PRL-1 PTPase expression is developmentally regulated with tissue-specific patterns in epithelial tissues

The mechanisms controlling tyrosine phosphorylation of cellular proteins ar e important in the regulation of many cellular processes, including develop ment and differentiation. Protein tyrosine phosphatases (PTPases) may be as important as protein tyrosine kinases (PTKs) in these processes. PRL-1 is a distinct PTPase originally identified as an immediate-early gene in liver regeneration whose expression is associated with growth in some tissues bu t with differentiation in others. We now demonstrate that the PRL-1 protein is expressed during development in a number of digestive epithelial tissue s. It is expressed at variable time points in the developing intestine, but its expression is limited to the developing villus enterocytes. In the gas tric epithelium, PRL-1 expression in the adult is restricted to zymogen cel ls. PRL-1 is also expressed in the developing liver and esophagus and in th e epithelia of the kidney and lung. In each of these contexts, the expressi on of PRL-1 is associated with terminal differentiation, suggesting that it may play a role in this important developmental process.