Molecular cloning of the cDNA encoding the Epstein-Barr virus/C3d receptor (complement receptor type 2) of human B lymphocytes.

Abstract

Complementary DNA clones for complement receptor type 2 (CR2), the B-lymphocyte membrane protein that serves as the receptor for Epstein-Barr virus and the C3d complement fragment, were obtained by screening a Xgtll library generated from Raji B lymphoblastoid cell mRNA. A 4.2-kilobase (kb) clone, representing the entire coding sequence of the protein plus untranslated 5' and 3' nucleotide sequences was obtained and sequenced. The 4.2-kb clone, which contains all but about 500 base pairs (bp) of the 5' untranslated region of the fufl-length CR2 mRNA, consists of 63 bp of 5' untranslated nucleotide sequence followed successively by a start codon, a 20-amino acid hydrophobic signal peptide, 1005 amino acids having a repeating motif, a 28-amino acid probable transmembrane domain, and a 34-amino acid cytoplasmic tail. The deduced amino acid sequence of the protein indicates that the extracellular domain consists entirely of 16 tandemly arranged repeating elements, each 60-75 amino acids in length, which are identified by multiple conserved residues. This repeating motif also occurs in the C3b/C4b receptor, several complement proteins, and a number of noncomplement proteins. In CR2, the 16 repeats occur in four clusters of four repeats each. Approximately 10% of the deduced amino acid sequence, including the amino and carboxyl termini, was conflirmed by amino acid sequencing of tryptic peptides derived from purified CR2. The nucleotide and derived amino acid sequence of CR2 and related studies are presented here.A Mr 145,000 B-lymphocyte membrane glycoprotein, designated complement receptor type 2 (CR2), serves as the receptor for Epstein-Barr virus (EBV) and the C3d and C3dg fragments of the third component of complement (1-5). An EBV viral envelope protein termed gp350/220 mediates the binding of EBV to CR2 (6, 7). Gp350/220 and C3d, the natural ligands, exhibit two regions of primary sequence similarity, a finding that suggests that common domains in these two proteins mediates binding to CR2. In addition to its role in permitting EBV infection, CR2 has been implicated in triggering B-cell activation (7-11); consistent with this finding, CR2 has been found to be phosphorylated upon treatment of B cells with phorbol myristate or anti-Ig (12).Previous studies have shown that the mature Mr 145,000 CR2 molecule consists of a Mr 111,000 polypeptide chain and multiple N-linked oligosaccharides (13). A previous study (14) reported the isolation of a partial CR2 cDNA clone and indicated that CR2 is highly similar to CR1, the C3b/C4b receptor; however, relatively limited nucleotide and protein sequence information was presented in that publication. The genes encoding both CR1 and CR2 have been mapped to human chromosome 1, band q32 (15).To further define the structural and functional properties of CR2, cDNA clones encoding CR2 were isolated, and the complete amino acid sequence of the protein* was deduced. Sequence analysis of tryptic peptides derived from purified CR2 allowed verification of the amino and carboxyl...

Activation of the EBV/C3d Receptor (CR2, CD21) on Human B Lymphocyte Surface Triggers Tyrosine Phosphorylation of the 95-kDa Nucleolin and Its Interaction with Phosphatidylinositol 3 Kinase

“…CR2 also interacts with autoantibodies present in serum of polyarthritis rheumatoid patients (13) and with CD23 (14). Molecular cloning indicated that CR2 is constituted by a large extracellular domain of 954 aa composed of 15-16 short consensus repeats, a 24-aa transmembrane domain, and a 34-aa intracellular domain (15,16). CR2 allows C3d and EBV to induce proliferation (17,18) or transformation (8), respectively.…”

CD19 Can Regulate B Lymphocyte Signal Transduction Independent of Complement Activation

“…CD21 is composed of an extracellular domain containing 15 or 16 repeating structural elements termed short consensus repeats (SCRs), a transmembrane region, and a 34-aa cytoplasmic domain (23,24). CD21 and CD35 (complement receptor 1) are alternative splice products of the same Cr2 gene in mice, but are encoded by different genes in humans (25,26).…”

Viral cell recognition and entry

“…Because delivery of the viral genome into the cell involves major rearrangements of the capsid structure, entry must be a tightly regulated process, which is triggered by the cell. The mechanism of entry can be, in the case of enveloped viruses, by fusion of the viral Paul et al, 1989;Choi et al, 1990Weis et al, 1988Fried et al, 1981Dalgleish et al, 1984Mendelsohn et al, 1989Greve et al, 1989Staunton et al, 1989;Tomassini et al, 1989Acharya et al, 1989Mason et al, 1993Moore et al, 1987Tanner et al, 1987 J.W. Kim et al, 1991;H.…”