Biochimica et Biophysica Acta (BBA) - Molecular Cell Research

Sugar-induced cell death (SICD) remains an intriguing but poorly studied phenomenon in the physiology of Saccharomyces cerevisiae. Recently, it was shown that SICD development largely depends on the redirection of glucose fluxes between glycolysis and the pentose phosphate pathway (PPP). In particular, inhibition of glycolysis by iodoacetamide (IAA) was observed to reduce SICD levels. This study is devoted to further investigation of the relationship between SICD and the functionality of the two PPP branches. It was shown that deletion of the ZWF1 gene does not affect the decrease in SICD levels in IAA-treated cells. This allows us to conclude that the oxidative branch of the PPP is not involved in the suppression of SICD/ROS. Deletion of the GLR1 gene and attenuation of the TRR1 gene also did not restore SICD levels in cells after IAA treatment. The obtained results indicate that the level of reduced glutathione or thioredoxin does not affect SICD genesis. The addition of 5 mM ribose-5-phosphate (R5P) to the incubation medium led to suppression of SICD by 79%. At the same time, the addition of 5 mM ribose + 5 mM Pi suppressed SICD by only 20%. Suppression of SICD by 5 mM R5P in the{Delta} pho3 strain (83%) excludes the mechanism of extracellular dephosphorylation of R5P to ribose, its subsequent transport into the cell, and re-phosphorylation inside the cell. Furthermore, more than 70% suppression of SICD in the{Delta} end3 strain with 5 mM R5P excludes endocytosis as a mechanism of R5P import into the cell. The observed effect of R5P can be explained by the moonlighting function of some unknown protein. Thus, SICD development in S. cerevisiae cells depends on the final product of the non-oxidative PPP--R5P.

The ubiquitin conjugating enzyme UBE2J1/Ubc6e localizes to the endoplasmic reticulum where it mediates the ubiquitination and proteasomal degradation of terminally misfolded proteins. Although the protein is known to undergo phosphorylation at serine S184, we have considered modification at an additional site and used a bespoke anti-phospho antibody to confirm phosphorylation also at serine residue S266. Despite the well-described role of UBE2J1 in ER associated degradation (ERAD), we found no evidence for regulation at S266 during Unfolded Protein Response (UPR) induction by thapsigargin. Instead, our studies suggest that phosphorylation occurs independently at the S184 and S266 sites, with mutation at one site failing to disrupt basal phosphorylation at the second. We identified several contexts in which these two phosphorylations were differentially regulated. For example, ER localization, which is important for phosphorylation at S184, was not required for modification at S266, and sensitivity to proteasome inhibitors, which is regarded as a distinguishing feature of the S184 phospho-variant, was unaltered by the S266A mutation. Regarding regulation at S266 on the other hand, we found that pharmacological activation of protein kinase A resulted in rapid phosphorylation, with differential use of phospho-specific antibodies confirming that phosphorylation at S184 was unchanged by this treatment. Hormonal stimulation by glucagon resulted in a similar pattern of UBE2J1 phosphorylation, which occurred exclusively at S266 and could be inhibited by H89. The differential regulation demonstrated in these studies extends our understanding of the UBE2J1 enzyme, and may indicate a role in the integration of energy metabolism with environmental stress conditions.

Mitochondrial pyruvate carrier (MPC) inhibition was found protective in models of neurodegenerative diseases, such as Alzheimers and Parkinsons. However, little is known about MPC as a potential therapeutic target in Huntingtons disease (HD), a neurodegenerative disorder with dysregulation of the pro-survival pathway integrated stress response (ISR). Here, we investigate if MPC inhibition modulates the ISR and mitigates mutant huntingtin (mut-Htt) proteotoxicity in a cellular HD model. We treated cells expressing N-terminal fragments of wild-type- (wt-) or mut-Htt with two MPC inhibitors (mitoglitazone and UK5099) or solvent control. Metabolism was assessed analysing resazurin reduction, oxygen consumption, extracellular acidification, and ATP levels. ISR activation and huntingtin proteostasis were assessed using western-blot and filter-trap assays. Mut-Htt-expressing cells showed decreased resazurin reduction and ATP levels, and increased eIF2 phosphorylation, indicating metabolic stress and ISR activation. MPC inhibitors (100 {micro}M) increased resazurin reduction and decreased respiration. The latter was rescued by the membrane-permeant methyl pyruvate, which bypasses MPC inhibition. In wt-Htt-expressing cells, MPC inhibitors increased levels of ATP and ISR markers, suggesting metabolic adaptation and ISR activation. In mut-Htt-expressing cells, MPC inhibitors preserved ATP levels and attenuated mut-Htt-induced eIF2 phosphorylation but without changing soluble or aggregated mut-Htt levels. This work showed that MPC inhibition differentially modulates the ISR: it activates ISR in control cells and attenuates overactive ISR in mut-Htt-expressing cells. However, MPC inhibition did not impact the proteostasis of N-terminal fragment mut-Htt. Further studies are essential to explore MPC inhibition in less severe full-length mut-Htt-expressing models to better understand its therapeutic potential in HD.

In yeast, transcriptional adaptor 2 (ADA2; SAGA complex subunit ADA2), a member of histone acetyltransferase (HAT) complex, regulates transcription through cell signalling, but its precise role in cellular metabolism remains unclear. In this study, genetic loss of ADA2 (ada2{Delta}) induces squalene (SQ) accumulation, indicating aberrant triterpene metabolism, coupled with endoplasmic reticulum (ER)/nuclear ER (nER) expansion. Lipid analyses of ada2{Delta} revealed elevated phosphatidic acid (PA) and phosphatidylcholine (PC) levels, indicating disrupted phospholipid metabolism. The expanded ER causes basal autophagy elevation, cellular recycling, and nER phagy, suggesting a regulatory role for ADA2 in autophagy. Downregulation of phosphatidate cytidylyltransferase (CDS1) and inositol-3-phosphate synthase (INO1), coupled with elevated PA and PC in ada2{Delta}, points to a significant disruption in cytidine-diphosphate-diacylglycerol and phosphatidylinositol pathway. Overexpression of CDS1 or INO1, or the inositol supplementation, in ada2{Delta} restores SQ, basal autophagy and ER phagy. The observed target of rapamycin Ser/Thr kinase complex (TORC1) activity in ada2{Delta} is due to the high PA content. Rapamycin-mediated inhibition of TORC1 reduced SQ, PA and ER expansion while increasing lipid droplets. In contrast, a rapamycin-treated ada2{Delta}pah1{Delta} strain retained high PA, SQ and ER expansion, underscoring the functional role of TORC1-nuclear envelope morphology protein 1 (Nem1)/sporulation-specific protein SPO7 (Spo7)-Pah1 axis. Notably, SQ levels remained unchanged in a rapamycin-treated ada2{Delta}atg39{Delta} strain, suggesting that loss of nER-phagy receptor, Atg39, impairs the effectiveness of TORC1 inhibition. In conclusion, our data unveiled a critical role for Ada2 in maintaining the intricate relationship between lipid and triterpene/sterol metabolism and connecting autophagy and ER homeostasis.

The association between higher levels of physical activity and lower cancer risk and mortality is well established. However, a causal link is yet to be proven. Recent studies showed a decrease in the proliferation rates of cultured human cancer cells when the human serum employed to stimulate them was conditioned by acute exercise. Here, we tested the hypothesis that serum mediates some of the putative benefits of exercise on cancer through alterations to the growth pattern and susceptibility to chemotherapy agents of cancer cells. To this end, human non-small cell lung cancer (NSCLC) cells were exposed to serum from two cohorts that differed significantly on their levels of physical activity and, accordingly, cardiorespiratory fitness, but were otherwise identical (master athletes and non-exercisers), collected before and after an acute exercise intervention. Serum levels of glucose, lipids, albumin, C-reactive protein and cytokines were determined and the impact of the serum responses to acute and lifelong exercise on the above-mentioned parameters were analyzed. We found that acute exercise decreased the cells proliferation rate, yet shortened the cells lag phase after detachment, whereas lifelong exercise had the opposite effects. Significantly, we showed, for the first time, that lifelong exercise increased susceptibility to a chemotherapy agent (cisplatin), which may contribute to the decreased cancer mortality rates found among those who exercise regularly. Similar to the cellular effects, changes to serum cytokine levels - several of them linked to the senescence-associated secretory phenotype - depended on whether serum was conditioned by acute or by chronic exercise. Key pointsChronic exercise increased the in vitro susceptibility of lung cancer cells to cisplatin. Acute and chronic exercise modulated the in vitro tumorigenic potential of lung cancer cells. Effects were mediated by serological changes produced by exercise. Acute and chronic exercise had distinct impacts on serological cytokine levels.

The Ube2J1 enzyme that mediates the ubiquitination and proteasomal degradation of misfolded proteins at the ER is phosphorylated at serine S184. Following anisomycin treatment of HEK293T cells, we observed an inverse relationship between phosphorylation and dephosphorylation at this site. This suggested a dynamic interchange between the two forms, and we show that S184 is a target for protein phosphatase 2A. The S184-phosphorylated protein is known to exhibit increased sensitivity to proteasomal degradation, and we found that mutation at K186R increased the ratio of S184-phosphorylated to S184-dephosphorylated protein. Although the K186R mutant retained some sensitivity to proteasomal inhibition, our results show that Ube2J1 steady state expression can be exercised at multiple levels, and can involve dynamic phosphorylation and dephosphorylation at S184.

Exposure to cigarette smoke is one of the major risk factors for developing various diseases such as chronic obstructive pulmonary disease (COPD), cardiovascular disorders, and cancer mediated via cellular oxidative stress and organelle dysfunction. To this end, the current study investigated how cigarette smoke extract (CSE) affects vacuole structure and function in Saccharomyces cerevisiae, as vacuole plays a crucial role in handling oxidative stress-induced misfolded proteins. Our results showed that CSE exposure causes transient vacuolar fragmentation up to 1 h to increase its surface area to facilitate microautophagy in clearing CSE-mediated misfolded protein and promoting cell survival. However, excessive fragmentation or vacuolar fusion sensitizes cells towards CSE-mediated cellular toxicity. Towards understanding the underlying mechanism, the current study demonstrated the involvement of PI3P and PI (3,5) P2-mediated signaling and phospholipase-driven remodeling of lipid moieties. Moreover, the current study also showed the importance of mitochondrial activity in CSE-mediated vacuolar fragmentation. Prolonged exposure to CSE impairs mitochondrial function and thus disrupts fragmentation, the adaptive survival strategy against CS. It results in proteostasis collapse, which is a characteristic shared by many inflammatory and degenerative disorders. Taken together, the current study reveals a previously unrecognized cellular protection mechanism induced by cigarette smoke and highlights potential therapeutic targets for mitigating CS-mediated diseases

Autophagy contributes to normal cells physiology and is essential for progression of malignant tumors. While autophagy is mostly considered as a self-degradative and self-renewal process, it has non-degradative functions whose contribution to tumor progression is poorly explored. Here we use the autophagy dependent Drosophila RasV12, Scrib-/- carcinoma model to examine whether perturbation of distinct steps of autophagy differentially influences tumor progression. We found that inhibition of autophagosome formation, by mutating Atg13 or Atg6 either in the tumor or in the whole animal significantly decreased tumor growth. In contrast, blocking the later autophagosome-lysosome fusion (by loss of Vps39 or Syx17) and thereby autolysosomal degradation, does not reduce tumor size. We observed that an early (Atg13), but not a late (Vps39 or Syx17) block in autophagy showed reduced activity of JAK/STAT signaling, known to be critical for the progression of this tumor type. Importantly, we demonstrated that both Atg13 and Vps39 deficient tumors accumulated Stat92E inhibitor Su(var)2-10/dPIAS, a recently identified autophagic cargo, however in Vps39 mutants Su(var)2-10 is sequestered into autophagosomes. Finally, we found that reduction of Su(var)2-10 partially restores JAK/STAT signaling and rescues the growth of Atg13-deficient tumors, indicating its sequestration is a crucial mechanism to promote tumor progression.

Lipopolysaccharide (LPS), a ubiquitous bacterial component of food, is neutralized by a variety of mechanisms that help to establish a threshold, which when exceeded results in an inflammatory TLR4 mediated response. Notably both CEACAM1 and CD36 affect downstream signaling of TLR4 to LPS. Furthermore, CEACAM1 associates with CD36 in hepatocytes, regulating lipid storage and bile acid (BA) secretion that includes reverse transport of LPS to the intestine. Direct binding of LPS-Ra micelles to soluble CEACAM1 or soluble CD36 was analyzed by surface plasmon resonance (SPR), size exclusion chromatography (SEC) and transmission electron microscopy (TEM). Direct binding of CEACAM1 to CD36 was analyzed by SPR and proximity ligation assays. Molecular models were generated by Alpha Fold and Molecular Dynamics. LPS Binding: SPR binding constants of KD= 1.04 x 10-10 M and KD= 3.38 x 10-10 M were obtained for LPS-Ra micelle binding to sCEACAM1 and sCD36, respectively. On SEC, the molecular sizes of LPS-Ra micelles bound to sCEACAM1 and sCD36 were approximately 500 and 800 kDa, respectively. In addition, LPS binding to both was reduced by sodium cholate and sodium deoxycholate. Alpha Fold predicted a binding site of LPS-Ra to CD36, while Molecular Dynamic studies of an N-domain mutant of CEACAM1, that breaks a conserved salt bridge, revealed the presence of an open form that is predicted to bind LPS. sCEACAM1 to sCD36 Binding: A KD of 5.28 x 10-8 M was obtained for sCEACAM1 binding to immobilized sCD36 by SPR. Antibody-based-proximity ligation demonstrated the association of the ectodomains of CEACAM1 and CD36 on hepatic cells and when co-expressed in HEK cells. In addition, biotin-based proximity ligation demonstrated association of the cytoplasmic domains of CEACAM1 and a CD36-BioID2 fusion protein when co-expressed in HEK cells. Alpha Fold predicted both head-to-head (trans) and side-to-side (cis) binding of the N-domain of CEACAM1 to CD36, from which a membrane model of their cis-interaction could account for the proximity ligation results. Both CEACAM1 and CD36 share a common LPS micelle binding function, as well as binding to each other, and together, may regulate uptake and excretion of micellar LPS.

Ageing is considered as a process were molecular, cellular and tissular function is impaired. One classic cellular phenotype that increases during ageing is cellular senescence. Upon senescence, the cells stop proliferating and release a variety of cytokines, chemokines and extracellular vesicles. However, the implication of biomolecules derived from lipids such as resolvins are not well characterised in senescence and ageing. Here, we find that the resolvin E and D biosynthesis pathway is activated as observed by an increase in their corresponding receptors and enzymes implicated. Furthermore, knockdown of the resolvins E and D receptors impairs the induction of senescence. This pathway is conserved not only during senescence but also in fibroblasts derived from aged human individuals, aged mice and during other inflammatory responses. A metabolomics analyses shows an increase in different precursors of resolvins in senescence. In accordance with prior data, we find that small extracellular vesicles (sEV) isolated from young human donors ameliorate inflammation and the biogenesis of resolvins both in different cell models and in aged mice. In summary, here we present data showing that the resolvins biogenesis pathway is induced in ageing and cellular senescence.

Zinc is essential for life, and its regulation is tightly controlled by numerous transporters. As we age, our micronutrient levels, intake, and absorption change. Additionally, senescent cells increase with age and can contribute to the progression of age-related diseases. The study of Zn homeostasis in senescent intestinal cells is a relatively unexplored area that we aimed to investigate. Using two models to induce senescence in intestinal epithelial cells--etoposide treatment and {gamma}-irradiation--we observed that Zn levels increased in the cells, likely due to the upregulation of Zn transporters ZIP4 and ZnT7. This upregulated Zn seems to accumulate in the Golgi apparatus, and when Zn accumulation is blocked through chelation, a rescue effect occurs, marked by a decrease in senescence markers. This research emphasizes the role of Zn in senescent cells and its possible involvement in the development of senescence and the disrupted Zn homeostasis seen with aging.

Genetic inhibition of cyclophilin D (CypD) delays the opening of the mitochondrial permeability transition pore (MPTP) and therefore reduces necrotic cell death. Elucidation of factors that impact CypD activity is therefore key to understanding the regulation of MPTP opening. Glycogen synthase kinase-3{beta} (GSK3{beta}) is a serine/threonine kinase that has been shown to modulate MPTP and cell death, potentially through phosphorylation of CypD. Therefore, we hypothesized that the mitochondrial fraction of GSK3{beta} directly phosphorylates CypD and promotes opening of MPTP. Overexpression of full length GSK3{beta} in mouse embryonic fibroblasts sensitized the MPTP and exacerbated oxidative stress-induced necrosis. In contrast, genetic inhibition of GSK3{beta} protected against oxidant-induced cytotoxicity but did not affect the MPTP. Recombinant GSK3{beta} could directly bind to and phosphorylate recombinant CypD. Mass spectrometry revealed several putative GSK3{beta} phosphorylation sites on CypD. However, mutation of these sites did not affect the peptidyl prolyl isomerase activity of CypD and reconstitution of these phosphomutants in CypD-deficient cells increased MPTP sensitivity and oxidative-induced cell death to the same extent as wild-type CypD. Further, targeted overexpression of either wild-type or kinase-inactive GSK3{beta} in the mitochondrial matrix did not impact MPTP or cell death. Moreover, while proteinase-K digestion of cardiac mitochondria showed a significant amount of GSK3{beta} in the mitochondria, it was not localized to the matrix. Finally, overexpression of GSK3{beta} was still able to increase MPTP sensitivity and oxidative stress-induced death in CypD-null cells. Taken together, these data indicate that, while GSK3{beta} can modulate MPTP, this appears to be independent of GSK3{beta}s interaction with, or phosphorylation of CypD.

Zinc is an essential transition metal that participates in many biological processes. In C. elegans, excess zinc is stored in lysosomes in intestinal cells; this process involves increasing the expression of the zinc transporter CDF-2 and remodeling of lysosomes characterized by an increase in the volume of the expansion compartment. To determine if this is a more general property, we investigated other metals. Here we report that lysosomes are remodeled in response to excess copper, manganese, and cadmium, with each metal causing an increase in the volume of the expansion compartment. Mutants with a reduced number of lysosomes were hypersensitive to growth retardation caused by excess copper and manganese, suggesting metal toxicity is prevented by metal sequestration in lysosomes. Using a novel method to analyze isolated lysosomes by X-ray Fluorescence Microscopy we demonstrated that zinc, copper and manganese are detectable in the lumen of lysosomes. To further analyze copper, we examined localization of CUA-1.1, a copper transporter that moves copper into the lumen of lysosomes. Like the zinc transporter CDF-2, CUA-1.1 localizes to both the acidified and expansion compartments in excess copper. These results indicate that the same intestinal lysosomes store zinc, copper and manganese. Lysosome remodeling characterized by an increase in volume of the expansion compartment is not specific to zinc but is a more general phenomenon during metal storage in lysosomes.

The MYC associated factor X (MAX) is the heterodimeric partner of the MYC paralogs (MYC, MYCN and MYCL). When deregulated, high level of the MYC paralogs contribute to all aspects of tumorigenesis and tumor growth. MAX can also heterodimerize with the MXD proteins, MNT and MGA. Heterodimerization and sequence specific DNA binding to the E-Box sequences at gene promoters is controlled by their heterodimerization with the MAX b-HLH-LZ. As a heterodimer with MAX, MYC proteins activate genes involved in cell metabolism, growth and proliferation whereas MXD proteins, MNT and MGA repress them. MAX can also bind to the E-Bos sequence as a homodimer. Being devoid of a transactivation domain it can act as an antagonist of the MYC/MAX heterodimers. Variants of MAX have been reported to be linked to cancer. These variants are either not expressed, inactivated or lead to missense mutations. This has led to the notion that MAX may have a tumor suppressor role. Here, we characterize three of those variants with missense mutations in the basic region, i.e. E32K, R35P and R35C. We analyzed their heterodimerization with the b-HLH-LZ of MYC and their DNA binding properties as homo-and heterodimers. The R35C variant b-HLH-LZ was found to have a markedly increased affinity for the b-HLH-LZ of MYC. We also observed that all three b-HLH-LZ variants have a lower affinity as homodimers for the E-Box than the WT. This was shown to lead to a preferential binding of all the heterodimeric b-LHLH-LZ to the E-Box. This effect is exacerbated in the case of the R35C variant. We argue that this preferential binding of MYC as heterodimers with these variants to E-Box sequences could contribute to tumorigenesis. Hence, our results suggest that, mechanistically, the MAX homodimer bound to the E-Box could act as a tumor suppressor. MATERIALS AND METHODSO_ST_ABSMolecular modelingC_ST_ABSThe open source version 1.7.6.0 of Pymol was used for modeling and molecular rendering [1]. The crystal structure of the MAX homodimer bound to the E-Box (1HLO [2]) was used as a template for the generation of the models. The variants were generated using the mutagenesis function in the wizard. The conformation of the K32 side chain was manually set in order to avoid introducing steric clashes with DNA. Protein expression and purificationThe cDNA, coding for the MAX b-HLH-LZ (Max* hereafter, residues 22-103, UniProt entry P61244-1) to which are added the GSGC residues in c-terminal, inserted in the pET3a vector was already available in the laboratory [3] and was used as a template to generate the plasmids with inserts coding for each of the mutants (E32K, R35C and R35P) through quick-change PCR with Q5 DNA polymerase and DpnI from New England Biolabs. The primers used were purchased from IDT DNA, their sequences are listed in Table S1. Sequence for each construct was confirmed by Sanger sequencing at the Plateforme de sequencage SANGER - Centre de recherche du CHU de Quebec - Universite Laval. The primary structure for the basic region of each construct is given in Fig. 2A. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=137 SRC="FIGDIR/small/715400v1_fig2.gif" ALT="Figure 2"> View larger version (41K): org.highwire.dtl.DTLVardef@1b05d5eorg.highwire.dtl.DTLVardef@1c1d692org.highwire.dtl.DTLVardef@ee469dorg.highwire.dtl.DTLVardef@15e0ba4_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 2.C_FLOATNO Structure schematics, specific and non-specific interactions dictating specificity and stability of binding of the basic region of MAX to the canonical (CACGTG) E-Box. A. Primary structure for the basic region of MAX and each of the variants. Positions making the most important contacts with the E-box are indicated by black arrows. Positions for the variants studied here are colored according to the Zappo colour scheme, following their physico-chemical properties: red for negative, blue for positive, magenta for proline and yellow for cysteine. B. The side chain (carboxylate) of E32 receives H-Bonds from the CA nucleobases in the leading strand (white carbon atoms). R35 and R36 make a salt bridges with phosphate groups while and the guanidino moiety of R36 makes a specific H-Bond with the nucleobase of the G in the strand of the reverse complement (cyan carbon atoms). C. The R35C mutation removes one non-specific salt-bridge at the interface of the complex. D. The aliphatic portion of the K side chain in the E32K variant is unable to accept the H-Bonds from the CA nucleobases and leads to the stabilisation of the complex and the helical structure of the basic region. E. In addition to removing a salt-bride, the Pro residue in the R35P kinks the path of the basic region, prevents the establishment of the specific H-Bonds mandatory for recognition of the E-Box and leads to unfolding of the helical state. C_FIG The MYC b-HLH-LZ (Myc*), the Max*WT b-HLH-LZ and its variants were expressed and purified as previously described [3,4] After lyophilisation, the b-HLH-LZs were kept at -20{degrees}C and solubilised in Myc buffer (50 mM NaCl, 50 mM NaH2PO4 pH 5.5) for Myc* or PBS for Max* at a final concentration of 1 mM before use. Circular dichroismAll circular dichroism (CD) measurements were performed on a Jasco J-810 spectropolarimeter equipped with a Peltier-type thermostat. The instrument was routinely calibrated using an aqueous solution of d-10-(+)-camphorsulfonic acid at 290.5 nm. Samples were prepared as follows: Max* (either WT or a variant) was diluted in 100 {micro}l 2X CD buffer (40 mM KCl, 11.4 mM K2HPO4, 28.6 mM KH2PO4, pH 6.8) and the volume adjusted to 106 {micro}l with PBS. 10 {micro}l TCEP 16 mM were added, and the volume further adjusted to 192 {micro}l with ddH2O before samples were incubated overnight at room temperature. After reduction, Myc* was added and the volume adjusted to 198 {micro}l with Myc buffer (Na2HPO4 0.95 mM, NaH2PO4 49.05 mM, 50 mM NaCl, pH 5.5). The DNA complexes were prepared as follows. After a 10 minutes incubation of the protein samples at room temperature, 0, 1 or 2 {micro}l of 2 mM of specific or non-specific DNA duplexes in 10 mM Tris pH 8.0 were added and the volume adjusted to 200 {micro}l with 10 mM Tris pH 8.0. The strands of the specific probe were: 5-ATT ACC CAC GTG TCC T*AC-3 and 5-GTA GGA CAC GTG GGT* AAT-3 (with the E-box sequence underlined) and the non-specific probe: 5-ATT ACC TCC GGA TCC T*AC-3 and 5-GTA GGA TCC GGA GGT* AAT-3 (Integrated DNA Technologies). Samples were further incubated for 10 minutes at room temperature and transferred to a 1 mm path length quartz cuvette. All spectra were recorded from 250 to 195 nm at 0.1 nm intervals by accumulating 10 spectra at 25 {degrees}C. Thermal denaturations were recorded at 222 nm from 5 to 95 {degrees}C at a heating rate of 1 {degrees}C/min. CD signal for spectra and thermal denaturations was corrected by substracting the signal from corresponding spectra or thermal denaturation either for buffer alone or the appropriate DNA duplex. CD signal was then converted to mean residue ellipticity using the following formula [5]: [{theta}] = {delta} {middle dot} MRW/(10{middle dot}c l) where [{theta}] is the mean residue ellipticity in deg {middle dot} cm2 dmol-1, {delta} is the CD signal in millidegrees, MRW is the mean residue weight, c is the concentration in mg/ml and l is the pathlength in mm. For the heterodimers, the concentration used was the sum of Max* and Myc* and the MRW was determined using a weighted average.

Synthetic 6-Br-Q0C10 has been shown to exhibit a partial electron transfer activity of native coenzyme Q in the isolated mitochondria. It reduces energy coupling efficiency by approximately 30%, suggesting that it may be useful in modulating cell growth in tissue culture. Whether or not it behaves in the same way in the whole cells, or animal, however, has not yet been fully examined. Recently we have investigated the effect of 6-Br-Q0C10 across multiple cell lines using three detection methods. Treatment with 6-Br-Q0C10 reduces cell proliferation in all cell lines tested, with different effectiveness. Obesity-related cell lines were the most susceptible, and a pronounced inhibitory effect was also observed in cancer cell lines. These results strengthen the idea of using 6-Br-Q0C10 to manage obesity or to retard the growth of rate cancer cells and thus prolonging life.

Brain metastases are a common and often fatal complication of certain cancer types, such as triple-negative breast cancer. However, the molecular pathways driving brain metastasis formation, including the migration of cancer cells from the bloodstream to the brain parenchyma across the blood-brain barrier, are not yet fully defined. Therefore, using highly relevant mouse and human model systems, the mechanisms by which triple-negative breast cancer cells and their released extracellular vesicles modulate the blood-brain barrier-forming endothelium to increase its permissiveness to tumour cell entry into the brain are investigated. It is observed that extracellular vesicles derived from tumour cells are taken up by cerebral endothelial cells, where they induce miR-146a-5p- and TGF-{beta}1-mediated downregulation of PAQR5/mPR{gamma}, a membrane progesterone receptor. This, in turn, leads to disruption of interendothelial tight junctions, particularly through repression of claudin-5 expression, a critical protein for maintaining barrier function. Altogether this identifies a novel mechanism by which triple-negative breast cancer-derived extracellular vesicles compromise blood-brain barrier integrity, thereby facilitating transendothelial migration of cancer cells and promoting brain metastasis development. Moreover, this study is the first to highlight the role of membrane progesterone receptors in regulating the blood-brain barrier. Table of contents O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=136 SRC="FIGDIR/small/701753v2_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@15252aeorg.highwire.dtl.DTLVardef@1b23beforg.highwire.dtl.DTLVardef@7cd517org.highwire.dtl.DTLVardef@189db4e_HPS_FORMAT_FIGEXP M_FIG Extracellular vesicles from triple-negative breast cancer cells induce miR-146a-5p- and TGF-1-mediated downregulation of PAQR5/mPR{gamma}, a membrane progesterone receptor, in blood-brain barrier-forming endothelial cells. This results in disruption of interendothelial tight junctions, thereby promoting enhanced migration of cancer cells into the brain. This mechanism highlights the role of membrane progesterone receptors in regulating the blood-brain barrier. C_FIG

Colorectal cancer is the third most common cancer across the world. Acquired resistance to therapeutics is one of the major challenges in cancer cure. With the development of resistance to organometallic drugs there was switch for the usage of inhibitors of kinases which play a crucial role in cellular activities. Regorafenib is a multi-kinase inhibitor used as an oral anti-cancer drug for treating advanced colorectal cancer (CRC). With increasing reports of acquired resistance to regorafenib in long-term use it is inevitable to understand the mechanisms underlying in the development of resistance. To understand the molecular mechanism of acquired drug resistance towards regorafenib we have developed a regorafenib resistant HCT116 cell line (Reg-R-HCT116) and an integrated quantitative proteomic and phospho-proteomics approach is used to elucidate the molecular signaling mechanisms that help in drug tolerance. Proteome and Phosphoproteome analysis revealed an extensive remodelling of signaling pathways associated with metabolism, protein synthesis and stress adaptations. This also revealed a large set of phosphorylated proteins as well as proteins that might be associated with aberrant activation or differential alteration of PI3K-AKT-mTOR, EIF2, HIF-1, Apoptosis inhibition, Glucose metabolism, amino acid metabolism and DNA-repair-associated signaling. Differential phosphorylation of downstream molecules of the mentioned pathways NDRG1, ACINUS and RICTOR and enhanced cell survival further confirmed their role in drug tolerance. Targeted inhibition of both the mTOR complexes using Torin1 resensitized the cells to regorafenib. Combination treatment of regorafenib with torin1 showed a synergistic cytotoxicity and attenuated the expression of key survival proteins. These findings provide mechanistic insight into acquired resistance to regorafenib in colorectal cancer and identified mTOR/eIF2 signaling as one of the critical drivers of resistance phenotype. The results suggest combinatorial targeting of these pathways could be an effective strategy to overcome regorafenib resistance and improve clinical outcomes in CRC.

Proteostasis is the balance of protein synthesis, protein maintenance and protein degradation. Proteostasis is disturbed in neurodegenerative disorders like Alzheimers disease (AD) of the aging human body. Protein synthesis by the ribosome is the most error-prone process in gene expression. If and how the error-rate of protein synthesis is regulated during human aging and contributes to AD is unknown. Here we show that ribosomal error-rate is adapted in cellular models of human aging, but not in mouse aging. This adaptation involves ER-stress signaling and the Alzheimers disease-related proteins amyloid-beta precursor protein and presenilin 1. Our results suggest that ribosomal error-rate is a relevant parameter in human aging and disease.

Altered iron homeostasis has long been implicated in Parkinson's Disease (PD), although the mechanisms have not been clear. Given the critical role of PD-related activating mutations in LRRK2 (leucine-rich repeat protein kinase 2) within membrane trafficking pathways we examined the impact of a homozygous mutant LRRK2G2019S on iron homeostasis within the RAW macrophage cell line with high iron capacity. Proteomics analysis revealed a dysregulation of iron-related proteins in steady state with highly elevated levels of ferritin light chain and a reduction of ferritin heavy chain. LRRK2G2019S mutant cells showed efficient ferritinophagy upon iron chelation, but upon iron overload there was a near complete block in the degradation of the ferritinophagy adaptor NCOA4. These conditions lead to an accumulation of phosphorylated Rab8 at the plasma membrane, which is selectively inhibited by LRRK type II kinase inhibitors. Iron overload then leads to increased oxidative stress and ferroptotic cell death. These data implicate LRRK2 as a key regulator of iron homeostasis and point to the need for an increased focus on the mechanisms of iron dysregulation in PD.

The enzyme nitric oxide synthase (NOS) breaks down the semi-essential amino acid L-arginine (L-Arg) in the cell to produce citrulline and nitric oxide (NO). NO is a crucial signalling molecule in cells that controls the metabolism of fats and carbohydrates. The aim of this study was to investigate two important genes in the L-Arg-NOS-NO signalling pathway, AMPK and ACC-1, as markers of the molecular mechanisms that are triggered when liver cells sense elevated L-Arg. Mouse liver epithelial insulin-sensitive BNL CL2 cells were used as a model system and cultured with 0, 400 or 800 {micro}M L-Arg. Cell growth parameters were analysed alongside qRT-PCR based analysis of target transcripts involved in lipid and glucose metabolic pathways. In a further experiment, NOS inhibitor; L-NAME (40 mM) and external NO donor; SNAP (100 {micro}M) were added and the effect on target gene expression analysed. L-Arg addition impacted culture viability and cell growth. AMP-activated protein kinase (AMPK) was regulated in response to L-Arg addition with increasing extracellular concentrations elevating AMPK mRNA and protein expressions. L-NAME decreased target gene expression in an L-Arg addition dependent manner. SNAP (100 {micro}M) addition increased target gene expression after 6 and 24 h. NO, produced as a result of L-Arg addition and the factors L-NAME and SNAP, that regulate NO bioavailability, impacted BNL CL2 cell NO/AMPK/ACC-1 signalling pathways via regulating mRNA expression and subsequently protein expression.