A mutation in succinate dehydrogenase cytochrome b causes oxidative stress and ageing in nematodes

Much attention has focused on the aetiology of oxidative damage in cellular and organismal ageing. Especially toxic are the reactive oxygen byproducts of respiration and other biological processes. A mev-1(kn1) mutant of Caenorhabditis elegans has been found to be hypersensitive to raised oxygen concentrations. Unlike the wild type, its lifespan decreases dramatically as oxygen concentrations are increased from 1 to 60%. Strains bearing this mutation accumulate markers of ageing (such as fluorescent materials and protein carbonyls) faster than the wild type. We show here that mev-1 encodes a subunit of the enzyme succinate dehydrogenase cytochrome b, which is a component of complex II of the mitochondrial electron transport chain. We found that the ability of complex II to catalyse electron transport from succinate to ubiquinone is compromised in mev-1 animals. This may cause an indirect increase in superoxide levels, which in turn leads to oxygen hypersensitivity and premature ageing. Our results indicate that mev-1 governs the rate of ageing by modulating the cellular response to oxidative stress.

Phase III study comparing oxaliplatin plus S-1 with cisplatin plus S-1 in chemotherapy-naïve patients with advanced gastric cancer

BACKGROUND

We evaluated the efficacy and safety of S-1 plus oxaliplatin (SOX) as an alternative to cisplatin plus S-1 (CS) in first-line chemotherapy for advanced gastric cancer (AGC).

PATIENTS AND METHODS

In this randomized, open-label, multicenter phase III study, patients were randomly assigned to receive SOX (80-120 mg/day S-1 for 2 weeks with 100 mg/m(2) oxaliplatin on day 1, every 3 weeks) or CS (S-1 for 3 weeks with 60 mg/m(2) cisplatin on day 8, every 5 weeks). The primary end points were noninferiority in progression-free survival (PFS) and relative efficacy in overall survival (OS) for SOX using adjusted hazard ratios (HRs) with stratification factors; performance status and unresectable or recurrent (+adjuvant chemotherapy) disease.

RESULTS

Overall, 685 patients were randomized from January 2010 to October 2011. In per-protocol population, SOX (n = 318) was noninferior to CS (n = 324) in PFS [median, 5.5 versus 5.4 months; HR 1.004, 95% confidence interval (CI) 0.840-1.199; predefined noninferiority margin 1.30]. The median OS for SOX and CS were 14.1 and 13.1 months, respectively (HR 0.958 with 95% CI 0.803-1.142). In the intention-to-treat population (SOX, n = 339; CS, n = 337), the HRs in PFS and OS were 0.979 (95% CI 0.821-1.167) and 0.934 (95% CI 0.786-1.108), respectively. The most common ≥grade 3 adverse events (SOX versus CS) were neutropenia (19.5% versus 41.8%), anemia (15.1% versus 32.5%), hyponatremia (4.4% versus 13.4%), febrile neutropenia (0.9% versus 6.9%), and sensory neuropathy (4.7% versus 0%).

CONCLUSION

SOX is as effective as CS for AGC with favorable safety profile, therefore SOX can replace CS.

CLINICAL TRIAL NUMBER

JapicCTI-101021.

A novel membrane glycoprotein, SHPS-1, that binds the SH2-domain-containing protein tyrosine phosphatase SHP-2 in response to mitogens and cell adhesion

Protein tyrosine phosphatases (PTPases), such as SHP-1 and SHP-2, that contain Src homology 2 (SH2) domains play important roles in growth factor and cytokine signal transduction pathways. A protein of approximately 115 to 120 kDa that interacts with SHP-1 and SHP-2 was purified from v-src-transformed rat fibroblasts (SR-3Y1 cells), and the corresponding cDNA was cloned. The predicted amino acid sequence of the encoded protein, termed SHPS-1 (SHP substrate 1), suggests that it is a glycosylated receptor-like protein with three immunoglobulin-like domains in its extracellular region and four YXX(L/V/I) motifs, potential tyrosine phosphorylation and SH2-domain binding sites, in its cytoplasmic region. Various mitogens, including serum, insulin, and lysophosphatidic acid, or cell adhesion induced tyrosine phosphorylation of SHPS-1 and its subsequent association with SHP-2 in cultured cells. Thus, SHPS-1 may be a direct substrate for both tyrosine kinases, such as the insulin receptor kinase or Src, and a specific docking protein for SH2-domain-containing PTPases. In addition, we suggest that SHPS-1 may be a potential substrate for SHP-2 and may function in both growth factor- and cell adhesion-induced cell signaling.

Molecular cloning and characterization of a new multispecific organic anion transporter from rat brain

A cDNA encoding the new member of the multispecific organic anion transporter family, OAT3, was isolated by the reverse transcription-polymerase chain reaction cloning method. Degenerate primers were designed based on the sequences conserved among OAT1, OAT2, and organic cation transporter 1 (OCT1), and reverse transcription-polymerase chain reaction was performed using rat brain poly(A)+ RNA. The 536-amino acid protein sequence encoded by OAT3 showed 49, 39, and 36% identity to those of OAT1, OAT2, and OCT1, respectively. Northern blot analysis revealed that rat OAT3 mRNA is expressed in the liver, brain, kidney, and eye. When expressed in Xenopus laevis oocytes, OAT3 mediated the uptake of organic anions, such as p-aminohippurate (Km = 65 microM), ochratoxin A (Km = 0.74 microM), and estrone sulfate (Km = 2.3 microM) and a cationic compound, cimetidine. OAT3-mediated uptake of [3H]estrone sulfate was sodium-independent. para-Aminohippuric acid, estrone sulfate or ochratoxin A did not show any trans-stimulatory effect on either influx or efflux of [3H]estrone sulfate via OAT3. Organic anions such as sulfobromophthalein, probenecid, indocyanine green, bumetanide, piroxicam, furosemide, azidodeoxythymidine, 4, 4'-diisothiocyanostilbene-3,3'-disulfonic acid, and benzylpenicillin inhibited OAT3-mediated estrone sulfate uptake, while ouabain and digoxin did not. Organic cations such as tetraethylammonium, guanidine, verapamil, and quinidine did not interact with OAT3. Acidic metabolites of neurotransmitters derived from dopamine, epinephrine, norepinephrine, and serotonin inhibited the uptake of estrone sulfate via OAT3. These results suggest an important role of OAT3 in the excretion/detoxification of endogenous and exogenous organic anions, especially from the brain.

The cell-surface proteoglycan Dally regulates Wingless signalling in Drosophila

Wingless (Wg) is a member of the Wnt family of growth factors, secreted proteins that control proliferation and differentiation during development. Studies in Drosophila have shown that responses to Wg require cell-surface heparan sulphate, a glycosaminoglycan component of proteoglycans. These findings suggest that a cell-surface proteoglycan is a component of a Wg/Wnt receptor complex. We demonstrate here that the protein encoded by the division abnormally delayed (dally) gene is a cell-surface, heparan-sulphate-modified proteoglycan. dally partial loss-of-function mutations compromise Wg-directed events, and disruption of dally function with RNA interference produces phenotypes comparable to those found with RNA interference of wg or frizzled (fz)/Dfz2. Ectopic expression of Dally potentiates Wg signalling without altering levels of Wg and can rescue a wg partial loss-of-function mutant. We also show that dally, a regulator of Decapentaplegic (Dpp) signalling during post-embryonic development, has tissue-specific effects on Wg and Dpp signalling. Dally can therefore differentially influence signalling mediated by two growth factors, and may form a regulatory component of both Wg and Dpp receptor complexes.

Safety and efficacy of nivolumab in combination with S-1/capecitabine plus oxaliplatin in patients with previously untreated, unresectable, advanced, or recurrent gastric/gastroesophageal junction cancer: interim results of a randomized, phase II trial (ATTRACTION-4)

BACKGROUND

Nivolumab is approved as an option for third- or later-line treatment of advanced gastric/gastroesophageal junction (G/GEJ) cancer in several countries after ATTRACTION-2. To further improve the therapeutic efficacy of first-line therapy, exploration of a nivolumab-chemotherapy combination is warranted. In part 1 (phase II) of ATTRACTION-4, the safety and efficacy of nivolumab combined with S-1 plus oxaliplatin (SOX) or capecitabine plus oxaliplatin (CapeOX) as first-line therapy for unresectable advanced or recurrent human epidermal growth factor receptor 2 (HER2)-negative G/GEJ cancer were evaluated.

PATIENTS AND METHODS

Patients were randomized (1 : 1) to receive nivolumab (360 mg intravenously every 3 weeks) plus SOX (S-1, 40 mg/m2 orally twice daily for 14 days followed by 7 days off; oxaliplatin, 130 mg/m2 intravenously on day 1 every 3 weeks) or CapeOX (capecitabine, 1000 mg/m2 orally twice daily for 14 days followed by 7 days off; oxaliplatin, 130 mg/m2 intravenously on day 1 every 3 weeks) until disease progression, unacceptable toxicity, or consent withdrawal.

RESULTS

Of 40 randomized patients, 39 (nivolumab plus SOX, 21; nivolumab plus CapeOX, 18) and 38 (21 and 17, respectively) comprised the safety and efficacy populations, respectively. Most frequent (>10%) grade 3/4 treatment-related adverse events were neutropenia (14.3%) in the nivolumab plus SOX group, and neutropenia (16.7%), anemia, peripheral sensory neuropathy, decreased appetite, type 1 diabetes mellitus, and nausea (11.1% each) in the nivolumab plus CapeOX group. No treatment-related death occurred. Objective response rate was 57.1% (95% confidence interval 34.0-78.2) with nivolumab plus SOX and 76.5% (50.1-93.2) with nivolumab plus CapeOX. Median overall survival was not reached (NR) in both groups. Median progression-free survival was 9.7 months (5.8-NR) and 10.6 months (5.6-12.5), respectively.

CONCLUSION

Nivolumab combined with SOX/CapeOX was well tolerated and demonstrated encouraging efficacy for unresectable advanced or recurrent HER2-negative G/GEJ cancer. ATTRACTION-4 has proceeded to part 2 (phase III) to compare nivolumab plus SOX/CapeOX versus placebo plus SOX/CapeOX.

CLINICALTRIALS.GOV ID

NCT02746796.

Identification of multispecific organic anion transporter 2 expressed predominantly in the liver

In the present study, we demonstrate that NLT (novel liver-specific transport protein) is a multispecific organic anion transporter of the liver. The amino acid sequence of NLT shows 42% identity to that of the renal multispecific organic anion transporter, OAT1. When expressed in Xenopus laevis oocytes, NLT mediated uptake of organic anions, such as salicylate, acetylsalicylate, PGE2, dicarboxylates and p-aminohippurate. [14C]Salicylate uptake via NLT was saturable (Km = 88.8 +/- 23.4 microM) and sodium-independent. Expression of the mRNA of NLT was detected in the liver and kidney (liver >> kidney). We propose that NLT be renamed OAT2.

A defect in the cytochrome b large subunit in complex II causes both superoxide anion overproduction and abnormal energy metabolism in Caenorhabditis elegans

A mev-1(kn1) mutant of the nematode Caenorhabditis elegans is defective in the cytochrome b large subunit (Cyt-1/ceSDHC) in complex II of the mitochondrial electron transport chain. We have previously shown that a mutation in mev-1 causes shortened life span and rapid accumulation of aging markers such as fluorescent materials and protein carbonyls in an oxygen-dependent fashion. However, it remains unclear as to whether this hypersensitivity is caused by direct toxicity of the exogenous oxygen or by the damage of endogenous reactive oxygen species derived from mitochondria. Here we report important biochemical changes in mev-1 animals that serve to explain their abnormalities under normoxic conditions: (i) an overproduction of superoxide anion from mitochondria; and (ii) a reciprocal reduction in glutathione content even under atmospheric oxygen. In addition, unlike wild type, the levels of superoxide anion production from mev-1 mitochondria were significantly elevated under hyperoxia. Under normal circumstances, it is well known that superoxide anion is produced at complexes I and III in the electron transport system. Our data suggest that the mev-1(kn1) mutation increases superoxide anion production at complex II itself rather than at complexes I and III. The mev-1 mutant also had a lactate level 2-fold higher than wild type, indicative of lactic acidosis, a hallmark of human mitochondrial diseases. These data indicate that Cyt-1/ceSDHC plays an important role not only in energy metabolism but also in superoxide anion production that is critically involved in sensitivity to atmospheric oxygen.

A urease-negative mutant of Helicobacter pylori constructed by allelic exchange mutagenesis lacks the ability to colonize the nude mouse stomach

The urease of Helicobacter pylori has been proposed to be one of its pathogenic factors. A kanamycin resistance determinant was inserted in a cloned urease gene, and transformation-mediated allelic exchange mutagenesis was carried out to introduce the disrupted gene into the corresponding wild-type chromosomal region of a clinical isolate of H. pylori, CPY3401. The resulting mutant, HPT73, had the null activity of urease. Nude mouse stomachs were challenged with these two isogenic strains to examine the role of urease in pathogenesis. Gastritis was found in the CPY3401-challenged stomachs, from which bacteria indistinguishable from CPY3401 were recovered. There was no gastritis in the HPT73-challenged stomachs, and we could not recover H. pylori from them. These results indicated that H. pylori urease is essential for colonizing the nude mouse stomach.

Randomized phase III study of bevacizumab plus FOLFIRI and bevacizumab plus mFOLFOX6 as first-line treatment for patients with metastatic colorectal cancer (WJOG4407G)

BACKGROUND

FOLFIRI and FOLFOX have shown equivalent efficacy for metastatic colorectal cancer (mCRC), but their comparative effectiveness is unknown when combined with bevacizumab.

PATIENTS AND METHODS

WJOG4407G was a randomized, open-label, phase III trial conducted in Japan. Patients with previously untreated mCRC were randomized 1:1 to receive either FOLFIRI plus bevacizumab (FOLFIRI + Bev) or mFOLFOX6 plus bevacizumab (mFOLFOX6 + Bev), stratified by institution, adjuvant chemotherapy, and liver-limited disease. The primary end point was non-inferiority of FOLFIRI + Bev to mFOLFOX6 + Bev in progression-free survival (PFS), with an expected hazard ratio (HR) of 0.9 and non-inferiority margin of 1.25 (power 0.85, one-sided α-error 0.025). The secondary end points were response rate (RR), overall survival (OS), safety, and quality of life (QoL) during 18 months. This trial is registered to the University Hospital Medical Information Network, number UMIN000001396.

RESULTS

Among 402 patients enrolled from September 2008 to January 2012, 395 patients were eligible for efficacy analysis. The median PFS for FOLFIRI + Bev (n = 197) and mFOLFOX6 + Bev (n = 198) were 12.1 and 10.7 months, respectively [HR, 0.905; 95% confidence interval (CI) 0.723-1.133; P = 0.003 for non-inferiority]. The median OS for FOLFIRI + Bev and mFOLFOX6 + Bev were 31.4 and 30.1 months, respectively (HR, 0.990; 95% CI 0.785-1.249). The best overall RRs were 64% for FOLFIRI + Bev and 62% for mFOLFOX6 + Bev. The common grade 3 or higher adverse events were leukopenia (11% in FOLFIRI + Bev/5% in mFOLFOX6 + Bev), neutropenia (46%/35%), diarrhea (9%/5%), febrile neutropenia (5%/2%), peripheral neuropathy (0%/22%), and venous thromboembolism (6%/2%). The QoL assessed by FACT-C (TOI-PFC) and FACT/GOG-Ntx was favorable for FOLFIRI + Bev during 18 months.

CONCLUSION

FOLFIRI plus bevacizumab was non-inferior for PFS, compared with mFOLFOX6 plus bevacizumab, as the first-line systemic treatment for mCRC.

CLINICAL TRIALS NUMBER

UMIN000001396.

Cell type-specific ATP-activated responses in rat dorsal root ganglion neurons

1. The aim of our study is to clarify the relationship between expression pattern of P2X receptors and the cell type of male adult rat (Wistar) dorsal root ganglion (DRG) neurons. We identified the nociceptive cells of acutely dissociated DRG neurons from adult rats type using capsaicin sensitivity. 2. Two types of ATP-activated currents, one with fast, the other with slow desensitization, were found under voltage-clamp conditions. In addition, cells with fast but not slow desensitization responded to capsaicin, indicating that there was a relationship between current kinetics and capsaicin-sensitivity. 3. Both types of neurons were responsive to ATP and alpha, beta methylene-ATP (alpha,betameATP). The concentration of alpha,(beta)meATP producing half-maximal activation (EC50) of neurons with fast desensitization was less (11 microM) than that of neurons with slow desensitization (63 microM), while the Hill coefficients were similar. Suramin and pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid tetrasodium (PPADS) antagonized alpha,betameATP-induced currents in both types of neurons. 4. In situ hybridization revealed that small cells of the DRG predominantly expressed mRNAs of P2X3 and medium-sized cells expressed mRNAs of P2X2 and P2X3. In contrast, both of mRNAs were not detected in large cells of the DRG. 5. These results suggest that capsaicin-sensitive, small-sized DRG neurons expressed mainly the homomeric P2X3 subunit and that capsaicin-insensitive, medium-sized DRG neurons expressed the heteromultimeric receptor with P2X2 and P2X3.

Mechanisms underlying extracellular ATP-evoked interleukin-6 release in mouse microglial cell line, MG-5

Microglia play various important roles in the CNS via the synthesis of cytokines. The ATP-evoked production of interleukin-6 (IL-6) and its intracellular signals were examined using a mouse microglial cell line, MG-5. ATP, but not its metabolites, produced IL-6 in a concentration-dependent manner. Although ATP activated two mitogen-activated protein kinases, i.e. p38 and extracellular signal-regulated protein kinase, only p38 was involved in the IL-6 induction. However, the activation of p38 was not sufficient for the IL-6 induction because 2'- and 3'-O-(4-benzoylbenzoyl) ATP, an agonist to P2X7 receptors, failed to produce IL-6 despite the fact that it activated p38. Unlike in other cytokines in microglial cells, P2Y rather than P2X7 receptors seem to have a major role in the IL-6 production by the cells. The ATP-evoked IL-6 production was attenuated by Gö6976, an inhibitor of Ca(2+)-dependent protein kinase C (PKC). The P2Y receptor responsible for these responses was insensitive to pertussis toxin (PTX) and was linked to phospholipase C. Taken together, ATP acting on PTX-insensitive P2Y receptors activates p38 and Ca(2+)-dependent PKC, thereby resulting in the mRNA expression and release of IL-6 in MG-5. This is a novel pathway for the induction of cytokines in microglia.

Analysis of transforming activity of human synovial sarcoma-associated chimeric protein SYT-SSX1 bound to chromatin remodeling factor hBRM/hSNF2 alpha

Human synovial sarcoma has been shown to exclusively harbor the chromosomal translocation t(X;18) that produces the chimeric gene SYT-SSX. However, the role of SYT-SSX in cellular transformation remains unclear. In this study, we have established 3Y1 rat fibroblast cell lines that constitutively express SYT, SSX1, and SYT-SSX1 and found that SYT-SSX1 promoted growth rate in culture, anchorage-independent growth in soft agar, and tumor formation in nude mice. Deletion of the N-terminal 181 amino acids of SYT-SSX1 caused loss of its transforming activity. Furthermore, association of SYT-SSX1 with the chromatin remodeling factor hBRM/hSNF2 alpha, which regulates transcription, was demonstrated in both SYT-SSX1-expressing 3Y1 cells and in the human synovial sarcoma cell line HS-SY-II. The binding region between the two molecules was shown to reside within the N-terminal 181 amino acids stretch (aa 1--181) of SYT-SSX1 and 50 amino acids (aa 156--205) of hBRM/hSNF2 alpha and we found that the overexpression of this binding region of hBRM/hSNF2 alpha significantly suppressed the anchorage-independent growth of SYT-SSX1-expressing 3Y1 cells. To analyze the transcriptional regulation by SYT-SSX1, we established conditional expression system of SYT-SSX1 and examined the gene expression profiles. The down-regulation of potential tumor suppressor DCC was observed among 1,176 genes analyzed by microarray analysis, and semi-quantitative reverse transcription--PCR confirmed this finding. These data clearly demonstrate transforming activity of human oncogene SYT-SSX1 and also involvement of chromatin remodeling factor hBRM/hSNF2 alpha in human cancer.

Binding sites for pituitary adenylate cyclase activating polypeptide (PACAP): comparison with vasoactive intestinal polypeptide (VIP) binding site localization in rat brain sections

Pituitary adenylate cyclase activating polypeptide (PACAP) is structurally similar to vasoactive intestinal polypeptide (VIP). We investigated the characteristics and topographical distribution of [125I]PACAP binding sites compared with those of [125I]VIP binding sites in the rat brain. Radiolabeled PACAP and VIP showed highly specific binding to sections at the level of the dorsal hippocampus. The specific binding of [125I]PACAP was 10 times higher than that of [125I]VIP in hippocampal sections. [125I]PACAP binding was scarcely displaced by unlabeled VIP, while [125I]VIP binding was effectively displaced by unlabeled PACAP. Therefore, PACAP binding sites may reflect both PACAP specific binding sites and VIP/PACAP binding sites. However, the amount of VIP/PACAP binding sites was negligibly low. Autoradiography revealed that [125I]PACAP binding sites were dense in the piriform cortex, diagonal band, accumbens nucleus, anterior part of the striatum, hippocampal formation, habenular nucleus, lateral hypothalamic area, superior colliculus and dorsal raphe nucleus. Moderate to high labeling was observed in the medial septal nucleus, olfactory tubercle, caudal part of the striatum, most parts of the thalamus, supraoptic and periventricular hypothalamic nuclei, central gray, substantia nigra pars compacta, locus coeruleus, pontine reticular nucleus and cerebellum. Distribution pattern was remarkably different from that of [125I]VIP binding sites in the hippocampal formation, lateral hypothalamic area, substantia nigra pars compacta, pontine reticular nucleus and cerebellum. The present results suggest that PACAP may have a physiological role in the regulation of the central nervous system.

Molecular cloning of a novel polypeptide, DP5, induced during programmed neuronal death

To study the molecular mechanisms underlying neuronal programmed cell death (PCD), we performed differential display screening for genes, the expression of which was induced during PCD in the sympathetic neuron culture model deprived of NGF. We cloned a gene encoding a novel polypeptide (DP5) which consisted of 92 amino acids. DP5 polypeptide had no homology with any other known protein and contained no motif that would indicate its putative biochemical functions. DP5 mRNA levels peaked at 15 h after nerve growth factor withdrawal, concurrent with the time at which neurons were committed to die. The induction of DP5 gene expression was blocked when cell death was rescued by treatment with cycloheximide, KCl, or the cyclic AMP analogue CPTcAMP. Overexpression of the full-length DP5 in cultured sympathetic neurons was in itself sufficient to induce apoptosis. These results suggest that DP5 plays a role in programmed neuronal death.

Pituitary adenylate cyclase activating polypeptide provokes cultured rat chromaffin cells to secrete adrenaline

Pituitary adenylate cyclase activating polypeptide (PACAP) provoked the rat chromaffin cells to secrete adrenaline. Within 20 min, the amount of adrenaline secreted by PACAP (10(-8) M) was as much as that caused by acetylcholine (10(-4) M). PACAP, but not acetylcholine, induced a long-term (over 120 min) increase in secretion of adrenaline. PACAP also activated adenylate cyclase and elevated cytosolic Ca2+ concentration. Furthermore, we found immunoreactive PACAP and PACAP binding sites in the rat adrenal medulla. These results suggest that PACAP has an important role in stimulating secretion of adrenaline in the adrenal medulla.

Regional distribution of pituitary adenylate cyclase activating polypeptide (PACAP) in the rat central nervous system as determined by sandwich-enzyme immunoassay

We investigated endogenous levels of a novel peptide, pituitary adenylate cyclase activating polypeptide (PACAP), in the rat central nervous system. The amount of PACAP was measured by means of highly specific and sensitive sandwich-enzyme immunoassay. This assay system following HPLC analysis revealed that PACAP38 was a major portion of the total PACAP immunoreactivity and PACAP27 levels were negligibly low in the brain. Therefore, we measured the amount of PACAP38 in 62 regions punched out from frozen tissue sections. High amounts of PACAP38 were found in the lateral septal nucleus (intermediate part), diagonal band, central amygdaloid nucleus, several parts of the hypothalamus (suprachiasmatic, supraoptic, periventricular and arcuate nuclei), central gray, interpeduncular nucleus and dorsal raphe. The suprachiasmatic, paraventricular and periventricular hypothalamic nuclei showed the highest levels. A moderate amount of the peptide was observed in the lateral septal nucleus (dorsal part), medial septal nucleus, medial amygdaloid nucleus, thalamus (paraventricular, paratenial, central medial, ventromedial, reuniens and rhomboid nuclei), hypothalamus (lateral hypothalamic area and mammillary body), ventral tegmental area, interfascicular nucleus and in the locus coeruleus. Such a distribution of endogenous PACAP38 did not parallel the localization of PACAP binding sites which we had demonstrated recently. Moreover, the topographical distribution of PACAP38 observed in the present study differed from that of VIP which had been previously reported. The present results suggest that PACAP38 may have a neurotransmitter/neuromodulator role which is different from that of VIP in the central nervous system.

Identification of the urease operon in Helicobacter pylori and its control by mRNA decay in response to pH

We investigated the transcription of the urease gene cluster ureABIEFGH in Helicobacter pylori to determine the regulation of gene expression of the highly produced enzyme urease. Northern blot hybridization analysis demonstrated that cells of the wild-type strain grown in an ordinary broth had transcripts of ureAB, ureABI, ureI, ureIE' and ure'FGH, but cells of a ureI-disrupted mutant had only the ureAB transcript. When the wild-type cells were exposed to pH 8 for 30 min, very little mRNA was detected. However, when exposed to pH 6, a large amount of the ureIE" transcript, which was longer than the ureIE' transcript, together with the additional transcripts ureABIEFGH and ure'EFGH were detected. Rifampicin addition experiments demonstrated that urease mRNAs, and the ureIE' transcripts in particular, are more stable at pH 5.5 than at pH 7. In accord with these results, urease activity in the crude cell extract of the pH 5.5 culture was twice as much as that of the pH 7 culture, although the amounts of UreA and UreB detected by immunoblot analysis were similar. The transcription start point of ureI was identified by primer extension using a ureA promoter-deleted mutant, and a consensus sequence of RpoD-RNA polymerase was found in the ureI promoter. The 3' end of the ureIE" mRNA, determined using S1 nuclease mapping, revealed that the transcript is able to cover the majority of the ureE open reading frame (ORF) that might be sufficient for UreE activity. Based on the above results, we conclude that the urease gene cluster of H. pylori consists of two operons, ureAB and ureIEFGH, and that primary transcripts of the latter as well as the read-through transcript, ureABIEFGH, are cleaved to produce several species of mRNA. It has been suggested that the ureIEFGH operon is regulated post-transcriptionally by mRNA decay in response to environmental pH. We are tempted to speculate that the ureE" transcript present in acidic pH may contribute to produce an active product that can proceed the nickel incorporation to the active centre, the final step of urease biosynthesis.

PI 3-kinase gamma and protein kinase C-zeta mediate RAS-independent activation of MAP kinase by a Gi protein-coupled receptor

Receptors coupled to the inhibitory G protein Gi, such as that for lysophosphatidic acid (LPA), have been shown to activate MAP kinase through a RAS-dependent pathway. However, LPA (but not insulin) has now been shown to activate MAP kinase in a RAS-independent manner in CHO cells that overexpress a dominant-negative mutant of the guanine nucleotide exchange protein SOS (CHO-DeltaSOS cells). LPA also induced the activation of MAP kinase kinase (MEK), but not that of RAF1, in CHO-DeltaSOS cells. The RAS-independent activation of MAP kinase by LPA was blocked by inhibitors of phosphatidylinositol 3-kinase (PI3K) or by overexpression of a dominant-negative mutant of the gamma isoform of PI3K. Furthermore, LPA induced the activation of the atypical zeta isoform of protein kinase C (PKC-zeta) in CHO-DeltaSOS cells in a manner that was sensitive to wortmannin or to the dominant-negative mutant of PI3Kgamma, and overexpression of a dominant-negative mutant of PKC-zeta inhibited LPA-induced activation of MAP kinase. These observations indicate that Gi protein-coupled receptors induce activation of MEK and MAP kinase through a RAS-independent pathway that involves PI3Kgamma-dependent activation of atypical PKC-zeta.

Octopus rhodopsin. Amino acid sequence deduced from cDNA

The primary structure of rhodopsin from the octopus Paroctopus defleini has been determined by parallel analysis of the protein and corresponding cDNA. The amino acid sequence is most similar to the recently cloned Drosophila opsins. Similarities to bovine and human opsins are also evident. The transmembrane topology of octopus rhodopsin is discussed.

Faithful transcription initiation of fibroin gene in a homologous cell-free system reveals an enhancing effect of 5' flanking sequence far upstream

For the faithful initiation of transcription of exogenously added fibroin gene, a crude cellular extract was prepared from the posterior silk glands where fibroin gene is specifically transcribed. The faithful initiation was demonstrated by the assay with use of truncated fibroin gene templates and confirmed by nuclease S1 mapping. The transcription initiation of fibroin gene was detected also in the extract from the middle silk glands where fibroin gene is not transcribed, indicating that an expected suppression machinery for the gene was left behind during the extraction procedures. The promoter sequence of fibroin gene required in these homologous extracts (the nucleotide position -29 to +6) is the same as that in a heterologous HeLa cell extract. This result guarantees a limited usefulness of the HeLa cell extract in determining promotor sequence or analyzing general transcription machinery. In the homologous extracts, but not in the heterologous extract, however, it has been shown for the first time in vitro that the 5' flanking sequence upstream from -74 enhances the transcription initiation of fibroin gene. In addition, a remarkable fibroin gene preference in transcription over mouse beta globin and adenovirus 2 major late genes was observed in the homologous extracts. The fibroin gene preference is partly caused by the sequence element upstream from -74 of fibroin DNA.

Integrin-mediated tyrosine phosphorylation of SHPS-1 and its association with SHP-2. Roles of Fak and Src family kinases

SHPS-1 is a receptor-like glycoprotein that undergoes tyrosine phosphorylation and binds SHP-2, an Src homology 2 domain containing protein tyrosine phosphatase, in response to various mitogens. Cell adhesion to extracellular matrix proteins such as fibronectin and laminin also induced the tyrosine phosphorylation of SHPS-1 and its association with SHP-2. These responses were markedly reduced in cells overexpressing the Csk kinase or in cells that lack focal adhesion kinase or the Src family kinases Src or Fyn. However, unlike Src, focal adhesion kinase did not catalyze phosphorylation of the cytoplasmic domain of SHPS-1 in vitro. Overexpression of a catalytically inactive SHP-2 markedly inhibited activation of mitogen-activated protein (MAP) kinase in response to fibronectin stimulation without affecting the extent of tyrosine phosphorylation of focal adhesion kinase or its interaction with the docking protein Grb2. Overexpression of wild-type SHPS-1 did not enhance fibronectin-induced activation of MAP kinase. These results indicate that the binding of integrins to the extracellular matrix induces tyrosine phosphorylation of SHPS-1 and its association with SHP-2, and that such phosphorylation of SHPS-1 requires both focal adhesion kinase and an Src family kinase. In addition to its role in receptor tyrosine kinase-mediated MAP kinase activation, SHP-2 may play an important role, partly through its interaction with SHPS-1, in the activation of MAP kinase in response to the engagement of integrins by the extracellular matrix.

Differential activation of brain-derived neurotrophic factor gene promoters I and III by Ca2+ signals evoked via L-type voltage-dependent and N-methyl-D-aspartate receptor Ca2+ channels

Although the brain-derived neurotrophic factor (BDNF) gene is activated by the intracellular Ca(2+) signals evoked via Ca(2+) influx into neurons, little is known about how the activation of alternative BDNF gene promoters is controlled by the Ca(2+) signals evoked via N-methyl-d-aspartate receptors (NMDA-R) and L-type voltage-dependent Ca(2+) channels (L-VDCC). There is a critical range in the membrane depolarization caused by high K(+) concentrations (25-50 mm KCl) for effective BDNF mRNA expression and transcriptional activation of BDNF gene promoters I and III (BDNF-PI and -PIII, respectively) in rat cortical culture. The increase in BDNF mRNA expression induced at high K(+) was repressed not only by nicardipine, an antagonist for L-VDCC, but also by dl-amino-5-phosphonovalerate, an antagonist for NMDA-R, which was supported by the effects of antagonists on the Ca(2+) influx. Although the promoter activations at 25 and 50 mm KCl were different, BDNF-PIII was activated by either the Ca(2+) influx through NMDA-R or L-VDCC, whereas BDNF-PI was predominantly by the Ca(2+) influx through L-VDCC. Direct stimulation of NMDA-R supported the activation of BDNF-PIII but not that of BDNF-PI. Thus, the alternative BDNF gene promoters responded differently to the intracellular Ca(2+) signals evoked via NMDA-R and L-VDCC.

Tyrosine phosphorylation of p62(Dok) induced by cell adhesion and insulin: possible role in cell migration

Dok, a 62-kDa Ras GTPase-activating protein (rasGAP)-associated phosphotyrosyl protein, is thought to act as a multiple docking protein downstream of receptor or non-receptor tyrosine kinases. Cell adhesion to extracellular matrix proteins induced marked tyrosine phosphorylation of Dok. This adhesion-dependent phosphorylation of Dok was mediated, at least in part, by Src family tyrosine kinases. The maximal insulin-induced tyrosine phosphorylation of Dok required a Src family kinase. A mutant Dok (DokDeltaPH) that lacked its pleckstrin homology domain failed to undergo tyrosine phosphorylation in response to cell adhesion or insulin. Furthermore, unlike the wild-type protein, DokDeltaPH did not localize to subcellular membrane components. Insulin promoted the association of tyrosine-phosphorylated Dok with the adapter protein NCK and rasGAP. In contrast, a mutant Dok (DokY361F), in which Tyr361 was replaced by phenylalanine, failed to bind NCK but partially retained the ability to bind rasGAP in response to insulin. Overexpression of wild-type Dok, but not that of DokDeltaPH or DokY361F, enhanced the cell migratory response to insulin without affecting insulin activation of mitogen-activated protein kinase. These results identify Dok as a signal transducer that potentially links, through its interaction with NCK or rasGAP, cell adhesion and insulin receptors to the machinery that controls cell motility.

Plasmid DNAs directly injected into mouse brain with lipofectin can be incorporated and expressed by brain cells

In this study, we demonstrated that lipofectin-treated DNAs which were injected into mouse brain could be incorporated and expressed by brain cells. When L7RH-beta gal plasmid DNA harboring E. coli beta-galactosidase gene fused with the nuclear location signal of SV40 T-antigen gene was injected into brains of 1-week-old mice, cells whose nuclei appeared to be densely stained with the chromogenic substrate X-gal were detected in several portions of the brain till 9 days after injection. Injection of pMLV-CAT plasmid DNA which contains the E. coli chloramphenicol acetyltransferase (CAT) gene also resulted in cells immunoreactive to the anti-CAT antibody.