Regulation of secretogranin II mRNA in rat neuronal cultures

Secretoneurin is a secretogranin-2 derived hormonal peptide in vertebrate neuroendocrine systems

Secretogranin-2 (SCG2) is a large precursor protein that is processed into several potentially bioactive peptides, with the 30-43 amino acid central domain called secretoneurin (SN) being clearly evolutionary conserved in vertebrates. Secretoneurin exerts a diverse array of biological functions including regulating nervous, endocrine, and immune systems in part due to its wide tissue distribution. Expressed in some neuroendocrine neurons and pituitary cells, SN is a stimulator of the synthesis and release of luteinizing hormone from both goldfish pituitary cells and the mouse LβT2 cell line. Neuroendocrine, paracrine and autocrine signaling pathways for the stimulation of luteinizing hormone release indicate hormone-like activities to regulate reproduction. Mutation of the scg2a and scg2b genes using TALENs in zebrafish reduces sexual behavior, ovulation, oviposition, and fertility. A single injection of the SNa peptide enhanced reproductive outcomes in scg2a/scg2b double mutant zebrafish. Evidence in goldfish suggests a new role for SN to stimulate food intake by actions on other feeding-related neuropeptides. Expression and regulation of the Scg2a precursor mRNA in goldfish gut also supports a role in feeding. In rodent models, SN has trophic-like properties promoting both neuroprotection and neuronal plasticity and has chemoattractant properties that regulate neuroinflammation. Data obtained from several cellular models suggest that SN binds to and activates a G-protein coupled receptor (GPCR), but a bona fide SN receptor protein needs to be identified. Other signaling pathways for SN have been reported which provides alternatives to the GPCR hypothesis. These include AMP-activated protein kinase (AMPK), extracellular signal-regulated kinases (ERK), mitogen-activated protein kinase (MAPK)and calcium/calmodulin-dependent protein kinase II in cardiomyocytes, phosphatidylinositol 3-kinase (PI3K) and Akt/Protein Kinase B (AKT, and MAPK in endothelial cells and Janus kinase 2/signal transducer and activator of transcription protein (JAK2-STAT) signaling in neurons. Some studies in cardiac cells provide evidence for cellular internalization of SN by an unknown mechanism. Many of the biological functions of SN remain to be fully characterized, which could lead to new and exciting applications.

The secretogranin II gene is a signal integrator of glutamate and dopamine inputs

Cooperative gene regulation by different neurotransmitters likely underlies the long-term forms of associative learning and memory, but this mechanism largely remains to be elucidated. Following cDNA microarray analysis for genes regulated by Ca(2+) or cAMP, we found that the secretogranin II gene (Scg2) was cooperatively activated by glutamate and dopamine in primary cultured mouse hippocampal neurons. The Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA-AM) and the mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitor PD98059 prevented Scg2 activation by glutamate or dopamine; thus, the Ca(2+) /MEK pathway is predicted to include a convergence point(s) of glutamatergic and dopaminergic signaling. Unexpectedly, the protein kinase A inhibitor KT5720 enhanced Scg2 activation by dopamine. The protein-synthesis inhibitor cycloheximide also enhanced Scg2 activation, and the proteasome inhibitor ZLLLH diminished the KT5720-mediated augmentation of Scg2 activation. These results are concordant with the notion that dopaminergic input leads to accumulation of a KT5720-sensitive transcriptional repressor, which is short-lived because of rapid degradation by proteasomes. This repression pathway may effectively limit the time window permissive to Scg2 activation by in-phase glutamate and dopamine inputs via the Ca(2+) /MEK pathway. We propose that the regulatory system of Scg2 expression is equipped with machinery that is refined for the signal integration of in-phase synaptic inputs. We proposed hypothetical mechanism for the regulation of the secretogranin II gene as a signal integrator of glutamate and dopamine inputs. Glutamate or dopamine activates the Ca(2+) /MEK/ERK pathway, which thus contributes to the signal integration. Concurrently, activation of the PKA inhibitor KT5720-sensitive pathway by dopamine leads to accumulation of the repressor protein X that is otherwise susceptible to proteasome degradation. This repression system may determine the time window permissive to the cooperative activation by in-phase glutamate and dopamine inputs.

Aspects of the neuroendocrine cerebellum: expression of secretogranin II, chromogranin A and chromogranin B in mouse cerebellar unipolar brush cells

Morphologically distinct neuron classes can be subdivided in sublineages by differential chemical phenotypes that correlate with functional diversity. Here we show by immunocytochemistry that chromogranin A (CgA) chromogranin B (CgB) and secretogranin II (SgII), the principal granins situated in neuronal secretory granules and large dense-core vesicles, are widely but differentially expressed in cells of the mouse cerebellum and terminals of cerebellar afferents. While CgA and CgB were nearly panneuronal, SgII was more restricted in distribution. The cells most intensely immunoreactive for SgII were a class of small, excitatory interneurons enriched in the granular layer of the vestibulocerebellum, the unipolar brush cells (UBCs), although larger neurons likely to be a subset of the Golgi-Lugaro-globular cell population were also distinctly immunopositive; by contrast, Purkinje cells and granule cells were, at best, faintly stained and, stellate, basket cells were unstained. SgII was also present in subsets of mossy fibers, climbing fibers and varicose fibers. Neurons in the cerebellar nuclei and inferior olive were distinctly positive for the three granins. Double-labeling with subset-specific cell class markers indicated that, while both CgA and CgB were present in most UBCs, SgII immunoreactivity was present in the calretinin (CR)-expressing subset, but lacked in metabotropic glutamate receptor 1alpha (mGluR1alpha)-expressing UBCs. Thus, we have identified an additional cell class marker, SgII, which serves to study subtype properties in the UBC population. The abundance of SgII in only one of the two known subsets of UBCs is remarkable, as its expression in other neurons of the cortex was moderate or altogether lacking. The data suggest that the CR-positive UBCs represent a unique neuroendocrine component of the mammalian cerebellar cortex, presumably endowed with transynaptically regulated autocrine or paracrine action/s. Because of the well-known organization of the cerebellar system, several of its neuron classes may represent valuable cellular models to analyze granin functions in situ, in acute slices and in dissociated cell and organotypic slice cultures.

GABAB receptor stimulation decreases amphetamine-induced behavior and neuropeptide gene expression in the striatum

The purpose of this study was to investigate whether GABA(B) receptor activation blocks acute amphetamine-induced behavioral activity, dopamine release, and neuropeptide mRNA expression in the striatum. Systemic administration of R-(+)-baclofen (1.25 mg/kg, i.p.) did not alter total distance traveled or vertical rearing induced by amphetamine (2.5 mg/kg, i.p.). At 2.5 mg/kg, baclofen did not alter spontaneous motor activity or total distance traveled, but completely blocked vertical rearing induced by amphetamine. At 5.0 mg/kg, baclofen completely blocked both total distance traveled and vertical rearing induced by amphetamine. Quantitative in situ hybridization histochemistry revealed that baclofen (2.5 mg/kg, i.p.) decreased the ability of amphetamine to increase preprodynorphin (PPD), preprotachykinin (PPT), preproenkephalin (PPE), and secretogranin II (SGII) mRNA levels in the striatum without altering the basal levels of these signals. Baclofen also blocked the amphetamine-induced rise in SGII mRNA in the core and shell of the nucleus accumbens and cingulate cortex. In a separate experiment, systemic baclofen (2.5 mg/kg) decreased the amphetamine-induced increase in dialysate dopamine levels in the striatum. These results suggest that reduced striatal dopamine release contributes to the ability of GABA(B) receptor activation to decrease acute amphetamine-induced behavioral activity and striatal neuropeptide gene expression.

Differential effects of phencyclidine application on secretogranin II expression in organotypic slices of rat prefrontal cortex

Phencyclidine (PCP) is a non-competitive NMDA glutamate receptor antagonist that induces psychotomimetic effects in humans and experimental animals. Chronic PCP exposure elicits signs of persistently altered frontal brain activity and related behaviors which are also seen in patients with schizophrenia. Secretogranin II (sg II) belongs to the chromogranin family of proteins that exist in large dense core vesicles in nervous tissue. In the brain, 90% of sg II is processed to the small peptide secretoneurin. We previously detected differential effects of single-dose and subchronic PCP administration on sg II expression in the rat prefrontal cortex (PFC). In the present study, we applied PCP to organotypic PFC slices. PCP application for 28 h induced decreased tissue and culture medium secretoneurin content. In contrast, incubation with the adenylate cyclase activator forskolin caused significantly increased secretoneurin levels after 8 h. PCP for 4 h followed by 24 h without PCP resulted in increased culture medium secretoneurin content but no change in tissue levels. sg II mRNA expression was decreased after 28 h PCP application in cortical neurons. Immunohistochemical and TUNEL staining profiles indicated that the alterations were not due to neurodegeneration. PCP for 5 days changed neither the secretoneurin tissue or culture medium levels, nor the sg II mRNA expression. These results demonstrate that PCP modulates sg II expression in PFC tissue in the absence of afferent inputs and that the nature of these changes is dependent upon the duration of exposure to and/or withdrawal from PCP.

Gonadotropin-releasing hormone-induced stimulation of the rat secretogranin II promoter involves activation of CREB

To investigate the events involved in regulation of the secretogranin II (SgII) gene, luciferase reporter constructs were transfected into gonadotrope-derived, alphaT3-1 cells. DNA between -91 and -60 relative to the transcription start site was found to be required for GnRH induced SgII reporter gene activation. This region contains a consensus cAMP response element (CRE) and disruption of this CRE reduced GnRH responsiveness of the SgII promoter. CREB was shown to bind to the SgII CRE and transfection studies with a dominant-negative CREB mutant provided evidence that CREB is required for GnRH responsiveness of the SgII promoter. An expression vector for an inhibitor of the cAMP-dependent protein kinase was found to reduce the ability of cAMP or GnRH to activate the SgII-luciferase reporter gene. These studies offer evidence that GnRH-induced activation of the SgII promoter in the alphaT3-1 cell line requires cAMP-dependent protein kinase activity and a functional CRE within the 5'-flanking region of the gene.

Neuroendocrine cell type-specific and inducible expression of chromogranin/secretogranin genes: crucial promoter motifs

The chromogranin/secretogranins (Cg/Sg) are a family of soluble, acidic proteins representing major constituents in secretory vesicle cores of virtually all neuroendocrine tissues. We and others have identified the cyclic adenosine monophosphate response element (CRE) as the crucial promoter element responsible for neuroendocrine cell type-specific expression of the Cg/Sg genes. In addition to CRE, GC-rich domains in chromogranin B (CgB) and serum response element (SRE) in secretogranin II (SgII) promoters appear to play important roles in neuroendocrine cell type-specific expression of CgB and SgII genes. Nicotinic-cholinergic and peptidergic chromaffin cell stimuli evoke catecholamine secretion and augment biosynthesis of Cg/Sg genes. These stimuli signal to CgA gene transcription through the CRE in cis and through protein kinase A, protein kinase C, and mitogen-activated protein kinase and CRE-binding protein in trans. In addition to CRE, a GC-rich domain in CgB and SRE in SgII promoters also play important roles in mediating inducible expression of the CgB and SgII genes. We conclude that CRE, GC-rich domains, and SRE are crucial determinants of both cell type-specific and secretagogue-inducible expression of the Cg/Sg genes.

Myb-binding protein 1a augments AhR-dependent gene expression

We have studied the mechanism by which an acidic domain (amino acids 515-583) of the aromatic hydrocarbon receptor (AhR) transactivates a target gene. Studies with glutathione S-transferase fusion proteins demonstrate that the wild-type acidic domain associates in vitro with Myb-binding protein 1a, whereas a mutant domain (F542A, I569A) does not. AhR-defective cells reconstituted with an AhR containing the wild-type acidic domain exhibit normal AhR function; however, cells reconstituted with an AhR containing the mutant acidic domain do not function normally. Transient transfection of Myb-binding protein 1a into mouse hepatoma cells is associated with augmentation of AhR-dependent gene expression. Such augmentation does not occur when Myb-binding protein 1a is transfected into AhR-defective cells that have been reconstituted with an AhR that lacks the acidic domain. We infer that 1) Myb-binding protein 1a associates with AhR, thereby enhancing transactivation, and 2) the presence of AhR's acidic domain is both necessary and sufficient for Myb-binding protein 1a to increase AhR-dependent gene expression.

Dioxin-inducible transactivation in a chromosomal setting. Analysis of the acidic domain of the Ah receptor

We analyzed the transactivation function of the acidic segment of the Ah receptor (amino acids 515-583) by reconstituting AhR-defective mouse hepatoma cells with mutants. Our data reveal that both hydrophobic and acidic residues are important for transactivation and that these residues are clustered in two regions of the acidic segment of AhR. Both regions are crucial for function, because disruption of either one substantially impairs transactivation of the chromosomal CYP1A1 target gene. Neither region contains an amino acid motif that resembles those reported for other acidic activation domains. Furthermore, proline substitutions in both regions do not impair transactivation in vivo, a finding that implies that alpha-helix formation is not required for function.

Regulation of chromogranin biosynthesis by neurotrophic growth factors in neuroblastoma cells

Polypeptide growth factors secreted from the target tissue determine the choice of transmitter synthesis in the innervating nerves. We have investigated whether they also influence the expression of chromogranins and neuropeptide Y, components co-stored with the neurotransmitters within large dense-core vesicles. IMR-32 and SH-SY5Y human neuroblastoma cells were treated for up to six days with various neurotrophic growth and differentiation factors. For chromogranins A and B, no significant changes at the mRNA level were observed and for chromogranin A this was confirmed at the protein level. The expression of secretogranin II/pro-secretoneurin mRNA, however, was considerably enhanced in both cell lines after basic fibroblast growth factor treatment. In IMR-32 cells we determined a fast and continuous induction, whereas the up-regulation in SH-SY5Y cells was more delayed. A transient elevation of secretogranin II/pro-secretoneurin mRNA levels was seen in SH-SY5Y cells in response to epidermal growth factor. In these cells we also measured the amounts of secretogranin II/pro-secretoneurin protein which were increased by both growth factors. In addition to the above described changes in secretogranin II/pro-secretoneurin biosynthesis we extended and confirmed data available on neuropeptide Y. We found a qualitatively similar pattern of biosynthesis regulation as for secretogranin II/pro-secretoneurin, indicating that the ultimately increased expression of the two proteins may be characteristic of the phenotypic differentiation after growth factor treatment. Moreover, this finding of a concomitant regulation further emphasizes the concept of secretogranin II/pro-secretoneurin being a neuropeptide precursor from which the functional peptide secretoneurin is proteolytically liberated.

Regulation of the biosynthesis and processing of chromogranins in organotypic slices: influence of depolarization, forskolin and differentiating factors

Slices from rat hippocampus in organotypic culture were used to study the biosynthesis regulation of chromogranins A and B and secretogranin II. Additionally, we investigated the proteolytic conversion of secretogranin II and the levels of prohormone convertases putatively involved. Forskolin treatment and depolarization with potassium plus BayK 8644 led to significant increases in secretogranin II mRNA in the principal cells of the hippocampus. Enhanced expression of secretogranin II was also reflected by a rise in peptide levels. Despite this induction of biosynthesis the extensive processing to secretoneurin normally observed in brain was maintained. Both forskolin and depolarization upregulated the prohormone convertase (PC)1, but not PC2, indicating that PC1 levels are critical for secretoneurin production under stimulating conditions. Results obtained for chromogranins A and B were less consistent. For chromogranin A mRNA, changes were restricted to granule cells; for chromogranin B, a response in granule cells was observed to depolarization but not to forskolin, and effects in pyramidal neurons were weak. Accordingly, we were unable to detect alterations in chromogranin A and B protein levels. Furthermore, we tested several neurotrophic growth factors and found that only basic fibroblast growth factor raised secretogranin II expression without affecting chromogranins A and B. The hippocampal slice preparation allowed well controlled treatment with identification of neuronal subpopulations and yielded data largely matching experiments in vivo and in cell culture. The pronounced regulation of secretogranin II and its effective processing underlines the importance of the resulting peptide secretoneurin as an active neuropeptide in the nervous system.

Isolation and characterization of the human secretogranin II gene promoter

The goal of this study was to isolate and functionally characterize the human secretogranin II (SgII) gene promoter. SgII is a member of the granin family of proteins which are selectively expressed in neurosecretory cells. The human SgII promoter contains a consensus TATA box and cyclic AMP response element (CRE) 35 and 74 bp upstream of the transcription start site, respectively, elements also found in the mouse and rat SgII gene promoters. Transfection studies showed that 869 bp of the human SgII promoter were sufficient to confer cell type-specific expression of an SgII promoter-luciferase reporter gene in neurosecretory PC-12, GH and BE(2)-M17 cells. The activity of the human SgII promoter was also compared in three N-type, human neuroblastoma cell lines [BE(2)-M17, SMS-KAN and SH-SY5Y], which differ markedly in the level of SgII expression. SgII promoter activities in the neuroblastoma cell lines correlated not only with the levels of SgII but also the levels of the cyclic AMP response element-binding protein CREB which were highest in BE(2)-M17 cells and lowest in SH-SY5Y cells. To establish that the activity of the human SgII promoter in these neuroblastoma cell lines is dependent on the level of CREB, rat CREB was overexpressed in SH-SY5Y cells. SgII promoter activity was up to 8-fold higher in SH-SY5Y cells overexpressing CREB. These results suggest that SgII expression is a marker for neuronal differentiation in human neuroblastoma cell lines and is dependent on the level of CREB expression.

Synergistic action of upstream elements and a promoter-proximal CRE is required for neuroendocrine cell-specific expression and second-messenger regulation of the gene encoding the human secretory protein secretogranin II

Secretogranin II (SgII) is a secretory polypeptide stored in large dense core vesicles of neuroendocrine and neuronal cells. In order to characterize the molecular mechanisms underlying the tissue-specific expression of the SgII gene and its regulation by second-messenger pathways in endocrine and neuronal cells, we have cloned and characterized the human SgII gene. Sequence analysis revealed the existence of numerous putative cis-regulatory elements in the SgII gene promoter, including a consensus cyclic AMP-responsive element (CRE). Constructs containing different portions of the human SgII promoter fused to the luciferase reporter were transfected in AtT-20, SH-SY5Y, LLC-PK1 or COS-7 cells. Northern blot analysis showed that the endogenous SgII gene is more highly expressed in AtT-20 cells than in SH-SY5Y cells, and not expressed at all in LLC-PK1 cells. Treatment by forskolin or 12-O-tetradecanoylphorbol-13-acetate (TPA) caused a 1.5- and 10-fold increase, respectively, in SgII mRNA levels in SH-SY5Y cells but not in AtT-20 cells. Transfection experiments revealed that 4 kb of the human SgII promoter is sufficient to impart cell-specific expression of the reporter gene in the four cell lines studied. Specifically, in AtT-20 cells, a positive element located between -1.38 and -4 kb, in addition to the CRE, is responsible for the high expression of the SgII gene. In SH-SY5Y cells, a negative element located between -0.66 and -1.4 kb represses the activating effect of the CRE leading to an overall lower activity of fusion genes in these cells compared to the activity in AtT-20 cells. Finally, the promoter activity was very low in LLC-PK1 and COS-7 cells. Forskolin and TPA stimulated the activity of a SgII-luciferase fusion gene in SH-SY5Y but not in AtT-20 cells. Disruption of the CRE abolished the stimulatory effect of forskolin and TPA. These data suggest that the basal activity of the human SgII gene relies on cell-specific trans-acting factors in addition to factors that bind to the CRE and show that the regulation of this gene by second messengers is cell-specific and requires an intact CRE.

Coactivation of secretogranin-II and BDNF genes mediated by calcium signals in mouse cerebellar granule cells

In primary culture of mouse cerebellar granule cells, the brain-derived neurotrophic factor (BDNF) gene is activated in an activity-dependent manner, accompanying Ca2+ influx into neurons through voltage-dependent calcium channels (VDCCs). In this study, we investigated the inducibility of secretogranin-II (Sg-II) gene in terms of Ca2+ signals evoked via VDCCs, by a comparison with BDNF and c-fos genes. Deprivation and subsequent induction of membrane depolarization by lowering and reelevating the extracellular concentration of potassium chloride (KCl), respectively, led to an decrease and then an increase in the Sg-II, BDNF and c-fos mRNA expression. The increase in Sg-II mRNA expression was detected as early as but was slower than that of BDNF one. The increase in Sg-II mRNA expression was induced depending upon the extracellular Ca2+ and inhibited by nicardipine, indicating a requirement of Ca2+ influx through VDCCs for the Sg-II as well as BDNF gene induction. Inhibition of de novo protein synthesis by cycloheximide did not affect the Sg-II induction. The response of Sg-II gene to the changes in extracellular KCl concentration was the same as that of BDNF but different from that of c-fos gene. Thus, Sg-II gene is coactivated with BDNF gene in response to the intracellular Ca2+ signals evoked via Ca2+ influx through VDCCs.

Identification of a novel secretogranin II-derived peptide (SgII(187-252)) in adult and fetal human adrenal glands using antibodies raised against the human recombinant peptide

Molecular cloning of secretogranin II (SgII) in phylogenetically distant species has recently revealed the existence of a highly conserved 66-amino acid peptide flanked by preserved pairs of basic residues. This observation suggested that this peptide, named EM66, which had not been described to date, could be an important processing product of SgII. The aim of the present study was to investigate the possible occurrence of EM66 in the human adrenal gland. The EM66 peptide was generated in Escherichia coli, which was programmed to make a fusion protein containing the human EM66 sequence. The affinity-purified fusion protein was used to raise polyclonal antibodies in rabbits. The free EM66 peptide was obtained by cleavage of the fusion protein followed by high performance liquid chromatography purification. Immunohistochemical analysis using the EM66 antibodies revealed intense labeling of adrenochromaffin cells in the adult adrenal medulla and the fetal adrenal gland. A sensitive and specific RIA was developed and applied to the detection of EM66-like immunoreactivity in extracts of adult adrenal medulla and whole fetal adrenal gland after high performance liquid chromatographic analysis. A major immunoreactive species exhibiting the same retention time as recombinant EM66 was detected in both adult and fetal adrenal extracts. Taken together, these data demonstrate that posttranslational processing of SgII actually generates EM66 in the adrenal gland. The strong conservation of the amino acid sequence of EM66 in the vertebrate phylum and the occurrence of the mature peptide in both fetal and adult chromaffin cells suggest that EM66 could play an important physiological role in the human adrenal gland.

Identification of a novel secretogranin II-derived peptide in the adult and fetal human adrenal gland

Molecular cloning of secretogranin II (SgII) in different species has revealed the existence of a highly conserved 66-amino acid peptide (EM66) flanked by preserved pairs of basic residues. In the present study we have localized and characterized EM66 in the human adrenal gland. A fusion protein containing the human EM66 peptide was produced in E. coli and used to raise polyclonal antibodies in rabbits. Immunohistochemical staining of human adrenal slices revealed intense labeling of adrenochromaffin cells in the adult and fetal gland. HPLC analysis of adrenal extracts showed the presence of an immunoreactive peak exhibiting the same retention time as recombinant EM66 in both adult and fetus. These data demonstrate that post-translational processing of SgII actually generates a novel peptide in the human adrenal gland. The conservation of the sequence of EM66 in vertebrates and the occurrence of the mature peptide during early ontogenesis of the human adrenal gland strongly suggest that EM66 could exert physiological activities.

Regulation of the biosynthesis of large dense-core vesicles in chromaffin cells and neurons

1. The proteins of large dense-core vesicles (LDV) in neuroendocrine tissues are well characterized. Secretory components comprise chromogranins and neuropeptides. Intrinsic membrane proteins include cytochrome b-561, transporters, SV2, synaptotagmin, and synaptobrevin. 2. The effects of stimulation and of second messengers on the biosynthesis of LDV have been studied in detail. 3. Regulation of biosynthesis is complex. The cell can adapt to prolonged stimulation either by producing vesicles of normal size filled with a higher quantum of secretory peptides or by forming larger vesicles. In addition, some components, e.g., enzymes, can be upregulated specifically.

The cAMP-response element mediates induction of secretogranin II by CHX and FSK in GH4C1 cells

The effect of cAMP on secretogranin II (SgII) gene transcription in GH4C1 (GH) cells is not observed unless protein synthesis is inhibited. We have defined elements in the SgII promoter that mediate regulation by cycloheximide (CHX) and forskolin (FSK) and characterized the nuclear proteins that interact with them. GH cells were transfected with p2774Luc, p351Luc, p242Luc, and p223Luc containing 2,612, 189, 80, and 61 bp of the SgII promoter upstream of the luciferase gene, respectively. Treatment with CHX and FSK increased promoter activity 8- to 12-fold in cells transfected with p2774Luc, p351Luc, and p242Luc but had not effect in cells transfected with p223Luc. The same 19-bp element (-80 to -62) mediates regulation by CHX alone, as CHX caused a 3.8-fold increase in activity in GH cells transfected with p242Luc but not p223Luc. Gel mobility shifts using sequences -84 to -53 resulted in three complexes, which contained cAMP response element-binding protein heterodimerized with cAMP response element modulator or activating transcription factor-1. No differences were observed in complex formation when cells were treated with either CHX, FSK, or CHX and FSK. Thus CHX affects the response to FSK in GH cells by inhibiting the synthesis of a protein, which does not itself interact with DNA or affect the binding of CRE-binding proteins with the SgII promoter, but likely interferes with the interaction of CRE-binding proteins with the general transcriptional machinery.

Limbic seizures induce neuropeptide and chromogranin mRNA expression in rat adrenal medulla

Rats treated with kainic acid develop limbic seizures and have elevated levels of circulating catecholamines resulting from an extensive stimulation of the adrenal gland. We investigated the levels of several constituents of chromaffin granules in rat adrenal medulla after injection of kainic acid. This treatment increased mRNA steady-state levels of enkephalin, neuropeptide Y and chromogranin B 2-6-fold. Elevated levels of these constituents were found as early as 2 h after treatment and lasted up to 24 h. Chromogranin A and secretogranin II mRNA levels, on the other hand, remained unchanged. Adrenal catecholamine concentrations were reduced by 80%. Pre-treatment of rats with thiopental prior to kainic acid prevented seizures, the decline in catecholamines and the elevation of enkephalin and neuropeptide Y mRNAs but not that of chromogranin B. On the other hand, the peripherally acting ganglionic blocker chlorisondamine did not protect from the kainic acid-induced up-regulation of chromogranin B mRNA, suggesting that chromogranin B mRNA may be regulated by a direct effect of kainic acid on chromaffin cells. The pattern of changes in mRNA expression differed from that seen after insulin hypoglycemia or reserpine treatment. Thus, stimulation of the splanchnic innervation in vivo by various means leads to an individual and independent regulation of granule constituents by quite different mechanisms.