Cell surface ADP-ribosyltransferase regulates lymphocyte function-associated molecule-1 (LFA-1) function in T cells.
Post-translational modifications are important in regulating the functions of signal proteins. This is well established for intracellular proteins, but little is known in the case of extracellular domains of cell surface molecules. We recently described a cell surface protein, mono-ADP-ribosyltransferase (ADPRT), on cytotoxic T cells and showed that it mediates attachment of ADP-ribose to cell surface proteins. Concomitantly, cytolytic activity and cell proliferation are inhibited. Here we report that one of the principal proteins modified by this enzyme is lymphocyte function-associated molecule-1 (LFA-1). While both chains are ADP-ribosylated on the extracellular domain of the molecule, persistence of the modification differs between the chains. Label is released from the beta-chain by 1 h, yet remains for at least 6 h on the alpha-chain. Loss of label is suppressed by phosphodiesterase inhibitors such as ADP-ribose and p-nitrophenylthymidine 5'-monophosphate, pointing to the involvement of this class of enzyme. Modification of LFA-1 requires expression of the cell surface ADPRT and causes the loss of epitopes recognized by alpha- and beta-chain-specific Abs. Concomitantly, the generation of inositol phosphates induced by Ab cross-linking of LFA-1 is significantly inhibited. Consistent with this effect, anti-LFA-1-induced homotypic cell adhesion is also inhibited. These effects are not seen in cells from which the ADPRT was removed by phospholipase C. Moreover, cells lacking the cell surface ADPRT are not inhibited by NAD in the cell adhesion assay, but gain this property upon transfection with the ADPRT gene. It is concluded that the cell surface protein mono-ADPRT regulates LFA-1 functions.
Nemoto
E
E
Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, University of Southern California School of Medicine, Los Angeles 90033, USA.
Yu
Y
Y
Dennert
G
G
D036002:ADP Ribose Transferases; D000818:Animals; D000906:Antibodies; D001120:Arginine / Q000737:chemistry; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D000939:Epitopes / Q000737:chemistry / Q000378:metabolism; D006825:Hybridomas; D066298:In Vitro Techniques; D016169:Lymphocyte Function-Associated Antigen-1 / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009243:NAD / Q000378:metabolism / Q000494:pharmacology; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D015398:Signal Transduction / Q000187:drug effects; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology*; D014162:Transfection
D000906:Antibodies; D000939:Epitopes; D016169:Lymphocyte Function-Associated Antigen-1; D008565:Membrane Proteins; D009243:NAD; D001120:Arginine; D036002:ADP Ribose Transferases; D011065:Poly(ADP-ribose) Polymerases; D010727:Phosphoric Diester Hydrolases