Molecular cloning of a novel hyaluronan receptor that mediates tumor cell motility

A cDNA encoding a unique hyaluronan receptor has been molecularly cloned from a lambda GT11 3T3 cDNA expression library. Immunoblot analyses of cell lysates, using antibodies to peptides encoded in the cDNA, specifically react with a 58-kD protein. This protein is regulated by the mutant H-ras gene in cells containing a metallothionein promoter H-ras hybrid gene. Further, antibodies to peptide sequences encoded in the cDNA block the increase in locomotion resulting from induction of the mutant H-ras gene in this cell line. In a transblot assay, the bacterially expressed protein binds to biotinylated hyaluronan. Antibodies to peptides encoded in the cDNA react in immunoblot assays with the 58- and 52-kD proteins of a novel hyaluronan receptor complex previously implicated in cell locomotion. Furthermore, antibodies specific to the 58- and 52-kD proteins, which block ras-induced locomotion, also cross-react with the expressed, encoded protein. The gene product described here appears to be a new type of hyaluronan receptor that is involved in cell locomotion. It is named RHAMM, an acronym for receptor for hyaluronan-mediated motility.

Structural studies on bovine spleen heme oxygenase. Immunological and structural diversity among mammalian heme oxygenase enzymes

Heme oxygenase is an Mr 32,000 microsomal enzyme which catalyzes the rate-limiting step in the oxidative catabolism of heme to yield equimolar quantities of biliverdin IX alpha, carbon monoxide, and iron. In the present investigation, evidence is presented suggesting that immunochemical and structural differences exist between bovine spleen heme oxygenase and heme oxygenase enzymes from other mammalian species. Using an antibody directed against bovine spleen heme oxygenase, enzyme-linked immunosorbent assays, Western blotting experiments, and cell-free translation immunoprecipitation studies showed that bovine spleen heme oxygenase is only weakly immunochemically related to heme oxygenase from rat spleen. This observation was supported by the fact that a rat spleen heme oxygenase cDNA probe did not hybridize significantly to bovine spleen heme oxygenase mRNA in Northern analyses nor to restriction fragments containing the bovine heme oxygenase gene in Southern analyses. Tryptic peptides were prepared from bovine spleen heme oxygenase and the amino acid sequences of nine peptides comprising 94 amino acid residues were determined, providing the first information on the primary structure of bovine spleen heme oxygenase. Comparison of the sequences of these tryptic peptides with regions of the deduced amino acid sequences of rat spleen and human macrophage heme oxygenase revealed sequence similarities ranging from 55 to 100%. Several peptides displaying the highest degree of sequence similarity were found to occur in regions of the heme oxygenase molecule postulated to contain the heme binding site, indicating that despite the immunochemical and apparent structural differences between bovine spleen heme oxygenase and the rat and human enzymes, functionally important amino acid residues have been conserved in the evolution of mammalian heme oxygenase genes.

Abrogation of the antibenzylpenicilloyl (BPO) IgE response with BPO-polyvinyl alcohol conjugates

IgE antibodies to the benzylpenicilloyl (BPO) determinant and ovalbumin (OA) were readily induced B⁶D²F¹ mice by a single i.p. injection of 10 µg of BPO⁴-OA suspended with 1 mg AI(OH)³ in 0.5 ml of saline. The potential of these mice to mount a <i>de novo</i> anti-BPO IgE antibody response was specifically abrogated by pretreatment of mice with tolerogenic conjugates consisting of the hapten coupled to the hydrophilic and nonimmunogenic polymers, polyvinyl alcohols (PVA), with average molecular weigths of 10,000 or 14,000 daltons. The average epitope density of these conjugates varied from 1.1 to 3.9. It is noteworthy that even BPO^1.1-PVA, which elicied only weak PCA reactions in rats sensitized i.d. with mouse anti-BPO reaginic antibodies, was highly tolerogenic. More importantly, the ongoing anti-BPO reaginic response in sensitized mice was also readily suppressed by administration of these tolerogenic conjugates, e.g. a single dose of 100 µg of BPO^2.7-PVA was sufficient to abolish an ongoing anti-BPO IgE response. Moreover, administration of these tolerogenic conjugates into mice sensitized to BPO⁴-OA, prior to their resensitization in presence of <i>Bordetella pertussis,</i> protected these animals from anaphylactic death on i.v. challenge with 2 mg of the polyvalent BPO⁹-MγG conjugate (MγG = mosue γ-globulins); by contrast, all control mice which had not received this tolerogenic regimen died of anaphylaxis. It is suggested that conjugates of PVA with haptenic antibiotic or other drug molecules may prove to be effective therapeutic agents for the specific suppression of IgE antibodies mediating allergies of the immediate type to a wide spectrum of low molecular weight allergenic compounds.