Hyaluronic acid-receptor binding demonstrated by synthetic adhesive proteoglycan peptide constructs and by cell receptors on the marine sponge Microciona prolifera.

Abstract

The aggregation factor (MAF) of Microciona sponge is depicted as a species specific, adhesive proteoglycan molecule configured as a sunburst-type structure with a central ring, or core, from which numerous elongated arms project (1). Although the carbohydrate content of MAF is very high, the core is considered to be a protein (2). Fernandez-Busquets et al. have demonstrated, in a cloned peptide MAF fragment, a putative hyaluronic acid (HA) binding sequence bearing a chemical similarity to some other HA binding proteins on vertebrate cell membranes (3, 4) that are known to be involved in growth, and cell cycle and motility events (5, 6). The sequence of predominantly basic amino acids is generally designated by the formula B (X7) B, where B is arginine or lysine, and X is any non-acidic amino acid; there is also at least one additional basic amino acid within, or adjacent to, the basic unit (7, 8). By these criteria, the deduced MAF peptide sequence is shown to be B (X6) B, and is thus analogous to its vertebrate counterparts. In an earlier study, we used a biotin-labeled HA (BHA) probe to demonstrate HA receptors on Microciona cells; we also used antibodies against RHAMM (receptor for HA mediated motility, having the chemical formula shown above) to demonstrate that RHAMM is present on some of these cells (9). These results led us to hypothesize that HA, known to be present on MAF, might serve as a ligand for these chemically similar binding peptides, one on the MAF core peptide, the other on cell membranes, and that it might, thereby, be capable of signal transduction, as is known to occur in higher organisms. The aim of this study was to provide evidence in support of these notions.