Three immediate early gene response elements in the proximal preprotachykinin-A promoter in two functionally distinct domains

Lithium chloride regulation of the substance P encoding preprotachykinin a, Tac1 gene in rat hippocampal primary cells

In rat hippocampal cultures, the preprotachykinin A (PPTA/Tac1) gene, which encodes the neuropeptide substance P, is regulated by the action of lithium. We used reporter gene and expression constructs to demonstrate that this mechanism of action of lithium is mediated via a previously characterised cis-regulatory Ebox element in the proximal promoter, which binds members of the basic Helix-Loop-Helix family of transcription factors. Consistent with this, in hippocampal cells, both the expression of the endogenous gene and the function of this promoter element are differentially regulated by the basic Helix-Loop-Helix factors, upstream stimulatory factor 1 and 2 (USF1/2). In addition, the genes for USF1 and USF2 are differentially regulated by lithium in these cells. Our data implicate USF1 as a major regulator of the action of lithium on the proximal PPTA promoter.

Extracellular signal-regulated kinase 1/2 and c-Jun NH2-terminal kinase, through nuclear factor-kappaB and activator protein-1, contribute to caerulein-induced expression of substance P and neurokinin-1 receptors in pancreatic acinar cells

The neuropeptide substance P (SP) has emerged to be an important proinflammatory mediator in acute pancreatitis (AP). The presence of substance P and its receptor, neurokinin-1 receptor (NK1R) has been shown in the pancreas and the pancreatic acinar cells. In this study, we investigated the unexplored mechanisms that mediate SP and NK1R expression using an in vitro AP model. Pancreatic acinar cells were obtained from pancreas of male Swiss mice. Isolated cells were treated with caerulein to mimic secretagogue pancreatitis. A concentration-dependent study that subjected the cells to 60 min of stimulation by caerulein showed that SP and the transcript from its gene preprotachykinin-A (PPT-A), and NK1R were up-regulated at a supraphysiological concentration of 10(-7) M. A concentration-dependent study on intracellular kinases, extracellular signal-regulated kinase (ERK1/2), and c-Jun N-terminal kinase (JNK) and also transcription factors nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) showed that they were activated when the caerulein concentration was 10(-7) M. Inhibition of JNK reversed the up-regulation of PPT-A, SP, and NK1R. However, inhibition of ERK1/2 reversed the up-regulation of NK1R but not of PPT-A and SP. Furthermore, we found that specific ERK1/2 and JNK inhibitors reduce NF-kappaB and AP-1 activity. Taken together, our results suggest that supraphysiological concentrations of caerulein up-regulate the expression of SP and NK1R in pancreatic acinar cells, and the signaling molecules that are involved in this up-regulation include ERK1/2, JNK, NF-kappaB, and AP-1.

Regulatory mechanisms in the differential expression of Hemokinin-1

Hemokinin-1, encoded by the TAC4 gene, is the most recent addition to the tachykinin family. Although most closely related to the neuropeptide Substance P, Hemokinin-1 distinguishes itself from other tachykinins by its predominantly non-neuronal expression pattern. Its expression in T and B lymphocytes, macrophages, and dendritic cells points to an important role for Hemokinin-1 in the immune system. To seek reasons for its preferential expression in the immune system and ultimately to provide clues to its function, we investigated the molecular mechanisms driving the differential expression pattern of this unique tachykinin. Our study provides the first analysis of the promoter region of the TAC4 gene, which reveals regulatory mechanism different from the Substance P promoter. We demonstrate for the first time that Hemokinin-1 initiates transcription from multiple start sites through a TATA-less promoter. Conservation of the 5' non-coding region indicates the importance of the upstream regulatory region in directing expression of Hemokinin-1 in specific cell types, during cell differentiation and activation. Furthermore, NFkappaB, a transcription factor important in the activation of immune cells was shown to be involved in promoting increased TAC4 transcription during PMA induction of a T cell line. Our studies reveal that Hemokinin-1 is regulated by a unique transcription regulation system that likely governs its differential expression pattern and suggests a role for Hemokinin-1 distinct from Substance P.

Induction of deltaFosB in the periaqueductal gray by stress promotes active coping responses

We analyzed the influence of the transcription factor DeltaFosB on learned helplessness, an animal model of affective disorder wherein a subset of mice exposed to inescapable stress (IS) develop a deficit in escape behavior. Repeated IS induces DeltaFosB in the ventrolateral periaqueductal gray (vlPAG), and levels of the protein are highly predictive of an individual's subsequent behavorial deficit-with the strongest DeltaFosB induction observed in the most resilient animals. Induction of DeltaFosB by IS predominates in substance P-positive neurons in the vlPAG, and the substance P gene, a direct target for DeltaFosB, is downregulated upon DeltaFosB induction. Local overexpression of DeltaFosB in the vlPAG using viral-mediated gene transfer dramatically reduces depression-like behaviors and inhibits stress-induced release of substance P. These results indicate that IS-induced accumulation of DeltaFosB in the vlPAG desensitizes substance P neurons enriched in this area and opposes behavioral despair by promoting active defense responses.

A proximal E-box modulates NGF effects on rat PPT-A promoter activity in cultured dorsal root ganglia neurones

The rat preprotachykinin A (rtPPTA) promoter fragment spanning -865+92, relative to the major transcriptional start, has previously been demonstrated to be nerve growth factor (NGF) responsive in primary cultures of rat dorsal root ganglion (DRG) neurones [Harrison, P.T., Dalziel, R.G., Ditchfield, N.A., Quinn, J.P., 1999. Neuronal-specific and nerve growth factor-inducible expression directed by the preprotachykinin-A promoter delivered by an adeno-associated virus vector. Neuroscience 94, 997-1003]. In this communication, we demonstrate that an E box element at -60, in part, regulates the activity of this rtPPT-A promoter fragment in DRG neurones in response to NGF. Differential regulation of the promoter is observed in the presence or absence of NGF when the E Box site is present. Under basal conditions binding of proteins to this -60 element may antagonise promoter activity. Hence, in the absence of NGF, mutation of the -60 E box increased reporter gene expression. Further, comparison of levels of reporter gene expression supported by both WT and mutated promoter indicate that in the presence of NGF the -60 E box element also plays a role as an activator domain. This represents a novel mechanism for NGF regulation of rtPPT-A. Similarly, an important role for this signalling pathway was observed in neonate rat DRG neuronal cultures, which require NGF for their survival, namely mutation of the -60 element resulted in higher levels of reporter gene expression.

A model of organotypic rat spinal slice culture and biolistic transfection to elucidate factors that drive the preprotachykinin-A promoter

The tachykinin substance P (SP) is a neuropeptide that is expressed in some nociceptive primary sensory afferents and in discrete populations of spinal cord neurons. Expression of spinal SP and the preprotachykinin-A (PPT-A) gene that encodes SP exhibits plasticity in response to conditions such as peripheral inflammation but the mechanisms that regulate expression are poorly understood. We have developed a spinal cord organotypic culture system that is suitable for the analysis of PPT-A gene promoter activity following biolistic transfection of recombinant DNA constructs. Spinal cord organotypic slices showed good viability over a 7-day culture period. Immunostaining for phenotypic markers such as NeuN and beta-III tubulin demonstrated preservation of neurons and their structure, although there was evidence of axotomy-induced down-regulation of NeuN in certain neuronal populations. Neurokinin-1 receptor (NK-1R) immunostaining in laminae I and III was similar to that seen in acute slices. Biolistic transfection was used to introduce DNA constructs into neurons of these organotypic cultures. Following transfection with a construct in which expression of enhanced green fluorescent protein (EGFP) is controlled by the PPT-A promoter, we showed that induction of neuronal activity by administration of a forskolin analogue/high K(+) (10 microM/10 mM) for 24 h resulted in a fourfold increase in the number of EGFP-positive cells. Similarly, a twofold increase was obtained after treatment with the NK-1R-specific agonist [Sar(9),Met (O(2))(11)]-substance P (10 microM). These data demonstrate the usefulness of this model to study physiological and pharmacological factors relevant to nociceptive processing that can modulate PPT-A promoter activity.

How nerve growth factor drives physiological and inflammatory expressions of acid-sensing ion channel 3 in sensory neurons

Nerve growth factor (NGF) is a key element of inflammatory pain. It induces hyperalgesia by up-regulating the transcription of genes encoding receptors, ion channels, and neuropeptides. Acid-sensing ion channel 3 (ASIC3), a depolarizing sodium channel gated by protons during tissue acidosis, is specifically expressed in sensory neurons. It has been associated to cardiac ischemic and inflammatory pains. We previously showed that low endogenous NGF was responsible for ASIC3 basal expression and high NGF during inflammation increased ASIC3 expression parallely to the development of neuron hyperexcitability associated with hyperalgesia. NGF is known to activate numerous signaling pathways through trkA and p75 receptors. We now show that (i). NGF controls ASIC3 basal expression through constitutive activation of a trkA/phospholipase C/protein kinase C pathway, (ii). high inflammatory-like NGF induces ASIC3 overexpression through a trkA/JNK/p38MAPK pathway and a p75-dependent mechanism as a transcriptional switch, and (iii). NGF acts through AP1 response elements in ASIC3 encoding gene promoter. These new data indicate potential targets that could be used to develop new treatments against inflammatory pain.

Neuron restrictive silencer factor as a modulator of neuropeptide gene expression

We hypothesize that the transcription factor neuron restrictive silencer factor (NRSF) is an important determinant of the expression of the preprotachykinin (PPTA) gene (encoding substance P and Neurokinin A) and arginine vasopressin (AVP) both in neuronal and nonneuronal cells. NRSF, a zinc finger repressor protein, binds the NRSE motif found in many neuronal specific genes at a variety of promoter locations. However, it is found in a similar location at the major transcriptional start site, within both PPTA and AVP peptide promoters. We have correlated modulation of NRSF activity with expression of AVP and PPTA in a variety of cell types, indicating the general mechanism by which this protein may regulate expression. Specifically, they are as follows:(1). Expression of NRSF dramatically represses PPTA promoter activity in reporter gene constructs in primary cultures of DRG neurons.(2). The PPTA promoter activity is regulated differentially in osteoarthritic compared to normal chondrocytes. This regulation correlates with the region containing the NRSE site.(3). We have correlated a splice variant of NRSF with the establishment and progression of small cell lung carcinoma (SCLC) and demonstrated that NRSF variants can directly affect the activity of the AVP promoter in reporter gene constructs. If the deregulated expression of peptides in these diseases point to the mechanism determining the pathology, then perhaps targeting protocols that correct this deregulation may also reverse the specific disease phenotypes. Our data would indicate that modulation of NRSF activity would be a target for such intervention.

Analysis of human neuropeptide FF gene expression

As an initial step to study the function of the gene encoding the human neuropeptide FF (NPFF), we cloned a 4.7-kb sequence from the promoter region. Primer extension and 5'-rapid amplification of cDNA ends revealed multiple transcription initiation sites. Northern blot analysis of the mRNA expression revealed a specific signal only in poly(A) + RNA from medulla and spinal cord. Chimeric luciferase reporter gene constructs were transiently transfected in A549, U-251 MG, SK-N-SH, SK-N-AS and PC12 cells. The promoter activity was directly comparable with the level of endogenous NPFF mRNA as determined by real-time quantitative RT-PCR. The highest promoter activity was measured when a region from - 552 to - 830 bp of the 5'-flanking region was fused to the constructs, and a potential silencer element was localized between nucleotides -220 and -551. A twofold increase in NPFF mRNA was observed after 72 h of nerve growth factor stimulation of PC12 cells and the region between - 61 and - 214 bp of the 5'-flanking region was found to be responsive to this stimulation. We postulate that control of human NPFF gene expression is the result of both positive and negative regulatory elements and the use of multiple transcription initiation sites.

Molecular models to analyse preprotachykinin-A expression and function

Towards an understanding of the mechanisms controlling Preprotachykinin A (PPT) expression we have generated a variety of molecular models to determine the mechanisms regulating both the tissue-specific and stimulus-inducible expression of the PPT gene. The approaches used include transgenic and virus vector models complementing biochemical analysis of promoter interactions with transcription factors. We have identified and characterised a yeast artificial chromosome (YAC) containing the human PPT gene and generated transgenic mouse lines containing multiple copies of this chromosome on a normal mouse genetic background. This resulted in a pattern of expression in the nervous system remarkably similar to that reported for PPT mRNA in rodents. In addition, this transgenic model has been constructed in such a manner to allow for over expression of tachykinins based on the number of extra alleles in the transgenic mouse. These animals allow us to further examine the function of the tachykinins and acts as a useful complement to existing PPT ablated mice. In vitro we have introduced the proximal PPT promoter in reporter gene constructs into adult neurones in both DRG and the CNS by an adenoassociated virus (AAV) vector or by biolistic transfection respectively. Using the AAV vector we have demonstrated that the proximal promoter can mediate the effects of NGF in adult rat DRG. These models allow us to delineate transcriptional domains involved in the physiological and pathological expression of the PPT gene.

Using c-Fos immunocytochemistry to identify forebrain regions that may inhibit maternal behavior in rats

Evidence indicates there is a neural system that inhibits maternal behavior in virgin rats. It has been suggested that pregnancy hormones promote the onset of maternal behavior by reducing the behavioral influence of this system. The authors used c-Fos immunocytochemistry to identify brain regions more activated by pup exposure in nonmaternal rats than in maternal rats. Previous experiments indicated that some of these regions, such as the posterodorsal medial amygdala and several medial hypothalamic sites, inhibit maternal behavior. For others, such as the ventral lateral septum, dorsal premammillary nucleus, and principal bed nucleus of the stria terminalis, this is the first indication that they could also inhibit maternal responding. These regions have previously been implicated in promoting defensive behaviors, consistent with the finding that nonmaternal rats actively avoid pups. These findings suggest the existence of a neural circuit through which pup exposure could promote defensive responses in virgin rats, and how pregnancy hormones could reduce such activity to stimulate maternal behavior.

Neuronal-specific and nerve growth factor-inducible expression directed by the preprotachykinin-A promoter delivered by an adeno-associated virus vector

The ability to manipulate the expression of genes within neurons provides unique opportunities to study the role of individual gene products in nervous system function. Virus vectors are a potentially rapid tool for the experimental manipulation of gene expression in the mammalian nervous system. However, a block to the use of virus vector systems in neurobiology is often the lack of cell-specific expression of the gene within the nervous system, and the immune and inflammatory responses to both the virus vector and the delivered gene. We have generated an adeno-associated virus vector that exploits the restricted expression pattern of the rat preprotachykinin-A promoter to support reporter gene expression. We demonstrate that this virus has a neuronal-specific expression pattern. Moreover, it is shown for the first time that the proximal rat preprotachykinin-A promoter is nerve growth factor inducible. This virus will be a useful tool to (i) modify neuronal phenotype by expressing therapeutic molecules or antisense nucleic acid and (ii) dissect the signal transduction pathways that regulate promoter function in vivo.

An intronic domain within the rat preprotachykinin-A gene containing a CCCT repetitive motif acts as an enhancer in differentiating embryonic stem cells

Previous attempts by several groups to clone fragments containing intron 2 of the rat preprotachykinin-A gene have generated deletions of various sizes. We have determined that these deletions occur within a specific region of the intron spanning a CCCT tandem repeat domain. We show that this intronic domain is able to support reporter gene expression in mouse embryonic stem (ES) cells that have been induced to differentiate but not in undifferentiated ES cells. No significant expression was observed in the HeLa clonal cell line. This demonstrates that this intron 2 domain is a highly restrictive enhancer and may be associated with differentiation.

Inducible and constitutive transcription factors in the mammalian nervous system: control of gene expression by Jun, Fos and Krox, and CREB/ATF proteins

This article reviews findings up to the end of 1997 about the inducible transcription factors (ITFs) c-Jun, JunB, JunD, c-Fos, FosB, Fra-1, Fra-2, Krox-20 (Egr-2) and Krox-24 (NGFI-A, Egr-1, Zif268); and the constitutive transcription factors (CTFs) CREB, CREM, ATF-2 and SRF as they pertain to gene expression in the mammalian nervous system. In the first part we consider basic facts about the expression and activity of these transcription factors: the organization of the encoding genes and their promoters, the second messenger cascades converging on their regulatory promoter sites, the control of their transcription, the binding to dimeric partners and to specific DNA sequences, their trans-activation potential, and their posttranslational modifications. In the second part we describe the expression and possible roles of these transcription factors in neural tissue: in the quiescent brain, during pre- and postnatal development, following sensory stimulation, nerve transection (axotomy), neurodegeneration and apoptosis, hypoxia-ischemia, generalized and limbic seizures, long-term potentiation and learning, drug dependence and withdrawal, and following stimulation by neurotransmitters, hormones and neurotrophins. We also describe their expression and possible roles in glial cells. Finally, we discuss the relevance of their expression for nervous system functioning under normal and patho-physiological conditions.

A role for the octamer-binding protein in preprotachykinin-A gene expression

A rat Preprotachykinin-A promoter fragment has been previously identified which supports reporter gene activity in primary cultures of adult dorsal root ganglion neurons. That study demonstrated that two promoter domains which exhibit enhancer activity in these neurons are bound by the same classes of transcription factors. Further, the two domains exhibit similarities with respect to the relationship of bound transcription factors within each domain. This suggests that these domains may function in an identical manner or may act synergistically to regulate gene expression. These domains contain recognition motifs for at least three classes of transcription factors: octamer-binding proteins, Sp1-related proteins and an as yet unidentified but distinct factor. The definition of an octamer-binding protein site within these domains is of interest, as this class of factor has recently been suggested as mediating the effect of nerve growth factor in sensory neurons. Nerve growth factor is a well-characterized regulator of preprotachykinin-A gene expression. Definition of these sites within the promoter allows for the design of rational experiments to address the mechanism of transcriptional regulation of the rat preprotachykinin-A gene.

Simultaneous quantitation of substance P-encoding preprotachykinin alternatively spliced mRNAs and substance P receptor NK-1 mRNA by an RNase protection assay

Tachykinins form a family of peptides with neurotransmitter/neuromodulator function. Four tachykinins, substance P, neurokinin A, neuropeptide gamma and neuropeptide K, are encoded by the same PreProTachykinin (PPT) gene. Alternatively spliced mRNAs encode different combinations of these peptides (Brown, E.R., Harlan, R.E., Krause, J.E., Gonadal steroid regulation of substance P (SP) and SP-encoding mRNA in the rat anterior pituitary and hypothalamus, Endocrinology, 126 (1990) 330-340; Krause, J.E., Chirgwin, J.M., Carter, M.S., Xu, Z.S., Hershey, A.D., Three rat preprotachykinin mRNAs encode the neuropeptides substance P and neurokinin A, Proc. Natl. Acad. Sci. USA, 84 (1987) 881-885). The proportion of PPT mRNAs varies from tissue to tissue (Carter, M.S., Krause, J.E., Structure, expression, and some regulatory mechanisms of the rat preprotachykinin gene encoding substance P, neurokinin A, neuropeptide K, and neuropeptide gamma, J. Neurosci., 10 (1990) 2203-2214), and within the rat hypothalamus according to the estrous cycle-related hormonal status (Gautreau, A., Duval, P., Kerdelhué, B., Variations in substance P-encoding preprotachykinin and substance P receptor NK-1 mRNA transcripts in the rat hypothalamus throughout the estrous cycle: a correlation between amounts of beta-preprotachykinin and NK-1 mRNA, Mol. Brain Res., (1997) in press). Tachykinin receptors as well as tachykinins are regulated at the mRNA level. A fully quantitative method is needed to deal with the complex physiological regulation of the tachykinin system. Here, we describe an RNase protection assay that allows the simultaneous quantitation of alternatively spliced PPT mRNAs, Substance P receptor NK-1 mRNA, and glyceraldehyde-3-phosphodehydrogenase (GAPDH) mRNA as an internal control, in the rat hypothalamus. The advantages of this method are its high sensitivity (0.1 pg) and a wide range of linearity (more than 3 orders of magnitude). Moreover, this protocol provides guidelines to set up a quantitative multiprobe RNase protection assay for other genes.

Involvement of a c-fos-dependent mechanism in caffeine-induced expression of the preprotachykinin A and neurotensin/neuromedin N genes in rat striatum

Striatal c-fos induction was blocked by local administration of phosphorothioated c-fos antisense oligonucleotides (AS-ODN) to examine the possible role of caffeine-induced c-fos expression in transcriptional regulation of striatal preproenkephalin, prodynorphin, preprotachykinin A and neurotensin/neuromedin N. Caffeine (100 mg/kg i.p.) induced both c-fos mRNA and Fos-protein, and this induction was significantly attenuated by intrastriatal injection of 4 (but not 1) nmol c-fos AS-ODN. This suggests that, in addition to translational arrest, other mechanisms may be involved in the mediation of antisense action. The action of the AS-ODN was sequence specific. The antisense blockade of c-fos reduced the effect of caffeine on the expression of mRNAs for preprotachykinin A and neurotensin/neuromedin N in the ventrolateral caudate-putamen. Levels of preproenkephalin and prodynorphin transcripts were unaffected. Thus caffeine induction of striatal preprotachykinin A mRNA and neurotensin/neuromedin N mRNA, but not of preproenkephalin mRNA or prodynorphin mRNA, may at least in part be mediated by a pathway involving Fos protein. The findings illustrate the utility of blockade of gene expression with antisense oligonucleotides for in vivo studies of drug actions.

The molecular biology of preprotachykinin-A gene expression

The expression of neuropeptides is largely tissue-specific and under strictly regulated and complex control. In view of the diversity of neuronal phenotypes, with concomitant plasticity of gene expression within any phenotype, it is obvious that there is coordinated activation and repression of genes. One of the central observations from these studies is that neuropeptide gene expression is dependent upon the combinatorial interaction of multiple transcription factors with the regulatory elements which determine mRNA synthesis. These factors mediate both tissue specific and stimulus inducible gene expression. We will illustrate some of the mechanisms that regulate neuropeptide gene expression utilizing our own studies on the rat preprotachykinin-A gene (rPPT) and, where appropriate, expand on the generality of these findings to other neuropeptide genes.

Neuronal-specific gene expression--the interaction of both positive and negative transcriptional regulators

Gene expression patterns in neurons are complex and are modulated in response to multiple extracellular stimuli. In addition, during development and as neurons differentiate into distinct neuronal phenotypes, there is a co-ordinated activation and repression of a variety of genes. It is becoming increasingly evident that negative regulatory elements are present in neuronal-specific promoters. These elements have been shown, in part, to restrict promoter activity to the correct physiological cell type, both in transient transfection and in transgenic mouse models. Repression can be effected by different mechanisms depending on location within the promoter of silencer complexes and their relationship to other bound transcription factors. This review will discuss the molecular mechanisms regulating promoter function, in particular: (1) the combinatorial interaction between transcription factors which generate regulated promoter function; and (2) the restriction of promoter function to the correct cell type by bound repressor molecules. Determination of the mechanism of regulated gene expression will allow advances in gene therapy and definition of novel targets for pharmaceutical intervention. At the more basic level, functional dissection of the promoters of specific neuronal expressed genes will provide information of importance in two key areas of neurobiology: (1) the mechanism by which extracellular factors, such as neurotrophins and cytokines, regulate gene expression; (2) the events which lead to the tissue-specific expression of genes in subpopulations of neurons, both in the adult and during development.

An upstream stimulatory factor (USF) binding motif is critical for rat preprotachykinin-A promoter activity in PC12 cells

We demonstrate the presence of a functional E box motif in the proximal rat preprotachykinin-A (rPPT) promoter. This element (spanning nucleotides -67 to -47) exhibits the sequence 5'-CACGTG-3' which is recognized and bound by the basic helix-loop-helix family of regulatory proteins. We also show that at least one of the factors bound to this rPPT promoter element in both HeLa and PC12 nuclear extract is the ubiquitously expressed transcription factor, the upstream stimulatory factor (USF). Mutation of this element by insertion of a 10 bp linker into the E box motif, in an rPPT promoter fragment spanning -865 to +92, destroys the ability of this promoter fragment to support reporter gene expression in a PC12 cell model of rPPT promoter activity. The data indicate that this rPPT E box element is likely to function as an important cis-regulatory domain in the rPPT promoter.