Tyrosine Residues In Proteins Research Articles

Mass spectrometry analysis of phosphotyrosine-containing proteins.

Tyrosine phosphorylation is a crucial posttranslational modification that is involved in various aspects of cell biology and often has functions in cancers. It is necessary not only to identify the specific phosphorylation sites but also to quantify their phosphorylation levels under specific pathophysiological conditions. Because of its high sensitivity and accuracy, mass spectrometry (MS) has been widely used to identify endogenous and synthetic phosphotyrosine proteins/peptides across a range of biological systems. However, phosphotyrosine-containing proteins occur in extremely low abundance and they degrade easily, severely challenging the application of MS. This review highlights the advances in both quantitative analysis procedures and enrichment approaches to tyrosine phosphorylation before MS analysis and reviews the differences among phosphorylation, sulfation, and nitration of tyrosine residues in proteins. In-depth insights into tyrosine phosphorylation in a wide variety of biological systems will offer a deep understanding of how signal transduction regulates cellular physiology and the development of tyrosine phosphorylation-related drugs as cancer therapeutics.

Interaction mechanism of icariin and whey protein based on spectrofluorimetry and molecular docking

Icariin has low bioavailability and poor stability, which limits its wide application. The complexation of icariin and whey protein is expected to solve this problem, but there is no research on their interaction mechanism. In view of this, the related mechanism was studied systematically by spectrofluorimetry and molecular docking method in this study. The fluorescence analysis showed that icariin and whey protein could form a non-covalent complex driven by hydrophobic force, which led to the fluorescence quenching of whey protein. In this process, the microenvironment around the tyrosine residue and tryptophan residue of whey protein changed. The molecular docking analysis confirmed the existence of hydrophobic interaction and hydrogen bonding in the complex, which well confirmed fluorescence results. The obtained results can promote the application of icariin in food.

Abstract 10825: Tumor-Bearing Induces Cardiomyopathy by Disrupting Cardiometabolic Reprogramming

Introduction: Advances in cancer therapies have significantly improved patient survival. However, prolonged tumor-bearing (TB) survival makes the originally hidden cardiovascular disease become an increasingly important cause of death in tumor patients. In addition, some commonly used chemotherapeutic agents, such as the doxorubicin (DOX), have definite cardiotoxicity. Moreover, epidemiological studies found higher risks of cardiovascular disease in cancer patients than in the general population. This study aimed to investigate the if the TB state leads to cardio-fragility and myocardial sensitivity which further causes excessive cardiotoxicity of DOX in tumor patients. Methods and Results: We established mouse TB models with six types of transplantation tumors. We administrated them and littermate controls with DOX intraperitoneal injections of 10mg/kg weekly for four weeks. The results showed more severer myocardial injury in TB mice than control group based on the echocardiography, cardiac fibrosis, and etc. The RNA-seq, extracellular flux analysis, and PET-CT indicated an increased proportion of myocardial glycolytic metabolism in the TB state. Furthermore, the Secretomic results of clinical cancer patients and control group, along with the Co-IP of TB mice, showed that the TB state induced hyper-phosphorylation of protein tyrosine residues in cardiomyocytes (CMs) via the increase of secreted growth factors, which introduced an elevated expression of pyruvate kinase muscle 2 (PKM2) and increased the proportion of dimer conformation. Meanwhile, those changes allowing re-entry of CMs into the cell cycle and further increased DNA damage co-localization with EdU, eventually led to excessive cardiotoxicity in the TB state by DOX. Finally, treatment with AG-1478 or TEPP-46 with DOX restricted the cardiotoxicity in the TB state, which meanwhile enhanced the tumor-suppressive effect in lung cancer and melanoma models. Conclusion: Our study reveals that differences in tyrosine phosphorylation of CMs between TB and normal states could cause metabolic pattern shift and cell cycle re-entry in CMs. The increased cardio-fragility induced by TB state may be involved in the enhanced cardiotoxic side effects of chemotherapeutics.

Protein C-Terminal Tyrosine Conjugation via Recyclable Immobilized BmTYR.

Protein modification plays an essential role in biological and pharmaceutical research. Due to the ordinary selectivity and inevitable damage to proteins of chemical synthetic methods, increased efforts were focused on biocatalysts which exhibited high regioselectivity and mild reaction conditions. However, separation of the biocatalysts and modified proteins remained a problem, especially when scaling up. Here, we developed a simple method for site-specific protein modification with a recyclable biocatalyst. The immobilizing tyrosinase (BmTYR) on magnetic beads can oxidize C-terminal tyrosine residues of the target protein to o-quinone, followed by the spontaneous addition of different nucleophiles (e.g., aniline derivatives), resulting in a C-terminal modified protein. Compared to the homogeneous biocatalytic system reported before, this heterogeneous system leads to an easier separation. Furthermore, the solid-phase biocatalyst can be regenerated during separation, providing reusability and lower costs.

Oncogenic fusion of BCAR4 activates EGFR signaling and is sensitive to dual inhibition of EGFR/HER2.

We previously reported CD63-BCAR4 fusion as a novel oncogene that significantly enhanced cell migration and metastasis in lung cancer. To identify effective inhibitors of metastatic activity induced by BCAR4 fusion, we screened a drug library of 381 FDA-approved compounds. The effect of drugs on cell migration was evaluated by monitoring wound healing. Drugs that decreased the cellular mobility of fusion-overexpressing cells compared with that of control cells were selected as candidates. Library screening revealed that erlotinib, canertinib, and lapatinib demonstrated inhibitory effects on cell migration. Activation of the EGFR signaling pathway was detected after ectopic expression of CD63-BCAR4 in normal bronchial epithelial cells, as observed by the increased phosphorylation of tyrosine residues in the EGFR protein. We also confirmed increased levels of the phosphorylated EGFR protein in resected tumors from mice injected with CD63-BCAR4 overexpressing cells. Tyrosine kinase inhibitors (TKIs) of the EGFR family significantly inhibit the migration of BCAR4 fusion-overexpressing cells and induce apoptosis at high concentrations. Among the EGFR family TKIs, canertinib, a dual EGFR/HER2 inhibitor, showed the best inhibitory effect on the migration and viability of BCAR4 fusion-overexpressing cells. We examined the effect of canertinib in vivo using a mouse xenograft model. Oral administration of canertinib to xenografted mice reduced tumor growth induced by the CD63-BCAR4 fusion gene. In addition, canertinib treatment restored E-cadherin expression and reduced the expression of epithelial–mesenchymal transition regulatory factors such as Slug and Snail. Taken together, these results suggest that EGFR/HER2 inhibitors are potential therapeutic options for BCAR4 fusion-harboring lung cancer patients, even in the absence of EGFR mutations.

Salicylaldehyde Suppresses IgE-Mediated Activation of Mast Cells and Ameliorates Anaphylaxis in Mice.

Mast cells (MCs) play key roles in IgE-mediated immunoresponses, including in the protection against parasitic infections and the onset and/or symptoms of allergic diseases. IgE-mediated activation induces MCs to release mediators, including histamine and leukotriene, as an early response, and to produce cytokines as a late phase response. Attempts have been made to identify novel antiallergic compounds from natural materials such as Chinese medicines and food ingredients. We herein screened approximately 60 compounds and identified salicylaldehyde, an aromatic aldehyde isolated from plant essential oils, as an inhibitor of the IgE-mediated activation of MCs. A degranulation assay, flow cytometric analyses, and enzyme-linked immunosorbent assays revealed that salicylaldehyde inhibited the IgE-mediated degranulation and cytokine expression of bone-marrow-derived MCs (BMMCs). The salicylaldehyde treatment reduced the surface expression level of FcεRI, the high affinity receptor for IgE, on BMMCs, and suppressed the IgE-induced phosphorylation of tyrosine residues in intercellular proteins, possibly Lyn, Syk, and Fyn, in BMMCs. We also examined the effects of salicylaldehyde in vivo using passive anaphylaxis mouse models and found that salicylaldehyde administration significantly enhanced the recovery of a reduced body temperature due to systemic anaphylaxis and markedly suppressed ear swelling, footpad swelling, and vascular permeability in cutaneous anaphylaxis.

Free-cell therapeutics and mechanism of exosomes from adipose-derived stem cells in promoting wound healing: current understanding and future applications.

Free-cell therapeutics and mechanism of exosomes from adipose-derived stem cells in promoting wound healing: current understanding and future applications.

Investigation of structure–stability correlations of reconstructed oil bodies

To overcome the challenges of complex synthesis methods and the thermodynamic instability associated with conventional emulsions, the artificial oil bodies (AOBs) containing oil body proteins (OBPs) and phospholipids (PLs) were fabricated using ultrasonication and the correlations between their reconstituted structures and characteristics were investigated. As the PL concentration was increased, the concentrations of α-helix and β-turns in interfacial proteins decreased, whereas those of β-sheets and random coils increased. Moreover, the number of the intermolecular hydrogen bond first increased and then decreased. At an OBP/PL ratio of 0.5, the AOBs exhibited the lowest mean particle size (unimodal distribution), highest creaming index, and lowest KE. The oxidation stabilities of the AOBs with OBP/PL ratios of 0.05 and 0.015 were higher than those of other AOBs. Furthermore, statistical analysis indicated that the secondary structure and tyrosine residues of the interface protein were significantly correlated with the stability of the AOBs (p < 0.05), but the hydrogen bond of the interface protein has a low correlation with the stability of the oil body.

Quantitative Functionalization of the Tyrosine Residues in Silk Fibroin through an Amino‐Tyrosine Intermediate

AbstractHere, a reaction sequence that can be used to quantitatively modify the tyrosine residues in silk protein fromB. morisilkworms is demonstrated. A primary amine is installed ortho to the hydroxyl group on the tyrosine ring using a diazonium coupling reaction followed by reduction of the azo bond. The resulting amine is then acylated using carboxylic acid or NHS‐ester derivatives at room temperature and neutral pH conditions. The silk derivatives are characterized using1H NMR, UV–vis spectroscopy, ATR‐FTIR, and a unique method to follow this reaction sequence using isotopically labeled reagents and 2D NMR spectroscopy is also used. This study further demonstrates that this sequence can be used to install alkyne or azide functional groups which can undergo further bio‐orthogonal cycloaddition reactions under mild conditions. Finally, methods to carry out these modifications on solid silk microparticles and electrospun mats are also described.

A pilot study on nitration/dysfunction of NK1 segment of myogenic stem cell activator HGF

Protein tyrosine residue (Y) nitration, a post-translational chemical-modification mode, has been associated with changes in protein activity and function; hence the accumulation of specific nitrated proteins in tissues may be used to monitor the onset and progression of pathological disorders. To verify the possible impact of nitration on postnatal muscle growth and regeneration, a pilot study was designed to examine the nitration/dysfunction of hepatocyte growth factor (HGF), a key ligand that is released from the extracellular tethering and activates myogenic stem satellite cells to enter the cell cycle upon muscle stretch and injury. Exposure of recombinant HGF (a hetero-dimer of α- and β-chains) to peroxynitrite induces Y nitration in HGF α-chain under physiological conditions. Physiological significance of this finding was emphasized by Western blotting that showed the NK1 segment of HGF (including a K1 domain critical for signaling-receptor c-met binding) undergoes nitration with a primary target of Y198. Peroxynitrite treatment abolished HGF-agonistic activity of the NK1 segment, as revealed by in vitro c-met binding and bromodeoxyuridine-incorporation assays. Importantly, direct-immunofluorescence microscopy of rat lower hind-limb muscles from two aged-groups (2-month-old “young” and 12-month-old “retired/adult”) provided in vivo evidence for age-related nitration of extracellular HGF (Y198). Overall, findings provide the insight that HGF/NK1 nitration/dysfunction perturbs myogenic stem cell dynamics and homeostasis; hence NK1 nitration may stimulate progression of muscular disorders and diseases including sarcopenia.

Characterization of Protein Tyrosine Phosphatase 1B activator peptides in cells

The Protein Tyrosine Phosphatase (PTP) family of phosphatases regulates cell signaling through dephosphorylation of serine, threonine and tyrosine residues of downstream effector proteins. The role of PTPs is very well known in normal cell functions, as well as in disease states such as diabetes and cardiovascular diseases. We previously reported on the role of the phosphotyrosine recognition loop (PTBL) of PTP1B in protein‐protein interactions (Londhe et al.2020, Nat. Chem. Biol., 16(2):122‐125) and showed that interfering with protein‐protein interactions between PTP1B and 14‐3‐3zusing R18, a pan‐14‐3‐3 inhibitor, destabilizes the reversibly oxidized form of PTP1B (PTP1B‐OX) and activates the phosphatase. We rationally designed peptides using phosphotyrosine recognition loop of PTP1B to determine whether selective and effective activation of PTPs was possible. We first performed a structural analysis to compare the changes occurring in PTP1B‐OX compared to its reduced form. Using this approach, we observed profound conformational changes in the phosphotyrosine recognition loop (PTBL) of PTP1B and rationally designed peptides comprised of the sequence of amino acids of the newly exposed loop, with a TAT (transactivator of transcription) peptide sequence in amino or carboxy‐terminal to facilitate cell permeability. Targeting the PTP1B‐OX‐14‐3‐3z interaction using R18 and TAT‐PTBL peptide led to disruption in protein‐protein interaction and maintained PTP1B in its active form. Interestingly, destabilizing the PTP1B‐OX form by treating cells with rationally designed PTP1B activator peptides also decreased EGFR phosphorylation at PTP1B sites. In cells stimulated with exogenousH2O2 to bypass the NOX‐mediated PTP1B oxidation, the pretreatment with R18 and TAT‐PTBL prevented the interaction between PTP1B‐OX and 14‐3‐3z. Then we observed that our TAT‐PTBL peptide was not interfering with NOX‐mediated reactive oxygen species (ROS) generation, whereas R18, a pan‐14‐3‐3 inhibitor, decreased ROS production significantly. Finally, exposing A431 epidermoid carcinoma cells to PTP1B activator peptides prevented EGFR phosphorylation and impaired colony formation. Collectively our data suggest that the biological activity of PTP1B activator peptides is likely to be therapeutically useful, and could translate into drug leads.

Photothermal/NO combination therapy from plasmonic hybrid nanotherapeutics against breast cancer.

In this study, a plasmon-semiconductor nanotheranostic system comprising Au nanostars/graphene quantum dots (AuS/QD) hybrid nanoparticles loaded with BNN6 and surface modified with PEG-pyrene was developed for the photo-triggered hyperthermia effect and NO production as the dual modality treatment against orthotopic triple-negative breast cancer. The structure and morphology of the hybrid nanodevice was characterized and the NIR-II induced thermal response and NO production was determined. The hybrid nanodevice has shown enhanced plasmonic energy transfer from localized surface plasmonic resonance of Au nanostars to QD semiconductor that activates the BNN6 species loaded on QD surfaces, leading to the effective NO production and the gas therapy in addition to the photothermal response. The increased accumulation of the NIR-II-responsive hybrid nanotheranostic in tumor via the enhanced permeation and retention effects was confirmed by both in vivo fluorescence and photoacoustic imaging. The prominent therapeutic efficacy of the photothermal/NO combination therapy from the BNN6-loaded AuS@QD nanodevice with the NIR-II laser irradiation at 1064nm against 4T1 breast cancer was observed both in vitro and in vivo. The NO therapy for the cancer treatment was evidenced with the increased cellular nitrosative and oxidative stress, nitration of tyrosine residues of mitochondrial proteins, vessel eradication and cell apoptosis. The efficacy of the photothermal treatment was corroborated directly by severe tissue thermal ablation and tumor growth inhibition. The NIR-II triggered thermal/NO combination therapy along with the photoacoustic imaging-guided therapeutic accumulation in tumor shows prominent effect to fully inhibit tumor growth and validates the promising strategy developed in this study.

Shear Stress Induces α-Synuclein Aggregation Due to a Less Strained Protein Backbone and Protein Tyrosyl Groups Do Not Intervene in the Aggregation

Parkinson’s disease (PD) is an increasingly prevalent and currently incurable neurodegenerative disorder. The aggregation of the amyloid disordered protein α-synuclein (Syn) has been implicated in the development of PD. In the literature, it has been suggested that tyrosine residues of Syn play an important role in the interactions established during the fibrillation process. Herein, the prevalence of the referred interactions under shear stress conditions of Nα-acetyl-L-tyrosinamide (NAYA) and of Syn solutions by using membrane centrifugal filters with different cut-off of 200 nm, 100 kDa, 50 kDa and 30 kDa, under centrifugation conditions, were investigated. In order to determine the nature of the interactions involving the protein tyrosine residues the NAYA compound, which mimics the peptide bonds in protein and also possesses a tyrosyl group similar to the tyrosyl groups found in the Syn protein molecular structure, was used. It is expected that for a small molecule, such as NAYA, no molecular association occurs, contrary to what exists in the Syn protein solutions, which can more adequately retrieve the type of interactions formed, involving the tyrosyl group. Therefore, sensing the tyrosyl group absorption, spectroscopic techniques, in particular, were used. For NAYA, an intramolecular interaction between the tyrosyl group and the peptide bond was evidenced. For NAYA and Syn, it was observed that decreasing the membrane centrifugal filters pore size, under centrifugation conditions, was concomitant with the minimization of the intramolecular interactions between the tyrosyl group and the peptide bond. With this, it is likely to assume that shear stress conditions in the Syn solutions propel protein aggregation by a less strained protein backbone. Contrary to the centrifugation of NAYA solutions, centrifuging Syn solutions revealed molecular association and a progressive exposure of protein tyrosyl groups to water. Thus, we can also infer that shear stress conditions in the Syn solutions cause the protein tyrosyl groups to not intervene in the protein aggregation.

Selecting motile, non-apoptotic and induced spermatozoa for capacitation without centrifuging by MACS-Up method.

In newly improved MACS-Up method, magnetic field has been applied to separate non-apoptotic spermatozoa directly from the neat semen. The spermatozoa during passing through a viscous layer, located on the neat semen, contacted with progesterone and induced for the capacitation. Then, a clean population of non-apoptotic, and capacitated spermatozoa were selected in the pure culture media. Selected spermatozoa may be useful for use in ART. The 80semen samples from normozoospermic individuals were divided separately into 4 attempts. Semen analysis, SCSA (sperm chromatin structure assay), FLICA (fluorescein-labelled inhibitors of caspase) methods, immunoassay of phosphorylation of tyrosine residues of sperm proteins, nuclear DNA integrity, caspase 3 activity and sperm capacitation rate were all performed for evaluation of sperm parameters respectively. To examine all aspects, the MACS-Up method compared with DGC (density gradient centrifuging) and MACS-DGC methods separately. This method can isolate non-apoptotic spermatozoa directly from the neat semen, which has similar performance compared to the MACS-DGC method. Movement and passing spermatozoa through the viscous layer, and contact with progesterone, significantly induced spermatozoa for capacitation compared with the control group. Also, the MACS-Up in comparison with routine DGC method could select spermatozoa with significantly higher total and progressive motility, DNA integrity, induced sperm population for capacitation and normal morphology. MACS-Up can be developed as an effective, short-time, and ease of performing method and used practically to select functional spermatozoa as novel sperm selection procedure. However, for clinical use of MACS-Up, all clinical aspects of this method should be considered and evaluated.

Glial cell line derived neurotrophic factor in brain repair after focal ischemic stroke.

Glial cell line derived neurotrophic factor in brain repair after focal ischemic stroke.

Redox Regulation to Modulate Phosphorylation Events in Human Spermatozoa.

Significance: Spermatozoa are complex and compartmentalized cells that undergo capacitation, a series of biochemical and morphological changes to acquire the ability to fertilize oocytes. Reactive oxygen species (ROS) have a prominent dual role in capacitation. At physiological levels, ROS regulate numerous cellular processes, including increases of cyclic adenosine monophosphate, calcium, and activation of phosphorylation events needed for capacitation. On the contrary, at high concentrations that do not impair sperm viability, ROS can cause loss of motility and inhibition of capacitation. Higher ROS concentrations promote oxidation of lipids, proteins, and DNA leading to cell death, and these damages have been associated with male infertility. Critical Issues: When incubated under specific conditions, spermatozoa can produce low and controlled amounts of ROS that are not harmful but instead regulate numerous cellular processes, including the phosphorylation of tyrosine, serine, and threonine residues in critical proteins needed for sperm capacitation. Here, we outline the complex redox signaling in human spermatozoa needed to achieve fertility and the role of ROS as physiological mediators that trigger phosphorylation cascades. Moreover, we illustrate the importance of various phosphoproteins in spermatozoa capacitation, viability, and hyperactive motility. Future Directions: Further studies to elucidate the different phosphorylation players during sperm capacitation and acrosome reaction (the regulated exocytotic event that releases proteolytic enzymes allowing the spermatozoon to penetrate the zona pellucida and fertilize the oocyte) are essential to understand how the spermatozoon acquires the fertilizing ability to fertilize the oocyte. This knowledge will serve to develop novel diagnostic tools and therapy for male infertility. Antioxid. Redox Signal. 37, 437-450.

686 Characterization of a novel compound that inhibits peroxynitrite generation by myeloid derived suppressor cells

BackgroundMyeloid-derived suppressor cells (MDSC) are immature immune cells that suppress immunity and mediate resistance to immune–based cancer therapies. MDSC exert their immunosuppressive effects partly through the production of reactive nitrogen and oxygen species, which combine to form peroxynitrite (PNT). PNT reacts with the tyrosine residues of key immune cell signaling proteins and inactivates them via nitration. Targeting MDSC via PNT inhibitors is an attractive avenue to improve the response to immunotherapy. The Peterson and Carson Labs have collaborated to develop a novel inhibitor of PNT and have explored its use in murine tumor models and human patients with cancer.MethodsSplenocytes (comprised of 12% MDSC) were isolated from mice bearing tumors derived from the EMT6 breast cancer cell line and cultured with 10 µm beads labelled with polyclonal antibodies (immunoglobulin-G or IgG). Fluorescence emitted upon MDSC recognition and reaction with IgG was detected with a previously reported fluorescent sensor compound termed PS3. Cells were mixed with PS3 and IgG beads (or controls: IgG without beads and beads without IgG) and treated for 4 hours with the following agents: (1) BRP0112233, a novel biaryl furan discovered via high-throughput screening using PNT depletion as the readout (6 or 12 µM); (2) Ibrutinib, an FDA-approved Bruton's tyrosine kinase inhibitor shown by the Carson Lab to inhibit the activity of nitric oxide synthase in MDSC, (2, 10 µM); and (3) PBS control. Fluorescence produced by reaction of PS3 with PNT was measured in triplicate wells using a Clariostar plate reader.ResultsSplenocytes from tumor-bearing mice produced significantly greater levels of PNT than normal splenocytes (24-fold vs 8-fold increase over plain beads, p&lt;0.0001). Differences in fluorescence were confirmed via confocal microscopy. BRP0112233 inhibited PNT levels by 40% and 85% for the 6 and 12 µM doses, respectively. Ibrutinib inhibited PNT output by 90% and 100% at 2 and 10 µM. Cell viability was &gt;90% except for the higher BRP dose (60% viability). In humans, peripheral blood mononuclear cells (PBMC) isolated from patients with cancer produced more PNT than healthy donor PBMC.ConclusionsPNT output could be reproducibly quantified via this assay and BRP0112233 and ibrutinib greatly inhibited MDSC PNT production. Using the EMT6 model, these compounds are being tested in combination with anti-PD-1 antibodies approved for patients with cancer. This assay has shown similar results in human peripheral blood mononuclear cells isolated from patients with cancer.AcknowledgementsWe thank the NIH (NCI UM1 CA186712, R01CA211720), a OSUCCC Translational Therapeutics Seed Grant, and the Pelotonia Fellowship Program for financial support.

Potential molecular mechanism of radiation-induced cytotoxicity of Cetrimonium bromide to head and neck cancer cells

A previous study has shown that Cetrimonium bromide has a slight cytotoxicity to head and neck cancer cells due to the presence of the cationic quaternary amine group in this molecule that affects the function of mitochondria.The same study also found that the cytotoxicity of Cetrimonium bromide increased when combined with gamma radiation and this could be used to treat head and neck cancer in a mice in vivo tumor model.In the current study, an in vitro photochemical reaction between Cetrimonium chloride and tyrosine was investigated in order to understand the molecular mechanism of the in vivo observations and data. I found that Cetrimonium chloride could react with tyrosine upon simulated solar irradiation to produce an imine Schiff base which turned into cyano-tyrosine and a melanin polymer.It is possible that in the in vivo study mentioned earlier, the gamma radiation and Cetrimonium bromide together destroyed the tyrosine residues in some cellular proteins chemically, and as a result, tyrosine phosphorylation was inhibited in the cancer cells which slowed the growth of the tumor.

Ageing Causes Ultrastructural Modification to Calcium Release Units and Mitochondria in Cardiomyocytes.

Ageing is associated with an increase in the incidence of heart failure, even if the existence of a real age-related cardiomyopathy remains controversial. Effective contraction and relaxation of cardiomyocytes depend on efficient production of ATP (handled by mitochondria) and on proper Ca2+ supply to myofibrils during excitation–contraction (EC) coupling (handled by Ca2+ release units, CRUs). Here, we analyzed mitochondria and CRUs in hearts of adult (4 months old) and aged (≥24 months old) mice. Analysis by confocal and electron microscopy (CM and EM, respectively) revealed an age-related loss of proper organization and disposition of both mitochondria and EC coupling units: (a) mitochondria are improperly disposed and often damaged (percentage of severely damaged mitochondria: adults 3.5 ± 1.1%; aged 16.5 ± 3.5%); (b) CRUs that are often misoriented (longitudinal) and/or misplaced from the correct position at the Z line. Immunolabeling with antibodies that mark either the SR or T-tubules indicates that in aged cardiomyocytes the sarcotubular system displays an extensive disarray. This disarray could be in part caused by the decreased expression of Cav-3 and JP-2 detected by western blot (WB), two proteins involved in formation of T-tubules and in docking SR to T-tubules in dyads. By WB analysis, we also detected increased levels of 3-NT in whole hearts homogenates of aged mice, a product of nitration of protein tyrosine residues, recognized as marker of oxidative stress. Finally, a detailed EM analysis of CRUs (formed by association of SR with T-tubules) points to ultrastructural modifications, i.e., a decrease in their frequency (adult: 5.1 ± 0.5; aged: 3.9 ± 0.4 n./50 μm2) and size (adult: 362 ± 40 nm; aged: 254 ± 60 nm). The changes in morphology and disposition of mitochondria and CRUs highlighted by our results may underlie an inefficient supply of Ca2+ ions and ATP to the contractile elements, and possibly contribute to cardiac dysfunction in ageing.

Overexpression of rice OsWNK9 promotes arsenite tolerance in transgenic Arabidopsis plants

Protein kinases are involved in the transfer of phosphate group to serine, threonine, and tyrosine residues of a target protein. With No Lysine (WNK) kinase is a member of the serine/threonine protein kinase family, which has conserved catalytic lysine (K) residue in subdomain I instead of being in subdomain II.The WNKs family members in plants are stress inducible and have been validated for their role in abiotic stress tolerance. In the present study, we have characterized Arabidopsis overexpressed lines of OsWNK9 regulated by the constitutive promoter under arsenite stress. Moreover, we have performed In silico expression analysis of OsWNK9 under nutrient deficiency and heavy metal stress. Three independent transgenic Arabidopsis (OsWNK9-OX T11, T12,andT13) lines showed tolerance to arsenite stress compared to wild-type (WT) plants. Under arsenite stress, transgenic lines T11, T12 and T13 showed 56.46, 57.8 and 51.66 % increased biomass respectively, as compared to WT plants. All three ArabidopsisOsWNK9-OX lines exhibited higher proline content, increased antioxidant enzyme activities and lower hydrogen peroxide levels under arsenite stress. Besides, the total antioxidant capacity in terms of DPPH (2, 2-diphenyl-1-picrylhydrazyl) free radical scavenging percentage was increased by 8–15 % in three independent OsWNK9-OX lines compared with those of WT plants. Protein-protein interaction analysis of OsWNK9 predicted interaction partners with protein kinase and oxidative stress-responsive protein. Co-expression analysis of OsWNK9 in phosphate deficiency and arsenate stress condition predicted various proteins including membrane transporter and transcription factors. Taken together, our results, for the first time, provide evidence that OsWNK9 could positively mediate arsenite stress tolerance in plants.