive charge outside this interface could result in disruption or inadequate formation of the FcRI-FcR -chain complex. Notably, the importance of the position of a positive charge for complex formation has also been described for TCR-CD3 assembly (46). The -chain of the TCR bears two positive residues on opposite sides, allowing association with both CD3
- and CD3-chains. Relocation of one of the positive charges abrogated association of the -chain with the CD3 heterodimer, which coincided with the lack of formation of the TCR 
complex.
From previous studies of FcRs, it is known that polar transmembrane residues are required for FcR -chain association for optimal receptor functioning, indicating that other residues can interact with the FcR -chain. For FcRI, the last 10 aa within the transmembrane region of FcRI, including the polar asparagine, are important for FcR -chain-dependent phagocytosis (41, 47). In FcRI and FcRIIIa, a negatively charged aspartic acid is present in the transmembrane region and mediates FcR -chain association and functioning (48, 49, 50). Replacement of the transmembrane region of the FcR -chain with the CD8 transmembrane region (32) abrogated phagocytosis, indicating that the transmembrane part is crucial for association.
In summary, this present study further defines the molecular basis for FcRI-FcR -chain association. Vertical positioning of the basic residue is found to be indispensable within the three-helical interface for functional assembly of the FcRI-FcR -chain dimer complex. This implies that multiple interactions contribute to stable FcRI-FcR -chain complexes.
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Acknowledgments |
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Disclosures |
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Footnotes |
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1 This work was supported by Dutch Cancer Foundation Grant UU 2002 2706 and Association for International Cancer Research Grant 03-119. 
2 Address correspondence and reprint requests to Dr. Jeanette H. W. Leusen, Department of Immunology, Immunotherapy Laboratory, University Medical Center Utrecht, Lundlaan 6, 3584 EA Utrecht, Room C-02.064.0, Utrecht, The Netherlands. E-mail address: j.h.w.leusen{at}lab.azu.nl
3 Abbreviations used in this paper: LRC, leukocyte receptor cluster; DAP, DNAX-associating protein; KAR, killer activatory receptors; Wt, wild type.
Received for publication November 4, 2005. Accepted for publication January 4, 2006.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionDisclosuresReferences |
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receptor in humans. J. Exp. Med. 171: 597-613. RI-positive liver Kupffer cells: reappraisal of the function of immunoglobulin A in immunity. Nat. Med. 6: 680-685. [Medline]RI, CD89). Immunol. Lett. 92: 23-31. [Medline]RI, CD89) function in transgenic mice requires both FcR chain and CR3 (CD11b/CD18). Blood 93: 4387-4394. -receptor I (CD89) recruits neutrophils as effector cells for CD20-directed antibody therapy. J. Immunol. 165: 5954-5961. RI (CD64) and FcRI (CD89). Cancer Res. 61: 4055-4060. R) with FcRI2 subunits in U937 cells: aggregation induces the tyrosine phosphorylation of 2. J. Immunol. 153: 3228-3236. [Abstract] chain: molecular basis for CD89/FcR chain association. J. Biol. Chem. 270: 29781-29787. association and protects against degradation of bound ligand. J. Biol. Chem. 274: 7216-7225. receptors (CD89) lacking chain association and mediate noninflammatory properties of secretory IgA. J. Leukocyte Biol. 69: 289-296. receptors mediate release of tumour necrosis factor- and interleukin-6 by human monocytes following receptor aggregation. Immunology 86: 1-5. [Medline] or phorbol ester stimulation. J. Leukocyte Biol. 63: 636-642. [Abstract] receptor cross-linking causes translocation of phosphatidylinositol-dependent protein kinase 1 and protein kinase B to MHC class II peptide-loading-like compartments. J. Immunol. 166: 5585-5593. -chain signaling. Blood 97: 205-213. RI as an inhibitory receptor that controls inflammation: dual role of FcR ITAM. Immunity 22: 31-42. [Medline]RI with IgA and its implications for ligand binding by immunoreceptors of the leukocyte receptor cluster. J. Immunol. 166: 1781-1789. RI and CD3
. J. Leukocyte Biol. 76: 1200-1206. receptor transmembrane domains: role in cell surface expression, chain interaction, and phagocytosis. Blood 101: 4479-4484. RIa--chain complexes trigger antibody-dependent cell-mediated cytotoxicity (ADCC) in CD5+ B cell/macrophage IIA1.6 cells. Clin. Exp. Immunol. 113: 415-422. [Medline]R (CD89) is mediated by a single serine residue (S263) in the intracellular domain of the receptor. Blood 97: 3478-3483. R-triggered Ca2+ signals: role in neutrophil NADPH oxidase activation. Biochem. Biophys. Res. Commun. 276: 749-755. [Medline]RI oxidant signaling. Blood 94: 2112-2120. 
B. Am. J. Respir. Cell Mol. Biol. 26: 315-332. RI) with the subunit of the IgE receptor. Proc. Natl. Acad. Sci. USA 90: 6023-6027. RI and its complex with IgA1-Fc. Nature 423: 614-620. [Medline]RI. J. Biol. Chem. 278: 27966-27970. chain residues at the interface of the cytoplasmic and transmembrane domains affect association with FcRI, surface expression, and function. J. Biol. Chem. 279: 26339-26345. in human T cells. J. Immunol. 156: 2155-2162. [Abstract]RI and the -chain is mediated solely via the 21 amino acid transmembrane domain of FcRI. Mol. Membr. Biol. 12: 309-312. [Medline]RIII (CD16) is mediated through the chain. J. Exp. Med. 175: 1381-1390. This article has been cited by other articles:
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  J. E. Bakema, A. Bakker, S. de Haij, H. Honing, M. Bracke, L. Koenderman, G. Vidarsson, J. G. J. van de Winkel, and J. H. W. Leusen Inside-Out Regulation of Fc{alpha}RI (CD89) Depends on PP2A J. Immunol., September 15, 2008; 181(6): 4080 - 4088. [Abstract] [Full Text] [PDF]
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M. A. Otten, J. H. W. Leusen, E. Rudolph, J. A. van der Linden, R. H. J. Beelen, J. G. J. van de Winkel, and M. van Egmond FcR {gamma}-Chain Dependent Signaling in Immature Neutrophils Is Mediated by Fc{alpha}RI, but Not by Fc{gamma}RI J. Immunol., September 1, 2007; 179(5): 2918 - 2924. [Abstract] [Full Text] [PDF]
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M. Dechant, T. Beyer, T. Schneider-Merck, W. Weisner, M. Peipp, J. G. J. van de Winkel, and T. Valerius Effector Mechanisms of Recombinant IgA Antibodies against Epidermal Growth Factor Receptor J. Immunol., September 1, 2007; 179(5): 2936 - 2943. [Abstract] [Full Text] [PDF]
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C. Nakahashi, S. Tahara-Hanaoka, N. Totsuka, Y. Okoshi, T. Takai, N. Ohkohchi, S.-i. Honda, K. Shibuya, and A. Shibuya Dual Assemblies of an Activating Immune Receptor, MAIR-II, with ITAM-Bearing Adapters DAP12 and FcR{gamma} Chain on Peritoneal Macrophages J. Immunol., January 15, 2007; 178(2): 765 - 770. [Abstract] [Full Text] [PDF]
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 B. D. Wines, H. M. Trist, P. A. Ramsland, and P. M. Hogarth A Common Site of the Fc Receptor {gamma} Subunit Interacts with the Unrelated Immunoreceptors Fc{alpha}RI and Fc{epsilon}RI J. Biol. Chem., June 23, 2006; 281(25): 17108 - 17113. [Abstract] [Full Text] [PDF]
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| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
). The vertical relocation of the positive charge (Fc
). Side chains of the amino acids R209, R210, and H213 are depicted.
, IL-2 production of Fc
, IL-2 production of Fc
, IL-2 production of Fc
www.site.uottawa.ca/
turcotte/resources/HelixWheel
). The N termini of the transmembrane regions start with a thick black line and end with a thin gray one (C-terminal end of the transmembrane regions). The association between the arginine (R) at position 209 in Fc