Apoptosis, a type of programmed cell death, is the evolutionarily conserved biochemical pathway that plays essential role in regulating normal development and homeostasis in multi-cellular organism. The present study is to investigate the molecular mechanisms that regulate apoptosis. Data on subcellular fractionation and fluorescence microscopy suggest the increase in association of actin-regulating protein cofilin with cytoskeletal actin filaments (F-actin) before mitochondrial insertion of Bax and mitochondrial fission in apoptotic induction, implying that cofilin could change the actin dynamics during early apoptosis. Further investigation reveals the observation on the increase in mitochondrial association of actin in early apoptosis. By subcellular fractionation, it suggests the mi...[ Read more ]

Apoptosis, a type of programmed cell death, is the evolutionarily conserved biochemical pathway that plays essential role in regulating normal development and homeostasis in multi-cellular organism. The present study is to investigate the molecular mechanisms that regulate apoptosis. Data on subcellular fractionation and fluorescence microscopy suggest the increase in association of actin-regulating protein cofilin with cytoskeletal actin filaments (F-actin) before mitochondrial insertion of Bax and mitochondrial fission in apoptotic induction, implying that cofilin could change the actin dynamics during early apoptosis. Further investigation reveals the observation on the increase in mitochondrial association of actin in early apoptosis. By subcellular fractionation, it suggests the mitochondrial translocation of β-actin occurred before the mitochondrial insertion of Bax and release of cytochrome c in apoptosis. The translocation of β -actin was observed with various apoptotic stimuli in various cell lines, suggesting that this is a general apoptotic phenomenon in mammalian systems. By microscopy, it shows that an apoptotic induction triggered the reorganization of F-actin network with an increase in association with mitochondria, which was observed before mitochondrial fission and nuclear condensation that characterize apoptosis. The observation on the increase in association of cofilin to F-actin suggests that cofilin could facilitate the translocation of actin in early apoptosis. Perhaps actin could contribute to the initiation of apoptosis by enabling cytosolic proapoptotic proteins to be carried to mitochondria by the cytoskeleton-driven trafficking system. Cell death-inducing DFF45-like effector (CIDE) family protein has been reported as a proapoptotic family which causes nuclear condensation during apoptosis. Fluorescent microscopy shows that GFP-CIDE-A/B transfected in Cos-7 cells localized in cytosolic vacuoles. This provides an important insight into a potential mechanism of CIDEs in apoptosis, as cytosolic vacuole is a dynamic organelle that could serves as the proapoptotic calcium reservoir which could regulate cytoplasmic calcium oscillation for signaling the initiation of apoptosis.