RAPID MITOGEN-INDUCED AMINOPEPTIDASE-N SURFACE EXPRESSION IN HUMAN T-CELLS IS DOMINATED BY MECHANISMS INDEPENDENT OF DE-NOVO PROTEIN-BIOSYNTHESIS

The membrane bound metalloprotease aminopeptidase N (APN, CD13, EC 3.4 .11.2) is a well established marker of normal and malignant cells of t he myelo-monocytic lineage. It is also expressed by leukaemic blasts o f a small group of patients suffering from acute or chronic lymphoid l eukaemia. Recently the expression of the APN gene in T cell lines as w ell as the induction of APN gene and surface expression in human perip heral T cells by mitogenic activation have been demonstrated. Here, hy means of cytofluorimetric analysis evidence is provided, that the ind uction of APN surface expression is partially resistent to the action of the inhibitors of protein biosynthesis, puromycin and cycloheximide , and is not prevented by tunicamycin, an inhibitor of glycosylation. These data suggest that the rapid mitogen-induced surface expression o f APN, detectable 20 hours after stimulation is dominated by mechanism s not dependent on de novo protein biosynthesis or glycosylation. As s hown by simultaneous analyses, the inhibitors used did also differentl y modify the induction of surface expression of other inducible glycos ylated leukocyte surface antigens, namely CD25, CD69 and CD95.