Apoptotic redistribution

Marguet, D Luciani, M.F., Moynault, A., WiUiamson, P., and Chimini, G., 1999, Engulfment of apoptotic cells involves the redistribution of membrane phosphatidylserine on phagocyte and prey, iVttt. Cell Biol. 1 454-456. 

These same authors also report a dose-dependent increase in the apoptotic rate after the administration of gemcitabine (33), which they believe correlates with the elimination of the more radioresistant S phase population of cells and redistribution of the remaining cells into more radiosensitive compartments of the cell cycle. They also report in another study that reoxygenation of the resistant hypoxic fraction of tumor cells is also a mechanism for the action of gemcitabine (34). Therefore, elimination of these S phase tumor cells may aid the radiation response by not only causing cell cycle synchronization but also by leading to reoxygenation of hypoxic cells. 

Transactivation of proapoptotic genes is not the only way that p53 protein can activate the apoptotic program. There is evidence that variants of p53, which are independent of Bax protein and do not operate at the transcription level, can also result in apoptosis (see Haffner and Oren, 1995 Ko and Prives, 1996). Thus, a p53-regulated redistribution of the Fas death receptor from the cytosol to the cell membrane has been demonstrated (Beimet et al., 1998). Overall, these mechanisms are poorly understood. 

In contrast to PS, the function of PE exposure during apoptosis is largely unclear. We have recently found that exposure of PE on cell surface at the cleavage furrow is essential for completion of cell division (Emoto et al., 1996). We have further shown that redistribution of PE on the cleavage furrow contributes to regulation of actin filament reorganization in cell division (Umeda and Emoto, 1999 Emoto and Umeda, 2000). Interestingly, the transbilayer redistribution of PE in apoptotic cells is specifically... 

McCutcheon, J., Haslett, C. and Dransfield, I. (1995). Regulation of macrophage recognition of apoptotic cells by activation of protein kinases, redistribution of the integrin av 0. Submitted. 

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