Salivary receptors for GalNAcβ-sensitive adherence of Actinomyces spp.: Evidence for heterogeneous GalNAcβ and proline-rich protein receptor properties

Abstract

The receptors for GalNAcβ1-3GalαOethyl (GalNAcβ)-sensitive adherence of Actinomyces strains to salivary pellicles were investigated. Parotid and submaxillary saliva from one individual was size fractionated and utilized in hydroxyapatite adherence assays with Actinomyces naeslundii 12104 and A. viscosus 19246 and LY7 with and without GalNAcβ. Three parotid salivary fractions, the high-molecular-weight, acidic proline-rich protein (PRP), and statherin fractions, promote GalNAcβ-sensitive adherence of strain 12104, whereas only the high-molecular-weight fraction of submaxillary saliva promotes such adherence. In contrast, strain LY7, possessing a variant GalNAcβ specificity, shows GalNAcβ-sensitive adherence to the leading and trailing regions of the submaxillary PRP fractions but less distinct adherence to the parotid and submaxillary high-molecular-weight fractions. In addition, the PRP and statherin fractions promote adherence of strains LY7 and 19246 that is not inhibited by GalNAcβ. However, whereas strain LY7 binds more strongly to the PRP fraction than to the statherin fraction, strain 19246 binds preferentially to the statherin fractions of parotid and submaxillary saliva. These salivary protein fractions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunostained to detect glycosylated proteins. The different salivary receptor properties are paralleled by different glycosylation patterns. The variable GalNAcβ specificities may have evolved to match different salivary glycosylation patterns, and PRP and statherin binding properties seem to be heterogeneous among the Actinomyces strains.