HEPATIC TYROSINE-PHOSPHORYLATED PROTEINS IDENTIFIED AND LOCALIZED FOLLOWING IN-VIVO INHIBITION OF PROTEIN-TYROSINE PHOSPHATASES - EFFECTS OF H2O2 AND VANADATE ADMINISTRATION INTO RAT LIVERS
Yr. Hadari et al., HEPATIC TYROSINE-PHOSPHORYLATED PROTEINS IDENTIFIED AND LOCALIZED FOLLOWING IN-VIVO INHIBITION OF PROTEIN-TYROSINE PHOSPHATASES - EFFECTS OF H2O2 AND VANADATE ADMINISTRATION INTO RAT LIVERS, Molecular and cellular endocrinology, 97(1-2), 1993, pp. 9-17
Injection of a combination of H2O2 and vanadate (H/V) into the portal
vein of rat livers resulted in inhibition of protein tyrosine phosphat
ase activity and led to a dramatic enhanced in vivo protein tyrosine p
hosphorylation. Some of the phosphorylated proteins were identified as
the beta-subunit of the insulin receptor, the insulin receptor substr
ate 1 (pp185), PLC-gamma (pp145), and a 100 kDa PLC-gamma-associated p
rotein. Immunofluorescense and immune electron microscopy of frozen li
ver sections with anti-P-Tyr antibodies revealed that most of the tyro
sine-phosphorylated proteins are localized in close proximity to the p
lasma membrane in intercellular adherence junctions and tight junction
regions. This close in vivo association between membranal protein tyr
osine kinases, their target proteins, and cytoskeletal elements could
enable formation of 'signaling complexes' which may play a role in tra
nsmembrane signal transduction. By affinity chromatography over immobi
lized anti-P-Tyr antibodies, a large number of these tyrosine-phosphor
ylated proteins were partially purified.