THE MAJOR SURFACE PROTEIN COMPLEX OF TREPONEMA-DENTICOLA DEPOLARIZES AND INDUCES ION CHANNELS IN HELA-CELL MEMBRANES

The oral spirochete Treponema denticola is closely associated with per iodontal diseases in humans. The 53-kDa major surface protein (Msp) lo cated in the outer membrane of T. denticola serovar a (ATCC 35405) has both pore-forming activity and adhesin activity. We have used standar d patch clamp recording methods to study the effects of a partially pu rified outer membrane complex containing Msp on HeLa sells. The Msp co mplex was free of the chymotrypsin-like proteinase also found in the o uter, membrane of T. denticola. Msp bound to several HeLa cell protein s, including a 65-kDa surface protein and a 96-kDa cytoplasmic protein . The Msp complex depolarized and increased the conductance of the HeL a cell membrane in a manner which was not strongly selective for Na+, K+, Ca2+, and Cl- ions. Cell-attached patches of Hela cell membrane ex posed to Msp complex exhibited short-lived channels with a slope condu ctance of 0.4 nS in physiologically normal saline. These studies show that Msp binds both a putative epithelial cell surface receptor and cy toplasmic proteins and that the Msp complex can form large conductance ion channels in the cytoplasmic membrane of epithelial cells. These p roperties may contribute to the cytopathic effects of T. denticola on host epithelial cells.