Biomedical subjects

Y Fukui

Publications and source records attributed to Y Fukui.

At least 163 records · Page 9Linked to original sources

PubMed1998

cDNA cloning, gene expression and subcellular localization of anthocyanin 5-aromatic acyltransferase from Gentiana triflora.

Acylation of anthocyanins with hydroxycinnamic acid derivatives is one of the most important and less under-stood modification reactions during anthocyanin biosynthesis. Anthocyanin aromatic acyltransferase catalyses the transfer of hydroxycinnamic acid moieties from their CoA esters to the glycosyl groups of anthocyanins. A full-length cDNA encoding the anthocyanin 5-aromatic acyltransferase (5AT) (EC 2.3.1.153) that acylates the glucose bound at the 5-position of anthocyanidin 3,5-diglucoside was isolated from petals of Gentiana triflora on the basis of the amino acid sequence of the purified enzyme. The isolated full-length cDNA had an open reading frame of 469 amino acids and the calculated molecular weight was 52,736. The deduced amino acid sequence contains consensus motifs that are conserved among the putative acyl CoA-mediated acyltransferases, and this indicates that 5AT is a member of a proposed superfamily of multi-functional acyltransferases (St-Pierre et al. (1998) Plant J. 14, 703-713). The cDNA was expressed in Escherichia coli and yeast, and confirmed to encode 5AT. The enzymatic characteristics of the recombinant 5AT were consistent with those of the native gentian 5AT. Immunoblot analysis using specific antibodies to 5AT showed that the 5AT protein is present in petals, but not in sepals, stems or leaves of G. triflora. RNA blot analysis showed that the 5AT gene is expressed only in petals and that its expression is temporally regulated during flower development coordinately with other anthocyanin biosynthetic genes. Immunohistochemical analysis demonstrated that the 5AT protein is specifically expressed in the outer epidermal cells of gentian petals and that it is localized mainly in the cytosol.

Acyltransferases↗

PubMed1998

Thirty-eight years experience of malignant hepatic tumors in infants and childhood.

A description is given of therapeutic experiences with 39 cases of malignant liver tumors in infancy and childhood during the past 38 years. Of these patients, 9 not undergoing hepatic resection all died, while 18 (60%) of 30 patients treated by hepatic resection survived. When only patients with hepatoblastoma are considered, 14 of 24 patients are alive, although 3 of them had local recurrence and had lung metastasis. Among patients with other types of liver tumor, those with hepatocellular carcinomas (2 cases) and vascular neoplasms all died in a short period of time, whereas 2 with yolk sac tumor and one with metabolic pancreatic tumor are alive despite of tumor recurrence. In summary, the results of surgical treatment of malignant liver tumors in infancy and childhood, which formerly were poor, have been improved remarkably, which we owe mainly to: 1) advances in diagnostic imaging techniques (e.g., angiography, ultrasonography, CT and MRI) permitting early diagnosis, localization of tumor, visualization of the coursing of major vessels (particularly, hepatic artery & vein) and more accurate definition of resectability, 2) technical improvement of hepatic resection and 3) progress of chemotherapy mainly with cisplatin and adriamycin.

Adolescent↗

PubMed1998

Amino acid metabolism of bovine blastocysts derived from parthenogenetically activated or in vitro fertilized oocytes.

The uptake and synthesis of 19 amino acids by fresh or frozen-thawed bovine blastocysts produced by parthenogenesis (PT) or in vitro fertilization (IVF) were compared in the present study. Fresh blastocysts, 180 h after IVF or PT activation, and frozen-thawed blastocysts, 168 h old and cultured for 12 h post-thawing, were cultured in synthetic oviduct fluid medium (SOFM) containing polyvinyl alcohol (PVA) with both essential and non-essential amino acids (EAA and NEAA, respectively) (Medium 1: M1) or SOFM containing PVA with only EAA (Medium 2: M2). In Experiment 1, when fresh or frozen-thawed PT blastocysts were cultured in M1, the uptake of glutamate (in fresh only), aspartate and arginine, and the synthesis of glutamine and alanine were significantly enhanced. In the culture with M2, serine, asparagine, glutamate, glutamine, glycine, arginine and alanine were significantly taken up. It was found that the glutamine concentrations was significantly higher (P < 0.001) in the culture medium drops containing embryos than in the drops without embryos. In Experiment 2, when PT blastocysts were cultured in M1, the uptake of aspartate and synthesis of alanine were greater (P < 0.01) than those by IVF blastocysts. When M2 was used, a significant (P < 0.01) production of serine, asparagine, glutamate, glutamine and alanine, and the uptake of arginine by PT blastocysts were observed. In Experiment 3, when IVF blastocysts were cultured in M1, fresh blastocysts depleted more aspartate and glutamate, and produced more glutamine and alanine than frozen-thawed blastocysts. When cultured in M2, frozen-thawed blastocysts depleted more threonine (P < 0.01) than fresh blastocysts. These results indicate that the uptake and synthesis of amino acids were different in fresh or frozen-thawed bovine blastocysts derived from PT or IVF. These differences in amino acid metabolism may be related to the viability of the blastocysts.

Alanine↗

PubMed1998

Downstream of phosphatidylinositol-3 kinase, a multifunctional signaling molecule, and its regulation in cell responses.

Phosphatidylinositol (PI)-3 kinase is an enzyme that phosphorylates the D-3 position of PI and its derivatives. It is activated immediately after growth factor or differentiation factor stimulation, suggesting that PI-3 kinase is involved in signal transduction of the stimulation. PI-3 kinase appears to play various important roles including signaling to the nucleus, vesicle transport, and rearrangement of the cytoskeleton since many cell responses which require these events are affected by inhibition or activation of PI-3 kinase. To understand how PI-3 kinase can act in such multiple ways, it is important to identify the factors downstream of PI-3 kinase. In this review, we discuss the factors downstream of PI-3 kinase and the methods used to identify them. Recent studies revealed that some proteins involved in vesicle transport or in rearrangement of the cytoskeleton are regulated by the phospholipids generated by PI-3 kinase, implying the mechanism by which PI-3 kinase regulates these cell responses.

Animals↗

PubMed1998

Real-time relationships between intraluteal and plasma concentrations of endothelin, oxytocin, and progesterone during prostaglandin F2alpha-induced luteolysis in the cow.

Recent observations suggest that the endothelial cell-derived vasoconstrictive peptide endothelin-1 (ET-1) interacts with prostaglandin F2alpha (PGF2alpha) and that luteal ET-1 participates in the rapid cascade of functional luteolysis in vivo. Thus, the present study aimed to determine in detail the real-time changes in ET-1, oxytocin (OT), and progesterone (P4) concentrations within the regressing corpus luteum (CL), along with the changes in ovarian venous plasma (OVP) ipsilateral to the CL as well as in jugular venous plasma (JVP) in the cow. In the first study, peripheral plasma from daily sampling during the estrous cycle (n = 6) showed clear changes in ET-1 concentration with the stage of the cycle (p < 0.05). ET-1 remained at basal concentrations (23.2+/-1.3 pg/ml) on Days 2-12, increased (p < 0.05) on Days 13-19 (33.5+/-2.6 pg/ml), and reached the highest (p < 0.001) concentrations (45.6+/-4.4 pg/ml) on Days 20-22 after estrus. These data indicate that plasma ET-1 concentration increases around luteolysis and estrus. In the second study, a microdialysis system (MDS) was surgically implanted into the CL of 11 cows in the midluteal phase. In 4 of the 11 cows, the catheter was also fitted to the ovarian vein ipsilateral to the CL at surgery. A PGF2alpha analogue (cloprostenol; 500 microg) was then injected (designated as 0 h) i.m. to induce luteolysis. In the cows fitted with an MDS, the PGF2alpha injection clearly induced a rapid decrease in intraluteal P4 release within 4 h (p < 0.05), and the levels decreased to 20% of the baseline after 24 h. Intraluteal release of ET-1 increased (p < 0.05) to 160% within 4 h after PGF2alpha injection, when an enormous OT release (to 950%) occurred, which reached a plateau of 250% after 20 h that persisted until 72 h. ET-1 release into the ovarian vein began to increase at 2 h after PGF2alpha injection, when the acute OT release almost dropped to the baseline. The ET-1 concentration was temporarily (between 0 and 24 h after PGF2alpha) 2-3 times higher in OVP than in JVP (p < 0.05), and increased again to higher levels than in JVP from 32 to 64 h (p < 0.05). ET-1 concentrations in JVP gradually increased from 10 pg/ml to 30 pg/ml during PGF2alpha-induced luteolysis (p < 0.05). In conclusion, PGF2alpha injection rapidly increased ET-1 release within the regressing CL as well as into the ovarian venous blood in the cow. The overall results strongly support the hypothesis that luteal ET-1 is a local luteolytic mediator/promotor in the regressing bovine CL.

Animals↗

PubMed1998

A model analysis of aftereffects of high-intensity DC stimulation on action potential of ventricular muscle.

The mechanism for aftereffects of high-intensity dc stimulation on ventricular muscle was studied by using Beeler-Reuter's action potential model. A leak conductance (Gpore, maximal value from 40 to 80 microS for 1 cm2 of membrane), which mimics reversible dielectric breakdown of the cell membrane by the shock, was incorporated into the model. To simulate resealing process, Gpore was assumed to decrease after the shock exponentially at a time constant (tau pore) of 5-50 s. The simulation results are qualitatively consistent with our experimental observations in guinea pig papillary muscle [1]; they include prolonged depolarization, diastolic depolarization or oscillation of membrane potential leading to a single or multiple spontaneous excitation. The phase-independence and shock intensity-dependence can also be reproduced. Analysis of current components has revealed that: 1) a large inward leak current (Ileak) is responsible for the prolonged depolarization; 2) time-dependent decay of outward current (IX1) in combination with Ileak and slow inward current (I(s)) results in diastolic depolarization or oscillation of membrane potential; 3) spontaneous excitation depends on an activation of I(s). These findings support our hypothesis that strong shocks (> 15 V/cm) will produce abnormal arrhythmogenic responses in ventricular muscle through a transient rupture of sarcolemmal membrane.

Action Potentials↗

PubMed1998

Spatiotemporal dynamics of actin concentration during cytokinesis and locomotion in Dictyostelium.

To study the spatial and temporal regulation of the actin cytoskeleton, we have analyzed the actin concentration dynamics in live Dictyostelium. The relative actin concentration was analyzed with respect to cell behavior by fluorescence morphometry. We electroporated rhodamine-actin into Dictyostelium cells and acquired images with 200-300 millisecond temporal and approximately 250 nm spatial resolutions. To convert fluorescence intensity into actin concentration, the observation was made on nearly two-dimensional cells, and the actin signal was ratioed over a volume marker (FITC-BSA or GFP). Since the emission of FITC and GFP is pH-dependent, we first measured the cytoplasmic pH in live cells and determined that the pHi in pseudopods is same as that of general cytoplasm. During cytokinesis, the relative concentration of actin in the cleavage furrow was significantly higher than in the general cytoplasm. In migrating cells, actin was recruited surprisingly rapidly, particularly in the pseudopod. We found that the region of high actin concentration moves relative to the leading edge when a pseudopod projects or retracts. When the pseudopod retracts, the actin density dissipates within 5 seconds. We have also found that actin accumulates in developing pseudopods in an oscillatory manner, and this timing coordinates with advancement of the centroid. This is the first study to reveal the dynamic changes in relative concentration of actin in live cells and to quantitatively correlate these changes with the locomotive behavior of the amoeba.

Actins↗

PubMed1998

Microinjection of activated phosphatidylinositol-3 kinase induces process outgrowth in rat PC12 cells through the Rac-JNK signal transduction pathway.

We have previously shown that sustained phosphatidylinositol (PI)-3 kinase activity is necessary for neurite outgrowth of PC12 cells induced by nerve growth factor (NGF). Microinjection of a constitutively active mutant of PI-3 kinase induced process formation suggesting that PI-3 kinase is indeed involved in the neurite outgrowth. However, the processes appeared to be incomplete neurites as they had very poor organization of F-actin and GAP43 antigen. The microtubule network was enhanced in the process-bearing cells and process formation was inhibited by colchicine suggesting that microtubules play an important role in process formation downstream of PI-3 kinase. These cell responses were inhibited by dominant-negative mutants of Rac and Sek1/SAPK but not by a dominant-negative mutant Ras and PD98059, a MAP kinase kinase (MEK) inhibitor, suggesting that not the Ras-MAP kinase pathway but the Rac-Jun N-terminal kinase (JNK) pathway is involved in process formation.

Animals↗

PubMed1998

Isolation, characterization, and sugar chain structure of endoPG Ia, Ib and Ic from Stereum purpureum.

Three endopolygalacturonases (endoPG Ia, Ib, and Ic) were isolated from the culture filtrate of Stereum purpureum, the causative fungus of apple silver-leaf disease. Their properties, including specific activities, optimum pHs, thermal stabilities, and kinetic parameters (K(m) and Vmax) were compared. Their properties were very similar to one another except for the substrate specificity and relative molecular mass. The sugar chains of endoPG Is were released by hydrazinolysis, and one major sugar chain common to endoPG Is was isolated. The pyridylamino sugar was characterized by a two-dimensional mapping method using HPLC, and identified as a high mannose type N-linked sugar chain, Man alpha 1-6(Man alpha 1-3)Man alpha 1-6(Man alpha 1-3) Man beta 1-4 GlcNAc beta 1-4 GlcNAc (designated as M5.1). Observation of the course of Western blot analysis for the proteins from the culture filtrate with endoPG I antibodies showed that the fungus secreted three endoPG Is into the culture broth during the growing period.

Amino Sugars↗

PubMed1998

Effects of buprenorphine and Ro 15-4513 on delayed death and brain beta-endorphin levels in rats treated with cocaine or cocaine-ethanol.

The present study was aimed at elucidating the relationship between brain beta-endorphin, which was estimated by the immunofluorescence method, and fatal drug toxicities due to cocaine and combined cocaine-ethanol administration, including the late fatal toxicities clinically noted. beta-endorphin is an endogenous opioid peptide, and its secretion has been suggested to be influenced by physiological stresses. Furthermore, since protection against these fatal toxicities has been previously reported to be provided by buprenorphine (a ligand for opioid receptors) and Ro 15-4513 (a ligand for benzodiazepine receptors), this study also focused on the relationship between the effects of these two ligands and the changes in brain beta-endorphin immunoreactivity. In the fatal toxicity study, a toxic dose (75 mg/kg, i.p.) of cocaine combined with and without ethanol (3 g/kg, i.p.) was administered to the rats, with and without buprenorphine (0.25, 0.5, 1 mg/kg, i.p.) or Ro 15-4513 (5, 10, 15 mg/kg, i.p.). All of the deaths that occurred in these animals were divided into two groups: early deaths with early toxic symptoms in which the drugs were detected in the tissue samples, and late deaths with late toxic symptoms in which no drugs were detected in the samples. Without the administration of buprenorphine or Ro 15-4513, the frequency of late deaths was higher in the cocaine group as compared to the cocaine-ethanol group. The total mortality rate was effectively attenuated by treatment with 0.25 mg/kg buprenorphine or 10 mg/kg Ro 15-4513. Following treatment with 1 mg/kg buprenorphine or 15 mg/kg Ro 15-4513, the frequency of late deaths was significantly enhanced in the cocaine group. The brain and liver cocaethylene concentrations were also attenuated in those groups in which the total mortality rates were attenuated. In the brain beta-endorphin immunoreactivity study, the number of beta-endorphin immunoreactive nerve cells at the arcuate nucleus was counted at 3 minutes or 24 hours after the drug treatment. At 3 minutes after the drug treatment, the number of weakly immunoreactive cells with photographic light absorption values greater than 50% was enhanced in the groups in which the frequency of late deaths had been increased. In the cocaine-ethanol groups treated with buprenorphine or Ro 15-4513, this enhancement of weakly immunoreactive cells was observed when the total mortality rate was increased, regardless of the type of death. At 24 hours after the drug treatment (50 mg/kg cocaine), an enhancement of the weakly immunoreactive cells only was observed in all of the groups in which the occurrence of toxicities had been enhanced, regardless of the type of toxicity. Therefore, it can be concluded that the enhancement of total brain beta-endorphin immunoreactivity was closely correlated with the increase in the frequency of total fatal toxicities, and that the enhancement of weakly immunoreactive cells was closely correlated with the increase in the frequency of delayed fatal toxicities.

Affinity Labels↗

PubMed1998

[Signal transduction of PI3-kinase].

Phosphatidylinositol (PI)-3 kinase is an enzyme that phosphorylates D3 position of PI and its derivatives. It is activated immediately after growth factor or differentiation factor stimulation, suggesting that PI-3 kinase is involved in signal transduction of the stimulations. PI-3 kinase appears to play important roles in various points including signaling to the nucleus, vesicle transport, and rearrangement of cytoskeleton since many cell responses which requires these events were affected by inhibition or activation of PI-3 kinase. There are many mechanisms of activation of PI-3 kinase including binding to phosphotyrosine containing proteins or binding to Ras. Each mechanism can target PI-3 kinase to the right place to induce the right cell responses.

Actins↗

PubMed1997

Estimation of the numerical densities of neurons and synapses in cerebral cortex.

In this paper we discuss a stereological technique, 'the unfolding method', for a quantitative study of the nervous system [1,31]. Stereology implies a geometric analysis of structures and textures, and is a method to derive directly metric properties of structures from two-dimensional sections on the basis of geometrico-statistical reasoning [36,37]. Recent advances in the stereological method allow quantitative analysis [8,19,27,32]. Images on sections provide only two-dimensional information, but the stereological method can offer three-dimensional and quantitative information [19]. The need for quantitative analysis is more important and useful in the central nervous system (CNS) than in other organs. Two functional units, neurons and synapses, are of particular interest in evaluating CNS function. Numerical densities of neurons and synapses in rat visual cortex were estimated using the unfolding method at light and electron microscopic levels, respectively. Once the numerical densities of neurons and synapses were obtained, synapse-to-neuron ratios could be calculated. The ratios are interpreted as a means to obtain an index of interneuronal connectivity [9]. The unfolding method may become a powerful strategy in neuroscience research when numerical estimates are performed in restricted areas such as cortical layers II-IV, because this method is less time-consuming than other stereological methods [6,21,22].

Animals↗

PubMed1997

Immunohistochemical and RT-PCR detection of Na+-dependent inorganic phosphate cotransporter (NaPi-2) in rat brain.

Expression of a renal Na+-dependent inorganic phosphate (Pi) cotransporter (NaPi-2) was studied in rat forebrain with reverse transcription and polymerase chain reaction (RT-PCR) and immunohistochemistry. RT-PCR analysis for total RNA from whole brain and sequencing of the PCR products showed expression of NaPi-2 mRNA in the brain. Immunohistochemical analysis revealed NaPi-2 staining in many nonpyramidal neurons of all six layers throughout neocortical areas and in neurons of proisocortical and periallocortical areas. NaPi-2-immunoreactive neurons were also detectable in the piriform cortex, hippocampal formation, caudate-putamen, amygdaloid nuclei and lateral geniculate nucleus. Furthermore, NaPi-2 staining was shown in ependymal cells and microvascular endothelial cells. The present results suggest that NaPi-2 is synthesized within the brain and involved in maintaining Pi homeostasis of certain neurons and/or the entire brain.

Animals↗

PubMed1997

In vitro and in vivo evidence for high frequency of I-Ab-reactive CD4+ T cells in HLA-DQ or HLA-DRA transgenic mice lacking endogenous MHC class I and/or class II expression.

Although T cells are educated to recognize foreign antigenic peptides in the context of self MHC molecules during their development in the thymus, peripheral T cells also recognize allo- and xeno-MHC molecules. The lower frequency of xeno-MHC-reactive T cells than that of allo-MHC-reactive T cells is often explained by the difference in the degree of homology between xeno- or allo-MHC and self MHC molecules, as well as by the species barrier of the molecules involved in immune recognition. To distinguish these two possibilities, we estimated the frequency of I-Ab-reactive CD4+ T cells selected by HLA-DQ or DR alpha E beta b molecules, using HLA-DQ6 and HLA-DRA transgenic C57BL/6 (B6) mice lacking endogenous MHC class I and/or class II molecules (DQ6A0/0 and DR alpha 30A0/0 beta 20/0). CD4+ lymph node T cells from DQ6A0/0 and DR alpha 30A0/0 beta 20/0 showed the strong proliferative response to I-Ab molecules. In addition, DQ6A0/0 and DR alpha 30A0/0 beta 20/0 rejected the skin graft from mice expressing I-Ab molecules irrespective of MHC class I expression, indicating that the CD4+ T cells recognizing I-Ab molecules are directly involved in this rejection. The estimated frequency of I-Ab-reactive CD4(+)CD8- thymocytes in DR alpha 30A0/0 beta 20/0 and DQ6A0/0 was comparable with that observed in the MHC class II-disparate strains. Our findings thus indicate that CD4+ T cells selected to mature on xeno-MHC class II molecules such as HLA-DQ6 or DR alpha E beta b, when these molecules are expressed in mice, recognize I-Ab molecules as allo-MHC class II, despite the less structural homology.

Animals↗

PubMed1997

Anthocyanin 5-aromatic acyltransferase from Gentiana triflora. Purification, characterization and its role in anthocyanin biosynthesis.

Acylation with hydroxycinnamic acids stabilizes anthocyanins and makes their colour bluer (bathochromic shift). We purified to homogeneity one acylation enzyme, hydroxycinnamoyl-CoA:anthocyanidin 3,5-diglucoside 5-O-glucoside-6"'-O-hydroxycinnamoyltransferase, from blue petals of Gentiana triflora. It is a single polypeptide protein of 52 kDa with a pI of 4.6. It catalyzes the transfer of the p-coumaric acid and caffeic acid from their CoA esters to the 5-glucosyl moiety of anthocyanidin 3,5-diglucosides but could not use malonyl-CoA as an acyl donor. Neither anthocyanidin 3-monoglucoside nor anthocyanins aromatically acylated at the 3-glucosyl moiety could be acylated by this enzyme. Aromatic acylation of anthocyanidin 3,5-diglucoside by this enzyme caused a bathochromic shift and increased pigment stability in neutral to weakly basic pH. Other anthocyanins from the petals of G. triflora were isolated and their structures were determined by fast-atom-bombardment MS and NMR. The biosynthetic pathway of gentiodelphin, a diacylated anthocyanin accumulating in G. triflora petals, is proposed on the basis of these results.

Acylation↗

PubMed1997

Heterodimeric phosphoinositide 3-kinase consisting of p85 and p110beta is synergistically activated by the betagamma subunits of G proteins and phosphotyrosyl peptide.

Phosphoinositide 3-kinase (PI 3-kinase) is a key signaling enzyme implicated in variety of receptor-stimulated cell responses. Receptors with intrinsic or associated tyrosine kinase activity recruit heterodimeric PI 3-kinases consisting of a 110-kDa catalytic subunit (p110) and an 85-kDa regulatory subunit (p85). We separated a PI 3-kinase that could be stimulated by the betagamma subunits of G protein (Gbetagamma) from rat liver. The Gbetagamma-sensitive PI 3-kinase appeared to be a heterodimer consisting of p110beta and p85 (or their related subunits). The stimulation by Gbetagamma was inhibited by the GDP-bound alpha subunit of the inhibitory GTP-binding protein. Moreover, the stimulatory action of Gbetagamma was markedly enhanced by the simultaneous addition of a phosphotyrosyl peptide synthesized according to the amino acid sequence of the insulin receptor substrate-1. Such enzymic properties could be observed with a recombinant p110beta/p85alpha expressed in COS-7 cells with their cDNAs. In contrast, another heterodimeric PI 3-kinase consisting of p110alpha and p85 in the same rat liver, together with a recombinant p110alpha/p85alpha, was not activated by Gbetagamma, although their activities were stimulated by the phosphotyrosyl peptide. These results indicate that p110beta/p85 PI 3-kinase may be regulated in a cooperative manner by two different types of membrane receptors, one possessing tyrosine kinase activity and the other activating GTP-binding proteins.

Amino Acid Sequence↗

PubMed1997

Dual control of neurite outgrowth by STAT3 and MAP kinase in PC12 cells stimulated with interleukin-6.

IL-6 induces differentiation of PC12 cells pretreated with nerve growth factor (NGF). We explored the signals required for neurite outgrowth of PC12 cells by using a series of mutants of a chimeric receptor consisting of the extracellular domain of the granulocyte-colony stimulating factor (G-CSF) receptor and the cytoplasmic domain of gp130, a signal-transducing subunit of the IL-6 receptor. The mutants incapable of activating the MAP kinase cascade failed to induce neurite outgrowth. Consistently, a MEK inhibitor, PD98059, inhibited neurite outgrowth, showing that activation of the MAP kinase cascade is essential for the differentiation of PC12 cells. In contrast, a mutation that abolished the ability to activate STAT3 did not inhibit, but rather stimulated neurite outgrowth. This mutant did not require NGF pretreatment for neurite outgrowth. Dominant-negative STAT3s mimicked NGF pretreatment, and NGF suppressed the IL-6-induced activation of STAT3, supporting the idea that STAT3 might regulate the differentiation of PC12 cells negatively. These results suggest that neurite outgrowth of PC12 cells is regulated by the balance of MAP kinase and STAT3 signal transduction pathways, and that STAT3 activity can be regulated negatively by NGF.

Animals↗

PubMed1997

Expression of a constitutively active phosphatidylinositol 3-kinase induces process formation in rat PC12 cells. Use of Cre/loxP recombination system.

It has been shown that inhibition of phosphatidylinositol (PI) 3-kinase blocks neurite outgrowth of PC12 cells stimulated with nerve growth factor. To further assess the role of PI 3-kinase, the active form of PI 3-kinase was expressed in PC12 cells by the adenovirus mediated introduction of a site-specific recombinase, Cre. After expression of the active PI 3-kinase, elevation of the levels of PI 3,4-diphosphate and PI 3,4,5-trisphosphate as well as formation of neurite-like processes was observed. The process formation was inhibited by wortmannin, a selective inhibitor of PI 3-kinase, which suggests that a high activity of PI 3-kinase was responsible for the formation of these processes. The processes lacked accumulation of F-actin and GAP43 at the growth cone, which suggests that the processes were incomplete compared with neurites. Instead, the bundling of microtubules was enhanced, which suggests that organization of the microtubules might be driving the process of elongation in the cells expressing the active PI 3-kinase. Induction of active PI 3-kinase resulted in activation of Jun N-terminal kinase but not of mitogen-activated protein kinase or protein kinase B/Rac protein kinase/Akt. These results suggest that PI 3-kinase is involved in neurite outgrowth in PC12 cells and that activation of Jun N-terminal kinase cascade may be involved in the cell response.

Animals↗