TISSUE-SPECIFIC EXPRESSION AND CELLULAR LOCALIZATION OF GLYCOSYLPHOSPHATIDYLINOSITOL-ANCHORED NAD:ARGININE ADP-RIBOSYLTRANSFERASE.

Mono ADP-ribosyltransferases (ADPRT) transfer the ADP-ribose moiety O fNAD to acceptor proteins. A glycosylphosphatidylinositol(GPI)- anchored ADPRT, originalyisolated from rabbit skeletal muscle, is conserved across species as evidenced on immunoblots where antibodies against rabbit skeletal muscle transferase reacted with partially purified ADPRT from canine,bovine and humanskeletal muscle. On Northern analysis, the skeletalmuscle ADPRTcDNA hybridized with a 1.6-kb band, strongly with mouse cardiac and skeletal muscle poly(A)+RNA and weakly with a 1.6-kb band from lung and lymphocyte mRNA. ADPRT activity was detected in human cells obtained by bronchoalveolarlavage (BAL).On immunoblots, a 40-kDa protein, reactive with anti-ADPRT antibodies, bound [32P]-NAD in an overlay assay. On immunohistochemical staining and confocal microscopic study of lung tisue, the epithelial layer was strongly reactive, with the immunoreactivity localized on the surface of intermediate bronchial epithelial cells and on the apical surface of ciliated cells, consistent with previous observations that GPI-linked proteins are targeted to the apical surface of polarized cells. Immunoreactivity was reduced by incubation of cells with phosphatidylinositol (PI)-specific phospholipase C, which releases the protein from the PI anchor. These data are consistent with the hypothesis that a GPI-anchored ADPRT, in addition to be found in muscle and lymphocytes, is a constituent of pulmonary epithelial cell membranes.