PTP1B Inhibitors Research Articles

Abstract PO018: Restoring the tumor-suppressed immune response during chemotherapy by targeting Mer:PTP1b interactions

Abstract The development of adaptive immune checkpoint inhibitors, which prevent tumor-mediated inactivation of lymphocytes, has drastically improved outcomes for advanced cancer patients. However, only 20-30% of patients benefit from these treatments and those that do often present moderate toxicity and/or later relapse. After discovering a novel innate immune checkpoint, we have identified a therapeutic strategy to restore the tumor-suppressed immune response during chemotherapy. Here, we show that multiple tumor types (including melanoma, lung, breast and pancreatic cancers) co-cultured with murine primary macrophages suppress the expression of the essential Toll-like Receptor (TLR) signal-transducing adapter protein MyD88 by 57-81% +/- 2-5% (mean +/- SEM). In the absence of MyD88, macrophages are unable to respond to TLR stimulating Damage Associated Molecular Patterns (DAMPs) released by dying tumor cells after chemotherapy, leading to as much as 97% +/- 6% reduction in pro-inflammatory gene expression in our co-culture models. Tumors exert this suppression by activating the macrophage Mer receptor, inducing recruitment of a phosphatase, known as PTP1b, and Stat1 to Mer. Increasing association between PTP1b and Stat1 leads to reduced Stat1 phosphorylation and translocation to the nucleus as well as a downstream reduction in MyD88 expression. Treatment with a pharmacological inhibitor of PTP1b (BVT948) blocks the association of Mer, PTP1b and Stat1, restoring MyD88 expression and responsiveness to chemotherapy-released DAMPs. In chemotherapy-resistant murine syngeneic melanoma models, including B16F10 and GEMM6 (Braf V600E, Pten-/-), we show that combination therapy with BVT948 and Cisplatin or Vemurafenib, respectively, leads to a 47% reduction in tumor growth rates. Treating chemo- and immuno-therapy resistant Lewis Lung Cancer (LLC) tumor-bearing mice with combination BVT948/Cisplatin therapy leads to a similar reduction in tumor growth that is magnified with the addition of adaptive immune checkpoint blockade. In summary, we have described a novel mechanism of cancer-mediated immune suppression that dramatically reduces the immune response during chemotherapy. PTP1b inhibition could represent a novel therapeutic strategy to improve the effectiveness of conventional chemotherapy in patients with advanced malignancies. Citation Format: Nestor Prieto-Dominguez, Eric S. Ubil. Restoring the tumor-suppressed immune response during chemotherapy by targeting Mer:PTP1b interactions [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO018.

Diarylheptanoid-chalcone hybrids with PTP1B and α-glucosidase dual inhibition from Alpinia katsumadai

The EtOH extracts of the dried seeds of Alpinia katsumadai were revealed with hypoglycemic effects on db/db mice at the concentration of 200 mg/kg. In order to clarify the antidiabetic constituents, 16 new diarylheptanoid-chalcone hybrids, katsumadainols A1−A16 (1–16), together with 13 known analogues (17–29), were isolated from A. katsumadai under the guidance of bioassay. Most of the compounds showed α-glucosidase and PTP1B dual inhibition, among which compounds 1–3, 5–7, 11–14, 21–25, and 27 showed PTP1B/TCPTP selective inhibition with IC50 values ranging from 22.0 to 96.7 μM, which were 2–10 times more active than sodium orthovanadate (IC50, 215.7 μM). All compounds exhibited obvious inhibition against α-glucosidase with IC50 values of 2.9–29.5 μM, indicating 6–59 times more active than acarbose (IC50, 170.9 μM). Study of enzyme kinetics indicated compounds 1, 3, and 12 were PTP1B and α-glucosidase mixed-type inhibitors with Ki values of 13.1, 12.9, 21.6 μM, and 4.9, 7.4, 3.4 μM, respectively.

Fungal metabolites as anti-diabetic agents: emphasis on PTP1B inhibitors

In the last decade the prevalence of diabetes has escalated globally and it is estimated that the number of diabetic people will increase to 642 million by 2040. Although numerous classes of pharmaceutical drugs are available to treat Type ll diabetes, they manifest certain side effects. PTP1B has attracted significant interest as an important therapeutic agent and has been validated to target diabetes and obesity. Fungi, in general, produce secondary metabolites with some amazing chemical and structural diversity and are recognized to be a valuable source for therapeutic molecules. In this review, the focus is on describing the PTP1B effects and their potential as anti-diabetic agents for the various metabolites isolated from fungi.

Deciphering the interactions of compounds from Allium sativum targeted towards identification of novel PTP 1B inhibitors in diabetes treatment: A computational approach

Diabetes has increased radically in recent decades globally. Diabetes mainly emerged as a major health care problem in the world, among which type-2 diabetes is the most common. Protein tyrosine phosphatase 1B (PTP1B) is an important target for treating type-2 diabetes. Discovering new and effective treatment options for type-2 diabetes is currently of high international health importance. It is therefore expedient to identify the bioactive compounds of plants with inhibitory activity against PTP1B for designing drugs against type-2 diabetes. In the present study, a computational technique was used to identify bioactive compounds isolated from Allium sativum with PTP-1B inhibitory activity. A molecular docking study was achieved utilizing the Glide-Ligand Docking panel of Maestro 12.5 with Schrödinger Suite 2020-3. The binding free energy of the receptor-ligand complex was calculated using the MM-GBSA Prime panel. Pharmacophore models were generated using the PHASE module and the absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties of the compounds were assessed using SwissADME and PROTOX-II servers. The top three compounds are kaempferol, apigenin, and guanosine; with a binding affinity of −7.597, −7.263, and −6.655 kcal/mol compared with −7.155 kcal/mol demonstrated by the standard ligand. These lead compounds, like the standard ligand interacted with important amino acid residues like PHE 280, ASN 193, and GLU 276. The ADMET prediction revealed possible oral bioavailability and safety for kaempferol and apigenin. Hence, the results demonstrated that compounds from A. sativum could inhibit PTP1B and could be considered for experimental studies and the development of drugs against type-2 diabetes.

Oligomeric phenylpropanoids having new skeletons and hypoglycemic activity from Magnolia officinalis var. biloba

Three oligomeric phenylpropanoids [(+)/(–)-1 and 2] with new skeletons and a meroterpenoid (3) from Magnolia officinalis var. biloba were identified. Pharmacological studies showed(+)-1 and (–)-1 are PTP1B and α-glucosidase dual inhibitors.

Synthesis of 2-ethoxycarbonylthieno[2,3-b]quinolines in biomass-derived solvent γ-valerolactone and their biological evaluation against protein tyrosine phosphatase 1B.

A series of 2-ethoxycarbonylthieno[2,3-b]quinolines were synthesized in the bio-derived “green” solvent γ-valerolactone (GVL) and evaluated for their inhibitory activities against PTP1B, the representative compound 6a displayed an IC50 value of 8.04 ± 0.71 μM with 4.34-fold preference over TCPTP. These results provided novel lead compounds for the design of inhibitors of PTP1B as well as other PTPs.

Isolation and Structure Determination of PTP1B Inhibitor from Streptomyces sp. Strain TD-X10

In the course of bioassay-guided study for natural antidiabetic compounds from microorganisms, two steroids, i.e. compounds 1 and 2, were isolated in vitro from biomass of antidiabetic Streptomyces sp. strain TD-X10. Structures of the compounds 1 and 2 were elucidated on the basis of spectroscopic analysis of nuclear magnetic resonance and mass spectral data and comparison with reported literature data as β-sitosterol and β-sitosteryl ferulate, respectively. While compound 1 exhibited faintly inhibitory activity against protein tyrosine phosphatase 1B, a highly validated therapeutic target for diabetes mellitus, compound 2 displayed a moderate inhibitory effect to the enzyme with IC50 value of 40.05 ± 2.46 µM. The results highlight the antidiabetic potential of natural products from actinobacteria, particularly Streptomyces species.

Integration of in silico, in vitro and ex vivo pharmacology to decode the anti-diabetic action of Ficus benghalensis L. bark.

Traditionally,Ficus benghalensis L. is used to treat metabolic disorders and is also recorded in the Ayurvedic pharmacopeia of India. The present study aimed to evaluate the anti-diabetic property of hydroalcoholic extract/fraction(s) of F. benghalensisL. bark via in silico, in vitro, and ex vivo approach. Enzyme inhibitory activity, glucose uptake in rat hemidiaphragm, andglucose permeability, and adsorption assays were performed using in vitro and ex vivo methods as applicable. Further, the PASS was used to identify the probable lead enzyme inhibitors. The presence of predicted enzyme inhibitors was confirmed via the LC-MS. Similarly, the docking of ligands with respective targets was performed using autodock4.0. Flavonoids rich fraction possessed the highest α-amylase, and α-glucosidase inhibitory activity followed by maximum efficacy for glucose uptake in rat hemidiaphragm. Similarly, the hydroalcoholic extract showed the highest efficacy to inhibit glucose diffusion. Likewise, 3,4-dihydroxybenzoic acid was predicted for the highest pharmacological activity for α-amylase, ursolic acid for PTP1B, and apigenin for α-glucosidase inhibition respectively. The LC-MS analysis also identified the presence of the above hit molecules in the hydroalcoholic extract. The analogs of 3,4-dihydroxybenzoic acid, apigenin, and ursolic acid could be the choice of lead hits as the α-amylase, α-glucosidase, and PTP1B inhibitors respectively. Additionally, the majority of secondary metabolites from the hydroalcoholic extract of F. benghalensis may be involved in enhancing the glucose uptake to support the process of glycogenesis.

The overexpression of TDP-43 in astrocytes causes neurodegeneration via a PTP1B-mediated inflammatory response

BackgroundCytoplasmic inclusions of transactive response DNA binding protein of 43 kDa (TDP-43) in neurons and astrocytes are a feature of some neurodegenerative diseases, such as frontotemporal lobar degeneration with TDP-43 (FTLD-TDP) and amyotrophic lateral sclerosis (ALS). However, the role of TDP-43 in astrocyte pathology remains largely unknown.MethodsTo investigate whether TDP-43 overexpression in primary astrocytes could induce inflammation, we transfected primary astrocytes with plasmids encoding Gfp or TDP-43-Gfp. The inflammatory response and upregulation of PTP1B in transfected cells were examined using quantitative RT-PCR and immunoblot analysis. Neurotoxicity was analysed in a transwell coculture system of primary cortical neurons with astrocytes and cultured neurons treated with astrocyte-conditioned medium (ACM). We also examined the lifespan, performed climbing assays and analysed immunohistochemical data in pan-glial TDP-43-expressing flies in the presence or absence of a Ptp61f RNAi transgene.ResultsPTP1B inhibition suppressed TDP-43-induced secretion of inflammatory cytokines (interleukin 1 beta (IL-1β), interleukin 6 (IL-6) and tumour necrosis factor alpha (TNF-α)) in primary astrocytes. Using a neuron-astrocyte coculture system and astrocyte-conditioned media treatment, we demonstrated that PTP1B inhibition attenuated neuronal death and mitochondrial dysfunction caused by overexpression of TDP-43 in astrocytes. In addition, neuromuscular junction (NMJ) defects, a shortened lifespan, inflammation and climbing defects caused by pan-glial overexpression of TDP-43 were significantly rescued by downregulation of ptp61f (the Drosophila homologue of PTP1B) in flies.ConclusionsThese results indicate that PTP1B inhibition mitigates the neuronal toxicity caused by TDP-43-induced inflammation in mammalian astrocytes and Drosophila glial cells.

Health Benefits of Silybum marianum: Phytochemistry, Pharmacology, and Applications.

Silybum marianum (SM), a well-known plant used as both a medicine and a food, has been widely used to treat various diseases, especially hepatic diseases. The seeds and fruits of SM contain a flavonolignan complex called silymarin, the active compounds of which include silybin, isosilybin, silychristin, dihydrosilybin, silydianin, and so on. In this review, we thoroughly summarize high-quality publications related to the pharmacological effects and underlying mechanisms of SM. SM has antimicrobial, anticancer, hepatoprotective, cardiovascular-protective, neuroprotective, skin-protective, antidiabetic, and other effects. Importantly, SM also counteracts the toxicities of antibiotics, metals, and pesticides. The diverse pharmacological activities of SM provide scientific evidence supporting its use in both humans and animals. Multiple signaling pathways associated with oxidative stress and inflammation are the common molecular targets of SM. Moreover, the flavonolignans of SM are potential agonists of PPARγ and ABCA1, PTP1B inhibitors, and metal chelators. At the end of the review, the potential and perspectives of SM are discussed, and these insights are expected to facilitate the application of SM and the discovery and development of new drugs. We conclude that SM is an interesting dietary medicine for health enhancement and drug discovery and warrants further investigation.

Mechanistic insight into the interactions between thiazolidinedione derivatives and PTP-1B combining 3D QSAR and molecular docking in the treatment of type 2 diabetes

Abstract Protein tyrosine phosphatases (PTP) regulate various cellular processes and represent important targets for therapeutic intervention in various diseases. Studies have shown that partial or total cessation of the PTP-1B gene in normal and diabetic mice has led to resistance to weight gain and improved insulin response. Also, a further study showed that inhibition of PTP-1B or a reduction in its cellular abundance in mice resulted in similar effects and, as such, provided a rationale for the treatment strategy for type 2 diabetes. Thiazolidinedione (TZD) derivatives have been identified as new PTP-1B inhibitors but the mechanism of interaction between TZD derivatives and PTP-1B is still elusive. In this study, a three-dimensional quantitative structure-activity relationship (3D-QSAR) analysis was performed, including multiple linear regression (MLR) and cross-validation, on a set of TZD derivatives as antidiabetic agents. MLR analysis was performed on 23 PTP-1B TZD derivatives to determine the relationships between physicochemical properties and antidiabetic properties of TZD derivatives. The training data set creates a QSAR model with a correlation coefficient (R 2) of 0.8516, a Q 2 (Leave-One-Out) cross-validation factor of 0.6473, r 2 (correlation coefficient) for the external dataset is 0.8367 while r 2 of predicted dataset is 0.8934 by the MLR Method. The MLR model was also validated by the standardization approach. We observed a high correlation between predicted and observed activity (experimental values), thus confirming and proving the high quality of QSAR models. Finally, molecular docking analysis was performed to better understand the interactions between the PTP-1B target and TZD derivatives. The model proposed in this project can be used to design new TZD derivatives with specific PTP-1B inhibitory activity.

Identification of Phomoxanthone A and B as Protein Tyrosine Phosphatase Inhibitors.

Phomoxanthone A and B (PXA and PXB) are xanthone dimers and isolated from the endophytic fungus Phomopsis sp. By254. The results demonstrated that PXB and PXA are noncompetitive inhibitors of SHP2 and PTP1B and competitive inhibitors of SHP1. Molecular docking studies showed that PXB and PXA interact with conserved domains of protein tyrosine phosphatases such as the β5-β6 loop, WPD loop, P loop, and Q loop. PXA and PXB could significantly inhibit the cell proliferation in MCF7 cells. Our results indicated that these two compounds do not efficiently inhibit PTP1B and SHP2 activity. RNA sequencing showed that PXA and PXB may inhibit SHP1 activity in MCF7 cells leading to the upregulation of inflammatory factors. In addition to PTP inhibition, PXA and PXB are multitarget compounds to inhibit the proliferation of tumor cells. In conclusion, both compounds show inhibition of cancer cells and a certain degree of inflammatory stimulation, which make them promising for tumor immunotherapy.

PTP1B and α-glucosidase inhibitors from Selaginella rolandi-principis and their glucose uptake stimulation.

As part of an ongoing search for new protein tyrosine phosphatase 1B inhibitors and glucose uptake stimulators from nature, a new coumarin, selaginolide A (1) and four known isoflavones (2‒5) were isolated from the ethanol extract of a Vietnamese medicinal plant Selaginella rolandi-principis. The chemical structures of the isolates were elucidated by extensive analysis of spectroscopic and physicochemical data. Compounds 3‒5 have been identified from Selaginella genus for the first time. The antidiabetic properties of the isolates (1‒5) were investigated using in vitro assay on 2-NBDG uptake in 3T3-L1 adipocytes and against PTP1B and α-glucosidase enzyme activities as well. Compounds 1 exhibited the most potency with inhibitory IC50 values of 7.40 ± 0.28 and 7.52 ± 0.37µM against PTP1B and α-glucosidase, respectively. Compounds 3 and 5 possessed potential inhibitions on PTP1B enzyme with IC50 values of 23.02 ± 1.29 and 11.08 ± 0.92µM and moderate inhibitions on α-glucosidase with IC50 values of 36.47 ± 1.87 and 55.73 ± 2.58µM, respectively. Compounds 2 and 4 showed weak PTP1B inhibitory activity (IC50 > 30µM) but displayed remarkable α-glucosidase inhibition with IC50 values of 3.39 ± 0.87 and 9.72 ± 0.62µM, respectively. Furthermore, ursolic acid as a positive control (IC50 3.42 ± 0.26µM) and compounds 1 and 5 acted as mixed-competitive inhibitors against PTP1B enzyme with Ki values of 6.46, 10.28, and 15.01µM, respectively. In addition, compounds 1 and 5 also showed potent stimulatory effects on 2-NBDG uptake at a concentration of 10µM. The obtained result might suggest the potential of new coumarin (1) as a new type of natural PTP1B and α-glucosidase inhibitor for further research and development of antidiabetic and obese agents.Graphic abstract.

Potential Inhibitors of Protein Tyrosine Phosphatase (PTP1B) Enzyme: Promising Target for Type-II Diabetes Mellitus.

There has been growing interest in the development of highly potent and selective protein tyrosine phosphatase (PTP1B) inhibitors for the past 2-3 decades. Though most PTPs share a common active site motif, the interest in selective inhibitors, particularly against PTP1B is increasing to discover new chemical entities as antidiabetic agents. In the current paradigm to find potent and selective PTP1B inhibitors, which is currently considered as one of the best validated biological targets for non-insulin-dependent diabetic and obese individuals, resistance to insulin due to decreased sensitivity of the insulin receptor is a pathological factor and is also genetically linked, causing type II diabetes. Insulin receptor sensitization is performed by a signal transduction mechanism via a selective protein tyrosine phosphatase (PTP1B). After the interaction of insulin with its receptor, autophosphorylation of the intracellular part of the receptor takes place, turning it into an active kinase (sensitization). PTP1B is involved in the desensitization of the receptor by dephosphorylation. PTP1b inhibitors delay the receptor desensitization, prolonging insulin effect and making PTP1B as a drug target for the treatment of diabetes II. Therefore, it has become a major target for the discovery of potent drugs for the treatment of type II diabetes and obesity. An attempt has been made in the present study to discuss the latest design and discovery of protein tyrosine phosphatase (PTP1B) inhibitors. Many PTP1B inhibitors such as diaminopyrroloquinazoline, triazines, pyrimido triazine derivatives, 2-(benzylamino)-1-phenylethanol, urea, acetamides and piperazinylpropanols, phenylsulphonamides and phenylcarboxamide, benzamido, arylcarboxylic acid derivatives, arylsupfonyl derivatives, thiazoles, isothiozolidiones and thiazolodinones have been discussed, citing the disease mechanisms. The reader will gain an overview of the structure and biological activity of recently developed PTPs inhibitors. The co-crystallized ligands and the screened inhibitors could be used as a template for the further design of potent congeners.

Optimization of ultrasound‐assisted extraction of melanin and its hypoglycemic activities from Sporisorium reilianum

Sporisorium reilianum (S. reiliana) is rich in nutrition, high in melanin content, and can be obtained by artificial species. It is a high-quality raw material for extracting natural melanin. Because of its unique structure and physicochemical property, natural melanin has become a stable and unique rare species in natural pigments. In this study, the effect of ultrasonic assisted on melanin extraction was studied with S. reiliana as a material. The influences of ultrasonic power, temperature, time, NaOH extract on melanin extraction in S. reiliana were investigated respectively. And through the single factor test and response surface method (RSM) to verify the evaluation. The RSM optimum conditions for melanin accumulation were: Ultrasonic power 245W, temperature 50°C, time 2 h, and pH 13 of NaOH extract. Under this condition, the return is 3.52%, which is close to the predicted value, indicating the feasibility of this model. For α-glycosidase and PTP1B inhibition assay, the melanin demonstrated the inhibitory effect with IC50 82.16 ± 5.02 μg/ml and 81.27 ± 10.48 μg/ml, respectively. This study reveals the hypoglycemic activities of the melanin isolated from S. reiliana for the first time. Practical applications Melanin from S. reiliana is an excellent hypoglycemic product due to its high α-glycosidase and PTP1B inhibition activity. However, its extraction yield is too low. The combination of unconventional techniques (ultrasound-assisted alkali dissolution and acid precipitation) is characterized as a new methodology for the extraction of melanin from S. reiliana. The extract provided a higher content of melanin than conventional methods. This technique is easily incorporated at the industrial level and is the low cost after the purchase of the relevant equipment.

Hypoglycemic Activity of Isolated Compounds from Gomphrena celosioides Mart

Five compounds (1 -– 5) were isolated from the leaves of Gomphrena celosioides Mart species harvested in Nam Dinh province and studied by chromatographic method. These compounds were identified as cleomiscosin A(1), dictyoceratin- C (2), ilimaquinone (3), bruceolline F (4), and neodactyloquinone (5). Their structures were elucidated by spectroscopic techniques including mass spectrometry (MS) and nuclear magnetic resonance (NMR). These compounds were isolated from the leaves of G. celosioides for the first time. All compounds were evaluated for their hypoglycemic activity in PTP1B inhibition and glucose uptake into 3T3-L1 adipocytes enhancement models. Results showed that compound 5 produced maximum effect with PTP1B inhibitory activity of 80.39 ± 6.88%, IC50 = 42.78 ± 2.86 μM, as well as the strongest ability to enhance glucose uptake in 3T3-L1 adipocytes.

Activation of tyrosine phosphatase PTP1B in pyramidal neurons impairs endocannabinoid signaling by tyrosine receptor kinase trkB and causes schizophrenia-like behaviors in mice.

Schizophrenia is a debilitating disorder affecting young adults displaying symptoms of cognitive impairment, anxiety, and early social isolation prior to episodes of auditory hallucinations. Cannabis use has been tied to schizophrenia-like symptoms, indicating that dysregulated endogenous cannabinoid signaling may be causally linked to schizophrenia. Previously, we reported that glutamatergic neuron-selective ablation of Lmo4, an endogenous inhibitor of the tyrosine phosphatase PTP1B, impairs endocannabinoid (eCB) production from the metabotropic glutamate receptor mGluR5. These Lmo4-deficient mice display anxiety-like behaviors that are alleviated by local shRNA knockdown or pharmacological inhibition of PTP1B that restores mGluR5-dependent eCB production in the amygdala. Here, we report that these Lmo4-deficient mice also display schizophrenia-like behaviors: impaired working memory assessed in the Y maze and defective sensory gating by prepulse inhibition of the acoustic startle response. Modulation of inhibitory inputs onto layer 2/3 pyramidal neurons of the prefrontal cortex relies on eCB signaling from the brain-derived neurotrophic factor receptor trkB, rather than mGluR5, and this mechanism was defective in Lmo4-deficient mice. Genetic ablation of PTP1B in the glutamatergic neurons lacking Lmo4 restored tyrosine phosphorylation of trkB, trkB-mediated eCB signaling, and ameliorated schizophrenia-like behaviors. Pharmacological inhibition of PTP1B with trodusquemine also restored trkB phosphorylation and improved schizophrenia-like behaviors by restoring eCB signaling, since the CB1 receptor antagonist 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-1-piperidinyl-1H-pyrazole-3-carboxamide blocked this effect. Thus, activation of PTP1B in pyramidal neurons contributes to schizophrenia-like behaviors in Lmo4-deficient mice and genetic or pharmacological intervention targeting PTP1B ameliorates schizophrenia-related deficits.

Analysis of polyphenolic metabolites from in vitro gastrointestinal digested soft fruit extracts identify malvidin-3-glucoside as an inhibitor of PTP1B

Protein-tyrosine phosphatase 1B (PTP1B, EC 3.1.3.48) is an important regulator of insulin signalling. Herein, we employed experimental and computational biology techniques to investigate the inhibitory properties of phenolics, identified from four in vitro gastrointestinal digested (IVGD) soft fruits, on PTP1B. Analysis by LC-MS/MS identified specific phenolics that inhibited PTP1B in vitro. Enzyme kinetics identified the mode of inhibition, while dynamics, stability and binding mechanisms of PTP1B-ligand complex were investigated through molecular modelling, docking, molecular dynamics (MD) simulations, and MM/PBSA binding free energy estimation. IVGD extracts and specific phenolics identified from the four soft fruits inhibited PTP1B (P < 0.0001) activity. Among the phenolics tested, the greatest inhibition was shown by malvidin-3-glucoside (P < 0.0001) and gallic acid (P < 0.0001). Malvidin-3-glucoside (Ki = 3.8 µg/mL) was a competitive inhibitor and gallic acid (Ki = 33.3 µg/mL) a non-competitive inhibitor of PTP1B. Malvidin-3-glucoside exhibited better binding energy than gallic acid and the synthetic inhibitor Dephostatin (−7.38 > −6.37 > −5.62 kcal/mol) respectively. Principal component analysis demonstrated malvidin-3-glucoside PTP1B-complex occupies more conformational space where critical WPD-loop displayed a higher degree of motion. MM/PBSA binding free energy for malvidin-3-glucoside to PTP1B was found to be higher than other complexes mediated by Van der Waals energy rather than electrostatic interaction for the other two inhibitors (-80.32 ± 1.25 > −40.64 ± 1.43 > −21.63 ± 1.73 kcal/mol) respectively. Altogether, we have established novel insights into the specific binding of dietary phenolics and have identified malvidin-3-glucoside as an PTP1B inhibitor, which may be further industrially developed for the treatment of type-2 diabetes.

Dimeric phenalenones from Talaromyces sp. (IQ-313) inhibit hPTP1B1-400: Insights into mechanistic kinetics from in vitro and in silico studies

A critical biological event that contributes to the appearance and progress of cancer and diabetes is the reversible phosphorylation of proteins, a process controlled by protein tyrosine-kinases (PTKs) and protein tyrosine-phosphatases (PTPs). Within the PTPs, PTP1B has gained significant interest since it is a validated target in drug discovery. Indeed, several PTP1B inhibitors have been developed, from both, synthesis and natural products. However, none have been approved by the FDA, due to their poor selectivity and/or pharmacokinetic properties. One of the most significant challenges to the discovery of PTP1B inhibitors (in vitro or in silico) is the use of truncated structures (PTP1B1-300), missing valuable information about the mechanisms of inhibition, and selectivity of ligands. The present study describes the biochemical characterization of a full-length PTP1B (hPTP1B1-400), as well as the description of phenalenones 1-4 and ursolic acid (5) as allosteric modulators. Compounds 1-5 showed inhibitory potential on hPTP1B1-400, with IC50 values ranging from 12.7 to 82.1µM. Kinetic studies showed that 1 and 5 behave as mixed and non-competitive inhibitors, respectively. Circular dichroism experiments confirmed that 1 and 5 induced conformational changes to hPTP1B1-400. Further insights into the structure of hPTP1B1-400 were obtained from a homology model, which pointed out that the C-terminus (residues 301-400) is highly disordered. Molecular docking with the homologated model suggested that compounds 1 and 3-5 bind to the C-terminal domain, likely inducing conformational changes on the protein. Docking positions of compounds 1, 4, and 5 were refined with molecular dynamics simulations. Importantly, these simulations confirmed the high flexibility of the C-terminus of hPTP1B1-400, as well as the changes to its rigidity when bound to 1, 4, and 5.

Inhibition of Protein-tyrosine Phosphatase PTP1B and LMPTP Promotes Palmitate/Oleate-challenged HepG2 Cell Survival by Reducing Lipoapoptosis, Improving Mitochondrial Dynamics and Mitigating Oxidative and Endoplasmic Reticulum Stress.

Objectives: Non-alcoholic fatty liver disease (NAFLD) is considered a well-known pathology that is determined without using alcohol and has emerged as a growing public health problem. Lipotoxicity is known to promote hepatocyte death, which, in the context of NAFLD, is termed lipoapoptosis. The severity of NAFLD correlates with the degree of hepatocyte lipoapoptosis. Protein–tyrosine phosphatases (PTP) including PTP1B and Low molecular weight PTP (LMPTP), are negative regulators of the insulin signaling pathway and are considered a promising therapeutic target in the treatment of diabetes. In this study, we hypothesized that the inhibition of PTP1B and LMPTP may potentially prevent hepatocyte apoptosis, mitochondrial dysfunction and endoplasmic reticulum (ER) stress onset, following lipotoxicity induced using a free fatty acid (FFA) mixture. Methods: HepG2 cells were cultured in the presence or absence of two PTP inhibitors, namely MSI-1436 and Compound 23, prior to palmitate/oleate overloading. Apoptosis, ER stress, oxidative stress, and mitochondrial dynamics were then evaluated by either MUSE or RT-qPCR analysis. Results: The obtained data demonstrate that the inhibition of PTP1B and LMPTP prevents apoptosis induced by palmitate and oleate in the HepG2 cell line. Moreover, mitochondrial dynamics were positively improved following inhibition of the enzyme, with concomitant oxidative stress reduction and ER stress abrogation. Conclusion: In conclusion, PTP’s inhibitory properties may be a promising therapeutic strategy for the treatment of FFA-induced lipotoxicity in the liver and ultimately in the management of the NAFLD condition.