Implication of Cholesterol in Regulating the Pore‐formation Mechanism of Vibrio Cholerae Cytolysin, a β‐barrel Pore‐forming toxin

Abstract

Vibrio cholerae cytolysin (VCC) is a β‐barrel pore‐forming toxin with potent cell‐killing cytolytic/cytotoxic activity. To exert it's cytolytic effect, VCC binds to the target cell membranes and forms transmembrane oligomeric β‐barrel pores. Earlier studies have indicated that cholesterol might play a critical role in regulating the mode of action of VCC. However, exact mechanistic basis of the process still remains unknown. In the present study, we have explored and examined the roles of cholesterol in the different steps of VCC mode of action. Employing the membrane lipid bilayer of lipid vesicles or liposomes containing varying amount of cholesterol, we have shown that cholesterol governs the efficient interaction of the toxin with the membrane lipid bilayer that in turn facilitates subsequent oligomeric pore‐formation process. We have also studied the physiological relevance of membrane cholesterol in the context of the biomembranes of the eukaryotic cells. Our results have shown that the depletion of membrane cholesterol from erythrocytes compromises the pore‐forming activity of VCC. In the biomembrane of erythrocytes, where accessory interactions are available, binding of VCC is not affected to any significant extent. However, upon depletion of membrane cholesterol in the erythrocytes membranes, membrane‐bound fraction of VCC remains trapped in the form of abortive oligomeric assembly, and does not form the functional pores. Our study has also revealed that VCC shows a marked tendency to associate with the cholesterol‐rich membrane micro‐domains on erythrocytes that, in turn, appears to facilitate cholesterol‐dependent pore‐formation mechanism of the toxin. In sum, our results suggest that the presence of cholesterol in the target membranes play critical role for the pore‐formation mechanism of VCC.Support or Funding InformationWe acknowledge the support through funding from the Department of Biotechnology (DBT), Govt. of India [DBT grant no. BT/HRD/NBA/37/01/2014 (x)] and also the support through funding under the Centre of Excellence (COE) in Frontier Areas of Science and Technology (FAST) program of the Ministry of Human Resource Development, Govt. of India, in the area of protein science, design, and engineering (to K.C.). We also thank the Indian Institute of Science Education and Research Mohali for the support.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.