title: Expression cloning of the human C3a anaphylatoxin receptor (C3aR) from differentiated U-937 cells.
abstract: 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.
authors.affiliation: Institute of Medical Microbiology, Hannover Medical School, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Crass
authors.forename: U
authors.initials: U
authors.lastname: Raffetseder
authors.forename: U
authors.initials: U
authors.lastname: Martin
authors.forename: M
authors.initials: M
authors.lastname: Grove
authors.forename: A
authors.initials: A
authors.lastname: Klos
authors.forename: J
authors.initials: J
authors.lastname: Köhl
authors.forename: W
authors.initials: W
authors.lastname: Bautsch
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D002454:Cell Differentiation / Q000276:immunology; D002460:Cell Line; D003001:Cloning, Molecular; D015926:Complement C3a / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D009000:Monocytes / Q000166:cytology / Q000378:metabolism; D011485:Protein Binding / Q000276:immunology; D011951:Receptors, Complement / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology; D017422:Sequence Analysis, DNA
chemical_list: D008565:Membrane Proteins; D011951:Receptors, Complement; C085567:complement C3a receptor; D015926:Complement C3a