The chimpanzee and cynomolgus monkey erythrocyte immune adherence receptors are encoded by CR1-like genes.
The human erythrocyte immune adherence (IA) receptor is the Mr 220,000 type one complement receptor, or CR1. Nonhuman primate IA receptors are comprised of a family of smaller erythrocyte complement receptors (E-CRs) of unknown origin. Recently, the Mr 65,000 baboon E-CR was identified as a glycophosphatidylinositol (GPI)-linked protein encoded by a partially duplicated CR1 gene termed CR1-like. The purpose of this study was to determine the genetic origin of the Mr 75,000 chimpanzee E-CR. Two previously identified cDNAs, an alternative splice product of CR1 termed CR1a and a chimpanzee form of CR1-like, were synthesized and amplified from chimpanzee bone marrow RNA, and transiently expressed in COS-7 cells. By SDS-PAGE, the CR1a protein had a relative mobility slightly greater than chimpanzee E-CR, whereas that of the CR1-like protein was slightly less. Affinity chromatography demonstrated that little chimpanzee CR1a bound to human C3i linked to activated thiol-Sepharose (C3i-ATS), while over 50% of both chimpanzee CR1-like and chimpanzee E-CR bound to C3i-ATS. Treatment with phosphatidylinositol-specific phospholipase C (PIPLC) to assess GPI linkage released E-CR from chimpanzee erythrocytes, and E-CR from cynomolgus monkey erythrocytes. Based on size, ligand-binding specificity, and PIPLC sensitivity, we conclude that the chimpanzee E-CR is encoded by the CR1-like gene. Furthermore, based on PIPLC sensitivity, the cynomolgus monkey E-CR is also likely encoded by a CR1-like sequence. Thus, CR1-like, which is a genetic element of unknown significance in humans, is the gene that encodes the erythrocyte IA receptor of many nonhuman primates.
Chen
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The Department of Internal Medicine, The Ohio State University, Columbus 43210, USA.
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Shen
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Birmingham
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D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004912:Erythrocytes / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D016023:Integrins / Q000235:genetics*; D008252:Macaca fascicularis / Q000235:genetics*; D008969:Molecular Sequence Data; D002679:Pan troglodytes / Q000235:genetics*; D016133:Polymerase Chain Reaction / Q000379:methods; D011951:Receptors, Complement; D017463:Receptors, Complement 3b / Q000235:genetics*
D016023:Integrins; D011951:Receptors, Complement; D017463:Receptors, Complement 3b; C075060:erythrocyte immune adherence receptor