Nav1.7-Ca2+ influx-induced increased phosphorylations of extracellular signal-regulated kinase (ERK) and p38 attenuate tau phosphorylation via glycogen synthase kinase-3beta: priming of Nav1.7 gating by ERK and p38

In cultured bovine adrenal chromaffin cells expressing Nav1.7 sodium channel isoform, we previously showed that veratridine-induced Na+ influx via Nav1.7 and the subsequent Ca2+ influx via voltage-dependent calcium channels activated protein kinase C-alpha and Akt, which converged on increasing inhibitory Ser9-phosphorylation of glycogen synthase kinase-3beta, decreasing constitutive Ser396-phosphorylation of tau. Here, veratridine increased constitutive Tyr204-phosphorylation of extracellular signal-regulated kinase-1/-2 (ERK1/ERK2) and constitutive Thr180/Tyr182-dual phosphorylation of p38 by approximately 118% (EC50=2.8 microM). Veratridine-induced increased phosphorylation levels of ERK1/ERK2 and p38 were abolished by tetrodotoxin, extracellular Ca2+ removal, or Gö6976 [12-(2-cyanoethyl)-6,7,12,13-tetrahydro-13-methyl-5-oxo-5H-indolo(2,3-a)pyrrolo(3,4-c)-carbazole;Go6976] (protein kinase C-alpha inhibitor). PD98059 (2'-amino-3'-methoxyflavone) (ERK1/ERK2 inhibitor) or SB203580 [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole] (p38 inhibitor) attenuated veratridine-induced increased phosphorylation of glycogen synthase kinase-3beta and decreased phosphorylation of tau by approximately 54% and approximately 56%, as partial blockade by Gö6976. Additionally, basal constitutive phosphorylation levels of ERK1/ERK2 and p38 were decreased by PD98059 or SB203580, but not by SB216763 [3-(2,4-dichlorophenyl)-4-(1-methyl-1H-indolo-3-yl)-1H-pyrrole-2,5-dione] (glycogen synthase kinase-3beta inhibitor) or extracellular Ca2+ removal. In this condition, PD98059 or SB203580 (but not SB216763 or extracellular Ca2+ removal) inhibited veratridine-induced 22Na+ influx and 45Ca2+ influx, without changing nicotine-induced 22Na+ influx via nicotinic receptor-associated cation channels and nicotine-induced 45Ca2+ influx via voltage-dependent calcium channels. These results suggest that Nav1.7-Ca2+ influx-protein kinase C-alpha pathway activated ERK1/ERK2 and p38, which increased phosphorylation of glycogen synthase kinase-3beta, decreasing tau phosphorylation. In veratridine-nontreated cells, basal constitutive activities of ERK1/ERK2 and p38 primed Nav1.7 to increase 22Na+ influx.

Gene up-regulation in response to predator kairomones in the water flea, Daphnia pulex

BACKGROUND

Numerous cases of predator-induced polyphenisms, in which alternate phenotypes are produced in response to extrinsic stimuli, have been reported in aquatic taxa to date. The genus Daphnia (Branchiopoda, Cladocera) provides a model experimental system for the study of the developmental mechanisms and evolutionary processes associated with predator-induced polyphenisms. In D. pulex, juveniles form neckteeth in response to predatory kairomones released by Chaoborus larvae (Insecta, Diptera).

RESULTS

Previous studies suggest that the timing of the sensitivity to kairomones in D. pulex can generally be divided into the embryonic and postembryonic developmental periods. We therefore examined which of the genes in the embryonic and first-instar juvenile stages exhibit different expression levels in the presence or absence of predator kairomones. Employing a candidate gene approach and identifying differentially-expressed genes revealed that the morphogenetic factors, Hox3, extradenticle and escargot, were up-regulated by kairomones in the postembryonic stage and may potentially be responsible for defense morph formation. In addition, the juvenile hormone pathway genes, JHAMT and Met, and the insulin signaling pathway genes, InR and IRS-1, were up-regulated in the first-instar stage. It is well known that these hormonal pathways are involved in physiological regulation following morphogenesis in many insect species. During the embryonic stage when morphotypes were determined, one of the novel genes identified by differential display was up-regulated, suggesting that this gene may be related to morphotype determination. Biological functions of the up-regulated genes are discussed in the context of defense morph formation.

CONCLUSIONS

It is suggested that, following the reception of kairomone signals, the identified genes are involved in a series of defensive phenotypic alterations and the production of a defensive phenotype.

Ergatoid queen development in the ant Myrmecina nipponica: modular and heterochronic regulation of caste differentiation

Caste polyphenism in social insects provides us with excellent opportunities to examine the plasticity and robustness underlying developmental pathways. Several ant species have evolved unusual castes showing intermediate morphologies between alate queens and wingless workers. In some low-temperature habitats, the ant Myrmecina nipponica produces such intermediate reproductives (i.e. ergatoids), which can mate and store sperm but cannot fly. To gain insight into the developmental and evolutionary aspects associated with ergatoid production, we conducted morphological and histological examinations of the post-embryonic development of compound eyes, gonads and wings during the process of caste differentiation. In compound eyes, both the queen-worker and ergatoid-worker differences were already recognized at the third larval instar. In gonads, queen-worker differentiation began at the larval stage, and ergatoid-worker differentiation began between the prepupal and pupal stages. Wing development in ergatoids was generally similar to that in workers throughout post-embryonic development. Our results showed that the developmental rate and timing of differentiation in body parts differed among castes and among body parts. These differences suggest that the rearrangement of modular body parts by heterochronic developmental regulation is responsible for the origination of novel castes, which are considered to be adaptations to specific ecological niches.

Ovarian development and insulin-signaling pathways during reproductive differentiation in the queenless ponerine ant Diacamma sp

In many social hymenopteran species, workers possess functional ovaries that are physiologically inactive in the presence of queens. We investigated the ovarian regulatory mechanism of workers and reproductives in a queenless ponerine ant, Diacamma sp., using histological and molecular techniques. In this ant, clear reproductive differentiation occurs via a highly sophisticated dominance behavioral interaction called "gemmae mutilation". This clear and rapid bifurcation of reproductive physiology allows us to elucidate the detailed ovarian differentiation process. Histological characteristics of functional ovaries (fusomes and ring canals) were found in both workers and reproductives, suggesting that early oogenesis is not blocked in workers. Since insulin/insulin-like growth factor signaling (IIS) is known to control insect reproduction, orthologs of 2 positive IIS regulators, insulin receptor and serine-threonine kinase Akt (protein kinase B), were cloned in Diacamma (DiaInR, DiaAkt); their expression patterns during reproductive differentiation were examined by real-time quantitative polymerase chain reaction; DiaInR and DiaAkt were strongly expressed in the gasters of reproductives. Whole-mount in situ hybridization of ovaries indicated that DiaInR and DiaAkt were expressed in nurse cells, oocytes, and upper germarial regions of reproductives but not of workers. Our data suggest that the IIS pathway accounts for reproductive differentiation in late oogenesis.

Mathematical model for empirically optimizing large scale production of soluble protein domains

BACKGROUND

Efficient dissection of large proteins into their structural domains is critical for high throughput proteome analysis. So far, no study has focused on mathematically modeling a protein dissection protocol in terms of a production system. Here, we report a mathematical model for empirically optimizing the cost of large-scale domain production in proteomics research.

RESULTS

The model computes the expected number of successfully producing soluble domains, using a conditional probability between domain and boundary identification. Typical values for the model's parameters were estimated using the experimental results for identifying soluble domains from the 2,032 Kazusa HUGE protein sequences. Among the 215 fragments corresponding to the 24 domains that were expressed correctly, 111, corresponding to 18 domains, were soluble. Our model indicates that, under the conditions used in our pilot experiment, the probability of correctly predicting the existence of a domain was 81% (175/215) and that of predicting its boundary was 63% (111/175). Under these conditions, the most cost/effort-effective production of soluble domains was to prepare one to seven fragments per predicted domain.

CONCLUSIONS

Our mathematical modeling of protein dissection protocols indicates that the optimum number of fragments tested per domain is actually much smaller than expected a priori. The application range of our model is not limited to protein dissection, and it can be utilized for designing various large-scale mutational analyses or screening libraries.

Homologous posttranscriptional regulation of insulin-like growth factor-I receptor level via glycogen synthase kinase-3beta and mammalian target of rapamycin in adrenal chromaffin cells: effect on tau phosphorylation

In cultured bovine adrenal chromaffin cells, approximately 24 h-treatment with insulin-like growth factor-I (IGF-I) decreased cell surface (125)I-IGF-I binding capacity and IGF-I receptor protein level by approximately 64% (EC(50) = 5.0 nM; t(1/2) = approximately 7 h). IGF-I-induced IGF-I receptor decrease was abolished by LY294002 (phosphoinositide 3-kinase inhibitor) and partially attenuated by rapamycin (an inhibitor of mammalian target of rapamycin [mTOR]). SB216763 (an inhibitor of glycogen synthase kinase-3 [GSK-3]) down-regulated IGF-I receptor, which was further decreased by IGF-I. IGF-I increased inhibitory Ser(9)-phosphorylation of GSK-3beta and stimulatory Ser(2448)-phosphorylation of mTOR. l-leucine increased phosphorylation of mTOR (but not GSK-3beta), and down-regulated IGF-I receptor, both events being abolished by rapamycin. IGF-I-induced IGF-I receptor decrease was not prevented by proteolysis inhibitors. Pulse-label with [(35)S]methionine/cysteine followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that SB216763 or L-leucine retarded synthesis of IGF-I receptor and its precursor molecule. SB216763 (but not l-leucine) destabilized IGF-I receptor mRNA and decreased its level, without changing IGF-I receptor gene transcription. In SB216763-treated cells, IGF-I-induced Tyr-autophosphorylation of IGF-I receptor was decreased by 36%, compared to nontreated cells. IGF-I attenuated constitutive Ser(396)-phosphorylation of tau by 30% in nontreated cells, but not in SB216763-treated cells. IGF-I-induced down-regulations of (125)I-IGF-I binding and IGF-I receptor, as well as IGF-I-induced phosphorylations of GSK-3beta and mTOR were restored to the control levels of nontreated cells after washout of IGF-I (10 nM for 12 h)-treated cells. Thus, IGF-I down-regulated functional IGF-I receptor via GSK-3beta inhibition and mTOR activation; constitutive activity of GSK-3beta maintained IGF-I receptor level in nonstimulated cells.

A new aspect of nickel-catalyzed Grignard cross-coupling reactions: selective synthesis, structure, and catalytic behavior of a T-shape three-coordinate nickel(i) chloride bearing a bulky NHC ligand

A novel NHC-nickel(i) chloride was isolated by the reactions of Ni(IPr)₂ with chloroarenes. High catalyst activity of the Ni(i) complex was first demonstrated in Grignard cross-coupling reactions of aryl halides.

[Simulation of thoracoscopic esophagectomy for esophageal cancer by three-dimensional computed tomography and usefulness for preservation of bronchial arteries]

Thoracoscopic esophagectomy for esophageal cancer was simulated preoperatively by 3-dimensional computed tomography (3D-CT). The anatomical structures such as major vessels, bone, trachea and bronchi, esophagus, lymph nodes, and broncial arteries were extracted from multi-detector row CT scanning and integrated to build the virtual operative field by multi-volume fusion. The virtual thoracoscopy was helpful to understand the location of lymph nodes and bronchial arteries in relation to the adjacent anatomical structures. Preservation of bronchial arteries is important to avoid tracheobronchial ischemia which is a fatal complication in salvage esophagectomy after definitive chemoradiotherapy. 3D-CT revealed anatomical variations of bronchial arteries and was useful for identification and preservation of bronchial arteries in thoracoscopic esophagectomy.

The effects of seasonal and interannual variability of oceanic structure in the western Pacific North Equatorial Current on larval transport of the Japanese eel Anguilla japonica

As the North Equatorial Current (NEC)-bifurcation is known to be related to El Niño-Southern Oscillation (ENSO) events, the influence of the position of the NEC bifurcation on transport success of the larval Japanese eel Anguilla japonica was investigated. Using a Lagrangian modelling approach, larval transport was simulated and the relative influence of El Niño and La Niña events and the NEC-bifurcation position on the success of particle transport analysed. The number of particles transported from the NEC to the Kuroshio tended to be lowest during El Niño years, and differences between La Niña and regular years were small. The transport success observed in simulations showed some relationships to annual A. japonica glass eel recruitment to Tanegashima Island over 1993 to 2001, but not in 2002. The study shows that particle tracking simulations can be used to improve knowledge of the oceanic migration of A. japonica but further studies are required, including comparisons with the effects on larval survival of fluctuations in temperature and food availability.

Behavior of solutions of the Hodgkin-Huxley equations and its relation to properties of mechanoreceptors

The membrane current in the Hodgkin-Huxley equations is considered to be a stimulus to the membrane and the responses to the simulus are numerically calculated. Responses of the Hodgkin-Huxley model to an alternating current superimposed upon a constant bias current show qualitative analogy to responses of biological mechanoreceptors. The intensity of the bias current seems to correspond to the degree of adaptation of actual receptors.