Cellular functions of GEF-H1, a microtubule-regulated Rho-GEF: is altered GEF-H1 activity a crucial determinant of disease pathogenesis?

The Rho guanine nucleotide exchange factor GEF-H1 is uniquely regulated by microtubule binding and is crucial in coupling microtubule dynamics to Rho-GTPase activation in a variety of normal biological situations. Here, we review the roles of GEF-H1 in epithelial barrier permeability, cell motility and polarization, dendritic spine morphology, antigen presentation, leukemic cell differentiation, cell cycle regulation, and cancer. GEF-H1 might also contribute to pathophysiological signaling involved in leukemias, and in cancers associated with mutated p53 tumor suppressor gene, epithelial and endothelial cell dysfunction, infectious disease, and cardiac hypertrophy. We suggest that GEF-H1 could be a novel therapeutic target in multiple human diseases.     

Mind bomb 1-expressing intermediate progenitors generate notch signaling to maintain radial glial cells

Notch signaling is critical for the stemness of radial glial cells (RGCs) during embryonic neurogenesis. Although Notch-signal-receiving events in RGCs have been well characterized, the signal-sending mechanism by the adjacent cells is poorly understood. Here, we report that conditional inactivation of mind bomb-1 (mib1), an essential component for Notch ligand endocytosis, in mice using the nestin and hGFAP promoters resulted in complete loss of Notch activation, which leads to depletion of RGCs, and premature differentiation into intermediate progenitors (IPs) and finally neurons, which were reverted by the introduction of active Notch1. Interestingly, Mib1 expression is restricted in the migrating IPs and newborn neurons, but not in RGCs. Moreover, sorted Mib1+ IPs and neurons can send the Notch signal to neighboring cells. Our results reveal that not only newborn neurons but also IPs are essential Notch-ligand-presenting cells for maintaining RGC stemness during both symmetric and asymmetric divisions.     

Toll-like receptor 9-stimulated monocyte chemoattractant protein-1 is mediated via JNK-cytosolic phospholipase A2-ROS signaling

Monocyte chemoattractant protein-1 (MCP-1) influences monocyte migration into sites of inflammation. This study highlights the importance of cytosolic phospholipase A2 (cPLA2)-mediated reactive oxygen species (ROS) signaling processes in the regulation of MCP-1 release as a result of toll-like receptor (TLR) activation. In macrophages, activation of TLR9 induced MCP-1 and cPLA2-phosphorylated arachidonic acid (AA) release. Inhibition of cPLA2 blocked CpG-induced MCP-1 and AA release. Although CpG stimulates phosphorylation of ERK, p38 and JNK, only inhibition of the JNK signaling pathways attenuated MCP-1 release, suggesting that the TLR9-mediated MCP-1 release was dependent upon the JNK pathway. TLR9 activation also stimulated ROS generation, while inhibition of NADPH oxidases (Noxs) blocked CpG-induced MCP-1 release. The CpG treatment increased macrophage Nox1 mRNA level, however it had no effect on macrophage Nox2 mRNA level. Overall, these results suggest that CpG enhances ROS generation through cPLA2-dependent pathways, which results in MCP-1 release.     

Variation in demographic and fine-scale genetic structure with population-history stage of <Emphasis Type="Italic">Hemerocallis taeanensis</Emphasis> (Liliaceae) across the landscape

Fine-scale genetic structure (FSGS) in plant populations is expected to be influenced by variation in demographic processes across space and over time. I chose Hemerocallis taeanensis (Liliaceae), a perennial herb with a rapid population turnover, to quantify how demographic structure and FSGS change with a population’s history (i.e., density). Nonaccumulative O-ring statistic and spatial autocorrelation analysis (kinship coefficient, F _ij ) were used to quantify spatial patterns of individuals and FSGS in four populations belonging to two population stages (expansion and maturation) in west-central Korea. The O-ring function revealed that significant aggregation of individuals occurs at short spatial scales during the earlier stage of population expansion, which reflects restricted seed dispersal around maternal individuals. However, this pattern disappears as the population density increases during population maturation, probably due to a high population density. Significant evidence of FSGS was found in two populations at the stage of population expansion (Sp, a statistic which describes the rate of decrease of pairwise kinship with distance, was 0.018 and 0.029). The results show that most seeds fall around maternal plants when initially established colonists proliferate at suitable microhabitats. In contrast to this, much lower Sp values (−0.003 and 0.004) were estimated for two populations at the stage of population maturation, which may result from the overlapping of seed shadows due to high adult density. All of these results demonstrate considerable variation in within-population demographic and genetic structures of H. taeanensis with respect to population temporal stage across the landscape.     

Superhydrophobicity of cellulose triacetate fibrous mats produced by electrospinning and plasma treatment

Nano/micro-fibrous cellulose triacetate (CTA) mats were prepared by electrospinning a fixed concentration of CTA with different methylene chloride (MC)/ethanol (EtOH) ratios and with various concentrations of CTA at a fixed MC/EtOH 80/20 (v/v) ratio. All of the electrospun CTA mats had a high water contact angle (WCA) compared to the CTA cast film. At a solvent composition of 80/20 (v/v) and 5 wt.% CTA concentration, the CTA mat without plasma treatment had good surface roughness and electrospinning processability, and its WCA was 142°. To further improve its hydrophobicity, the CTA fibrous mat electrospun from the 5 wt.% solution of CTA was treated with a CF₄ plasma for various times. Superhydrophobicity could be obtained after the CF₄ plasma treatment. The WCA of the CTA mat reached as high as 153° after plasma treatment for 60 s.     

cDNA cloning and analysis of tissue-specific gene expression of rat urocortin II

The corticotropin-releasing hormone (CRH) family of neuropeptides includes CRH (a 41-amino acid hypothalamic peptide) and urocortin. Corticotropin-releasing factor (CRF), a peptide first isolated from mammalian, plays an important role in the regulation of the pituitary-adrenal axis, and in endocrine, autonomic, immune and behavioral responses to stress. In this study, we cloned rat urocortin II (UCN II) cDNA from rat mid-brain by RT-PCR. The rat UCN II clone contained an open reading frame (ORF) 109 amino acids which shared 90% and 63% homology with mouse and human homologues, respectively. The expression of UCN II mRNA is mainly distributed in bone marrow, ovary, uterus, hypophysis, adrenal gland, and skin. In this study, rat recombinant UCN was expressed in E. coli and purified in active form. Furthermore, purified recombinant UCN II protein specifically binds to CRF receptor 2 in rat ROS 17 / 2.8 and GH3 cells by flow-cytometry analysis. UCN II cDNA clone obtained in this study will be useful for further investigation on behavioral responses to stress in rats.     

Quercetin‐induced upregulation of human GCLC gene is mediated by cis‐regulatory element for early growth response protein‐1 (EGR1) in INS‐1 beta‐cells

The catalytic subunit of γ‐glutamylcysteine ligase (GCLC) catalyses the rate‐limiting step in the de novo synthesis of glutathione (GSH), which is involved in maintaining intracellular redox balance. GSH is especially important for antioxidant defense system since beta‐cells show intrinsically low expression of antioxidant enzymes. In the present study, we investigated the regulatory mechanisms by which quercetin, a flavonoid, induces the expression of the GCLC gene in rat pancreatic beta‐cell line INS‐1. Promoter study found that the proximal GC‐rich region (from ?90 to ?34) of the GCLC promoter contained the quercetin‐responsive cis‐element(s). The quercetin‐responsive region contains consensus DNA binding site for early growth response 1 (EGR1) at ‐67 (5′‐CGCCTCCGC‐3′) which overlaps with a putative Sp1 binding site. Electrophoretic mobility shift assay showed that an oligonucleotide containing the EGR1 site was bound to nuclear factors EGR1, Sp1, and Sp3. In the promoter analysis, mutation of EGR1 site significantly reduced the quercetin response, whereas mutation of Sp1 site decreased only the basal activity of the GCLC promoter. Additionally, the transient overexpression of EGR1 significantly increased basal activity of the GCLC promoter. Finally, we showed that quercetin potently induced both EGR1 mRNA and its protein levels without affecting the expression of Sp1 and Sp3 proteins. Therefore, we concluded that EGR1 was bound to GC‐rich region of the GCLC gene promoter, which was prerequisite for the transactivation of the GCLC gene by quercetin. J. Cell. Biochem. 108: 1346–1355, 2009. © 2009 Wiley‐Liss, Inc.     

Down-regulation of FoxO-dependent c-FLIP expression mediates TRAIL-induced apoptosis in activated hepatic stellate cells

Activated hepatic stellate cells which contribute to liver fibrosis have represented an important target for antifibrotic therapy. In this study, we found that TRAIL inhibited PI3K/Akt-dependent FoxO phosphorylation and relocated FoxO proteins into the nucleus from the cytosol in activated human hepatic stellate LX-2 cells. The accumulated FoxO proteins in the nucleus led to down-regulation of c-FLIP_L/S expression, resulting in the activation of apoptosis-related signaling molecules including the activation of caspase-8, -3, and Bid, as well as mitochondrial cytochrome c release. These results were supported by showing that siRNA-mediated knockdown of FoxO led to restoration of c-FLIP_L/S expression and resistance to TRAIL-induced apoptosis after treatment of LX-2 cells with TRAIL. Furthermore, c-FLIP_L/S-transfected LX-2 cells showed the decreased sensitivity to TRAIL-induced apoptosis. Collectively, our data suggest that sequential activation of FoxO proteins under conditions of suppressed PI3K/Akt signaling by TRAIL can down-regulate c-FLIP_L/S, consequently promoting TRAIL-induced apoptosis in LX-2 cells. Therefore, the present study suggests TRAIL may be an effective strategy for antifibrotic therapy in liver fibrosis.     

Design and synthesis of 4-aryl-4-oxobutanoic acid amides as calpain inhibitors

The involvement of μ-calpain in neurological disorders, such as stroke and Alzheimer’s disease has attracted considerable interest in the use of calpain inhibitors as therapeutic agents. 4-Aryl-4-oxobutanoic acid amide derivatives 4 were designed as acyclic variants of μ-calpain inhibitory chromone and quinolinone derivatives. Of the compounds synthesized, 4c-2, which possesses a 2-methoxymethoxy group at the phenyl ring and a primary amide at the warhead region most potently inhibited μ-calpain (IC₅₀ = 0.34 μM). Our findings suggest that the 4-aryl-4-oxobutanoic acid amide derivatives should be considered as a new family of μ-calpain inhibitors.