The major surface protein complex of Treponema denticola depolarizes and induces ion channels in HeLa cell membranes

Abstract

The oral spirochete Treponema denticola is closely associated with periodontal diseases in humans. The 53-kDa major surface protein (Msp) located in the outer membrane of T. denticola serovar a (ATCC 35405) has both pore-forming activity and adhesin activity. We have used standard patch clamp recording methods to study the effects of a partially purified outer membrane complex containing Msp on HeLa cells. The Msp complex was free of the chymotrypsin-like proteinase also found in the outer membrane of T. denticola. Msp bound to several HeLa cell proteins, including a 65-kDa surface protein and a 96-kDa cytoplasmic protein. The Msp complex depolarized and increased the conductance of the HeLa cell membrane in a manner which was not strongly selective for Na ؉ , K ؉ , Ca 2؉ , and Cl ؊ ions. Cell-attached patches of HeLa cell membrane exposed to Msp complex exhibited short-lived channels with a slope conductance of 0.4 nS in physiologically normal saline. These studies show that Msp binds both a putative epithelial cell surface receptor and cytoplasmic proteins and that the Msp complex can form large conductance ion channels in the cytoplasmic membrane of epithelial cells. These properties may contribute to the cytopathic effects of T. denticola on host epithelial cells.

Outer sheath associated proteins of the oral spirochete Treponema maltophilum

“…The electron micrographs clearly indicate that MspA is a major protein of the outer sheath, supporting our previous results from subcellular fractionation, SDS-PAGE analysis and deter-gent treatment of the outer membrane [8]. The T. denticola Msp protein was shown to be an outer membrane porin, with binding properties to host cell surface proteins [4,5,12]. Further it was reported that the Msp protein forms a hexagonal array in the outer sheath [4], however, this could not be con¢rmed by a recent publication [2].…”

Mutagenesis of outer membrane virulence determinants of the oral spirochete Treponema denticola

“…Like most bacterial outer membrane porins, Msp was relatively resistant to proteolytic degradation. This resistance to endogenous proteases was employed in a recent study as a means of puri¢cation of Msp from crude outer membrane extracts [6]. Msp may play a role in presentation of CTLP on the cell surface, thus protecting the cell from its degradative e¡ects.…”

“…Two prominent surface antigens of T. denticola ATCC 35405, the poreforming major surface protein (Msp) and the chymotrypsin-like protease (CTLP), adhered to and were cytotoxic to epithelial cells [5]. Msp induced pore formation in HeLa cell membranes [6]. CTLP activ-ity was required for T. denticola migration through a basement membrane model [7].…”

New insights into the emerging role of oral spirochaetes in periodontal disease

“…Msp is part of an outer sheath complex in T. denticola; it has both adhesin and porin properties [67,70,71]. Msp is also found in T. vincentii, but not in other oral spirochaetes [72,73].…”