Reversible protein phosphorylation represents a cellular response to normal physiological processes as well as to cellular insults and stress.
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.
References
Saleh M, Pagliari LJ, Green DR. Life support: the alpha4 phosphatase subunit in cell survival and apoptosis. Trends Cell Biol. 2005 Jun;15(6):285-7. PMID: 15953545