Cholesterol induce oligomerization of Vibrio vulnificus cytolysin specifically

Abstract

Vibrio vulnificus cytolysin (VVC) has been implicated as one of the important virulence determinants of V. vulnificus that causes serious septicemia and wound infection. An attempt was made to investigate that VVC could act as a ligand which stimulates intracellular signaling systems. Cholesterol dose-dependently blocked VVC hemolytic activity through oligomerization of cytolysin. Among cholesterol derivatives including 7-dehydrocholesterol, cholesteryl esters, deoxycholate, and cholestane tested, only 7-dehydrocholesterol induced oligomerization as well as inactivation of VVC. These results show that oligomerization of VVC is completely dependent on three-dimensional structure of cholesterol where specific interaction of cholesterol at oligomerization sites of VVC is very selective. These findings support the idea that cholesterol which constitute many of cellular plasma membrane could be a receptor of VVC on plasma membrane of target cells.

Inactivation of Vibrio vulnificus Hemolysin by Oligomerization but Not Proteolysis

“…As the VvhA oligomer observed in this study was different to the cholesterol-mediated oligomerization (tetramer, about 210 kDa) of VvhA, 20,21) we can not state clearly as to whether the oligomerization of VvhA occurs spontaneously, or is mediated by unknown components of the HI broth or by unknown products derived from dying V. vulnificus in the late growth phase. Nevertheless, our results evidently demonstrate that the hemolytic activity of VvhA in the late growth phase is inactivated by the oligomerization of VvhA, but not by the proteolytic cleavage of VvhA by VvpE or other proteases as believed previously.…”

“…This raises the possibility that only very small amounts of VvhA may be produced in vivo, 18,19) and the produced VvhA may be rapidly inactivated by host factors such as cholesterol and bacterial factors such as VvpE. 5,16,[20][21][22] Therefore, in order to evidently determine the pathogenetic roles of VvhA, further detailed studies regarding the in vitro and in vivo production and inactivation of VvhA are necessary.Physiologically, VvhA is produced in the early growth phase, and becomes abruptly inactivated in the late growth phase with the concomitant production of VvpE. Accordingly, it has been classically believed that the inactivation of VvhA is attributable to the destruction of VvhA by VvpE.…”

The Aromatic Ring of Phenylalanine 334 Is Essential for Oligomerization ofVibrio vulnificusHemolysin

“…7B). It is also well known that VVH binds to cholesterol in vitro (10,35), but the cholesterol binding site has not yet been defined. Interestingly, VVH does not have the tryptophan-rich motif that is highly conserved in gpCDCs and is involved in membrane recognition (3,9,27).…”

“…VVH binds directly to cholesterol and is oligomerized in vitro. Once VVH forms the VVH-cholesterol complex, it can no longer bind to susceptible cells (10). Therefore, VVH could be considered a member of the cholesterol-dependent cytolysin (CDC) toxin family (35).…”

Human Serum Albumin Enhances the Hemolytic Activity of Vibrio vulnificus

“…[11][12][13] The inactivation of the vvhA gene does not affect mouse-lethality, which raises the possibility that only small amounts of VvhA are produced in vivo, 14,15) and that this VvhA is rapidly inactivated by host factors like cholesterol and bacterial factors such as proteases. 5,12,[16][17][18] Therefore, in order to better characterize the pathogenetic roles of VvhA, further detailed studies regarding the in vitro and in vivo production and inactivation of VvhA are required.…”