Receptor for the chemotactic and inflammatory peptide anaphylatoxin C3a. This receptor stimulates chemotaxis, granule enzyme release and superoxide anion production.
Combining with the C3a product of the complement cascade and transmitting the signal from one side of the membrane to the other to initiate a change in cell activity.
A cDNA clone encoding the human C3a anaphylatoxin receptor (C3aR) was isolated from a pcDNAI/Amp expression library prepared from U-937 cells which had been differentiated with dibutyryl cAMP to a macrophage-like phenotype. The cDNA clone contained an insert of 4.3 kbp and was able to confer to transfected human HEK-293 cells the capacity to bind specifically iodinated human C3a. Chinese hamster ovary cells co-transfected with this cDNA clone and a G-protein alpha subunit (G alpha-16) became functionally responsive to C3a and a C3a analog synthetic peptide, as measured by increased phosphoinositide hydrolysis. As inferred from the cDNA sequence, the clone encodes a 482-residue polypeptide with seven hydrophobic membrane-spanning helices and a high homology to the human C5a and formyl-Met-Leu-Phe receptors. Uniquely among the family of G-protein coupled receptors, the C3aR contains an exceptionally large second extracellular loop of approximately 175 residues. Northern hybridizations revealed an approximately 2.3-kb transcript as the major and an additional approximately 3.9 kb-transcript as a minor transcription product of the C3aR. The C3aR appears to be widely expressed in different lymphoid tissues, as shown by Northern hybridizations, providing evidence for a central role of the C3a anaphylatoxin in inflammatory processes.
Combining with an extracellular signal and transmitting the signal across the membrane by activating an associated G-protein; promotes the exchange of GDP for GTP on the alpha subunit of a heterotrimeric G-protein complex.
Evidence
1:
Inferred from Genetic InteractionUniProtKB
A cDNA was cloned from a rabbit spleen cDNA library which encoded a G-protein alpha subunit peptide of 374 amino acids, that at the peptide level exhibited 86% and 79% identity with human Galpha16 and mouse G(alpha)15, respectively. The rabbit G(alpha)subunit cDNA was subcloned into a mammalian expression vector and transiently co-transfected into HEK-293 cells along with cDNAs encoding the human C3a, C5a, or nociceptin/orphanin FQ receptors. In all three cases the rabbit G alpha subunit behaved similarly to G(alpha)15 or G(alpha)16 and effectively coupled the transfected receptors to intracellular calcium mobilization pathways. By nucleotide sequence homology and functional activity the rabbit G(alpha) subunit appears to be the ortholog of human G(alpha)16 and mouse G(alpha)15.
A cDNA clone encoding the human C3a anaphylatoxin receptor (C3aR) was isolated from a pcDNAI/Amp expression library prepared from U-937 cells which had been differentiated with dibutyryl cAMP to a macrophage-like phenotype. The cDNA clone contained an insert of 4.3 kbp and was able to confer to transfected human HEK-293 cells the capacity to bind specifically iodinated human C3a. Chinese hamster ovary cells co-transfected with this cDNA clone and a G-protein alpha subunit (G alpha-16) became functionally responsive to C3a and a C3a analog synthetic peptide, as measured by increased phosphoinositide hydrolysis. As inferred from the cDNA sequence, the clone encodes a 482-residue polypeptide with seven hydrophobic membrane-spanning helices and a high homology to the human C5a and formyl-Met-Leu-Phe receptors. Uniquely among the family of G-protein coupled receptors, the C3aR contains an exceptionally large second extracellular loop of approximately 175 residues. Northern hybridizations revealed an approximately 2.3-kb transcript as the major and an additional approximately 3.9 kb-transcript as a minor transcription product of the C3aR. The C3aR appears to be widely expressed in different lymphoid tissues, as shown by Northern hybridizations, providing evidence for a central role of the C3a anaphylatoxin in inflammatory processes.
A cDNA clone encoding the human C3a anaphylatoxin receptor (C3aR) was isolated from a pcDNAI/Amp expression library prepared from U-937 cells which had been differentiated with dibutyryl cAMP to a macrophage-like phenotype. The cDNA clone contained an insert of 4.3 kbp and was able to confer to transfected human HEK-293 cells the capacity to bind specifically iodinated human C3a. Chinese hamster ovary cells co-transfected with this cDNA clone and a G-protein alpha subunit (G alpha-16) became functionally responsive to C3a and a C3a analog synthetic peptide, as measured by increased phosphoinositide hydrolysis. As inferred from the cDNA sequence, the clone encodes a 482-residue polypeptide with seven hydrophobic membrane-spanning helices and a high homology to the human C5a and formyl-Met-Leu-Phe receptors. Uniquely among the family of G-protein coupled receptors, the C3aR contains an exceptionally large second extracellular loop of approximately 175 residues. Northern hybridizations revealed an approximately 2.3-kb transcript as the major and an additional approximately 3.9 kb-transcript as a minor transcription product of the C3aR. The C3aR appears to be widely expressed in different lymphoid tissues, as shown by Northern hybridizations, providing evidence for a central role of the C3a anaphylatoxin in inflammatory processes.
The directed movement of a motile cell or organism, or the directed growth of a cell guided by a specific chemical concentration gradient. Movement may be towards a higher concentration (positive chemotaxis) or towards a lower concentration (negative chemotaxis).
A cDNA was cloned from a rabbit spleen cDNA library which encoded a G-protein alpha subunit peptide of 374 amino acids, that at the peptide level exhibited 86% and 79% identity with human Galpha16 and mouse G(alpha)15, respectively. The rabbit G(alpha)subunit cDNA was subcloned into a mammalian expression vector and transiently co-transfected into HEK-293 cells along with cDNAs encoding the human C3a, C5a, or nociceptin/orphanin FQ receptors. In all three cases the rabbit G alpha subunit behaved similarly to G(alpha)15 or G(alpha)16 and effectively coupled the transfected receptors to intracellular calcium mobilization pathways. By nucleotide sequence homology and functional activity the rabbit G(alpha) subunit appears to be the ortholog of human G(alpha)16 and mouse G(alpha)15.
A series of molecular signals that proceeds with an activated receptor promoting the exchange of GDP for GTP on the alpha-subunit of an associated heterotrimeric G-protein complex. The GTP-bound activated alpha-G-protein then dissociates from the beta- and gamma-subunits to further transmit the signal within the cell. The pathway begins with receptor-ligand interaction, or for basal GPCR signaling the pathway begins with the receptor activating its G protein in the absence of an agonist, and ends with regulation of a downstream cellular process, e.g. transcription.
The Xenopus laevis oocyte has been widely utilized for cloning and functional expression of G-protein coupled receptors (GPCR). This system was used for the functional expression and characterization of the recently identified human C3a receptor. Complementary RNA from the human C3a receptor was transcribed in vitro and microinjected into Xenopus oocytes for functional characterization. A positive response to a synthetic C3a peptide agonist and to C3a, but not to platelet activating factor or fMetLeuPhe was detected. In addition, a response of approximately one third the amplitude obtained with C3a was obtained with rC5a. Conversely, oocytes co-injected with the C5a receptor and total RNA isolated from U937 cells responded to C5a as well as to C3a and the C3a synthetic peptide. A functional response with the anaphylatoxin C3a receptor in oocytes was dependent on co-injection of a pertussis toxin sensitive complementary human factor which could be supplied by co-injection of total RNA isolated from U937 cells. Oocytes expressing the anaphylatoxin C3a and C5a receptors responded to both agonists, in each case the response to the cognate ligand was substantially more robust than the response elicited by the other anaphylatoxin.
The immediate defensive reaction (by vertebrate tissue) to infection or injury caused by chemical or physical agents. The process is characterized by local vasodilation, extravasation of plasma into intercellular spaces and accumulation of white blood cells and macrophages.
A cDNA clone encoding the human C3a anaphylatoxin receptor (C3aR) was isolated from a pcDNAI/Amp expression library prepared from U-937 cells which had been differentiated with dibutyryl cAMP to a macrophage-like phenotype. The cDNA clone contained an insert of 4.3 kbp and was able to confer to transfected human HEK-293 cells the capacity to bind specifically iodinated human C3a. Chinese hamster ovary cells co-transfected with this cDNA clone and a G-protein alpha subunit (G alpha-16) became functionally responsive to C3a and a C3a analog synthetic peptide, as measured by increased phosphoinositide hydrolysis. As inferred from the cDNA sequence, the clone encodes a 482-residue polypeptide with seven hydrophobic membrane-spanning helices and a high homology to the human C5a and formyl-Met-Leu-Phe receptors. Uniquely among the family of G-protein coupled receptors, the C3aR contains an exceptionally large second extracellular loop of approximately 175 residues. Northern hybridizations revealed an approximately 2.3-kb transcript as the major and an additional approximately 3.9 kb-transcript as a minor transcription product of the C3aR. The C3aR appears to be widely expressed in different lymphoid tissues, as shown by Northern hybridizations, providing evidence for a central role of the C3a anaphylatoxin in inflammatory processes.
Any process that increases the rate, frequency or extent of macrophage chemotaxis. Macrophage chemotaxis is the movement of a macrophage in response to an external stimulus.
Any process that increases the frequency, rate, or extent of neutrophil chemotaxis. Neutrophil chemotaxis is the directed movement of a neutrophil cell, the most numerous polymorphonuclear leukocyte found in the blood, in response to an external stimulus, usually an infection or wounding.
Protein involved in the movement of a cell, or organism, along a concentration gradient of a chemotactic agent, such as a protein which causes, mediates or responds to chemotaxis. Chemotactic molecules such as sugars, peptides, cell metabolites, cell-wall or membrane lipids bind to cell surface receptors and trigger activation of intracellular signaling pathways, as well as remodeling of the cytoskeleton through the activation or inhibition of various actin-binding proteins.
Receptors which transduce extracellular signals across the cell membrane. At the external side they receive a ligand (a photon in case of opsins), and at the cytosolic side they activate a guanine nucleotide-binding (G) protein. These receptors are hydrophobic proteins that cross the membrane seven times.
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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