Mechanism of inhibition of protein-tyrosine phosphatases by vanadate and pervanadate

Mechanism of the antimicrobial activity induced by phosphatase inhibitor sodium ortho-vanadate

The present study describes a novel antimicrobial mechanism based on Sodium Orthovanadate (SOV), an alkaline phosphatase inhibitor. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM) were employed to examine the surface morphologies of the test organism, Escherichia coli (E. coli), during various antibacterial phases. Our results indicated that SOV kills bacteria by attacking cell wall growth and development, leaving E. coli's outer membrane intact. Our antimicrobial test indicated that the MIC of SOV for both E. coli and Lactococcus lactis (L. lactis) is 40 μM. A combination of quantum mechanical calculations and vibrational spectroscopy revealed that divanadate from SOV strongly coordinates with Ca2+ and Mg2+, which are the activity centers for the phosphatase that regulates bacterial cell wall synthesis. The current study is the first to propose the antibacterial mechanism caused by SOV attacking cell wall.

Real-time monitoring of dephosphorylation process of phosphopeptide and rapid assay of PTP1B activity based on a 100 MHz QCM biosensing platform

The misregulation of protein phosphatases is a key factor in the development of many human diseases, notably cancers. Here, based on a 100 MHz quartz crystal microbalance (QCM) biosensing platform, the dephosphorylation process of phosphopeptide (P-peptide) caused by protein tyrosine phosphatase 1B (PTP1B) was monitored in real time for the first time and PTP1B activity was assayed rapidly and sensitively. The QCM chip, coated with a gold (Au) film, was used to immobilized thiol-labeled single-stranded 5'-phosphate-DNAs (P-DNA) through Au-S bond. The P-peptide, specific to PTP1B, was then connected to the P-DNA via chelation between Zr4+ and phosphate groups. When PTP1B was injected into the QCM flow cell where the P-peptide/Zr4+/MCH/P-DNA/Au chip was placed, the P-peptide was dephosphorylated and released from the Au chip surface, resulting in an increase in the frequency of the QCM Au chip. This allowed the real-time monitoring of the P-peptide dephosphorylation process and sensitive detection of PTP1B activity within 6 min with a linear detection range of 0.01-100 pM and a detection limit of 0.008 pM. In addition, the maximum inhibitory ratios of inhibitors were evaluated using this proposed 100 MHz QCM biosensor. The developed 100 MHz QCM biosensing platform shows immense potential for early diagnosis of diseases related to protein phosphatases and the development of drugs targeting protein phosphatases.

The receptor protein tyrosine phosphatase PTPRK promotes intestinal repair and catalysis-independent tumour suppression

PTPRK is a receptor tyrosine phosphatase that is linked to the regulation of growth factor signalling and tumour suppression. It is stabilized at the plasma membrane by trans homophilic interactions upon cell-cell contact. PTPRK regulates cell-cell adhesion but is also reported to regulate numerous cancer-associated signalling pathways. However, the signalling mechanism of PTPRK remains to be determined. Here, we find that PTPRK regulates cell adhesion signalling, suppresses invasion and promotes collective, directed migration in colorectal cancer cells. In vivo, PTPRK supports recovery from inflammation-induced colitis. In addition, we confirm that PTPRK functions as a tumour suppressor in the mouse colon and in colorectal cancer xenografts. PTPRK regulates growth factor and adhesion signalling, and suppresses epithelial to mesenchymal transition (EMT). Contrary to the prevailing notion that PTPRK directly dephosphorylates EGFR, we find that PTPRK regulation of both EGFR and EMT is independent of its catalytic function. This suggests that additional adaptor and scaffold functions are important features of PTPRK signalling.

Development of Novel Phosphonodifluoromethyl-Containing Phosphotyrosine Mimetics and a First-In-Class, Potent, Selective, and Bioavailable Inhibitor of Human CDC14 Phosphatases

Together with protein tyrosine kinases, protein tyrosine phosphatases (PTPs) control protein tyrosine phosphorylation and regulate numerous cellular functions. Dysregulated PTP activity is associated with the onset of multiple human diseases. Nevertheless, understanding of the physiological function and disease biology of most PTPs remains limited, largely due to the lack of PTP-specific chemical probes. In this study, starting from a well-known nonhydrolyzable phosphotyrosine (pTyr) mimetic, phosphonodifluoromethyl phenylalanine (F2Pmp), we synthesized 7 novel phosphonodifluoromethyl-containing bicyclic/tricyclic aryl derivatives with improved cell permeability and potency toward various PTPs. Furthermore, with fragment- and structure-based design strategies, we advanced compound 9 to compound 15, a first-in-class, potent, selective, and bioavailable inhibitor of human CDC14A and B phosphatases. This study demonstrates the applicability of the fragment-based design strategy in creating potent, selective, and bioavailable PTP inhibitors and provides a valuable probe for interrogating the biological roles of hCDC14 phosphatases and assessing their potential for therapeutic interventions.

THEMIS2 Impairs Antitumor Activity of NK Cells by Suppressing Activating NK Receptor Signaling

NK cells are cytotoxic innate lymphocytes that play a critical role in antitumor immunity. NK cells recognize target cells by using a repertoire of activating NK receptors and exert the effector functions. Although the magnitude of activation signals through activating NK receptors controls NK cell function, it has not been fully understood how these activating signals are modulated in NK cells. In this study, we found that a scaffold protein, THEMIS2, inhibits activating NK receptor signaling. Overexpression of THEMIS2 attenuated the effector function of human NK cells, whereas knockdown of THEMIS2 enhanced it. Mechanistically, THEMIS2 binds to GRB2 and phosphorylated SHP-1 and SHP-2 at the proximity of activating NK receptors DNAM-1 and NKG2D. Knockdown of THEMIS2 in primary human NK cells promoted the effector functions. Furthermore, Themis2-deficient mice showed low metastatic burden in an NK cell-dependent manner. These findings demonstrate that THEMIS2 has an inhibitory role in the antitumor activity of NK cells, suggesting that THEMIS2 might be a potential therapeutic target for NK cell-mediated cancer immunotherapy.

DNA damage-induced allosteric activation of protein phosphatase PP1:NIPP1 through Src kinase-induced circularization of NIPP1

Protein phosphatase-1 (PP1) complexed to nuclear inhibitor of PP1 (NIPP1) limits DNA repair through dephosphorylation of NIPP1-recruited substrates. However, the PP1:NIPP1 holoenzyme is completely inactive under basal conditions, hinting at a DNA damage-regulated activation mechanism. Here, we report that DNA damage caused the activation of PP1:NIPP1 after a time delay of several hours through phosphorylation of NIPP1 at the C-terminal tyrosine 335 (Y335) by a Src-family kinase. PP1:NIPP1 activation partially resulted from the dissociation of the C terminus of NIPP1 from the active site of PP1. In addition, the released Y335-phosphorylated C terminus interacted with the N terminus of NIPP1 to enhance substrate recruitment by the flanking forkhead-associated (FHA) domain. Constitutive activation of PP1:NIPP1 by knock-in of a phospho-mimicking (Y335E) NIPP1 mutant led to the hypo-phosphorylation of FHA ligands and an accumulation of DNA double-strand breaks. Our data indicate that PP1:NIPP1 activation through circularization of NIPP1 is a late response to DNA damage that contributes to the timely recovery from damage repair.

THEMIS promotes T cell development and maintenance by rising the signaling threshold of the inhibitory receptor BTLA

The current paradigm about the function of T cell immune checkpoints is that these receptors switch on inhibitory signals upon cognate ligand interaction. We here revisit this simple switch model and provide evidence that the T cell lineage protein THEMIS enhances the signaling threshold at which the immune checkpoint BTLA (B- and T-lymphocyte attenuator) represses T cell responses. THEMIS is recruited to the cytoplasmic domain of BTLA and blocks its signaling capacity by promoting/stabilizing the oxidation of the catalytic cysteine of the tyrosine phosphatase SHP-1. In contrast, THEMIS has no detectable effect on signaling pathways regulated by PD-1 (Programmed cell death protein 1), which depend mainly on the tyrosine phosphatase SHP-2. BTLA inhibitory signaling is tuned according to the THEMIS expression level, making CD8+ T cells more resistant to BTLA-mediated inhibition than CD4+ T cells. In the absence of THEMIS, the signaling capacity of BTLA is exacerbated, which results in the attenuation of signals driven by the T cell antigen receptor and by receptors for IL-2 and IL-15, consequently hampering thymocyte positive selection and peripheral CD8+ T cell maintenance. By characterizing the pivotal role of THEMIS in restricting the transmission of BTLA signals, our study suggests that immune checkpoint operability is conditioned by intracellular signal attenuators.

Hyper-accumulation of vanadium in animals: Two sponges compete with urochordates

Vanadium (V) concentrations in organisms are usually very low. To date, among animals, only some urochordate and annelid species contain very high levels of V in their tissues. A new case of hyper-accumulation of V in a distinct animal phylum (Porifera), namely, the two homoscleromorph sponge species Oscarella lobularis and O. tuberculata is reported. The measured concentrations (up to 30 g/kg dry weight) exceed those reported previously and are not found in all sponge classes. In both Oscarella species, V is mainly accumulated in the surface tissues, and in mesohylar cells, as V(IV), before being partly reduced to V(III) in the deeper tissues. Candidate genes from Bacteria and sponges have been identified as possibly being involved in the metabolism of V. This finding provides clues for the development of bioremediation strategies in marine ecosystems and/or bioinspired processes to recycle this critical metal.

The Norm of Reciprocity in Intergroup Context: A Normative-Identity Model

Reciprocity, regarded as a fundamental psychological phenomenon, may underlie a wide range of interpersonal and intergroup behaviors. Various disciplines such as behavioral economics, anthropology, sociology, and psychology as well documented how reciprocity is a strong determinant of human behavior. On the other hand, less is known about intergroup reciprocity, its functions and consequences as well as the psychological mechanisms through which these effects manifest, remain mostly unknown. In this paper, we propose a model to understand how the reciprocity norm operates in the intergroup contexts, through employing the Personal Norm of Reciprocity model (Perugini et al., 2003) and the Self-Categorization Theory (Turner et al., 1987). We suggest that the conditions that give rise to intergroup reciprocal behavior are ingroup identification, labeling outgroup behavior as a favor or transgression, and the internalization of the reciprocity norm. We also propose that the intergroup outcomes, such as ingroup favoritism, discrimination, collective action, and conflict resolution, might become more understandable when taking into account the reciprocity as an explanatory variable.

Association of urinary and seminal plasma vanadium concentrations with semen quality: A repeated-measures study of 1135 healthy men

Although animal studies have shown the reproductive toxicity of vanadium, less is known about its effects on semen quality in humans. Among 1135 healthy men who were screened as potential semen donors, we investigated the relationships of semen quality with urinary and seminal plasma vanadium levels via inductively coupled plasma-mass spectrometry (ICP-MS). Spearman rank correlation tests and linear regression models were used to assess the correlations between average urinary and within-individual pooled seminal plasma vanadium concentrations (n = 1135). We utilized linear mixed-effects models to evaluate the associations of urinary and seminal plasma vanadium levels (n = 1135) with repeated sperm quality parameters (n = 5576). Seminal plasma vanadium concentrations were not significantly correlated with urinary vanadium concentrations (r = 0.03). After adjusting for possible confounders, we observed inverse relationships of within-individual pooled seminal plasma vanadium levels with total count, semen volume, and sperm concentration (all P values for trend < 0.05). Specifically, subjects in the highest (vs. lowest) tertile of seminal plasma vanadium concentrations had - 11.3% (-16.4%, -5.9%), - 11.1% (-19.1%, -2.4%), and - 20.9% (-29.0%, -11.8%) lower sperm volume, concentration, and total count, respectively; moreover, urinary vanadium levels appeared to be negatively associated with sperm motility. These relationships showed monotonically decreasing dose-response patterns in the restricted cubic spline analyses. Our results demonstrated a poor correlation between urinary and seminal plasma levels of vanadium, and elevated vanadium concentrations in urine and seminal plasma may be adversely related to male semen quality.

Vanadium Complexes with Thioanilide Derivatives of Amino Acids: Inhibition of Human Phosphatases and Specificity in Various Cell Models of Metabolic Disturbances

In the text, the synthesis and characteristics of the novel ONS-type vanadium (V) complexes with thioanilide derivatives of amino acids are described. They showed the inhibition of human protein tyrosine phosphatases (PTP1B, LAR, SHP1, and SHP2) in the submicromolar range, as well as the inhibition of non-tyrosine phosphatases (CDC25A and PPA2) similar to bis(maltolato)oxidovanadium(IV) (BMOV). The ONS complexes increased [14C]-deoxy-D-glucose transport into C2C12 myocytes, and one of them, VC070, also enhanced this transport in 3T3-L1 adipocytes. These complexes inhibited gluconeogenesis in hepatocytes HepG2, but none of them decreased lipid accumulation in the non-alcoholic fatty liver disease model using the same cells. Compared to the tested ONO-type vanadium complexes with 5-bromosalicylaldehyde and substituted benzhydrazides as Schiff base ligand components, the ONS complexes revealed stronger inhibition of protein tyrosine phosphatases, but the ONO complexes showed greater activity in the cell models in general. Moreover, the majority of the active complexes from both groups showed better effects than VOSO4 and BMOV. Complexes from both groups activated AKT and ERK signaling pathways in hepatocytes to a comparable extent. One of the ONO complexes, VC068, showed activity in all of the above models, including also glucose utilizatiand ONO Complexes are Inhibitors ofon in the myocytes and glucose transport in insulin-resistant hepatocytes. The discussion section explicates the results within the wider scope of the knowledge about vanadium complexes.

Effects of the tetravanadate [V4O12]4- anion on the structural, magnetic, and biological properties of copper/phenanthroline complexes

The aim to access linked tetravanadate [V4O12]4- anion with mixed copper(II) complexes, using α-amino acids and phenanthroline-derived ligands, resulted in the formation of four copper(II) complexes [Cu(dmb)(Gly)(OH2)]2[Cu(dmb)(Gly)]2[V4O12]·9H2O (1) [Cu(dmb)(Lys)]2[V4O12]·8H2O (2), [Cu(dmp)2][V4O12]·C2H5OH·11H2O (3), and [Cu(dmp)(Gly)Cl]·2H2O (4), where dmb = 4,4'-dimethioxy-2,2'-bipyridine; Gly = glycine; Lys = lysine; and dmp = 2,9-dimethyl-1,10-phenanthroline. The [V4O12]4- anion is functionalized with mixed copper(II) units in 1 and 2; while in 3, it acts as a counterion of two [Cu(dmp)]2+ units. Compound 4 crystallized as a unit that did not incorporate the vanadium cluster. All compounds present magnetic couplings arising from Cu⋯O/Cu⋯Cu bridges. Stability studies of water-soluble 3 and 4 by UV-Vis spectroscopy in cell culture medium confirmed the robustness of 3, while 4 appears to undergo ligand scrambling over time, resulting partially in the stable species [Cu(dmp)2]+ that was also identified by electrospray ionization mass spectrometry at m/z = 479. The in vitro cytotoxicity activity of 3 and 4 was determined in six cancer cell lines; the healthy cell line COS-7 was also included for comparative purposes. MCF-7 cells were more sensitive to compound 3 with an IC50 value of 12 ± 1.2 nmol. The tested compounds did not show lipid peroxidation in the TBARS assay, ruling out a mechanism of action via reactive oxygen species formation. Both compounds inhibited cell migration at 5 µM in wound-healing assays using MCF-7, PC-3, and SKLU-1 cell lines, opening a new window to study the anti-metastatic effect of mixed vanadium-copper(II) systems.

Phosphoproteomics and morphology of stored human red blood cells treated by protein tyrosine phosphatases inhibitor

ABSTRACT

The process of protein phosphorylation is involved in numerous cell functions. In particular, phosphotyrosine (pY) has been reported to play a role in red blood cell (RBC) functions, including the cytoskeleton organization. During their storage before transfusion, RBCs suffer from storage lesions that affect their energy metabolism and morphology. This study investigated the relationship between pY and the storage lesions. To do so, RBCs were treated (in the absence of calcium) with a protein tyrosine phosphatase inhibitor (orthovanadate [OV]) to stimulate phosphorylation and with 3 selective kinase inhibitors (KIs). Erythrocyte membrane proteins were studied by western blot analyses and phosphoproteomics (data are available via ProteomeXchange with identifier PXD039914) and cell morphology by digital holographic microscopy. The increase of pY triggered by OV treatment (inducing a global downregulation of pS and pT) disappeared during the storage. Phosphoproteomic analysis identified 609 phosphoproteins containing 1752 phosphosites, of which 41 pY were upregulated and 2 downregulated by OV. After these phosphorylation processes, the shape of RBCs shifted from discocytes to spherocytes, and the addition of KIs partially inhibited this transition. The KIs modulated either pY or pS and pT via diverse mechanisms related to cell shape, thereby affecting RBC morphology. The capacity of RBCs to maintain their function is central in transfusion medicine, and the presented results contribute to a better understanding of RBC biology.

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.

Histological and Memory Alterations in an Innovative Alzheimer's Disease Animal Model by Vanadium Pentoxide Inhalation

Background

Previous work from our group has shown that chronic exposure to Vanadium pentoxide (V2O5) causes cytoskeletal alterations suggesting that V2O5 can interact with cytoskeletal proteins through polymerization and tyrosine phosphatases inhibition, causing Alzheimer's disease (AD)-like hippocampal cell death.

Objective

This work aims to characterize an innovative AD experimental model through chronic V2O5 inhalation, analyzing the spatial memory alterations and the presence of neurofibrillary tangles (NFTs), amyloid-β (Aβ) senile plaques, cerebral amyloid angiopathy, and dendritic spine loss in AD-related brain structures.

Methods

20 male Wistar rats were divided into control (deionized water) and experimental (0.02 M V2O5 1 h, 3/week for 6 months) groups (n = 10). The T-maze test was used to assess spatial memory once a month. After 6 months, histological alterations of the frontal and entorhinal cortices, CA1, subiculum, and amygdala were analyzed by performing Congo red, Bielschowsky, and Golgi impregnation.

Results

Cognitive results in the T-maze showed memory impairment from the third month of V2O5 inhalation. We also noted NFTs, Aβ plaque accumulation in the vascular endothelium and pyramidal neurons, dendritic spine, and neuronal loss in all the analyzed structures, CA1 being the most affected.

Conclusions

This model characterizes neurodegenerative changes specific to AD. Our model is compatible with Braak AD stage IV, which represents a moment where it is feasible to propose therapies that have a positive impact on stopping neuronal damage.

High-Throughput Discovery and Characterization of Covalent Inhibitors for Protein Tyrosine Phosphatases

Covalent inhibition has gained increasing interest in targeting the undruggable protein tyrosine phosphatases (PTPs). However, a systematic method for discovering and characterizing covalent PTP inhibitors has yet to be established. Here, we describe a workflow involving high-throughput screening of covalent fragment libraries and a novel biochemical assay that enables the acquisition of kinetics parameters of PTP inhibition by covalent inhibitors with higher throughput.

The importance of including the C-terminal domain of PTP1B1-400 to identify potential antidiabetic inhibitors

In the present work, we studied the inhibitory and kinetic implications of classical PTP1B inhibitors (chlorogenic acid, ursolic acid, suramin) using three enzyme constructs (hPTP1B_1-285, hPTP1B_1-321, and hPTP1B_1-400). The results indicate that the unstructured region of PTP1B (300-400 amino acids) is very important both to obtain optimal inhibitory results and propose classical inhibition mechanisms (competitive or non-competitive) through kinetic studies. The IC₅₀ calculated for ursolic acid and suramin using hPTP1B_1-400 are around four and three times lower to the short form of the enzyme, the complete form of PTP1B, the one found in the cytosol (in vivo). On the other hand, we highlight the studies of enzymatic kinetics using the hPTP1B_1-400 to know the type of enzymatic inhibition and to be able to direct docking studies, where the unstructured region of the enzyme can be one more option for binding compounds with inhibitory activity.

Biological noncovalent N/O⋯V interactions: insights from theory and protein data bank analyses

Computations at the PBE0-D3/def2-TZVP level of theory in conjunction with a Protein Data Bank (PDB) survey have provided first time evidence of favorable noncovalent interactions between ADP metavanadate (VO4) and ADP orthovanadate (VO5) and electron rich atoms. These involve a σ-hole present in the V atom and the lone pairs belonging to (i) protein residues (e.g., serine (SER), glutamate (GLU) or histidine (HIS)), (ii) backbone carbonyl groups and (iii) water molecules. A computational study has been carried out to rationalize the physical nature and directionality of the interaction in addition to its plausible biological role. The results reported herein are expected to have an impact in the fields of medicinal chemistry, bioinorganic chemistry and chemical biology.

Enzyme PTP-1B Inhibition Studies by Vanadium Metal Complexes: a Kinetic Approach

The medical field now needs more novel drugs to treat obesity and type-2 diabetes mellitus (T2D) than ever before. Obesity and T2D are both characterized by resistance to the hormones leptin and insulin. PTP-1B is a promising target for drug growth, as strong genetic, pharmacological, and biochemical evidence points to the possibility of treating diabetes and obesity by blocking the PTP-1B enzyme. Studies have also found that PTP-1B is overexpressed in patients with diabetes and obesity, suggesting that inhibiting PTP-1B may be a useful technique in their care. There are no clinically used PTP-1B inhibitors, despite the fact that numerous naturally occurring PTP-1B inhibitors have demonstrated great therapeutic promise. This is most likely due to their low activity or lack of selectivity. It is still important to look for more effective and focused PTP-1B inhibitors. A few organovanadium metal complexes were synthesized and characterized, and binding studies on vanadium complexes with PTP-B were also performed using fluorescence emission spectroscopy. Additionally, we theoretically (molecular modeling) and experimentally (enzyme kinetics) examined the PTP-1B inhibitory effects of these vanadium metal complexes and found that they have excellent PTP-1B inhibitory properties.

Identification and characterization of an ectophosphatase activity involved in Acanthamoeba castellanii adhesion to host cells

Acanthamoeba castellanii is a free-living amoeba and an opportunistic pathogen for humans that can cause encephalitis and, more commonly, Acanthamoeba keratitis. During its life cycle, A. castellanii may present as proliferative and infective trophozoites or resistant cysts. The adhesion of trophozoites to host cells is a key first step in the pathogenesis of infection. A major virulence protein of Acanthamoeba is a mannose-binding protein (MBP) that mediates the adhesion of amoebae to cell surfaces. Ectophosphatases are ecto-enzymes that can dephosphorylate extracellular substrates and have already been described in several microorganisms. Regarding their physiological roles, there is consistent evidence that ectophosphatase activities play an important role in parasite-host interactions. In the present work, we identified and biochemically characterized the ectophosphatase activity of A. castellanii. The ectophosphatase activity is acidic, stimulated by magnesium, cobalt and nickel, and presents the following apparent kinetic parameters: Km = 2.12 ± 0.54 mM p-NPP and Vmax = 26.12 ± 2.53 nmol p-NP × h-1 × 10-6 cells. We observed that sodium orthovanadate, ammonium molybdate, sodium fluoride, and inorganic phosphate are able to inhibit ectophosphatase activity. Comparing the two stages of the A. castellanii lifecycle, ectophosphatase activity is significantly higher in trophozoites than in cysts. The ectophosphatase activity is stimulated by mannose residues and is significantly increased when trophozoites interact with LLC-MK2 cells. The inhibition of ectophosphatase by pretreatment with sodium orthovanadate also inhibits the adhesion of trophozoites to epithelial cells. These results allow us to conclude that the ectophosphatase activity of A. castellanii is somehow important for the adhesion of trophozoites to their host cells. According to our data, we believe that the activation of MBP by mannose residues triggers the stimulation of ectophosphatase activity to facilitate the adhesion process.

The Deficits of Insulin Signal in Alzheimer's Disease and the Mechanisms of Vanadium Compounds in Curing AD

Vanadium is a well-known essential trace element, which usually exists in oxidation states in the form of a vanadate cation intracellularly. The pharmacological study of vanadium began with the discovery of its unexpected inhibitory effect on ATPase. Thereafter, its protective effects on β cells and its ability in glucose metabolism regulation were observed from the vanadium compound, leading to the application of vanadium compounds in clinical trials for curing diabetes. Alzheimer's disease (AD) is the most common dementia disease in elderly people. However, there are still no efficient agents for treating AD safely to date. This is mainly because of the complexity of the pathology, which is characterized by senile plaques composed of the amyloid-beta (Aβ) protein in the parenchyma of the brain and the neurofibrillary tangles (NFTs), which are derived from the hyperphosphorylated tau protein in the neurocyte, along with mitochondrial damage, and eventually the central nervous system (CNS) atrophy. AD was also illustrated as type-3 diabetes because of the observations of insulin deficiency and the high level of glucose in cerebrospinal fluid (CSF), as well as the impaired insulin signaling in the brain. In this review, we summarize the advances in applicating the vanadium compound to AD treatment in experimental research and point out the limitations of the current study using vanadium compounds in AD treatment. We hope this will help future studies in this field.

Vanadium compounds as antiparasitic agents: An approach to their mechanisms of action

BACKGROUND

Parasitic infections are a public health problem since they have high morbidity and mortality worldwide. In parasitosis such as malaria, leishmaniasis and trypanosomiasis it is necessary to develop new compounds for their treatment since an increase in drug resistance and toxic effects have been observed. Therefore, the use of different compounds that couple vanadium in their structure and that have a broad spectrum against different parasites have been proposed experimentally.

OBJECTIVE

Report the mechanisms of action exerted by vanadium in different parasites.

CONCLUSION

In this review, some of the targets that vanadium compounds have were identified and it was observed that they have a broad spectrum against different parasites, which represents an advance to continue investigating therapeutic options.

Biological Consequences of Vanadium Effects on Formation of Reactive Oxygen Species and Lipid Peroxidation

Lipid peroxidation (LPO), a process that affects human health, can be induced by exposure to vanadium salts and compounds. LPO is often exacerbated by oxidation stress, with some forms of vanadium providing protective effects. The LPO reaction involves the oxidation of the alkene bonds, primarily in polyunsaturated fatty acids, in a chain reaction to form radical and reactive oxygen species (ROS). LPO reactions typically affect cellular membranes through direct effects on membrane structure and function as well as impacting other cellular functions due to increases in ROS. Although LPO effects on mitochondrial function have been studied in detail, other cellular components and organelles are affected. Because vanadium salts and complexes can induce ROS formation both directly and indirectly, the study of LPO arising from increased ROS should include investigations of both processes. This is made more challenging by the range of vanadium species that exist under physiological conditions and the diverse effects of these species. Thus, complex vanadium chemistry requires speciation studies of vanadium to evaluate the direct and indirect effects of the various species that are present during vanadium exposure. Undoubtedly, speciation is important in assessing how vanadium exerts effects in biological systems and is likely the underlying cause for some of the beneficial effects reported in cancerous, diabetic, neurodegenerative conditions and other diseased tissues impacted by LPO processes. Speciation of vanadium, together with investigations of ROS and LPO, should be considered in future biological studies evaluating vanadium effects on the formation of ROS and on LPO in cells, tissues, and organisms as discussed in this review.

Topical vanadate improves tensile strength and alters collagen organisation of excisional wounds in a mouse model

Wound dehiscence, oftentimes a result of the poor tensile strength of early healing wounds, is a significant threat to the post-operative patient, potentially causing life-threatening complications. Vanadate, a protein tyrosine phosphatase inhibitor, has been shown to alter the organisation of deposited collagen in healing wounds and significantly improve the tensile strength of incisional wounds in rats. In this study, we sought to explore the effects of locally administered vanadate on tensile strength and collagen organisation in both the early and remodelling phases of excisional wound healing in a murine model. Wild-type mice underwent stented excisional wounding on their dorsal skin and were divided equally into three treatment conditions: vanadate injection, saline injection control and an untreated control. Tensile strength testing, in vivo suction Cutometer analysis, gross wound measurements and histologic analysis were performed during healing, immediately upon wound closure, and after 4 weeks of remodelling. We found that vanadate treatment significantly increased the tensile strength of wounds and their stiffness relative to control wounds, both immediately upon healing and into the remodelling phase. Histologic analysis revealed that these biomechanical changes were likely the result of increased collagen deposition and an altered collagen organisation composed of thicker and distinctly organised collagen bundles. Given the risk that dehiscence poses to all operative patients, vanadate presents an interesting therapeutic avenue to improve the strength of post-operative wounds and unstable chronic wounds to reduce the risk of dehiscence.

Reversible Conversion of Disulfide/Dithiolate Occurring at a Vanadium(IV) Center: A Biomimetic System for Redox Exchange in Vanabin

Ascidians use a class of cysteine-rich proteins generally referred to as vanabins to reduce vanadium ions, one of the many biological processes that involve the redox conversion between disulfide and dithiolate mediated by transition-metal ions. To further understand the nature of disulfide/dithiolate exchange facilitated by a vanadium center, we report herein a six-coordinate non-oxido V^IV complex containing an unbound disulfide moiety, [V^IV(PS3″)(PS1″^S-S)] (1) (PS3″ = [P(C₆H₃-3-Me₃Si-2-S)₃]^3-, where PS1″^S-S is a disulfide form of PS3″). Complex 1 is obtained from a reaction of previously reported [V^V(PS3″)(PS2″S^H)] (2) (PS2″S^H = [P(C₆H₃-3-Me₃Si-2-SH)(C₆H₃-3-Me₃Si-2-S)₂] with TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidin-1-yl)oxyl) via hydrogen atom transfer. Importantly, complex 1 can be reduced by two electrons to form an eight-coordinate V^IV complex, [V^IV(PS3″)₂]^2- (4). The reaction can be reversed through a two-electron oxidation process to regenerate complex 1. The redox pathways both proceed through a common intermediate, [V(PS3″)₂]^- (3), that has been previously reported as a resonance form of V^V-dithiolate and a V^IV-(thiolate)(thiyl-radical) species. This work demonstrates an unprecedented example of reversible disulfide/dithiolate interconversion mediated by a V^IV center, as well as provides insights into understanding the function of V^V reductases in vanabins.

Role of the membrane anchor in the regulation of Lck activity

Theoretical work suggests that collective spatiotemporal behavior of integral membrane proteins should be modulated by boundary lipids sheathing their membrane anchors. Here, we show evidence for this prediction while investigating the mechanism for maintaining a steady amount of the active form of integral membrane protein Lck kinase (Lck_A) by Lck trans-autophosphorylation regulated by the phosphatase CD45. We used super-resolution microscopy, flow cytometry, and pharmacological and genetic perturbation to gain insight into the spatiotemporal context of this process. We found that Lck_A is generated exclusively at the plasma membrane, where CD45 maintains it in a ceaseless dynamic equilibrium with its unphosphorylated precursor. Steady Lck_A shows linear dependence, after an initial threshold, over a considerable range of Lck expression levels. This behavior fits a phenomenological model of trans-autophosphorylation that becomes more efficient with increasing Lck_A. We then challenged steady Lck_A formation by genetically swapping the Lck membrane anchor with structurally divergent ones, such as that of Src or the transmembrane domains of LAT, CD4, palmitoylation-defective CD4 and CD45 that were expected to drastically modify Lck boundary lipids. We observed small but significant changes in Lck_A generation, except for the CD45 transmembrane domain that drastically reduced Lck_A due to its excessive lateral proximity to CD45. Comprehensively, Lck_A formation and maintenance can be best explained by lipid bilayer critical density fluctuations rather than liquid-ordered phase-separated nanodomains, as previously thought, with "like/unlike" boundary lipids driving dynamical proximity and remoteness of Lck with itself and with CD45.

Blockade of the immunosuppressive KIR2DL5/PVR pathway elicits potent human NK cell-mediated antitumor immunity

Cancer immunotherapy targeting the TIGIT/PVR pathway is currently facing challenges. KIR2DL5, a member of the human killer cell, immunoglobulin-like receptor (KIR) family, has recently been identified as another binding partner for PVR. The biology and therapeutic potential of the KIR2DL5/PVR pathway are largely unknown. Here we report that KIR2DL5 was predominantly expressed on human NK cells with mature phenotype and cytolytic function and that it bound to PVR without competition with the other 3 known PVR receptors. The interaction between KIR2DL5 on NK cells and PVR on target cells induced inhibitory synapse formation, whereas new monoclonal antibodies blocking the KIR2DL5-PVR interaction robustly augmented the NK cytotoxicity against PVR+ human tumors. Mechanistically, both intracellular ITIM and ITSM of KIR2DL5 underwent tyrosine phosphorylation after engagement, which was essential for KIR2DL5-mediated NK suppression by recruiting SHP-1 and/or SHP-2. Subsequently, ITIM/SHP-1/SHP-2 and ITSM/SHP-1 downregulated the downstream Vav1/ERK1/2/p90RSK/NF-κB signaling. KIR2DL5+ immune cells infiltrated in various types of PVR+ human cancers. Markedly, the KIR2DL5 blockade reduced tumor growth and improved overall survival across multiple NK cell-based humanized tumor models. Thus, our results revealed functional mechanisms of KIR2DL5-mediated NK cell immune evasion, demonstrated blockade of the KIR2DL5/PVR axis as a therapy for human cancers, and provided an underlying mechanism for the clinical failure of anti-TIGIT therapies.

Neuronal Agrin Promotes Proliferation of Primary Human Myoblasts in an Age-Dependent Manner

Neuronal agrin, a heparan sulphate proteoglycan secreted by the α-motor neurons, promotes the formation and maintenance of the neuromuscular junction by binding to Lrp4 and activating muscle-specific kinase (MuSK). Neuronal agrin also promotes myogenesis by enhancing differentiation and maturation of myotubes, but its effect on proliferating human myoblasts, which are often considered to be unresponsive to agrin, remains unclear. Using primary human myoblasts, we determined that neuronal agrin induced transient dephosphorylation of ERK1/2, while c-Abl, STAT3, and focal adhesion kinase were unresponsive. Gene silencing of Lrp4 and MuSK markedly reduced the BrdU incorporation, suggesting the functional importance of the Lrp4/MuSK complex for myoblast proliferation. Acute and chronic treatments with neuronal agrin increased the proliferation of human myoblasts in old donors, but they did not affect the proliferation of myoblasts in young donors. The C-terminal fragment of agrin which lacks the Lrp4-binding site and cannot activate MuSK had a similar age-dependent effect, indicating that the age-dependent signalling pathways activated by neuronal agrin involve the Lrp4/MuSK receptor complex as well as an Lrp4/MuSK-independent pathway which remained unknown. Collectively, our results highlight an age-dependent role for neuronal agrin in promoting the proliferation of human myoblasts.

The Golgi-localized sphingosine-1-phosphate phosphatase is indispensable for Leishmania major

Sphingosine-1-phosphate phosphatase (SPP) catalyzes the dephosphorylation of sphingosine-1-phosphate (S1P) into sphingosine, the reverse reaction of sphingosine kinase. In mammals, S1P acts as a potent bioactive molecule regulating cell proliferation, migration, and immunity. In Leishmania, S1P production is crucial for the synthesis of ethanolamine and choline phospholipids, and cell survival under stress conditions. To better understand the roles of S1P, we characterized a SPP ortholog in Leishmania major which displays activity towards S1P but not structurally related lipids such as ceramide-1-phosphate or lysophosphatidic acid. While this enzyme is found in the endoplasmic reticulum in mammalian cells, L. major SPP is localized at the Golgi apparatus. Importantly, chromosomal SPP alleles cannot be deleted from L. major even with the addition of a complementing episome, suggesting that endogenously expressed SPP is essential. Finally, SPP overexpression in L. major leads to a slower growth rate and heightened sensitivity to brefeldin A and sodium orthovanadate. Together, these results suggest that the equilibrium between S1P and sphingosine is vital for the function of Golgi apparatus in Leishmania.

Impact of Environmental Risk Factors on Mitochondrial Dysfunction, Neuroinflammation, Protein Misfolding, and Oxidative Stress in the Etiopathogenesis of Parkinson's Disease

As a prevalent progressive neurodegenerative disorder, Parkinson's disease (PD) is characterized by the neuropathological hallmark of the loss of nigrostriatal dopaminergic (DAergic) innervation and the appearance of Lewy bodies with aggregated α-synuclein. Although several familial forms of PD have been reported to be associated with several gene variants, most cases in nature are sporadic, triggered by a complex interplay of genetic and environmental risk factors. Numerous epidemiological studies during the past two decades have shown positive associations between PD and several environmental factors, including exposure to neurotoxic pesticides/herbicides and heavy metals as well as traumatic brain injury. Other environmental factors that have been implicated as potential risk factors for PD include industrial chemicals, wood pulp mills, farming, well-water consumption, and rural residence. In this review, we summarize the environmental toxicology of PD with the focus on the elaboration of chemical toxicity and the underlying pathogenic mechanisms associated with exposure to several neurotoxic chemicals, specifically 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), rotenone, paraquat (PQ), dichloro-diphenyl-trichloroethane (DDT), dieldrin, manganese (Mn), and vanadium (V). Our overview of the current findings from cellular, animal, and human studies of PD provides information for possible intervention strategies aimed at halting the initiation and exacerbation of environmentally linked PD.

A new paradigm for regulation of protein phosphatase 2A function via Src and Fyn kinase-mediated tyrosine phosphorylation

Protein phosphatase 2A (PP2A) is a major phospho-Ser/Thr phosphatase and a key regulator of cellular signal transduction pathways. While PP2A dysfunction has been linked to human cancer and neurodegenerative disorders such as Alzheimer’s disease (AD), PP2A regulation remains relatively poorly understood. It has been reported that the PP2A catalytic subunit (PP2Ac) is inactivated by a single phosphorylation at the Tyr307 residue by tyrosine kinases such as v-Src. However, multiple mass spectrometry studies have revealed the existence of other putative PP2Ac phosphorylation sites in response to activation of Src and Fyn, two major Src family kinases (SFKs). Here, using PP2Ac phosphomutants and novel phosphosite-specific PP2Ac antibodies, we show that cellular pools of PP2Ac are instead phosphorylated on both Tyr127 and Tyr284 upon Src activation, and on Tyr284 following Fyn activation. We found these phosphorylation events enhanced the interaction of PP2Ac with SFKs. In addition, we reveal SFK-mediated phosphorylation of PP2Ac at Y284 promotes dissociation of the regulatory Bα subunit, altering PP2A substrate specificity; the phosphodeficient Y127/284F and Y284F PP2Ac mutants prevented SFK-mediated phosphorylation of Tau at the CP13 (pSer202) epitope, a pathological hallmark of AD, and SFK-dependent activation of ERK, a major growth regulatory kinase upregulated in many cancers. Our findings demonstrate a novel PP2A regulatory mechanism that challenges the existing dogma on the inhibition of PP2A catalytic activity by Tyr307 phosphorylation. We propose dysregulation of SFK signaling in cancer and AD can lead to alterations in PP2A phosphorylation and subsequent deregulation of key PP2A substrates, including ERK and Tau.

Cisplatin causes covalent inhibition of protein-tyrosine phosphatase 1B (PTP1B) through reaction with its active site cysteine: Molecular, cellular and in vivo mice studies

Protein tyrosine phosphatase 1B (PTP1B) is a critical regulator of different signalling cascades such as the EGFR pathway. The biological importance of PTP1B is further evidenced by knockout mice studies and the identification of recurrent mutations/deletions in PTP1B linked to metabolic and oncogenic alterations. Cisplatin is among the most widely used anticancer drug. The biological effects of cisplatin are thought to arise primarily from DNA damaging events involving cisplatin-DNA adducts. However, increasing evidence indicate that the biological properties of cisplatin could also rely on the perturbation of other processes such as cell signalling through direct interaction with certain cysteine residues in proteins. Here, we provide molecular, cellular and in vivo evidence suggesting that PTP1B is a target of cisplatin. Mechanistic studies indicate that cisplatin inhibited PTP1B in an irreversible manner and binds covalently to the catalytic cysteine residue of the enzyme. Accordingly, experiments conducted in cells and mice exposed to cisplatin showed inhibition of endogenous PTP1B and concomitant increase in tyrosine phosphorylation of EGFR. These findings are consistent with previous studies showing tyrosine phosphorylation-dependent activation of the EGFR pathway by cisplatin and with recent studies suggesting PTP1B inhibition by cisplatin and other platinum complexes. Importantly, our work provides novel mechanistic evidence that PTP1B is a protein target of cisplatin and is inhibited by this drug at molecular, cellular and in vivo levels. In addition, our work may contribute to the understanding of the pathways undergoing modulation upon cisplatin administration beyond of the established genotoxic effect of cisplatin.

Modification of plasma membrane H+-ATPase in Masson pine (Pinus massoniana Lamb.) seedling roots adapting to acid deposition

To understand the regulation of roots plasma membrane H+-ATPase in Masson pine responding to acid deposition, the changes in biomass, plant morphology, intracellular H+, enzyme activity and H+-ATPase genes expression in Masson pine seedlings exposed to simulated acid rain (SAR, pH 5.6 and 4.6) with and without vanadate were studied. Simulated acid rain exposure for 60 days increased the intracellular H+ in pine roots whether added with 0.1 mM Na3VO4 or not. The growth of seedlings treated with SAR was maintained well, even the primary lateral root length, root dry weight and number of root tips in seedlings exposed to SAR at pH 4.6 were higher than that of the control (pH 6.6). However, the addition of vanadate resulted in severe growth inhibition and obvious decline in morphological parameters. Similarly, ATP hydrolytic activity and H+ transport activity of roots plasma membrane H+-ATPase, both were stimulated by SAR whereas they were inhibited by vanadate, and the highest activity stimulation was observed in pine roots subjected to SAR at pH 4.6. In addition, SAR also induced the expression of the investigated H+-ATPase subunits (atpB, atpE, atpF, atpH and atpI). Therefore, the roots plasma membrane H+-ATPase is instrumental in the growth of Masson pine seedlings adapting to acid rain by a manner of pumping more protons across the membrane through enhancing its activity, and which involves the upregulated gene expression of roots H+-ATPase subunits at transcriptional level.

Physical and functional interactome atlas of human receptor tyrosine kinases

Much cell‐to‐cell communication is facilitated by cell surface receptor tyrosine kinases (RTKs). These proteins phosphorylate their downstream cytoplasmic substrates in response to stimuli such as growth factors. Despite their central roles, the functions of many RTKs are still poorly understood. To resolve the lack of systematic knowledge, we apply three complementary methods to map the molecular context and substrate profiles of RTKs. We use affinity purification coupled to mass spectrometry (AP‐MS) to characterize stable binding partners and RTK–protein complexes, proximity‐dependent biotin identification (BioID) to identify transient and proximal interactions, and an in vitro kinase assay to identify RTK substrates. To identify how kinase interactions depend on kinase activity, we also use kinase‐deficient mutants. Our data represent a comprehensive, systemic mapping of RTK interactions and substrates. This resource adds information regarding well‐studied RTKs, offers insights into the functions of less well‐studied RTKs, and highlights RTK‐RTK interactions and shared signaling pathways.

Photoactivatable Reporter to Perform Multiplexed and Temporally Controlled Measurements of Kinase and Protease Activity in Single Cells

Peptide bioreporters were developed to perform multiplexed measurements of the activation of epidermal growth factor receptor kinase (EGFR), Akt kinase (Akt/protein kinase B), and proteases/peptidases in single cells. The performance characteristics of the three reporters were assessed by measuring the reporter's proteolytic stability, kinetic constants for EGFR and Akt, and dephosphorylation rate. The reporter displaying optimal performance was composed of 6-carboxyfluorescein (6-FAM) on the peptide N-terminus, an Akt substrate sequence employing a threonine phosphorylation site for Akt, followed by a tri-D arginine linker, and finally an EGFR substrate sequence bearing a phosphatase-resistant 7-(S)-hydroxy-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (L-htc) residue as the EGFR phosphorylation site. Importantly, use of a single electrophoretic condition separated the mono- and diphosphorylated products as well as proteolytic forms permitting the quantitation of multiple enzyme activities simultaneously using a single reporter. Because the Akt and EGFR substrates were linked, a known ratio (EGFR/Akt) of the reporter was loaded into cells. A photoactivatable version of the reporter was synthesized by adding two 4,5-dimethoxy-2-nitrobenzyl (DMNB) moieties to mask the EGFR and Akt phosphorylation sites. The DMNB moieties were readily photocleaved following exposure to 360 nm light, unmasking the phosphorylation sites on the reporter. The new photoactivatable reporter permitted multiplexed measurements of kinase signaling and proteolytic degradation in single cells in a temporally controlled manner. This work will facilitate the development of a new generation of multiplexed activity-based reporters capable of light-initiated measurement of enzymatic activity in single cells.

T cell receptor (TCR) signaling in health and disease

Interaction of the T cell receptor (TCR) with an MHC-antigenic peptide complex results in changes at the molecular and cellular levels in T cells. The outside environmental cues are translated into various signal transduction pathways within the cell, which mediate the activation of various genes with the help of specific transcription factors. These signaling networks propagate with the help of various effector enzymes, such as kinases, phosphatases, and phospholipases. Integration of these disparate signal transduction pathways is done with the help of adaptor proteins that are non-enzymatic in function and that serve as a scaffold for various protein-protein interactions. This process aids in connecting the proximal to distal signaling pathways, thereby contributing to the full activation of T cells. This review provides a comprehensive snapshot of the various molecules involved in regulating T cell receptor signaling, covering both enzymes and adaptors, and will discuss their role in human disease.

The role of available phosphorous in vanadate decontamination by soil indigenous microbial consortia

Indigenous microbial consortia are closely associated with soil inherent components including nutrients and minerals. Although indigenous microbial consortia present great prospects for bioremediation of vanadate [V(V)] contaminated soil, influences of some key components, such as available phosphorus (AP), on V(V) biodetoxification are poorly understood. In this study, surface soils sampled from five representative vanadium smelter sites were employed as inocula without pretreatment. V(V) removal efficiency ranged from 81.7 ± 1.4% to 99.5 ± 0.2% in batch experiment, and the maximum V(V) removal rates were positively correlated with AP contents. Long-term V(V) removal was achieved under fluctuant hydrodynamic and hydrochemical conditions in column experiment. Geobacter and Bacillus, which were found in both original soils and bioreactors, catalytically reduced V(V) to insoluble tetravalent vanadium. Phosphate-solubilizing bacterium affiliated to Gemmatimonadaceae were also identified abundantly. Microbial functional characterization indicated the enrichment of phosphate ABC transporter, which could accelerate V(V) transfer into intercellular space for efficient reduction due to the structural similarity of V(V) and phosphate. This study reveals the critical role of AP in microbial V(V) decontamination and provides promising strategy for in situ bioremediation of V(V) polluted soil.

Alzheimer's Disease and Diabetes Mellitus in Comparison: The Therapeutic Efficacy of the Vanadium Compound

Alzheimer’s disease (AD) is an intractable neurodegenerative disease that leads to dementia, primarily in elderly people. The neurotoxicity of amyloid-beta (Aβ) and tau protein has been demonstrated over the last two decades. In line with these findings, several etiological hypotheses of AD have been proposed, including the amyloid cascade hypothesis, the oxidative stress hypothesis, the inflammatory hypothesis, the cholinergic hypothesis, et al. In the meantime, great efforts had been made in developing effective drugs for AD. However, the clinical efficacy of the drugs that were approved by the US Food and Drug Association (FDA) to date were determined only mild/moderate. We recently adopted a vanadium compound bis(ethylmaltolato)-oxidovanadium (IV) (BEOV), which was originally used for curing diabetes mellitus (DM), to treat AD in a mouse model. It was shown that BEOV effectively reduced the Aβ level, ameliorated the inflammation in brains of the AD mice, and improved the spatial learning and memory activities of the AD mice. These finding encouraged us to further examine the mechanisms underlying the therapeutic effects of BEOV in AD. In this review, we summarized the achievement of vanadium compounds in medical studies and investigated the prospect of BEOV in AD and DM treatment.

Protein tyrosine phosphatase 1B targets focal adhesion kinase and paxillin in cell-matrix adhesions

Protein tyrosine phosphatase 1B (PTP1B, also known as PTPN1) is an established regulator of cell-matrix adhesion and motility. However, the nature of substrate targets at adhesion sites remains to be validated. Here, we used bimolecular fluorescence complementation assays, in combination with a substrate trapping mutant of PTP1B, to directly examine whether relevant phosphotyrosines on paxillin and focal adhesion kinase (FAK, also known as PTK2) are substrates of the phosphatase in the context of cell-matrix adhesion sites. We found that the formation of catalytic complexes at cell-matrix adhesions requires intact tyrosine residues Y31 and Y118 on paxillin, and the localization of FAK at adhesion sites. Additionally, we found that PTP1B specifically targets Y925 on the focal adhesion targeting (FAT) domain of FAK at adhesion sites. Electrostatic analysis indicated that dephosphorylation of this residue promotes the closed conformation of the FAT 4-helix bundle and its interaction with paxillin at adhesion sites.

Protein tyrosine phosphatase Shp2 positively regulates cold stress-induced tyrosine phosphorylation of SIRPα in neurons

The membrane protein SIRPα is a cold stress-responsive signaling molecule in neurons. Cold stress directly induces tyrosine phosphorylation of SIRPα in its cytoplasmic region, and phosphorylated SIRPα is involved in regulating experience-dependent behavioral changes in mice. Here, we examined the mechanism of cold stress-induced SIRPα phosphorylation in vitro and in vivo. The levels of activated Src family protein tyrosine kinases (SFKs), which phosphorylate SIRPα, were not increased by lowering the temperature in cultured neurons. Although the SFK inhibitor dasatinib markedly reduced SIRPα phosphorylation, low temperature induced an increase in SIRPα phosphorylation even in the presence of dasatinib, suggesting that SFK activation is not required for low temperature-induced SIRPα phosphorylation. However, in the presence of pervanadate, a potent inhibitor of protein tyrosine phosphatases (PTPases), SIRPα phosphorylation was significantly reduced by lowering the temperature, suggesting that either the inactivation of PTPase(s) that dephosphorylate SIRPα or increased protection of phosphorylated SIRPα from the PTPase activity is important for low temperature-induced SIRPα phosphorylation. Inactivation of PTPase Shp2 by the allosteric Shp2 inhibitor SHP099, but not by the competitive inhibitor NSC-87877, reduced SIRPα phosphorylation in cultured neurons. Shp2 knockout also reduced SIRPα phosphorylation in the mouse brain. Our data suggest that Shp2, but not SFKs, positively regulates cold stress-induced SIRPα phosphorylation in a PTPase activity-independent manner.

Role of PTEN-less in cardiac injury, hypertrophy and regeneration

Cardiovascular diseases are the leading cause of death worldwide. Cardiomyocytes are capable of coordinated contractions, which are mainly responsible for pumping blood. When cardiac stress occurs, cardiomyocytes undergo transition from physiological homeostasis to hypertrophic growth, proliferation, or apoptosis. During these processes, many cellular factors and signaling pathways participate. PTEN is a ubiquitous dual-specificity phosphatase and functions by dephosphorylating target proteins or lipids, such as PIP3, a second messenger in the PI3K/AKT signaling pathway. Downregulation of PTEN expression or inhibiting its biologic activity improves heart function, promotes cardiomyocytes proliferation, reduces cardiac fibrosis as well as dilation, and inhibits apoptosis following ischemic stress such as myocardial infarction. Inactivation of PTEN exhibits a potentially beneficial therapeutic effects against cardiac diseases. In this review, we summarize various strategies for PTEN inactivation and highlight the roles of PTEN-less in regulating cardiomyocytes during cardiac development and stress responses.

Effects of co-administration of arsenic trioxide and Schiff base oxovanadium complex on the induction of apoptosis in acute promyelocytic leukemia cells

Acute promyelocytic leukaemia (APL) is commonly treated with arsenic trioxide (As2O3) that has many side effects. Given the increasing trend of studies on beneficial therapeutic properties of synthetic compounds containing vanadium, the present study sought to use Schiff base oxovanadium complex to reduce the needed concentration of arsenic trioxide. The HL-60 cell line, which is a model of APL, was selected and the effects of arsenic trioxide and Schiff base oxovanadium complex were individually and simultaneously evaluated on the cell viability by the MTT assay. Flow cytometry and Real-time RT-PCR were also performed to investigate the rate of apoptosis and the expression of P53 and P21 genes, respectively. The IC50 of arsenic trioxide and Schiff base oxovanadium complex on Hl-60 cells was 8.37 ± 0.36 µM and 34.12 ± 1.52 µg/ml, respectively. At the simultaneous administration of both compounds, the maximum decrease in the cell viability was seen in co-administration of 40 µg/ml of Schiff base oxovanadium complex and 0.001 µM of arsenic trioxide. Real-time RT-PCR indicated that the co-administration of Schiff base oxovanadium complex 40 µg/ml and arsenic trioxide 0.001 µM could increase the expression of P53 and P21 genes by 3.76 ± 0.19 and 6.57 ± 1.29 fold change, respectively to the control sample. The flow cytometry studies also indicated that this co-administration could induce apoptosis up to 67% ± 0.9% significantly higher than the control sample. The use of Schiff base oxovanadium complex could significantly reduce the required dose of arsenic trioxide to induce apoptosis in HL-60 cells.

KIR3DL3-HHLA2 is a human immunosuppressive pathway and a therapeutic target

The B7 family ligand HERV-H LTR-associating protein 2 (HHLA2) is an attractive target for cancer immunotherapy because of its coinhibitory function, overexpression in human cancers, and association with poor prognoses. However, the knowledge of the HHLA2 pathway is incomplete. HHLA2 has an established positive receptor transmembrane and immunoglobulin (Ig) domain containing 2 (TMIGD2) but a poorly characterized negative receptor human killer cell Ig-like receptor, three Ig domains, and long cytoplasmic tail (KIR3DL3). Here, KIR3DL3 and TMIGD2 simultaneously bound to different sites of HHLA2. KIR3DL3 was mainly expressed on CD56dim NK and terminally differentiated effector memory CD8+ T (CD8+ TEMRA) cells. KIR3DL3+ CD8+ TEMRA acquired an NK-like phenotype and function. HHLA2 engagement recruited KIR3DL3 to the immunological synapse and coinhibited CD8+ T and NK cell function and killing, inducing immune-evasive HHLA2+ tumors. KIR3DL3 recruited SHP-1 and SHP-2 to attenuate Vav1, ERK1/2, AKT, and NF-κB signaling. HHLA2+ tumors from human kidney, lung, gallbladder, and stomach were infiltrated by KIR3DL3+ immune cells. KIR3DL3 blockade inhibited tumor growth in multiple humanized mouse models. Thus, our findings elucidated the molecular and cellular basis for the inhibitory function of KIR3DL3, demonstrating that the KIR3DL3-HHLA2 pathway is a potential immunotherapeutic target for cancer.

[Novel Tyrosine Phosphorylation Signals in the Nucleus and on Mitotic Spindle Fibers and Lysosomes Revealed by Strong Inhibition of Tyrosine Dephosphorylation]

Protein-tyrosine phosphorylation is one of the posttranslational modifications and plays critical roles in regulating a wide variety of cellular processes, such as cell proliferation, differentiation, adhesion, migration, survival, and apoptosis. Protein-tyrosine phosphorylation is reversibly regulated by protein-tyrosine kinases and protein-tyrosine phosphatases. Strong inhibition of protein-tyrosine phosphatase activities is required to undoubtedly detect tyrosine phosphorylation. Our extremely careful usage of Na₃VO₄, a potent protein-tyrosine phosphatase inhibitor, has revealed not only the different intracellular trafficking pathways of Src-family tyrosine kinase members but also novel tyrosine phosphorylation signals in the nucleus and on mitotic spindle fibers and lysosomes. Furthermore, despite that the first identified oncogene product v-Src is generally believed to induce transformation through continuous stimulation of proliferation signaling by its strong tyrosine kinase activity, v-Src-driven transformation was found to be caused not by continuous proliferation signaling but by v-Src tyrosine kinase activity-dependent stochastic genome alterations. Here, I summarize our findings regarding novel tyrosine phosphorylation signaling in a spatiotemporal sense and highlight the significance of the roles of tyrosine phosphorylation in transcriptional regulation inside the nucleus and chromosome dynamics.