Large T-antigen up-regulates Kv4.3 K⁺ channels through Sp1, and Kv4.3 K⁺ channels contribute to cell apoptosis and necrosis through activation of calcium/calmodulin-dependent protein kinase II

Functional Annotation of Hypothetical Proteins From the Enterobacter cloacae B13 Strain and Its Association With Pathogenicity

Enterobacter cloacae B13 strain is a rod-shaped gram-negative bacterium that belongs to the Enterobacteriaceae family. It can cause respiratory and urinary tract infections, and is responsible for several outbreaks in hospitals. E. cloacae has become an important pathogen and an emerging global threat because of its opportunistic and multidrug resistant ability. However, little knowledge is present about a large portion of its proteins and functions. Therefore, functional annotation of the hypothetical proteins (HPs) can provide an improved understanding of this organism and its virulence activity. The workflow in the study included several bioinformatic tools which were utilized to characterize functions, family and domains, subcellular localization, physiochemical properties, and protein-protein interactions. The E. cloacae B13 strain has overall 604 HPs, among which 78 were functionally annotated with high confidence. Several proteins were identified as enzymes, regulatory, binding, and transmembrane proteins with essential functions. Furthermore, 23 HPs were predicted to be virulent factors. These virulent proteins are linked to pathogenesis with their contribution to biofilm formation, quorum sensing, 2-component signal transduction or secretion. Better knowledge about the HPs’ characteristics and functions will provide a greater overview of the proteome. Moreover, it will help against E. cloacae in neonatal intensive care unit (NICU) outbreaks and nosocomial infections.

Over-expression of Kv4.3 gene reverses cardiac remodeling and transient-outward K+ current (Ito) reduction via CaMKII inhibition in myocardial infarction

OBJECTIVE

Previous study has shown that Kv4.3, a main coding subunit generating cardiac transient-outward K⁺ current (Ito), can inhibit Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) activity. Based on these observations, we speculate that over-expression of Kv4.3 gene could reverse not only Ito reduction but also cardiac remodeling in the rat myocardial infarction (MI) model.

METHODS AND RESULTS

Healthy male Sprague-Dawley (SD) rats were used to establish MI model by ligation of left anterior descending coronary artery, and adenovirus integrated with Kv4.3 gene (AD-Kv4.3) was delivered in infarct border zone by intramyocardial injection. The hearts were harvested for histological analysis (HE or Masson trichrome staining), western blot or patch clamp 4 weeks after MI. Our data showed that the application of AD-Kv4.3 could reduce myocardial infarct size and fibrosis, and its cardioprotective effects were similar with medicine therapy (combination of metoprolol and captopril). Moreover, Kv4.3 over-expression significantly improved MI-induced cardiac dysfunction and enhanced Ito density while decreasing corrected QT (QTc) intervals and cardiac electrophysiological instability. Western blot showed that Kv4.3 transfection reduced CaMKII, PLB-17 and ryanodine receptor2 (RyR2 Ser2814) phosphorylation level, at same time increased SERCA2 expression dramatically.

CONCLUSION

Over-expression of Kv4.3 can not only attenuate cardiac electrophysiological instability and cardiac performance, but also reduce myocardial infarct area and cardiac fibrosis. Like traditional anti-remodeling therapy-angiotensin converting enzyme inhibitor (ACEI) combined with β-adrenergic receptor blocker, over-expression of Kv4.3 seems to be an effective and safe therapy for both structural and electrical remodeling induced by MI via CaMKII inhibition.

Probucol-induced hERG Channel Reduction can be Rescued by Matrine and Oxymatrine in vitro

Background

The human ether-a-go-go-related gene (hERG) potassium channel is the rapidly activating component of cardiac delayed rectifier potassium current (I_Kr), which is a crucial determinant of cardiac repolarization. The reduction of hERG current is commonly believed to cause Long QT Syndrome (LQTs). Probucol, a cholesterol-lowering drug, induces LQTs by inhibiting the expression of the hERG channel. Unfortunately, there is currently no effective therapeutic method to rescue probucol-induced LQTs.

Methods

Patch-clamp recording techniques were used to detect the action potential duration (APD) and current of hERG. Western blot was performed to measure the expression levels of proteins.

Results

In this study, we demonstrated that 1 μM matrine and oxymatrine could rescue the hERG current and hERG surface expression inhibited by probucol. In addition, matrine and oxymatrine significantly shortened the prolonged action potential duration induced by probucol in neonatal cardiac myocytes. We proposed a novel mechanism underlying the probucol induced decrease in the expression of transcription factor Specificity protein 1 (Sp1), which is an established transactivator of the hERG gene. We also demonstrated that matrine and oxymatrine were able to upregulate Sp1 expression which may be one of the possible mechanisms by which matrine and oxymatrine rescued probucol-induced hERG channel deficiency.

Conclusion

Our current results demonstrate that matrine and oxymatrine could rescue probucol-induced hERG deficiency in vitro, which may lead to potentially effective therapeutic drugs for treating acquired LQT2 by probucol in the future.

KCND2 upregulation might be an independent indicator of poor survival in gastric cancer

AIM

We aimed to investigate the expression of voltage-gated potassium channels KCND1/KCND2/KCND3 in gastric cancer (GC) and normal stomach tissues and to investigate the prognostic value of the upregulated gene KCND2.

PATIENTS & METHODS

A retrospective analysis was performed using data from large available databases.

RESULTS

KCND2 was significantly upregulated at the mRNA and protein levels in GC compared with that in normal stomach tissues. High KCND2 RNA expression was independently associated with shorter overall survival (HR: 1.634, 95% CI: 1.135-2.352; p = 0.008) and recurrence-free survival (HR: 2.644, 95% CI: 1.438-4.863; p = 0.002). Data mining in the Kaplan-Meier plotter confirmed the prognostic value of KCND2.

CONCLUSION

KCND2 upregulation is a valuable prognostic biomarker in GC patients, in terms of overall survival and recurrence-free survival.

Silibinin sensitizes TRAIL-mediated apoptosis by upregulating DR5 through ROS-induced endoplasmic reticulum stress-Ca2+-CaMKII-Sp1 pathway

In this study, we addressed how silibinin enhances tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis in various cancer cells. Combined treatment with silibinin and TRAIL (silibinin/TRAIL) induced apoptosis accompanied by the activation of caspase-3, caspase-8, caspase-9, and Bax, and cytosolic accumulation of cytochrome c. Anti-apoptotic proteins such as Bcl-2, IAP-1, and IAP-2 were inhibited as well. Silibinin also triggered TRAIL-induced apoptosis in A549 cells through upregulation of death receptor 5 (DR5). Pretreatment with DR5/Fc chimeric protein and DR5-targeted small interfering RNA (siRNA) significantly blocked silibinin/TRAIL-mediated apoptosis in A549 cells. Furthermore, silibinin increased the production of reactive oxygen species (ROS), which led to the induction of TRAIL-mediated apoptosis through DR5 upregulation. Antioxidants such as N-acetyl-L-cysteine and glutathione reversed the apoptosis-inducing effects of TRAIL. Silibinin further induced endoplasmic reticulum (ER) stress as was indicated by the increase in ER marker proteins such as PERK, eIF2α, and ATF-4, which stimulate the expression of CCAAT/enhancer binding protein homologous protein (CHOP). CHOP-targeted siRNA eliminated the induction of DR5 and resulted in a significant decrease in silibinin/TRAIL-mediated apoptosis. We also found that silibinin/TRAIL-induced apoptosis was accompanied with intracellular influx of Ca²⁺, which was stimulated by ER stress and the Ca²⁺ chelator, ethylene glycol tetraacetic acid (EGTA). Ca²⁺/calmodulin-dependent protein kinase (CaMKII) inhibitor, K252a, blocked silibinin/TRAIL-induced DR5 expression along with TRAIL-mediated apoptosis. Accordingly, we showed that ROS/ER stress-induced CaMKII activated Sp1, which is an important transcription factor for DR5 expression. Our results showed that silibinin enhanced TRAIL-induced apoptosis by upregulating DR5 expression through the ROS-ER stress-CaMKII-Sp1 axis.

(-)-Epicatechin rescues the As2 O3 -induced HERG K+ channel deficiency possibly through upregulating transcription factor SP1 expression

(-)-Epicatechin (EPI) has beneficial effects on the cardiovascular disease. The human ether-a-go-go-related gene (HERG) potassium channel is crucial for repolarization of cardiac action potential. Dysfunction of the HERG channel can cause long QT syndrome type 2 (LQT2). Arsenic trioxide (As2 O3 ) has shown efficacy in the treatment of acute promyelocytic leukemia. However, As2 O3 can induce the deficiency of HERG channel and cause LQT2. In this study, we examined whether EPI could rescue the As2 O3 -induced HERG channel deficiency. We found that 3 μM EPI obviously increased protein expression and current of HERG channel. EPI was able to recover the protein expression and current of HERG channel disrupted by As2 O3 . EPI was able to increase the expression of SP1 protein and recover the expression of SP1 protein disrupted by As2 O3 . In addition, EPI significantly shortened action potential duration prolonged by As2 O3 . Our data suggest that EPI rescues As2 O3 -induced HERG channel deficiency through upregulating SP1 expression.

Metal ions influx is a double edged sword for the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a common form of dementia in aged people, which is defined by two pathological characteristics: β-amyloid protein (Aβ) deposition and tau hyperphosphorylation. Although the mechanisms of AD development are still being debated, a series of evidence supports the idea that metals, such as copper, iron, zinc, magnesium and aluminium, are involved in the pathogenesis of the disease. In particular, the processes of Aβ deposition in senile plaques (SP) and the inclusion of phosphorylated tau in neurofibrillary tangles (NFTs) are markedly influenced by alterations in the homeostasis of the aforementioned metal ions. Moreover, the mechanisms of oxidative stress, synaptic plasticity, neurotoxicity, autophagy and apoptosis mediate the effects of metal ions-induced the aggregation state of Aβ and phosphorylated tau on AD development. More importantly, imbalance of these mechanisms finally caused cognitive decline in different experiment models. Collectively, reconstructing the signaling network that regulates AD progression by metal ions may provide novel insights for developing chelators specific for metal ions to combat AD.

Silencing of voltage-gated potassium channel KV9.3 inhibits proliferation in human colon and lung carcinoma cells

Voltage-gated potassium (K_v) channels are known to be involved in cancer development and cancer cell proliferation. K_V9.3, an electronically silent subunit, forms heterotetramers with K_V2.1 in excitable cells and modulates its electrophysiological properties. However, the role of K_V9.3 alone in non-excitable cancer cells has not been studied. Here, we evaluated the effect of silencing K_V9.3 on cancer cell proliferation in HCT15 colon carcinoma cells and A549 lung adenocarcinoma cells. We confirmed the expression of K_V9.3 mRNA in HCT15 and A549 cells and showed that silencing K_V9.3 using small interfering RNA caused G0/G1 cell cycle arrest and alterations in cell cycle regulatory proteins in both HCT15 and A549 cells without affecting apoptosis. Also, stable knockdown of K_V9.3 expression using short-hairpin RNA inhibited tumor growth in SCID mouse xenograft model. Using a bioinformatics approach, we identified Sp1 binding sites in the promoter region of the gene encoding K_V9.3. We further found that Sp1 bound to this region and showed that the Sp1 inhibitor, mithramycin A, induced a concentration-dependent decrease in K_V9.3 expression. Taken together, these data suggest that knockdown of K_V9.3 inhibits proliferation in colon carcinoma and lung adenocarcinoma cell lines and may be regulated by Sp1.

The potential role of Kv4.3 K+ channel in heart hypertrophy

Transient outward K+ current (I(to)) plays a crucial role in the early phase of cardiac action potential repolarization. Kv4.3 K(+) channel is an important component of I(to). The function and expression of Kv4.3 K(+) channel decrease in variety of heart diseases, especially in heart hypertrophy/heart failure. Int his review, we summarized the changes of cardiac Kv4.3 K(+) channel in heart diseases and discussed the potential role of Kv4.3 K(+) channel in heart hypertrophy/heart failure. In heart hypertrophy/heart failure of mice and rats, down regulation of Kv4.3 K(+) channel leads to prolongation of action potential duration (APD), which is associated with increased [Ca(2+)](I), activation of calcineurin and heart hypertrophy/heart failure.However, in canine and human, Kv4.3 K(+) channel does not play a major role in setting cardiac APD. So, in addition to Kv4.3 K(+) channel/APD/[Ca(2+)](I) pathway, there exits another mechanism of Kv4.3 K(+) channel in heart hypertrophy and heart failure: downregulation of Kv4.3 K(+) channels leads to CaMKII dissociation from Kv4.3–CaMKII complex and subsequent activation of the dissociated CaMKII , which induces heart hypertrophy/heart failure. Upregulation of Kv4.3K(+) channel inhibits CaMKII activation and its related harmful consequences. We put forward a new point-of-view that Kv4.3 K(+) channel is involved in heart hypertrophy/heart failure independently of its electric function, and drugs inhibiting or upregulating Kv4.3 K(+) channel might be potentially harmful or beneficial to hearts through CaMKII.

Nuclear localization and functional characteristics of voltage-gated potassium channel Kv1.3

It is widely known that ion channels are expressed in the plasma membrane. However, a few studies have suggested that several ion channels including voltage-gated K(+) (Kv) channels also exist in intracellular organelles where they are involved in the biochemical events associated with cell signaling. In the present study, Western blot analysis using fractionated protein clearly indicates that Kv1.3 channels are expressed in the nuclei of MCF7, A549, and SNU-484 cancer cells and human brain tissues. In addition, Kv1.3 is located in the plasma membrane and the nucleus of Jurkat T cells. Nuclear membrane hyperpolarization after treatment with margatoxin (MgTX), a specific blocker of Kv1.3 channels, provides evidence for functional channels at the nuclear membrane of A549 cells. MgTX-induced hyperpolarization is abolished in the nuclei of Kv1.3 silenced cells, and the effects of MgTX are dependent on the magnitude of the K(+) gradient across the nuclear membrane. Selective Kv1.3 blockers induce the phosphorylation of cAMP response element-binding protein (CREB) and c-Fos activation. Moreover, Kv1.3 is shown to form a complex with the upstream binding factor 1 in the nucleus. Chromatin immunoprecipitation assay reveals that Sp1 transcription factor is directly bound to the promoter region of the Kv1.3 gene, and the Sp1 regulates Kv1.3 expression in the nucleus of A549 cells. These results demonstrate that Kv1.3 channels are primarily localized in the nucleus of several types of cancer cells and human brain tissues where they are capable of regulating nuclear membrane potential and activation of transcription factors, such as phosphorylated CREB and c-Fos.

Neuroprotective or neurotoxic effects of 4-aminopyridine mediated by KChIP1 regulation through adjustment of Kv 4.3 potassium channels expression and GABA-mediated transmission in primary hippocampal cells

4-Aminopyridine (4-AP) is a potassium channel blocker used for the treatment of neuromuscular disorders. Otherwise, it has been described to produce a large number of adverse effects among them cell death mediated mainly by blockage of K(+) channels. However, a protective effect against cell death has also been described. On the other hand, Kv channel interacting protein 1 (KChIP1) is a neuronal calcium sensor protein that is predominantly expressed at GABAergic synapses and it has been related with modulation of K(+) channels, GABAergic transmission and cell death. According to this KChIP1 could play a key role in the protective or toxic effects induced by 4-AP. We evaluated, in wild type and KChIP1 silenced primary hippocampal neurons, the effect of 4-AP (0.25μM to 2mM) with or without semicarbazide (0.3M) co-treatment after 24h and after 14 days 4-AP alone exposure on cell viability, the effect of 4-AP (0.25μM to 2mM) on KChIP1 and Kv 4.3 potassium channels gene expression and GABAergic transmission after 24h treatment or after 14 days exposure to 4-AP (0.25μM to1μM). 4-AP induced cell death after 24h (from 1mM) and after 14 days treatment. We observed that 4-AP modulates KChIP1 which regulate Kv 4.3 channels expression and GABAergic transmission. Our study suggests that KChIP1 is a key gene that has a protective effect up to certain concentration after short-term treatment with 4-AP against induced cell injury; but this protection is erased after long term exposure, due to KChIP1 down-regulation predisposing cell to 4-AP induced damages. These data might help to explain protective and toxic effects observed after overdose and long term exposure.

Delineating the regulation of energy homeostasis using hypothalamic cell models

Attesting to its intimate peripheral connections, hypothalamic neurons integrate nutritional and hormonal cues to effectively manage energy homeostasis according to the overall status of the system. Extensive progress in the identification of essential transcriptional and post-translational mechanisms regulating the controlled expression and actions of hypothalamic neuropeptides has been identified through the use of animal and cell models. This review will introduce the basic techniques of hypothalamic investigation both in vivo and in vitro and will briefly highlight the key advantages and challenges of their use. Further emphasis will be place on the use of immortalized models of hypothalamic neurons for in vitro study of feeding regulation, with a particular focus on cell lines proving themselves most fruitful in deciphering fundamental basics of NPY/AgRP, Proglucagon, and POMC neuropeptide function.

DMH1 increases glucose metabolism through activating Akt in L6 rat skeletal muscle cells

DMH1(4-[6-(4-Isopropoxyphenyl)pyrazolo [1,5-a]pyrimidin-3-yl] quinoline) is a compound C analogue with the structural modifications at the 3- and 6-positions in pyrazolo[1,5-a]pyrimidine backbone. Compound C was reported to inhibit both AMPK and Akt. Our preliminary work found that DMH1 activated Akt. Since Akt was involved in glucose metabolism, we aimed to identify the effects of DMH1 on glucose metabolism in L6 rat muscle cells and the potential mechanism. Results showed that DMH1 increased lactic acid release and glucose consumption in L6 rat muscle cells in a dose-dependent manner. DMH1 activated Akt in L6 cells. Akt inhibitor inhibited DMH1-induced Akt activation and DMH1-induced increases of glucose uptake and consumption. DMH1 had no cytotoxicity in L6 cells, but inhibited mitochondrial function and reduced ATP production. DMH1 showed no effect on AMPK, but in the presence of Akt inhibitor, DMH1 significantly activated AMPK. Compound C inhibited DMH1-induced Akt activation in L6 cells. Compound C inhibited DMH1-induced increase of glucose uptake, consumption and lactic acid release in L6 cells. DMH1 inhibited PP2A activity, and PP2A activator forskolin reversed DMH1-induced Akt activation. We concluded that DMH1 increased glucose metabolism through activating Akt and DMH1 activated Akt through inhibiting PP2A activity in L6 rat muscle cells. In view of the analogue structure of DMH1 and compound C and the contrasting effects of DMH1 and compound C on Akt, the present study provides a novel leading chemical structure targeting Akt with potential use for regulating glucose metabolism.

Bone morphogenetic protein-2 antagonizes bone morphogenetic protein-4 induced cardiomyocyte hypertrophy and apoptosis

Our previous work showed that the expression of bone morphogenetic protein-4 (BMP4) was up-regulated in pathological cardiac hypertrophy models and BMP4 induced cardiomyocyte hypertrophy and apoptosis. Bone morphogenetic protein-2 (BMP2) and BMP4 share greater than 80% amino acid homology and there exists an interaction between BMP2 and BMP4, so the aim of the present study was to elucidate the changes of BMP2 in the cardiac hypertrophy models and the effects of BMP2 on BMP4-induced cardiomyocyte hypertrophy and apoptosis. The in vivo cardiac hypertrophy models were induced by pressure-overload and swimming exercise in mice. BMP2 mRNA and protein expressions increased in pressure-overload and swimming-exercise induced cardiac hypertrophy. BMP2 itself did not elicit cardiomyocyte hypertrophy and apoptosis, but antagonized BMP4-induced cardiomyocyte hypertrophy and apoptosis. BMP2 stimulated Akt in cardiomyocytes and Akt inhibitor prevented the antagonism of BMP2 on BMP4-induced cardiomyocyte apoptosis. Furthermore, BMP2 inhibited BMP4-induced JNK activation in cardiomyocytes. In conclusion, BMP2 antagonizes BMP4-induced cardiomyocyte hypertrophy and apoptosis. The anti-apoptotic effects of BMP2 on BMP4-induced cardiomyocyte apoptosis might be through activating Akt and inhibiting JNK activation.

Bone morphogenetic protein-4 induces upregulation of Cav3.1 Ca²⁺ channels in HL-1 atrial myocytes

Cardiac T-type Ca(2+) channels are reexpressed in atrial and ventricular myocytes under various pathological conditions such as post-myocardial infarction, hypertrophy, and heart failure, but relatively little is known about the mechanisms. Our previous study found that bone morphogenetic protein-4 (BMP4) was reexpressed in pathological cardiac hypertrophy models and BMP4-mediated cardiomyocyte hypertrophy. We hypothesized that BMP4 could upregulate cardiac T-type Ca(2+) channels in HL-1 atrial myocytes. The T-type Ca(2+) currents were recorded by using the patch-clamp technique, and the expressions of Cav3.1 and Cav3.2 were measured by real-time PCR method in HL-1 cells. BMP4 and Cav3.1 mRNA expressions increased in the left atrium from the pressure overload-induced hypertrophy of mice hearts. BMP4 treatment for 48 h induced increase of Cav3.1 but not Cav3.2 mRNA expression in HL-1 cells, and the increase was inhibited by BMP4 inhibitor noggin. Acute treatment with BMP4 did not affect T-type Ca(2+) currents, but chronic treatment (48 h) significantly increased the amplitude of T-type Ca(2+) currents in HL-1 cells. Chronic treatment with BMP4 induced upregulation of NADPH oxidase-4 (NOX4), increase of reactive oxygen species (ROS) level, and activation of mitogen-activated protein kinase (MAPK)-activated protein kinases c-jun N-terminal kinases (JNK) and p38. BMP4-induced upregulation of Cav3.1 mRNA was inhibited by NADPH oxidase inhibitor apocynin, the radical scavenger tempol, JNK inhibitor SP600125, and p38 inhibitor SB203580. In conclusion, BMP4 induces upregulation of Cav3.1 Ca(2+) channels and T-type Ca(2+) currents in HL-1 atrial myocytes through ROS/MAPK pathways.

Micrometastasis expressing insulin arise in lung and spleen at advanced stage of rip1-tag2 transgenic mice

Rip1-Tag2 mice is one overt pancreatic β-cell tumor model, which is widely used for studying pancreas tumor angiogenesis and tumor development. However, tumor metastasis in Rip1-Tag2 mice had rarely been reported, in this present study, we find some micrometastasis in lung and spleen of the Rip1-Tag2 mice at advanced stage, which is important for uncovering metastasis cell characteristics and exploring how to survive in cancer microenvironment. To study the micrometastasis of Rip1-Tag2 mice in advanced pancreatic cancer, we first observed the pathology process of β cell tumor in Rip1-Tag2 mice through HE staining, then we performed immunohistochemistry with insulin antibody, T-antigen antibodies and C-petide antibody on lung and spleen tissues sections from advanced stage, comparing with background wild-type C57BL/6 mice sections. The results indicated that micrometastasis expressing insulin was found in the Rip1-Tag2 mice lung, and spleen. Further evidences demonstrate pathology structure of lung and spleen are damaged. Interestingly and importantly, the expression of T antigen and insulin antibodies are all decreased in advanced stage of primary β cell tumor, which suggest that the at least partly micrometastasis is derived from the early stage or from advanced stage of β cell tumor then return to undifferentiated state like cancer stem cell. The findings contributed to the study of cancer metastasis and cancer stem cell.

Functional annotation of conserved hypothetical proteins from Haemophilus influenzae Rd KW20

Haemophilus influenzae is a Gram negative bacterium that belongs to the family Pasteurellaceae, causes bacteremia, pneumonia and acute bacterial meningitis in infants. The emergence of multi-drug resistance H. influenzae strain in clinical isolates demands the development of better/new drugs against this pathogen. Our study combines a number of bioinformatics tools for function predictions of previously not assigned proteins in the genome of H. influenzae. This genome was extensively analyzed and found 1,657 functional proteins in which function of 429 proteins are unknown, termed as hypothetical proteins (HPs). Amino acid sequences of all 429 HPs were extensively annotated and we successfully assigned the function to 296 HPs with high confidence. We also characterized the function of 124 HPs precisely, but with less confidence. We believed that sequence of a protein can be used as a framework to explain known functional properties. Here we have combined the latest versions of protein family databases, protein motifs, intrinsic features from the amino acid sequence, pathway and genome context methods to assign a precise function to hypothetical proteins for which no experimental information is available. We found these HPs belong to various classes of proteins such as enzymes, transporters, carriers, receptors, signal transducers, binding proteins, virulence and other proteins. The outcome of this work will be helpful for a better understanding of the mechanism of pathogenesis and in finding novel therapeutic targets for H. influenzae.

The many faces of calmodulin in cell proliferation, programmed cell death, autophagy, and cancer

Calmodulin (CaM) is a ubiquitous Ca(2+) receptor protein mediating a large number of signaling processes in all eukaryotic cells. CaM plays a central role in regulating a myriad of cellular functions via interaction with multiple target proteins. This review focuses on the action of CaM and CaM-dependent signaling systems in the control of vertebrate cell proliferation, programmed cell death and autophagy. The significance of CaM and interconnected CaM-regulated systems for the physiology of cancer cells including tumor stem cells, and processes required for tumor progression such as growth, tumor-associated angiogenesis and metastasis are highlighted. Furthermore, the potential targeting of CaM-dependent signaling processes for therapeutic use is discussed.

3-Methyladenine induces cell death and its interaction with chemotherapeutic drugs is independent of autophagy

3-Methyladenine (3-MA) is an autophagy inhibitor and has been widely used as a pharmacological tool in the autophagy studies. 3-MA potentiates the chemotherapeutic effects of anticancer drugs, but it is not clear whether the potentiating effects of 3-MA on chemotherapy efficacy comes from the autophagy inhibition or not. The aim of the present work is to identify the relationship between the effects of 3-MA on chemotherapy and the 3-MA-induced autophagy inhibition. The autophagy responses were evaluated by measuring LC3-II level. Cell viability, cell death and cell apoptosis were evaluated by MTT, live and dead assay kit and Tunel staining. Results showed that 3-MA dose-dependently reduced Hela cell viability but did not affect the basal autophagy responses. 3-MA at the concentration that inhibits autophagy induced Hela cell death and apoptosis. 3-MA did not inhibit the increased autophagy responses induced by chemotherapeutic drugs cispcis-diamminedichloroplatinum(II) (CDDP), tamoxifen and 5-fluorouracil (5-FU) in Hela and MCF-7 cells. The synergism or antagonism between 3-MA and chemotherapeutic drugs was dependent on the inhibition ratio of tumor cells. In conclusion, 3-MA itself induces cell death and apoptosis without relationship with autophagy; 3-MA does not inhibit the increased autophagy induced by anti-cancer drugs; the interaction between 3-MA and chemotherapeutic drugs is not related to autophagy.

AGEs induce cell death via oxidative and endoplasmic reticulum stresses in both human SH-SY5Y neuroblastoma cells and rat cortical neurons

Advanced glycation endproducts (AGEs) are elevated in aging and neurodegenerative diseases such as Alzheimer's disease (AD), and they can stimulate the generation of reactive oxygen species (ROSs) via NADPH oxidase, induce oxidative stress that lead to cell death. In the current study, we investigated the molecular events underlying the process that AGEs induce cell death in SH-SY5Y cells and rat cortical neurons. We found: (1) AGEs increase intracellular ROSs; (2) AGEs cause cell death after ROSs increase; (3) oxidative stress-induced cell death is inhibited via the blockage of AGEs receptor (RAGE), the down-regulation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, and the increase of scavenging by anti-oxidant alpha-lipoic acid (ALA); (4) endoplasmic reticulum (ER) stress was triggered by AGE-induced oxidative stress, resulting in the activation of C/EBP homologous protein (CHOP) and caspase-12 that consequently initiates cell death, taurine-conjugated ursodeoxycholic acid (TUDCA) inhibited AGE-induced ER stress and cell death. Blocking RAGE-NADPH oxidase, and RAGE-NADPH oxidase-ROSs and ER stress scavenging pathways could efficiently prevent the oxidative and ER stresses, and consequently inhibited cell death. Our results suggest a new prevention and or therapeutic approach in AGE-induced cell death.

Arsenic trioxide-induced hERG K(+) channel deficiency can be rescued by matrine and oxymatrine through up-regulating transcription factor Sp1 expression

The human ether-a-go-go-related gene (hERG) encodes the rapidly activating, delayed rectifier potassium channel (IKr) important for cardiac repolarization. Dysfunction of the hERG channel can cause Long QT Syndrome (LQTS). A wide variety of structurally diverse therapeutic compounds reduce the hERG current by acute direct inhibition of the hERG current or/and selective disruption of hERG protein expression. Arsenic trioxide (As(2)O(3)), which is used to treat acute promyelocytic leukemia, can cause LQTS type 2 (LQT2) by reducing the hERG current through the diversion of hERG trafficking to the cytoplasmic membrane. This cardiotoxicity limits its clinical applications. Our aim was to develop cardioprotective agents to decrease As(2)O(3)-induced cardiotoxicity. We reported that superfusion of hERG-expressing HEK293 (hERG-HEK) cells with matrine (1, 10 μM) increased the hERG current by promoting hERG channel activation. Long-term treatment with 1 μM matrine or oxymatrine increased expression of the hERG protein and rescued the hERG surface expression disrupted by As(2)O(3). In addition, Matrine and oxymatrine significantly shortened action potential duration prolonged by As(2)O(3) in guinea pig ventricular myocytes. These results were ascribed to the up-regulation of hERG at both mRNA and protein levels via an increase in the expression of transcription factor Sp1, an established transactivator of the hERG gene. Therefore, matrine and oxymatrine may have the potential to cure LQT2 as a potassium channel activator by promoting hERG channel activation and increasing hERG channel expression.