Mitochondrial outer membrane permeabilization (MOMP), also known as the mitochondrial outer membrane permeability, is one of two ways
apoptosis
Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes incl ...
(programmed cell death) can be activated.
It is part of the
intrinsic pathway of apoptosis, also known as the mitochondrial pathway. MOMP is known as the point of no return in apoptosis. Once triggered, it results in the diffusion of proteins from the space between the inner and outer mitochondrial membranes into the
cytosol
The cytosol, also known as cytoplasmic matrix or groundplasm, is one of the liquids found inside cells (intracellular fluid (ICF)). It is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondri ...
.
Mechanism
Initiation of MOMP involves
Bcl-2 family
The Bcl-2 familyTC# 1.A.21 consists of a number of evolutionarily-conserved proteins that share Bcl-2 homology (BH) domains. The Bcl-2 family is most notable for their regulation of apoptosis, a form of programmed cell death, at the mitochondrion. ...
proteins, including
BAX and
BAK.
The outer mitochondrial membrane, typically permeable to molecules smaller than 5 k
Da, forms pores during MOMP that allow it to accommodate proteins larger than 100 kDa. During MOMP, it takes about five minutes for all mitochondrial membranes within a cell to permeabilize.
Outcome
MOMP has been referred to as the point of no return for apoptosis, almost always resulting in the completion of the process, and thus, cell death.
However, in limited circumstances, apoptosis does not complete. Sometimes, MOMP does not complete, known as incomplete MOMP (iMOMP) or minority MOMP (miniMOMP). For incomplete MOMP, mitochondrial membranes become permeable in most, but not all, the cell's mitochondria. In minority MOMP, only a few mitochondria of the cell experience MOMP—the result of sublethal stress.
References
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Apoptosis
Mitochondria