Calcium- and Mucin-Binding Proteins of Staphylococci

Abstract

The association of staphylococci with the mucus gel that overlays the mucosa of the respiratory tract may lead to clearance of cocci or, in certain conditions such as cystic fibrosis (CF), to colonization. In the present study, a quantitative radioassay was used to study the effect of Ca2+, which is elevated in CF sputa, on the adhesion of 3H-labelled Staphylococcus aureus to submaxillary gland much immobilized in MaxiSorp 96-well, break-apart modules. Ca2+ significantly enhanced the adhesion of S. aureus (five strains) and Staphylococcus epidermidis (four strains). The reaction was specific because adhesion was not enhanced in the presence of Mg2+, Ca2+ + EGTA (a Ca" chelator) or protamine and was not attributable to hydrophobicity of the test strains. Staphylococcal adhesion was significantly (P d 0.005) blocked in the presence of highly sialated and sulphated reagents, which suggests that Ca" binds to the sialic acid and sulphate residues of immobilized mucin. The Ca2+-binding sites on the surface of S. aureus were trypsin-sensitive ; in addition, 12%labelled solubilized S. aureus surface proteins reacted with immobilized mucin in a direct binding assay, and the reaction was significantly enhanced by Ca2+. Autoradiography demonstrated that 45Ca bound directly to two polypeptides (M, 170000 and 150000) of solubilized staphylococcal surface proteins separated by SDS-PAGE, and that '251-labelled mucin bound directly to three staphylococcal polypeptides (M, 40000,35000, and 29000). These results suggest that S. aureus adhesion to mucin is mediated by at least two mechanisms: via Ca2+-binding surface proteins in the presence of Ca2+ and via mucin-binding surface proteins unrelated to Ca2+.

Localization ofStaphylococcus aureusin Infected Airways of Patients with Cystic Fibrosis and in a Cell Culture Model ofS. aureusAdherence

“…aureus is provided with a variety of membrane-bound molecules which may act as adhesins for different surface structures. In general, the nature of these adhesins is thought to be protein because treatment of S. aureus with proteinases significantly reduces adherence (14,17,19,20). Receptors for such adhesins on epithelial surfaces include membrane bound glycolipids (13,15); connective tissue glycoproteins, such as fibronectin (30); collagens (31); laminin (32); vitronectin (33); and proteoglycans, such as heparansulfate (14).…”

“…For example, in vitro , primary epithelial cells may degenerate after short periods of time, ciliated respiratory epithelial cells may rapidly lose their cilia, and most cell lines do not produce mucus. Particularly, mucus production is essential for an investigation of S. aureus adherence to the CF respiratory epithelium, since mucin binding of S. aureus has been demonstrated in animals (18) and in vitro (18)(19)(20), secreted mucins are oversulfated in CF (10,11,21), and inflammatory mechanisms in CF airways (22) provoke a pronounced mucus hypersecretion (23).…”

Expression of HCLCA1 in cystic fibrosis lungs is associated with mucus overproduction

“…Previous reports have shown that neutrophil elastase is a potent mucus secretagogue [1,2] and that lipopolysaccharide from Pseudomonas aeruginosa can directly induce upregulation of the mucin gene MUC2 [3,4]. Conversely, bacteria such as Staphylococcus aureus [5] and P. aeruginosa [6] are able to bind to mucins. Therefore, mucus overproduction and bacterial infection can support each other.…”

Scanning Electron Microscopy and Energy Dispersive X-Ray Microanalysis ofPerna canaliculusMussel Larvae Adhesive Secretion

“…Negatively charged molecules are present on the bacterial cell surface, and Ca 2þ decreases the electrostatic repulsion to negatively charged substrates during the initial stage of adhesion [42]. Moreover, a Ca 2þ -dependent attachment on solid surfaces is displayed in a variety of bacteria, such as in the case of Rhizobium leguminosarum [43] and Staphylococcus aureus [44], where, in the absence of this cation, the bacterial adhesion was observed to be fully prevented. The other elements detected by EDX microanalysis, S and P, can be found incorporated in the adhesive both in certain amino acids and as phosphorylated=sulfated functionalities in polysaccharides.…”