Molecular cloning of a novel transcriptional repressor protein of the rat type 1 vasoactive intestinal peptide receptor gene

A functional polymorphism of the vasoactive intestinal peptide receptor 1 gene correlates with the presence of HLA-B*2705 in Sardinia

The association of HLA-B27 with ankylosing spondylitis (AS) is the strongest among all inflammatory diseases. However, the exact role of these molecules in disease pathogenesis is still unknown. The existence of HLA-B27 variants rarely found in patients introduces a further level of complexity. It is now accepted that other genes of minor impact contribute to modify disease susceptibility and these genes might be diverse in different populations depending on the genetic background. We report here a study performed in Sardinia, an outlier population in which two major HLA-B27 subtypes are present, B (*)2705 strongly associated with AS and B (*)2709 which is not, and show the co-occurrence of the B (*)2705 allele with a single nucleotide polymorphism (SNP) mapping at 3'-UTR of the receptor 1 (VIPR1) for the vasoactive intestinal peptide (VIP), a neuropeptide with anti-inflammatory properties. This same SNP is associated with a different kinetics of down-modulation of the VIPR1 mRNA in monocytes after exposure to lipopolysaccharide (P=0.004). This particular setting, HLA-B (*)2705 and a functional polymorphism in VIPR1 gene, might be due to a founder effect or might be the result of a selective pressure. Irrespectively, the consequent downregulation of this receptor in the presence of a 'danger' signal might influence susceptibility to AS.

Differential expression of vasoactive intestinal peptide and its functional receptors in human osteoarthritic and rheumatoid synovial fibroblasts

OBJECTIVE

Vasoactive intestinal peptide (VIP) has shown potent antiinflammatory effects in murine arthritis and ex vivo in human rheumatoid arthritis (RA) synovial cells. To investigate the potential endogenous participation of this system in the pathogenesis of RA, we analyzed the expression and regulation of VIP and its functional receptors in human fibroblast-like synoviocytes (FLS) from patients with osteoarthritis (OA) and patients with RA.

METHODS

The expression of VIP was studied by reverse transcription-polymerase chain reaction (RT-PCR), enzyme immunoassay, and immunofluorescence in cultured FLS, and by immunohistochemical analysis in synovial tissue. The expression and function of the potential VIP receptors in FLS were studied by RT-PCR, determination of intracellular cAMP production, cell membrane adenylate cyclase (AC) activity, and interleukin-6, CCL2, and CXCL8 production in response to VIP or specific agonists and antagonists.

RESULTS

VIP expression was detected in human FLS at the messenger RNA and protein levels, and it was significantly decreased in RA FLS compared with OA FLS. VIP receptor type 1 (VPAC1) was the dominant AC-coupled receptor in OA FLS, in contrast with RA FLS, in which VPAC2 was dominant. Tumor necrosis factor alpha-treated OA FLS reproduced the VIP and VPAC receptor expression pattern of RA FLS. The antagonistic effects of VIP on FLS proinflammatory factor production were reproduced by VPAC1- and VPAC2-specific agonists in OA FLS and RA FLS, respectively.

CONCLUSION

VIP expression is down-regulated in RA and in tumor necrosis factor alpha-treated FLS, suggesting that down-regulation of this endogenous antiinflammatory factor may contribute to the pathogenesis of RA. In RA FLS, VPAC2 mediates the antiinflammatory effects of VIP, suggesting that VPAC2 agonists may be an alternative to VIP as antiinflammatory agents.

Morphological relationships between peptidergic nerve fibers and immunoglobulin A-producing lymphocytes in the mouse intestine

Immunoglobulin A (IgA) lymphocytes are present close to the nerve fibers in the lamina propria of the small intestine, and the administration of lipopolysaccharides (LPSs) increases the number of these cells and IgA secretion to the lumen. In the present study, we demonstrated that the nerve fibers immunoreactive for vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), and calcitonin gene-related peptide (CGRP) were close to the IgA lymphocytes in the mouse ileum lamina propria. Three hours after intraperitoneal administration of LPSs, IgA lymphocytes close to VIP nerve fibers, those close to basement membrane, and those close to both VIP nerve fibers and basement membrane were increased in number. Further, all IgA lymphocytes seen in the ileum lamina propria expressed the receptors for VIP, VIPR1, and VIPR2. Electron microscopy revealed that varicosities were in close apposition to the lymphocyte plasma membrane. The present study suggests that VIP/NPY/CGRP neurons in the submucosal plexus have a close anatomical relationship to IgA lymphocytes, playing a role in the secretion of IgA and intestinal fluid in response to stimulation by lipopolysaccharides, pathogens, or toxins.

The significance of vasoactive intestinal peptide in immunomodulation

First identified by Said and Mutt some 30 years ago, the vasoactive intestinal peptide (VIP) was originally isolated as a vasodilator peptide. Subsequently, its biochemistry was elucidated, and within the 1st decade, their signature features as a neuropeptide became consolidated. It did not take long for these insights to permeate the field of immunology, out of which surprising new attributes for VIP were found in the last years. VIP is rapidly transforming into something more than a mere hormone. In evolving scientifically from a hormone to a novel agent for modifying immune function and possibly a cytokine-like molecule, VIP research has engaged many physiologists, molecular biologists, biochemists, endocrinologists, and pharmacologists and it is a paradigm to explore mutual interactions between neural and neuroendocrine links in health and disease. The aim of this review is firstly to update our knowledge of the cellular and molecular events relevant to VIP function on the immune system and secondly to gather together recent data that support its role as a type 2 cytokine. Recognition of the central functions VIP plays in cellular processes is focusing our attention on this "very important peptide" as exciting new candidates for therapeutic intervention and drug development.

VIP receptor 1 (VPAC1) promoter targets the expression of a reporter gene to cerebellum and adrenal medulla in transgenic mice

Vasoactive intestinal peptide (VIP) is a neurotransmitter with neurotropic effects. VIP functions through two distinct G-protein-coupled receptor subtypes (VPAC1 and VPAC2). We have demonstrated expression of VPAC1 in pediatric nervous system tumors, including medulloblastoma arising in the cerebellum and neuroblastoma arising in the adrenal medulla. More recently, we have reported the differentiation of neuroblastoma cells by upregulation of VIP type 1 receptor suggesting a role for VPAC1 in neuronal development. To understand the molecular mechanisms regulating VPAC1 expression in both cerebellum and adrenal medulla, we have cloned the human VPAC1 gene and sequenced 2.6-kb of the 5'-flanking sequence. Expression of the luciferase reporter gene under the control of this 2.6-kb human VPAC1 promoter was induced 35-fold in a human medulloblastoma cell line (DAOY) and 36-fold in a human neuroblastoma cell line (SKNSH). Analysis of 5'-unidirectional deletion derivatives of the 2.6-kb fragment demonstrated that a 241-bp sequence immediately upstream of the VPAC1 coding region retains high activity, suggesting that it contains the core promoter region. Quantitative RT-PCR analysis demonstrated that VPAC1 is expressed in mouse cerebellar and adrenal tissues. The VPAC1 promoter also directed expression of a reporter gene in cerebellum and adrenal medulla in transgenic mice. Along with our previous findings, these results suggest that VPAC1 may play a functional role in development of both cerebellum and adrenal medulla.

VIP- and PACAP-mediated immunomodulation as prospective therapeutic tools

The immune system and the brain continuously signal to each other, often along the same pathways, which might explain the connection between immunity, the brain and disease. Neuropeptides and their receptors represent part of this communication network, and recent work has examined their relevance to health, proving a potentially crucial clinical significance. The structurally related neuropeptides, vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP), are emerging as a means of fine tuning in the maintenance a balanced steady state in the immune system. Murine knockout and transgenic models for a VIP receptor suggest that VIP is an endogenous anti-inflammatory mediator with characteristics resembling those of a T-helper-2 cytokine. Thus, through molecular mechanisms that are being discovered, VIP might extend the range of therapeutic treatments available for various disorders, including acute and chronic inflammatory diseases, septic shock and autoimmune diseases.

Searching for DNA-protein interactions by lambda phage display

We applied phage display technology to DNA-protein interaction studies. A cDNA expression library displayed on the surface of bacteriophage lambda was generated from the highly differentiated MMH E14 murine hepatic cell line. Selection of this library using the promoter sequence of the liver-enriched transcription factor HNF1alpha gene as ligate identified DNA-binding domains specifically interacting with different regions of this regulatory sequence. One of the selected phage showed 100% identity to a DNA-binding domain shared by differentiation specific element-binding protein, vasoactive intestinal peptide receptor-repressor protein and replication factor C and was further investigated. Specific binding of the selected protein domain was confirmed in a phage-independent context. By combining ELISA and South-Western assays using the selected phage and a bacterially expressed glutathione-S-transferase protein fused to the encoded DNA-binding domain, an array of multiple adjacent DNA-binding sites sharing a common consensus motif was identified. The strategy described represents a powerful tool to identify proteins that bind to DNA regulatory elements.

Vasoactive intestinal polypeptide as mediator of asthma

Vasoactive intestinal polypeptide (VIP) is one of the most abundant, biologically active peptides found in the human lung. VIP is a likely neurotransmitter or neuromodulator of the inhibitory non-adrenergic non-cholinergic airway nervous system and influences many aspects of pulmonary biology. In human airways VIP-immunoreactive nerve fibres are present in the tracheobronchial airway smooth muscle layer, the walls of pulmonary and bronchial vessels and around submucosal glands. Next to its prominent bronchodilatory effects, VIP potently relaxes pulmonary vessels. The precise role of VIP in the pathogenesis of asthma is still uncertain. Although a therapy using the strong bronchodilatory effects of VIP would offer potential benefits, the rapid inactivation of the peptide by airway peptidases has prevented effective VIP-based drugs so far and non-peptide VIP-agonists did not reach clinical use.

Transcriptional repressor of vasoactive intestinal peptide receptor mediates repression through interactions with TFIIB and TFIIEbeta

The transcriptional repressor for rat vasoactive-intestinal-polypeptide receptor 1 (VIPR-RP) is a recently characterized transcription factor that belongs to a family of proteins, which include components of the DNA replication factor C complex. In this study, I investigated the mechanisms by which VIPR-RP represses transcription. I show here that transcriptional repression by VIPR-RP is mediated by a histone deacetylase-independent mechanism. I provide evidence that VIPR-RP makes direct physical contacts with two proteins of the basal transcription apparatus, the transcription factors TFIIB and TFIIEbeta. The interaction with TFIIB is mediated by the N-terminal 180 amino acids, whereas the interactive domain with TFIIEbeta is located between residues 367 and 527 of VIPR-RP. Using gel mobility-shift assays I demonstrated that interaction between VIPR-RP and TFIIB prevents the recruitment of TFIIB into a DNA-TATA-box-binding protein complex. My results indicate that VIPR-RP mediates transcriptional repression through direct interactions with the general transcription machinery.

Molecular characterization of the VIP receptor transcriptional repressor protein

The rat type 1 VIP receptor transcriptional repressor protein (VIPR-RP) is a recently isolated novel transcription factor. In the study reported here, the functional domains of VIPR-RP were characterized. To map the DNA binding domain, various regions of VIPR-RP were either transcribed and translated in vitro or expressed in and purified from E. Coli as a glutathione S-transferase (GST) fusion. The ability of the truncated proteins to bind to VIPR-RP specific binding sequence was tested by gel mobility shift assays. The results indicated that the amino acid sequences between 367 and 475 play an essential role for VIPR-RP DNA binding. To determine the amino acid sequences required for transcriptional repression, fusion proteins containing the GAL4 DNA binding domain and various parts of VIPR-RP were constructed, and their ability to repress transcription of the reporter gene containing GAL4 DNA binding sequences were tested in transiently transfected COS7 cells. The results showed that VIPR-RP contains two separate transcriptional repression domains located between amino acids 50 to 101 and 470 to 527.

Vasoactive intestinal peptide (VIP) receptor type 2 (VPAC2) is the predominant receptor expressed in human thymocytes

Vasoactive intestinal peptide (VIP) binding sites have been identified in the human thymus, but the receptor subtype and how these receptors are distributed in the human thymus subsets is unknown. To assess gene expression, distribution, and receptor regulation of the two G-protein-associated VIP receptors, VPAC1 and VPAC2 mRNAs were quantified using a novel fluorometric-based kinetic (real-time) RT-PCR. Bulk and fractionated thymocytes were stimulated via the TCR/CD3 receptor complex and anti-CD28. Our results demonstrate that thymocytes express higher levels of VPAC2 compared to VPAC1 expression in bulk thymocytes, CD4+CD8+ selected double positives (DP), and CD8 depleted thymocytes. Double negative cells express low levels of VPAC2 mRNA. We demonstrate T-cell activation-dependent down-regulation of VPAC1, but not VPAC2, in human thymocytes. This study reports the first direct evidence of a differential distribution and selective regulation of VPAC1 and VPAC2 gene expression in normal human thymocyte subsets.

Regulation of vasoactive intestinal peptide receptor expression in developing nervous systems

Vasoactive intestinal peptide (VIP) is a 28-amino acid peptide that has several functions, including the regulation of water and electrolyte secretion, hormone and cytokine release, bronchodilitation, and neurogenesis. VIP effects are mediated by specific G-protein coupled receptors. Three distinct receptor subtypes, with differing affinity for VIP, have been cloned and characterized as receptors 1 and 2 (VPAC1 and VPAC2) and pituitary adenylate cyclase activating polypeptide receptor (PAC1). Our laboratory has demonstrated that upregulation of VPAC1 in SK-N-SH neuroblastoma cells results in marked shift in cell type to the glial lineage with a corresponding loss of neuronal lineage and suppression of xenograft tumor growth. To understand the molecular mechanisms responsible for regulation of the VPAC1 gene in neuronal lineage, we have cloned and sequenced 2.6-kb of the 5'-flanking sequences of the human VPAC1 gene. Sequence analysis demonstrated that the human VPAC1 promoter sequence contains putative binding sites for several known transcription factors, including Sp1, NFkB, and cETS-1. To study the temporal and spatial expression pattern of human VPAC1 promoter sequences, we have generated transgenic mice expressing the bacterial beta-galactosidase gene under the control of the 2.6-kb 5'-flanking and promoter sequence of the human VPAC1 gene. Transgene expression was detected in brain, spinal cord, and lung in 14-day-old animals. Taken together, these results demonstrate that VPAC1 may play an important role in the nervous system, and suggest a role for VIP in neuronal differentiation.

Selective gene expression and activation-dependent regulation of vasoactive intestinal peptide receptor type 1 and type 2 in human T cells

Vasoactive intestinal peptide (VIP) has potent antiproliferative and anti-inflammatory functions in the immune system. Two structurally distinct G-protein-associated receptors, VIP receptor type 1 (VPAC1) and VIP receptor type 2 (VPAC2), mediate the biological effects of VIP. The regulation of VIP receptor gene expression and the distribution of these receptors in different compartments of the human immune systems are unknown. This study reports, for the first time, a quantitative analysis of VPAC1 and VPAC2 mRNA expression in resting and activated T cells as well as in resting monocytes. Purified human peripheral blood CD4(+) T cells and CD8(+) T cells were stimulated via the TCR/CD3 receptor complex. Using the novel fluorometric-based kinetic (real-time) RT-PCR, we determined that VPAC1 is constitutively expressed in resting T cells and monocytes; the levels of expression were significantly higher in monocytes and CD4(+) T cells than in CD8(+) T cells. VPAC1 mRNA expression is significantly higher relative to VPAC2 in resting CD4(+) T cells and CD8(+) T cells. VPAC2 is expressed at very low levels in resting T cells but is not detectable in resting monocytes. In vitro stimulation of Th cells with soluble anti-CD3 plus PMA induced a T cell activation-dependent down-regulation of VPAC1. VPAC1 is down-regulated under conditions of optimal T cell stimulation. Our results suggest that selective VIP effects on T cell function may be mediated via selective expression of VPAC1 and VPAC2 on T cells and monocytes. Furthermore, down-regulation of VPAC1 in CD4(+) T cell subpopulations is highly correlated with T cell activation.

The human vasoactive intestinal peptide/pituitary adenylate cyclase-activating peptide receptor 1 (VPAC1) promoter: characterization and role in receptor expression during enterocytic differentiation of the colon cancer cell line Caco-2Cl.20

The basic organization of the human vasoactive intestinal peptide/pituitary adenylate cyclase-activating peptide receptor (VPAC) 1 promoter was investigated after cloning the 5'-flanking region (1.4 kb) of the VPAC1 gene from a human genomic library. Subsequent functional analysis of various deletions of the 5'-flanking sequence, subcloned upstream of a luciferase reporter gene, was carried out in HT-29 cells. The minimal promoter region identified encompasses the -205/+76 sequence and contains a crucial CCAAT box (-182/-178) and a GC-rich sequence. Moreover a region (-1348/-933) containing a silencer element was identified. We previously showed that the expression of the VPAC1 receptor binding site is strictly dependent upon the enterocytic differentiation of human colon cancer Caco-2 cells [Laburthe, Rousset, Rouyer-Fessard, Couvineau, Chantret, Chevalier and Zweibaum (1987) J. Biol. Chem. 262, 10180-10184]. In the present study we show that VPAC1 mRNA increases dramatically when Caco-2Cl.20 cells differentiate, as measured by RNase protection assays and reverse transcriptase-PCR. A single transcript species of 3 kb is detected in differentiated cells by Northern-blot analysis. Accumulation of VPAC1 receptor mRNA is due to a 5-fold increase of transcription rate (run-on assay) without a change in mRNA half-life (9 h). Stable transfections of various constructs in Caco-2Cl.20 cells and subsequent analysis of reporter gene expression, during the enterocytic differentiation process over 25 days of culture, further indicated that the -254/+76 5'-flanking sequence is endowed with the regulatory element(s) necessary for transcriptional regulation of VPAC1 during differentiation. Altogether, these observations provide the first characterization of the basic organization of the human VPAC1 gene promoter and unravel the crucial role of a short promoter sequence in the strict transcriptional control of VPAC1 expression during differentiation of human colon cancer Caco-2 cells.

Phosphorylation modulates the function of the vasoactive intestinal polypeptide receptor transcriptional repressor protein

The transcriptional repressor for rat vasoactive intestinal polypeptide receptor 1 (VIPR-RP) is a recently isolated transcription factor. In this study, we have characterized the functional domains of VIPR-RP and the importance of phosphorylation on VIPR-RP function. Using various regions of VIPR-RP in gel mobility shift assays, we show that the amino acid sequences between positions 367 and 475 play an essential role for VIPR-RP DNA binding. Transient transfection of fusion constructs containing GAL4 DNA binding domain and different parts of VIPR-RP indicated that there are two separate transcriptional repression domains in VIPR-RP, located between amino acids 50 and 101 and between 469 and 527. We demonstrated that VIPR-RP is phosphorylated in vitro by casein kinase II on Ser-69/71 and Thr-110, and by cAMP-dependent kinase on Ser-245/361. Furthermore, by site-directed mutagenesis, we show that phosphorylation of the casein kinase II sites potentiates VIPR-RP transcriptional repression activity by enhancing its nuclear translocation, and that phosphorylation by cAMP-dependent kinase inhibits VIPR- RP transcriptional repression function without affecting its subcellular localization. These observations suggest that phosphorylation plays an important role in regulating VIPR-RP function.