Apoptosis degradation activity

Caspases are intracellular proteases and cleave their substrate proteins specifically behind an aspartate residue. Caspases are normally present as inactive proenzymes. However, during apoptosis, caspase activation is induced by cleavage at specific internal aspartate residues. Activation of the initiator caspases by pro-apoptotic signals leads to proteolytic activation of the execution caspases, which cleave a set of vital proteins and thus initiate and execute the apoptotic degradation phase. A self-contained on-chip cell culture and pretreatment microdevice system has been developed for the screening of caspase-3 expression in apoptotic cells. 

Numerous studies have demonstrated that degradation products of (3-carotene exhibit deleterious effects in cellular systems (Alija et al., 2004, 2006 Hurst et al., 2005 Salerno et al., 2005 Siems et al., 2003). A mixture of (3-carotene degradation products exerts pro-apoptotic effects and cytotoxicity to human neutrophils (Salerno et al., 2005 Siems et al., 2003), and enhances the geno-toxic effects of oxidative stress in primary rat hepatocytes (Alija et al., 2004, 2006), as well as dramatically reduces mitochondrial activity in a human leukaemic cell line, K562, and RPE 28 SV4 cell line derived from stably transformed fetal human retinal pigmented epithelial cells (Hurst et al., 2005). As a result of degradation or enzymatic cleavage of (3-carotene, retinoids are formed, which are powerful modulators of cell proliferation, differentiation, and apoptosis (Blomhoff and Blomhoff, 2006). 

Systematic cell degradation and death, apoptosis, on the other hand, is thought to be necessary to avoid cell damage accumulating so as to cause incorrect differentiation. The process is very complicated involving activation of a number of destructive enzymes where once more increase in cell calcium often initiates the hydrolyses using special internal calcium-dependent enzymes, calpains (see Demaurex in Further Reading). 

Necrosis is a dramatic and very rapid form of cell death in which essentially every compartment of the cell disintegrates. Necrosis is characterized by marked dysregulation of ion homeostasis resulting in cell swelling, dilation of mitochondria and the ER and the formation of vacuoles in the cytoplasm [33], Proteases play important roles in the degradation of cells during necrosis. In contrast to apoptosis, where caspases are the key death proteases, calpains and lysosomal proteases (cathepsins B and D, in particular) are major players in necrosis. Caspases may be activated in response to mitochondrial damage and... 

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