Ostreolysin A/Pleurotolysin B and Equinatoxins: Structure, Function and Pathophysiological Effects of These Pore-Forming Proteins

Abstract

Acidic ostreolysin A/pleurotolysin B (OlyA/PlyB, formerly known as ostreolysin (Oly), and basic 20 kDa equinatoxins (EqTs) are cytolytic proteins isolated from the edible mushroom Pleurotus ostreatus and the sea anemone Actinia equina, respectively. Both toxins, although from different sources, share many similar biological activities: (i) colloid-osmotic shock by forming pores in cellular and artificial membranes enriched in cholesterol and sphingomyelin; (ii) increased vascular endothelial wall permeability in vivo and perivascular oedema; (iii) dose-dependent contraction of coronary vessels; (iv) haemolysis with pronounced hyperkalaemia in vivo; (v) bradycardia, myocardial ischemia and ventricular extrasystoles accompanied by progressive fall of arterial blood pressure and respiratory arrest in rodents. Both types of toxins are haemolytic within nanomolar range concentrations, and it seems that hyperkalaemia plays an important role in toxin cardiotoxicity. However, it was observed that the haemolytically more active EqT III is less toxic than EqT I, the most toxic and least haemolytic EqT. In mice, EqT II is more than 30 times more toxic than OlyA/PlyB when applied intravenously. These observations imply that haemolysis with hyperkalaemia is not the sole cause of the lethal activity of both toxins. Additional mechanisms responsible for lethal action of the two toxins are direct effects on heart, coronary vasoconstriction and related myocardial hypoxia. In this review, we appraise the pathophysiological mechanisms related to the chemical structure of OlyA/PlyB and EqTs, as well as their toxicity.

Antiviral, Cytotoxic, and Antioxidant Activities of Three Edible Agaricomycetes Mushrooms: Pleurotus columbinus, Pleurotus sajor-caju, and Agaricus bisporus

“…Pleurotolysin was detected in the Pleurotus species. It is a sphingomyelin-specific cytolysin composed of two subunits (17 and 59 kDa) that integrate to cause an outflow of K ions leading to selective lysis of cancer cells [ 81 , 82 ]. Serine proteinase plays an important role in the antiviral properties of mushrooms [ 83 ].…”

The Potential of UV-B Irradiated Oyster Mushroom (Pleurotus ostreatus) Powder on Plasma Glucose and TNF-α Levels in Type 2 Diabetic Rats

“…This protein binds to lipid membranes and forms pores, 25 disrupting cell membrane integrity and causing cells to lyse. 26 The disruption in membrane structure causes cell damage, triggering lipid peroxidation, and increasing oxidative stress, 27 which results in inflammation.…”

Advances in Cardiotoxicity Induced by Altered Mitochondrial Dynamics and Mitophagy

“…Generally, hypoxia refers to any kind of physiological oxygen deficiency or tissue oxygen demand deficiency state and the integration of local responses defines hypoxia as a paradigm of reactions affecting the entire body (86,132,133). Studies have shown that inhibiting the breathing of rats caused obvious cardiotoxicity (79, [134][135][136][137][138].…”