RING finger E3 ligase, RNF138 inhibits osteoblast differentiation by negatively regulating Runx2 protein turnover.

A few ubiquitin ligases have been shown to target Runx2, the key osteogenic transcription factor and thereby regulate bone formation. The regulation of Runx2 expression and function are controlled both at the transcriptional and posttranslational levels. Really interesting new gene (RING) finger ubiquitin ligases of which RNF138 is a member are important players in the ubiquitin-proteasome system, contributing to the regulation of protein turnover and cellular processes. Here, we demonstrated that RNF138 negatively correlated with Runx2 protein levels in osteopenic ovariectomized rats which implied its role in bone loss. Accordingly, RNF138 overexpression potently inhibited osteoblast differentiation of mesenchyme-like C3H10T1/2 as well primary rat calvarial osteoblast (RCO) cells in vitro, whereas overexpression of catalytically inactive mutant RNF138Δ18-58 (lacks RING finger domain) had mild to no effect. Contrarily, RNF138 depletion copiously enhanced endogenous Runx2 levels and augmented osteogenic differentiation of C3H10T1/2 as well as RCOs. Mechanistically, RNF138 physically associates within multiple regions of Runx2 and ubiquitinates it leading to its reduced protein stability in a proteasome-dependent manner. Moreover, catalytically active RNF138 destabilized Runx2 which resulted in inhibition of its transactivation potential and physiological function of promoting osteoblast differentiation leading to bone loss. These findings underscore the functional involvement of RNF138 in bone formation which is primarily achieved through its modulation of Runx2 by stimulating ubiquitin-mediated proteasomal degradation. Thus, our findings indicate that RNF138 could be a promising novel target for therapeutic intervention in postmenopausal osteoporosis.

AIP4 regulates adipocyte differentiation by targeting C/EBPα for ubiquitin-mediated proteasomal degradation.

Adipogenesis, that is, the formation of terminally differentiated adipocytes is intricately regulated by transcription factors where CCAAT/enhancer binding protein alpha (C/EBPα) plays a key role. In the current study, we demonstrate that E3 ubiquitin ligase AIP4 negatively regulates C/EBPα protein stability leading to reduced adipogenesis. While AIP4 overexpression in 3T3-L1 cells preadipocytes inhibited lipid accumulation when treated with differentiation inducing media (MDI), AIP4 depletion was sufficient to partially promote lipid accumulation even in the absence of MDI. Mechanistically, overexpression of AIP4 inhibited protein levels of both ectopically expressed as well as endogenous C/EBPα while catalytically inactive AIP4 failed. On the contrary, AIP4 depletion profoundly enhanced endogenous C/EBPα protein levels. The observation that AIP4 levels decrease with concomitant increase in C/EBPα levels during adipocyte differentiation further indicated that AIP4 negatively regulates C/EBPα levels. We further show that AIP4 physically interacts with C/EBPα and ubiquitinates it leading to its proteasomal degradation. AIP4 promoted K48-linked ubiquitination of C/EBPα while catalytically inactive AIP4-C830A failed. Taken together, our data demonstrate that AIP4 inhibits adipogenesis by targeting C/EBPα for ubiquitin-mediated proteasome degradation.

Dexamethasone activates c-Jun NH2-terminal kinase (JNK) which interacts with GR and protects it from ubiquitin-mediated degradation in NSCLC cells.

Dexamethasone-mediated pharmacological activation of the glucocorticoid receptor (GR) is widely used in the treatment regimen of hematological malignancies and solid cancers. However, DEX sensitivity towards patients primarily depends on the endogenous protein levels of GR. We observed that DEX treatment leads to an increase in GR protein levels despite inhibition of neo-protein synthesis in non-small cell lung cancer (NSCLC) cells. Mechanistically, DEX-stimulation concomitantly increased the JNK phosphorylation and GR protein levels, however the JNK stimulation preceds GR upregulation. Moreover, we also observed that DEX-mediated phosphorylation is partially mediated by upregulation in MEKK1 phosphorylation. Further, GR protein levels were significantly decreased in JNK inhibitor (JNKi, SP600125) treated cells whereas MG132 treatment restored GR levels indicating that DEX induced JNK activity regulated the GR protein levels through proteasomal-degradation pathway. Next, we showed that DEX led to JNK activation which physically interacts with GR and protects it from ubiquitination-mediated degradation. Furthermore, at basal level GR interacts with JNK in cytoplasm whereas upon DEX stimulation GR and pJNK both localized to nucleus and interact with each other. Next, we show that JNK-mediated GR stabilization affects its nuclear transcriptional functional activity in NSCLC cells. In line with these in vitro data, patient dataset analysis also shows that increased levels of both JNK and GR contributes towards better prognosis of NSCLC patients. Taken together, our data shows that DEX treatment may lead to positive feedback regulation of GR by activating JNK and thus highlights importance of GR-JNK crosstalk in NSCLC.

Recent Advancements in Nanocarrier-assisted Brain Delivery of Phytochemicals Against Neurological Diseases.

Despite ongoing advancements in research, the inability of therapeutics to cross the blood-brain barrier (BBB) makes the treatment of neurological disorders (NDs) a challenging task, offering only partial symptomatic relief. Various adverse effects associated with existing approaches are another significant barrier that prompts the usage of structurally diverse phytochemicals as preventive/therapeutic lead against NDs in preclinical and clinical settings. Despite numerous beneficial properties, phytochemicals suffer from poor pharmacokinetic profile which limits their pharmacological activity and necessitates the utility of nanotechnology for efficient drug delivery. Nanocarriers have been shown to be proficient carriers that can enhance drug delivery, bioavailability, biocompatibility, and stability of phytochemicals. We, thus, conducted a meticulous literature survey using several electronic databases to gather relevant studies in order to provide a comprehensive summary about the use of nanocarriers in delivering phytochemicals as a treatment approach for NDs. Additionally, the review highlights the mechanisms of drug transport of nanocarriers across the BBB and explores their potential future applications in this emerging field.

Extracellular Signal-Regulated Kinase1 (ERK1)-Mediated Phosphorylation of Voltage-Dependent Anion Channel (VDAC) Suppresses its Conductance.

ERK1 is one of the members of the mitogen-activated protein kinases that regulate important cellular functions. VDAC is located at the outer membrane of mitochondria. Here, an interaction between VDAC and ERK1 has been studied on an artificial planar lipid bilayer using in vitro electrophysiology experiments. We report that VDAC is phosphorylated by ERK1 in the presence of Mg2+-ATP and its single-channel currents are inhibited on the artificial bilayer membrane. Treatment of Alkaline phosphatase on ERK1 phosphorylated VDAC leads to partial recovery of the single-channel VDAC currents. Later, phosphorylation of VDAC was demonstrated by Pro-Q diamond dye. Mass Spectrometric studies indicate phosphorylation of VDAC at Threonine 33, Threonine 55, and Serine 35. In a nutshell, phosphorylation of VDAC leads to the closure of the channel.

Protocol for performing metabolic pathway-based subtyping of breast tumors.

Here, we present a protocol for analyzing the global metabolic landscape in breast tumors for the purpose of metabolism-based patient stratification. We describe steps for analyzing 1,454 metabolic genes representing 90 metabolic pathways and subjecting them to an algorithm that calculates the deregulation score of 90 pathways in each tumor sample, thus converting gene-level information into pathway-level information. We then detail procedures for performing clustering analysis to identify metabolic subtypes and using machine learning to develop a signature representing each subtype. For complete details on the use and execution of this protocol, please refer to Iqbal et al.1.

Nemo-like kinase blocks myeloid differentiation by targeting tumor suppressor C/EBPα in AML.

CCAAT/enhancer-binding protein α (C/EBPα), a key myeloid transcription factor, drives myeloid differentiation from blast cells by regulating the expression of granulocyte colony stimulating factor receptor and C/EBPε as required for promoting granulocyte differentiation. Here, we show that serine/threonine-protein kinase NLK, also known as Nemo-like kinase, physically associates with C/EBPα and phosphorylates it at multiple sites, including Ser21, Thr226, Thr230 and S234, leading to its ubiquitin-mediated degradation. Individual phospho-point mutants of C/EBPα could be phosphorylated by NLK, but a mutant with all phosphorylatable residues replaced by alanine resisted phosphorylation and degradation by NLK, as did the single point mutants. Furthermore, although ectopic expression of NLK enhanced phosphorylation of C/EBPα levels, it markedly inhibited total C/EBPα protein levels. Conversely, NLK depletion inhibited endogenous C/EBPα phosphorylation but enhanced its total protein levels in several acute myeloid leukemia (AML) cell lines and in peripheral blood mononuclear cells isolated from number of AML patient samples. Importantly, NLK depletion in peripheral blood mononuclear cells from primary AML patients not only restored C/EBPα protein levels, but also induced myeloid differentiation, suggesting that NLK could be therapeutically targeted to restore C/EBPα to resolve differentiation arrest in AML.

Voltage dependent anion channel and its interaction with N-acetyl-L-Cysteine (NAC) under oxidative stress on planar lipid bilayer.

Mitochondria are the major source of Hydrogen Peroxide (H2O2), a reactive oxygen species, in the cells. The reactive oxygen species generated by the mitochondria oxidize major proteins including Voltage Dependent Anion Channel (VDAC). We were interested to know how the effect of H2O2 is countered by antioxidants present around the mitochondria. N-Acetyl-l-Cysteine (NAC) is a naturally existing antioxidant in the cells. Keeping this in view, the modulatory effect of antioxidant NAC on H2O2 oxidized VDAC has been investigated through in vitro electrophysiological studies. First, the effect of H2O2 and NAC was studied on independently incorporated single-channel VDAC. It was observed that NAC suppresses VDAC conductance with a half-maximal inhibitory concentration (IC50) of ∼1.04 µM. In contrast, H2O2 enhances VDAC conductance. Later, oxidative stress was induced by H2O2 on VDAC increased conductance with half-maximal effective concentration (EC50) of ∼302 nM. An application of 1 µM NAC on H2O2 treated (300 nM) VDAC reversed the effect of oxidation. In the next step, NAC and H2O2 were added in reverse order. When oxidative stress was induced using H2O2, reduction in conductance by NAC was 4.5 ± 0.404 nS. The change in conductance is nearly 6.3%. However, if antioxidant NAC was incubated first followed by H2O2 treatment, the conductance of VDAC was 3.09 ± 0.27 nS. The change in conductance is near 33%. Both H2O2 and NAC also affected various conducting states of VDAC. In-silico studies indicated the binding of NAC at Lysine and Glutamic acid of VDAC. Hence, NAC was found to be effective in protection of VDAC against H2O2-induced oxidative stress due to its strong binding.

Dexamethasone induces cancer mitigation and irreversible senescence in lung cancer cells via damaging cortical actin and sustained hyperphosphorylation of pRb.

Activation of the glucocorticoid receptors by its cognate ligand, dexamethasone (DEX) is commonly used as an adjuvant treatment in solid tumors. However, its direct effect on cancerous phenotype is not fully understood. We explored the effect and molecular mechanisms of DEX action in lung cancer. In in vitro experiments, DEX treatment causes decrease in migration, invasion and colony formation ability of A549 cells even at lower doses. DEX also decreased adhesion of A549 cells by reducing the formation of cortical actin. Treatment with RU486, a GR antagonist, indicated that these effects are partially mediated through GR. Further; DEX induces G0/G1 arrest of A549 cells. Mechanistically, DEX induces expression of both CDK inhibitors (p21Cip1, p27Kip1) and cyclin-dependent kinases (CDK4, CDK6). Due to this compensatory activation of CDKs and CDKIs, DEX induces the hyper phosphorylation state of Rb protein (pRb) leading to irreversible senescence as confirmed by ß-gal staining. Next, in clinical dataset of NSCLC (Non-small cell lung cancer), GR was lowly expressed in cancer patients as compared to the normal group, where higher expression of GR led to higher overall survival of NSCLC indicating for a protective role of GR. Interestingly, when combined with chemotherapeutic agents, DEX can modulate the drug-sensitivity of cells. Taken together, these data indicate that DEX through GR activation may suppress tumor growth by decreasing proliferation and inducing irreversible senescence and combination of standard chemotherapy and DEX can be a potential treatment for NSCLC.

Metabolic stratification of human breast tumors reveal subtypes of clinical and therapeutic relevance.

Extensive metabolic heterogeneity in breast cancers has limited the deployment of metabolic therapies. To enable patient stratification, we studied the metabolic landscape in breast cancers (∼3000 patients combined) and identified three subtypes with increasing degrees of metabolic deregulation. Subtype M1 was found to be dependent on bile-acid biosynthesis, whereas M2 showed reliance on methionine pathway, and M3 engaged fatty-acid, nucleotide, and glucose metabolism. The extent of metabolic alterations correlated strongly with tumor aggressiveness and patient outcome. This pattern was reproducible in independent datasets and using in vivo tumor metabolite data. Using machine-learning, we identified robust and generalizable signatures of metabolic subtypes in tumors and cell lines. Experimental inhibition of metabolic pathways in cell lines representing metabolic subtypes revealed subtype-specific sensitivity, therapeutically relevant drugs, and promising combination therapies. Taken together, metabolic stratification of breast cancers can thus aid in predicting patient outcome and designing precision therapies.

Calmodulin Modulates the Gating Properties of Voltage-Dependent Anion Channel from Rat Brain Mitochondria.

Calmodulin (CaM) is a key signaling protein that plays a decisive role in mitochondrial Ca2+ homeostasis and signaling and modulates the mitochondrial membrane properties. We propose that voltage-dependent anion channel 1 (VDAC1), one of the most abundant outer mitochondrial membrane (OMM) proteins, could be its possible target or site of action. VDAC1 is known to play a crucial role in the mitochondrial Ca2+ signaling mechanism. Bilayer electrophysiology experiments show that CaM significantly reduces VDAC1's conductivity and modulates its gating as well as permeability properties. Also, spectrofluorimetric analysis indicates the possibility of binding CaM with VDAC1. Theoretical analysis of fluorescence data shows that the aforementioned protein-protein interaction is not linear, but rather it is a complex nonlinear process. In VDAC1, CaM binding site has been predicted using various bioinformatics tools. It is proposed that CaM could interact with VDAC1's outer-loop region and regulate its gating properties. Our findings suggest that VDAC1-CaM interaction could play a crucial role in the transport of ions and metabolites through the OMM and the regulation of the mitochondrial Ca2+ signaling mechanism through alteration of VDAC1's gating and conductive properties.

Phytocompounds Targeting Metabolic Reprogramming in Cancer: An Assessment of Role, Mechanisms, Pathways, and Therapeutic Relevance.

The metabolism of cancer is remarkably different from that of normal cells and confers a variety of benefits, including the promotion of other cancer hallmarks. As the rewired metabolism is a near-universal property of cancer cells, efforts are underway to exploit metabolic vulnerabilities for therapeutic benefits. In the continued search for safer and effective ways of cancer treatment, structurally diverse plant-based compounds have gained substantial attention. Here, we present an extensive assessment of the role of phytocompounds in modulating cancer metabolism and attempt to make a case for the use of plant-based compounds in targeting metabolic vulnerabilities of cancer. We discuss the pharmacological interactions of phytocompounds with major metabolic pathways and evaluate the role of phytocompounds in the regulation of growth signaling and transcriptional programs involved in the metabolic transformation of cancer. Lastly, we examine the potential of these compounds in the clinical management of cancer along with limitations and challenges.

Silibinin induces metabolic crisis in triple-negative breast cancer cells by modulating EGFR-MYC-TXNIP axis: potential therapeutic implications.

Triple-negative breast cancer (TNBC) is an aggressive form of breast cancer with limited treatment modalities and poor prognosis. Metabolic reprogramming in cancer is considered a hallmark of therapeutic relevance. Here, we report disruption of metabolic reprogramming in TNBC cells by silibinin via modulation of EGFR-MYC-TXNIP signaling. Metabolic assays combined with LC-MS-based metabolomics revealed inhibition of glycolysis and other key biosynthetic pathways by silibinin, to induce metabolic catastrophe in TNBC cells. Silibinin-induced metabolic suppression resulted in decreased cell biomass, proliferation, and stem cell properties. Mechanistically, we identify EGFR-MYC-TXNIP as an important regulator of TNBC metabolism and mediator of inhibitory effects of silibinin. Highlighting the clinical relevance of our observations, the analysis of METABRIC dataset revealed deregulation of EGFR-MYC-TXNIP axis in TNBC and association of EGFRhigh -MYChigh -TXNIPlow signature with aggressive glycolytic metabolism and poor disease-specific and metastasis-free survival. Importantly, combination treatment of silibinin or 2-deoxyglucose (glycolysis inhibitor) with paclitaxel synergistically inhibited proliferation of TNBC cells. Together, our results highlight the importance of EGFR-MYC-TXNIP axis in regulating TNBC metabolism, demonstrate the anti-TNBC activity of silibinin, and argue in favor of targeting metabolic vulnerabilities of TNBC, at least in combination with mainstay chemotherapeutic drugs, to effectively treat TNBC patients.

Multiomics integrative analysis reveals antagonistic roles of CBX2 and CBX7 in metabolic reprogramming of breast cancer.

Striking similarity exists between metabolic changes associated with embryogenesis and tumorigenesis. Chromobox proteins-CBX2/4/6/7/8, core components of canonical polycomb repressor complex 1, play essential roles in embryonic development and aberrantly expressed in breast cancer. Understanding how altered CBX expression relates to metabolic reprogramming in breast cancer may reveal vulnerabilities of therapeutic pertinence. Using transcriptomic and metabolomic data from breast cancer patients (N > 3000 combined), we performed pathway-based analysis and identified outstanding roles of CBX2 and CBX7 in positive and negative regulation of glucose metabolism, respectively. Genetic ablation experiments validated the contrasting roles of two isoforms in cancer metabolism and cell growth. Furthermore, we provide evidence for the role of mammalian target of rapamycin complex 1 signaling in mediating contrary effects of CBX2 and CBX7 on breast cancer metabolism. Underpinning the biological significance of metabolic roles, CBX2 and CBX7 were found to be the most up- and downregulated isoforms, respectively, in breast tumors compared with normal tissues. Moreover, CBX2 and CBX7 expression (not other isoforms) correlated strongly, but oppositely, with breast tumor subtype aggressiveness and the proliferation markers. Consistently, genomic data also showed higher amplification frequency of CBX2, not CBX7, in breast tumors. Highlighting the clinical significance of findings, disease-specific survival and drug sensitivity analysis revealed that CBX2 and CBX7 predicted patient outcome and sensitivity to FDA-approved/investigational drugs. In summary, this work identifies novel cross talk between CBX2/7 and breast tumor metabolism, and the results presented may have implications in strategies targeting breast cancer.

The effect of amantadine on an ion channel protein from Chikungunya virus.

Viroporins like influenza A virus M2, hepatitis C virus p7, HIV-1 Vpu and picornavirus 2B associate with host membranes, and create hydrophilic corridors, which are critical for viral entry, replication and egress. The 6K proteins from alphaviruses are conjectured to be viroporins, essential during egress of progeny viruses from host membranes, although the analogue in Chikungunya Virus (CHIKV) remains relatively uncharacterized. Using a combination of electrophysiology, confocal and electron microscopy, and molecular dynamics simulations we show for the first time that CHIKV 6K is an ion channel forming protein that primarily associates with endoplasmic reticulum (ER) membranes. The ion channel activity of 6K can be inhibited by amantadine, an antiviral developed against the M2 protein of Influenza A virus; and CHIKV infection of cultured cells can be effectively inhibited in presence of this drug. Our study provides crucial mechanistic insights into the functionality of 6K during CHIKV-host interaction and suggests that 6K is a potential therapeutic drug target, with amantadine and its derivatives being strong candidates for further development.

Cervical cancer awareness and HPV vaccine acceptability among females in Delhi: A cross-sectional study.

AIMS: The aim of this study is to assess the awareness about cervical cancer and the acceptability of cytological screening and vaccine against human papilloma virus (HPV) among women in Delhi, the national capital of India. MATERIALS AND METHODS: A cross-sectional survey of women was conducted in Delhi to assess the awareness of cervical cancer and acceptability of Papanicolaou (Pap) test and HPV vaccine. The sample size of the population was 450, and a pre-tested questionnaire was administered to them. RESULTS: Majority of the participants (85.11%) were aware of cervical cancer and were willing to undergo diagnosis by Pap test (84.6%). As far as vaccination was concerned, 63.14% found the HPV vaccine acceptable for their daughters. However, very few participants were willing to vaccinate themselves against HPV. CONCLUSION: The high awareness among females in Delhi about cervical cancer and acceptability of screening programs, if done free of cost, shows a positive trend. The only inhibition about HPV vaccine was primarily due to concerns about postvaccination complications. However, inclusion of HPV vaccine in Government-sponsored immunization program would go a long way in increasing the acceptability of the vaccine.