Perfringolysin O Theta Toxin as a Tool to Monitor the Distribution and Inhomogeneity of Cholesterol in Cellular Membranes.

Masashi Maekawa,Yanbo Yang,Gregory Fairn

doi:10.3390/toxins8030067

Masashi Maekawa, Yanbo Yang + Show 1 more

Open Access

https://doi.org/10.3390/toxins8030067

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Abstract

Cholesterol is an essential structural component of cellular membranes in eukaryotes. Cholesterol in the exofacial leaflet of the plasma membrane is thought to form membrane nanodomains with sphingolipids and specific proteins. Additionally, cholesterol is found in the intracellular membranes of endosomes and has crucial functions in membrane trafficking. Furthermore, cellular cholesterol homeostasis and regulation of de novo synthesis rely on transport via both vesicular and non-vesicular pathways. Thus, the ability to visualize and detect intracellular cholesterol, especially in the plasma membrane, is critical to understanding the complex biology associated with cholesterol and the nanodomains. Perfringolysin O (PFO) theta toxin is one of the toxins secreted by the anaerobic bacteria Clostridium perfringens and this toxin forms pores in the plasma membrane that causes cell lysis. It is well understood that PFO recognizes and binds to cholesterol in the exofacial leaflets of the plasma membrane, and domain 4 of PFO (D4) is sufficient for the binding of cholesterol. Recent studies have taken advantage of this high-affinity cholesterol-binding domain to create a variety of cholesterol biosensors by using a non-toxic PFO or the D4 in isolation. This review highlights the characteristics and usefulness of, and the principal findings related to, these PFO-derived cholesterol biosensors.

Highlights

Most of the cholesterol-dependent cytolysins (CDCs) are bacterial pore-forming toxins that bind to cholesterol in the plasma membrane of mammalian cells [1,2,3]
We highlight a variety of the cholesterol biosensors derived from Perfringolysin O (PFO)
Despite the usefulness of the PFO-derived cholesterol biosensors to visualize and detect intracellular cholesterol, attention should be paid to the fact that changes of binding of the PFO-derived cholesterol biosensors do not always directly correlate with changes in the cholesterol concentration in membranes

Summary

Introduction

Most of the cholesterol-dependent cytolysins (CDCs) are bacterial pore-forming toxins that bind to cholesterol in the plasma membrane of mammalian cells [1,2,3]. CDCs are secreted by a variety of Gram-positive bacteria including but not limited to Bacillus, Listeria, Streptococcus, Clostridium, and Lactobacillus [5] Binding of these water-soluble CDCs to cholesterol in the exofacial leaflets of the plasma membrane induces the oligomerization of the toxins (30–50 monomers) [1,6,7,8]. Another example of toxins used as tools for cell biology include the non-toxic B subunits of Cholera and Shiga toxins (CTxB and STxB, respectively) that bind to the exofacial glycosphingolipids GM1 and Gb3, respectively [25,26] Thanks to both the development of these lipid biosensors and advances in microscopic techniques, our understanding of cell biology continues to progress, especially in the field of lipid trafficking.

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Concluding Remarks