Examination of Hypoxanthine Guanine Phosphoribosyltransferase as a biomarker for colorectal cancer patients

The aim of this study is to investigate these enzymes as possible biomarkers in two colorectal cancer cell lines: HT29, SW480, SW620, and Colo205. With 1,168,929 individuals currently diagnosed with colorectal cancer in the United States, there remains a need to find biomarkers to improve diagnosis and expand treatment options for patients. Due to their role in proliferation and cell cycle regulation, we hypothesized an increase in salvage pathway enzyme (APRT, DCK, and HPRT) expression and possible presentation within colon cancer cells. Enzyme surface localization was assessed utilizing confocal microscopy, flow cytometry, and scanning electron microscopy. General protein expression was evaluated utilizing immunohistochemistry and Western blot analysis. While we found no statistically significant presence of either APRT or DCK on the membranes of SW620, Colo205, and HT29 cells, but found significant expression of HPRT on the surface of HT29, SW480, and SW620 cells. The average population fluorescence increased by 28%, 58%, and 40% in HT29, SW620, and SW480 cells, respectively, when compared to isotype controls. Confocal microscopy images revealed direct overlap between SW620 cells stained with a membrane dye and anti-HPRT antibody, indicating co-localization on the plasma membrane. In addition, cells treated with gold labelled HPRT antibody experienced significant changes in gold weight percentage on both SW620 and HT29 cells when compared to isotype controls. When evaluating expression within normal tissue, there was insignificant levels of HPRT binding. These data collectively suggest that HPRT may be a possible biomarker target for the identification and treatment of colorectal cancer.

Biogenic Polyphosphate Nanoparticles from Synechococcus sp. PCC 7002 Exhibit Intestinal Protective Potential in Human Intestinal Epithelial Cells In Vitro and Murine Small Intestine Ex Vivo

Polyphosphates are one of the active compounds from probiotics to maintain gut health. The current research extracted and purified intact biogenic polyphosphate nanoparticles (BPNPs) from Synechococcus sp. PCC 7002 cells. BPNPs were near-spherical anionic particles (56.9 ± 15.1 nm) mainly composed of calcium and magnesium salt of polyphosphate and were colloidally stable at near-neutral and alkaline pH. BPNPs survived gastrointestinal digestion in mice and could be absorbed and transported by polarized Caco-2 cell monolayers. They dose-dependently increased the tightness of intercellular tight junction and the expression of claudin-4, occludin, zonula occludens-1, and heat shock protein 27 in Caco-2 cell monolayers. BPNPs also effectively attenuated H₂O₂-induced cell death, plasma membrane impairment, and intracellular superoxide production in NCM460 cells. In addition, they conferred resistance to H₂O₂-induced barrier disruption in freshly excised mouse small intestine. Our results suggest that BPNPs are a promising postbiotic nanomaterial with potential applications in gut health maintenance.

Design Strategy of Multi-electron Transfer Catalysts Based on a Bioinformatic Analysis of Oxygen Evolution and Reduction Enzymes

Understanding the design strategy of photosynthetic and respiratory enzymes is important to develop efficient artificial catalysts for oxygen evolution and reduction reactions. Here, based on a bioinformatic analysis of cyanobacterial oxygen evolution and reduction enzymes (photosystem II: PS II and cytochrome c oxidase: COX, respectively), the gene encoding the catalytic D1 subunit of PS II was found to be expressed individually across 38 phylogenetically diverse strains, which is in contrast to the operon structure of the genes encoding major COX subunits. Selective synthesis of the D1 subunit minimizes the repair cost of PS II, which allows compensation for its instability by lowering the turnover number required to generate a net positive energy yield. The different bioenergetics observed between PS II and COX suggest that in addition to the catalytic activity rationalized by the Sabatier principle, stability factors have also provided a major influence on the design strategy of biological multi-electron transfer enzymes.

Mismatch tolerance during homologous recombination in mammalian cells

We investigated the homology dependency of recombination in thymidine kinase (tk)-deficient mouse fibroblasts. Cells were transfected with DNA constructs harboring a herpes tk gene (the "recipient") rendered non-functional by an oligonucleotide containing the recognition site for endonuclease I-SceI. Constructs also contained a "donor" tk sequence that could restore function to the recipient gene through spontaneous gene conversion or via repair of a double-strand break (DSB) at the I-SceI site. Recombination events were recoverable by selection for tk-positive clones. Three different donors were used containing 16, 25, or 33 mismatches relative to the recipient. The mismatches were clustered, forming an interval of "homeology" relative to the recipient sequences. We show that when homeologous sequences were surrounded by high homology, mismatches were frequently included in gene conversion events. Notably, conversion tracts from spontaneous recombination included either all or none of the mismatches, suggesting that recombination must begin and end in high homology. This requirement was relaxed for events that occurred near an induced DSB, as a significant number of these latter conversion tracts had one end positioned within homeology. Knock-down of mismatch repair showed that incorporation of mismatches into gene conversion tracts can involve repair of mismatched heteroduplex intermediates, indicating that mismatch repair does not necessarily impede homeologous genetic exchange. Our results illustrate (1) genetic exchange between homeologous sequences in a mammalian genome is enabled by nearby homology, (2) proximity to a DSB impacts the homology requirements for where genetic exchange may begin and end, and (3) mismatch correction and previously documented anti-recombination activity are separable functions of the mismatch repair machinery in mammalian cells.

SCFSNIPER4 controls the turnover of two redundant TRAF proteins in plant immunity

In mammals, tumor necrosis factor receptor associated factors (TRAFs) are signaling adaptors that regulate diverse physiological processes, including immunity and stress responses. In Arabidopsis, MUSE13 and MUSE14 are redundant TRAF proteins serving as adaptors in the SCF^CRP1 complex to facilitate the turnover of nucleotide-binding domain and leucine-rich repeats (NLR) immune receptors. Degradation of MUSE13 is inhibited by proteasome inhibitor, suggesting that the MUSE13 stability is controlled by the 26S proteasome. However, the E3 ligase that regulates MUSE13 level is unknown. Here we report the identification of an F-box protein, SNIPER4 that regulates the turnover of MUSE13 and MUSE14. Protein levels of MUSE13 and MUSE14 are reduced by SNIPER4 overexpression, while higher accumulation of MUSE13 and MUSE14 is observed when dominant-negative SNIPER4 is expressed. Furthermore, SNIPER4 associates with MUSE13 or MUSE14. Taken together, the SCF^SNIPER4 complex controls the turnover of TRAF proteins for an optimum immune output.

Involvement of Kif4a in Spindle Formation and Chromosome Segregation in Mouse Oocytes

Kif4a, a member of the kinesin superfamily, has been reported to participate in a series of cellular processes such as chromosome condensation and cytokinesis during mitosis. However, the roles of KIF4a in meiosis are still unknown. In present study we found that the Kif4a protein expression decreased in maternal aged mouse oocytes. We then explored the roles of Kif4a in mouse oocyte meiosis by knockdown analysis. Kif4a was enriched at the spindle during mouse oocyte maturation. By specific knock down of the Kif4a using morpholino microinjection, we found that the disruption of Kif4a caused the failure of polar body extrusion. Further analysis indicated that Kif4a might affect the spindle morphology and chromosome alignment in the mouse oocytes, and this might be due to the regulation of tubulin acetylation. Moreover, our results showed that an increased proportion of aneuploidy in the Kif4a knock down oocytes, and this might be due to the loss of kinetochore-microtubule attachment. Taken together, these results suggested that Kif4a possibly regulated mouse oocyte meiosis through its effects on the spindle organization and accurate chromosome segregation, and the loss of Kif4a might be related with aneuploidy of aging oocytes.

Endoplasmic reticulum stress in ischemic and nephrotoxic acute kidney injury

Acute kidney injury (AKI) is a medical condition characterized by kidney damage with a rapid decline of renal function, which is associated with high mortality and morbidity. Recent research has further established an intimate relationship between AKI and chronic kidney disease. Perturbations of kidney cells in AKI result in the accumulation of unfolded and misfolded proteins in the endoplasmic reticulum (ER), leading to unfolded protein response (UPR) or ER stress. In this review, we analyze the role and regulation of ER stress in AKI triggered by renal ischemia-reperfusion and cisplatin nephrotoxicity. The balance between the two major components of UPR, the adaptive pathway and the apoptotic pathway, plays a critical role in determining the cell fate in ER stress. The adaptive pathway is evoked to attenuate translation, induce chaperones, maintain protein homeostasis and promote cell survival. Prolonged ER stress activates the apoptotic pathway, resulting in the elimination of dysfunctional cells. Therefore, regulating ER stress in kidney cells may provide a therapeutic target in AKI. KEY MESSAGES Perturbations of kidney cells in acute kidney injury result in the accumulation of unfolded and misfolded proteins in ER, leading to unfolded protein response (UPR) or ER stress. The balance between the adaptive pathway and the apoptotic pathway of UPR plays a critical role in determining the cell fate in ER stress. Modulation of ER stress in kidney cells may provide a therapeutic strategy for acute kidney injury.

Consensus guidelines for the use and interpretation of angiogenesis assays

The formation of new blood vessels, or angiogenesis, is a complex process that plays important roles in growth and development, tissue and organ regeneration, as well as numerous pathological conditions. Angiogenesis undergoes multiple discrete steps that can be individually evaluated and quantified by a large number of bioassays. These independent assessments hold advantages but also have limitations. This article describes in vivo, ex vivo, and in vitro bioassays that are available for the evaluation of angiogenesis and highlights critical aspects that are relevant for their execution and proper interpretation. As such, this collaborative work is the first edition of consensus guidelines on angiogenesis bioassays to serve for current and future reference.

Isotopic Evidence for Disrupted Copper Metabolism in Amyotrophic Lateral Sclerosis

Redox-active metals are thought to be implicated in neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). To address this point, we measured the concentrations of 12 elements and, for the first time, the stable isotope compositions of copper (redox-active) and zinc (redox-inactive) in human cerebrospinal fluids of 31 patients with ALS, 11 age-matched controls (CTRL), and 14 patients with Alzheimer disease. We first show that metal concentrations weakly discriminate patients with ALS from the two other groups. We then report that zinc isotopic compositions are similar in the three groups, but that patients with ALS have significantly 65copper-enriched isotopic compositions relative to CTRL and patients with AD. This result unambiguously demonstrates that copper is implicated in ALS. We suggest that this copper isotopic signature may result from abnormal protein aggregation in the brain parenchyma, and propose that isotopic analysis is a potential tool that may help unraveling the molecular mechanisms at work in ALS.

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Redox-active metals are implicated in ALS through oxidative stress

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Concentrations of these metals in CSFs of patients with ALS are non-specific

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Copper stable isotope composition in CSFs of patients with ALS are specific

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Isotopic balance between CSFs and brain is probably the mechanism

FusC, a member of the M16 protease family acquired by bacteria for iron piracy against plants

Iron is essential for life. Accessing iron from the environment can be a limiting factor that determines success in a given environmental niche. For bacteria, access of chelated iron from the environment is often mediated by TonB-dependent transporters (TBDTs), which are β-barrel proteins that form sophisticated channels in the outer membrane. Reports of iron-bearing proteins being used as a source of iron indicate specific protein import reactions across the bacterial outer membrane. The molecular mechanism by which a folded protein can be imported in this way had remained mysterious, as did the evolutionary process that could lead to such a protein import pathway. How does the bacterium evolve the specificity factors that would be required to select and import a protein encoded on another organism's genome? We describe here a model whereby the plant iron-bearing protein ferredoxin can be imported across the outer membrane of the plant pathogen Pectobacterium by means of a Brownian ratchet mechanism, thereby liberating iron into the bacterium to enable its growth in plant tissues. This import pathway is facilitated by FusC, a member of the same protein family as the mitochondrial processing peptidase (MPP). The Brownian ratchet depends on binding sites discovered in crystal structures of FusC that engage a linear segment of the plant protein ferredoxin. Sequence relationships suggest that the bacterial gene encoding FusC has previously unappreciated homologues in plants and that the protein import mechanism employed by the bacterium is an evolutionary echo of the protein import pathway in plant mitochondria and plastids.

A novel EXT2 mutation in a consanguineous family with severe developmental delay, microcephaly, seizures, feeding difficulties, and osteopenia extends the phenotypic spectrum of autosomal recessive EXT2-related syndrome (AREXT2)

We report a consanguineous family where 2 boys presented with developmental delay, hypotonia, microcephaly, seizures, gastro-intestinal abnormalities, osteopenia, and neurological regression. Whole exome sequencing performed in one of the boys revealed the presence of a novel homozygous missense variant in the EXT2 gene: c.11C > T (p.Ser4Leu). Segregation analysis by Sanger sequencing confirmed homozygous by descent autosomal recessive transmission of this mutation. Another family was previously reported with homozygous mutations in this gene in four siblings affected with a nearly similar clinical condition (Farhan et al., 2015). We discuss the similarities and differences between the two syndromes and propose AREXT2 as a new acronym for EXT2-related diseases.

Ric-8A, a GEF for heterotrimeric G-proteins, controls cranial neural crest cell polarity during migration

The neural crest (NC) is a transient embryonic cell population that migrates extensively during development. Ric-8A, a guanine nucleotide exchange factor (GEF) for different Gα subunits regulates cranial NC (CNC) cell migration in Xenopus through a mechanism that still remains to be elucidated. To properly migrate, CNC cells establish an axis of polarization and undergo morphological changes to generate protrusions at the leading edge and retraction of the cell rear. Here, we aim to study the role of Ric-8A in cell polarity during CNC cell migration by examining whether its signaling affects the localization of GTPase activity in Xenopus CNC using GTPase-based probes in live cells and aPKC and Par3 as polarity markers. We show that the levels of Ric-8A are critical during migration and affect the localization of polarity markers and the subcellular localization of GTPase activity, suggesting that Ric-8A, probably through heterotrimeric G-protein signaling, regulates cell polarity during CNC migration.

Key Residues for the Formation of Aβ42 Amyloid Fibrils

Formation of amyloid fibrils by Aβ42 protein is a pathological hallmark of Alzheimer's disease. Aβ42 fibrillization is a nucleation-dependent polymerization process, in which nucleation is the rate-limiting step. Structural knowledge of the fibril nucleus is important to understand the molecular mechanism of Aβ aggregation and is also critical for successful modulation of the fibrillization process. Here, we used a scanning mutagenesis approach to study the role of each residue position in Aβ42 fibrillization kinetics. The side chain we used to replace the native residue is a nitroxide spin label called R1, which was introduced using site-directed spin labeling. In this systematic study, all residue positions of Aβ42 sequence were studied, and we identified six key residues for the Aβ42 fibril formation: H14, E22, D23, G33, G37, and G38. Our results suggest that charges at positions 22 and 23 and backbone flexibilities at positions 33, 37, and 38 play key roles in Aβ42 fibrillization kinetics. Our results also suggest that the formation of a β-strand at residues 15-21 is an important feature in Aβ42 fibril nucleus. In overall evaluation of all of the mutational effects on fibrillization kinetics, we found that the thioflavin T fluorescence at the aggregation plateau is a poor indicator of aggregation rates.

Telomerase Reverse Transcriptase Contains a BH3-Like Motif and Interacts with BCL-2 Family Members

Upregulation of human telomerase reverse transcriptase (hTERT) expression is an important factor in the cellular survival and cancer. Although growing evidence suggests that hTERT inhibits cellular apoptosis by telomere-independent functions, the mechanisms involved are not fully understood. Here, we show that hTERT contains a BH3-like motif, a short peptide sequence found in BCL-2 family proteins, and interacts with anti-apoptotic BCL-2 family proteins MCL-1 and BCL-xL, suggesting a functional link between hTERT and the mitochondrial pathway of apoptosis. Additionally, we propose that hTERT can be categorized into the atypical BH3-only proteins that promote cellular survival, possibly due to the non-canonical interaction between hTERT and antiapoptotic proteins. Although the detailed mechanisms underlying the hTERT BH3-like motif functions and interactions between hTERT and BCL-2 family proteins have not been elucidated, this work proposes a possible connection between hTERT and BCL-2 family members and reconsiders the role of the BH3-like motif as an interaction motif.

Sesquiterpene lactone from Artemisia argyi induces gastric carcinoma cell apoptosis via activating NADPH oxidase/reactive oxygen species/mitochondrial pathway

Apoptosis is an essential type of programmed cell death. Previous studies have demonstrated that a wide range of natural-derived anticancer agents induce apoptosis by trigging oxidative stress. Artemisia argyi is a traditional Chinese herb for treating diverse diseases including dyspepsia, arthroncus, and anaphylactic disease. In this study, sesquiterpene lactone 3 (SL3), a bioactive ingredient isolated from Artemisia argyi was found to show obvious inhibitory effect on two gastric carcinoma cells. Mechanism study revealed that SL3 promoted the membrane translocation of p47, activated nicotinamide adenine dinucleotide (NADPH) oxidase, and evaluated intracellular reactive oxygen species production, leading to the activation of mitochondria-dependent caspase apoptosis pathway. Collectively, these findings show that SL3 is a promising anticancer candidate against gastric carcinoma by activating NADPH oxidase/reactive oxygen species/mitochondrial pathway.

Circulating low density lipoprotein (LDL)

Low-density lipoprotein (LDL) particles are known as atherogenic agents in coronary artery diseases. They modify to other electronegative forms and may be the subject for improvement of inflammatory events in vessel subendothelial spaces. The circulating LDL value is associated with the plasma PCSK-9 level. They internalize into macrophages using the lysosomal receptor-mediated pathways. LDL uptake is related to the membrane scavenger receptors, modifications of lipid and protein components of LDL particles, vesicular maturation and lipid stores of cells. Furthermore, LDL vesicular trafficking is involved with the function of some proteins such as Rab and Lamp families. These proteins also help in the transportation of free cholesterol from lysosome into the cytosol. The aggregation of lipids in the cytosol is a starting point for the formation of foam cells so that they may participate in the primary core of atherosclerosis plaques. The effects of macrophage subclasses are different in the formation and remodeling of plaques. This review is focused on the cellular and molecular events involved in cholesterol homeostasis.

Epigenetics in ovarian cancer: premise, properties, and perspectives

Malignant ovarian tumors bear the highest mortality rate among all gynecological cancers. Both late tumor diagnosis and tolerance to available chemical therapy increase patient mortality. Therefore, it is both urgent and important to identify biomarkers facilitating early identification and novel agents preventing recurrence. Accumulating evidence demonstrates that epigenetic aberrations (particularly histone modifications) are crucial in tumor initiation and development. Histone acetylation and methylation are respectively regulated by acetyltransferases-deacetylases and methyltransferases-demethylases, both of which are implicated in ovarian cancer pathogenesis. In this review, we summarize the most recent discoveries pertaining to ovarian cancer development arising from the imbalance of histone acetylation and methylation, and provide insight into novel therapeutic interventions for the treatment of ovarian carcinoma.

"Do We Know Jack" About JAK? A Closer Look at JAK/STAT Signaling Pathway

Janus tyrosine kinase (JAK) family of proteins have been identified as crucial proteins in signal transduction initiated by a wide range of membrane receptors. Among the proteins in this family JAK2 has been associated with important downstream proteins, including signal transducers and activators of transcription (STATs), which in turn regulate the expression of a variety of proteins involved in induction or prevention of apoptosis. Therefore, the JAK/STAT signaling axis plays a major role in the proliferation and survival of different cancer cells, and may even be involved in resistance mechanisms against molecularly targeted drugs. Despite extensive research focused on the protein structure and mechanisms of activation of JAKs, and signal transduction through these proteins, their importance in cancer initiation and progression seem to be underestimated. This manuscript is an attempt to highlight the role of JAK proteins in cancer biology, the most recent developments in targeting JAKs, and the central role they play in intracellular cross-talks with other signaling cascades.

A polymyxin B-silver nanoparticle colloidal system and the application of lipopolysaccharide analysis

Polymyxin B (PMB) is a small cyclic polycationic lipopeptide, which can be used as an antibiotic drug against Gram-negative bacteria. In this work, the interaction between citrate capped silver nanoparticles (AgNPs) and PMB is studied. Experimental results show that the association constant is extremely high and the binding event leads to a significant variation in the localized surface plasmon resonance (LSPR) of AgNPs. Moreover, the PMB-AgNP colloidal system can be further exploited as a sensitive analytical platform. Taking lipopolysaccharide (LPS) as an example, we demonstrate a facile colorimetric LPS detection method. LPS is a major constituent of the Gram-negative bacterial cell wall which is used as an optimal biomarker for some diseases like urinary tract infections and sepsis. In this study, target LPS is able to tightly bind to PMB, which effectively inhibits the PMB induced aggregation of AgNPs. By monitoring the UV-vis absorption spectra, the LPS concentration can be quantitatively determined with high sensitivity. The sensing strategy is quite simple, which allows effortless diagnosis of many diseases at different stages.

Crystal structure and pH-dependent allosteric regulation of human β-ureidopropionase, an enzyme involved in anticancer drug metabolism

β-Ureidopropionase (βUP) catalyzes the third step of the reductive pyrimidine catabolic pathway responsible for breakdown of uracil-, thymine- and pyrimidine-based antimetabolites such as 5-fluorouracil. Nitrilase-like βUPs use a tetrad of conserved residues (Cys233, Lys196, Glu119 and Glu207) for catalysis and occur in a variety of oligomeric states. Positive co-operativity toward the substrate N-carbamoyl-β-alanine and an oligomerization-dependent mechanism of substrate activation and product inhibition have been reported for the enzymes from some species but not others. Here, the activity of recombinant human βUP is shown to be similarly regulated by substrate and product, but in a pH-dependent manner. Existing as a homodimer at pH 9, the enzyme increasingly associates to form octamers and larger oligomers with decreasing pH. Only at physiological pH is the enzyme responsive to effector binding, with N-carbamoyl-β-alanine causing association to more active higher molecular mass species, and β-alanine dissociation to inactive dimers. The parallel between the pH and ligand-induced effects suggests that protonation state changes play a crucial role in the allosteric regulation mechanism. Disruption of dimer-dimer interfaces by site-directed mutagenesis generated dimeric, inactive enzyme variants. The crystal structure of the T299C variant refined to 2.08 Å resolution revealed high structural conservation between human and fruit fly βUP, and supports the hypothesis that enzyme activation by oligomer assembly involves ordering of loop regions forming the entrance to the active site at the dimer-dimer interface, effectively positioning the catalytically important Glu207 in the active site.

Sublethal Photodynamic Treatment Does Not Lead to Development of Resistance

A promising new alternative approach for eradication of antibiotic-resistant strains is to expose microbes to photosensitizers, which upon illumination generate reactive oxygen species. Among the requirements for a potent, medically applicable photosensitizer, are high efficacy in killing microbes and low toxicity to the host. Since photodynamic treatment is based on production of reactive species which are potentially DNA damaging and mutagenic, it might be expected that under selective pressure, microbes would develop resistance. The aim of this study was to determine if antibacterial photodynamic treatment with a highly photoefficient photosensitizer, Zn(II) meso-tetrakis(N-n-hexylpyridinium-2-yl)porphyrin would lead to development of resistance. To answer that question, bacterial cultures were subjected to multiple cycles of sublethal photodynamic stress and regrowth, and to continuous growth under photodynamic exposure. Antibiotic-resistant Staphylococcus aureus and Escherichia coli clinical isolates were also tested for susceptibility to photodynamic inactivation and for development of resistance. Results demonstrated that multiple photodynamic exposures and regrowth of surviving cells or continuous growth under sublethal photodynamic conditions, did not lead to development of resistance to photosensitizers or to antibiotics. Antibiotic-resistant E. coli and S. aureus were as sensitive to photodynamic killing as were their antibiotic-sensitive counterparts and no changes in their sensitivity to antibiotics or to photodynamic inactivation after multiple cycles of photodynamic treatment and regrowth were observed. In conclusion, photosensitizers with high photodynamic antimicrobial efficiency can be used successfully for eradication of antibiotic-resistant bacterial strains without causing development of resistance.

Ratiometric Raman imaging reveals the new anti-cancer potential of lipid targeting drugs

De novo lipid synthesis is upregulated in cancer cells and inhibiting these pathways has displayed anti-tumour activity. Here we use Raman spectroscopy, focusing solely on high wavenumber spectra, to detect changes in lipid composition in single cells in response to drugs targeting de novo lipid synthesis. Unexpectedly, the beta-blocker propranolol showed selectively towards cancerous PC3 compared to non-cancerous PNT2 prostate cells, demonstrating the potential of this approach to identify new anti-cancer drug leads. A unique and simple ratiometric approach for intracellular lipid investigation is reported using statistical analysis to create phenotypic 'barcodes', a globally applicable strategy for Raman drug-cell studies. High wavenumber spectral analysis is compatible with low cost glass substrates, easily translatable into the cytological work stream. The analytical strength of this technique could have a significant impact on cancer treatment through vastly improved understanding of cancer cell metabolism, and thus guide drug design and enhance personalised medicine strategies.

Porcine Reproductive and Respiratory Syndrome Virus Infection Induces both eIF2α Phosphorylation-Dependent and -Independent Host Translation Shutoff

Porcine reproductive and respiratory syndrome virus (PRRSV) is an Arterivirus that has caused tremendous economic losses in the global swine industry since it was discovered in the late 1980s. Inducing host translation shutoff is a strategy used by many viruses to optimize their replication and spread. Here, we demonstrate that PRRSV infection causes host translation suppression, which is strongly dependent on viral replication. By screening PRRSV-encoded nonstructural proteins (nsps), we found that nsp2 participates in the induction of host translation shutoff and that its transmembrane (TM) domain is required for this process. nsp2-induced translation suppression is independent of protein degradation pathways and the phosphorylation of eukaryotic initiation factor 2α (eIF2α). However, the overexpression of nsp2 or its TM domain significantly attenuated the mammalian target of rapamycin (mTOR) signaling pathway, an alternative pathway for modulating host gene expression. PRRSV infection also attenuated the mTOR signaling pathway, and PRRSV-induced host translation shutoff could be partly reversed when the attenuated mTOR phosphorylation was reactivated by an activator of the mTOR pathway. PRRSV infection still negatively regulated the host translation when the effects of eIF2α phosphorylation were completely reversed. Taken together, our results demonstrate that PRRSV infection induces host translation shutoff and that nsp2 is associated with this process. Both eIF2α phosphorylation and the attenuation of the mTOR signaling pathway contribute to PRRSV-induced host translation arrest.IMPORTANCE Viruses are obligate parasites, and the production of progeny viruses relies strictly on the host translation machinery. Therefore, the efficient modulation of host mRNA translation benefits viral replication, spread, and evolution. In this study, we provide evidence that porcine reproductive and respiratory syndrome virus (PRRSV) infection induces host translation shutoff and that the viral nonstructural protein nsp2 is associated with this process. Many viruses induce host translation shutoff by phosphorylating eukaryotic initiation factor 2α (eIF2α). However, PRRSV nsp2 does not induce eIF2α phosphorylation but attenuates the mTOR signaling pathway, another pathway regulating the host cell translational machinery. We also found that PRRSV-induced host translation shutoff was partly reversed by eliminating the effects of eIF2α phosphorylation or reactivating the mTOR pathway, indicating that PRRSV infection induces both eIF2α phosphorylation-dependent and -independent host translation shutoff.

Genetic Analysis of Signal Generation by the Rgt2 Glucose Sensor of Saccharomyces cerevisiae

The yeast S. cerevisiae senses glucose through Snf3 and Rgt2, transmembrane proteins that generate an intracellular signal in response to glucose that leads to inhibition of the Rgt1 transcriptional repressor and consequently to derepression of HXT genes encoding glucose transporters. Snf3 and Rgt2 are thought to be glucose receptors because they are similar to glucose transporters. In contrast to glucose transporters, they have unusually long C-terminal tails that bind to Mth1 and Std1, paralogous proteins that regulate function of the Rgt1 transcription factor. We show that the C-terminal tail of Rgt2 is not responsible for its inability to transport glucose. To gain insight into how the glucose sensors generate an intracellular signal, we identified RGT2 mutations that cause constitutive signal generation. Most of the mutations alter evolutionarily-conserved amino acids in the transmembrane spanning regions of Rgt2 that are predicted to be involved in maintaining an outward-facing conformation or to be in the substrate binding site. Our analysis of these mutations suggests they cause Rgt2 to adopt inward-facing or occluded conformations that generate the glucose signal. These results support the idea that Rgt2 and Snf3 are glucose receptors that signal in response to binding of extracellular glucose and inform the basis of their signaling.

A small-molecule inhibitor of HIV-1 Rev function detected by a diversity screen based on RRE-Rev interference

The Rev protein of HIV-1 binds to the Rev Recognition Element (RRE) in the virus RNA to promote nuclear export of unspliced and partially spliced transcripts, an essential step in the virus transmission cycle. Here, we describe the screening of a library of chemically diverse compounds with an assay based on monitoring the interaction between the RNA-binding α-helix of Rev and its high-affinity binding site in the RRE. This screen allowed the identification of a benzofluorenone compound that inhibited the formation of the full-length RRE-Rev ribonucleoprotein by associating to the RRE, and blocked HIV-1 transcription and Rev action in cells. This molecule, previously studied as a cytostatic agent, had substantial antiretroviral activity. Together with other screening hits, it provides a new chemical scaffold for the development of antiretroviral agents based on blockage of HIV-1 RNA biogenesis.

Comparative genomic investigation of high-elevation adaptation in ectothermic snakes

Several previous genomic studies have focused on adaptation to high elevations, but these investigations have been largely limited to endotherms. Snakes of the genus Thermophis are endemic to the Tibetan plateau and therefore present an opportunity to study high-elevation adaptations in ectotherms. Here, we report the de novo assembly of the genome of a Tibetan hot-spring snake (Thermophis baileyi) and then compare its genome to the genomes of the other two species of Thermophis, as well as to the genomes of two related species of snakes that occur at lower elevations. We identify 308 putative genes that appear to be under positive selection in Thermophis We also identified genes with shared amino acid replacements in the high-elevation hot-spring snakes compared with snakes and lizards that live at low elevations, including the genes for proteins involved in DNA damage repair (FEN1) and response to hypoxia (EPAS1). Functional assays of the FEN1 alleles reveal that the Thermophis allele is more stable under UV radiation than is the ancestral allele found in low-elevation lizards and snakes. Functional assays of EPAS1 alleles suggest that the Thermophis protein has lower transactivation activity than the low-elevation forms. Our analysis identifies some convergent genetic mechanisms in high-elevation adaptation between endotherms (based on studies of mammals) and ectotherms (based on our studies of Thermophis).

Identification of a PDE4-Specific Pocket for the Design of Selective Inhibitors

Inhibitors of phosphodiesterases (PDEs) have been widely studied as therapeutics for the treatment of human diseases, but improvement of inhibitor selectivity is still desirable for the enhancement of inhibitor potency. Here, we report identification of a water-containing subpocket as a PDE4-specific pocket for inhibitor binding. We designed against the pocket and synthesized two enantiomers of PDE4 inhibitor Zl-n-91. The ( S)-Zl-n-91 enantiomer showed IC50 values of 12 and 20 nM for the catalytic domains of PDE4D2 and PDE4B2B, respectively, selectivity several thousand-fold greater than those of other PDE families, and potent neuroprotection activities. Crystal structures of the PDE4D2 catalytic domain in complex with each Zl-n-91 enantiomer revealed that ( S)-Zl-n-91 but not ( R)-Zl-n-91 formed a hydrogen bond with the bound water in the pocket, thus explaining its higher affinity. The structural superposition between the PDE families revealed that this water-containing subpocket is unique to PDE4 and thus valuable for the design of PDE4 selective inhibitors.

A specific QSAR model for proteasome inhibitors from Oleaeuropaea and Ficuscarica

Oleaeuropaea and Ficuscarica are widely used in traditional medicine for the treatment of cancer. Therefore, it is of interest to develop a QSAR model for screening proteasome inhibitors from plant source. Hence, a QSAR model was developed using multiple linear regressions; partial least squares regression and principal component regression methods. Results of QSAR modeling and docking demonstrate that compounds derived from both plants have great potentiality to be proteasome inhibitors. The developed QSAR model highlights a strong structure-effect relationship. The predicted correlation of comparative molecular field analysis, and comparative molecular similarity indexes are 0.963 and 0.919, respectively. Computed absorption, distribution, metabolism, excretion and toxicity studies on these derivatives showed encouraging results with very low toxicity, distribution and absorption.

Nanofibers as Bioinstructive Scaffolds Capable of Modulating Differentiation through Mechanosensitive Pathways for Regenerative Engineering

Bioinstructive scaffolds encode information in the physical shape and size of materials to direct cell responses. Electrospinning nanofibers is a process that offers control over scaffold architecture and fiber diameter, while providing extended linear length of fibers. This review summarizes tissue engineering literature that has utilized nanofiber scaffolds to direct stem cell differentiation for various tissues including musculoskeletal, vascular, immunological and nervous system tissues. Nanofibers are also considered for their extracellular matrix mimetic characteristics that can preserve stem cell differentiation capacity. These topics are considered in the context of focal adhesion and integrin signaling. Regenerative engineering will be enhanced by construction of scaffolds encoded with shape information to cause an attached cell to create the intended tissue at that region. Nanofibers are likely to be a bioinstructive scaffold in future regenerative engineering development as we pursue the Grand Challenges of engineering tissues.

Impact of Temperature on Heparin and Protein Interactions

Heparin has many important biological activities, associated with a diverse set of interactions with biologically functional proteins. The binding mechanisms and biological significance of heparin-protein interactions have attracted wide attention. However, the temperature sensitivity of heparin-protein interaction is relatively unstudied. The impact of temperature on the binding of heparin to three representative heparin-binding proteins, antithrombin III (AT III), fibroblast growth factor-1 (FGF1) and fibroblast growth factor-2 (FGF2) are evaluated. The affinity and kinetics of these interactions were measured at 10°C, 25°C and 30°C. The association rate, dissociation rate, binding affinity and binding mass were compared at different temperatures. In the two state binding process between AT III and heparin, temperature played a negligible role on ATIII binding to heparin (1st state reaction), but demonstrated a role in the conformational change process (2nd state reaction). In the case of FGF1 and FGF2, the kinetics and affinity, while distinctly different at the temperatures studies, were still within the same order of magnitude. Based these results, we conclude that it many cases it is possible to perform surface plasmon resonance measurements of heparin-protein interaction at different temperatures, especially at reduced (ambient or lower) temperatures, and obtain comparable binding data.

Partial Inactivation of the Chromatin Remodelers SMARCA2 and SMARCA4 in Virus-Infected Cells by Caspase-Mediated Cleavage

The BAF-chromatin remodeling complex, with its mutually exclusive ATPases SMARCA2 and SMARCA4, is essential for the transcriptional activation of numerous genes, including a subset of interferon-stimulated genes (ISGs). Here, we show that C-terminally truncated forms of both SMARCA2 and SMARCA4 accumulate in cells infected with different RNA or DNA viruses. The levels of truncated SMARCA2 or SMARCA4 strongly correlate with the degree of cell damage and death observed after virus infection. The use of a pan-caspase inhibitor and genetically modified cell lines unable to undergo apoptosis revealed that the truncated forms result from the activity of caspases downstream of the activated intrinsic apoptotic pathway. C-terminally cleaved SMARCA2 and SMARCA4 lack potential nuclear localization signals as well as the bromo- and SnAC domain, with the latter two domains believed to be essential for chromatin association and remodeling. Consistent with this belief, C-terminally truncated SMARCA2 was partially relocated to the cytoplasm. However, the remaining nuclear protein was sufficient to induce ISG expression and inhibit the replication of vesicular stomatitis virus and influenza A virus. This suggests that virus-induced apoptosis does not occur at the expense of an intact interferon-mediated antiviral response pathway.IMPORTANCE Efficient induction of interferon-stimulated genes (ISGs) prior to infection is known to effectively convert a cell into an antiviral state, blocking viral replication. Additionally, cells can undergo caspase-mediated apoptosis to control viral infection. Here, we identify SMARCA2 and SMARCA4 to be essential for the efficient induction of ISGs but also to be targeted by cellular caspases downstream of the intrinsic apoptotic pathway. We find that C-terminally cleaved SMARCA2 and SMARCA4 accumulate at late stages of infection, when cell damage already had occurred. Cleavage of the C terminus removes domains important for nuclear localization and chromatin binding of SMARCA2 and SMARCA4. Consequently, the cleaved forms are unable to efficiently accumulate in the cell nucleus. Intriguingly, the remaining nuclear C-terminally truncated SMARCA2 still induced ISG expression, although to lower levels. These data suggest that in virus-infected cells caspase-mediated cell death does not completely inactivate the SMARCA2- and SMARCA4-dependent interferon signaling pathway.

Design of Novel HIV-1/2 Fusion Inhibitors with High Therapeutic Efficacy in Rhesus Monkey Models

T-20 (enfuvirtide) is the only approved viral fusion inhibitor that is used for the treatment of human immunodeficiency virus type 1 (HIV-1) infection; however, it has relatively low antiviral activity and easily induces drug resistance. We recently reported a T-20-based lipopeptide fusion inhibitor (LP-40) showing improved anti-HIV activity (X. Ding et al., J Virol 91:e00831-17, 2017, https://doi.org/10.1128/JVI.00831-17). In this study, we designed LP-50 and LP-51 by refining the structure and function of LP-40. The two new lipopeptides showed dramatically enhanced secondary structure and binding stability and were exceptionally potent inhibitors of HIV-1, HIV-2, simian immunodeficiency virus (SIV), and chimeric simian-human immunodeficiency virus (SHIV), with mean 50% inhibitory concentrations (IC₅₀s) in the very low picomolar range. They also exhibited dramatically increased potencies in inhibiting a panel of T-20- and LP-40-resistant mutant viruses. In line with their in vitro data, LP-50 and LP-51 exhibited extremely potent and long-lasting ex vivo anti-HIV activities in rhesus monkeys: serum dilution peaks that inhibited 50% of virus infection were >15,200-fold higher than those for T-20 and LP-40. Low-dose, short-term monotherapy of LP-51 could sharply reduce viral loads to undetectable levels in acutely and chronically SHIV infected monkey models. To our knowledge, LP-50 and LP-51 are the most potent and broad HIV-1/2 and SIV fusion inhibitors, which can be developed for clinical use and can serve as tools for exploration of the mechanisms of viral entry and inhibition.IMPORTANCE T-20 remains the only membrane fusion inhibitor available for the treatment of viral infection, but its relatively low anti-HIV activity and genetic barrier for drug resistance have significantly limited its clinical application. Here we report two new lipopeptide-based fusion inhibitors (LP-50 and LP-51) showing extremely potent inhibitory activities against diverse HIV-1, HIV-2, SIV, and T-20-resistant variants. Promisingly, both inhibitors exhibited potent and long-lasting ex vivo anti-HIV activity and could efficiently suppress viral loads to undetectable levels in SHIV-infected monkey models. We believe that LP-50 and LP-51 are the most potent and broad-spectrum fusion inhibitors known to date and thus have high potential for clinical development.

Rtt105 functions as a chaperone for replication protein A to preserve genome stability

Generation of single-stranded DNA (ssDNA) is required for the template strand formation during DNA replication. Replication Protein A (RPA) is an ssDNA-binding protein essential for protecting ssDNA at replication forks in eukaryotic cells. While significant progress has been made in characterizing the role of the RPA-ssDNA complex, how RPA is loaded at replication forks remains poorly explored. Here, we show that the Saccharomyces cerevisiae protein regulator of Ty1 transposition 105 (Rtt105) binds RPA and helps load it at replication forks. Cells lacking Rtt105 exhibit a dramatic reduction in RPA loading at replication forks, compromised DNA synthesis under replication stress, and increased genome instability. Mechanistically, we show that Rtt105 mediates the RPA-importin interaction and also promotes RPA binding to ssDNA directly in vitro, but is not present in the final RPA-ssDNA complex. Single-molecule studies reveal that Rtt105 affects the binding mode of RPA to ssDNA These results support a model in which Rtt105 functions as an RPA chaperone that escorts RPA to the nucleus and facilitates its loading onto ssDNA at replication forks.

Comparative Proteomic Analysis of Coregulation of CIPK14 and WHIRLY1/3 Mediated Pale Yellowing of Leaves in Arabidopsis

Pale yellowing of leaf variegation is observed in the mutant Arabidopsis lines Calcineurin B-Like-Interacting Protein Kinase14 (CIPK14) overexpression (oeCIPK14) and double-knockout WHIRLY1/WHIRLY3 (why1/3). Further, the relative distribution of WHIRLY1 (WHY1) protein between plastids and the nucleus is affected by the phosphorylation of WHY1 by CIPK14. To elucidate the coregulation of CIPK14 and WHIRLY1/WHIRLY3-mediated pale yellowing of leaves, a differential proteomic analysis was conducted between the oeCIPK14 variegated (oeCIPK14-var) line, why1/3 variegated (why1/3-var) line, and wild type (WT). More than 800 protein spots were resolved on each gel, and 67 differentially abundant proteins (DAPs) were identified by matrix-assisted laser desorption ionization-time of flight/time of flight mass spectrometry (MALDI-TOF/TOF-MS). Of these 67 proteins, 34 DAPs were in the oeCIPK14-var line and 33 DAPs were in the why1/3-var line compared to the WT. Five overlapping proteins were differentially expressed in both the oeCIPK14-var and why1/3-var lines: ATP-dependent Clp protease proteolytic subunit-related protein 3 (ClpR3), Ribulose bisphosphate carboxylase large chain (RBCL), Beta-amylase 3 (BAM3), Ribosome-recycling factor (RRF), and Ribulose bisphosphate carboxylase small chain (RBCS). Bioinformatics analysis showed that most of the DAPs are involved in photosynthesis, defense and antioxidation pathways, protein metabolism, amino acid metabolism, energy metabolism, malate biosynthesis, lipid metabolism, and transcription. Thus, in the why1/3-var and oeCIPK14-var lines, there was a decrease in the photosystem parameters, including the content of chlorophyll, the photochemical efficiency of photosystem (PS II) (Fv/Fm), and electron transport rates (ETRs), but there was an increase in non-photochemical quenching (NPQ). Both mutants showed high sensitivity to intense light. Based on the annotation of the DAPs from both why1/3-var and oeCIPK14-var lines, we conclude that the CIPK14 phosphorylation-mediated WHY1 deficiency in plastids is related to the impairment of protein metabolism, leading to chloroplast dysfunction.

Stem cell-derived clade F AAVs mediate high-efficiency homologous recombination-based genome editing

The precise correction of genetic mutations at the nucleotide level is an attractive permanent therapeutic strategy for human disease. However, despite significant progress, challenges to efficient and accurate genome editing persist. Here, we report a genome editing platform based upon a class of hematopoietic stem cell (HSC)-derived clade F adeno-associated virus (AAV), which does not require prior nuclease-mediated DNA breaks and functions exclusively through BRCA2-dependent homologous recombination. Genome editing is guided by complementary homology arms and is highly accurate and seamless, with no evidence of on-target mutations, including insertion/deletions or inclusion of AAV inverted terminal repeats. Efficient genome editing was demonstrated at different loci within the human genome, including a safe harbor locus, AAVS1, and the therapeutically relevant IL2RG gene, and at the murine Rosa26 locus. HSC-derived AAV vector (AAVHSC)-mediated genome editing was robust in primary human cells, including CD34+ cells, adult liver, hepatic endothelial cells, and myocytes. Importantly, high-efficiency gene editing was achieved in vivo upon a single i.v. injection of AAVHSC editing vectors in mice. Thus, clade F AAV-mediated genome editing represents a promising, highly efficient, precise, single-component approach that enables the development of therapeutic in vivo genome editing for the treatment of a multitude of human gene-based diseases.

Parkinson's disease: convergence on synaptic homeostasis

Parkinson's disease, the second most common neurodegenerative disorder, affects millions of people globally. There is no cure, and its prevalence will double by 2030. In recent years, numerous causative genes and risk factors for Parkinson's disease have been identified and more than half appear to function at the synapse. Subtle synaptic defects are thought to precede blunt neuronal death, but the mechanisms that are dysfunctional at synapses are only now being unraveled. Here, we review recent work and propose a model where different Parkinson proteins interact in a cell compartment-specific manner at the synapse where these proteins regulate endocytosis and autophagy. While this field is only recently emerging, the work suggests that the loss of synaptic homeostasis may contribute to neurodegeneration and is a key player in Parkinson's disease.

The Doubletime Homolog KIN-20 Mainly Regulates let-7 Independently of Its Effects on the Period Homolog LIN-42 in Caenorhabditis elegans

The Caenorhabditis elegans (C. elegans) heterochronic pathway, which regulates developmental timing, is thought to be an ancestral form of the circadian clock in other organisms. An essential member of this clock is the Period protein whose homolog, lin-42, in C. elegans is an important heterochronic gene. LIN-42 functions as a transcriptional repressor of multiple genes including the conserved lin-4 and let-7 microRNAs. Like other Period proteins, levels of LIN-42 oscillate throughout development. In other organisms this cycling is controlled in part by phosphorylation. KIN-20 is the C. elegans homolog of the Drosophila Period protein kinase Doubletime. Worms containing a large deletion in kin-20 have a significantly smaller brood size and develop slower than wild type C. elegans Here we analyze the effect of kin-20 on lin-42 phenotypes and microRNA expression. We find that kin-20 RNAi enhances loss-of-function lin-42 mutant phenotypes and that kin-20 mutant worms express lower levels of LIN-42 We also show that kin-20 is important for post-transcriptional regulation of mature let-7 and lin-4 microRNA expression. In addition, the increased level of let-7 found in lin-42(n1089) mutant worms is not maintained after kin-20 RNAi treatment. Instead, let-7 is further repressed when levels of kin-20 and lin-42 are both decreased. Altogether these results suggest that though kin-20 regulates lin-42 and let-7 microRNA, it mainly affects let-7 microRNA expression independently of lin-42 These findings further our understanding of the mechanisms by which these conserved circadian rhythmic genes interact to ultimately regulate rhythmic processes, developmental timing and microRNA biogenesis in C. elegans.

Investigations on the mode of action of gephyronic acid, an inhibitor of eukaryotic protein translation from myxobacteria

The identification of inhibitors of eukaryotic protein biosynthesis, which are targeting single translation factors, is highly demanded. Here we report on a small molecule inhibitor, gephyronic acid, isolated from the myxobacterium Archangium gephyra that inhibits growth of transformed mammalian cell lines in the nM range. In direct comparison, primary human fibroblasts were shown to be less sensitive to toxic effects of gephyronic acid than cancer-derived cells. Gephyronic acid is targeting the protein translation system. Experiments with IRES dual luciferase reporter assays identified it as an inhibitor of the translation initiation. DARTs approaches, co-localization studies and pull-down assays indicate that the binding partner could be the eukaryotic initiation factor 2 subunit alpha (eIF2α). Gephyronic acid seems to have a different mode of action than the structurally related polyketides tedanolide, myriaporone, and pederin and is a valuable tool for investigating the eukaryotic translation system. Because cancer derived cells were found to be especially sensitive, gephyronic acid could potentially find use as a drug candidate.

New Insights Into Functions and Possible Applications of Clostridium difficile CRISPR-Cas System

Over the last decades the enteric bacterium Clostridium difficile (novel name Clostridioides difficile) - has emerged as an important human nosocomial pathogen. It is a leading cause of hospital-acquired diarrhea and represents a major challenge for healthcare providers. Many aspects of C. difficile pathogenesis and its evolution remain poorly understood. Efficient defense systems against phages and other genetic elements could have contributed to the success of this enteropathogen in the phage-rich gut communities. Recent studies demonstrated the presence of an active CRISPR (clustered regularly interspaced short palindromic repeats)-Cas (CRISPR-associated) subtype I-B system in C. difficile. In this mini-review, we will discuss the recent advances in characterization of original features of the C. difficile CRISPR-Cas system in laboratory and clinical strains, as well as interesting perspectives for our understanding of this defense system function and regulation in this important enteropathogen. This knowledge will pave the way for the development of promising biotechnological and therapeutic tools in the future. Possible applications for the C. difficile strain monitoring and genotyping, as well as for CRISPR-based genome editing and antimicrobials are also discussed.

Organ-wide profiling in mouse reveals high editing levels of Filamin B mRNA in the musculoskeletal system

Adenosine to inosine RNA editing in protein-coding messenger RNAs (mRNAs) potentially leads to changes in the amino acid composition of the encoded proteins. The mRNAs encoding the ubiquitously expressed actin-crosslinking proteins Filamin A and Filamin B undergo RNA editing leading to a highly conserved glutamine to arginine exchange at the identical position in either protein. Here, by targeted amplicon sequencing we analysed the RNA editing of Filamin B across several mouse tissues during post-natal development. We find highest filamin B editing levels in skeletal muscles, cartilage and bones, tissues where Filamin B function seems most important. Through the analysis of Filamin B editing in mice deficient in either ADAR1 or 2, we identified ADAR2 as the enzyme responsible for Filamin B RNA editing. We show that in neuronal tissues Filamin B editing drops in spliced transcripts indicating regulated maturation of edited transcripts. We show further that the variability of Filamin B editing across several organs correlates with its mRNA expression.

The Effect of Neurotoxin MPTP and Neuroprotector Isatin on the Profile of Ubiquitinated Brain Mitochondrial Proteins

Mitochondria are a crucial target for the actions of neurotoxins, causing symptoms of Parkinson's disease in various experimental animal models, and also neuroprotectors. There is evidence that mitochondrial dysfunction induced by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) influences functioning of the ubiquitin-proteasomal system (UPS) responsible for selective proteolytic degradation of proteins from various intracellular compartments (including mitochondria) and neuroprotective effects of certain anti-Parkisonian agents (monoamine oxidase inhibitors) may be associated with their effects on the UPS. In this study, we have investigated the effect of the neurotoxin MPTP and neuroprotector isatin, and their combination on the profile of ubiquitinated brain mitochondrial proteins. The development of movement disorders induced by MPTP administration caused dramatic changes in the profile of ubiquitinated proteins associated with mitochondria. Pretreatment with the neuroprotector isatin decreased manifestations of MPTP-induced Parkinsonism, and had a significant impact on the profile of ubiquitinated mitochondrial proteins (including oxidative modified proteins). Administration of isatin alone to intact mice also influenced the profile of ubiquitinated mitochondrial proteins, and increased the proportion of oxidized proteins carrying the ubiquitination signature. These alterations in the ubiquitination of mitochondrial proteins observed within 2 h after administration of MPTP and isatin obviously reflect immediate short-term biological responses to these treatments.

Coumarin-based Fluorescent Probes for Selectively Targeting and Imaging the Endoplasmic Reticulum in Mammalian Cells

Developing improved fluorescent probes for imaging the endoplasmic reticulum (ER) is necessary for structure-activity studies of this dynamic organelle. Two coumarin-based compounds with sulfonamide side groups were synthesized and characterized as ER-targeting probes. Their selectivity to target the ER in HeLa and GM07373 mammalian cells was shown with co-localization experiments using commercially available probes that localize in the ER, mitochondria, or lysozymes. The hydrophobicity of the coumarin-based probes was comparable to known probes that partition into the ER membrane. Their cytotoxicity in mammalian cells was low with IC50 values that range from 205 to 252 μm. The fluorescent quantum yields of the coumarin-based probes when excited with 400 nm light were 0.60, and they have a much narrower emission spectrum (from 435 to 525 nm in methanol) than that of the only commercially available ER probe that is exited with 400 nm light (ER-Tracker™ Blue-White DPX). Thus, the coumarin-based probes are more useful for multicolor imaging with yellow and red emitting fluorophores. In addition to the above benefits, ER labeling was achieved with the coumarin-based probes in both live cells and fixed cells, revealing their versatility for a wide range of cellular imaging applications.