Apoptosis - the path of precise regulation of cell death
There are many ways to end cell life, and apoptosis is only one of them, to ensure that they are detected is indeed the signal of apoptosis, you need to understand at least the following knowledge.
What plays an important role in apoptosis?
Apoptosis, often also said "cell suicide", is very important for the development of the body organs and the normal functioning of the body, our body needs to remove some unwanted, damaged, potentially harmful cells. However, in some cases, such as the occurrence of cancer, the disorder of the apoptosis process leads to uncontrollable cell survival and growth, or another situation such as heart attack leads to impaired apoptosis and kill more innocent cells. For human health, this process is so important, so scientists have invested a lot of enthusiasm to understand how different diseases in the environment to inhibit or induce apoptosis.
What induced the apoptosis of a cell?
Sudden elimination of survival signals or separation of cells from adjacent cells can cause apoptosis, increased extracellular pressure such as exposure to high fever conditions and DNA damage due to radiation / chemotherapy or pathogen infection can also lead to apoptosis, some cells Surface expression of death receptors such as TNF-a, when ligand binding or protein cross-linking will induce apoptosis.
The molecular mechanism of apoptosis
The classical apoptosis mechanism is divided into endogenous signaling pathways and exogenous signaling pathways.
· Introduction to endogenous signaling pathways·
When the cells are damaged by DNA, the endogenous signaling pathway is initiated within 2 hours, first by the activation of the apoptotic protein Bcl-2 antagonist Bak and Bcl-2 binding protein Bax induced by the apoptotic protein Bid, Began to destroy the cell energy plant mitochondria, they form a polymer inserted into the outer membrane caused by the formation of small holes on the membrane and eventually lead to decreased membrane potential and the release of key proteins, once the outer membrane is infiltrated, the apoptosis is irreversible. Mitochondrial release of molecules such as cytochrome c binding to the cytoplasmic apoptotic protease activator Apaf-1 forms a structure called apoptotic bodies, the death signal is amplified, and ultimately by two types of proteases that initiate caspases and effects of caspases to perform key proteins Cut, cell death pathway activation and survival pathway closure. Caspase-3 is the primary effect of caspases, which is initiated by caspase-9.
· Introduction to exogenous signal pathways·
Specific ligands such as Fas or tumor necrosis factor TNF-a bind to the corresponding death receptor Fas (also known as CD95) or TNF receptor 1 (TNFR1, also known as CD120a) each induced apoptosis, followed by death receptor aggregation and recruitment Caspase-8 and adapter protein FADD form death-induced signal complex DISC. Caspase-8 is thus activated and subsequently activates other caspases, which also interact with Bid to activate endogenous pathways.
How to detect apoptosis at different stages?
The occurrence of apoptosis is not overnight, from the initial cell shrinkage to the subsequent DNA fragments to the final formation of apoptotic bodies throughout the journey there are a number of landmark events, then we come to inventory how to capture the different stages of apoptosis Under the footsteps of it:
1. Direct method can be real-time cell imaging to observe the shape of the cell changes, such as cytoplasm can be seen bubble.
2. At the beginning, the activity of various caspases can be detected by western blotting or fluorescently labeled caspases inhibitors (FLICA ™).
3. Early in the morning, can also monitor the mitochondrial membrane potential of the sudden drop.
4. In the early stage, the asymmetric phospholipid bilayer rearrangement of the cytosolic membrane, phosphatidylserine (PS) eversion, can be detected using Annexin V Kits.
5. In the late stage, DNA fragmentation can be detected using TUNEL (Terminal deoxynucleotidyl transferase dUTP Nick End Labeling) Assay. DNA is exposed to the 3 'end after cleavage, the kit connects Br-dUTP to the 3' end and uses biotin or fluorescently labeled antibodies for flow or immunohistochemistry to detect BrdU.
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