title: PTP1B inhibition causes Rac1 activation by enhancing receptor tyrosine kinase signaling.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Division of Bioinformation, Department of Physiology, Hyogo College of Medicine, Nishinomiya, Japan.
authors.forename: Ayako
authors.initials: A
authors.lastname: Tsuchiya
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kanno
authors.forename: Hisao
authors.initials: H
authors.lastname: Nagaya
authors.forename: Tadashi
authors.initials: T
authors.lastname: Shimizu
authors.forename: Akito
authors.initials: A
authors.lastname: Tanaka
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Nishizaki
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002210:Caprylates / Q000737:chemistry / Q000494:pharmacology; D019793:Fluorescein / Q000737:chemistry; D031541:Fluorescence Resonance Energy Transfer; D006575:Heterocyclic Compounds, 3-Ring / Q000494:pharmacology; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D020932:Nerve Growth Factor / Q000494:pharmacology; D016716:PC12 Cells; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D051381:Rats; D020917:Receptor, trkA / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D000077191:Wortmannin; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000730:Androstadienes; D002210:Caprylates; D019793:Fluorescein; D006575:Heterocyclic Compounds, 3-Ring; D055504:Insulin Receptor Substrate Proteins; D020932:Nerve Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D051057:Proto-Oncogene Proteins c-akt; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D020917:Receptor, trkA; D000077191:Wortmannin; D020830:rac1 GTP-Binding Protein; C506022:8-(2-(2-pentyl-cyclopropylmethyl)cyclopropyl)octanoic acid; C548887:MK 2206; C000631434:Pdk1 protein, rat