Molecular Cloning of Human Fibroblast Hyaluronic Acid-binding Protein Confirms Its Identity with P-32, a Protein Co-purified with Splicing Factor SF2

Abstract

The purification of a 68-kDa hyaluronic acid-binding protein (HA-binding protein), a homodimer of 34 kDa that binds specifically to hyaluronic acid, has been reported earlier by us (Gupta, S., Batchu, R.B., and Datta, K. (1991) Eur. J. Cell Biol. 56, 58-67). Here, we report the isolation of a partial cDNA clone from a lambda gt11 cDNA expression library of human skin fibroblast by immuno-screening with HA-binding protein antiserum. The internal polypeptide sequence (83 residues) of the purified hyaluronic acid-binding protein is identical to the predicted protein sequence derived from hyaluronic acid-binding protein cDNA, suggesting the authenticity of the clone. Interestingly, this hyaluronic acid-binding protein cDNA sequence has complete homology with the cDNA sequence of a protein P-32, co-purified with the human pre-mRNA splicing factor SF2 (Krainer, A.R., Mayeda, A., Kozak, D., and Binns, G. (1991) Cell 66, 383-394). Furthermore, the data on the N-terminal sequence of hyaluronic acid-binding protein and the predicted polypeptide of P-32 revealed the identical coding sequence of 209 amino acids for both the proteins. As the identity and functional characterization of P-32 have not yet been reported, P-32 cDNA was expressed in Escherichia coli, and the recombinant P-32 protein was purified by hyaluronic acid-Sepharose affinity chromatography. The recombinant P-32 protein showed immunocross-reactivity with the polyclonal antibodies raised against HA-binding protein. The predicted amino acid sequence of the protein fulfilled the minimal criteria for binding to hyaluronic acid, i.e. two basic amino acids flanking a seven-amino acid stretch, as reported for other hyaluronic acid affinity of the recombinant P-32 protein was confirmed by biotinylated hyaluronic acid binding assay. The binding of recombinant P-32 protein to biotinylated hyaluronic acid binding assay. The binding of recombinant P-32 protein to biotinylated hyaluronic acid can be competed only with excess unlabeled hyaluronic acid, confirming its specificity toward hyaluronic acid. All these results suggest that both P-32, co-purified with the human pre-mRNA splicing factor SF2, and 34-kDa hyaluronic acid-binding protein reported by us are the same protein and that it is a new member of the hyaluronic acid-binding protein family, the "hyaladherins."

Platelet power: sticky problems for sticky parasites?

“…Equally weighty issues concern the affinity and avidity of such interactions and whether binding occurs in the presence or absence of the native ligands for these receptors. This is particularly interesting for gC1qR/HABP1/p32 that binds the globular head domains of C1q and hyaluronic acid [8,14]. Do these host ligands share overlapping binding sites on gC1qR/HABP1/p32 with the parasite molecules expressed on the infected erythrocytes?…”

Receptor for the globular heads of C1q (gC1q‐R, p33, hyaluronan‐binding protein) is preferentially expressed by adenocarcinoma cells

“…44,45 gC1q-R/p33 is expressed by a variety of cell types, including B cells, monocytes, macrophages, neutrophils, eosinophils, fibroblasts, platelets, endothelial cells and smooth muscle cells, as well as by the breast cancer cell lines MCF7 and SKBr3. 31 In addition to binding C1q itself, 46 gC1q-R is a multifunctional receptor capable of binding a variety of plasma proteins, including thrombin, 47 fibrinogen 35 and vitronectin, 37 as well as both bacterial 38,40 and viral 48 -51 proteins.…”

Hyaluronic acid induced hyaluronic acid binding protein phosphorylation and inositol triphosphate formation in lymphocytes

“…This cell surface protein was further shown to be involved in macrophage histiocytoma activation (7). Recently, the predicted amino acid sequence derived from eDNA sequence revealed the specific hyaluronic acid binding motif in this protein (8). The presence of two plasma membrane proteins of 37 kDa and 41 kDa, showing specific binding to this HA-binding protein have been demonstrated (9).…”