Expression of PRL-1 nuclear PTPase is associated with proliferation in liver but with differentiation in intestine
Diamond, R.H.; Peters, C.; Jung, S.P.; Greenbaum, L.E.; Haber, B.A.; Silberg, D.G.; Traber, P.G.; Taub, R.
American Journal of Physiology 271(1 Pt 1): G121-G129
1996
ISSN/ISBN: 0002-9513 PMID: 8760115 Document Number: 458430
Mechanisms controlling the tyrosine phosphorylation of cellular proteins are important in the regulation of cellular processes including growth and differentiation. It has become clear that a number of protein tyrosine phosphatases (PTPases) that dephosphorylate tyrosyl residues may play a role in the growth response, both in growth-promoting and growth-inhibiting capacities. We identified PRL-1, a unique nuclear PTPase that is an immediate-early gene in liver regeneration and is positively associated with growth, including fetal and neoplastic hepatic growth and anchorage-independent growth after overexpression in fibroblasts. In this study, we show that PRL-1 nuclear protein levels in regenerating liver parallel those of its mRNA, although the peak occurs later, just before the onset of DNA synthesis. We further show that PRL-1 is significantly expressed in intestinal epithelia and that, in contrast to the expression pattern of PRL-1 in liver, its expression is associated with cellular differentiation in intestine. Specifically, PRL-1 is expressed in villus but not crypt enterocytes and in confluent differentiated but not undifferentiated proliferating Caco-2 colon carcinoma cells. The expression of PRL-1 in intestine shows inverse correlation with proliferating cell nuclear antigen expression, a marker for S-phase cells. These results suggest that PRL-1 may play different roles in these two digestive tissues. Such a dichotomy of roles has previously been described for some protein tyrosine kinases and might be due to the availability of alternate substrates in different tissues.