cDNA cloning and nuclear localization of the circadian neuropeptide designated as pigment-dispersing factor PDF in the cricket Gryllus bimaculatus

Pigment-dispersing factor (PDF) was recently reported to be a principal circadian neuromodulator involved in transmitting circadian rhythms of daily locomotion in insects. In Drosophila, PDF functions in some of the neurons expressing the clock genes period, timeless, Clock, and cycle, and those clock genes in turn regulate pdf gene expression. In the present study, we cloned a cDNA encoding PDF in the brain of a nocturnal insect, the cricket Gryllus bimaculatus, and found that an isolated clone (310 bp) codes for an extraordinarily short precursor protein with no definite signal sequence, but a nuclear localization signal (NLS)-like sequence instead. The cricket PDF exhibits high sequence identity (78-94%) and similarity (89-100%) to insect PDFs and also to crustacean beta-PDH peptides. In the optic lobes of G. bimaculatus there are PDF-immunoreactive neurons in both the medulla and lamina neuropiles. Among the strongly immunoreactive lamina PDF neurons, on electron microscopy we identified cells exhibiting distinct staining that is not only cytoplasmic but also nuclear. When GFP-fused PDF precursor proteins were expressed in COS-7 cells, distinct translocation of the fusion protein into the nucleus was observed. This is the first finding of PDF peptide in the nucleus, which suggests a fundamental role of PDF peptide per se in the circadian clock system.     

Development of a scale-up strategy for Chinese hamster ovary cell culture processes using the kLa ratio as a direct indicator of gas stripping conditions

Herein, we described a scale-up strategy focused on the dissolved carbon dioxide concentration (dCO₂) during fed-batch cultivation of Chinese hamster ovary cells. A fed-batch culture process for a 2000-L scale stainless steel (SS) bioreactor was scaled-up from similarly shaped 200-L scale bioreactors based on power input per unit volume (P/V). However, during the 2000-L fed-batch culture, the dCO₂ was higher compared with the 200-L scale bioreactor. Therefore, we developed an alternative approach by evaluating the k_La values of O₂ (k_La[O₂]) and CO₂ [k_La(CO₂)] in the SS bioreactors as a scale-up factor for dCO₂ reduction. The k_La ratios [k_La(CO₂)/k_La(O₂)] were different between the 200-L and 2000-L bioreactors under the same P/V condition. When the agitation conditions were changed, the k_La ratio of the 2000-L scale bioreactor became similar and the P/V value become smaller compared with those of the 200-L SS bioreactor. The dCO₂ trends in fed-batch cultures performed in 2000-L scale bioreactors under the modified agitation conditions were similar to the control. This k_La ratio method was used for process development in single-use bioreactors (SUBs) with shapes different from those of the SS bioreactor. The k_La ratios for the SUBs were evaluated and conditions that provided k_La ratios similar to the 200-L scale SS bioreactors were determined. The cell culture performance and product quality at the end of the cultivation process were comparable for all tested SUBs. Therefore, we concluded that the k_La ratio is a powerful scale-up factor useful to control dCO₂ during fed-batch cultures.     

Stereoselective Synthesis of erythro-Serricornin, (4R, 6R, 7S)-, and (4S, 6R, 7S)-4,6-Dimethyl-7-hydroxynonan-3-one,Stereoisomers of the Sex Pheromone of Cigarette Beetle

A stereoselective synthesis of erythro-serricornin [(4RS,6R,7S)-4,6-dimethyl-7-hydroxynonan-3-one] was completed starting from l-(+)-tartaric acid. The relative configuration of C(6)-methyl and C(7)-hydroxyl groups in naturally occurring serricornin was threo.     

A circadian neuropeptide,pigment-dispersing factor-PDF,in the last-summer cicada Meimuna opalifera: cDNA cloning and immunocytochemistry

Pigment-dispersing factor (PDF), an 18-amino acid neuropeptide, is a principal circadian neuromodulator functioning downstream of the insect brain's circadian clock, modulating daily rhythms of locomotor activity. Recently, we found that PDF precursors of the cricket Gryllus bimaculatus comprise a nuclear localization signal (NLS). Moreover, the nuclear localization of PDF immunoreactivity and the translocation of GFP-fused PDF precursor into the nucleus have both been demonstrated. These suggest a fundamental role for PDF peptide in the circadian clock system within the nucleus, in addition to its role in downstream neural events. In the present study, we carried out the cDNA cloning of PDF from adult brains of the last-summer cicada Meimuna opalifera, and found that an isolated clone (545 bp) encodes an ordinary PDF precursor protein. PDF peptide itself shows a high sequence identity (78-94%) and similarity (89-100%) to insect PDFs and also to the crustacean beta-PDH peptides. The computer-assisted sequence analysis of PDF precursor revealed a possible translocation into the nucleus, despite the lack of a definite NLS-like sequence. Using immunocytochemistry, the optic lobes of M. opalifera revealed PDF-immunoreactive neurons in both the medulla and lamina neuropiles. All these PDF cells exhibited prominent immunolabeling of both their perikarya and axons, but not their nuclei. Our results provide the first structural and immunocytochemical identification of PDF neurons in Hemiptera.     

Characterization of the active site and a unique uncompetitive inhibitor of the PPM1-type protein phosphatase PPM1D

Protein phosphatase magnesium-dependent 1, delta (PPM1D) is a member of the PPM1 (formerly PP2C) protein phosphatase family, and is induced in response to DNA damage. The overexpression of PPM1D is thought to exert oncogenic effects through the inhibition of tumor suppressor proteins. PPM1D shows high selectivity for the primary sequence in its substrates when compared with other phosphatases, but the mechanisms underlying substrate recognition by this enzyme is not clearly known. In our present study we wished to identify the active center and further elucidate the substrate preference of PPM1D, and to this end performed sequence alignments among the human PPM1 type phosphatases. The results of this analysis clearly showed that the putative active site residues of PPM1D are highly conserved among the PPM1 family members. Phosphatase analyses using PPM1D mutants further identified the metal-chelating residues and a phosphate binding residue. In kinetic analyses using a series of phosphorylated p53 peptide analogs, the introduction of acidic residues into the region flanking the sites of dephosphorylation enhanced their affinity with PPM1D. Homology modeling of PPM1D also revealed that PPM1D contains two characteristic loops, a Pro-residue rich loop on the opposite side of the active site and a basic-residue rich loop in the vicinity of the active site in the catalytic domain. Interestingly, nonhydrolyzable AP4-3E peptides derived from the acidic p53 peptide analogs very effectively blocked PPM1D activity in an uncompetitive manner, suggesting that AP4-3E peptides may be useful lead compounds in the development of novel inhibitors of PPM1D.     

Alterations in growth requirements of kidney epithelial cells in defined medium associated with malignant transformation

The possibility has been investigated that (1) the supplements required for the growth of the Madin Darby Canine Kidney (MDCK) cell line in serum-free Medium K-l are indeed requirements for the growth of normal kidney cells in vitro, and (2) that alterations in these growth requirements are associated with malignant transformation. Consistent with the hypothesis that MDCK cells resemble normal kidney cells in culture, primary cultures of baby mouse kidney epithelial cells grow in Medium K-l and respond to the 5 components in the-medium. The growth properties of Moloney sarcoma virus (MSV)-transformed MDCK cells in defined media have been examined. Unlike MDCK cells, MSV-transformed MDCK cells form tumors in adult nude mice. Although they still respond to the 5 factors in Medium K-l, the optimal dosage for insulin is lower for the MSV transformants than for MDCK cells. The MSV transformants also have an additional requirement for growth in Medium K-l – fibronectin. Variants of MDCK cells have been isolated that have lost the PGE₁ requirement for growth in defined medium. These variant cells have acquired (1) the ability to form tumors in adult nude mice and (2) an alteration affecting cAMP metabolism, in addition to PGE₁ independence.     

A structural study of calcium-binding equine lysozyme by two-dimensional 1H-NMR.

Since 1H-NMR spectra of the calcium bound form (holo) and the calcium free form (apo) of equine lysozyme have an overall similarity, the folded structure of apo equine lysozyme seems to be similar to the holo structure at 25 degrees C and pH 7.0, even at low ionic strengths except for subtle conformational change. However, calcium titration experiments showed that a number of resonances change by a slow exchange process. The changes saturated at one calcium ion per one lysozyme molecule, and no more change was observed by further addition of calcium ions. This shows that just one calcium ion binds to equine lysozyme. To make assignments for these changed proton resonances, two-dimensional 1H-NMR studies, correlated spectroscopy (COSY), two-dimensional homonuclear Hartmann-Hahn spectroscopy (HOHAHA) and nuclear Overhauser effect spectroscopy (NOESY) were carried out. A structural model of equine lysozyme based on the crystal structure of human lysozyme was estimated and used to assign some resonances in the aromatic and beta-sheet regions. It was possible to use some proton signals as a probe to determine the specific conformational change induced by calcium ions. The calcium binding constant KCa was estimated from calcium titration experiments in which changes in the proton signal were monitored. The log KCa value was found to be on the order of 6-7, which is in agreement with the calcium binding constant determined by fluorescence probes. This means that the protons are affected by specific calcium binding.     

Effect of a conjugated quercetin metabolite,quercetin 3-glucuronide,on lipid hydroperoxide-dependent formation of reactive oxygen species in differentiated PC-12 cells

To assess the efficacy of conjugated quercetin metabolites as attenuators for oxidative stress in the central nervous system, we measured the 13-hydroperoxyoctadecadienoic acid (13-HPODE)-dependent formation of reactive oxygen species (ROS) in pheochromocytoma PC-12 cells in the presence of quercetin 3-O-β-glucuronide (Q3GA) and related compounds. A 2′,7′-dichlorofluorescin (DCFH) assay showed that Q3GA significantly suppressed the formation of ROS, when it was coincubated with 13-HPODE (coincubation system). However, it was less effective than quercetin aglycon in the concentration range from 0.5 to 10 μM. In an experiment in which the cells were incubated with the test compounds for 24 h before being exposed to 13-HPODE, Q3GA was also effective in suppressing the formation of ROS in spite that little Q3GA was taken up into the cells. These results suggest that antioxidative metabolites of quercetin are capable of protecting nerve cells from attack of lipid hydroperoxides.