An IgE-binding protein with a distinctive repetitive sequence and homology with an IgG receptor.

Abstract

Proteins that bind IgE play important roles in both the synthesis and function of IgE and are therefore intimately involved in IgE-mediated human allergic disorders. This report describes the structure of an IgE-binding protein, as predicted from sequencing a cDNA cloned from rat basophilic leukemia cells. This protein contains two domains: the amino-terminal domain (140 amino acids) consists of a highly conserved repetitive amino acid sequence, Tyr-Pro-GlyPro/Gln-Ala/Thr-Pro/Ala-Pro-Gly-Ala, whereas the carbox- The IgE receptor on mast cells and basophils has been most extensively studied. Metzger and coworkers (8) have proposed a tetrameric model for this receptor that includes a single highly glycosylated a subunit (Mr, 55,000), a single (3 subunit (Mr, 33,000), and two identical y subunits (Mr, 9000). Kulczycki and coworkers (9-11) have identified a protein of M, 31,000, in addition to the protein equivalent to the a subunit, in a two-cycle affinity purification of rat basophilic leukemia (RBL) cell lysates with IgE immunoadsorbents. A protein of similar properties was also found in rat mast cells (11, 12). Other investigators, using different procedures, have discovered Mr 30,000-33,000 IgE-binding proteins from RBL cells (13). Recently, we have identified a Mr 31,000 protein with affinity for IgE in oocytes injected with mRNA isolated from RBL cells (14) and in the in vitro translation products of RBL mRNA (15). It was shown that this protein exhibits an intrinsic and specific IgE-binding activity and is reactive with a specific rabbit antiserum prepared against highly purified RBL cell proteins isolated by affinity chromatography using IgE immunoadsorbent (9). It was also demonstrated that this IgE-binding protein is expressed specifically in certain cell types known to possess IgE-specific receptors. The cDNA coding for this protein was cloned and the partial amino acid sequence of this protein was determined through DNA sequencing of a partial cDNA (15).We report here the cloning and nucleotide sequence of a full-length cDNA revealing an IgE-binding protein (EBP) containing two distinct structural domains. One of the domains contains a highly conserved repetitive amino acid sequence and the other shares significant sequence homology with the receptor for the Fc portion of IgG (FcyR).t MATERIALS AND METHODSCell Lines and Reagents. The RBL cell line (16) was provided by H. Metzger of the National Institutes of Health. Mouse monoclonal IgE (H1-DNP-e-26.82) and IgG1 (Hi-DNP-y1-109.3) specific for 2,4-dinitrophenyl (DNP) have been described previously (17). Immunoadsorbents were prepared by conjugating 10 mg of protein to 1 g (dry weight) of CNBr-activated Sepharose 4B (Pharmacia).Preparation of RNA. Total cellular RNA was extracted from RBL cells by the guanidinium thiocyanate procedure (18). Isolation of poly(A)+ RNA by oligo(dT)-cellulose affinity chromatography and sucrose density gradient fractionation of the poly(A)+ RNA was performed as described (14).cDNA Cloning, Screening, and Sequencing. ...

Selective expression of an endogenous lactose-binding lectin gene in subsets of central and peripheral neurons

“…RL-14.5 also exhibits structural similarities with a larger (-30-35 kDa) lactose-binding lectin of mouse termed CBP-35 (Jia and Wang, 1988) and with a rat IgE binding protein (Albrandt et al, 1987), which is probably the rat homolog of CBP-35 (Fig. 2b).…”

Galectin‐3 is expressed in the notochord, developing bones, and skin of the postimplantation mouse embryo

“…Galectin-3 has been shown to localize to the surface of some cells, for example activated peritoneal macrophages (Sato and Hughes, 1994) (galectin-3 was originally known as the macrophage differentiation marker, Mac-2). Analysis of protein localisation in different cell lines has shown that despite the lack of signal sequence (Albrandt et al, 1987;Cherayil et al, 1989;Oda et al, 1991), galectin-3 is secreted through a pathway independent of the endoplasmic reticulum-Golgi complex Sato et al, 1993). Interestingly, it has also been proposed that distribution of galectin-3 might be regulated by its state of phosphorylation (Huflejt et al, 1993).…”

Visualization of Galectin-3 Oligomerization on the Surface of Neutrophils and Endothelial Cells Using Fluorescence Resonance Energy Transfer

“…Interestingly, galectin-3 does not comprise two CRDs nor does it form dimers in solution (20,21). Rather, galectin-3 is composed of a N-terminal, non-lectin domain consisting of multiple repeats of a peptide sequence rich in proline, glycine, and tyrosine in addition to its C-terminal CRD (22)(23)(24). Others and our previous study have underlined the importance of the two domains of galectin-3 for its biological functions through the demonstration that both the C-terminal CRD domain and the N-terminal non-lectin domain are essential for its role in signal transduction, cellular adhesion, and lattice formation (Refs.…”