Bile acids have been shown to be important regulatory molecules for cells in the liver and gastrointestinal tract. They can activate various cell signaling pathways including the extracellular regulated kinase (ERK)1/2 and AKT as well as the G-protein coupled receptor (GPCR), TGR5/M-BAR. Activation of the ERK1/2 and AKT signaling pathways by conjugated bile acids has been reported to be pertussis toxin (PTX) and dominant negative Gαi sensitive in primary rodent hepatocytes. However, the GPCRs responsible for activation of these pathways have not been identified. Screening GPCRs in the lipid activated phylogenetic family, expressed in HEK293 cells, identified sphingosine 1-phosphate receptor 2 (S1P2) as being activated by taurocholate (TCA). TCA, taurodeoxycholic acid (TDCA), tauroursodeoxycholic acid (TUDCA), glycocholic acid (GCA), glycodeoxycholic acid (GDCA), and S1P-induced activation of ERK1/2 and AKT were significantly inhibited by JTE-013, a S1P2 antagonist, in primary rat hepatocytes. JTE-013 significantly inhibited hepatic ERK1/2 and AKT activation as well as short heterodimeric partner (SHP) mRNA induction by TCA in the chronic bile fistula rat. Knock down of the expression of S1P2 by a recombinant lentivirus encoding S1P2 shRNA, markedly inhibited the activation of ERK1/2 and AKT by TCA and S1P in rat primary hepatocytes. Primary hepatocytes prepared from S1P2 knock out (S1P2−/−) mice were significantly blunted in the activation of the ERK1/2 and AKT pathways by TCA. Structural modeling of the S1P receptors indicated that only S1P2 can accommodate TCA binding. In summary, all these data support the hypothesis that conjugated bile acids activate the ERK1/2 and AKT signaling pathways primarily via S1P2 in primary rodent hepatocytes.

We have analyzed the specific interaction of murine p53 with the consensus DNA-binding sequence 5-AGACATGCCT-AGACATGCCT-3. We used segments of p53 lacking the C-terminal, nonspecific DNA-binding domain because the presence of an autonomous nonspecific DNA-binding domain in wild-type p53 would complicate analysis of site-specific DNA binding. p53 amino acids 1 to 360 bind the consensus sequence as tetramers, and DNA binding promotes tetramer-tetramer interactions. p53 amino acids 80 to 290, lacking both the nonspecific DNA-binding and tetramerization domains, consistently bind consensus DNA as four monomers and only as four monomers. The virtual absence of stable binding by fewer than four monomers, even at low concentrations of p53, argues that binding by amino acids 80 to 290 is strongly cooperative. Because p53 tetramers and monomers do not simultaneously bind a single DNA consensus sequence, we conclude that a single tetramer of wild-type p53 engages the recognition sequences of the entire DNA consensus site. We further show that consensus DNA consists of two functional half-sites. Insertions, deletions, or rearrangements within the half-sites reduce DNA binding dramatically. In contrast, two half-sites separated by insertions bind p53 relatively efficiently. Insertions that place half-sites on opposite faces of the DNA helix reduce DNA binding more than insertions that place half-sites on the same face of the helix. Transcription studies, in vivo, strongly confirm the rotational specificity of the p53 interaction with consensus DNA. The ability of single p53 tetramers to bind separated DNA half-sites argues that p53 has a flexible tetramerization region.Specific DNA binding and transcriptional activation play central roles in the suppression of cellular proliferation by p53 (6,29,32). Most p53 mutations that are associated with human cancer affect the central conserved region of p53 (13) that is necessary and sufficient for specific DNA binding (2, 17, 31). Indeed, many mutations severely reduce site-specific DNA binding (1, 15) and transactivation in vivo (9,16,20). In model systems, there is also an excellent correlation between the transactivation and suppression functions of p53 (19,21). Removal of the natural transactivation domain of p53 blocks suppression of transformation by other oncogenes. Replacement of the transactivation domain with the heterologous VP16 transactivation domain restores transactivation and suppression.Studies of human and murine p53 have identified a number of autonomous functional domains. The N-terminal, acidic region strongly activates transcription when positioned at a promoter either as part of p53 or as a chimera with the GAL4 DNA-binding domain (10,20). The large central conserved region of p53 binds specific DNA sequences (2, 17, 31) and forms unstable oligomers without a preference for a particular oligomeric form (30). The C-terminal region assembles stable tetramers (30) and binds to DNA without apparent specificity (31). Surprisingly, C-terminal-truncation mutants lac...

MicroRNAs (miRNAs) are emerging as important regulators in osteoarthritis (OA) pathogenesis. In our study, a real-time PCR assay revealed that miR-483-5p was upregulated in articular cartilage from OA patients and experimental OA mice induced by destabilization of the medial meniscus compared to their controls. Overexpression of miR-483-5p by intra-articular injection of lentivirus LV3-miR-483-5p significantly enhanced the severity of experimental OA. Consequently, we synthesized antago-miR-483-5p to silence the endogenous miR-483-5p and delivered it intra-articularly, which revealed that antagomiR-483-5p delayed the progression of experimental OA. To investigate the functional mechanism of miR-483-5p in OA development, we generated doxycycline-inducible miR-483 transgenic (TG483) mice. TG483 mice exhibited significant acceleration and increased severity of OA, and age-related OA occurred with higher incidence and greater severity in TG483 mice compared with their controls. Furthermore, our results revealed miR-483-5p directly targeted to the cartilage matrix protein matrilin 3 (Matn3) and tissue inhibitor of metalloproteinase 2 (Timp2) to stimulate chondrocyte hypertrophy, extracellular matrix degradation, and cartilage angiogenesis, and it consequently initiated and accelerated the development of OA. In conclusion, our findings reveal an miRNA functional pathway important for OA development. Targeting of miR-483-5p by intra-articular injection of antago-miR-483-5p represents an approach that could prevent the onset of OA and delay its progression.

Bacillus anthracis spores, the etiological agents of anthrax, possess a loosely fitting outer layer called the exosporium that is composed of a basal layer and an external hairlike nap. The filaments of the nap are formed by trimers of the collagenlike glycoprotein BclA. Multiple pentasaccharide and trisaccharide side chains are O linked to BclA. The nonreducing terminal residue of the pentasaccharide side chain is the unusual sugar anthrose. A plausible biosynthetic pathway for anthrose biosynthesis has been proposed, and an antABCD operon encoding four putative anthrose biosynthetic enzymes has been identified. In this study, we genetically and biochemically characterized the activities of these enzymes. We also used mutant B. anthracis strains to determine the effects on BclA glycosylation of individually inactivating the genes of the anthrose operon. The inactivation of antA resulted in the appearance of BclA pentasaccharides containing anthrose analogs possessing shorter side chains linked to the amino group of the sugar. The inactivation of antB resulted in BclA being replaced with only trisaccharides, suggesting that the enzyme encoded by the gene is a dTDP-␤-L-rhamnose ␣-1,3-L-rhamnosyl transferase that attaches the fourth residue of the pentasaccharide side chain. The inactivation of antC and antD resulted in the disappearance of BclA pentasaccharides and the appearance of a tetrasaccharide lacking anthrose. These phenotypes are entirely consistent with the proposed roles for the antABCD-encoded enzymes in anthrose biosynthesis. Purified AntA was then shown to exhibit ␤-methylcrotonyl-coenzyme A (CoA) hydratase activity, as we predicted. Similarly, we confirmed that purified AntC had aminotransferase activity and that purified AntD displayed N-acyltransferase activity.

BackgroundP450 fatty acid decarboxylases represented by the unusual CYP152 peroxygenase family member OleTJE have been receiving great attention recently since these P450 enzymes are able to catalyze the simple and direct production of 1-alkenes for potential applications in biofuels and biomaterials. To gain more mechanistic insights, broader substrate spectra, and improved decarboxylative activities, it is demanded to discover and investigate more P450 fatty acid decarboxylases.ResultsHere, we describe for the first time the expression, purification, and in vitro biochemical characterization of two new CYP152 peroxygenases, CYP-Aa162 and CYP-Sm46Δ29, that are capable of decarboxylating straight-chain saturated fatty acids. Both enzymes were found to catalyze the decarboxylation and hydroxylation of a broad range of free fatty acids (C10–C20) with overlapping substrate specificity, yet distinct chemoselectivity. CYP-Sm46Δ29 works primarily as a fatty (lauric) acid decarboxylase (66.1 ± 3.9% 1-undecene production) while CYP-Aa162 more as a fatty (lauric) acid hydroxylase (72.2 ± 0.9% hydroxy lauric acid production). Notably, the optical spectroscopic analysis of functional CYP-Sm46Δ29 revealed no characteristic P450 band, suggesting a unique heme coordination environment. Active-site mutagenesis analysis showed that substitution with the proposed key decarboxylation-modulating residues, His85 and Ile170, enhanced the decarboxylation activity of CYP-Aa162 and P450BSβ, emphasizing the importance of these residues in directing the decarboxylation pathway. Furthermore, the steady-state kinetic analysis of CYP-Aa162 and CYP-Sm46Δ29 revealed both cooperative and substrate inhibition behaviors which are substrate carbon chain length dependent.ConclusionsOur data identify CYP-Sm46Δ29 as an efficient OleTJE-like fatty acid decarboxylase. Oxidative decarboxylation chemoselectivity of the CYP152 decarboxylases is largely dependent upon the carbon chain length of fatty acid substrates and their precise positioning in the enzyme active site. Finally, the kinetic mode analysis of the enzymes could provide important guidance for future process design.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-017-0894-x) contains supplementary material, which is available to authorized users.

The one-electron reduction of redox-active chemotherapeutic agents generates highly toxic radical anions and reactive oxygen intermediates (ROI). A major enzyme catalyzing this process is cytochrome P450 reductase. Because many tumor cells highly express this enzyme, redox cycling of chemotherapeutic agents in these cells may confer selective antitumor activity. Nitrofurantoin is a commonly used redox-active antibiotic that possesses antitumor activity. In the present studies we determined whether nitrofurantoin redox cycling is correlated with cytochrome P450 reductase activity and cytotoxicity in a variety of cell lines. Recombinant cytochrome P450 reductase was found to support redox cycling of nitrofurantoin and to generate superoxide anion, hydrogen peroxide, and, in the presence of redox-active iron, hydroxyl radicals. This activity was NADPH dependent and inhibitable by diphenyleneiodonium, indicating a requirement for the flavin cofactors in the reductase. Nitrofurantoin-induced redox cycling was next analyzed in different cell lines varying in cytochrome P450 reductase activity including Chinese hamster ovary cells (CHO-OR) constructed to overexpress the enzyme. Nitrofurantoin-induced hydrogen peroxide production was 16-fold greater in lysates from CHO-OR cells than from control CHO cells. A strong correlation between cytochrome P450 reductase activity and nitrofurantoin-induced redox cycling among the cell lines was found. Unexpectedly, no correlation between nitrofurantoininduced ROI production and cytotoxicity was observed. These data indicate that nitrofurantoininduced redox cycling and subsequent generation of ROI are not sufficient to mediate cytotoxicity and that cytochrome P450 reductase is not a determinant of sensitivity to redox-active chemotherapeutic agents.

Asymmetric N(omega),N(omega)-dimethyl-l-arginine (ADMA) is an endogenously produced inhibitor of human nitric oxide synthase and an emerging biomarker for cardiovascular disease. Concentrations of ADMA are controlled by two isoforms of its catabolic enzyme dimethylarginine dimethylaminohydrolase (DDAH), the dysregulation of which has been studied as a mediating factor for endothelial dysfunction. A two-part, click-chemistry mediated activity-based probe, N-but-3-ynyl-2-chloroacetamidine, is shown to label myc-tagged DDAH-1 expressed in HEK 293T cells, but not an inactive mutant or inhibited enzyme. A two-color Western blotting technique is used to determine the in vivo IC(50) value for a reversible inhibitor of DDAH-1, N(5)-(1-iminopropyl)-l-ornithine, indicating this compound's bioavailability and its competition for binding to the active site. This probe provides a novel tool for the analysis of DDAH-1 activity in normal and pathophysiological states and should allow more meaningful studies of the etiology of endothelial dysfunction.

PurposeWe evaluated the effects of lentivirus-mediated exoenzyme C3 transferase (C3) expression on cultured primary human trabecular meshwork (HTM) cells in vitro, and on rat intraocular pressure (IOP).MethodsHTM cells were cultured and treated with lentivirus vectors expressing either green fluorescent protein (GFP) only (LV-GFP) or GFP and C3 together (LV-C3-GFP). Changes in cell morphology and actin stress fibers were assessed. The vectors were also injected into the anterior chamber of rats, and GFP expression was visualized by a Micron III Retinal Imaging Microscope in vivo and a fluorescence microscope ex vivo. Changes in rat IOP were monitored by using a rebound tonometer and the eyes were evaluated by slit lamp.ResultsLV-mediated C3 expression induced morphologic changes in HTM cells. The cells became retracted and rounded. GFP expression in the anterior chamber angle of rats was observed in vivo from 8 days to 48 days after injection of LV-C3-GFP or LV-GFP. IOP was significantly decreased in the LV-C3-GFP group starting 3 days post injection, and lasting for at least 40 days, when compared to either the contralateral control eyes (the LV-GFP group) or the ipsilateral baseline before injection (P < 0.05). No obvious inflammatory signs were observed in either the LV-C3-GFP or LV-GFP groups.ConclusionsLV-mediated C3 expression induced changes in morphology of cultured HTM cells. Intracameral injection of LV-C3-GFP lowered rat IOP for at least 40 days. No significant inflammatory reactions were observed in either the LV-C3-GFP or LV-GFP groups. This study supports the possible use of C3 gene therapy for the treatment of glaucoma.