Life support: the alpha4 phosphatase subunit in cell survival and apoptosis.

Reversible protein phosphorylation represents a cellular response to normal physiological processes as well as to cellular insults and stress. Recently, the protein phosphatase-associated alpha4 subunit was shown to be required for sustaining cell survival. Lack of alpha4 leads to apoptotic death of multiple cell types and to the death of the organism. Here, we explore how the phosphatase network might operate in controlling life-and-death decisions. We discuss the relevance of the findings for understanding the action of alpha4 in cell survival and for better discriminating between a role in maintaining cellular homeostasis, and thus survival, or actively keeping apoptotic cell death in check by targeting effectors of the cell death machinery.