Liver-specific protein-tyrosine phosphatase 1B (PTP1B) re-expression alters glucose Homeostasis of PTP1B-/- mice

Protein-tyrosine phosphatase 1B (PTP1B) is an important negative regulator of insulin and leptin signaling in vivo. Mice lacking PTP1B ( PTP1B -/- mice) are hyperresponsive to insulin and leptin and resistant to diet-induced obesity. The tissue(s) that mediate these effects of global PTP1B deficiency remain controversial. We exploited the high degree of hepatotropism of adenoviruses to assess the role of PTP1B in the liver. Liver-specific re-expression of PTP1B in PTP1B -/- mice led to marked attenuation of their enhanced insulin sensitivity. This correlated with, and was probably caused by, decreased insulin-stimulated tyrosyl phosphorylation of the insulin receptor (IR) and IR substrate 2-associated phosphatidylinositide 3-kinase activity. Analysis using phospho-specific antibodies for the IR revealed preferential dephosphorylation of Tyr-1162/1163 compared with Tyr-972 by PTP1B in vivo. Our findings show that the liver is a major site of the peripheral action of PTP1B in regulating glucose homeostasis.