Calcium is involved in several steps of the apoptotic process. In nuclei, endonucleases are presumed to be the main targets of calcium; however, little is known about its role during the cytosolic phase of apoptosis. We used a cell-free system to address this question. Our results show that CaCl 2 triggered nuclear apoptosis (i.e. typical morphological change and DNA fragmentation) at concentrations of 5 mM. This concentration was lowered 10-fold by the co-incubation with cytosolic extracts from nonapoptotic cells. Apoptotic changes induced by the incubation of nuclei with CaCl 2 in the presence of these cytosols were strongly reduced in the presence of an inhibitor of caspase-3 and to a lesser extent by an inhibitor of caspase-1. We also show that calcium-induced apoptosis is affected by protease inhibitors such as N-tosyl-L-phenylalanine chloromethyl ketone, but not by calpain or several lysosomal protease inhibitors. The addition of CaCl 2 to the cell-free system increased a caspase-3 activity in nonapoptotic cytosols as shown by specific antibodies and an enzymatic assay. No activation of a caspase-3-like activity by the addition of cytochrome c was observed in these extracts under similar conditions. The enhanced caspase-3 activity induced by calcium was inhibited by protease inhibitors affecting morphological nuclear apoptosis except for those responsible for the degradation of lamin A. These results suggest that CaCl 2 could trigger, in normal cells, an apoptotic cascade through the activation of cytosolic caspase-3 activity.

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The interaction of the anti-apoptotic members of the Bcl-2 family with mitochondria, through their hydrophobic Cterminus, has been proposed to play a crucial role in the execution phase of apoptosis. We report here that a substitution of the C-terminal end of pro-apoptotic bax by that of antiapoptotic bcl-xL (baxCxL) does not modify its association with mitochondria in human and rat cells or in Saccharomyces cerevisiae. In addition, while bax sensitizes these cells to apoptotic stimuli, the construct baxCxL does not affect the apoptotic response in transfected cells. These results suggest that the C-terminus of bax plays an important role in apoptosis independently of its membrane addressing/targeting mechanism. ß

Phages are envisioned for a variety of uses including (1) the biocontrol of pathogenic bacteria in agriculture and food industries, (2) the modulation of dysbiotic flora, (3) the eradication of pathogenic bacteria infecting humans or animals. The scope of the present review is limited to the medical setting in human, when a therapeutic effect is needed against a clearly defined bacterial target (or a few defined targets simultaneously).

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