Internalization ofClostridium perfringensα-toxin leads to ERK activation and is involved on its cytotoxic effect

Abstract

Clostridium perfringens phospholipase C (CpPLC), also called α-toxin, plays a key role in the pathogenesis of gas gangrene. CpPLC may lead to cell lysis at concentrations that cause extensive degradation of plasma membrane phospholipids. However, at sublytic concentrations it induces cytotoxicity without inducing evident membrane damage. The results of this work demonstrate that CpPLC becomes internalized in cells by a dynamin-dependent mechanism and in a time progressive process: first, CpPLC colocalizes with caveolin both at the plasma membrane and in vesicles, and later it colocalizes with early and late endosomes and lysosomes. Lysosomal damage in the target cells is evident 9 h after CpPLC exposure. Our previous work demonstrated that CpPLCinduces ERK1/2 activation, which is involved in its cytotoxic effect. In this work we found that cholesterol sequestration, dynamin inhibition, as well as inhibition of actin polymerization, prevent CpPLC internalization and ERK1/2 activation, involving endocytosis in the signalling events required for CpPLC cytotoxic effect at sublytic concentrations. These results provide new insights about the mode of action of this bacterial phospholipase C, previously considered to act only locally on cell membrane.

Bacterial Sphingomyelinases and Phospholipases as Virulence Factors

“…perfringens alpha-toxin induces PKC activation in rabbit erythrocytes, rabbit neutrophils, MDCK cells, and gangliosidedeficient cells (8,226,236). At sublytic concentrations, alphatoxin is internalized, inducing ERK1/2 activation and triggering NF-B in a MEK/ERK-dependent manner (236,237). PKC, MEK/ ERK, and NF-B signaling induced by C. perfringens alpha-toxin results in ROS production and cell death, and inhibition of either of these signaling pathways significantly reduces cytotoxicity in cultured cells and myotoxicity in vivo (222,236).…”

“…PKC, MEK/ ERK, and NF-B signaling induced by C. perfringens alpha-toxin results in ROS production and cell death, and inhibition of either of these signaling pathways significantly reduces cytotoxicity in cultured cells and myotoxicity in vivo (222,236). C. perfringens alpha-toxin is internalized in a dynamin-dependent manner, reaches early and late endosomes, and causes lysosomal damage (237). Furthermore, dynamin inhibition, which impairs alpha-toxin internalization, also inhibits its cytotoxic effect (237).…”

“…C. perfringens alpha-toxin is internalized in a dynamin-dependent manner, reaches early and late endosomes, and causes lysosomal damage (237). Furthermore, dynamin inhibition, which impairs alpha-toxin internalization, also inhibits its cytotoxic effect (237). ⌻herefore, C. perfringens alpha-toxin, previously considered to act only locally on the plasma membrane, has a more complex mode of action.…”

Membrane-damaging and cytotoxic sphingomyelinases and phospholipases

“…α-toxin induces PKC activation in rabbit erythrocytes, rabbit neutrophils, MCDK cells, and gangliosidedeficient cells [145]. At sublytic concentrations, in ganglioside-deficient cells, α-toxin is internalized, which induces ERK1/2 activation and triggers the NFκB pathway, in a MEK/ERK cascade-dependent manner [28,145,146].…”

“…α-toxin induces PKC activation in rabbit erythrocytes, rabbit neutrophils, MCDK cells, and gangliosidedeficient cells [145]. At sublytic concentrations, in ganglioside-deficient cells, α-toxin is internalized, which induces ERK1/2 activation and triggers the NFκB pathway, in a MEK/ERK cascade-dependent manner [28,145,146]. The activation of the PKC, MEK/ERK, and NFκB signaling induced by α-toxin results in reactive oxygen species (ROS) production, oxidative stress, lysosomal damage, and cell death [28,145] (Figure 22.3).…”