Association of human neuroglobin with cystatin C, a cysteine proteinase inhibitor

Neuroglobin (Ngb) is a newly discovered globin that is expressed in vertebrate brain. It has been reported that Ngb levels increase in neurons in response to oxygen deprivation, and that Ngb protects neurons from hypoxia. However, the mechanism of this neuroprotection remains unclear. In the present study, we identified human cystatin C, a cysteine proteinase inhibitor, as an Ngb-binding protein by using a yeast two-hybrid system. Surface plasmon resonance experiments verified that Ngb binds to cystatin C dimers, not to the monomers. Because both intracellular cystatin C and the amyloidogenic variant of cystatin C form dimers, Ngb may modulate the intracellular transport (or secretion) of cystatin C to protect against neuronal death under conditions of oxidative stress and/or it may have a role in the development of neurodegenerative diseases.     

Stabilization of exocytosis by dynamic F-actin coating of zymogen granules in pancreatic acini

Reorganization of F-actin in the apical region of mouse pancreatic acinar cells during Ca(2+)-dependent exocytosis of zymogen granules was investigated by two-photon excitation microscopy with intact acini. Granules were rapidly coated with F-actin in response to either agonist stimulation or photolysis of a caged-Ca(2+) compound. Such F-actin coating occurred exclusively at the surface of granules undergoing exocytosis and was prevented either by latrunculin-A, which inhibits actin polymerization, or by Clostridium botulinum exoenzyme C3, which inhibits the small GTPase Rho. Latrunculin-A or exoenzyme C3 also triggered the formation of vacuoles in acinar cells, a characteristic of acute pancreatitis. Stimulation of acini with high concentrations of cholecystokinin, which cause acute pancreatitis in mice, also impaired the F-actin coating of granules and induced vacuole formation. Latrunculin-A reduced the latency to exocytosis but did not affect the total number of exocytic events, suggesting that F-actin slows and further stabilizes exocytosis by facilitating F-actin coating. Rho-dependent F-actin coating of granule membranes thus stabilizes exocytic structures and is necessary for physiological progression of sequetial compound exocytosis in the exocrine pancreas and for prevention of acute pancreatitis.     

Monitoring for dynamic biological processing by intramolecular bioluminescence resonance energy transfer system using secreted luciferase

Proteolytic processing plays crucial roles in physiological and pathophysiological cellular functions such as peptide generation, cell cycle, and apoptosis. We developed a novel biophysical bioluminescence resonance energy transfer (BRET) system between a secreted Vargula luciferase (Vluc) and an enhanced yellow fluorescent protein (EYFP) for visualization of cell biological processes. The bioluminescence spectrum of the fusion protein (Vluc-EYFP) is bimodal (lambdamax = 460 nm (Vluc) and 525nm (EYFP)), indicating that the excited-state energy of Vluc transfers to EYFP (in short, BRET). The BRET signal can be measured in the culture medium and pursue quantitative production of two neuropeptides, nocistatin (NST) and nociceptin/orphanin FQ (N/OFQ) in living cells. NST and N/OFQ are located in tandem on the same precursor, but NST exhibits antagonistic action against N/OFQ-induced central functions. Insertion of a portion of the NST-N/OFQ precursor (Glu-Gln-Lys-Gln-Leu-Gln-Lys-Arg-Phe-Gly-Gly-Phe-Tyr-Gly) in Vluc-EYFP makes the fusion protein cleavable at Lys-Arg in NG108-15 cells, and proprotein convertase 1 enhances this digestion. The change in BRET signals quantifies the processing of the fusion protein. Our novel intramolecular BRET system using a secreted luciferase is useful for investigating peptide processing in living cells.     

ADAMs, a disintegrin and metalloproteinases, mediate shedding of oxytocinase

Placental leucine aminopeptidase (P-LAP), a type-II transmembrane protease responsible for oxytocin degradation during pregnancy, is converted to a soluble form through proteolytic cleavage. The goal of this study was to determine the nature of the P-LAP secretase activity. The hydroxamic acid-based metalloprotease inhibitors GM6001 and ONO-4817 as well as the TNF-alpha protease inhibitor-2 (TAPI-2) reduced P-LAP release, while tissue inhibitors of metalloproteinase (TIMP)-1 and TIMP-2, which are matrix metalloproteinase inhibitors, had no effect on P-LAP release in Chinese hamster ovary (CHO) cells stably overexpressing P-LAP, thus indicating possible involvement of ADAM (a disintegrin and metalloproteinase) members in P-LAP shedding. Furthermore, overexpression of ADAM9 and ADAM12 increased P-LAP release in P-LAP-CHO transfectants. Immunohistochemical analysis in human placenta demonstrated strong expression of ADAM12 in syncytiotrophoblasts, while little expression of ADAM9 was detected throughout the placenta. Our results suggest ADAM members, at least including ADAM12, are involved in P-LAP shedding in human placenta.     

A subpopulation of bone marrow cells depleted by a novel antibody, anti-Liv8, is useful for cell therapy to repair damaged liver

We previously reported a new in vivo model named as "GFP/CCl(4) model" for monitoring the transdifferentiation of green fluorescent protein (GFP) positive bone marrow cell (BMC) into albumin-positive hepatocyte under the specific "niche" made by CCl(4) induced persistent liver damage, but the subpopulation which BMCs transdifferentiate into hepatocytes remains unknown. Here we developed a new monoclonal antibody, anti-Liv8, using mouse E 11.5 fetal liver as an antigen. Anti-Liv8 recognized both hematopoietic progenitor cells in fetal liver at E 11.5 and CD45-positive hematopoietic cells in adult bone marrow. We separated Liv8-positive and Liv8-negative cells and then transplanted these cells into a continuous liver damaged model. At 4 weeks after BMC transplantation, more efficient repopulation and transdifferentiation of BMC into hepatocytes were seen with Liv8-negative cells. These findings suggest that the subpopulation of Liv8-negative cells includes useful cells to perform cell therapy on repair damaged liver.     

Ginkgo biloba extract modifies hypoglycemic action of tolbutamide via hepatic cytochrome P450 mediated mechanism in aged rats

We examined hepatic cytochrome P450 (CYP)-mediated interactions between Ginkgo biloba extract (GBE) and tolbutamide, an oral anti-diabetic agent, in aged and young rats. Tolbutamide was orally given to rats with or without GBE treatment, and time-dependent changes in blood glucose were monitored. The basal activity of six CYP subtypes in liver was lower in the aged rats than in the young rats, while the inductions of these enzymes by 5 day pretreatment of 0.1% GBE diet were more in the aged rats. Further, the pretreatment of GBE significantly attenuated the hypoglycemic action of tolbutamide in the aged rats, corresponding well to the enhanced activity of (S)-warfarin 7-hydroxylase, which is responsible for CYP2C9 subtype, a major isoform metabolizing tolbutamide. In contrast, the simultaneous administration of GBE with tolbutamide potentiated the hypoglycemic action of this drug. The in vitro experiments revealed that GBE competitively inhibited the metabolism of tolbutamide by (S)-warfarin 7-hydroxylase in the rat liver microsomes. In the young rats, the 5 day pretreatment with GBE significantly attenuated the hypoglycemic action of tolbutamide, but a simultaneous treatment had little influence on the tolbutamide effect. In conclusion, the present study has shown that the simultaneous and continuous intake of GBE significantly affects the hypoglycemic action of tolbutamide, possibly via a hepatic CYP enzyme-mediated mechanism, particularly in the aged rats. Therefore, it is anticipated that the intake of GBE as a dietary supplement with therapeutic drugs should be cautious, particularly in elderly people.     

HuC:Kaede, a useful tool to label neural morphologies in networks in vivo

A simple and efficient procedure for labeling neurons is a prerequisite for investigating the development of neural networks in zebrafish. To label neurons we used Kaede, a fluorescent protein with a photoconversion property allowing conversion from green to red fluorescence following irradiation with UV or violet light. We established a zebrafish stable transgenic line, Tg(HuC:Kaede), expressing Kaede in neurons under the control of the HuC promoter. This transgenic line was used to label a small number of neurons in the trigeminal ganglion. Also, using embryos injected with the transgene, we labeled peripheral axon arbors of a Rohon-Beard neuron at 4 days postfertilization and observed the dendrite development of a tectal neuron for 3 days. These data indicate that Kaede is a useful tool to selectively label neural networks in zebrafish.     

β-Naphthoflavone analogs as potent and soluble aryl hydrocarbon receptor agonists: Improvement of solubility by disruption of molecular planarity

The physiological role of aryl hydrocarbon receptor (AhR) is not yet fully understood, and investigation is hampered by the limited solubility of reported AhR ligands in aqueous media. To achieve improved solubility, we focused on our previous finding that planarity-disruption of molecules leads to less efficient crystal packing and greater aqueous solubility. Here, we describe chemical modification of an AhR agonist, β-naphthoflavone, focusing on planarity-disruption. As expected, introduction of substituents at the ortho-positions of the phenyl group resulted in greater solubility. Among the compounds prepared, the fluoro analog showed more potent AhR agonistic activity and greater solubility than did β-naphthoflavone. Our results indicate that this strategy to improve aqueous solubility, that is, introduction of substituent(s) that disrupt planarity, may be generally applicable to bicyclic molecules.