Regulation of the preprotachykinin-I gene promoter through a protein kinase A-dependent, cyclic AMP response element-binding protein-independent mechanism

Developmental regulation of TAC1 in peptidergic-induced human mesenchymal stem cells: implication for spinal cord injury in zebrafish

Human mesenchymal stem cells (MSCs) are easy to expand, are relatively safe, and can be transplanted in allogeneic recipients as off-the-shelf cells. MSCs can be induced to form functional peptidergic neurons and express the neurotransmitter gene, TAC1. Expression of TAC1 requires that the repressor gene, RE-1 silencing transcription factor (REST), is decreased. This study investigated the molecular pathway in TAC1 induction as MSCs differentiated into neurons and then applied the findings in a model of spinal cord injury (SCI) in zebrafish. We studied the developmental roles of the 2 cAMP response element (CRE) sites: CRE1 and CRE2. Activator protein-1 (AP-1) binding site overlaps with CRE2 (CRE2/AP-1). Reporter gene studies with the 5' regulatory region of TAC1 containing wild-type or mutant CRE sites and, parallel studies with ectopically expressed inhibitor of cAMP proteins (inducible cAMP early repressor) indicated that CRE1 and CRE2/AP-1 are activated at days 6 and 12, respectively. Studies with protein kinase-A (PKA) and Jun N-terminal kinase (JNK) inhibitors in the reporter gene studies, chromatin immunoprecipation assay, and ectopic expression of REST indicated the following pathways: Decrease of REST activated upstream c-Jun N-terminal kinase (JNK). In turn, JNK activated ATF-2 and AP-1 for interaction with CRE1 and CRE2/AP-1, respectively. To apply the finding to SCI, we transplanted 6-day-induced MSCs in transgenic HB9-GFP zebrafish larvae with SCI, in the presence or absence of JNK inhibitors. Imaging and functional studies showed significant improvement in the fish. The repair mechanism involved the activation of JNK. The findings have long-term implications for SCI repair with MSCs.

Chronic methamphetamine exposure suppresses the striatal expression of members of multiple families of immediate early genes (IEGs) in the rat: normalization by an acute methamphetamine injection

RATIONALE

Repeated injections of cocaine cause blunted responses to acute cocaine challenge-induced increases in the expression of immediate early genes (IEGs).

OBJECTIVES

The aim of this study was to test if chronic methamphetamine (METH) exposure might cause similar blunting of acute METH-induced increases in IEG expression.

RESULTS

Repeated saline or METH injections were given to rats over 14 days. After 1 day of withdrawal, they received a single injection of saline or METH (5 mg/kg). Acute injection of METH increased c-fos, fosB, fra2, junB, Egr1-3, Nr4a1 (Nur77), and Nr4a3 (Nor-1) mRNA levels in the striatum of saline-pretreated rats. Chronic METH treatment alone reduced the expression of AP1, Erg1-3, and Nr4a1 transcription factors below control levels. Acute METH challenge normalized these values in METH-pretreated rats. Unexpectedly, acute METH challenge to METH-pretreated animals caused further decreases in Nr4a2 (Nurr1) mRNA levels. In contrast, the METH challenge caused significant but blunted increases in Nr4a3 and Arc expression in METH-pretreated rats. There were also chronic METH-associated decreases in the expression of cAMP responsive element binding protein (CREB) which modulates IEG expression via activation of the cAMP/PKA/CREB signal transduction pathway. Chronic METH exposure also caused significant decreases in preprotachykinin, but not in prodynorphin, mRNA levels.

CONCLUSIONS

These results support the accumulated evidence that chronic administration of psychostimulants is associated with blunting of their acute stimulatory effects on IEG expression. The METH-induced renormalization of the expression of several IEGs in rats chronically exposed to METH hints to a potential molecular explanation for the recurrent self-administration of the drug by human addicts.

Long-range regulatory synergy is required to allow control of the TAC1 locus by MEK/ERK signalling in sensory neurones

Changes in the expression of the neuropeptide substance P (SP) in different populations of sensory neurones are associated with the progression of chronic inflammatory disease. Thus, understanding the genomic and cellular mechanisms driving the expression of the TAC1 gene, which encodes SP, in sensory neurones is essential to understanding its role in inflammatory disease. We used a novel combination of computational genomics, primary-cell culture and mouse transgenics to determine the genomic and cellular mechanisms that control the expression of TAC1 in sensory neurones. Intriguingly, we demonstrated that the promoter of the TAC1 gene must act in synergy with a remote enhancer, identified using comparative genomics, to respond to MAPK signalling that modulates the expression of TAC1 in sensory neurones. We also reveal that noxious stimulation of sensory neurones triggers this synergy in larger diameter sensory neurones – an expression of SP associated with hyperalgesia. This noxious stimulation of TAC1 enhancer-promotor synergy could be strongly blocked by antagonism of the MEK pathway. This study provides a unique insight into the role of long-range enhancer-promoter synergy and selectivity in the tissue-specific response of promoters to specific signal transduction pathways and suggests a possible new avenue for the development of novel anti-inflammatory therapies.

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.

D1 receptor regulation of preprotachykinin-A gene by extracellular signal-regulated kinase pathway in striatal cultures

In animal models of Parkinson's disease, a supersensitive response to dopamine (DA) is associated with a switch in the coupling of striatal DA D1 receptors from a cyclic AMP/protein kinase A signaling pathway to one involving extracellular signal-regulated kinase/mitogen-associated protein kinase. In this study, we found that generation of organotypic striatal cultures, with concomitant loss of DA innervation, led to a downregulation in preprotachykinin-A gene expression, which was reinstated by D1 receptor activation in an extracellular signal-regulated kinase/mitogen-associated protein kinase-dependent manner. These data demonstrate that acute organotypic slice cultures recapitulate important changes in D1 receptor-mediated signal transduction seen in DA-denervated animals, providing a valuable model system to study denervation effects on DA signaling and striatal gene expression.