Regulatory T Cells Condition Lymphatic Endothelia for Enhanced Transendothelial Migration

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Mitochondrial Oxidative Phosphorylation Regulates the Fate Decision between Pathogenic Th17 and Regulatory T Cells

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Sensitivity of progesterone receptors to aurintricarboxylic acid: Inhibition of nuclear uptake,ATP and DNA binding

When hen oviduct cytosol samples containing progesterone receptor complexed to [³H]progesterone were included with isolated nuclei in presence of 0.2 mM aurintricarboxylic acid, more than 50% inhibition occurred in the uptake of progesterone receptor by the nuclei. The activated form of progesterone receptor appeared to be more sensitive to the presence of aurintricarboxylic acid since pretreatment of non-activated progesterone receptor with the inhibitor and the subsequent removal of the latter prior to activation did not result in the inhibition of receptor uptake by the nuclei. Also, the binding of progesterone receptor to columns of DNA-cellulose or ATP-Sepharose was abolished under simmilar conditions. When nuclei, ATP-Sepharose or DNA-cellulose were preincubated with the inhibitor prior to the addition of receptor preparations, no such inhibition resulted indicating that the inhibitor may be interacting with the receptor protein and not complexing to ATP, DNA or sites in the nuclei. The steroid binding properties of progesterone receptor, however, remained intact under these conditions. Both A and B forms of progesterone receptor are equally sensitive to aurintricarboxylic acid presence when tested for their nuclear uptake. Aurintricarboxylic acid was also found to be very effective at low concentrations (0.25 mM) in eluting the receptor complexes off ATP-Sepharose columns without disrupting the steroid binding properties of progesterone receptor. Our results suggest that auintricarboxylic acid is an effective inhibitor of progesterone receptor and that it may be acting by interfering with a site(s) on progesterone receptor which may be exposed upon activation and are involved in such processes as ATP binding, nuclear uptake and DNA binding. These observations suggest the use of aurintricarboxylic acid as a chemical probe for the analysis of progesterone receptor.     

BRE over-expression promotes growth of hepatocellular carcinoma

BRE, also known as TNFRSF1A modulator and BRCC45, is an evolutionarily highly conserved protein. It is a death receptor-associated protein in cytoplasm and a component of BRCA1/2-containing DNA repair complex in nucleus. BRE was found to have anti-apoptotic activity. Over-expression of BRE by transfection promoted survival of cell lines against apoptotic induction; whereas depletion of the protein by siRNA resulted in the opposite. In vivo anti-apoptotic activity of BRE was demonstrated by significant attenuation of Fas-induced acute fulminant hepatitis in transgenic mice expressing the human protein specifically in the liver. BRE was also implicated in tumor promotion by the accelerated tumor growth of Lewis Lung carcinoma transfected with human BRE; and by high expression of BRE specifically in the tumoral regions of human hepatocellular carcinoma (HCC). The present study was to test directly if transgenic expression of BRE in livers could promote HCC development in neonatal diethylnitrosamine model. By 8 months after tumor induction, the maximal sizes of tumor nodules of transgenic mice were significantly larger than those of the non-transgenic controls, although the numbers of tumor nodules between the two groups did not significantly differ. Importantly, as in human HCC, the mouse endogenous BRE level was up-regulated in mouse HCC nodules. These results show that BRE over-expression can indeed promote growth, though not initiation, of liver tumors. Furthermore, the common occurrence of BRE over-expression in human and mouse HCC suggests that up-regulation of BRE is functionally important in liver tumor development.     

Stimulation of the P2Y Purinergic Receptor on Type 1 Astroglia Results in Inositol Phosphate Formation and Calcium Mobilization

Cultured astroglia express purinergic receptors that initiate phosphoinositide metabolism and calcium mobilization. Experiments were conducted to characterize the purinergic receptor subtype on type 1 astroglia responsible for stimulation these second-messenger systems. Inositol phosphate (IP) accumulation and calcium mobilization were measured after stimulation with ATP or purinergic receptor subtype-selective ATP analogues. ATP (10(-5) M) increased IP accumulation severalfold. Dose-effect assays monitoring astroglial IP accumulation revealed the order of potency that defines the P2Y receptor: 2-methylthioadenosine 5'-triphosphate greater than ATP greater than alpha beta-methyleneadenosine 5'-triphosphate greater than beta gamma-methyleneadenosine 5'-triphosphate. The influence of ATP on intracellular calcium levels in individual type 1 astroglia was examined using the calcium indicator dye, fura-2. Dose-effect experiments indicated that ATP was equally potent for generating inositol phosphates and increasing cellular calcium. The most prevalent response (87% of total responses) to ATP consisted of a rapid increase in calcium to a peak level that was approximately five times greater than the prestimulation level. This peak was followed by a decline to a plateau level that was significantly above baseline. This plateau phase of the calcium increase was maintained for at least 5 min in the presence of ATP and was dependent on external calcium. Many (23%) astroglia exhibited spontaneous calcium oscillations whose frequency and magnitude increased after the addition of 10(-5) M ATP. Immunocytochemical staining indicated that the responses occurred in glial fibrillary acidic protein positive cells. We conclude that type 1 astroglia express the P2Y purinergic receptor which regulates IP production and calcium mobilization.     

Identification of significant regions of transcription factor DP-1 (TFDP-1) involved in stability/instability of the protein

We previously reported the identification of DP-1 isoforms (α and β), which are structurally C-terminus-deleted ones, and revealed the low-level expression of these isoforms. It is known that wild-type DP-1 is degraded by the ubiquitin-proteasome system, but few details are known about the domains concerned with the protein stability/instability for the proteolysis of these DP-1 isoforms. Here we identified the domains responsible for the stability/instability of DP-1. Especially, the DP-1 “Stabilon” domain was a C-terminal acidic motif and was quite important for DP-1 stability. Moreover, we propose that this DP-1 Stabilon may be useful for the stability of other nuclear proteins when fused to them.     

Serotonin Inhibits Acetylcholine Release from Rat Striatum Slices: Evidence for a Presynaptic Receptor-Mediated Effect

Rat brain striatum slices were incubated with [3H]choline, perfused with a physiological buffer, and stimulated by perfusion with a K+-enriched buffer for 2 min. The tritium overflow evoked by K+ was decreased by 5-hydroxytryptamine (serotonin, 5-HT) (maximal inhibition 10(-6) M). This effect of 5-HT was mimicked by several agonists (5-methoxytryptamine, N,N-dimethyl-tryptamine, bufotenin) and blocked by serotonergic antagonists (methiothepin, methysergide, cinanserin) but not by haloperidol; methiothepin and methysergide alone slightly increased the K+-evoked overflow of tritium (3H). Inhibition of the tritium release by 5-HT was not suppressed in the presence of tetrodotoxin (TTX) (10(-6) M). These results suggest that 5-HT tonically inhibits acetylcholine (ACh) release from striatal cholinergic neurons by acting on a presynaptic receptor localized on cholinergic terminals.     

Characterization by [3H]Dihydroergocryptine Binding of Alpha-Adrenergic Receptors in Neuroblastoma × Glioma Hybrid Cells

[3H]Dihydroergocryptine ([3H]DHE) was shown to bind to sites in membranes from neuroblastoma X glioma hybrid cells (NG 108-15) that had the characteristics expected of alpha-adrenergic receptors. The binding was saturable with 0.3 pmol [3H]DHE bound per mg of protein and of high affinity, with an apparent dissociation constant (KD) of 1.8 nM. The specificity of the binding site for various ligands was more similar to that of alpha 2 receptors than to that of alpha 1. No specific binding of [3H]WB-4101 was found in the membranes derived from NG 108 cells. This finding also indicated that the [3H]DHE binding site in the cell is the alpha 2 receptor. GTP lowered the affinity of agonists for the [3H]DHE binding site, although the nucleotide hardly affected the affinity of antagonists including [3H]DHE.     

Adenosine mediates transforming growth factor-beta 1 release in kidney glomeruli of diabetic rats

Up regulation of the transforming growth factor-beta 1 (TGF-β1) axis has been recognized as a pathogenic event for progression of glomerulosclerosis in diabetic nephropathy. We demonstrate that glomeruli isolated from diabetic rats accumulate up to sixfold more extracellular adenosine than normal rats. Both decreased nucleoside uptake activity by the equilibrative nucleoside transporter 1 and increased AMP hydrolysis contribute to raise extracellular adenosine. Ex vivo assays indicate that activation of the low affinity adenosine A_2B receptor subtype (A_2BAR) mediates TGF-β1 release from glomeruli of diabetic rats, a pathogenic event that could support progression of glomerulopathy when the bioavailability of adenosine is increased.