Expression cloning of the human C3a anaphylatoxin receptor (C3aR) from differentiated U-937 cells

Eur J Immunol. 1996 Aug;26(8):1944-50. doi: 10.1002/eji.1830260840.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Blotting, Northern
  • Cell Differentiation / immunology
  • Cell Line
  • Cloning, Molecular*
  • Complement C3a / metabolism*
  • Complement C3a / physiology
  • Humans
  • Membrane Proteins*
  • Molecular Sequence Data
  • Monocytes / cytology
  • Monocytes / metabolism
  • Protein Binding / immunology
  • Receptors, Complement / genetics*
  • Receptors, Complement / isolation & purification
  • Receptors, Complement / physiology
  • Sequence Analysis, DNA


  • Membrane Proteins
  • Receptors, Complement
  • complement C3a receptor
  • Complement C3a

Associated data

  • GENBANK/Z73157