The Dopamine/D1 Receptor Mediates the Phosphorylation and Inactivation of the Protein Tyrosine Phosphatase STEP via a PKA-Dependent Pathway

The aim of the present study was to identify the signaling mechanism(s) responsible for the modulation of growth hormone secretagogue receptor type 1a (GHSR1a)-associated Akt activity. Ghrelin leads to the activation of Akt through the interplay of distinct signaling mechanisms: an early Gi/o protein-dependent pathway and a late pathway mediated by β-arrestins. We found that the Src homology 2–containing protein tyrosine phosphatase (SHP-1) was an essential molecule in both Gi/o protein–dependent and β-arrestin–mediated pathways. More specifically, the role of SHP-1 in the Gi/o protein–dependent pathway was demonstrated by the fact that the overexpression of a catalytically defective SHP-1 augments tyrosine phosphorylation of the PI3K regulatory subunit p85, leading to an increase in the phosphorylation of cSrc and phosphoinositide-dependent protein kinase 1, and finally activating Akt. The presence of SHP-1 in the β-arrestin–scaffolded complex and its attenuating effect on the cSrc and Akt activities verified that SHP-1 regulates not only the Gi/o protein–dependent pathway but also the β-arrestin–mediated pathway. Assays performed in preadipocyte and adipocyte 3T3-L1 cells showed SHP-1 expression. According to our results in HEK-GHSR1a cells, ghrelin stimulated SHP-1 phosphorylation in 3T3-L1 cells. The increase in ghrelin-induced Akt activity was enhanced by small interfering RNA of SHP-1 in preadipocyte 3T3-L1 cells. These results were reproduced in white adipose tissue obtained from mice, in which SHP-1 exhibited higher expression in omental than in subcutaneous tissue. Furthermore, this pattern of expression was inverted in mice fed a high-fat diet, suggesting a role for SHP-1 in controlling ghrelin sensitivity in adipose tissue. Indeed, SHP-1 deficiency was associated with augmented ghrelin-evoked Akt phosphorylation in omental tissue, as well as decreased phosphorylation under overexpression of SHP-1 in subcutaneous tissue. These findings showed a novel role for SHP-1 in the regulation of Akt activity through the modulation of the ghrelin/GHSR1a system signaling.

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Discovery of novel protein tyrosine phosphatase 1B inhibitors from medicinal plant resources

Planta Medica ◽

10.1055/s-0036-1596581 ◽

2016 ◽

Vol 81 (S 01) ◽

pp. S1-S381

Author(s):

W Li ◽

T Sasaki ◽

T Onoda ◽

K Higai ◽

K Koike

Keyword(s):

Medicinal Plant ◽

Protein Tyrosine Phosphatase ◽

Tyrosine Phosphatase ◽

Protein Tyrosine Phosphatase 1B ◽

Plant Resources ◽

Protein Tyrosine ◽

Novel Protein

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1742-P: Targeting the Low Molecular Weight Protein Tyrosine Phosphatase for Obesity-Associated Diabetes Therapy

Diabetes ◽

10.2337/db20-1742-p ◽

2020 ◽

Vol 69 (Supplement 1) ◽

pp. 1742-P

Author(s):

STEPHANIE M. STANFORD ◽

MICHAEL A. DIAZ ◽

JIWEN J. ZOU ◽

ROBERT J. ARDECKY ◽

ANTHONY PINKERTON ◽

...

Keyword(s):

Molecular Weight ◽

Protein Tyrosine Phosphatase ◽

Tyrosine Phosphatase ◽

Low Molecular Weight ◽

Molecular Weight Protein ◽

Diabetes Therapy ◽

Protein Tyrosine ◽

Weight Protein ◽

Low Molecular Weight Protein

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Inhibition of Protein Tyrosine Phosphatase 1B by Lutein Derivatives isolated from Mexican Oregano (Lippia graveolens)

Phytothérapie ◽

10.3166/phyto-2018-0074 ◽

2018 ◽

Vol 17 (3) ◽

pp. 134-139

Author(s):

R.M. Perez-Gutierrez

Keyword(s):

Protein Tyrosine Phosphatase ◽

Inhibitory Activity ◽

Spectroscopic Data ◽

Methanol Extract ◽

Tyrosine Phosphatase ◽

Positive Control ◽

Protein Tyrosine Phosphatase 1B ◽

Protein Tyrosine ◽

Ic50 Value ◽

Ic50 Values

Methanol extract from Lippia graveolens (Mexican oregano) was studied in order to identify inhibitory bioactives for protein tyrosine phosphatase 1B (PTP1B). Known flavone as lutein (1), and another flavone glycoside such as lutein-7-o-glucoside (2), 6-hydroxy-lutein-7-ohexoside (3) and lutein-7-o-ramnoide (4) were isolated from methanol extract of aerial parts of the Lippia graveolens. All isolates were identified based on extensive spectroscopic data analysis, including UV, IR, NMR, MS and compared with spectroscopic data previously reported. These flavones were evaluated for PTP1B inhibitory activity. Among them, compounds 1 and 3 displayed potential inhibitory activity against PTP1B with IC50 values of 7.01 ± 1.25 μg/ml and 18.4 μg/ml, respectively. In addition, compound 2 and 4 showed moderate inhibitory activity with an IC50 value of 23.8 ± 6.21 and 67.8 ± 5.80 μg/ml respectively. Among the four compounds, luteolin was found to be the most potent PTP1B inhibitor compared to the positive control ursolic acid, with an IC50 value of 8.12 ± 1.06 μg/ml. These results indicate that flavonoids constituents contained in Lippia graveolens can be considered as a natural source for the treatment of type 2 diabetes.

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