PTP1B: a double agent in metabolism and oncogenesis

Spinal PTP1B Regulated NMDA Receptor-mediated Nociceptive Transmission and Peripheral Inflammation-induced Pain Sensitization

Protein tyrosine phosphatases (PTPs) catalyze the dephosphorylation of several pain-related substrates in spinal cord dorsal horn and are critically involved in the modification of pain transmission. The current study demonstrated that protein tyrosine phosphatase 1B (PTP1B), a unique endoplasmic reticulum-resident member of PTP family, displayed an activity-dependent increase in its protein expression and synaptic localization in spinal dorsal horn of adult male rats. PTP1B interacted with the Src Homology 3 (SH3) domain of Synapse-Associated Protein 102 (SAP102), one of the postsynaptic scaffolding proteins that anchored PTP1B at postsynaptic sites. The SAP102-tethered PTP1B augmented the synaptic transmission mediated specifically by GluN2B subunit-containing N-methyl-D-aspartate subtype glutamate receptors. Interference with PTP1B activity or disruption of its interaction with SAP102 attenuated GluN2B-mediated nociceptive transmission and ameliorated pain sensitization induced by intraplantar injection of Complete Freund's Adjuvant. These data suggested that the activity-dependent synaptic redistribution of PTP1B served as an important mechanism regulating GluN2B receptor activity and that manipulation of PTP1B synaptic targeting might represent an effective approach for the treatment of chronic inflammatory pain.

Protein tyrosine phosphatase 1B in metabolic and cardiovascular diseases: from mechanisms to therapeutics

Protein Tyrosine Phosphatase 1B (PTP1B) has emerged as a significant regulator of metabolic and cardiovascular disease. It is a non-transmembrane protein tyrosine phosphatase that negatively regulates multiple signaling pathways integral to the regulation of growth, survival, and differentiation of cells, including leptin and insulin signaling, which are critical for development of obesity, insulin resistance, type 2 diabetes, and cardiovascular disease. Given PTP1B's central role in glucose homeostasis, energy balance, and vascular function, targeted inhibition of PTP1B represents a promising strategy for treating these diseases. However, challenges, such as off-target effects, necessitate a focus on tissue-specific approaches, to maximize therapeutic benefits while minimizing adverse outcomes. In this review, we discuss molecular mechanisms by which PTP1B influences metabolic and cardiovascular functions, summarize the latest research on tissue-specific roles of PTP1B, and discuss the potential for PTP1B inhibitors as future therapeutic agents.

An expanded trove of fragment-bound structures for the allosteric enzyme PTP1B from computational reanalysis of large-scale crystallographic data

Due to their low binding affinities, detecting small-molecule fragments bound to protein structures from crystallographic datasets has been a challenge. Here, we report a trove of 65 new fragment hits for PTP1B, an "undruggable" therapeutic target enzyme for diabetes and cancer. These structures were obtained from computational analysis of data from a large crystallographic screen, demonstrating the power of this approach to elucidate many (∼50% more) "hidden" ligand-bound states of proteins. Our new structures include a fragment hit found in a novel binding site in PTP1B with a unique location relative to the active site, one that links adjacent allosteric sites, and, perhaps most strikingly, a fragment that induces long-range allosteric protein conformational responses. Altogether, our research highlights the utility of computational analysis of crystallographic data, makes publicly available dozens of new ligand-bound structures of a high-value drug target, and identifies novel aspects of ligandability and allostery in PTP1B.

Structures of human PTP1B variants reveal allosteric sites to target for weight loss therapy

Protein Tyrosine Phosphatase 1B (PTP1B) is a negative regulator of leptin signaling whose disruption protects against diet-induced obesity in mice. We investigated whether structural characterization of human PTP1B variant proteins might reveal precise mechanisms to target for weight loss therapy. We selected 12 rare variants for functional characterization from exomes from 997 people with persistent thinness and 200,000 people from UK Biobank. Seven of 12 variants impaired PTP1B function by increasing leptin-stimulated STAT3 phosphorylation in cells. Using room-temperature X-ray crystallography, hydrogen-deuterium exchange mass spectrometry, and computational modeling, we determined that human variants modulate the 3-dimensional structure of PTP1B through distinct allosteric conduits that energetically link distal, highly ligandable structural regions to the active site. These studies inform the design of allosteric PTP1B inhibitors for the treatment of obesity.

In silico analysis of the interaction of de novo peptides derived from Salvia hispanica with anticancer targetsEvaluation of the anticancer potential of de novo peptides derived from Salvia hispanica through molecular docking

Cancer is one of the leading causes of death worldwide. Conventional cancer therapies are not selective to cancer cells resulting in serious side effects on patients. Thus, the need for complementary treatments that improve the patient's response to cancer therapy is highly important. To predict and evaluate the physicochemical characteristics and potential anticancer activity of the peptides identified from S. hispanica protein fraction <1 kDa through the use of in silico tools. Peptides derived from Salvia hispanica's protein fraction <1 kDa were identified and analyzed for the prediction of their physicochemical properties. The characterized peptide sequences were then submitted to a multi-criteria decision analysis to identify the peptides that possess the characteristics to potentially exert anticancer activity. Through molecular docking analysis, the potential anticancer activity of the Potentially Anticancer Peptide (PAP)-1, PAP-2, PAP-3, PAP-4, and PAP-5 was estimated by their binding interactions with cancer and apoptosis-related molecules. All five evaluated PAPs exhibited strong binding interactions (< -100 kcal/mol). However, PAP-3 showed the lowest binding free energies with several of the targets. Thus, PAP-3 shows potential to be used as a nutraceutical or ingredient for functional foods that adjuvate in cancer treatment. Conclusions: Through the molecular docking studies, the binding of the PAPs to target molecules of interest for cancer treatment was successfully simulated, from which PAP-3 exhibited the lowest binding free energies. Further in vitro and in vivo studies are required to validate the predictions obtained by the in silico analysis.Communicated by Ramaswamy H. Sarma.

Protein tyrosine phosphatase 1B (PTP1B) function, structure, and inhibition strategies to develop antidiabetic drugs

Tyrosine protein phosphatase non-receptor type 1 (PTP1B; also known as protein tyrosine phosphatase 1B) is a member of the protein tyrosine phosphatase (PTP) family and is a soluble enzyme that plays an essential role in different physiological processes, including the regulation of metabolism, specifically in insulin and leptin sensitivity. PTP1B is crucial in the pathogenesis of type 2 diabetes mellitus and obesity. These biological functions have made PTP1B validated as an antidiabetic and anti-obesity, and potentially anticancer, molecular target. Four main approaches aim to inhibit PTP1B: orthosteric, allosteric, bidentate inhibition, and PTPN1 gene silencing. Developing a potent and selective PTP1B inhibitor is still challenging due to the enzyme's ubiquitous expression, subcellular location, and structural properties. This article reviews the main advances in the study of PTP1B since it was first isolated in 1988, as well as recent contextual information related to the PTP family to which this protein belongs. Furthermore, we offer an overview of the role of PTP1B in diabetes and obesity, and the challenges to developing selective, effective, potent, bioavailable, and cell-permeable compounds that can inhibit the enzyme.

Discovery of Selective Proteolysis-Targeting Chimera Degraders Targeting PTP1B as Long-Term Hypoglycemic Agents

PTP1B, a promising target for insulin sensitizers in type 2 diabetes treatment, can be effectively degraded using proteolysis-targeting chimera (PROTAC). This approach offers potential for long-acting antidiabetic agents. We report potent bifunctional PROTACs targeting PTP1B through the E3 ubiquitin ligase cereblon. Western blot analysis showed significant PTP1B degradation by PROTACs at concentrations from 5 nM to 5 μM after 48 h. Evaluation of five highly potent PROTACs revealed compound 75 with a longer PEG linker (23 atoms), displaying remarkable degradation activity after 48 and 72 h, with DC50 values of 250 nM and 50 nM, respectively. Compound 75 induced selective degradation of PTP1B, requiring engagement with both the target protein and CRBN E3 ligase, in a ubiquitination and proteasome-dependent manner. It significantly reduced blood glucose AUC0-2h to 29% in an oral glucose tolerance test and activated the IRS-1/PI3K/Akt signaling pathway in HepG2 cells, showing promise for long-term antidiabetic therapy.

Mulberry Leaf Compounds and Gut Microbiota in Alzheimer's Disease and Diabetes: A Study Using Network Pharmacology, Molecular Dynamics Simulation, and Cellular Assays

Recently, studies have reported a correlation that individuals with diabetes show an increased risk of developing Alzheimer's disease (AD). Mulberry leaves, serving as both a traditional medicinal herb and a food source, exhibit significant hypoglycemic and antioxidative properties. The flavonoid compounds in mulberry leaf offer therapeutic effects for relieving diabetic symptoms and providing neuroprotection. However, the mechanisms of this effect have not been fully elucidated. This investigation aimed to investigate the combined effects of specific mulberry leaf flavonoids (kaempferol, quercetin, rhamnocitrin, tetramethoxyluteolin, and norartocarpetin) on both type 2 diabetes mellitus (T2DM) and AD. Additionally, the role of the gut microbiota in these two diseases' treatment was studied. Using network pharmacology, we investigated the potential mechanisms of flavonoids in mulberry leaves, combined with gut microbiota, in combating AD and T2DM. In addition, we identified protein tyrosine phosphatase 1B (PTP1B) as a key target for kaempferol in these two diseases. Molecular docking and molecular dynamics simulations showed that kaempferol has the potential to inhibit PTP1B for indirect treatment of AD, which was proven by measuring the IC50 of kaempferol (279.23 μM). The cell experiment also confirmed the dose-dependent effect of kaempferol on the phosphorylation of total cellular protein in HepG2 cells. This research supports the concept of food-medicine homology and broadens the range of medical treatments for diabetes and AD, highlighting the prospect of integrating traditional herbal remedies with modern medical research.

Preventing obesity, insulin resistance and type 2 diabetes by targeting MT1-MMP

Obesity is one of the predominant risk factors for type 2 diabetes. Despite all the modern advances in medicine, an effective drug treatment for obesity without overt side effects has not yet been found. The discovery of growth and differentiation factor 15 (GDF15), an appetite-regulating hormone, created hopes for the treatment of obesity. However, an insufficient understanding of the physiological regulation of GDF15 has been a major obstacle to mitigating GDF15-centric treatment of obesity. Our recent studies revealed how a series of proteolytic events predominantly mediated by membrane-type 1 matrix metalloproteinase (MT1-MMP/MMP14), a key cell-surface metalloproteinase involved in extracellular remodeling, contribute to the pathogenesis of metabolic disorders, including obesity and diabetes. The MT1-MMP-mediated cleavage of the GDNF family receptor-α-like (GFRAL), a key neuronal receptor of GDF15, controls the satiety center in the hindbrain, thereby regulating non-homeostatic appetite and bodyweight changes. Furthermore, increased activation of MT1-MMP does not only lead to increased risk of obesity, but also causes age-associated insulin resistance by cleaving Insulin Receptor in major metabolic tissues. Importantly, inhibition of MT1-MMP effectively protects against obesity and diabetes, revealing the therapeutic potential of targeting MT1-MMP for the management of metabolic disorders.

Druggable targets of protein tyrosine phosphatase Family, viz. PTP1B, SHP2, Cdc25, and LMW-PTP: Current scenario on medicinal Attributes, and SAR insights

Protein tyrosine phosphatases (PTPs) are the class of dephosphorylation enzymes that catalyze the removal of phosphate groups from tyrosine residues on proteins responsible for various cellular processes. Any disbalance in signal pathways mediated by PTPs leads to various disease conditions like diabetes, obesity, cancers, and autoimmune disorders. Amongst the PTP superfamily, PTP1B, SHP2, Cdc25, and LMW-PTP have been prioritized as druggable targets for developing medicinal agents. PTP1B is an intracellular PTP enzyme that downregulates insulin and leptin signaling pathways and is involved in insulin resistance and glucose homeostasis. SHP2 is involved in the RAS-MAPK pathway and T cell immunity. Cdk-cyclin complex activation occurs by Cdc25-PTPs involved in cell cycle regulation. LMW-PTPs are involved in PDGF/PDGFR, Eph/ephrin, and insulin signaling pathways, resulting in certain diseases like diabetes mellitus, obesity, and cancer. The signaling cascades of PTP1B, SHP2, Cdc25, and LMW-PTPs have been described to rationalize their medicinal importance in the pathophysiology of diabetes, obesity, and cancer. Their binding sites have been explored to overcome the hurdles in discovering target selective molecules with optimum potency. Recent developments in the synthetic molecules bearing heterocyclic moieties against these targets have been explored to gain insight into structural features. The elaborated SAR investigation revealed the effect of substituents on the potency and target selectivity, which can be implicated in the further discovery of newer medicinal agents targeting the druggable members of the PTP superfamily.

Protein tyrosine phosphatase 1B contributes to neuropathic pain by aggravating NF-κB and glial cells activation-mediated neuroinflammation via promoting endoplasmic reticulum stress

BACKGROUND

Neuropathic pain is a prevalent and highly debilitating condition that impacts millions of individuals globally. Neuroinflammation is considered a key factor in the development of neuropathic pain. Accumulating evidence suggests that protein tyrosine phosphatase 1B (PTP1B) plays a crucial role in regulating neuroinflammation. Nevertheless, the specific involvement of PTP1B in neuropathic pain remains largely unknown. This study aims to examine the impact of PTP1B on neuropathic pain and unravel the underlying molecular mechanisms implicated.

METHODS

In the current study, we evaluated the paw withdrawal threshold (PWT) of male rats following spared nerve injury (SNI) to assess the presence of neuropathic pain. To elucidate the underlying mechanisms, western blotting, immunofluorescence, and electron microscopy techniques were employed.

RESULTS

Our results showed that SNI significantly elevated PTP1B levels, which was accompanied by an increase in the expression of endoplasmic reticulum (ER) stress markers (BIP, p-PERK, p-IRE1α, and ATF6) and phosphorylated NF-κB in the spinal dorsal horn. SNI-induced mechanical allodynia was impaired by the treatment of intrathecal injection of PTP1B siRNA or PTP1B-IN-1, a specific inhibitor of PTP1B. Moreover, the intrathecal administration of PTP1B-IN-1 effectively suppressed the expression of ER stress markers (BIP, p-PERK/p-eIF2α, p-IRE1α, and ATF6), leading to the inhibition of NF-κB, microglia, and astrocytes activation, as well as a decrease in pro-inflammatory cytokines, including TNF-α, IL-6, and IL-1β. However, these effects were reversed by intrathecal administration of tunicamycin (Tm, an inducer of ER stress). Additionally, intrathecal administration of Tm in healthy rats resulted in the development of mechanical allodynia and the activation of NF-κB-mediated neuroinflammatory signaling.

CONCLUSIONS

The upregulation of PTP1B induced by SNI facilitates the activation of NF-κB and glial cells via ER stress in the spinal dorsal horn. This, in turn, leads to an increase in the production of pro-inflammatory cytokines, thereby contributing to the development and maintenance of neuropathic pain. Therefore, targeting PTP1B could be a promising therapeutic strategy for the treatment of neuropathic pain.

An expanded view of ligandability in the allosteric enzyme PTP1B from computational reanalysis of large-scale crystallographic data

The recent advent of crystallographic small-molecule fragment screening presents the opportunity to obtain unprecedented numbers of ligand-bound protein crystal structures from a single high-throughput experiment, mapping ligandability across protein surfaces and identifying useful chemical footholds for structure-based drug design. However, due to the low binding affinities of most fragments, detecting bound fragments from crystallographic datasets has been a challenge. Here we report a trove of 65 new fragment hits across 59 new liganded crystal structures for PTP1B, an "undruggable" therapeutic target enzyme for diabetes and cancer. These structures were obtained from computational analysis of data from a large crystallographic screen, demonstrating the power of this approach to elucidate many (~50% more) "hidden" ligand-bound states of proteins. Our new structures include a fragment hit found in a novel binding site in PTP1B with a unique location relative to the active site, one that validates another new binding site recently identified by simulations, one that links adjacent allosteric sites, and, perhaps most strikingly, a fragment that induces long-range allosteric protein conformational responses via a previously unreported intramolecular conduit. Altogether, our research highlights the utility of computational analysis of crystallographic data, makes publicly available dozens of new ligand-bound structures of a high-value drug target, and identifies novel aspects of ligandability and allostery in PTP1B.

Protein tyrosine phosphatase 1B is a regulator of alpha-actinin4 in the glomerular podocyte

Glomerular podocytes are instrumental for the barrier function of the kidney, and podocyte injury contributes to proteinuria and the deterioration of renal function. Protein tyrosine phosphatase 1B (PTP1B) is an established metabolic regulator, and the inactivation of this phosphatase mitigates podocyte injury. However, there is a paucity of data regarding the substrates that mediate PTP1B actions in podocytes. This study aims to uncover novel substrates of PTP1B in podocytes and validate a leading candidate. To this end, using substrate-trapping and mass spectroscopy, we identified putative substrates of this phosphatase and investigated the actin cross-linking cytoskeletal protein alpha-actinin4. PTP1B and alpha-actinin4 co-localized in murine and human glomeruli and transiently transfected E11 podocyte cells. Additionally, podocyte PTP1B deficiency in vivo and culture was associated with elevated tyrosine phosphorylation of alpha-actinin4. Conversely, reconstitution of the knockdown cells with PTP1B attenuated alpha-actinin4 tyrosine phosphorylation. We demonstrated co-association between alpha-actinin4 and the PTP1B substrate-trapping mutant, which was enhanced upon insulin stimulation and disrupted by vanadate, consistent with an enzyme-substrate interaction. Moreover, we identified alpha-actinin4 tandem tyrosine residues 486/487 as mediators of its interaction with PTP1B. Furthermore, knockdown studies in E11 cells suggest that PTP1B and alpha-actinin4 are modulators of podocyte motility. These observations indicate that PTP1B and alpha-actinin4 are likely interacting partners in a signaling node that modulates podocyte function. Targeting PTP1B and plausibly this one of its substrates may represent a new therapeutic approach for podocyte injury that warrants additional investigation.

A PTP1B-Cdk3 Signaling Axis Promotes Cell Cycle Progression of Human Glioblastoma Cells through an Rb-E2F Dependent Pathway

PTP1B plays a key role in developing different types of cancer. However, the molecular mechanism underlying this effect is unclear. To identify molecular targets of PTP1B that mediate its role in tumorigenesis, we undertook a SILAC-based phosphoproteomic approach, which allowed us to identify Cdk3 as a novel PTP1B substrate. Substrate trapping experiments and docking studies revealed stable interactions between the PTP1B catalytic domain and Cdk3. In addition, we observed that PTP1B dephosphorylates Cdk3 at tyrosine residue 15 in vitro and interacts with it in human glioblastoma cells. Next, we found that pharmacological inhibition of PTP1B or its depletion with siRNA leads to cell cycle arrest with diminished activity of Cdk3, hypophosphorylation of Rb, and the downregulation of E2F target genes Cdk1, Cyclin A, and Cyclin E1. Finally, we observed that the expression of a constitutively active Cdk3 mutant bypasses the requirement of PTP1B for cell cycle progression and expression of E2F target genes. These data delineate a novel signaling pathway from PTP1B to Cdk3 required for efficient cell cycle progression in an Rb-E2F dependent manner in human GB cells.

Exploring the mechanism of the PTP1B inhibitors by molecular dynamics and experimental study

Protein tyrosine phosphatase 1B (PTP1B) has proven to be an attractive target for the treatment of cancer, diabetes and other diseases. Although many PTP1B inhibitors with various scaffolds have been developed, there is still a lack of PTP1B inhibitor with high specificity and acceptable pharmacological properties. Therefore, it is urgent to develop more methods to explore complex action mode of PTP1B and ligands for designing ideal PTP1B modulators. In this work, we developed a potential molecular dynamics (MD) analytic mode to analyze the mechanism of active compounds 6a and 6e against PTP1B from different perspectives, including the stable ability, interactions and binding site of ligand and protein, the binding energy, relative movement between residues and changes in protein internal interactions. The simulated results demonstrated that compound 6a bound more stably to the active pocket of PTP1B than 6e due to its smaller molecular volume (326 Å3), matched electronegativity, and enhanced the positive correlation motion of residues, especially for WPD loop and P loop. Lastly, compound 6a as a competitive inhibitor for PTP1B was verified by enzyme kinetic assay. This work successfully studied the mechanism of compound 6a against PTP1B from various aspects, enriched the analysis of interaction mode between PTP1B and inhibitors. In summary, we hope that this work could provide more theoretical information for designing and developing more novel and ideal PTP1B inhibitors in the future.

PTPN1 is a prognostic biomarker related to cancer immunity and drug sensitivity: from pan-cancer analysis to validation in breast cancer

Background

Protein tyrosine phosphatase non-receptor type 1 (PTPN1), a member of the protein tyrosine phosphatase superfamily, has been identified as an oncogene and therapeutic target in various cancers. However, its precise role in determining the prognosis of human cancer and immunological responses remains elusive. This study investigated the relationship between PTPN1 expression and clinical outcomes, immune infiltration, and drug sensitivity in human cancers, which will improve understanding regarding its prognostic value and immunological role in pan-cancer.

Methods

The PTPN1 expression profile was obtained from The Cancer Genome Atlas and Cancer Cell Line Encyclopedia databases. Kaplan-Meier, univariate Cox regression, and time-dependent receiver operating characteristic curve analyses were utilized to clarify the relationship between PTPN1 expression and the prognosis of pan-cancer patients. The relationships between PTPN1 expression and the presence of tumor-infiltrated immune cells were analyzed using Estimation of Stromal and Immune cells in Malignant Tumor tissues using Expression data and Tumor Immune Estimation Resource. The cell counting kit-8 (CCK-8) assay was performed to examine the effects of PTPN1 level on the sensitivity of breast cancer cells to paclitaxel. Immunohistochemistry and immunoblotting were used to investigate the relationship between PTPN1 expression, immune cell infiltration, and immune checkpoint gene expression in human breast cancer tissues and a mouse xenograft model.

Results

The pan-cancer analysis revealed that PTPN1 was frequently up-regulated in various cancers. High PTPN1 expression was associated with poor prognosis in most cancers. Furthermore, PTPN1 expression correlated highly with the presence of tumor-infiltrating immune cells and the expression of immune checkpoint pathway marker genes in different cancers. Furthermore, PTPN1 significantly predicted the prognosis for patients undergoing immunotherapy. The results of the CCK-8 viability assay revealed that PTPN1 knockdown increased the sensitivity of MDA-MB-231 and MCF-7 cells to paclitaxel. Finally, our results demonstrated that PTPN1 was associated with immune infiltration and immune checkpoint gene expression in breast cancer.

Conclusion

PTPN1 was overexpressed in multiple cancer types and correlated with the clinical outcome and tumor immunity, suggesting it could be a valuable potential prognostic and immunological biomarker for pan-cancer.

Exosomes as biomarkers and therapy in type 2 diabetes mellitus and associated complications

Type 2 diabetes mellitus (T2DM) is one of the most prevalent metabolic disorders worldwide. However, T2DM still remains underdiagnosed and undertreated resulting in poor quality of life and increased morbidity and mortality. Given this ongoing burden, researchers have attempted to locate new therapeutic targets as well as methodologies to identify the disease and its associated complications at an earlier stage. Several studies over the last few decades have identified exosomes, small extracellular vesicles that are released by cells, as pivotal contributors to the pathogenesis of T2DM and its complications. These discoveries suggest the possibility of novel detection and treatment methods. This review provides a comprehensive presentation of exosomes that hold potential as novel biomarkers and therapeutic targets. Additional focus is given to characterizing the role of exosomes in T2DM complications, including diabetic angiopathy, diabetic cardiomyopathy, diabetic nephropathy, diabetic peripheral neuropathy, diabetic retinopathy, and diabetic wound healing. This study reveals that the utilization of exosomes as diagnostic markers and therapies is a realistic possibility for both T2DM and its complications. However, the majority of the current research is limited to animal models, warranting further investigation of exosomes in clinical trials. This review represents the most extensive and up-to-date exploration of exosomes in relation to T2DM and its complications.

Analysis of neutral mutational drift in an allosteric enzyme

Neutral mutational drift is an important source of biological diversity that remains underexploited in fundamental studies of protein biophysics. This study uses a synthetic transcriptional circuit to study neutral drift in protein tyrosine phosphatase 1B (PTP1B), a mammalian signaling enzyme for which conformational changes are rate limiting. Kinetic assays of purified mutants indicate that catalytic activity, rather than thermodynamic stability, guides enrichment under neutral drift, where neutral or mildly activating mutations can mitigate the effects of deleterious ones. In general, mutants show a moderate activity-stability tradeoff, an indication that minor improvements in the activity of PTP1B do not require concomitant losses in its stability. Multiplexed sequencing of large mutant pools suggests that substitutions at allosterically influential sites are purged under biological selection, which enriches for mutations located outside of the active site. Findings indicate that the positional dependence of neutral mutations within drifting populations can reveal the presence of allosteric networks and illustrate an approach for using synthetic transcriptional systems to explore these mutations in regulatory enzymes.

Identification of natural product inhibitors of PTP1B based on high-throughput virtual screening strategy: In silico, in vitro and in vivo studies

Protein tyrosine phosphatase 1B (PTP1B) is a key negative regulator of the insulin signaling pathway, which is a potential therapeutic target for the treatment of type 2 diabetes mellitus (T2DM). In this study, we identified several PTP1B inhibitors with high activity by using high-throughput virtual screening and in vitro enzyme inhibition activity verification strategies. Among them, baicalin was first reported as a selective mixed inhibitor of PTP1B, with IC₅₀ value of 3.87 ± 0.45 μM, and its inhibitory activity against homologous proteins TCPTP, SHP2, and SHP1 exceeded 50 μM. Molecular docking study found that baicalin and PTP1B could bind stably, and revealed that baicalin had a dual inhibitory effect. Cell experiments showed that baicalin was almost non-toxic and could significantly enhance the phosphorylation of IRS-1 in C2C12 myotube cells. Animal experiments showed that baicalin could significantly reduce the blood sugar of STZ-induced diabetic mice models, and had a liver protective effect. In conclusion, this study can provide new ideas for the development of PTP1B selective inhibitors.

Catechins and Proanthocyanidins Involvement in Metabolic Syndrome

Recent studies on natural antioxidant compounds have highlighted their potentiality against various pathological conditions. The present review aims to selectively evaluate the benefits of catechins and their polymeric structure on metabolic syndrome, a common disorder characterized by a cluster of three main risk factors: obesity, hypertension, and hyperglycemia. Patients with metabolic syndrome suffer chronic low inflammation state and oxidative stress both conditions effectively countered by flavanols and their polymers. The mechanism behind the activity of these molecules has been highlighted and correlated with the characteristic features present on their basic flavonoidic skelethon, as well as the efficient doses needed to perform their activity in both in vitro and in vivo studies. The amount of evidence provided in this review offers a starting point for flavanol dietary supplementation as a potential strategy to counteract several metabolic targets associated with metabolic syndrome and suggests a key role of albumin as flavanol-delivery system to the different target of action inside the organism.

Isosteviol derivatives as protein tyrosine Phosphatase-1B inhibitors: Synthesis, biological evaluation and molecular docking

Protein tyrosine phosphatase (PTP1B) antagonizes insulin signaling and acts as a potential therapeutic target for insulin resistance associated with obesity and type II diabetes. In this work, a series of isosteviol derivatives 1-28 was synthesized and the inhibitory activity on PTP1B was evaluated by double antibody sandwich ELISA (DAS-ELISA) in vitro. Most isosteviol derivatives showed moderate PTP1B inhibitory activities. Among them, derivatives 10, 13, 24, 27 showed remarkable bioactivities with IC₅₀ values ranging from 0.24 to 0.40 µM. Particularly, derivative 24 exhibited the best inhibitory activity against PTP1B (IC₅₀ = 0.24 µM) in vitro; moreover, it showed 7-fold selectivity to PTP1B over T-cell protein tyrosine phosphatase (TCPTP) and 14-fold selectivity to PTP1B over cell division cycle 25 homolog B (CDC25B). Molecular docking studies demonstrated the hydrogen bond interaction between 24 and LYS-116 residue in PTP1B might be essential for the inhibitory activity. The results suggested that derivative 24 has great potential to be employed as drug candidate for the treatment of obesity and type II diabetes.

Dual PTP1B/TC-PTP Inhibitors: Biological Evaluation of 3-(Hydroxymethyl)cinnoline-4(1H)-Ones

Dual inhibitors of protein phosphotyrosine phosphatase 1B (PTP1B)/T-cell protein phosphotyrosine phosphatase (TC-PTP) based on the 3-(hydroxymethyl)-4-oxo-1,4-dihydrocinnoline scaffold have been identified. Their dual affinity to both enzymes has been thoroughly corroborated by in silico modeling experiments. The compounds have been profiled in vivo for their effects on body weight and food intake in obese rats. Likewise, the effects of the compounds on glucose tolerance, insulin resistance, as well as insulin and leptin levels, have been evaluated. In addition, the effects on PTP1B, TC-PTP, and Src homology region 2 domain-containing phosphatase-1 (SHP1), as well as the insulin and leptin receptors gene expressions, have been assessed. In obese male Wistar rats, a five-day administration of all studied compounds led to a decrease in body weight and food intake, improved glucose tolerance, attenuated hyperinsulinemia, hyperleptinemia and insulin resistance, and also compensatory increased expression of the PTP1B and TC-PTP genes in the liver. The highest activity was demonstrated by 6-Chloro-3-(hydroxymethyl)cinnolin-4(1H)-one (compound 3) and 6-Bromo-3-(hydroxymethyl)cinnolin-4(1H)-one (compound 4) with mixed PTP1B/TC-PTP inhibitory activity. Taken together, these data shed light on the pharmacological implications of PTP1B/TC-PTP dual inhibition, and on the promise of using mixed PTP1B/TC-PTP inhibitors to correct metabolic disorders.

[Characterization and biological activity of new 4-oxo-1,4-dihydrocinnoline-based inhibitors of the tyrosine phosphatase PTP1B and TCPTP]

Functional disorders in obesity are largely due to a decrease in tissue sensitivity to insulin and leptin. One of the ways to restore it is inhibition of protein phosphotyrosine phosphatase 1B (PTP1B) and T-cell protein phosphotyrosine phosphatase (TCPTP), negative regulators of the insulin and leptin signaling. Despite progress in the development of inhibitors of these phosphatases, commercial preparations based on them have not been developed yet, and the mechanisms of action are poorly understood. The aim of the work was to study the effect of new derivatives of 4-oxo-1,4-dihydrocinnoline (PI04, PI06, PI07) on the activity of PTP1B and TCPTP, as well as to study the effect of their five-day administration (i.p., 10 mg/kg/day) to Wistar rats with diet-induced obesity on body weight and fat, metabolic and hormonal parameters, and gene expression of phosphatase and insulin and leptin receptors in the liver. It has been shown that PI04 is a mild, low selective inhibitor of both phosphatases (PTP1B, IC50=3.42(2.60-4.51) μM; TCPTP, IC50=4.16(3.49-4.95) μM), while PI06 and PI07 preferentially inhibit PTP1B (IC50=3.55 (2.63-4.78) μM) and TCPTP (IC50=1.45(1.18-1.78) μM), respectively. PI04 significantly reduced food intake, body weight and fat, attenuated hyperglycemia, normalized glucose tolerance, basal and glucose-stimulated levels of insulin and leptin, and insulin resistance index. Despite the anorexigenic effect, PI06 and PI07 were less effective, having little effect on glucose homeostasis and insulin sensitivity. PI04 significantly increased the expression of the PTP1B and TCPTP genes and decreased the expression of the insulin and leptin receptor genes. PI06 and PI07 had little effect on these indicators. Thus, PI04, the inhibitor of PTP1B and TCPTP phosphatases, restored metabolic and hormonal parameters in obese rats with greater efficiency than inhibitors of PTP1B (PI06) and TCPTP (PI07). This indicates the prospect of creating mixed PTP1B/TCPTP inhibitors for correction of metabolic disorders.

Unified Total Synthesis of the Limonoid Alkaloids: Strategies for the De Novo Synthesis of Highly Substituted Pyridine Scaffolds

Highly substituted pyridine scaffolds are found in many biologically active natural products and therapeutics. Accordingly, numerous complementary de novo approaches to obtain differentially substituted pyridines have been disclosed. This article delineates the evolution of the synthetic strategies designed to assemble the demanding tetrasubstituted pyridine core present in the limonoid alkaloids isolated from Xylocarpus granatum, including xylogranatopyridine B, granatumine A and related congeners. In addition, NMR calculations suggested structural misassignment of several limonoid alkaloids, and predicted their C3-epimers as the correct structures, which was further validated unequivocally through chemical synthesis. The materials produced in this study were evaluated for cytotoxicity, anti-oxidant effects, anti-inflammatory action, PTP1B and Nlrp3 inflammasome inhibition, which led to compelling anti-inflammatory activity and anti-oxidant effects being discovered.

Targeting the PTP1B-Bcr-Abl1 interaction for the degradation of T315I mutant Bcr-Abl1 in chronic myeloid leukemia

Small-molecule-induced degradation of mutant Bcr-Abl1 provides a potential approach to overcome Bcr-Abl1 tyrosine kinase inhibitor (TKI)-resistant chronic myeloid leukemia (CML). Our previous study reported that a synthetic steroidal glycoside SBF-1 showed remarkable anti-CML activity by inducing the degradation of native Bcr-Abl1 protein. Here, we observed the comparable growth inhibition for SBF-1 in CML cells harboring T315I mutant Bcr-Abl1 in vitro and in vivo. SBF-1 triggered its degradation through disrupting the interaction between protein-tyrosine phosphatase 1B (PTP1B) and Bcr-Abl1. Using SBF-1 as a tool, we found that Tyr46 in the PTP1B catalytic domain and Tyr852 in the Bcr-Abl1 pleckstrin-homology (PH) domain are critical for their interaction. Moreover, the phosphorylation of Tyr1086 within the Bcr-Abl1 SH2 domain recruited the E3 ubiquitin ligase c-Cbl to catalyze K27-linked ubiquitin chains, which serve as a recognition signal for p62-dependent autophagic degradation. PTP1B dephosphorylated Bcr-Abl1 at Tyr1086 and prevented the recruitment of c-Cbl, leading to the stability of Bcr-Abl1. This study unravels the action mechanism of PTP1B in stabilizing Bcr-Abl1 protein and indicates that the PTP1B-Bcr-Abl1 interaction might be one of druggable targets for TKI-resistant CML with point mutations.

N-Octyl Caffeamide, a Caffeic Acid Amide Derivative, Prevents Progression of Diabetes and Hepatic Steatosis in High-Fat Diet Induced Obese Mice

The underlying pathological mechanisms of diabetes are complicated and varied in diabetic patients, which may lead to the current medications often failing to maintain glycemic control in the long term. Thus, the discovery of diverse new compounds for developing medicines to treat diabetes and its complications are urgently needed. Polyphenols are metabolites of plants and have been employed in the prevention and treatment of a variety of diseases. Caffeic acid phenethyl ester (CAPE) is a category of compounds structurally similar to polyphenols. In this study, we aimed to investigate the antidiabetic activity and potential molecular mechanisms of a novel synthetic CAPE derivative N-octyl caffeamide (36M) using high-fat (HF) diet induced obese mouse models. Our results demonstrate that 36M prevented the progression of diabetes in the HF diet fed obese mice via increasing phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and inhibiting expression of protein tyrosine phosphatase 1B (PTP1B). We also found that 36M could prevent hepatic lipid storage in the HF diet fed mice via inhibition of fatty acid synthase and lipid droplet proteins, including perilipins and Fsp27. In conclusion, 36M is a potential candidate compound that can be developed as AMPK inhibitor and PTP1B inhibitor for treating diabetes and hepatic steatosis.

The Effects of Persimmon (Diospyros kaki L.f.) Oligosaccharides on Features of the Metabolic Syndrome in Zebrafish

Metabolic syndrome has become a global health care problem since it is rapidly increasing worldwide. The search for alternative natural supplements may have potential benefits for obesity and diabetes patients. Diospyros kaki fruit extract and its oligosaccharides, including gentiobiose, melibiose, and raffinose, were examined for their anti-insulin resistance and obesity-preventing effect in zebrafish larvae. The results show that D. kaki oligosaccharides improved insulin resistance and high-fat-diet-induced obesity in zebrafish larvae, evidenced by enhanced β-cell recovery, decreased abdominal size, and reduced the lipid accumulation. The mechanism of the oligosaccharides, molecular docking, and enzyme activities of PTP1B were investigated. Three of the oligosaccharides had a binding interaction with the catalytic active sites of PTP1B, but did not show inhibitory effects in an enzyme assay. The catalytic residues of PTP1B were typically conserved and the cellular penetration of the cell membrane was necessary for the inhibitors. The results of the mechanism of action study indicate that D. kaki fruit extract and its oligosaccharides affected gene expression changes in inflammation- (TNF-α, IL-6, and IL-1β), lipogenesis- (SREBF1 and FASN), and lipid-lowering (CPT1A)-related genes. Therefore, D. kaki fruit extract and its oligosaccharides may have a great potential for applications in metabolic syndrome drug development and dietary supplements.

Evaluation of Biological Activity of Natural Compounds: Current Trends and Methods

Natural compounds have diverse structures and are present in different forms of life. Metabolites such as tannins, anthocyanins, and alkaloids, among others, serve as a defense mechanism in live organisms and are undoubtedly compounds of interest for the food, cosmetic, and pharmaceutical industries. Plants, bacteria, and insects represent sources of biomolecules with diverse activities, which are in many cases poorly studied. To use these molecules for different applications, it is essential to know their structure, concentrations, and biological activity potential. In vitro techniques that evaluate the biological activity of the molecules of interest have been developed since the 1950s. Currently, different methodologies have emerged to overcome some of the limitations of these traditional techniques, mainly via reductions in time and costs. These emerging technologies continue to appear due to the urgent need to expand the analysis capacity of a growing number of reported biomolecules. This review presents an updated summary of the conventional and relevant methods to evaluate the natural compounds' biological activity in vitro.

Human Protein Tyrosine Phosphatase 1B (PTP1B): From Structure to Clinical Inhibitor Perspectives

Phosphorylation is an essential process in biological events and is considered critical for biological functions. In tissues, protein phosphorylation mainly occurs on tyrosine (Tyr), serine (Ser) and threonine (Thr) residues. The balance between phosphorylation and dephosphorylation is under the control of two super enzyme families, protein kinases (PKs) and protein phosphatases (PPs), respectively. Although there are many selective and effective drugs targeting phosphokinases, developing drugs targeting phosphatases is challenging. PTP1B, one of the most central protein tyrosine phosphatases (PTPs), is a key player in several human diseases and disorders, such as diabetes, obesity, and hematopoietic malignancies, through modulation of different signaling pathways. However, due to high conservation among PTPs, most PTP1B inhibitors lack specificity, raising the need to develop new strategies targeting this enzyme. In this mini-review, we summarize three classes of PTP1B inhibitors with different mechanisms: (1) targeting multiple aryl-phosphorylation sites including the catalytic site of PTP1B; (2) targeting allosteric sites of PTP1B; (3) targeting specific mRNA sequence of PTP1B. All three types of PTP1B inhibitors present good specificity over other PTPs and are promising for the development of efficient small molecules targeting this enzyme.

Biochemical, Enzymatic, and Computational Characterization of Recurrent Somatic Mutations of the Human Protein Tyrosine Phosphatase PTP1B in Primary Mediastinal B Cell Lymphoma

Human protein tyrosine phosphatase 1B (PTP1B) is a ubiquitous non-receptor tyrosine phosphatase that serves as a major negative regulator of tyrosine phosphorylation cascades of metabolic and oncogenic importance such as the insulin, epidermal growth factor receptor (EGFR), and JAK/STAT pathways. Increasing evidence point to a key role of PTP1B-dependent signaling in cancer. Interestingly, genetic defects in PTP1B have been found in different human malignancies. Notably, recurrent somatic mutations and splice variants of PTP1B were identified in human B cell and Hodgkin lymphomas. In this work, we analyzed the molecular and functional levels of three PTP1B mutations identified in primary mediastinal B cell lymphoma (PMBCL) patients and located in the WPD-loop (V184D), P-loop (R221G), and Q-loop (G259V). Using biochemical, enzymatic, and molecular dynamics approaches, we show that these mutations lead to PTP1B mutants with extremely low intrinsic tyrosine phosphatase activity that display alterations in overall protein stability and in the flexibility of the active site loops of the enzyme. This is in agreement with the key role of the active site loop regions, which are preorganized to interact with the substrate and to enable catalysis. Our study provides molecular and enzymatic evidence for the loss of protein tyrosine phosphatase activity of PTP1B active-site loop mutants identified in human lymphoma.

PTP1B inhibition ameliorates inflammatory injury and dysfunction in ox‑LDL‑induced HUVECs by activating the AMPK/SIRT1 signaling pathway via negative regulation of KLF2

Atherosclerosis is a key pathogenic factor of cardiovascular diseases. However, the role of protein tyrosine phosphatase 1B (PTP1B) in oxidized low-density lipoprotein (ox-LDL)-treated vascular endothelial cells remains unclear. The aim of the present study was to explore the possible physiological roles and mechanism of PTP1B in atherosclerosis using HUVECs as an in vitro model. PTP1B expression was assessed by reverse transcription-quantitative PCR. Cell viability was measured using the Cell Counting Kit-8 and lactate dehydrogenase activity assays. Levels of inflammatory factors, including IL-1β, IL-6 and TNF-α, and oxidative stress factors, including malondialdehyde, superoxide dismutase and glutathione peroxidase, were assessed using ELISA and commercially available kits, respectively. Furthermore, TUNEL assay and western blotting were performed to assess the extent of apoptosis-related factors, including Bcl-2, Bax, Cleaved caspase-3 and Caspase-3. Tube formation assay was used to assess tubule formation ability and western blotting was to analyze VEGFA protein level. Binding sites for the transcription factor Kruppel-like factor 2 (KLF2) on the PTP1B promoter were predicted using the JASPAR database and verified using luciferase reporter assays and chromatin immunoprecipitation. The protein levels of phosphorylated 5'AMP-activated protein kinase (p-AMPK), AMPK and SIRT1 were measured using western blotting. The results demonstrated that the PTP1B mRNA and protein expression levels were significantly upregulated in oxidized low-density lipoprotein (ox-LDL)-induced HUVECs. In addition, ox-LDL-induced HUVECs transfected with short hairpin RNA against PTP1B exhibited a significant increase in cell viability, reduced inflammatory factor levels, apoptosis and oxidative stress, as well as increased tubule formation ability. KLF2 was found to negatively regulate the transcriptional activity of PTP1B. KLF2 knockdown reversed the protective effects of PTP1B knockdown on ox-LDL-induced HUVECs. KLF2 knockdown also abolished PTP1B knockdown-triggered AMPK/SIRT1 signaling pathway activation in ox-LDL-induced HUVECs. To conclude, the results of the present study suggested that PTP1B knockdown can prevent ox-LDL-induced inflammatory injury and dysfunction in HUVECs, which is regulated at least in part by the AMPK/SIRT1 signaling pathway through KLF2.

Direct Intracellular Delivery of Benzene Diazonium Ions As Observed by Increased Tyrosine Phosphorylation

A challenge within the field of bioconjugation is developing probes to uncover novel information on proteins and other biomolecules. Intracellular delivery of these probes offers the promise of giving relevant context to this information, and these probes can serve as hypothesis-generating tools within complex systems. Leveraging the utility of triazabutadiene chemistry, herein, we discuss the development of a probe that undergoes reduction-mediated deprotection to rapidly deliver a benzene diazonium ion (BDI) into cells. The intracellular BDI resulted in an increase in global tyrosine phosphorylation levels. Seeing phosphatase dysregulation as a potential source of this increase, a tyrosine phosphatase (PTP1B) was tested and shown to be both inhibited and covalently modified by the BDI. In addition to the expected azobenzene formation at tyrosine side chains, key reactive histidine residues were also modified.

Increased O-GlcNAcylation promotes IGF-1 receptor/PhosphatidyI Inositol-3 kinase/Akt pathway in cervical cancer cells

O-linked β-N-acetylglucosaminylation (O-GlcNAcylation) is a reversible post-translational modification on serine and threonine residues of cytosolic, nuclear and mitochondrial proteins. O-GlcNAcylation level is regulated by OGT (O-GlcNAc transferase), which adds GlcNAc on proteins, and OGA (O-GlcNAcase), which removes it. Abnormal level of protein O-GlcNAcylation has been observed in numerous cancer cell types, including cervical cancer cells. In the present study, we have evaluated the effect of increasing protein O-GlcNAcylation on cervical cancer-derived CaSki cells. We observed that pharmacological enhancement of protein O-GlcNAcylation by Thiamet G (an inhibitor of OGA) and glucosamine (which provides UDP-GlcNAc substrate to OGT) increases CaSki cells proliferation, migration and survival. Moreover, we showed that increased O-GlcNAcylation promotes IGF-1 receptor (IGF1R) autophosphorylation, possibly through inhibition of protein tyrosine-phosphatase 1B activity. This was associated with increased IGF-1-induced phosphatidyl-Inositol 3-phosphate production at the plasma membrane and increased Akt activation in CaSki cells. Finally, we showed that protein O-GlcNAcylation and Akt phosphorylation levels were higher in human cervical cancer samples compared to healthy cervix tissues, and a highly positive correlation was observed between O-GlcNAcylation level and Akt phosphorylation in theses tissues. Together, our results indicate that increased O-GlcNAcylation, by activating IGF1R/ Phosphatidyl inositol 3-Kinase (PI-3K)/Akt signaling, may participate in cervical cancer cell growth and proliferation.

Myeloid-Specific PTP1B Deficiency Attenuates Inflammation-Induced and Ovariectomy-Induced Bone Loss in Mice by Inhibiting Osteoclastogenesis

The differentiation and activity of bone-resorbing osteoclasts are tightly regulated to maintain the homeostasis of healthy bones. In this study, the role of protein tyrosine phosphatase 1B (PTP1B) during osteoclastogenesis was studied in myeloid-specific Ptpn1-deficient (conditional knockout [cKO]) mice. The mRNA and protein expression of PTP1B increased during the formation of mature osteoclasts from mouse bone macrophages on stimulation with macrophage-colony stimulating factor (M-CSF) and receptor activator of nuclear factor κB ligand (RANKL). The Ptpn1 cKO mice exhibited increased femoral trabecular bone volume with a decreased number and activity of osteoclasts compared with control mice. The in vitro culture of osteoclast precursors corroborated the inhibition of osteoclastogenesis in cKO cells compared with control, with concomitantly decreased RANKL-dependent proliferation, lower osteoclast marker gene expression, reduced nuclear expression of nuclear factor of activated T cells cytoplasmic 1 (NFATc1), diminished intracellular Ca²⁺ oscillations, and increased phosphorylation of proto-oncogene tyrosine-protein kinase Src on inhibitory tyrosine residue. In a ligature-induced periodontitis model, Ptpn1 cKO mice exhibited attenuated osteoclastogenesis and alveolar bone loss following the induction of inflammation. The Ptpn1-deficient mice were similarly protected from ovariectomy-induced bone loss compared with control mice. These results provide a novel regulatory role of PTP1B in osteoclastogenesis and suggest a potential as a therapeutic target for bone-lytic diseases. © 2021 American Society for Bone and Mineral Research (ASBMR).

An update on mode of action of metformin in modulation of meta-inflammation and inflammaging

Type 2 diabetes mellitus (T2DM) is the most common chronic metabolic condition. Several genetic and environmental factors are involved in developing T2DM. Aging, inflammation, and obesity are the main contributors to the initiation of T2DM. They cause chronic sterile meta-inflammation and insulin resistance, thereby making a person more susceptible to developing T2DM. Metformin, a natural cationic biguanide, is widely used as the first-line treatment of T2DM. The exact action mechanism behind the glucose-lowering effect of metformin is not clear, but, presumably, metformin utilizes a broad spectrum of molecular mechanisms to control blood glucose including decreasing intestinal glucose absorption, inhibition of the hepatic gluconeogenesis, decreasing insulin resistance, etc. Recent studies have shown that metformin exerts its effects through the inhibition of mitochondrial respiratory chain complex 1 and the AMP-activated protein kinase (AMPK) activation, but it has been identified in the other studies that AMPK is not the sole hub in metformin mode of action or there are other unknown mechanisms which are involved and yet to be explored. Therefore, here, we discuss the updated findings of the mechanism of action of metformin that contributes to the meta-inflammation and inflammaging action. It is proposed that figuring out the precise mechanism of action of metformin could improve its application in the fields of obesity, inflammation, aging, and inflammaging.

Isothiocyanate From Moringa oleifera Seeds Inhibits the Growth and Migration of Renal Cancer Cells by Regulating the PTP1B-dependent Src/Ras/Raf/ERK Signaling Pathway

Moringa oleifera Lam. is a tropical and subtropical plant that has been used for centuries as both food and traditional medicine. 4-[(α-L-Rhamnosyloxy) benzyl] isothiocyanate (MIC-1) is an active substance in M. oleifera, with anti-cancer activity. However, whether MIC-1 exerts anti-renal cancer effects is unknown. Therefore, the aim of the present study was to evaluate the effects of MIC-1 on the growth and migration of renal cell carcinoma (RCC) cells and to identify the putative underlying mechanism. We found that, among 30 types of cancer cells, MIC-1 exerted the strongest growth inhibitory effects against 786-O RCC cells. In addition, MIC-1 (10 μM) significantly inhibited the growth of five RCC cell lines, including 786-O, OSRC-2, 769-P, SK-NEP-1, and ACHN cells, but was not toxic to normal renal (HK2) cells. Also, MIC-1 suppressed 786-O and 769-P cell migration and invasion abilities, and reduced the expression of matrix metalloproteinase (MMP)-2 and MMP-9. Furthermore, MIC-1 induced apoptosis and cell cycle arrest, increased Bax/Bcl-2 ratio, and decreased cell cycle-related protein expression in 786-O cells and 769-P cells. Molecular docking and small-molecule interaction analyses with PTP1B both showed that MIC-1 inhibited PTP1B activity by binding to its active site through hydrogen bonding and hydrophobic interactions. Additionally, MIC-1 could suppress the growth and migration of 786-O cells by inhibiting PTP1B-mediated activation of the Src/Ras/Raf/ERK signaling pathway. In vivo experiments further showed that MIC-1 markedly inhibited the growth of xenograft tumors in mice, and greatly increased Bax/Bcl-2 ratio in tumor tissues. In addition, MIC-1 had no effect on the PTP1B-dependent Src/Ras/Raf/ERK signaling pathway in HCT-116 cells, Hep-G2 cells, and A431 cells. Overall, our data showed that MIC-1 could be a promising, non-toxic, natural dietary supplement for the prevention and treatment of renal cancer.

The role of protein tyrosine phosphatase 1B (PTP1B) in the pathogenesis of type 2 diabetes mellitus and its complications

Insulin resistance, the most important characteristic of the type 2 diabetes mellitus (T2DM), is mostly caused by impairment in the insulin receptor (IR) signal transduction pathway. Protein tyrosine phosphatase 1B (PTP1B), one of the main negative regulators of the IR signaling pathway, is broadly expressed in various cells and tissues. PTP1B decreases the phosphorylation of the IR resulting in insulin resistance in various tissues. The evidence for the physiological role of PTP1B in regulation of metabolic pathways came from whole-body PTP1B-knockout mice. Whole-body and tissue-specific PTP1B-knockout mice showed improvement in adiposity, insulin resistance, and glucose tolerance. In addition, the key role of PTP1B in the pathogenesis of T2DM and its complications was further investigated in mice models of PTP1B deficient/overexpression. In recent years, targeting PTP1B using PTP1B inhibitors is being considered an attractive target to treat T2DM. PTP1B inhibitors improve the sensitivity of the insulin receptor and have the ability to cure insulin resistance-related diseases. We herein summarized the biological functions of PTP1B in different tissues in vivo and in vitro. We also describe the effectiveness of potent PTP1B inhibitors as pharmaceutical agents to treat T2DM.

Unleashing T cell responses to cancer through removal of intracellular checkpoints

In a new study, researchers identified protein tyrosine phosphatase PTP1B as an inhibitor of cytokine receptor signalling and demonstrated that blocking activity or expression of this enzyme unleashes T cell responses to cancer.

Which Role Plays 2-Hydroxybutyric Acid on Insulin Resistance?

Type 2 Diabetes Mellitus (T2D) is defined as a chronic condition caused by beta cell loss and/or dysfunction and insulin resistance (IR). The discovering of novel biomarkers capable of identifying T2D and other metabolic disorders associated with IR in a timely and accurate way is critical. In this review, 2-hydroxybutyric acid (2HB) is presented as that upheaval biomarker with an unexplored potential ahead. Due to the activation of other metabolic pathways during IR, 2HB is synthesized as a coproduct of protein metabolism, being the progression of IR intrinsically related to the increasing of 2HB levels. Hence, the focus of this review will be on the 2HB metabolite and its involvement in glucose homeostasis. A literature review was conducted, which comprised an examination of publications from different databases that had been published over the previous ten years. A total of 19 articles fulfilled the intended set of criteria. The use of 2HB as an early indicator of IR was separated into subjects based on the number of analytes examined simultaneously. In terms of the association between 2HB and IR, it has been established that increasing 2HB levels can predict the development of IR. Thus, 2HB has demonstrated considerable promise as a clinical monitoring molecule, not only as an IR biomarker, but also for disease follow-up throughout IR treatment.

Recent advances in PTP1B signaling in metabolism and cancer

Protein tyrosine phosphorylation is one of the major post-translational modifications in eukaryotic cells and represents a critical regulatory mechanism of a wide variety of signaling pathways. Aberrant protein tyrosine phosphorylation has been linked to various diseases, including metabolic disorders and cancer. Few years ago, protein tyrosine phosphatases (PTPs) were considered as tumor suppressors, able to block the signals emanating from receptor tyrosine kinases. However, recent evidence demonstrates that misregulation of PTPs activity plays a critical role in cancer development and progression. Here, we will focus on PTP1B, an enzyme that has been linked to the development of type 2 diabetes and obesity through the regulation of insulin and leptin signaling, and with a promoting role in the development of different types of cancer through the activation of several pro-survival signaling pathways. In this review, we discuss the molecular aspects that support the crucial role of PTP1B in different cellular processes underlying diabetes, obesity and cancer progression, and its visualization as a promising therapeutic target.

Possible Gender Influence in the Mechanisms Underlying the Oxidative Stress, Inflammatory Response, and the Metabolic Alterations in Patients with Obesity and/or Type 2 Diabetes

The number of patients afflicted by type 2 diabetes and its morbidities has increased alarmingly, becoming the cause of many deaths. Normally, during nutrient intake, insulin secretion is increased and glucagon secretion is repressed, but when plasma glucose concentration increases, a state of prediabetes occurs. High concentration of plasma glucose breaks the redox balance, inducing an oxidative stress that promotes chronic inflammation, insulin resistance, and impaired insulin secretion. In the same context, obesity is one of the most crucial factors inducing insulin resistance, inflammation, and contributing to the onset of type 2 diabetes. Measurements of metabolites like glucose, fructose, amino acids, and lipids exhibit significant predictive associations with type 2 diabetes or a prediabetes state and lead to changes in plasma metabolites that could be selectively affected by gender and age. In terms of gender, women and men have biological dissimilarities that might have an important role for the development, diagnosis, therapy, and prevention of type 2 diabetes, obesity, and relevant hazards in both genders, for type 2 diabetes. Therefore, the present review attempts to analyze the influence of gender on the relationships among inflammatory events, oxidative stress, and metabolic alterations in patients undergoing obesity and/or type 2 diabetes.

PTP1B inhibition studies of biological active phloroglucinols from the rhizomes of Dryopteris crassirhizoma: Kinetic properties and molecular docking simulation

By various chromatographic methods, 30 phloroglucinols (1-30) were isolated from a methanol extract of Dryopteris crassirhizoma, including two new dimeric phloroglucinols (13 and 25). The structures of the isolates were confirmed by HR-MS, 1D, and 2D NMR as well as by comparison with the literature. The protein tyrosine phosphatase 1B (PTP1B) effects of the isolated compounds (1-30) were evaluated using sodium orthovanadate and ursolic acid as a positive control. Among them, trimeric phloroglucinols 26-28 significantly exhibited the PTP1B inhibitory effects with the IC₅₀ values of 1.19 ± 0.13, 1.00 ± 0.04, 1.23 ± 0.05 μM, respectively. In addition, the kinetic analysis revealed compounds 26-28 acted as competitive inhibitors against PTP1B enzyme with K_i values of 0.63, 0.61, 1.57 μM, respectively. Molecular docking simulations were performed to demonstrate that these active compounds can bind with the catalytic sites of PTP1B with negative binding energies and the results are in accordance with that of the kinetic studies. In vitro and in silico results suggest that D. crassirhizoma rhizomes together with compounds 26-28 are potential candidates for treating type 2 diabetes.

Synthesis, structure and in vitro biological properties of a new copper(II) complex with 4-{[3-(pyridin-2-yl)-1H-pyrazol-1-yl]methyl}benzoic acid

The new copper(II) complex dichloridobis(4-{[3-(pyridin-2-yl-κN)-1H-pyrazol-1-yl-κN²]methyl}benzoic acid)copper(II) methanol sesquisolvate hemihydrate, [CuCl₂L₂]·1.5CH₃OH·0.5H₂O, (1), has been synthesized from CuCl₂·2H₂O and the ligand 4-{[3-(pyridin-2-yl)-1H-pyrazol-1-yl]methyl}benzoic acid (L, C₁₅H₁₁N₃O₂). The complex was characterized by elemental analysis, Fourier transform IR spectroscopy, electrospray ionization mass spectrometry and single-crystal X-ray diffraction. Two chloride ligands and two bidentate L ligands coordinate the Cu^II centre in 1 in a Jahn-Teller-distorted octahedral geometry of rather unusual configuration: a chloride substituent and a pyrazole N atom of an N,N'-chelating ligand occupy the more distant axial positions. Classical O-H...O hydrogen bonds and O-H...Cl interactions link neighbouring complex molecules and cocrystallized methanol molecules into chains that propagate parallel to the b direction. The title compound shows intriguing bioactivity: the effects of 1 on the enzymatic activity of protein tyrosine phosphatase 1B (PTP1B) and on the viability of human breast cancer cells of cell line MCF7 were evaluated. Complex 1, with an IC₅₀ value of 0.51 µM, can efficiently inhibit PTP1B activity. An enzyme kinetic assay suggests that 1 inhibits PTP1B in a noncompetitive manner. A fluorescence titration assay indicates that 1 has a strong affinity for PTP1B, with a binding constant of 4.39 × 10⁶ M^-1. Complex 1 may also effectively decrease the viability of MCF7 cells in an extent comparable to that of cisplatin (IC₅₀ = 6.3 µM). The new copper complex therefore represents a promising PTP1B inhibitor and an efficient antiproliferation reagent against MCF7 cells.

Quantitative proteomics identifies PTP1B as modulator of B cell antigen receptor signaling

This study analyses the function of the protein tyrosine phosphatase 1B identifying its binding partners and dephosphorylation targets for modulating B cell antigen receptor signaling.

B cell antigen receptor (BCR) signaling is initiated by protein kinases and limited by counteracting phosphatases that currently are less well studied in their regulation of BCR signaling. Here, we used the B cell line Ramos to identify and quantify human B cell signaling components. Specifically, a protein tyrosine phosphatase profiling revealed a high expression of the protein tyrosine phosphatase 1B (PTP1B) in Ramos and human naïve B cells. The loss of PTP1B leads to increased B cell activation. Through substrate trapping in combination with quantitative mass spectrometry, we identified 22 putative substrates or interactors of PTP1B. We validated Igα, CD22, PLCγ1/2, CBL, BCAP, and APLP2 as specific substrates of PTP1B in Ramos B cells. The tyrosine kinase BTK and the two adaptor proteins GRB2 and VAV1 were identified as direct binding partners and potential substrates of PTP1B. We showed that PTP1B dephosphorylates the inhibitory receptor protein CD22 at phosphotyrosine 807. We conclude that PTP1B negatively modulates BCR signaling by dephosphorylating distinct phosphotyrosines in B cell-specific receptor proteins and various downstream signaling components.

Expedition of sulfur-containing heterocyclic derivatives as cytotoxic agents in medicinal chemistry: A decade update

This review article proposes a comprehensive report of the design strategies engaged in the development of various sulfur-bearing cytotoxic agents. The outcomes of various studies depict that the sulfur heterocyclic framework is a fundamental structure in diverse synthetic analogs representing a myriad scope of therapeutic activities. A number of five-, six- and seven-membered sulfur-containing heterocyclic scaffolds, such as thiazoles, thiadiazoles, thiazolidinediones, thiophenes, thiopyrans, benzothiazoles, benzothiophenes, thienopyrimidines, simple and modified phenothiazines, and thiazepines have been discussed. The subsequent studies of the derivatives unveiled their cytotoxic effects through multiple mechanisms (viz. inhibition of tyrosine kinases, topoisomerase I and II, tubulin, COX, DNA synthesis, and PI3K/Akt and Raf/MEK/ERK signaling pathways), and several others. Thus, our concise illustration explains the design strategy and anticancer potential of these five- and six-membered sulfur-containing heterocyclic molecules along with a brief outline on seven-membered sulfur heterocycles. The thorough assessment of antiproliferative activities with the reference drug allows a proficient assessment of the structure-activity relationships (SARs) of the diversely synthesized molecules of the series.

Inhibitory Effects of Secondary Metabolites from the Lichen Stereocaulon evolutum on Protein Tyrosine Phosphatase 1B

Protein tyrosine phosphatase 1B plays a significant role in type 2 diabetes mellitus and other diseases and is therefore considered a new drug target. Within this study, an acetone extract from the lichen Stereocaulon evolutum was identified to possess strong protein tyrosine phosphatase 1B inhibition in a cell-free assay (IC₅₀ of 11.8 µg/mL). Fractionation of this bioactive extract led to the isolation of seven known molecules belonging to the depsidones and the related diphenylethers and one new natural product, i.e., 3-butyl-3,7-dihydroxy-5-methoxy-1(3H)-isobenzofurane. The isolated compounds were evaluated for their inhibition of protein tyrosine phosphatase 1B. Two depsidones, lobaric acid and norlobaric acid, and the diphenylether anhydrosakisacaulon A potently inhibited protein tyrosine phosphatase 1B with IC₅₀ values of 12.9, 15.1, and 16.1 µM, respectively, which is in the range of the protein tyrosine phosphatase 1B inhibitory activity of the positive control ursolic acid (IC₅₀ of 14.4 µM). Molecular simulations performed on the eight compounds showed that i) a contact between the molecule and the four main regions of the protein is required for inhibitory activity, ii) the relative rigidity of the depsidones lobaric acid and norlobaric acid and the reactivity related to hydrogen bond donors or acceptors, which interact with protein tyrosine phosphatase 1B key amino acids, are involved in the bioactivity on protein tyrosine phosphatase 1B, iii) the cycle opening observed for diphenylethers decreased the inhibition, except for anhydrosakisacaulon A where its double bond on C-8 offsets this loss of activity, iv) the function present at C-8 is a determinant for the inhibitory effect on protein tyrosine phosphatase 1B, and v) the more hydrogen bonds with Arg221 there are, the more anchorage is favored.

Junctional ER Organization Affects Mechanotransduction at Cadherin-Mediated Adhesions

Cadherin-mediated adhesions (also known as adherens junctions) are adhesive complexes that connect neighboring cells in a tissue. While the role of the actin cytoskeleton in withstanding tension at these sites of contact is well documented, little is known about the involvement of microtubules and the associated endoplasmic reticulum (ER) network in cadherin mechanotransduction. Therefore, we investigated how the organization of ER extensions in close proximity of cadherin-mediated adhesions can affect such complexes, and vice versa. Here, we show that the extension of the ER to cadherin-mediated adhesions is tension dependent and appears to be cadherin-type specific. Furthermore, the different structural organization of the ER/microtubule network seems to affect the localization of ER-bound PTP1B at cadherin-mediated adhesions. This phosphatase is involved in the modulation of vinculin, a molecular clutch which enables differential engagement of the cadherin-catenin layer with the actomyosin cytoskeleton in response to tension. This suggests a link between structural organization of the ER/microtubule network around cadherin-specific adhesions, to control the mechanotransduction of adherens junctions by modulation of vinculin conformational state.

The PTP1B mutant PTP1B∆2-4 is a positive regulator of the JAK/STAT signalling pathway in Hodgkin lymphoma

The neoplastic Hodgkin/Reed-Sternberg (HRS) cells of classical Hodgkin lymphoma (cHL) depend on chronic activation of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signalling pathways to maintain survival and proliferation. Accumulating reports highlight the importance of the inactivation or reduced expression of negative JAK/STAT regulators such as the protein-tyrosine phosphatase 1B (PTP1B/PTPN1) in this process. Various PTPN1 mRNA variants as well as truncated PTP1B proteins were identified in cHL cell lines and primary cHL tumour samples. These PTPN1 mRNA variants lack either one or several exon sequences and therefore render these PTP1B variants catalytically inactive. Here, we show that one of these mutants, PTP1B∆2-4, is not only a catalytically inactive variant, but also augmented the IL-4-induced JAK/STAT activity similar to the recently reported PTP1B∆6 splice variant. Moreover, while PTP1B∆6 diminished the activity and protein levels of PTP1BWT, PTP1BWT remained unaffected by PTP1B∆2-4, arguing for different molecular mechanisms of JAK/STAT modulation by PTP1B∆6 and PTP1B∆2-4. Collectively, these data indicate that PTPN1 variants missing one or more exon sequences originated either from alternative splicing or from gene mutation, create PTP1B gain-of-function variants with oncogenic potential by augmenting JAK/STAT signalling in cHL.