Synthesis of the extended phenacene molecules, [10]phenacene and [11]phenacene, and their performance in a field-effect transistor

The [10]phenacene and [11]phenacene molecules have been synthesized using a simple repetition of Wittig reactions followed by photocyclization. Sufficient amounts of [10]phenacene and [11]phenacene were obtained, and thin-film FETs using these molecules have been fabricated with SiO₂ and ionic liquid gate dielectrics. These FETs operated in p-channel. The averaged measurements of field-effect mobility, <μ>, were 3.1(7) × 10⁻² and 1.11(4) × 10⁻¹ cm² V⁻¹ s⁻¹, respectively, for [10]phenacene and [11]phenacene thin-film FETs with SiO₂ gate dielectrics. Furthermore, [10]phenacene and [11]phenacene thin-film electric-double-layer (EDL) FETs with ionic liquid showed low-voltage p-channel FET properties, with <μ> values of 3(1) and 1(1) cm² V⁻¹ s⁻¹, respectively. This study also discusses the future utility of the extremely extended π-network molecules [10]phenacene and [11]phenacene as the active layer of FET devices, based on the experimental results obtained.

Chemical analysis of superconducting phase in K-doped picene

Potassium-doped picene (K3.0picene) with a superconducting transition temperature (T C) as high as 14 K at ambient pressure has been prepared using an annealing technique. The shielding fraction of this sample was 5.4% at 0 GPa. The T C showed a positive pressure-dependence and reached 19 K at 1.13 GPa. The shielding fraction also reached 18.5%. To investigate the chemical composition and the state of the picene skeleton in the superconducting sample, we used energy-dispersive x-ray (EDX) spectroscopy, MALDI-time-of-flight (MALDI-TOF) mass spectroscopy and x-ray diffraction (XRD). Both EDX and MALDI-TOF indicated no contamination with materials other than K-doped picene or K-doped picene fragments, and supported the preservation of the picene skeleton. However, it was also found that a magnetic K-doped picene sample consisted mainly of picene fragments or K-doped picene fragments. Thus, removal of the component contributing the magnetic quality to a superconducting sample should enhance the volume fraction.

ZEB1 induces EPB41L5 in the cancer mesenchymal program that drives ARF6-based invasion, metastasis and drug resistance

Onset of the cancer mesenchymal program is closely associated with cancer malignancy and drug resistance. Among the different epithelial–mesenchymal transition (EMT)-associated transcriptional factors, ZEB1 has a key role in inducing the mesenchymal phenotypes and stem cell-like properties of different breast cancer cells. ARF6 and its effector AMAP1 are frequently overexpressed in breast cancer cells, and promote invasion, metastasis and drug resistance. EPB41L5 is induced during EMT, and mediates the disruption of E-cadherin-based cell–cell adhesion and the promotion of focal adhesion dynamics. Here we show that EPB41L5 is an integral component of the ARF6-based pathway, which is induced by ZEB1. We found that EPB41L5 is expressed at high levels in malignant breast cancer cells and binds to AMAP1. ZEB1 induced EPB41L5 both in cancer cells and normal cells. This relationship was recaptured with The Cancer Genome Atlas RNASeq data set, and correlated with the poor outcome of the patients. In contrast, diversified events, such as tumor growth factor β1 stimulation, expression of SNAI1 and TP53 mutation, can each cause the induction of ZEB1 and EPB41L5, depending on the cellular context. Our results demonstrated that the ZEB1-EPB41L5 axis is at the core of the cancer mesenchymal program that drives ARF6-based invasion, metastasis and drug resistance of significant populations of primary breast cancers, and is tightly correlated with the poor outcomes of patients.

FKBP12 functions as an adaptor of the Smad7-Smurf1 complex on activin type I receptor

The cytoplasmic immunophilin FKBP12, a 12 kDa FK506-binding protein, has been shown to act as an inhibitor for transforming growth factor-beta (TGF-beta) signaling. FKBP12 binds to the glycine- and serine-rich motif (GS motif) of the TGF-beta type I receptor, and functions as a secure switch to prevent the leaky signal. Upon stimulation with ligand, FKBP12 is released from the receptor to fully propagate the signal. We found that activin, a member of TGF-beta superfamily, also induced the dissociation of FKBP12 from the activin type I receptor (ALK4). However, we observed that the released FKBP12 associates again with the receptor a few hours later. FKBP12 also interacted with another inhibitory molecule of activin signal, Smad7, in an activin-dependent manner, and formed a complex with Smad7 on the type I receptor. FK506, a chemical ligand for FKBP12, which dissociates FKBP12 from the receptor, decreased the interaction between Smad7 and Smad ubiquitin regulatory factor 1 (Smurf1). FK506 also inhibited the ubiquitination of the type I receptor by Smurf1. These findings indicate a new inhibitory function of FKBP12 as an adaptor molecule for the Smad7-Smurf1 complex to regulate the duration of the activin signal.

Characterization of isoforms of activin receptor-interacting protein 2 that augment activin signaling

Activin type II receptors (ActRIIs) including ActRIIA and ActRIIB are serine/threonine kinase receptors that form complexes with type I receptors to transmit intracellular signaling of activins, nodal, myostatin and a subset of bone morphogenetic proteins. ActRIIs are unique among serine/threonine kinase receptors in that they associate with proteins having PSD-95, Discs large and ZO-1 (PDZ) domains. In our previous studies, we reported specific interactions of ActRIIs with two independent PDZ proteins named activin receptor-interacting proteins 1 and 2 (ARIP1 and ARIP2). Overexpression of both ARIP1 and ARIP2 reduce activin-induced transcription. Here, we report the isolation of two isoforms of ARIP2 named ARIP2b and 2c. ARIP2, ARIP2b and ARIP2c recognize COOH-terminal residues of ActRIIA that match a PDZ-binding consensus motif. ARIP2 and its isoforms have one PDZ domain in the NH2-terminal region, and interact with ActRIIA. Although PDZ domains containing GLGF motifs of ARIP2b and 2c are identical to that of ARIP2, their COOH-terminal sequences differ from that of ARIP2. Interestingly, unlike ARIP2, overexpression of ARIP2b or 2c did not affect ActRIIA internalization. ARIP2b/2c inhibit inhibitory actions of ARIP2 on activin signaling. ARIP2 is widely distributed in mouse tissues. ARIP2b/2c is expressed in more restricted tissues such as heart, brain, kidneys and liver. Our results indicate that although both ARIP2 and ARIP2b/2c interact with activin receptors, they regulate ActRIIA function in a different manner.

Synergistic activity of activin A and basic fibroblast growth factor on tyrosine hydroxylase expression through Smad3 and ERK1/ERK2 MAPK signaling pathways

Activin has previously been shown to act as a nerve cell survival factor and to have neurotrophic effects on neurons. However, the role of activin in regulating neurotransmitter expression in the central nervous system and the exact mechanisms involved in this process are poorly understood. In the present study, we report that activin A and basic fibroblast growth factor (bFGF) synergistically increased the protein level of tyrosine hydroxylase (TH), and also greatly increased the TH mRNA level, in both mouse E14 striatal primary cell cultures and the hippocampal neuronal cell line HT22. Activin A and bFGF cooperatively stimulated nuclear translocation of Smad3 and specifically activated ERK1/2, but not p38 or JNK. Interestingly, a specific inhibitor for MEK, U0126, efficiently blocked the induction of TH promoter activity by activin A and bFGF, indicating that activin A collaborated with bFGF signaling to induce the TH gene through selective activation of ERK-type MAP kinase in mouse striatal and HT22 cells. These data suggest that activin A may act in concert with bFGF for the development of TH-positive neurons.

Zinc-mediated carbon radical addition to glyoxylic imines in aqueous media for the synthesis of α-amino acids

The addition of carbon radicals to glyoxylic imines was studied using zinc dust as a radical initiator. The zinc-mediated radical reaction of glyoxylic oxime ethers and hydrazones proceeded smoothly to give the alkylated products via a carbon-carbon bond-forming process in aqueous media. The reaction of the oxime ethers and hydrazones having an Oppolzer's camphorsultam group provided the corresponding alkylated products, which could be converted into enantiomerically pure alpha-amino acids. The diastereoselectivities observed in the reaction of hydrazones were better than those obtained in the reaction of oxime ethers.

Assessment of the developmental totipotency of neural cells in the cerebral cortex of mouse embryo by nuclear transfer

When neural cells were collected from the entire cerebral cortex of developing mouse fetuses (15.5-17.5 days postcoitum) and their nuclei were transferred into enucleated oocytes, 5.5% of the reconstructed oocytes developed into normal offspring. This success rate was the highest among all previous mouse cloning experiments that used somatic cells. Forty-four percent of live embryos at 10.5 days postcoitum were morphologically normal when premature and early-postmitotic neural cells from the ventricular side of the cortex were used. In contrast, the majority (95%) of embryos were morphologically abnormal (including structural abnormalities in the neural tube) when postmitotic-differentiated neurons from the pial side of the cortex were used for cloning. Whereas 4.3% of embryos cloned with ventricular-side cells developed into healthy offspring, only 0.5% of those cloned with differentiated neurons in the pial side did so. These facts seem to suggest that the nuclei of neural cells in advanced stages of differentiation had lost their developmental totipotency. The underlying mechanism for this developmental limitation could be somatic DNA rearrangements in differentiating neural cells.

Role of adenosine in renal protection induced by a brief episode of ischemic preconditioning in rats

The protective effect of a brief episode of ischemic preconditioning was examined at an early phase of ischemic-reperfusion injury in the rat kidney. Rats were subjected to 50 min of left renal artery occlusion followed by 120 min of reperfusion. Ischemic preconditioned rats were subjected to preconditioning with two cycles of 3-min ischemia and 5-min reperfusion (IPC). Ischemic-reperfusion injury led to a low recovery of the glomerular filtration rate (GFR). Overt morphological changes, consisting of blood trapping and tubular collapse, were seen. IPC improved the recovery of GFR and renal morphology. The IPC effect was not blocked by 8-(p-sulfophenyl)-theophylline (SPT), a non-selective adenosine receptor antagonist, by 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), a selective A1-receptor antagonist, or by 3,7-dimethyl-1-propargylxanthine (DMPX), a selective A2-receptor antagonist. Intravenous infusion of adenosine (30 microg/min per rat, for 5 min) prior to the 50-min occlusion improved the recovery of GFR, and this protection of GFR was blocked by SPT. Thus, both IPC and exogenous adenosine attenuated ischemic-reperfusion injury of the kidney. However, because three adenosine receptor antagonists failed to abolish the protective effect of IPC, there is no evidence to indicate that activation of adenosine receptors contributes to the IPC effect in the kidney.

Possible involvement of protein kinases and Smad2 signaling pathways on osteoclast differentiation enhanced by activin A

Bone tissues reportedly contain considerable amounts of activin A and follistatin, an activin A-binding protein. In the present study, we found that follistatin strongly inhibited osteoclast formation in cocultures of mouse bone marrow cells and primary osteoblasts induced by 1alpha,25 dihydroxyvitamin D(3), prostaglandin E(2), and interleukin-1alpha. Antibody aganist activin A also inhibited the osteoclast formation. Furthermore, activin A synergistically stimulated osteoclast differentiation mediated by receptor activator NF-kappaB ligand (RANKL). RT-PCR analysis revealed that osteoblasts produced not only activin A but also follistatin. Western blot analysis of a panel of phosphorylated proteins revealed that activin A stimulated the phosphorylation of p44/42 mitogen activated protein (MAP) kinase (ERK1/2) and p38 MAP kinase in macrophage colony-stimulating factor-dependent bone marrow macrophages (M-BMMPhis). In addition, phosphorylation of Smad2 was observed in M-BMMPhis stimulated with activin A. These findings indicate that the phosphorylation of p44/42 MAP kinase, p38 MAP kinase, and Smad2 is involved in activin A-enhanced osteoclast differentiation induced by RANKL. Taken together, these results suggest that both activin A and follistatin produced by osteoblasts may play an important role in osteoclast differentiation through MAP kinases and Smad2 signaling pathways.

Intracellular and extracellular control of activin function by novel regulatory molecules

Activin signal transduction is regulated through multiple mechanisms. We have identified novel regulatory proteins that control activin functions either intracellularly or extracellularly. As intracellular molecules, PSD-95/Dlg/ZO-1 (PDZ) proteins that specifically associate with activin type II receptors (ActRIIs) were identified. We have named the molecules as activin receptor-interacting proteins (ARIPs). ARIP1 has two WW domains and five PDZ domains, associates not only with ActRIIs but also with Smads, and controls activin functions intracellularly in neuronal cells. Another ARIP we have found has only one PDZ domain, and is likely to be involved in intracellular trafficking and sorting of activin receptor complexes in the cell. As an extracellular regulatory protein, we have identified a novel follistatin-like protein, named follistatin-related gene (FLRG). Like follistatins, FLRG binds activins and bone morphogenetic proteins (BMPs) and controls their functions extracellularly. The mode of association of follistatin and FLRG with activins and their expression patterns are different, suggesting the distinct functions of follistatin and FLRG in vivo.

Apoptosis is not increased in myocardium overexpressing type 2 angiotensin II receptor in transgenic mice

To determine whether angiotensin type 2 (AT(2)) receptor stimulation induces apoptosis in cardiomyocytes in vivo, we developed transgenic mice overexpressing the AT(2) receptor in a cardiac-specific manner, using the alpha-myosin heavy-chain promoter. Ten- to 12-week-old male homozygous transgenic mice (n=44) and wild-type mice (n=44) were used. Both transgenic and wild-type mice were given either saline (control), a subpressor dose of angiotensin II (100 ng. kg(-1). min(-1)), a pressor dose of angiotensin II (1000 ng. kg(-1). min(-1)) for 14 days, a pressor dose of angiotensin II for 28 days to investigate the effects of stimulation on both angiotensin type 1 (AT(1)) and AT(2) receptors, the AT(1) antagonist L158809 alone, or a combination of angiotensin II (1000 ng. kg(-1). min(-1)) and L158809 for 14 days to investigate the effects of selective AT(2) receptor stimulation. Apoptosis was analyzed in paraffin-embedded ventricular sections by the terminal deoxynucleotidyl-transferase-mediated dUTP nick-end labeling (TUNEL) technique. In both transgenic and wild-type mice, administration of a subpressor dose of angiotensin II, L158809, or a combination of angiotensin II and L158809 did not significantly affect the tail-cuff blood pressure or heart-to-body weight ratio, whereas administration of a pressor dose of angiotensin II for 14 or 28 days significantly increased blood pressure and the heart-to-body weight ratio. However, there was no statistical difference between the effects of angiotensin II in transgenic and wild-type mice. The number of TUNEL-positive nuclei was approximately 0 to 10 per 100 000 cardiomyocytes, with no difference between transgenic and wild-type mice, regardless of saline infusion or any stimulation. In infarcted canine myocardial tissue sections for positive control, the number of TUNEL-positive nuclei was increased by 13.8 to 19.1 times compared with those in the noninfarcted myocardium. In conclusion, angiotensin II infusion for a period of 28 days failed to induce cardiomyocyte apoptosis regardless of the presence or absence of cardiac AT(2) receptor overexpression. It is unlikely that in mice the AT(2) receptor is a strong signal to induce cardiomyocyte apoptosis in vivo.

Two novel CNRs from the CNR gene cluster have molecular features distinct from those of CNR1 to 8

Cadherin-related neuronal receptor (CNR) family proteins are known as synaptic cadherins and Reelin receptors. Here we have identified two novel mouse CNR genes, CNRc1 and CNRc2, orthologues of human protocadherin (Pcdh) alpha-c1 and Pcdhalpha-c2, respectively. While the variable large exons of CNRc1 and c2 contain six conserved extracellular cadherin repeats (EC1-6) and are linked to the constant exons, both contain several molecular features distinct from CNR1-8. CNRc1 and c2 lack the Arg-Gly-Asp (RGD) sequence that is conserved in the EC1 of CNR1-8, which is necessary for binding to Reelin. The present studies confirm that CNRc1 and c2 failed to immunoprecipitate with Reelin. In addition, the regulation of novel CNR expression patterns during brain development is slightly different from that of CNR1. The identification of these new CNR genes characterized by their distinct extracellular function and expression is indicative of the novel diversity of the processes of brain structuring and synapse regulation.

Somatic mutations of synaptic cadherin (CNR family) transcripts in the nervous system

BACKGROUND

Cadherin-related neuronal receptor (CNR) family genes have been identified in the nervous system by screening molecules bound to Fyn-tyrosine kinase. The CNR family is comprised of diverse synaptic cadherins. The genomic organization of the CNR genes, composed of variable and constant regions, is similar to that of the immunoglobulin gene cluster. The nervous system is characterized by the acquisition of diverse function. This feature is similar to the immune system. In the immune system, the generation and selection of immunoglobulin gene mutants is the underlying basis for acquired immunity. We therefore examined somatic regulation of the CNR family genes in the nervous system to determine whether a similar mechanism controls nervous system development.

RESULTS

We first demonstrated that approximately 10% of the CNR3 transcripts were trans-transcripts between the variable and constant exons at the adult stage. Furthermore, somatic mutations of CNR3 transcripts accumulated during brain development, with a marked bias for A-to-G and U-to-C transitions. Approximately 70% of the CNR3 transcripts exhibited a mutation characterized by the addition of a CU-repeat; these transcripts contained seven continuous CU-repeats in the 3' untranslated region at the adult stage, whereas the CNR genomic DNA contained six continuous CU-repeats. Interestingly, a high rate of replacement mutations was detected in the first cadherin domain that functions in acquisition of specificity for cell adhesion in cadherins, while in the other regions the occurrence of silent mutations increased during development.

CONCLUSION

The present report is the first description of the generation and possible selection of somatic mutations of synaptic cadherin transcripts. The somatic alterations of CNR family transcripts and their synaptic localization have interesting implications for the molecular basis underlying the establishment of somatic rearrangement of neuronal networks.

Is compensatory vasoconstrictor tone in the hindquarter vascular region induced by hemorrhage in conscious spontaneously hypertensive rats?

We investigated whether a compensatory vasoconstrictor action would be induced by a hypotensive intervention in the hindquarter vascular region of conscious spontaneously hypertensive rats (SHRs). Mean arterial pressure and hindquarter blood flow were recorded. After hemorrhage (withdrawing blood, 0.3 ml/100 g body weight), hindquarter resistance (HQR) was increased significantly. The decrease in HQR induced by the administration of a ganglionic blocker (C6; 25 mg/kg, i.v.) was significantly greater in SHRs with hemorrhage than in those without hemorrhage. The present results suggest that a detectable hindquarter compensator tone occurs due to hemorrhage in SHRs, although an abnormal substantial vasoconstrictor tone already exists in the hindquarters.

Identification and characterization of a novel follistatin-like protein as a binding protein for the TGF-beta family

Follistatin is an activin-binding protein that prevents activin from binding to its receptors and neutralizes its activity. Follistatin also binds bone morphogenetic proteins (BMPs). In this study, we report the identification of a novel follistatin-like protein from mouse. The mouse cDNA encodes a 256-residue precursor and most likely a mouse homologue of human FLRG, which was found at the breakpoint of the chromosomal rearrangement in a B-cell line. Whereas follistatin has three follistatin domains, which are presumed to be growth factor binding motifs, FLRG possesses only two follistatin domains. Northern blotting revealed that mRNAs for FLRG were abundantly expressed in heart, lung, kidney, and testis in mouse. The recombinant mouse FLRG proteins were found to have binding activity for both activin and bone morphogenetic protein-2. Like follistatin, FLRG has higher affinity for activin than for BMP-2. The FLRG protein inhibited activin-induced and BMP-2-induced transcriptional responses in a dose-dependent manner. Glutathione S-transferase fusion proteins encoding various regions of FLRG were produced and studied. Ligand blotting using (125)I-activin revealed that the COOH-terminal region containing the second follistatin domain was able to bind activin. Our finding implies that cellular signaling by activin and BMPs is tightly regulated by multiple members of the follistatin family.

Difference between follistatin isoforms in the inhibition of activin signalling: activin neutralizing activity of follistatin isoforms is dependent on their affinity for activin

We demonstrate the difference between the follistatin isoforms (FS-288 and FS-315), two activin-binding proteins, in the neutralizing activity for activin signalling. Transcriptional reporter assay using 3TP-Lux, an activin-responsive reporter construct, showed that the inhibitory effect of FS-288 on activin-induced transcriptional response is more potent than that of FS-315. The potency was not influenced by the presence of heparan sulfates, by which FS, in particular FS-288, associates with cell surfaces at a high affinity. Furthermore, FS-288 inhibited the binding of activin to its type II receptor more markedly than did FS-315, as evidenced by surface plasmon resonance and affinity cross-linking experiments. Moreover, the Kd of FS-288 and FS-315 for activin A was estimated to be 46.5+/-0.37 pM and 432+/-26 pM, respectively, by surface plasmon resonance experiments. These results indicate that the different potency between the two FS isoforms in the inhibition of activin activities depends on their affinity for activin A.

Expression of a TGF-beta1 inducible gene, TSC-36, causes growth inhibition in human lung cancer cell lines

TSC-36 (TGF-beta1-stimulated clone 36) is a TGF-beta1 inducible gene whose product is an extracellular glycoprotein that contains a single follistatin module. TSC-36 is highly expressed in the lung, but its physiological function is unknown. In an attempt to elucidate it, we investigated the effect of TSC-36 on proliferation of human lung cancer cell lines. We found a correlation between expression of TSC-36 and cell growth: TSC-36 mRNA was not detected in cells derived from small cell lung cancer (SCLC) cells, a highly aggressive neoplasm, but was detected in some non-small cell lung cancer (NSCLC) cells, a moderately aggressive neoplasm. This suggested an antiproliferative function for TSC-36. To address this question, NSCLC PC-14 cells, which express very low level of TSC-36 protein, were transfected with TSC-36 cDNA and the proliferative capacity of stable transfectants was determined by measuring the doubling time, colony forming activity in soft agar and the level of incorporation of (3)H-thymidine into DNA. Under normal culture conditions, the transfected cells showed a longer doubling time, lower plating efficiency and lower rate of DNA synthesis than the parental cells and the control neo transfectant cells. These findings suggested that expression of TSC-36 caused growth inhibition in human lung cancer cells.

Chemical structure of nuclear proteins which are phosphorylated during meiotic maturation of starfish oocytes

Oocytes of the starfish, Asterina pectinifera, are arrested at the G2 phase of meiosis I and possess a prominent germinal vesicle in which maternal stores of nuclear proteins which are destined for use primarily by the early embryo are stored. Germinal vesicle breakdown and subsequent oocyte maturation is triggered by activation of the p34(cdc2)/cyclin B complex, which is present as the preform in the cytoplasm. The aim of the present study was to identify and biochemically characterize in vivo substrates of the kinase. Two nucleic acid binding nuclear proteins designated NAAP1 and NAAP2 were found, both of which contain 345 amino acid residues with pI 3. 6 and which serve as substrates. The only difference between the two proteins was in the primary amino acid sequence at position 51, which is Asn in NAAP1 but Thr in NAAP2. NAAPs are phosphorylated in vivo during oocyte maturation but not at the meiotic G(2) stage. NAAPs are phosphorylated in vitro by the cdc2 kinase on the same site as in vivo. Although there are other evolutionarily conserved consensus sequences for phosphorylation by mitotically active cdc2 kinase in NAAPs and NAAP-derived fragments containing the sequences were efficiently phosphorylated in vitro, these sites in the intact NAAPs were not phosphorylated either in vivo or in vitro. These results suggest that the tertiary structure of NAAPs affects the target specificity of the cdc2 kinase.

Effect of activin on production and secretion of prolactin and growth hormone in cultured rat GH3 cells

OBJECTIVE

To evaluate the effect of the growth factor activin A on the secretion of prolactin (PRL) and GH in cultured GH3 cells.

METHODS

The concentrations of PRL and GH secreted from GH3 cells cultured in media with and without activin A were measured by RIA, and the expression of PRL mRNA and GH mRNA were analyzed using the Northern blot method.

RESULTS

Activin A significantly inhibited PRL release from GH3 cells cultured for 48h in a dose-dependent manner (activin: 0.3-3nM). The inhibitory effects of 3nM activin A were observed in the culture from 12h to 48h (53.2% of control). Activin A (3nM) also significantly inhibited the expression of PRL mRNA at 24h (33.8% of control). In contrast, activin A significantly stimulated GH release from GH3 cells cultured for 48h in a dose-dependent manner (activin: 0.3-3nM). The stimulatory effect of 3nM activin A was observed in the culture for 48h (157.6% of control). Activin A (3nM) also significantly stimulated the expression of GH mRNA at 24h (183.6% of control). In spite of these significant changes in PRL and GH secretion, pit-1 mRNA levels were not significantly changed by activin A.

CONCLUSIONS

These findings indicated that activin A modulates PRL and GH secretion through the regulation of PRL and GH gene transcription in GH3 cells, but that these effects are unrelated to pit-1 gene expression.

Activin promotes astrocytic differentiation of a multipotent neural stem cell line and an astrocyte progenitor cell line from murine central nervous system

The effects of activin A were investigated on the development of a multipotent neural stem cell line (MEB5) and an astrocyte progenitor cell line (AP-16) that were established from murine central nervous system (CNS). Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis demonstrated that each cell line expresses both type I and type II activin receptors and signaling molecules for activin, Smad2, Smad3, and Smad4. Activin A did not affect the proliferation of MEB5 and AP-16 cells. When each cell line was treated alone with activin A, glial fibrillary acidic protein (GFAP), a marker for astrocytes, was induced in AP-16 cells, but not in MEB5 cells. However, activin A accelerated the leukemia inhibitory factor (LIF)-induced astroglial differentiation of MEB5 cells. These results suggest that activin promotes astrocyte differentiation of CNS neural progenitors, and the competence to activin is different between multipotent stem cells and unipotent astrocyte progenitor cells.

Identification of two polyketide synthase gene clusters on the linear plasmid pSLA2-L in Streptomyces rochei

The 200kb linear plasmid pSLA2-L was suggested to be involved in the production of two macrolide antibiotics, lankamycin (Lm) and lankacidin (Lc), in Streptomyces rochei 7434AN4. Hybridization experiments with the polyketide synthase (PKS) genes for erythromycin and actinorhodin identified two eryAI-homologous regions and an actI-homologous region on pSLA2-L. The nucleotide sequence of a 3.6kb SacI fragment carrying one of the eryAI-homologs revealed that it codes for part of a large protein with four domains for ketoreductase, acyl carrier protein, ketosynthase, and acyltransferase. Gene disruption confirmed that the two eryAI-homologs are parts of a large type-I PKS gene cluster for Lm. A 4.8kb DNA carrying the actI-homologous region contains four open reading frames (ORF1-ORF4) as well as an additional ORF, i.e. ORF5, which might code for a thioesterase. Deletion of the ORF2-ORF4 region showed that it is not involved in the synthesis of Lm or Lc. Thus, it was confirmed that pSLA2-L contains two PKS gene clusters for Lm and an unknown type-II polyketide.

Activin A stimulates insulin secretion in cultured human pancreatic islets

Activin A is a dimeric glycoprotein showing a high sequence homology with transforming growth factor-beta (TGF-beta) and playing autocrine/paracrine actions in reproductive tissues. However, since the synthesis of activin is ubiquitous it may have a role in regulating cell growth and differentiation in several tissues. Previous studies showed that activin A is expressed by insulin-positive B cells of human pancreatic islets, and women with gestational diabetes have higher serum activin A levels than healthy pregnant women at the same gestational age. The present study aimed to evaluate the effect of activin A on insulin secretion from cultured human pancreatic islets. With this purpose human pancreatic islets were incubated with varying concentrations of activin A (0.1 to 10.0 nM). In absence of glucose, activin A did not modify insulin secretion at the different concentrations used. In absence of activin A, 8.3 mM and 16.7 mM glucose significantly increased insulin secretion, with a dose-dependent pattern. In presence of a non stimulatory concentration of glucose (3.3 mM), activin A significantly increased insulin secretion starting from low concentration (0.1 nM). Furthermore, the addition of activin A to 8.3 mM and 16.7 mM glucose induced an additional effect of the dose-dependent glucose-mediated insulin secretion (p<0.001). The present data could support a role for activin A in human endocrine pancreas in modulating insulin response to different glucose concentrations.

Expression patterns of follistatin and two follistatin-related proteins during mouse development

We compared the expression patterns of follistatin and two follistatin-related proteins (FRP and m7365) during early mouse development. m7365 is expressed continuously during preimplantation development, in contrast to FRP and follistatin. At early postimplantation stages, follistatin and 7365 are expressed from E6.0, while FRP is detected from E7.5 onwards. Although there is some overlap between the expression of these genes in the primitive streak and somites, their overall expression patterns are distinct.

Identification and characterization of a PDZ protein that interacts with activin type II receptors

We have identified a mouse PDZ protein that interacts with the activin type IIA receptor (ActRIIA), which we named activin receptor-interacting protein 1 (ARIP1). By using yeast two-hybrid screening, we isolated a cDNA clone of ARIP1 from a mouse brain cDNA library. We detected two forms of ARIP1, ARIP1-long and ARIP1-short, which may be produced by alternative splicing. ARIP1-long had one guanylate kinase domain in the NH(2)-terminal region, followed by two WW domains and five PDZ domains (PDZ1-5). ARIP1-short had a deletion in the NH(2)-terminal region and lacked the guanylate kinase domain. Both forms interacted with ActRIIA through PDZ5. The COOH-terminal residues of ActRIIA (ESSL) agree with a PDZ-binding consensus motif, and ARIP1 recognized the consensus sequence. ARIP1 interacts specifically with ActRIIA among the receptors for the transforming growth factor beta family. Interestingly, ARIP1 also interacted with Smad3, which is an activin/transforming growth factor beta intracellular signaling molecule. The mRNA of ARIP1 was more abundant in the brain than in other tissues. Overexpression of ARIP1 controls activin-induced and Smad3-induced transcription in activin-responsive cell lines. These findings suggest that ARIP1 has a significant role in assembling activin signaling molecules at specific subcellular sites and in regulating signal transduction in neuronal cells.

Genomic organization of the family of CNR cadherin genes in mice and humans

The cadherin-related neuronal receptor (CNR) family is localized to the synaptic junction, and their cytoplasmic domains interact with Fyn-tyrosine kinase. Here, we describe the chromosomal locations and the orthologous genomic structures of CNR family members in mice and humans. In the genomic organization, distinct exons, each of which encodes the N-terminus of a different CNR ("variable region"), are clustered in a tandem array, and these exons are spliced to a common region composed of three exons ("constant region"). We also discovered three alternative versions of the transcripts; a single variable exon connects with three different C-terminal tails, comparable to class-switching in the immunoglobulin heavy chain. Thus the CNR family in the central nervous system has similarities to the immunoglobulin and T-cell receptor genes in the immune system.

Molecular characterization of a novel nucleolar protein in starfish oocytes which is phosphorylated before and during oocyte maturation

In response to 1-methyladenine, a maturation-inducing substance, starfish oocytes undergo reinitiation of meiosis with germinal vesicle breakdown through activation of p34cdc2-cyclin B, which results in the dispersal of the nucleolus. Little information has been elucidated thus far on nucleolar proteins that are phosphorylated by p34cdc2-cyclin B during meiotic maturation. Here, we describe a novel nucleolar protein of the starfish Asterina pectinifera oocyte, which is designated ANO39 and which is phosphorylated during meiotic maturation. A full-length ANO39 cDNA of 2106 base pairs encodes a polypeptide of 346 amino acids having a calculated Mr of 39 005. The amount of ANO39 is kept nearly constant during oocyte maturation and embryogenesis up to the midgastrula stage. The transcript encoding ANO39 was present in growing oocytes but not in full-grown ones, as evidenced by Northern blot hybridization. Ser145 is specifically phosphorylated when ANO39 is incubated in vitro with purified starfish p34cdc2-cyclin B. This phosphorylation site corresponds to that is phosphorylated during meiotic maturation in vivo. Immunoblot analysis using phosphoserine145-specific antibody as a probe revealed that some populations of ANO39 of the immature oocytes at the G2 stage have been already phosphorylated on Ser145 and Ser145 is maximally phosphorylated during meiotic maturation.

Effects of activin on hormone secretion by single female rat pituitary cells: analysis by cell immunoblot assay

We investigated the effect of activin A on secretion of LH, FSH, and prolactin (PRL) by female cultured rat pituitary cells at the single-cell level by means of the cell immunoblot assay. Anterior pituitary cells from 8-week-old female rats were preincubated with or without activin A for 24 h, after which they were monodispersed and immediately used for cell immunoblot assay. The percentages of LH-, FSH- and PRL-immunoreactive cell blots detected were 5.5, 5.3 and 43.1%, respectively, of all pituitary cells applied to the transfer membrane. The percentage of LH-secreting cells and mean LH secretion per cell did not change after treatment with activin. In contrast, activin significantly increased the percentage of FSH-secreting cells and mean FSH secretion per cell to 136.0 and 114. 5% respectively. In addition, activin significantly decreased the percentage of PRL-secreting cells and mean PRL secretion per cell to 52.2 and 72.0% respectively. These results suggest that (1) activin A has effects on female rat pituitary cells that increase not only the amount of FSH secretion per cell but also the number of FSH-secreting cells, and (2) activin A decreases both the amount of PRL secretion per cell and the number of PRL-secreting cells.

Differential inhibition of Smad6 and Smad7 on bone morphogenetic protein- and activin-mediated growth arrest and apoptosis in B cells

Smad6 and Smad7 prevent ligand-induced activation of signal-transducing Smad proteins in the transforming growth factor-beta family. Here we demonstrate that both Smad6 and Smad7 are human bone morphogenetic protein-2 (hBMP-2)-inducible antagonists of hBMP-2-induced growth arrest and apoptosis in mouse B cell hybridoma HS-72 cells. Moreover, we confirmed that the ectopic expressions of Smad6 and Smad7 inhibited the hBMP-2-induced Smad1/Smad5 phosphorylation. We previously reported that Smad7 is an activin A-inducible antagonist of activin A-induced growth arrest and apoptosis in HS-72 cells. Interestingly, although mRNA expression of Smad6 was induced by activin A in HS-72 cells, Smad6 showed no antagonistic effect on activin A-induced growth arrest and apoptosis. Moreover, we found that the ectopic expression of Smad7, but not Smad6, inhibited the activin A-induced Smad2 phosphorylation in HS-72 cells. Thus, Smad6 and Smad7 exhibit differential inhibitory effects in bone morphogenetic protein-2- and activin A-mediated signaling in B lineage cells.

cDNA cloning and distribution of the Xenopus follistatin-related protein

Recently, several proteins which have a follistatin module have been isolated. One of them, the follistatin-related protein (FRP), is encoded by TSC-36 (TGF-beta-stimulated clone 36) in mouse, originally isolated as a cDNA clone up-regulated by TGF-beta1 in mouse osteogenic MC3T3E1 cells. To determine the physiological role of FRP in early Xenopus embryonic development, we cloned the Xenopus FRP (xFRP) cDNA. The resulting cDNA clone was a secreted glycoprotein consisting of 299 amino acid residues with about 70% similarity to the mammalian and avian FRPs. Northern blotting analysis revealed that xFRP gene expression started at stage 10, the onset of gastrulation, gradually increased during the blastula and neurula stages and was sustained through the tail-bud stage. Whole-mount in situ hybridization analysis showed the localization of xFRP mRNAs in the Spemann organizer, notochord, neural floor plate, hypochord and somite. The similarities with the pattern of expression of Xenopus follistatin mRNA suggests that xFRP may play a role in neuralization.

The role of activin type I receptors in activin A-induced growth arrest and apoptosis in mouse B-cell hybridoma cells

Activins transduce their signals by binding to activin type I receptors and activin type II receptors, both of which contain a serine/threonine kinase domain. In this study, we established stable transfectants expressing two types of activin receptors, ActRI and ActRIB, to clarify the role of these receptors in activin signalling for growth inhibition in HS-72 mouse B-cell hybridoma cells. Over-expression of ActRI suppressed activin A-induced cell-cycle arrest in the G1 phase caused by inhibition of retinoblastoma protein phosphorylation through induction of p21CIP1/WAF1, a cyclin-dependent kinase inhibitor, and subsequent apoptosis. In contrast, HS-72 clones that over-expressed ActRIB significantly facilitated activin A-induced apoptosis. These results indicate that ActRI and ActRIB are distinct from each other and that the ActRI/ActRIB expression ratio could regulate cell-cycle arrest in the G1 phase and subsequent apoptosis in HS-72 cells induced by activin A.

Direct binding of follistatin to a complex of bone-morphogenetic protein and its receptor inhibits ventral and epidermal cell fates in early Xenopus embryo

In early development of Xenopus laevis, it is known that activities of polypeptide growth factors are negatively regulated by their binding proteins. In this study, follistatin, originally known as an activin-binding protein, was shown to inhibit all aspects of bone morphogenetic protein (BMP) activity in early Xenopus embryos. Furthermore, using a surface plasmon resonance biosensor, we demonstrated that follistatin can directly interact with multiple BMPs at significantly high affinities. Interestingly, follistatin was found to be noncompetitive with the BMP receptor for ligand binding and to form a trimeric complex with BMP and its receptor. The results suggest that follistatin acts as an organizer factor in early amphibian embryogenesis by inhibiting BMP activities by a different mechanism from that used by chordin and noggin.

Hypoplasia of pancreatic islets in transgenic mice expressing activin receptor mutants

Activin, a member of the TGF-beta superfamily, regulates the growth and differentiation of a variety of cell types. Based on the expression of activin in pancreatic rudiments of rat embryos and stimulation of insulin secretion from adult rat pancreatic islets by activin, activin is implicated in the development and function of islets. To examine the significance of activin signaling in the fetal and postnatal development of islets, transgenic mice expressing a dominant negative form of activin receptor (dn-ActR) or a constitutively active form of activin receptor (ActR-T206D) in islets were generated together with the transgenic mice expressing intact activin receptor (intact ActR) as a negative control. Transgenic mice with both dn-ActR and ActR-T206D showed lower survival rates, smaller islet area, and lower insulin content in the whole pancreas with impaired glucose tolerance when compared with transgenic mice with intact ActR or littermates, but they showed the same alpha cell/beta cell ratios as their littermates. In addition to islet hypoplasia, the insulin response to glucose was severely impaired in dn-ActR transgenic mice. It is suggested that a precisely regulated intensity of activin signaling is necessary for the normal development of islets at the stage before differentiation into alpha and beta cells, and that activin plays a role in the postnatal functional maturation of islet beta cells.

Activin A regulates the production of mature interleukin-1beta and interleukin-1 receptor antagonist in human monocytic cells

Activin A, a member of the transforming growth factor-beta (TGF-beta) family, is produced by a variety of cells and implicated in the regulation of the reproductive endocrine system, mesoderm induction, and erythropoiesis. In the present study, we showed that activin A inhibited the production of interleukin-1beta (IL-1beta), a potent proinflammatory cytokine, and enhanced the production of IL-1 receptor antagonist (IL-1ra), in activated THP-1 and U-937 human monocytic cells, resulting in the reduction of IL-1 biologic activity. Northern blot analysis revealed that activin A had no effect on mRNA accumulation of IL-1beta and IL-1ra, indicating that activin A regulates IL-1beta and IL-1ra production at a posttranscriptional level. As it is well known that an inactive precursor form of IL-1beta (pro-IL-1beta) is converted to an active mature form (mature IL-1beta), we examined the expression levels of pro-IL-1beta and mature IL-1beta by immunoblot analysis. Although activin A inhibited the production of mature IL-1beta in activated U-937 cells, the relative protein expression of pro-IL-1beta was unaltered by activin A, suggesting that activin A inhibits IL-1beta production by blocking proteolytic conversion of pro-IL-1beta into mature IL-1beta. Taken together, these findings suggest that activin A may function as an anti-inflammatory cytokine by modulating mature IL-1beta and IL-1ra production in inflammatory sites.

Correlation between Bcl-X expression and B-cell hybridoma apoptosis induced by activin A

In this study, we examined the role of bcl-XL and bcl-XS in apoptotic cell death of HS-72 cells induced by activin A. Immunoblot analysis revealed that a band of Bcl-XL was detected in HS-72 cells cultured with or without activin A. Although untreated HS-72 cells did not express Bcl-XS, the expression of Bcl-XS was significantly increased when cultured with activin A. We also investigated the expression of Bcl-XS and Bcl-XL in HS-72 cells cultured with activin A in the presence of protein kinase C inhibitor 1-(5-isoquinotinesulfonyl)-2-methylpiperazine dihydrochloride (H7), which suppressed apoptosis in HS-72 cells induced by activin A. Exposure to H7 apparently increased the level of Bcl-XL in HS-72 cells cultured with or without activin A. In contrast, no detectable band of Bcl-XS was found in HS-72 cells cultured with activin A and H7. These findings indicate that Bcl-XL upregulation and Bcl-XS downregulation induced by H7 might correlate with the suppression of activin A-induced apoptosis in B-lineage cells.

Identification of a novel type II activin receptor, type IIA-N, induced during the neural differentiation of murine P19 embryonal carcinoma cells

We have identified a novel type II activin receptor, called type IIA-N, the expression of which was induced during the neural differentiation of murine P19 embryonal carcinoma cells (P19 cells). P19 cells differentiate into several cell types dependent on the culture conditions. The induction of type IIA-N mRNA occurred predominantly in conjunction with neural differentiation. Sequence analysis of a cDNA clone for type IIA-N indicated that type IIA-N had a 24 bp insertion in the juxtamembrane region of the type IIA activin receptor suggesting that it is an alternative splicing product of the type IIA gene. Type IIA-N was also identified in human and Xenopus, and the amino acid sequences of three species were completely conserved. The expression of type IIA-N mRNA was specifically detected in neuroblastoma cells among several activin responsive cell lines. In vivo expression of type IIA-N mRNA was detected only in the neural tissues such as brain and spinal cord in adult mouse, by RT-PCR. Furthermore, its expression in developing Xenopus embryos was restricted to the neurula and later stages. These results suggest that the expression of type IIA-N is specific to neural cells and mediates neural differentiation-specific activin signaling.

Molecular characterization of Xenopus embryo heparan sulfate. Differential structural requirements for the specific binding to basic fibroblast growth factor and follistatin

Enzymatic elimination of heparan sulfate (HS) causes abnormal mesodermal and neural formation in Xenopus embryos, and HS plays an indispensable role in establishing the embryogenesis and tissue morphogenesis during early Xenopus development (Furuya, S., Sera, M., Tohno-oka, R., Sugahara, K., Shiokawa, K., and Hirabayashi, Y. (1995) Dev. Growth Differ. 37, 337-346). In this study, HS was purified from Xenopus embryos to investigate its disaccharide composition and binding ability to basic fibroblast growth factor (bFGF) and follistatin (FS), the latter being provided in two isoforms with core sequences of 315 and 288 amino acids (designated FS-315 and FS-288) originating from alternative mRNA splicing. Disaccharide composition analysis of the purified Xenopus HS showed the preponderance of a disulfated disaccharide unit with uronic acid 2-O-sulfate and glucosamine 2-N-sulfate, which has been implicated in the interactions with bFGF. Specific binding of the HS to bFGF and FS-288, the COOH-terminal truncated form, was observed in the filter binding assay, whereas HS did not bind to FS-315, indicating that the acidic Glu-rich domain of FS-315 precluded the binding. The binding of the HS to bFGF or FS-288 was markedly inhibited by heparin (HP) and various HS preparations, but not by chondroitin sulfate, supporting the binding specificity of HS. The binding specificity was further investigated using FS-288 and bovine intestinal [3H]HS. Competitive inhibition assays of the HS binding to FS-288 using size-defined HP oligosaccharides revealed that the minimum size required for significant inhibition was a dodecasaccharide, which is larger than the pentasaccharide required for bFGF binding. The binding affinity of FS to HS increased in the presence of activin, a growth/differentiation factor, which could be inactivated by direct binding to FS. These results, taken together, indicate that the structural requirement for binding of HS to bFGF and FS is different. HS may undergo dynamic changes in its structure during early Xenopus embryogenesis in response to the temporal and spatial expression of various growth/differentiation factors.

Follistatin-like immunoreactivity in the cytoplasm and nucleus of spermatogenic cells in the rat

Immunohistochemistry using an antiserum raised against the synthetic follistatin peptide (residues 123-134) was used, in the present study, to detect the stage-specific appearance of immunoreactive follistatin in the rat testis. Follistatin immunoreactivity was not found in Sertoli and Leydig cells, while it was clearly detected in spermatogenic cells. Follistatin-like immunoreactivity was detected in the cytoplasm and nucleus of late pachytene spermatocytes. Although the reaction in the cytoplasm disappeared after meiosis, it continued to be intense in the nucleus from pachytene spermatocytes to round spermatids. This finding indicated that follistatin or its closely related peptide produced in late pachytene spermatocytes migrates from the cytoplasm to the nucleus. We subjected rat testis homogenate to affinity chromatography on a sulfate-cellulofine and anti-follistatin Cys (123-134)-Affi-Gel Hz column followed by reverse-phase HPLC and analyzed the resulting fractions by Western blotting using follistatin antiserum. Three major bands at 57, 45 and 39 kDa or four bands at 52, 44, 39 and 34 kDa were detected in crude preparations from rat testis homogenate, under reducing or non-reducing SDS-PAGE respectively. The protein from rat testis, which was recognized by anti-follistatin (123-134) antiserum, exhibited a characteristic pattern for follistatin on SDS-PAGE, i.e. slower migration under reducing conditions than under non-reducing conditions, suggesting that it was follistatin or its closely related protein. Follistatin or its closely related protein may be a stage-specific modulator of spermatogenesis. Since follistatin-like immunoreactivity was not found in oocytes in any stage of development from embryonic to adult rats, it may act in an event specific to spermatogenesis, such as nuclear condensation.

Synthesis of a novel sialic acid derivative (sialylphospholipid) as an antirotaviral agent

A novel sialylphospholipid (SPL) was synthesized from N-acetylneuraminic acid (NeuAc) and phosphatidylcholine (PC) by a chemical and enzymatic method and evaluated as an inhibitor of rotavirus. PC and 1,8-octanediol were conjugated by transesterification reaction of Streptomyces phospholipase D (PLD) under a water-chloroform biphasic system to afford phosphatidyloctanol, which was condensed with a protected 2-chloro-2-deoxyneuraminic acid derivative by using silver trifluoromethanesulfonate as an activator in chloroform and converted, after deprotection, to SPL. Rhesus monkey kidney cells (MA-104) were incubated with simian (SA-11 strain) and human (MO strain) rotaviruses in the presence of SPL, and the cells infected were detected indirectly with anti-rotavirus antibody. SPL showed dose dependent inhibition against both virus strains. The concentrations required for 50% inhibition (IC50) against SA-11 and MO were 4.35 and 16.1 microM, respectively, corresponding to 10(3)- and 10(4)-fold increases in inhibition as compared to monomeric NeuAc.

Distribution of human endogenous retroviral RTVL-H2 LTR sequences among human chromosomes

The human genome carries multiple copies of sequences related to endogenous retroviral DNA. We report here the distribution of a new multicopy long terminal repeat (LTR) sequence that has been a part of an endogenous retrovirus-like sequence RTVL-H2. Twenty-four human chromosomes were either separated by flow sorting or by using rodent cells carrying a single human chromosome, and the DNA was subjected to Southern analyses using the RTVL-H2 DNA as a probe. The RTVL-H2 LTRs were distributed among all the human chromosomes, but the density and the profile differed from chromosome to chromosome. The same chromosome obtained from different individuals showed essentially the same chromosome-specific patterns. The distribution of the RTVL-H2 LTRs among different chromosomes did not correlate with the distribution of LTRs from another endogenous retroviral DNA, HERV-A, strongly suggesting that there is no preferred chromosome or a region thereof, for the integration. The possibility of rearrangement or amplification after integration is discussed.

Follistatin and its role as an activin-binding protein

Follistatin (FS), a specific binding protein for activin, neutralizes the diverse actions of activin by forming an inactive complex with activin. FS is a monomer derived from two polypeptide core sequences of 288 (FS-288) and 315 (FS-315) amino acids originated from alternatively spliced mRNA. We purified six molecular forms of FS from porcine ovaries. Their structural differences were caused by truncation of the COOH-terminal region and/or the presence of carbohydrate chains, resulting in the formation of FS-288, FS-315 and FS composed of 303 amino acids (FS-303) in various forms of glycosylation on the two potential Asn-linked glycosylation sites. All six molecular species have almost the same activin binding activity (Kd = 540-680 pM). By contrast, the COOH-terminal truncated form, FS-288, showed much higher affinity for heparan sulfate proteoglycans of the cell surface than FS-303, whereas the intact form of FS, FS-315, had no affinity. Furthermore, FS-288 more effectively blocked the suppression of follicle-stimulating hormone (FSH) secretion from rat pituitary cells by activin. This implies that activin binds to the cell surface through FS-288 which adheres to the cell surface. To clarify the physiological role of cell-associated FS, we then investigated the binding of activin to cell-associated FS and the fate of cell surface-bound activin and FS using primary cultured rat pituitary and ovarian granuloma cells. When the cells were incubated with 125I-activin A in the presence of FS-288 or 315, the binding of activin A to the cell surface was promoted much more markedly by FS-288 than by FS-315. The amounts of radioactivity recovered in trichloroacetic acid-soluble fractions (degraded activin) from the incubation medium were greatly increased by the addition of FS-288. This increase was abolished by heparan sulfate, monensin (an endocytosis inhibitor), chloroquine (a lysosome function inhibitor) and several lysosomal enzyme inhibitors. These results suggest that cell-associated FS-288 accelerates the internalization of activin into the cells, leading to its degradation by lysosomal enzymes, and that cell surface-associated FS therefore plays a role in the clearance system of activin.

Genomic organization and chromosomal localization of the mouse telencephalin gene, a neuronal member of the ICAM family

Telencephalin is a cell adhesion molecule belonging to the immunoglobulin (Ig) superfamily, whose expression is restricted to subsets of neurons in the telencephalon, the most rostral segment of brain. Of all the Ig superfamily molecules so far identified, the structure of telencephalin is most closely related to those of intercellular adhesion molecules (ICAMs)-1 and -3. Here we report the cloning, characterization, and chromosomal localization of the mouse telencephalin gene (Tlcn). The Tlcn gene spanned about 6.3 kb and consisted of 11 exons. A signal peptide and individual nine Ig-like domains of telencephalin were encoded by a single exon, while the transmembrane and cytoplasmic regions were fused in a same exon. The primer extension technique was used to establish that the transcription initiation sites were located 92-95 bp upstream from the ATG start codon. DNA sequencing of the 5'-flanking region revealed the presence of a strong initiator element for TATA-less genes, two CAAT boxes, and numerous potential transcription factor binding sites including four E-box and two N-box sequences. Interspecific backcross analysis demonstrated that the Tlcn gene was mapped in the proximal region of mouse chromosome 9 in close vicinity to the Icam-1 gene, suggesting that Tlcn and Icam-1 are derived from a common ancestral gene by gene duplication.

A novel role of follistatin, an activin-binding protein, in the inhibition of activin action in rat pituitary cells. Endocytotic degradation of activin and its acceleration by follistatin associated with cell-surface heparan sulfate

There are two types of the activin-binding protein follistatin (FS), FS-288 and FS-315. These result from alternative splicing of mRNA. FS-288 exhibits high affinity for cell-surface heparan sulfate proteoglycans, whereas FS-315 shows low affinity. To understand the physiological role of cell-associated FS, we investigated the binding of activin to cell-associated FS and its behavior on the cell surface using primary cultured rat pituitary cells. Affinity cross-linking experiments using 125I-activin A demonstrated that activin bound to rat pituitary cells via FS as well as to their receptors on the cell surface. FS-288 promoted the binding of activin A to the cell surface more markedly than FS-315. When the cells were incubated with 125I-activin A in the presence of FS-288, significant degradation of activin A was observed, and this was dependent on the FS-288 concentration. This activin degradation was abolished by heparan sulfate, chloroquine, and several lysosomal enzyme inhibitors. Moreover, FS-288 stimulated cellular uptake of activin A, whereas chloroquine suppressed lysosomal degradation following internalization, as demonstrated by microscopic autoradiography. These results suggest that cell-associated FS-288 accelerates the uptake of activin A into pituitary cells, leading to increased degradation by lysosomal enzymes, and thus plays a role in the activin clearance system.

A comparison of the uricosuric effects in rats of diltiazem and derivatives of dihydropyridine (nicardipine and nifedipine)

The effects of nicardipine and nifedipine on the urinary excretion of urate were examined in rats and compared with those of diltiazem. Test drugs were administered to urethane-anesthetized oxonate-loaded rats by continuous i.v. infusion. Diltiazem (10 micrograms/rat/min), nicardipine (0.3 microgram/rat/min) and nifedipine (1.0 microgram/rat/min) caused similar reductions of systemic blood pressure and increased total renal blood flow. Diltiazem did not increase urine volume significantly. However, this drug produced obvious uricosuria, with a significant increase in the ratio of urate clearance to inulin clearance (Cua/Cin), which resulted from an increase in Cua, but not from changes in the glomerular filtration rate (GFR). Nicardipine had clear diuretic and uricosuric effects, with similar increases in Cua and GFR and, thus, no change in Cua/Cin. On the other hand, nifedipine did not have any significant effect on the renal handling of urate. These results suggest that nicardipine produces uricosuria in rats via alterations in renal hemodynamics, while the uricosuric effect of diltiazem involves the tubules, as well as alterations in renal hemodynamics.