Protein-tyrosine Phosphatase-1B (PTP1B) Mediates the Anti-migratory Actions of Sprouty

Abstract

Mammalian Sprouty proteins have been shown to inhibit the proliferation and migration of cells in response to growth factors and serum. In this communication, using HeLa cells, we have examined the possibility that human Sprouty 2 (hSPRY2) mediates its anti-migratory actions by modulating the activity or intracellular localization of protein-tyrosine phosphatases. In HeLa cells, overexpression of hSPRY2 resulted in an increase in protein-tyrosine phosphatase (PTP1B) amount and activity in the soluble (100,000 x g) fraction of cells without an increase in total amount of cellular PTP1B. This increase in the soluble form of PTP1B was accompanied by a decrease in the amount of the enzyme in the particulate fraction. The amounts of PTP-PEST or PTP1D in the soluble fractions were not altered. Consistent with an increase in soluble PTP1B amount and activity, the tyrosine phosphorylation of cellular proteins and p130(Cas) was decreased in hSPRY2-expressing cells. In control cells, overexpression of wild-type (WT) PTP1B, but not its C215S catalytically inactive mutant mimicked the actions of hSPRY2 on tyrosine phosphorylation of cellular proteins and migration. On the other hand, in hSPRY2-expressing cells, the C215S mutant, but not WT PTP1B, increased tyrosine phosphorylation of cellular proteins and attenuated the anti-migratory actions of hSPRY2. Interestingly, neither WT nor C215S mutant forms of PTP1B modulated the anti-mitogenic actions of hSPRY2. Therefore, we conclude that an increase in soluble PTP1B activity contributes to the anti-migratory, but not anti-mitogenic, actions of hSPRY2.