The localization and phosphorylation of p47 are important for Golgi disassembly-assembly during the cell cycle

In mammalian cells, the Golgi apparatus is disassembled at the onset of mitosis and reassembled at the end of mitosis. This disassembly-reassembly is generally believed to be essential for the equal partitioning of Golgi into two daughter cells. For Golgi disassembly, membrane fusion, which is mediated by NSF and p97, needs to be blocked. For the NSF pathway, the tethering of p115-GM130 is disrupted by the mitotic phosphorylation of GM130, resulting in the inhibition of NSF-mediated fusion. In contrast, the p97/p47 pathway does not require p115-GM130 tethering, and its mitotic inhibitory mechanism has been unclear. Now, we have found that p47, which mainly localizes to the nucleus during interphase, is phosphorylated on Serine-140 by Cdc2 at mitosis. The phosphorylated p47 does not bind to Golgi membranes. An in vitro assay shows that this phosphorylation is required for Golgi disassembly. Microinjection of p47(S140A), which is unable to be phosphorylated, allows the cell to keep Golgi stacks during mitosis and has no effect on the equal partitioning of Golgi into two daughter cells, suggesting that Golgi fragmentation-dispersion may not be obligatory for equal partitioning even in mammalian cells.     

HVJ-envelope vector for gene transfer into central nervous system

To overcome some problems of virus vectors, we developed a novel non-viral vector system, the HVJ-envelope vector (HVJ-E). In this study, we investigated the feasibility of gene transfer into the CNS using the HVJ-E both in vitro and in vivo. Using the Venus reporter gene, fluorescence could be detected in cultured rat cerebral cortex neurons and glial cells. In vivo, the reporter gene (Venus) was successfully transfected into the rat brain by direct injection into the thalamus, intraventricular injection, or intrathecal injection, without inducing immunological change. When the vector was injected after transient occlusion of the middle cerebral artery, fluorescence due to EGFP gene or luciferase activity could be detected only in the injured hemisphere. Finally, luciferase activity was markedly enhanced by the addition of 50 U/ml heparin (P<0.01). Development of efficient HVJ-E for gene transfer into the CNS will be useful for research and clinical gene therapy.     

A dominant negative TAK1 inhibits cellular fibrotic responses induced by TGF-beta

Transforming growth factor-beta (TGF-beta) is crucially virulent in the progression of fibrotic disorders. TAK1 (TGF-beta activated kinase 1) is one of the mitogen-activated kinase kinase kinase (MAPKKK) that is involved in TGF-beta signal transduction. To elucidate the importance of TAK1 in TGF-beta-induced fibrotic marker expression, we investigated whether dominant negative TAK1 could suppress TGF-beta signaling. Based on the finding that TAB1 (TAK1 binding protein 1) binding to TAK1 is required for TAK1 activation, a minimal portion of TAK1 lacking kinase activity that binds to TAB1 was designed as a TAK1 dominant negative inhibitor (TAK1-DN). The effect of TAK1-DN was assessed in the cells that respond to TGF-beta stimulation and that lead to the increase in production of extracellular matrix (ECM) proteins. TAK1-DN, indeed, decreased the ECM protein production, indicating that TAK1-DN retains the ability to intercept the TGF-beta signaling effectively.     

Inducible liver injury in the transgenic rat by expressing liver-specific suicide gene

Suicide gene expression in specific tissue of transgenic animals has been used for cell-specific ablation. To examine the influence of hepatocyte removal, we produced the herpes simplex virus thymidine kinase (HSVtk) transgenic rat, whose gene was regulated by an albumin enhancer promoter. The liver presence of HSVtk was demonstrated in one line of the transgenic rats. We injected ganciclovir (GCV, 50mg/kg) into the rat on alternate days. After 28 days of GCV administration, liver tissues, and blood of the rats were collected. The histological investigation revealed infiltration of T cells, macrophages, granulocytes/neutrophils, and hepatocyte cell death. The biochemistry analysis demonstrated elevated levels of AST, ALT, and total bilirubin in transgenic rat. In conclusion, the transgenic rat with expressed albumin-specific HSVtk developed experimental hepatitis with administration of GCV, and will be a useful model to facilitate the evaluation of drug effects for clinical control of liver disease.     

Pioglitazone reduces monocyte adhesion to vascular endothelium under flow by modulating RhoA GTPase and focal adhesion kinase

Thiazolidinediones (TZDs), potent peroxisome proliferator-activated receptor gamma ligands, have been shown to improve endothelial function in vascular diseases. We investigated the effects of pioglitazone, a TZD, on monocyte-endothelial interaction under flow and found that pretreatment (20 mumol/l, 48 h) significantly reduced U937 adhesion to human umbilical vein endothelial cells. Integrin expression was not altered, however, the activation of RhoA GTPase was significantly reduced after treatment. Further, pioglitazone treatment significantly reduced phosphorylation of focal adhesion kinase (FAK) at 925Y, but not at 397Y, suggesting a specific role in FAK-dependent signaling. These results indicate a novel anti-inflammatory role for this compound.     

Differential expression of two cathepsin Es during metamorphosis-associated remodeling of the larval to adult type epithelium in Xenopus stomach

Cathepsin E (CE) was purified from the foregut of Xenopus laevis tadpoles as a mature dimeric form. The purified enzyme was a typical CE among aspartic proteinases with respect to pH dependence of proteolytic activity, susceptibility to pepstatin, and having N-linked high-mannose type oligosaccharide chains. We isolated two cDNAs for the CE (CE1 and CE2) from adult stomach. The amino acid sequence of the N-terminal region of the purified CE coincided with the corresponding sequence predicted from CE1. Northern blot analysis and in situ hybridization were performed. The CE1 mRNA was highly expressed in surface mucous cells and gland cells constituting the larval epithelium of the foregut of pro-metamorphic tadpoles. As metamorphosis began and progressed, CE1 mRNA drastically decreased in amount, and subsequently both CE1 and CE2 mRNAs gradually increased. The increase in CE2 mRNA was detected shortly after the increase in CE1 mRNA. The decrease in CE1 expression correlated with degeneration of the larval type epithelium, while the increases in both CE1 and CE2 expression correlated with formation of the adult type epithelium. Thus, cathepsin E gene expression was differentially regulated during metamorphosis-associated remodeling of the larval to adult type epithelium in stomach.