Investigating the role of ADAM10 as a receptor for streptococcal pneumolysin

Abstract

Streptococcus pneumoniae is a gram-positive extracellular opportunistic bacterium. S. pneumoniae mainly colonizes the human upper respiratory tract. Dissemination of this bacterium is a leading cause of a broad range of infections such as sepsis, otitis media, meningitis, and community-acquired pneumoniae. This bacterium produces pneumolysin (PLY), a cholesterol-dependent-cytotoxin. PLY mediates host cell death by binding to cholesterol in the plasma membrane and oligomerizing into cytolytic pores. PLY has been found to induce ADAM10-dependent E-cadherin cleavage, suggesting that the metalloprotease ADAM10 might be exploited as a receptor by PLY. Therefore, this study aims to investigate the role of ADAM-10 as a receptor for PLY. The surface expression of ADAM10 on multiple different epithelial and myeloid cell lines was measured. Lysis experiments with PLY were performed on these cell lines to study the sensitivity of cells in relation to their ADAM10 expression. Furthermore, the sensitivity of ADAM10-expressing rabbit erythrocytes and ADAM10-non-expressing human erythrocytes to PLY was compared. Lastly, ADAM10KO monoclonal cell lines were generated. Their sensitivity to PLY was measured and compared to the non-targeting control. ADAM10 surface expression did not correlate with cell sensitivity to PLY. Furthermore, rabbit and human erythrocytes demonstrated similar sensitivity to PLY. ADAM10KO cells did not demonstrate a physiologically relevant change in sensitivity to PLY. CONCLUSION: Our findings strongly indicate that ADAM10 is not utilized as a high-affinity proteinaceous receptor of PLY, as a lack of ADAM10 does not alter the cell sensitivty to PLY.