Signalling properties of glycosylphosphatidylinositols and their regulated release from membranes in the turnover of glycosylphosphatidylinositol-anchored proteins.

Glycosylphosphatidylinositols are involved in transmembrane signalling, and their signal mediated release from the cell membrane has been demonstrated for several hormones and growth factors. Presently, however, only indirect evidence exists for the enzyme responsible for the signal mediated release of glycosylphosphatidylinositols. Indirect evidence from product identification led to the conclusion that in mammals the hormone sensitive activity is that of a glycosylphosphatidylinositol anchor hydrolyzing phospholipase C. On the other hand a mammalian glycosylphosphatidylinositol anchor hydrolyzing phospholipase D is well-established. This enzyme most likely functions in the intracellular turnover of glycosylphosphatidylinositols, however, its possible relation to the signalling properties of glycosylphosphatidylinositols remains unclear.