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Updated: May 1, 2026

Assessing Cellular Target Engagement by SHP2 PTPN11 Phosphatase Inhibitors
Published on: July 17, 2020
PTP1B inhibition causes Rac1 activation by enhancing receptor tyrosine kinase signaling
Ayako Tsuchiya1, Takeshi Kanno, Hisao Nagaya
1Division of Bioinformation, Department of Physiology, Hyogo College of Medicine, Nishinomiya, Japan.
Background/Aims:
The present study investigated the signaling pathway underlying Rac1 activation induced by the linoleic acid derivative 8-[2-(2-pentyl-cyclopropylmethyl)-cyclopropyl]-octanoic acid (DCP-LA).
Methods:
Activity of protein tyrosine phosphatase 1B (PTP1B) was assayed under cell-free conditions. Western blot was carried out to quantify phosphorylation of insulin receptor substrate-1 (IRS-1) and Akt in PC-12 cells. Rac1 activity was monitored in the föerster resonance energy transfer (FRET) analysis using living and fixed PC-12 cells.
Results:
DCP-LA markedly suppressed PTP1B activity in a concentration (100 pM-100 µM)-dependent manner. In the DCP-LA binding assay, fluorescein-conjugated DCP-LA produced a single fluorescent signal band at 60 kDa, corresponding to the molecule of PTP1B, and the signal was attenuated or abolished by co-treatment or pretreatment with non-conjugated DCP-LA. DCP-LA significantly enhanced nerve growth factor (NGF)-stimulated phosphorylation of IRS-1 at Tyr1222 and Akt1/2 at Thr308/309 and Ser473/474 in PC-12 cells. In the FRET analysis, DCP-LA significantly enhanced NGF-stimulated Rac1 activation, which is abrogated by the phosphatidylinositol 3 kinase (PI3K) inhibitor wortmannin, the 3-phosphoinositide-dependent protein kinase-1 (PDK1) inhibitor BX912, or the Akt inhibitor MK2206.
Conclusion:
The results of the present study show that DCP-LA-induced PTP1B inhibition, possibly through its direct binding, causes Rac1 activation by enhancing a pathway along a receptor tyrosine kinase (RTK)/IRS-1/PI3K/Akt/Rac1 axis.
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