Molecular characterization of water-selective AQP (EbAQP4) in hagfish: insight into ancestral origin of AQP4

Hagfish (Eptatretus burgeri) are agnathous and are the earliest vertebrates still in existence. Pavement cells adjacent to the mitochondria-rich cells show orthogonal arrays of particles (OAPs) in the gill of hagfish, a known ultrastructural morphology of aquaporin (AQP) in mammalian freeze-replica studies, suggesting that an AQP homolog exists in pavement cells. We therefore cloned water channels from hagfish gill and examined their molecular characteristics. The cloned AQP [E. burgeri AQP4 (EbAQP4)] encodes 288 amino acids, including two NPA motifs and six transmembrane regions. The deduced amino acid sequence of EbAQP4 showed high homology to mammalian and avian AQP4 (rat, 44%; quail, 43%) and clustered with AQP4 subsets by the molecular phylogenetic tree. The osmotic water permeability of Xenopus oocytes injected with EbAQP4 cRNA increased eightfold compared with water-injected controls and was not reversibly inhibited by 0.3 mM HgCl(2). EbAQP4 mRNA expression in the gill was demonstrated by the RNase protection assay; antibody raised against the COOH terminus of EbAQP4 also detected (by Western blot analysis) a major approximately 31-kDa band in the gill. Immunohistochemistry and immunoelectron microscopy showed EbAQP4 localized along the basolateral membranes of gill pavement cells. In freeze-replica studies, OAPs were detected on the protoplasmic face of the split membrane comprising particles 5-6 nm long on the basolateral side of the pavement cells. These observations suggest that EbAQP4 is an ancestral water channel of mammalian AQP4 and plays a role in basolateral water transport in the gill pavement cells.     

Anti-tumor agents 255: novel glycyrrhetinic acid-dehydrozingerone conjugates as cytotoxic agents

Esterification of glycyrrhetinic acid (GA) with dehydrozingerone (DZ) resulted in a novel cytotoxic GA-DZ conjugate. Based on this exciting finding, we conjugated eleven different DZ analogs with GA or other triterpenoids, including oleanoic acid (OA) or ursolic acid (UA). In an in vitro anti-cancer assay using nine different human tumor cell lines, most of the GA-DZ conjugates showed significant potency. Particularly, compounds 5, 29, and 30 showed significant cytotoxic effects against LN-Cap, 1A9, and KB cells with ED(50) values of 0.6, 0.8, and 0.9 microM, respectively. Similar conjugates between DZ and OA or UA were inactive suggesting that the GA component is critical for activity. Notably, although GA-DZ conjugates showed potent cytotoxic activity, the individual components (GA and DZ analogs) were inactive. Thus, GA-DZ conjugates are new chemical entities and represent interesting hits for anti-cancer drug discovery and development.     

Expression and localization of Parkinson's disease-associated leucine-rich repeat kinase 2 in the mouse brain

Mutations in the gene encoding leucine-rich repeat kinase 2 (LRRK2) have been identified as the cause of familial Parkinson's disease (PD) at the PARK8 locus. To begin to understand the physiological role of LRRK2 and its involvement in PD, we have investigated the distribution of LRRK2 mRNA and protein in the adult mouse brain. In situ hybridization studies indicate sites of mRNA expression throughout the mouse brain, with highest levels of expression detected in forebrain regions, including the cerebral cortex and striatum, intermediate levels observed in the hippocampus and cerebellum, and low levels in the thalamus, hypothalamus and substantia nigra. Immunohistochemical studies demonstrate localization of LRRK2 protein to neurones in the cerebral cortex and striatum, and to a variety of interneuronal subtypes in these regions. Furthermore, expression of LRRK2 mRNA in the striatum of VMAT2-deficient mice is unaltered relative to wild-type littermate controls despite extensive dopamine depletion in this mouse model of parkinsonism. Collectively, our results demonstrate that LRRK2 is present in anatomical brain regions of direct relevance to the pathogenesis of PD, including the nigrostriatal dopaminergic pathway, in addition to other regions unrelated to PD pathology, and is likely to play an important role in the normal function of telencephalic forebrain neurones and other neuronal populations.     

Putative mechanism of the itch-scratch circle: repeated scratching decreases the cutaneous level of prostaglandin D2, a mediator that inhibits itching

In atopic dermatitis, scratching of the skin as a reaction to itching causes injury to the skin, which, in turn, further increases the itching resulting in the establishment of the so-called itch-scratch circle. We have shown that prostaglandin (PG) D2 plays an inhibitory role against pruritus in mice with atopic-like dermatitis; therefore, we examined the relationship between scratching and the cutaneous PGD2 level using an artificial scratching model with a wire brush. Mechanical scratching induced a temporary increase of the skin PGs levels (PGE2, PGD2, 6-ketoPGF1alpha, PGF2alpha). The skin PGD2 level and the ability of PGD2 production decreased at 48 h after repeated scratch, compared to that of normal skin, not so after single scratch. Immunohistochemical analysis and Western blotting revealed a decrease in the levels of cyclooxygenase-1 (COX-1) and hematopoietic PGD synthase in mechanically scratched skin. The reduced ability of the skin for PGD2 production following mechanical scratching could be caused by this decrease in the expression levels of COX-1 and PGD2 synthase. The results suggest that repeated scratching in mice decreases the ability of the skin to produce PGD2, which is an endogenous mediator that inhibits pruritus, resulting in the establishment of the itch-scratch circle.     

Bovine papilloma virus encoded E2 protein activates lymphokine genes through DNA elements, distinct from the consensus motif, in the long control region of its own genome.

Activation of T cells by antigen, lectin or a combination of phorbol ester (PMA) and calcium ionophore (A23187) leads to the induction of a set of lymphokine genes. Transfection of a human T cell leukemia cell line, Jurkat, or an African green monkey kidney cell line, CV1, with a cDNA encoding E2 protein, a trans-activator of bovine papilloma virus type 1, results in activation of interleukin 2 (IL-2), interleukin 3 (IL-3) and granulocyte/macrophage colony-stimulating factor (GM-CSF) genes in a transient transfection assay. 5' deletion and mutation analyses showed that the sequence between positions -60 and a TATA-like sequence is required for basic promotor function and that the sequence between positions -95 and -73 containing conserved lymphokine element 2 (CLE2) and a GC box (CLE2/GC box) mediates the positive response to E2 protein. The latter has been previously shown to respond to PMA/A23187 stimulation or to p40tax, a trans-activator encoded by human T cell leukemia virus type 1 (HTLV-I). The sequence located between -108 and -99 (CLE1) is inhibitory to E2 protein or PMA/A23187 stimulation. The combination of E2 protein and PMA/A23187 appears to eliminate an inhibitory effect of the upstream region. However, E2 protein, like p40tax, mediates a positive response through CLE1 alone linked to the basic promoter sequence. The level of activation of the long control region (LCR) by E2 protein is unaffected by the number of CLE2/GC box sequences.(ABSTRACT TRUNCATED AT 250 WORDS)     

Disparate effects of interleukin 11 and thrombopoietin on megakaryocytopoiesis in vitro

The effects of interleukin-11 (IL-11) and thrombopoietin (TPO) on murine megakaryocytopoiesis were studied using a serum-free culture system. Acting alone, both IL-11 and TPO increased the number of acetylcholinesterase (AchE)(+)cells (megakaryocytes), the latter being more potent than the former. TPO, but not IL-11, increased the mean AchE activity per megakaryocyte (AchE activity/megakaryocyte). TPO increased both the number of megakaryocytes with high ploidy, and of those with low ploidy. In contrast, IL-11 increased only the number of megakaryocytes with high ploidy. The effect of TPO on megakaryocyte ploidy was stronger than that of IL-11. Both IL-11 and TPO increased the proportion of large megakaryocytes, but the latter was more potent than the former. While the stimulatory effects of IL-11 and TPO on the number of megakaryocytes were enhanced by IL-3 or stem cell factor (SCF), synergism of IL-11 or TPO with IL-3 or SCF in stimulating AchE activity/megakaryocyte was inconsistent. IL-11 and TPO stimulated the formation of colony-forming units of megakaryocyte in the presence of IL-3, but not alone, with similar maximum colony numbers for both cytokines. Our findings thus demonstrate that IL-11 principally stimulates megakaryocyte maturation rather than the proliferation of megakaryocytes, whereas TPO stimulates both.     

Initiation of lagging-strand synthesis for pBR322 plasmid DNA replication in vitro is dependent on primosomal protein i encoded by dnaT

The role of the primosome assembly and protein n' recognition site in replication of pBR322 plasmid was examined. The following evidence indicates that the primosome is involved in lagging-strand synthesis of pBR322 plasmid replication in vitro. Early replicative intermediates with newly synthesized leading strand, approximately 1 kilobase pair long, immediately downstream of the replication origin accumulate in products synthesized in extracts from a dnaT strain that lacks primosomal protein i or in wild-type extracts supplemented with anti-protein i antibody. These intermediates are converted efficiently into full-length DNA by addition of purified protein i. Consistent with the previously proposed role of the primosome (Arai, K. and Kornberg, A. (1981) Proc. Natl. Acad. Sci. U. S. A. 78, 69-73), an n' site on the lagging strand, but not on the leading strand, is required for efficient replication of the plasmid in vitro. Plasmids lacking an n' site on the lagging strand replicate only to a limited extent in vitro and early replicative intermediates carrying nascent leading strands are accumulated, although a portion of the intermediates complete replication to yield full-length DNA. The latter reaction is completely inhibited by addition of anti-protein i antibody. Insertion of the n' site of phage phi X174 into pBR322 plasmids lacking lagging-strand n' sites restores the replicative ability of the mutant plasmid comparable to that of the wild-type plasmid. These results indicate that protein i is essential for lagging-strand synthesis of pBR322 plasmid in vitro and that it may play an important role in the priming events as a part of either an n' site-dependent primosome or an n' site-independent, as yet unidentified, priming complex.     

Physiological concentration of atrial natriuretic peptide induces endothelial regeneration in vitro

Both nitric oxide (NO) and natriuretic peptides produce apoptosis of vascular smooth muscle cells. However, there is evidence that NO induces endothelial cell proliferation, which suggests that there is a difference in the response of endothelial cells to natriuretic peptides. The purpose of this study was to investigate the effect of atrial natriuretic peptide (ANP) on human endothelial cell survival. ANP within the physiological concentration (10(-11) mol/l) induced a 52% increase in the number of human coronary arterial endothelial cells and a 63% increase in human umbilical vein endothelial cells at a low concentration of serum. The increase in cell numbers was blocked by pretreatment with RP8-CPT-cGMP (RP8), a cGMP-dependent protein kinase inhibitor, with wortmannin, an Akt/PKB inhibitor, and with PD-98059, an ERK1/2 inhibitor. In a Transwell migration test, ANP also increased the cell migration, and RP8, wortmannin, and PD-98059 blocked this increase. A wound healing assay was performed to examine the effects of ANP on regeneration in vitro. ANP increased both cell numbers and migration, but the effects were blocked by the above three kinase inhibitors. ANP increased the expression of phospho-Akt and of phospho-ERK1/2 within 1.5 h. These results suggest that ANP can potentiate endothelial regeneration by cGMP-dependent protein kinase stimulation and subsequent Akt and ERK1/2 activations.     

Three-dimensional structure of gurmarin,a sweet taste-suppressing polypeptide

Summary The solution structure of gurmarin was studied by two-dimensional proton NMR spectroscopy at 600 MHz. Gurmarin, a 35-amino acid residue polypeptide recently discovered in an Indian-originated tree Gymnema sylvestre, selectively suppresses the neural responses of rat to sweet taste stimuli. Sequence-specific protons. The three-dimensional solution structure was determined by simulated-annealing calculations on the basis of 135 interproton distance constraints derived from NOEs, six distance constraints for three hydrogen bonds and 16 dihedral angle constraints derived from coupling constants. A total of 10 structures folded into a well-defined structure with a triple-stranded antiparallel -sheet. The average rmsd values between any two structures were 1.65±0.39 Å for the backbone atoms (N, C, C) and 2.95±0.27 Å for all heavy atoms. The positions of the three disulfide bridges, which could not be deterermined chemically, were estimated to be Cys³–Cys¹⁸, Cys¹⁰–Cys²³ and Cys¹⁷–Cys³³ on the basis of the NMR distance constraints. This disulfide bridge pattern in gurmarin turned out to be analogous to that in -conotoxin and Momordica charantia trypsin inhibitor-II, and the topology of folding was the same as that in -conotoxin.Abbreviations DQF-COSY double-quantum-filtered correlated spectroscopy - HOHAHA homonuclear Hartmann-Hahn spectroscopy - NOESY nuclear Overhauser enhancement spectroscopy - ppm parts per million; rmsd, root-mean-square deviation - TSP 3-(trimethylsilyl)-2,2,3,3-tetradeutero-propionate     

Physiological levels of insulin and IGF-1 synergistically enhance the differentiation of mesenteric adipocytes

Visceral adipose tissue, particularly mesenteric adipose tissue, is important in the pathogenesis of metabolic syndrome. Here, we present a physiologically relevant differentiation system of rat mesenteric-stromal vascular cells (mSVC) to mesenteric-visceral adipocytes (mVAC). We optimized the insulin concentration at levels comparable to those in vivo ( approximately 0.85 ng/ml) by including physiological concentrations of IGF-1. We found that the insulin-like growth factor (IGF-1) and insulin worked synergistically, since IGF-1 alone could induce CCAAT/enhancer binding protein alpha (C/EBPalpha) and adipocyte lipid binding protein (aP2) mRNA expression but not lipid droplet accumulation associated with maturation. Using real-time PCR analyses on 180 adipocyte-related genes, we identified a dramatic effect by IGF-1 plus insulin. We also demonstrated the state of insulin resistance at pathologically high insulin concentrations. This culture system will contribute to understanding the physiological differentiation process and the patho/physiology of mVAC.