A rapid method for the identification of ceramide activated protein phosphatase

Recently, the sphingomyelin cycle has emerged as a key mechanism implicated in apoptosis, cell growth, differentiation, and cellular stress. This pathway is activated following Hgand binding of receptors and subsequent activation of a neutral cytosolic sphingomyelinase, which in turn, hydrolyzes sphingomyelin to generate ceramide and phosphorylcholin. The novel second messenger, ce ramide, once generated, acts through a ceramide activated protein phosphatase (CAPP) to elicit its downstream effects. Although, CAPP is a prime candidate for mediating ceramide signaling in mammalian cells, its identity and its connection to the downstream targets of ceramide activation remain elusive. Molecular characterization of CAPP is, therefore, a prelude to a better understanding of the mechanism by which ceramide causes its downstream effects. In this study we report a novel method for the separation and identification of CAPP. We have used a combination of ionexchange chromatography, hydrophobic inter action, and immunological methods, for the purification and identification of ('APP. Our studies demonstrate that CAPP consists of multimeric forms of protein phosphatase 2A (PP2A).