生物化学翻译

To show that HAX-1 degradation is part of the apoptotic process and any involvement Omi may have， we used the ucf-101 inhibitor. ucf-101 is a specific inhibitor of the proteolytic activity of Omi and has been described previously (13). When... To show that HAX-1 degradation is part of the apoptotic process and any involvement Omi may have， we used the ucf-101 inhibitor. ucf-101 is a specific inhibitor of the proteolytic activity of Omi and has been described previously (13). When HK-2 cells were treated with cisplatin in the presence of ucf-101， the percentage of apoptotic cells decreased and the inhibitor significantly blocked HAX-1 degradation. This effect was more pronounced when a higher concentration of the inhibitor was used.

To confirm the specificity of the inhibitor in this system and exclude the possibility that another protease rather than Omi is involved in HAX-1 cleavage， we used cell lines derived from mnd2 mice (9). The parent cell line (mnd2-MSCV) derived from mouse embryo fibroblasts has no detectable Omi proteolytic activity (9). The same cell line has been transfected with wild type human Omi cDNA (mnd2-MSCV-Omi) and expresses high levels of active Omi protein (14). We found that in mnd2-MSCV cells， when induced to undergo apoptosis with various stimuli， the number of apoptotic cells was very low. Furthermore， no detectable cleavage of HAX-1 was observed. This is in contrast with the mnd2-MSCV-Omi cells where apoptosis was robust， and HAX-1 levels were inversely proportional to the degree of apoptosis. This experiment clearly shows that Omi is solely responsible for HAX-1 cleavage， which is essential for apoptosis under the conditions used in these experiments. HAX-1 subcellular localization depends on cell type (21， 30) and has been reported to be present in the mitochondria， cytoplasm， or plasma membrane (10， 21， 22， 30). We performed subcellular fractionation to investigate where HAX-1 cleavage by Omi takes place. We found that， in HEK293 cells， HAX-1 was predominantly present in the mitochondria， and this localization did not change in response to apoptotic stimuli. This suggests that Omi can initiate apoptosis in the mitochondria by cleaving HAX-1 protein. This is in accord with a recent study that shows Omi can induce apoptosis in human neutrophils treated with TNF- without being released from the mitochondria (7). Although several studies clearly define HAX-1 as an anti-apoptotic protein， the mechanism of its function is unknown. HAX-1 has sequence similarity to Bcl-2 family of proteins (10， 22).