Untitled - D Ank Unlimited

apoptosis, necrosis and 75 apoptosis, negative induction
The inhibitor of apoptosis proteins XIAP, cIAP-1, and Survivin can
prevent proteolytic processing of procaspases 3, 6, and 7 by blocking
cytochrome-c-induced activation of procaspase 9.
apoptosis, necrosis and
Apoptosis and necrosis are two major processes by which
cells die. Apoptosis is the ordered disassembly of cells from
within. Disassembly creates changes in the phospholipid content
of the plasma membrane outer leaflet. Phosphatidylserine
(PS) is exposed on the outer leaflet, and phagocytic cells
that recognize this change may engulf the apoptotic cell or
cell-derived, membrane-limited apoptotic bodies. Necrosis
normally results from a severe cellular insult. Both internal
organelle and plasma membrane integrities are lost, resulting
in spilling of cytosolic and organellar contents into the surrounding
environment. Immune cells are attached to the area
and begin producing cytokines that generate an inflammatory
response. Thus, cell death in the absence of an inflammatory
response may be the best way to distinguish apoptosis from
necrosis. Other techniques that have been used to distinguish
apoptosis from necrosis in cultured cells and in tissue sections
include detecting PS at the cell surface with annexin
V binding, DNA laddering, and staining cleaved DNA
fragments that contain characteristic ends. At the extremes,
apoptosis and necrosis clearly involve different molecular
mechanisms. It is not clear whether there is cellular death
involving the molecular mechanisms of both apoptosis and
necrosis. Cell death induced by free radicals, however, may
have characteristics of apoptosis and necrosis.
The inhibitor of apoptosis protein FLIP interacts with FADD and procaspase
8, blocking activation of caspase 8 and thereby suppressing deathreceptor-induced
apoptosis.
apoptosis, negative induction
Negative induction of apoptosis by loss of a suppressor
activity involves the mitochondria. Release of cytochrome c
from the mitochondria into the cytosol serves as a trigger to
activate caspases. Permeability of the mitochondrial outer
membrane is essential to initiation of apoptosis through this
pathway. Proteins belonging to the Bcl-2 family appear to
regulate the membrane permeability to ions and possibly
to cytochrome c as well. Although these proteins can form
channels in membranes, the molecular mechanisms by which
they regulate mitochondrial permeability and the solutes
released are less clear. The Bcl-2 family is composed of a
Apoptotic cell death resulting from free-radical exposure involves mitochondria. In cells undergoing apoptosis, mitochondria release AIF (apoptosis-inducing
factor) and cytochrome c. The anti-apoptotic mitochondrial protein Bcl-2 inhibits free-radical-induced apoptosis.
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