Palmitoyl-CoA synthetase on the external surface of isolated rat hepatocytes

After incubating isolated rat hepatocytes with [1-¹⁴C]palmitic acid, CoA and ATP (+MgCl₂), a significant amount of [1-¹⁴C]palmitoyl-CoA was found in the incubation medium. There was no correlation between its rate of synthesis and the degree of intactness of the cells. The results indicate that there is a long-chain fatty acyl-CoA synthetase active on the external surface of the hepatocyte plasma membrane. The activity of this enzyme was negligible in primary cultures of rat hepatocytes, suggesting that the exofacial long-chain acyl-CoA synthetase is an artifact of the collagenase perfusion technique used to prepare the hepatocytes.     

Estradiol-induced progesterone receptor synthesis in normal and diabetic ovariectomized rat uterus

Estrogen stimulation of progesterone-receptor (Prog R.) synthesis is an important parameter of the sex hormones activity at the uterine level. Experimental diabetes in the rat has been shown to perturb protein synthesis in some tissues and to reduce, under certain circumstances, estrogen and androgen activity on their respective target tissues. The present work tended to evaluate the effect of streptozotocin diabetes on estradiol (E2) stimulation of Prog. R and on Prog R. kinetics in the rat uterus. Two groups of diabetic rats were primed for three consecutive days with 5 microg. E2 s.c. (EP). One group received an acute i.p. injection of progesterone (P), 1 h before sacrifice (Inj), the other group did not (n Inj). Two other groups, not primed with E2 (nEP) were similarly injected or not with P. Four groups of non diabetic animals served as controls. Estrogen priming induced a 20-25% increase in DNA content, both in controls and in diabetics. Protein content was also increased to almost the same extent in diabetics and controls; protein concentration remained however slightly lower in cytosol of EP diabetics as compared to controls. Prog R. increased about 7-fold in cytosol and 4-5-fold in nuclei of EP control and diabetic groups. Cytosol to nuclei ratios of Prog R. decreased similarly in Inj. EP diabetics and controls, compared to the corresponding n Inj. groups. It is concluded that estrogen priming stimulated Prog R., total protein and DNA synthesis to the same extent in diabetic as in control rats Prog R. kinetics was unaltered in diabetics. This finding might be relevant to situations like early pregnancy, when Prog R. levels change rapidly and specifically in relation with the time and the site of implantation.     

Hsp90 is cleaved by reactive oxygen species at a highly conserved N-terminal amino Acid motif

Hsp90 is an essential chaperone that is necessary for the folding, stability and activity of numerous proteins. In this study, we demonstrate that free radicals formed during oxidative stress conditions can cleave Hsp90. This cleavage occurs through a Fenton reaction which requires the presence of redox-active iron. As a result of the cleavage, we observed a disruption of the chaperoning function of Hsp90 and the degradation of its client proteins, for example, Bcr-Abl, RIP, c-Raf, NEMO and hTert. Formation of Hsp90 protein radicals on exposure to oxidative stress was confirmed by immuno-spin trapping. Using a proteomic analysis, we determined that the cleavage occurs in a conserved motif of the N-terminal nucleotide binding site, between Ile-126 and Gly-127 in Hsp90β, and between Ile-131 and Gly-132 in Hsp90α. Given the importance of Hsp90 in diverse biological functions, these findings shed new light on how oxidative stress can affect cellular homeostasis.     

Immobilization of Pseudorabies Virus in Porcine Tracheal Respiratory Mucus Revealed by Single Particle Tracking

Pseudorabies virus (PRV) initially replicates in the porcine upper respiratory tract. It easily invades the mucosae and submucosae for subsequent spread throughout the body via blood vessels and nervous system. In this context, PRV developed ingenious processes to overcome different barriers such as epithelial cells and the basement membrane. Another important but often overlooked barrier is the substantial mucus layer which coats the mucosae. However, little is known about how PRV particles interact with porcine respiratory mucus. We therefore measured the barrier properties of porcine tracheal respiratory mucus, and investigated the mobility of nanoparticles including PRV in this mucus. We developed an in vitro model utilizing single particle tracking microscopy. Firstly, the mucus pore size was evaluated with polyethylene glycol coupled (PEGylated) nanoparticles and atomic force microscope. Secondly, the mobility of PRV in porcine tracheal respiratory mucus was examined and compared with that of negative, positive and PEGylated nanoparticles. The pore size of porcine tracheal respiratory mucus ranged from 80 to 1500 nm, with an average diameter of 455±240 nm. PRV (zeta potential: −31.8±1.5 mV) experienced a severe obstruction in porcine tracheal respiratory mucus, diffusing 59-fold more slowly than in water. Similarly, the highly negatively (−49.8±0.6 mV) and positively (36.7±1.1 mV) charged nanoparticles were significantly trapped. In contrast, the nearly neutral, hydrophilic PEGylated nanoparticles (−9.6±0.8 mV) diffused rapidly, with the majority of particles moving 50-fold faster than PRV. The mobility of the particles measured was found to be related but not correlated to their surface charge. Furthermore, PEGylated PRV (-13.8±0.9 mV) was observed to diffuse 13-fold faster than native PRV. These findings clearly show that the mobility of PRV was significantly hindered in porcine tracheal respiratory mucus, and that the obstruction of PRV was due to complex mucoadhesive interactions including charge interactions rather than size exclusion.     

Glucopyranosyl Lipid Adjuvant (GLA), a Synthetic TLR4 agonist, promotes potent systemic and mucosal responses to intranasal immunization with HIVgp140

Successful vaccine development against HIV will likely require the induction of strong, long-lasting humoral and cellular immune responses in both the systemic and mucosal compartments. Based on the known immunological linkage between the upper-respiratory and urogenital tracts, we explored the potential of nasal adjuvants to boost immunization for the induction of vaginal and systemic immune responses to gp140. Mice were immunized intranasally with HIV gp140 together with micellar and emulsion formulations of a synthetic TLR4 agonist, Glucopyranosyl Lipid Adjuvant (GLA) and responses were compared to R848, a TLR7/8 agonist, or chitosan, a non TLR adjuvant. GLA and chitosan but not R848 greatly enhanced serum immunoglobulin levels when compared to antigen alone. Both GLA and chitosan induced high IgG and IgA titers in nasal and vaginal lavage and feces. The high IgA and IgG titers in vaginal lavage were associated with high numbers of gp140-specific antibody secreting cells in the genital tract. Whilst both GLA and chitosan induced T cell responses to immunization, GLA induced a stronger Th17 response and chitosan induced a more Th2 skewed response. Our results show that GLA is a highly potent intranasal adjuvant greatly enhancing humoral and cellular immune responses, both systemically and mucosally.     

Adaptive value of phenological traits in stressful environments: predictions based on seed production and laboratory natural selection

Phenological traits often show variation within and among natural populations of annual plants. Nevertheless, the adaptive value of post-anthesis traits is seldom tested. In this study, we estimated the adaptive values of pre- and post-anthesis traits in two stressful environments (water stress and interspecific competition), using the selfing annual species Arabidopsis thaliana. By estimating seed production and by performing laboratory natural selection (LNS), we assessed the strength and nature (directional, disruptive and stabilizing) of selection acting on phenological traits in A. thaliana under the two tested stress conditions, each with four intensities. Both the type of stress and its intensity affected the strength and nature of selection, as did genetic constraints among phenological traits. Under water stress, both experimental approaches demonstrated directional selection for a shorter life cycle, although bolting time imposes a genetic constraint on the length of the interval between bolting and anthesis. Under interspecific competition, results from the two experimental approaches showed discrepancies. Estimation of seed production predicted directional selection toward early pre-anthesis traits and long post-anthesis periods. In contrast, the LNS approach suggested neutrality for all phenological traits. This study opens questions on adaptation in complex natural environment where many selective pressures act simultaneously.     

The cDNA sequence of three hemocyanin subunits from the garden snail Helix lucorum

Hemocyanins are blue copper containing respiratory proteins residing in the hemolymph of many molluscs and arthropods. They can have different molecular masses and quaternary structures. Moreover, several molluscan hemocyanins are isolated with one, two or three isoforms occurring as decameric, didecameric, multidecameric or tubule aggregates. We could recently isolate three different hemocyanin isopolypeptides from the hemolymph of the garden snail Helix lucorum (HlH). These three structural subunits were named α_D-HlH, α_N-HlH and β-HlH. We have cloned and sequenced their cDNA which is the first result ever reported for three isoforms of a molluscan hemocyanin. Whereas the complete gene sequence of α_D-HlH and β-HlH was obtained, including the 5′ and 3′ UTR, 180 bp of the 5′ end and around 900 bp at the 3′ end are missing for the third subunit. The subunits α_D-HlH and β-HlH comprise a signal sequence of 19 amino acids plus a polypeptide of 3409 and 3414 amino acids, respectively. We could determine 3031 residues of the α_N-HLH subunit. Sequence comparison with other molluscan hemocyanins shows that α_D-HlH is more related to Aplysia californicum hemocyanin than to each of its own isopolypeptides. The structural subunits comprise 8 different functional units (FUs: a, b, c, d, e, f, g, h) and each functional unit possesses a highly conserved copper-A and copper-B site for reversible oxygen binding. Potential N-glycosylation sites are present in all three structural subunits. We confirmed that all three different isoforms are effectively produced and secreted in the hemolymph of H. lucorum by analyzing a tryptic digest of the purified native hemocyanin by MALDI-TOF and LC-FTICR mass spectrometry.     

Patients lacking classical poor prognostic markers might also benefit from a step-down glucocorticoid bridging scheme in early rheumatoid arthritis: week 16 results from the randomized multicenter CareRA trial

IntroductionConsidering a lack of efficacy data in patients with early rheumatoid arthritis (eRA) presenting without classical markers of poor prognosis, we compared methotrexate (MTX) with or without step-down glucocorticoids in the CareRA trial.MethodsDisease-modifying antirheumatic drug–naïve patients with eRA were stratified into a low-risk group based on prognostic markers that included non-erosiveness, anti–citrullinated protein antibodies and rheumatoid factor negativity and low disease activity (Disease Activity Score in 28 joints based on C-reactive protein (DAS28(CRP)) ≤3.2). Patients were randomized to 15 mg of MTX weekly (MTX with tight step-up (MTX-TSU)) or 15 mg of MTX weekly with prednisone bridging, starting at 30 mg and tapered to 5 mg daily from week 6 (COmbinatie therapie bij Reumatoïde Artritis (COBRA Slim)). A TSU approach was applied. Outcomes assessed were DAS28(CRP)-determined remission, cumulative disease activity, Health Assessment Questionnaire (HAQ) scores and adverse events (AEs) after 16 treatment weeks.ResultsWe analyzed 43 COBRA Slim and 47 MTX-TSU patients and found that 65.1% in the COBRA Slim group and 46.8% in the MTX-TSU group reached remission (P = 0.081). Mean ± standard deviation area under the curve values of DAS28(CRP) were 13.84 ± 4.58 and 11.18 ± 4.25 for the MTX-TSU and COBRA Slim patients, respectively (P = 0.006). More COBRA Slim patients had an HAQ score of 0 (51.2% versus 23.4%, P = 0.006) at week 16. Therapy-related AEs between groups did not differ.ConclusionIn patients with low-risk eRA, MTX with step-down glucocorticoid bridging seems more efficacious than MTX step-up monotherapy, with a comparable number of AEs observed over the first 16 treatment weeks.

Trial registration

EU Clinical Trials Register Identifier: EudraCT number 2008-007225-39. Registered 5 November 2008.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0611-8) contains supplementary material, which is available to authorized users.     

Resistance of the dopamine D4 receptor to agonist-induced internalization and degradation

Dopamine receptors are G-protein-coupled receptors involved in the control of motivation, learning, and fine-tuning of motor movement, as well as modulation of neuroendocrine signalling. Stimulation of G-protein-coupled receptors normally results in attenuation of signalling through desensitization, followed by internalization and down-regulation of the receptor. These processes allow the cell to regain homeostasis after exposure to extracellular stimuli and offer protection against excessive signalling.Here, we have investigated the agonist-mediated attenuation properties of the dopamine D4 receptor.We found that several hallmarks of signal attenuation such as receptor phosphorylation, internalization and degradation showed a blunted response to agonist treatment. Moreover, we did not observe recruitment of β-arrestins upon D4 receptor stimulation. We also provide evidence for the constitutive phosphorylation of two serine residues in the third intracellular loop of the D4 receptor.These data demonstrate that, when expressed in CHO, HeLa and HEK293 cells, the human D4 receptor shows resistance to agonist-mediated internalization and down-regulation. Data from neuronal cell lines, which have been reported to show low endogenous D4 receptor expression, such as the hippocampal cell line HT22 and primary rat hippocampal cells, further support these observations.