proposed a set of recommendations for the definition of distinct cell death morphologies and for the appropriate use of cell death-related terminology, including 'apoptosis', 'necrosis' and 'mitotic catastrophe'. In view of the substantial progress in the biochemical and genetic exploration of cell death, time has come to switch from morphological to molecular definitions of cell death modalities. Here we propose a functional classification of cell death subroutines that applies to both in vitro and in vivo settings and includes extrinsic apoptosis, caspase-dependent or -independent intrinsic apoptosis, regulated necrosis, autophagic cell death and mitotic catastrophe. Moreover, we discuss the utility of expressions indicating additional cell death modalities. On the basis of the new, revised NCCD classification, cell death subroutines are defined by a series of precise, measurable biochemical features.

Geldanamycin (GA),

Recent evidence indicates that anti-apoptotic functions of Bcl-2 can be regulated by its phosphorylation. According to the 'mitotic arrest-induced' model, multi-site phosphorylation of the Bcl-2 loop domain is followed by cell death. In contrast, in cytokine-dependent cell lines, cytokines mediate phosphorylation of Bcl-2 on S70, preventing apoptosis. As discussed in this review, these models are not mutually exclusive but reflect different cellular contexts. During mitotic arrest, signal transduction is unique and is fundamentally different from classical mitogenic signaling, since the nucleus membrane is dissolved, gene expression is reduced, and numerous kinases and regulatory proteins are hyperphosphorylated. Hyperphosphorylation of Bcl-2 mediated by paclitaxel and other microtubuleactive drugs is strictly dependent on targeting microtubules that in turn cause mitotic arrest. In addition to serine-70 (S70), microtubule-active agents promote phosphorylation of S87 and threonine-69 (T69), inactivating Bcl-2. A major obstacle for identification of the mitotic Bcl-2 kinase(s) is that inhibition of putative kinase(s) by any means (dominant-negative mutants, antisense oligonucleotides, pharmacological agents) may arrest cycle, preventing mitosis and Bcl-2 phosphorylation. The role of Bcl-2 phosphorylation in cell death is discussed. Leukemia (2001) 15, 869-874.

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