Open AccessAggregatibacter actinomycetemcomitans leukotoxin cytotoxicity occurs through bilayer destabilization
Author(s) -
Brown Angela C.,
BoeszeBattaglia Kathleen,
Du Yurong,
Stefano Frank P.,
Kieba Irene R.,
Epand Raquel F.,
Kakalis Lazaros,
Yeagle Philip L.,
Epand Richard M.,
Lally Edward T.
Publication year - 2012
Publication title -
cellular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.542
H-Index - 138
eISSN - 1462-5822
pISSN - 1462-5814
DOI - 10.1111/j.1462-5822.2012.01762.x
Subject(s) - bilayer , liposome , biophysics , lipid bilayer , biology , aggregatibacter actinomycetemcomitans , cytotoxicity , membrane , cell membrane , microbiology and biotechnology , biochemistry , in vitro , bacteria , genetics , porphyromonas gingivalis
Summary The Gram‐negative bacterium, Aggregatibacter actinomycetemcomitans , is a common inhabitant of the human upper aerodigestive tract. The organism produces an RTX (Repeats in ToXin) toxin (LtxA) that kills human white blood cells. LtxA is believed to be a membrane‐damaging toxin, but details of the cell surface interaction for this and several other RTX toxins have yet to be elucidated. Initial morphological studies suggested that LtxA was bending the target cell membrane. Because the ability of a membrane to bend is a function of its lipid composition, we assessed the proficiency of LtxA to release of a fluorescent dye from a panel of liposomes composed of various lipids. Liposomes composed of lipids that form nonlamellar phases were susceptible to LtxA‐induced damage while liposomes composed of lipids that do not form non‐bilayer structures were not. Differential scanning calorimetry demonstrated that the toxin decreased the temperature at which the lipid transitions from a bilayer to a nonlamellar phase, while 31 P nuclear magnetic resonance studies showed that the LtxA‐induced transition from a bilayer to an inverted hexagonal phase occurs through the formation of an isotropic intermediate phase. These results indicate that LtxA cytotoxicity occurs through a process of membrane destabilization.