GLYCOSYLPHOSPHATIDYLINOSITOL-SPECIFIC PHOSPHOLIPASE-D IS LOCALIZED INKERATINOCYTES

Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is abu ndant in mammalian plasma, but little is known of its cellular and tis sue distribution. In this study frozen sections of perfused tissues fr om adult rats were stained with monoclonal antibodies against GPI-PLD. The most intense staining was observed in the stratified squamous epi thelium of the forestomach. Staining was also observed in the esophagu s, the tongue, the hard palate, and the skin but not in most other tis sues including the columnar epithelium of the stomach or the lower gas trointestinal tract. GPI-PLD expression was also detected in several k eratinocyte cell lines. Biochemical assays of glycosylphosphatidylinos itol-degrading activity using [H-3]myristate-labeled variant surface g lycoprotein as substrate provided independent evidence for the presenc e of GPI-PLD. Expression of GPI-PLD by keratinocytes was not affected by culture in serum-free media, indicating that it does not originate by uptake of serum GPI-PLD in the media. These data suggest that kerat inocytes are an important site of action of GPI-PLD and possibly a con tributor to the plasma GPI-PLD pool.