Inhibition of glycosylphosphatidylinositol (GPI) phospholipase D by suramin-like compounds

A number of proteins are found attached to the plasma membrane of mammalian cells by a glycosylphosphatidylinositol (GPI) anchor that can be cleaved by GPI specific phospholipase D (GPI-PLD). There are no known specific inhibitors of GPI-PLD. We examined some inhibitors of phosphatidylinositol specific phospholipase C (PI-PLC) for their ability to inhibit human serum and human bone marrow cell GPI-PLD. Azo analogues of suramin were found to be potent inhibitors of GPI-PLD. One compound had art IC50 of 3.7 mu M that was 10-fold lower than the IC50 required to inhibit PI-PLC. The azo suramin analogues inhibited cancer cell growth at concentrations similar to those required to inhibit GPI-PLD, and below concentrations required to inhibit growth factor binding. It is possible that inhibition of cell growth might be related to the ability of the compounds to inhibit GPI-PLD.