A highly sensitive LC-ESI-MS/MS method for the quantification of cholesterol ozonolysis products secosterol-A and secosterol-B after derivatization with 2-hydrazino-1-methylpyridine

Cholesterol ozonolysis products, 3β-hydroxy-5-oxo-5,6-secocholestan-6-al (secosterol-A) and its aldolization product 3β-hydroxy-5β-hydroxy-B-norcholestane-6β-carboxaldehyde (secosterol-B) have been found in atherosclerosis plaques and the brain tissues of Alzheimer's disease patients, implicating them in the pathogenesis of cardiovascular and neurodegenerative diseases. We have recently reported that when cholesterol is oxidized with an ozone-like oxidant generated by activated mouse neutrophils, secosterol-A is generated which is then converted to secosterol-B by an aldol reaction. To investigate further pathophysiological roles of secosterols, we have developed a highly sensitive method to detect secosterol-A and -B as derivatives with 2-hydrazino-1-methylpyridine (HMP) by LC-ESI-MS/MS. The limits of detection for the HMP derivatives of secosterol-A and secosterol-B were 0.05 and 0.01fmol, respectively, which were approximately 400 and 2000 times better than those for underivatized secosterol-A and -B. We also developed a highly reproducible and accurate method to extract, purify and derivatize secosterol in small volumes of biological specimens. Using this method, we determined the levels of secosterol-A and -B as 1.4 ± 0.7 and 4.3 ± 0.8 nM, respectively, in the plasma of normal C57BL/6 mice, and in the range of 10.4 ± 16.3 to 40.7 ± 20.1 pmol/g and 110.9 ± 10.6 to 161.5 ± 56.3 pmol/g, respectively, in the brain, liver and lung tissues.     

Crystal structure of basic 7S globulin, a xyloglucan-specific endo-β-1,4-glucanase inhibitor protein-like protein from soybean lacking inhibitory activity against endo-β-glucanase

β-Linked glucans such as cellulose and xyloglucan are important components of the cell walls of most dicotyledonous plants. These β-linked glucans are constantly exposed to degradation by various endo-β-glucanases from pathogenic bacteria and fungi. To protect the cell wall from degradation by such enzymes, plants secrete proteinaceous endo-β-glucanases inhibitors, such as xyloglucan-specific endo-β-1,4-glucanase inhibitor protein (XEGIP) in tomato. XEGIPs typically inhibit xyloglucanase, a member of the glycoside hydrolase (GH)12 family. XEGIPs are also found in legumes, including soybean and lupin. To date, tomato XEGIP has been well studied, whereas XEGIPs from legumes are less well understood. Here, we determined the crystal structure of basic 7S globulin (Bg7S), a XEGIP from soybean, which represents the first three-dimensional structure of XEGIP. Bg7S formed a tetramer with pseudo-222 symmetry. Analytical centrifugation and size exclusion chromatography experiments revealed that the assembly of Bg7S in solution depended on pH. The structure of Bg7S was similar to that of a xylanase inhibitor protein from wheat (Tritinum aestivum xylanase inhibitor) that inhibits GH11 xylanase. Surprisingly, Bg7S lacked inhibitory activity against not only GH11 but also GH12 enzymes. In addition, we found that XEGIPs from azukibean, yardlongbean and mungbean also had no impact on the activity of either GH12 or GH11 enzymes, indicating that legume XEGIPs generally do not inhibit these enzymes. We reveal the structural basis of why legume XEGIPs lack this inhibitory activity. This study will provide significant clues for understanding the physiological role of Bg7S.     

Diurnal dynamics of S-phase entry of germ cells in the secondary testis of the bambooleaf wrasse (Pseudolabrus sieboldi)

The diversity of reproductive strategies found in fish is attributed to the adaptation of gametogenesis to different habitats. To date, however, information about the dynamics of male gametogenesis and its molecular mechanisms of control by the brain-pituitary-gonadal (BPG) axis, a well-known facet of the endocrine system in vertebrates, is not sufficient to explain the variation in spawning and regulatory mechanisms among species. The bambooleaf wrasse (Pseudolabrus sieboldi) is a protogynous hermaphrodite fish that shows clear diurnal fluctuations in gonadotropin gene expression and serum sex steroid levels associated with spawning. In this study, morphometrical and histological analyses were performed to determine the number of spermatogonial generations in the testis of the sex-changed male (secondary testis). In addition, the diurnal dynamics of S-phase entry of germ cells was explored by measuring the frequency of BrdU-incorporating germ cells at different times of day. We found that the bambooleaf wrasse spermatozoa were generated through nine spermatogonial generations, followed by meiotic divisions accompanied by loss of some spermatocytes and spermatids through apoptosis. BrdU analyses revealed a high frequency of entry into S-phase of undifferentiated type A spermatogonia at 03:00?hr. On the other hand, the frequency of spermatocytes at S-phase of the cell cycle decreased during 00:00-09:00?hr. This study demonstrates for the first time the daily fluctuations of S-phase entry of male germ cells in fish. These results will provide a useful foundation for understanding the roles of endocrinological and cytological regulation of fish spermatogenesis.     

Suppression and regression of choroidal neovascularization in mice by a novel CCR2 antagonist, INCB3344

Purpose

To investigate the effect of an intravitreally administered CCR2 antagonist, INCB3344, on a mouse model of choroidal neovascularization (CNV).

Methods

CNV was induced by laser photocoagulation on Day 0 in wild type mice. INCB3344 or vehicle was administered intravitreally immediately after laser application. On Day 14, CNV areas were measured on retinal pigment epithelium (RPE)-choroid flat mounts and histopathologic examination was performed on 7 µm-thick sections. Macrophage infiltration was evaluated by immunohistochemistry on RPE-choroid flat mounts and quantified by flow cytometry on Day 3. Expression of vascular endothelial growth factor (VEGF) protein in RPE-choroid tissue was examined by immunohistochemistry and ELISA, VEGF mRNA in sorted macrophages in RPE-choroid tissue was examine by real-time PCR and expression of phosphorylated extracellular signal-regulated kinase (p-ERK 1/2) in RPE-choroid tissue was measured by Western blot analysis on Day 3. We also evaluated the efficacy of intravitreal INCB3344 to spontaneous CNV detected in Cu, Zn-superoxide dismutase (SOD1) deficient mice. Changes in CNV size were assessed between pre- and 1week post-INCB3344 or vehicle administration in fundus photography and fluorescence angiography (FA).

Results

The mean CNV area in INCB3344-treated mice decreased by 42.4% compared with the vehicle-treated control mice (p<0.001). INCB3344 treatment significantly inhibited macrophage infiltration into the laser-irradiated area (p<0.001), and suppressed the expression of VEGF protein (p = 0.012), VEGF mRNA in infiltrating macrophages (p<0.001) and the phosphorylation of ERK1/2 (p<0.001). The area of spontaneous CNV in Sod1 ^−/− mice regressed by 70.35% in INCB3344-treated animals while no change was detected in vehicle-treated control mice (p<0.001).

Conclusions

INCB3344 both inhibits newly forming CNV and regresses established CNV. Controlling inflammation by suppressing macrophage infiltration and angiogenic ability via the CCR-2/MCP-1 signal may be a useful therapeutic strategy for treating CNV associated with age-related macular degeneration.     

Dimerization and proper degradation of BmNPV IE2 are required for efficient virus growth in larvae of Bombyx mori (Lepidoptera: Bombycidae)

The baculovirus ie2 gene is one of the immediate early genes, and its product is known to transactivate viral promoters. However, the roles of Bombyx mori nucleopolyhedrovirus (BmNPV) ie2 in insect larvae are poorly understood. Here we investigated the functions of BmNPV IE2 in cultured cells and in insect larvae using two mutant viruses, BmIE2D and BmIE2CS. BmIE2D lacks the IE2 C-terminal coiled-coil domain that is required for IE2 dimerization. The other mutant BmIE2CS expresses an E3 ligase activity-deficient IE2 derivative, which is degraded more slowly compared with wild-type IE2. We found that ie2 mutations had little effect on BmNPV infection in cultured cells, whereas budded virus and occlusion body production was significantly reduced in the hemolymph of B. mori larvae infected with ie2 mutants. These results indicate that both dimerization and proper degradation of BmNPV IE2 are crucial steps for efficient virus growth in B. mori larvae, but not in cultured cells. Oral infection assays also revealed that the infectivity of the occluded form of ie2 mutants was normal in B. mori larvae, which is inconsistent with the results reported from ie2 mutants of Autographa californica NPV. This suggests that loss of IE2 function causes virus-specific effects in host insects.     

Extracellular Signal-regulated Kinase and Glycogen Synthase Kinase 3β Regulate Gephyrin Postsynaptic Aggregation and GABAergic Synaptic Function in a Calpain-dependent Mechanism

Molecular mechanisms of plasticity at GABAergic synapses are currently poorly understood. To identify signaling cascades that converge onto GABAergic postsynaptic density proteins, we performed MS analysis using gephyrin isolated from rat brain and identified multiple novel phosphorylation and acetylation residues on gephyrin. Here, we report the characterization of one of these phosphoresidues, Ser-268, which when dephosphorylated leads to the formation of larger postsynaptic scaffolds. Using a combination of mutagenesis, pharmacological treatment, and biochemical assays, we identify ERK as the kinase phosphorylating Ser-268 and describe a functional interaction between residues Ser-268 and Ser-270. We further demonstrate that alterations in gephyrin clustering via ERK modulation are reflected by amplitude and frequency changes in miniature GABAergic postsynaptic currents. We unravel novel mechanisms for activity- and ERK-dependent calpain action on gephyrin, which are likely relevant in the context of cellular signaling affecting GABAergic transmission and homeostatic synaptic plasticity in pathology.     

ATM Mediates pRB Function To Control DNMT1 Protein Stability and DNA Methylation

The retinoblastoma tumor suppressor gene (RB) product has been implicated in epigenetic control of gene expression owing to its ability to physically bind to many chromatin modifiers. However, the biological and clinical significance of this activity was not well elucidated. To address this, we performed genetic and epigenetic analyses in an Rb-deficient mouse thyroid C cell tumor model. Here we report that the genetic interaction of Rb and ATM regulates DNMT1 protein stability and hence controls the DNA methylation status in the promoters of at least the Ink4a, Shc2, FoxO6, and Noggin genes. Furthermore, we demonstrate that inactivation of pRB promotes Tip60 (acetyltransferase)-dependent ATM activation; allows activated ATM to physically bind to DNMT1, forming a complex with Tip60 and UHRF1 (E3 ligase); and consequently accelerates DNMT1 ubiquitination driven by Tip60-dependent acetylation. Our results indicate that inactivation of the pRB pathway in coordination with aberration in the DNA damage response deregulates DNMT1 stability, leading to an abnormal DNA methylation pattern and malignant progression.