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

Torsten Crass, Ute Raffetseder, Ulrich Martin, Melanie Grove, Andreas Klos, Jörg Köhl, Wilfried Bautsch*

*Corresponding author for this work
    143 Citations (Scopus)


    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 (Gα-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 ~ 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.

    Original languageEnglish
    JournalEuropean Journal of Immunology
    Issue number8
    Pages (from-to)1944-1950
    Number of pages7
    Publication statusPublished - 01.08.1996


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