Membrane-Damaging Activity Against Various Phospholipid Liposomes by γ-hemolysin, Staphylococcal Two-Component Pore-Forming Cytolysin

摘要

References(44) Staphylococcal γ-hemolysin (Hlg) is a two-component cytolysin, which consists of LukF (Hlg1) and Hlg2. Our previous study has suggested that LukF and Hlg2 are alternatively arranged on the human erythrocyte membrane and form a ring-shaped heterooligomeric transmembrane pore with a functional diameter of approximately 2 nm. Quantitative image analyses using high-resolution transmission electron microscopy have revealed that LukF and Hlg2 tend to be arranged in several mismatch patterns. Several previous studies have reported that the LukF component has a binding pocket for phosphatidylcholine. In the present study, membranedamaging activities by Hlg were investigated by using carboxyfluoresceine (CF)-loading liposomes consisting of mammalian erythrocyte phospholipids or one kind of phospholipid. Our results revealed that Hlg shows membrane-damaging activities on horse, rabbit and human erythrocyte total phospholipid liposomes. Such activity was closely related to the ratio of phosphatidylcholine. Hlg showed membrane-damaging activity against phosphatidylcholine liposome by formation of ring-shaped pore complex and cluster. Besides, it was revealed that Hlg could target cardiolipin, which is not included in the mammalian erythrocyte membrane, but exists in the bacterial cytoplasmic membrane and in the inner mitochondrial membrane of mammal cell. The results suggest that Hlg has the potential to recognize several phospholipids in both erythrocyte and non-erythrocyte membranes and induce cytolysis not only of mammalian cells but also of bacterial cells by the formation of pores and clusters. These novel findings will contribute to the elucidation of mutual actions between cytotoxicity protein and phospholipids, and eventually lead to the development of a treatment for staphylococcal infection.