Visual and functional demonstration of growing Bax-induced pores in mitochondrial outer membranes.
Visual and functional demonstration of growing Bax-induced pores in mitochondrial outer membranes.
复制标题
DOI：
10.1091/mbc.e13-11-0638
复制
发表时间：
2015-01-15
影响因子：
3.3
通讯作者：
Kuwana T
中科院分区：
文献类型：
--
作者：
Gillies LA;Du H;Peters B;Knudson CM;Newmeyer DD;Kuwana T
We visualized Bax-induced pores in outer membrane vesicles (OMVs) using cryo-electron microscopy and monitored dextran release from these vesicles by flow cytometry. The data argue that Bax promotes mitochondrial outer membrane permeabilization by inducing the formation of large, solitary, and growing pores through a mechanism involving membrane-curvature stress. Bax induces mitochondrial outer membrane permeabilization (MOMP), a critical step in apoptosis in which proteins are released into the cytoplasm. To resolve aspects of the mechanism, we used cryo-electron microscopy (cryo-EM) to visualize Bax-induced pores in purified mitochondrial outer membranes (MOMs). We observed solitary pores that exhibited negative curvature at their edges. Over time, the pores grew to ∼100–160 nm in diameter after 60–90 min, with some pores measuring more than 300 nm. We confirmed these results using flow cytometry, which we used to monitor the release of fluorescent dextrans from isolated MOM vesicles. The dextran molecules were released gradually, in a manner constrained by pore size. However, the release rates were consistent over a range of dextran sizes (10–500 kDa). We concluded that the pores were not static but widened dramatically to release molecules of different sizes. Taken together, the data from cryo-EM and flow cytometry argue that Bax promotes MOMP by inducing the formation of large, growing pores through a mechanism involving membrane-curvature stress.
