An update on transcriptional and post-translational regulation of brain voltage-gated sodium channels

Voltage-gated sodium channels are essential proteins in brain physiology, as they generate the sodium currents that initiate neuronal action potentials. Voltage-gated sodium channels expression, localisation and function are regulated by a range of transcriptional and post-translational mechanisms. Here, we review our understanding of regulation of brain voltage-gated sodium channels, in particular SCN1A (Naᵥ1.1), SCN2A (Naᵥ1.2), SCN3A (Naᵥ1.3) and SCN8A (Naᵥ1.6), by transcription factors, by alternative splicing, and by post-translational modifications. Our focus is strongly centred on recent research lines, and newly generated knowledge

Interplay between R513 methylation and S516 phosphorylation of the cardiac voltage-gated sodium channel

Arginine methylation is a novel post-translational modification within the voltage-gated ion channel superfamily, including the cardiac sodium channel, Naᵥ1.5. We show that Naᵥ1.5 R513 methylation decreases S516 phosphorylation rate by 4 orders of magnitude, the first evidence of protein kinase A inhibition by arginine methylation. Reciprocally, S516 phosphorylation blocks R513 methylation. Naᵥ1.5 p.G514C, associated to cardiac conduction disease, abrogates R513 methylation, while leaving S516 phosphorylation rate unchanged. This is the first report of methylation–phosphorylation cross-talk of a cardiac ion channel

Capturing the industrial requirements of set-based design for CONGA framework

The Configuration Optimisation of Next-Generation Aircraft (CONGA) is a proposed framework in a response industrial need to enhance the aerospace capability in the UK. In order to successfully address this challenge, a need to develop a true multi-disciplinary Set-Based Design (SBD) capability that could deploy new technologies on novel configurations more quickly and with greater confidence was identified. This paper presents the first step towards the development of the SBD capabilities which is to elicit the industrial requirement of the SBD process for the key aerospace industrial partners involved in this CONGA approach

Capturing the Industrial Requirements of Set-Based Design for the CONGA Framework

The Configuration Optimisation of Next-Generation Aircraft (CONGA) is a proposed framework in a response to industrial need to enhance the aerospace capability in the UK. In order to successfully address this challenge, a need to develop a true multi-disciplinary Set-Based Design (SBD) capability that could deploy new technologies on novel configurations more quickly and with greater confidence was identified. This paper presents the first step towards the development of the SBD capabilities which is to elicit the industrial requirement of the SBD process for the key aerospace industrial partners involved in this CONGA approach

Mapping arginine methylation in the human body and cardiac disease

Purpose Arginine methylation (ArgMe) is one of the most ubiquitous post-translational modifications, and hundreds of proteins undergo ArgMe in e.g. brain. However, the scope of ArgMe in many tissues, including the heart, is currently under explored. Here, we aimed to 1) identify proteins undergoing ArgMe in human organs, and 2) expose the relevance of ArgMe in cardiac disease. Experimental design We used publicly available proteomic data to search for ArgMe in 13 human tissues. We used glucose to induce H9c2 cardiac-like cell hypertrophy. Results Our results show that ArgMe is mainly tissue-specific; nevertheless, we suggest an embryonic origin of core ArgMe events. In the heart, we found 103 mostly novel ArgMe sites in 58 non-histone proteins. We provide compelling evidence that cardiac protein ArgMe is relevant to cardiomyocyte ontology, and important for proper cardiac function. This is highlighted by the fact that genetic mutations affecting methylated arginine positions are often associated with cardiac disease, including hypertrophic cardiomyopathy. We provide pilot experimental data suggesting significant changes in ArgMe profiles of H9c2 cells upon induction of cell hypertrophy using glucose. Conclusions and clinical relevance Our work calls for in-depth investigation of ArgMe in normal and diseased tissues, using methods including clinical proteomics

Inhibiting arginine methylation as a tool to investigate cross-talk with methylation and acetylation post-translational modifications in a glioblastoma cell line

Glioblastomas (GBM) are the most common grade 4 brain tumours; patients have very poor prognosis with an average survival of 15 months after diagnosis. Novel research lines have begun to explore aberrant protein arginine methylation (ArgMe) as a possible therapeutic target in GBM and ArgMe inhibitors are currently in clinical trials. Enzymes known as protein arginine methyltransferases (PRMT1-9) can lead to mono-or di-ArgMe, and in the latter case symmetric or asymmetric dimethylation (SDMA and ADMA, respectively). Using the most common GBM cell line, we have profiled the expression of PRMTs, used ArgMe inhibitors as tools to investigate post-translational modifications cross-talk and measured the effect of ArgMe inhibitors on cell viability. We have identified novel SDMA events upon inhibition of ADMA in GBM cells and spheroids. We have observed cross-talk between ADMA and lysine acetylation in GBM cells and platelets. Treatment of GBM cells with furamidine, a PRMT1 inhibitor, reduces cell viability in 2D and 3D models. These data provide new molecular understanding of a disease with unmet clinical needs

Boron doped TiO2 catalysts for photocatalytic ozonation of aqueous mixtures of common pesticides: Diuron, o-phenylphenol, MCPA and terbuthylazine

Photocatalysts were characterized by ICP-EOS, N2 adsorption-desorption, XRD, XPS, and DR-UV-Vis spectroscopy. Four recalcitrant herbicides and pesticides (diuron, o-phenylphenol, 2-methyl-4-chlorophenoxyacetic acid (MCPA) and terbuthylazine) were subjected to degradation by ozonation, photolytic ozonation, photocatalysis and photocatalytic ozonation using the prepared catalysts under simulated solar irradiation in a laboratory scale system. The boron that was not incorporated to the TiO2 interstitial positions was unstable and leached to the solution. The washed B-doped TiO2 catalysts, with 0.5-0.8 wt.% of interstitial boron were more active than bare TiO2 for the removal and mineralization of the target compounds. The combination of ozonation and photocatalysis led to faster mineralization rates and allowed the complete removal of the pesticides below the regulatory standards. The B-doped catalyst was stable and maintained 75% mineralization after 3 consecutive runs

Do sodium channel proteolytic fragments regulate sodium channel expression?

© 2017 Taylor & Francis The cardiac voltage-gated sodium channel (gene: SCN5A, protein: Na V 1.5) is responsible for the sodium current that initiates the cardiomyocyte action potential. Research into the mechanisms of SCN5A gene expression has gained momentum over the last few years. We have recently described the transcriptional regulation of SCN5A by GATA4 transcription factor. In this addendum to our study, we report our observations that 1) the linker between domains I and II (L DI-DII ) of Na V 1.5 contains a nuclear localization signal (residues 474–481) that is necessary to localize L DI-DII into the nucleus, and 2) nuclear L DI-DII activates the SCN5A promoter in gene reporter assays using cardiac-like H9c2 cells. Given that voltage-gated sodium channels are known targets of proteases such as calpain, we speculate that Na V 1.5 degradation is signaled to the cell transcriptional machinery via nuclear localization of L DI-DII and subsequent stimulation of the SCN5A promoter

Identification of N-terminal protein acetylation and arginine methylation of the voltage-gated sodium channel in end-stage heart failure human heart

The α subunit of the cardiac voltage-gated sodium channel, Naᵥ1.5, provides the rapid sodium inward current that initiates cardiomyocyte action potentials. Here, we analyzed for the first time the post-translational modifications of Naᵥ1.5 purified from end-stage heart failure human cardiac tissue. We identified R526 methylation as the major post-translational modification of any Naᵥ1.5 arginine or lysine residue. Unexpectedly, we found that the N terminus of Naᵥ1.5 was: 1) devoid of the initiation methionine, and 2) acetylated at the resulting initial alanine residue. This is the first evidence for N-terminal acetylation in any member of the voltage-gated ion channel superfamily. Our results open the door to explore Naᵥ1.5 N-terminal acetylation and arginine methylation levels as drivers or markers of end-stage heart failure

The Epigenetic Regulatory Protein CBX2 Promotes mTORC1 Signalling and Inhibits DREAM Complex Activity to Drive Breast Cancer Cell Growth

Chromobox 2 (CBX2) is a chromatin-binding component of polycomb repressive complex 1, which causes gene silencing. CBX2 expression is elevated in triple-negative breast cancer (TNBC), for which there are few therapeutic options. Here, we aimed to investigate the functional role of CBX2 in TNBC. CBX2 knockdown in TNBC models reduced cell numbers, which was rescued by ectopic expression of wild-type CBX2 but not a chromatin binding-deficient mutant. Blocking CBX2 chromatin interactions using the inhibitor SW2_152F also reduced cell growth, suggesting CBX2 chromatin binding is crucial for TNBC progression. RNA sequencing and gene set enrichment analysis of CBX2-depleted cells identified downregulation of oncogenic signalling pathways, including mTORC1 and E2F signalling. Subsequent analysis identified that CBX2 represses the expression of mTORC1 inhibitors and the tumour suppressor RBL2. RBL2 repression, in turn, inhibits DREAM complex activity. The DREAM complex inhibits E2F signalling, causing cell senescence; therefore, inhibition of the DREAM complex via CBX2 may be a key oncogenic driver. We observed similar effects in oestrogen receptor-positive breast cancer, and analysis of patient datasets suggested CBX2 inhibits RBL2 activity in other cancer types. Therapeutic inhibition of CBX2 could therefore repress mTORC1 activation and promote DREAM complex-mediated senescence in TNBC and could have similar effects in other cancer types