Inhibition of bovine gingival laminin receptor by bacterial lipopolysaccharide

A laminin receptor was isolated from bovine gingival epithelial-cell membrane. After solubilization with octylglucoside, the receptor was subjected to affinity chromatography on laminin-coupled Sepharose and eluted with cation-free EDTA buffer yielding on SDS-PAGE a 67 kDa protein band. After radioiodination, the protein was incorporated into liposomes which displayed specific affinity towards laminin-coated surfaces, as well as to tooth cementum. The binding of receptor protein to cementum was inhibited by lipopolysaccharide from Bacteroides gingivalis. Preincubation of cementum with the lipopolysaccharide decreased the binding of the liposomal laminin-receptor preparation by 35.8%, while a 59.2% decrease in binding occurred when the lipopolysaccharide was preincubated with the receptor, suggesting that the lipopolysaccharide interfered with the laminin binding site on the receptor. The results demonstrate the existence of a specific gingival cell-surface laminin receptor, show that it is capable of binding to cementum, and provide evidence for the disruption of this process by bacterial lipopolysaccharide. This mechanism may account for the loss of gingival attachment in the pathogenesis of periodontal disease.