Ectopic CRYPTOCHROME renders TIM light sensitive in the Drosophila ovary

The period (per) and timeless (tim) genes play a central role in the Drosophila circadian clock mechanism. PERIOD (PER) and TIMELESS (TIM) proteins periodically accumulate in the nuclei of pace-making cells in the fly brain and many cells in peripheral organs. In contrast, TIM and PER in the ovarian follicle cells remain cytoplasmic and do not show daily oscillations in their levels. Moreover, TIM is not light sensitive in the ovary, while it is highly sensitive to this input in circadian tissues. The mechanism underlying this intriguing difference is addressed here. It is demonstrated that the circadian photoreceptor CRYPTOCHROME (CRY) is not expressed in ovarian tissues. Remarkably, ectopic cry expression in the ovary is sufficient to cause degradation of TIM after exposure to light. In addition, PER levels are reduced in response to light when CRY is present, as observed in circadian cells. Hence, CRY is the key component of the light input pathway missing in the ovary. However, the factors regulating PER and TIM levels downstream of light/cry action appear to be present in this non-circadian organ.     

Microbial transformations of flavanone and 6-hydroxyflavanone by Aspergillus niger strains

Flavanone (1) and 6-hydroxyflavanone (2) were subjected to transformation by means of Aspergillus niger strains (one wild and three UV mutants). For both substrates the biotransformation resulted in reduction of the carbonyl group (products 5 and 7) and dehydrogenation at C-2 and C-3 (3 and 8). Additionally, for flavanone (1) reduction of C-4 together with hydroxylation at C-7 (6) and dehydrogenation at C-2, C-3 along with hydroxylation at C-3 (4) were observed.     

Synthesis and SAR-study for novel arylpiperazine derivatives of 5-arylidenehydantoin with α₁-adrenoceptor antagonistic properties

The study is focused on a series of 5-arylidenehydantoin derivatives with a phenylpiperazine-hydroxypropyl fragment at N3 of the hydantoin ring. The compounds were assessed on their affinity for α(1)-adrenoceptors and evaluated in functional bioassays for their antagonistic properties. Crystal structures of (Z)-5-(4-chlorobenzylidene)-3-(3-(4-(2-ethoxyphenyl)piperazin-1-yl)-2-hydroxypropyl)imidazolidine-2,4-dione (7) and hydrochloride of (Z)-5-(4-chlorobenzylidene)-3-(2-hydroxy-3-(4-(2-methoxyphenyl)piperazin-1-yl)propyl)imidazolidine-2,4-dione (10a) were solved using the X-ray diffraction method. Classical molecular mechanics (MMFFs force field, MCMM, MacroModel) were used to predict 3D structure of compounds 5a-18a using a crystal structure of 7. SAR analysis was performed on the basis of Barbaro's pharmacophore model and structural properties of previously investigated α(1)-adrenoceptor antagonists possessing a hydantoin fragment. Most of the compounds exhibited significant affinities for α(1)-ARs in nanomolar range (40-290 nM). The highest activities (K(i)<75 nM) were observed for compounds possessing a 2-alkoxyphenylpiperazine fragment and two methoxy substituents at the benzylidene moiety. The results indicated that chemical properties, number and positions of substituents at the 5-arylidene fragment influenced the power of α(1)-affinities as follows: 3,4-di CH(3)O>2,4-di CH(3)O>4-Cl>2,3-di CH(3)O>H>4-N(CH(3))(2).     

The proprotein convertase PCSK9 induces the degradation of low density lipoprotein receptor (LDLR) and its closest family members VLDLR and ApoER2

The proprotein convertase PCSK9 gene is the third locus implicated in familial hypercholesterolemia, emphasizing its role in cardiovascular diseases. Loss of function mutations and gene disruption of PCSK9 resulted in a higher clearance of plasma low density lipoprotein cholesterol, likely due to a reduced degradation of the liver low density lipoprotein receptor (LDLR). In this study, we show that two of the closest family members to LDLR are also PCSK9 targets. These include the very low density lipoprotein receptor (VLDLR) and apolipoprotein E receptor 2 (ApoER2) implicated in neuronal development and lipid metabolism. Our results show that wild type PCSK9 and more so its natural gain of function mutant D374Y can efficiently degrade the LDLR, VLDLR, and ApoER2 either following cellular co-expression or re-internalization of secreted human PCSK9. Such PCSK9-induced degradation does not require its catalytic activity. Membrane-bound PCSK9 chimeras enhanced the intracellular targeting of PCSK9 to late endosomes/lysosomes and resulted in a much more efficient degradation of the three receptors. We also demonstrate that the activity of PCSK9 and its binding affinity on VLDLR and ApoER2 does not depend on the presence of LDLR. Finally, in situ hybridization show close localization of PCSK9 mRNA expression to that of VLDLR in mouse postnatal day 1 cerebellum. Thus, this study demonstrates a more general effect of PCSK9 on the degradation of the LDLR family that emphasizes its major role in cholesterol and lipid homeostasis as well as brain development.     

Lipoic acid ameliorates oxidative stress and renal injury in alloxan diabetic rabbits

The therapeutic potential of lipoic acid (LA) in diabetes and diabetic nephropathy treatment was elucidated. Alloxan diabetic rabbits were treated daily for three weeks with either 10 or 50 mg of LA per kg body weight (i.p.). The following parameters were measured: 1) serum glucose, urea, creatinine and hydroxyl free radical (HFR) levels; 2) blood glutathione redox state; 3) urine albumin concentration; 4) hepatic and renal HFR levels, GSH/GSSG ratios, cysteine contents and the activities of the enzymes of glutathione metabolism; and 5) the activity of renal NADPH oxidase. Histological studies of kidneys were also performed. The treatment of diabetic rabbits with 50 mg of LA resulted in lethal hypoglycaemia in 50% of animals studied. Although the low dose of LA did not change serum glucose concentration, it decreased serum urea and creatinine concentrations, attenuated diabetes-induced decline in GSH/GSSG ratio and abolished hydroxyl free radicals accumulation in serum, liver and kidney cortex. LA did not change the activities of the enzymes of glutathione metabolism, but it elevated hepatic content of cysteine, which limits the rate of glutathione biosynthesis. Moreover, LA lowered urine albumin concentration and attenuated glomerulopathy characteristic of diabetes. However, it did not affect diabetes-stimulated activity of renal NADPH oxidase. In view of these data, it is concluded that low doses of LA might be useful for the therapy of diabetes and diabetic nephropathy. Beneficial action of LA seems to result mainly from direct scavenging of HFR and restoring glutathione redox state due to elevation of intracellular cysteine levels.     

Construction and preliminary characterisation of mini-derivatives of a large (107-kb) cryptic plasmid of the sulfur bacterium Thiobacillus versutus

Abstract Several mini-replicons, derivatives of a large (107-kb) cryptic Thiobacillus versutus pTAV1 plasmid, were obtained. The pTAV1 derivatives confer all functions sufficient for autonomous replication in T. versutus but they cannot be maintained in Escherichia coli . The fragment of pTAV1 (4-kb) included in the smallest mini-replicon, pTAV202, encodes for two proteins of approximately 26 and 45 kDa. The region responsible for stable maintenance of pTAV1 derivatives (and presumably entire pTAV1) was located in defined 14-kb fragment of pTAV1 genome. Hybrid plasmids composed of E. coli vectors (pBGS18 or pWSK29) and pTAV202 replicon were constructed and their activity in both hosts tested.