Molecular Cloning and Characterization of the Human Anaphylatoxin C3a Receptor

doi:10.1074/jbc.271.34.20231

Molecular Cloning and Characterization of the Human Anaphylatoxin C3a Receptor*

From the Departments of ^‡ Molecular Immunology,
** Molecular Genetics,
^‴ Biomolecular Discovery, and
^∥ Pulmonary Pharmacology, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406-0939 and
^¶ Human Genome Sciences, Rockville, Maryland 20850-3338

^§ To whom correspondence should be addressed:
Dept. of Molecular Immunology UE0548, SmithKline Beecham Pharmaceuticals, 709 Swedeland Rd., P. O. Box 1539, King of Prussia, PA 19406-0939.
Tel.: 610-270-7602; Fax: 610-270-5093.

Abstract

In a human neutrophil cDNA library, an orphan G-protein-coupled receptor, HNFAG09, with 37% nucleotide identity to the C5a receptor (C5a-R, CD88) was identified. A novel feature of this gene, unlike C5a-R and other G-protein-coupled receptors, is the presence of an extraordinarily large predicted extracellular loop comprised of in excess of 160 amino acid residues between transmembrane domains 4 and 5. Northern blot analysis revealed that expression of mRNA for this receptor in human tissues, while similar, was distinct from C5a-R expression. Although there were differences in expression, transcripts for both receptors were detected in tissues throughout the body and the central nervous system. Mammalian cells stably expressing HNFAG09 specifically bound ¹²⁵I-C3a and responded to a C3a carboxyl-terminal analogue synthetic peptide and to human C3a but not to rC5a with a robust calcium mobilization response. HNFAG09 encodes the human anaphylatoxin C3a receptor.

Footnotes

↵* The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact
↵¹ The abbreviations used are:

PCR

polymerase chain reaction

kb

kilobase

PBL

peripheral blood leukocytes.
↵² R. S. Ames, P. Nuthulaganti, and C. Kumar, unpublished observation.
- Received June 18, 1996.
- Revision received June 26, 1996.