Protein tyrosine phosphatase 1B (PTP1B) is a protein tyrosine phosphat
ase of unknown function, although increasing evidence supports a role
for this phosphatase in insulin action, We have investigated the inter
action of PTP1B with the insulin receptor using a PTP1B glutathione S-
transferase (GST) fusion protein with a point mutation in the enzyme's
catalytic domain, This fusion protein is catalytically inactive, but
the phosphatase's phosphotyrosine binding site is maintained, The acti
vated insulin receptor was precipitated from purified receptor prepara
tions and whole-cell lysates by the inactive PTP1B-GST, demonstrating
a direct association between the insulin receptor and PTP1B. A p120 of
unknown identity was also precipitated from whole-cell lysates by the
PTP1B fusion protein, but IRS-1 (pp185) was not, A catalytically inac
tive [S-35]PTP1B-fusion protein bound directly to immobilized insulin
receptor kinase domains and was displaced in a concentration-dependent
manner, Finally, tyrosine-phosphorylated PTP1B was precipitated from
whole-cell lysates by an anti-insulin receptor antibody after insulin
stimulation, The site of interaction between PTP1B and the insulin rec
eptor was studied using phosphopeptides modeled after the receptor's k
inase domain, the NPXY domain, and the COOH-terminal. Each phosphopept
ide inhibited the PTP1B-GST:insulin receptor interaction, Study of mut
ant insulin receptors demonstrated that activation of the kinase domai
n is necessary for the PTP1B:insulin receptor interaction, but recepto
rs with deletion of the NPXY domain or of the COOH-terminal can still
bind to the PTP1B-GST. We conclude that PTP1B can associate directly w
ith the activated insulin receptor at multiple different phosphotyrosi
ne sites and that dephosphorylation by PTP1B may play a significant ro
le in insulin receptor signal transduction.