TY - JOUR
T1 - Cholesterol Effects on BAX Pore Activation
AU - Christenson, Eric
AU - Merlin, Sean
AU - Saito, Mitsu
AU - Schlesinger, Paul
N1 - Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2008/9/19
Y1 - 2008/9/19
N2 - The importance of BCL-2 family proteins in the control of cell death has been clearly established. One of the key members of this family, BAX, has soluble, membrane-bound, and membrane-integrated forms that are central to the regulation of apoptosis. Using purified monomeric human BAX, defined liposomes, and isolated human mitochondria, we have characterized the soluble to membrane transition and pore formation by this protein. For the purified protein, activation, but not oligomerization, is required for membrane binding. The transition to the membrane environment includes a binding step that is reversible and distinct from the membrane integration step. Oligomerization and pore activation occur after the membrane integration. In cells, BAX targets several intracellular membranes but notably does not target the plasma membrane while initiating apoptosis. When cholesterol was added to either the liposome bilayer or mitochondrial membranes, we observed increased binding but markedly reduced integration of BAX into both membranes. This cholesterol inhibition of membrane integration accounts for the reduction of BAX pore activation in liposomes and mitochondrial membranes. Our results indicate that the presence of cholesterol in membranes inhibits the pore-forming activity of BAX by reducing the ability of BAX to transition from a membrane-associated protein to a membrane-integral protein.
AB - The importance of BCL-2 family proteins in the control of cell death has been clearly established. One of the key members of this family, BAX, has soluble, membrane-bound, and membrane-integrated forms that are central to the regulation of apoptosis. Using purified monomeric human BAX, defined liposomes, and isolated human mitochondria, we have characterized the soluble to membrane transition and pore formation by this protein. For the purified protein, activation, but not oligomerization, is required for membrane binding. The transition to the membrane environment includes a binding step that is reversible and distinct from the membrane integration step. Oligomerization and pore activation occur after the membrane integration. In cells, BAX targets several intracellular membranes but notably does not target the plasma membrane while initiating apoptosis. When cholesterol was added to either the liposome bilayer or mitochondrial membranes, we observed increased binding but markedly reduced integration of BAX into both membranes. This cholesterol inhibition of membrane integration accounts for the reduction of BAX pore activation in liposomes and mitochondrial membranes. Our results indicate that the presence of cholesterol in membranes inhibits the pore-forming activity of BAX by reducing the ability of BAX to transition from a membrane-associated protein to a membrane-integral protein.
KW - BCL-2 family
KW - apoptosis
KW - cholesterol
KW - pore formation
KW - protein-membrane interactions
UR - http://www.scopus.com/inward/record.url?scp=48749122796&partnerID=8YFLogxK
U2 - 10.1016/j.jmb.2008.06.037
DO - 10.1016/j.jmb.2008.06.037
M3 - Article
C2 - 18590739
AN - SCOPUS:48749122796
VL - 381
SP - 1168
EP - 1183
JO - Journal of Molecular Biology
JF - Journal of Molecular Biology
SN - 0022-2836
IS - 5
ER -