Altered regulation of 5-HT1A receptors is implicated in mood disorders such as anxiety and major depression. To provide insight into its transcriptional regulation, we previously identified a novel DNA element [14 bp 5'-repressor element (FRE)] of the 5-HT1A receptor gene that mediates repression in neuronal and non-neuronal cells (Ou et al., 2000). We have now cloned a novel DNA binding protein [five' repressor element under dual repression binding protein-1 (Freud-1)] that binds to FRE to mediate repression of the 5-HT1A receptor or heterologous promoters. Freud-1 is evolutionarily conserved and contains two DM-14 basic repeats, a predicted helix-loop-helix DNA binding domain, and a protein kinase C conserved region 2 (C2)/calcium-dependent lipid binding (CalB) calcium/phospholipid binding domain. An intact CalB domain was required for Freud-1-mediated repression. In serotonergic raphe cells, overexpression of Freud-1 repressed the 5-HT1A promoter and decreased 5-HT1A receptor protein levels, whereas transfection of antisense to Freud-1 derepressed the 5-HT1A gene and increased 5-HT1A receptor protein expression. Calcium-dependent signaling blocked Freud-1-FRE binding and derepressed the 5-HT1A promoter. Treatment with inhibitors of calmodulin or CAM-dependent protein kinase reversed calcium-mediated inhibition of Freud-1. Freud-1 RNA and protein were present in raphe nuclei, hippocampus, cortex, and hypothalamus, and Freud-1 protein was colocalized with 5-HT1A receptors, suggesting its importance in regulating 5-HT1A receptors in vivo. Thus, Freud-1 represents a novel calcium-regulated repressor that negatively regulates basal 5-HT1A receptor expression in neurons and may play a role in the altered regulation of 5-HT1A receptors associated with anxiety or major depression.

The serotonin-1A (5-HT 1A ) receptor is the primary somatodendritic autoreceptor that inhibits the activity of serotonergic raphe neurons and is also expressed in nonserotonergic cortical and limbic neurons. Alterations in 5-HT 1A receptor levels are implicated in mood disorders, and a functional C(-1019)G 5-HT 1A promoter polymorphism has been associated with depression, suicide, and panic disorder. We examined the cell-specific activity of identified transcription factors, human nuclear deformed epidermal autoregulatory factor-1 (DEAF-1)-related (

Regulation of serotonin (5-HT)1A receptor expression in brain is implicated in mood disorders such as depression and anxiety. Transcriptional activity of the human 5-HT1A receptor gene was strongly repressed by a negative regulatory region containing a consensus repressor element-1 (RE-1) and two copies of the dual repressor element (DRE) identified in the rat 5-HT1A receptor gene. REST/NRSF, a silencer of neuronal genes, bound the 5-HT1A RE-1 and repressed the 5-HT1A promoter. Inactivation of RE-1 completely abolished RESTmediated repression, but resulted in only partial (15-50%) de-repression of basal 5-HT1A promoter activity. The human 5-HT1A DRE sequences bound specifically to the novel repressor Freud-1 (5¢repressor element under dual repression binding protein-1) and conferred repressor activity at 5-HT1A or SV40 promoters. In 5-HT1A-negative cells [L6, human embryonic kidney (HEK) 293], the histone deacetylase (HDAC) inhibitor trichostatin A (TSA) abolished repression mediated by both RE-1/REST and DRE/Freud-1, and induced almost complete de-repression of the 5-HT1A gene. By contrast, in 5-HT1A-expressing neuronal cells (RN46A, SN-48) TSA blocked RE-1/REST repression, but did not affect DRE/Freud-1-mediated repression. Thus in contrast to REST, Freud-1 mediates HDAC-independent repression of the 5-HT1A receptor promoter in neuronal 5-HT1A-positive cells, suggesting that HDAC recruitment might influence neuron-specific gene expression by further silencing expression in non-neuronal tissue.

Serotonin1A (5-HT1A) receptors are reported altered in the brain of subjects with major depressive disorder (MDD). Recent studies have identified transcriptional regulators of the 5-HT1A receptor and have documented gender-specific alterations in 5-HT1A transcription factor and 5-HT1A receptors in female MDD subjects. The 5′ repressor element under dual repression binding protein-1 (Freud-1) is a calcium-regulated repressor that negatively regulates the 5-HT1A receptor gene. This study documented the cellular expression of Freud-1 in the human prefrontal cortex (PFC) and quantified Freud-1 protein in the PFC of MDD and control subjects as well as in the PFC of rhesus monkeys chronically treated with fluoxetine. Freud-1 immunoreactivity was present in neurons and glia and was co-localized with 5-HT1A receptors. Freud-1 protein level was significantly decreased in the PFC of male MDD subjects (37%, p=0.02) relative to gender-matched control subjects. Freud-1 protein was also reduced in the PFC of female MDD subjects (36%, p=0.18) but was not statistically significant. When the data was combined across genders and analysed by age, the decrease in Freud-1 protein level was greater in the younger MDD subjects (48%, p=0.01) relative to age-matched controls as opposed to older depressed subjects. Similarly, 5-HT1A receptor protein was significantly reduced in the PFC of the younger MDD subjects (48%, p=0.01) relative to age-matched controls. Adult male rhesus monkeys administered fluoxetine daily for 39 wk revealed no significant change in cortical Freud-1 or 5-HT1A receptor proteins compared to vehicle-treated control monkeys. Reduced protein expression of Freud-1 in MDD subjects may reflect dysregulation of this transcription factor, which may contribute to the altered regulation of 5-HT1A receptors observed in subjects with MDD. These data may also suggest that reductions in Freud-1 protein expression in the PFC may be associated with early onset of MDD.

The CC2D1A/Freud-1 gene has recently been linked to non-syndromic mental retardation and a short isoform of mouse Five prime REpressor Under Dual repression binding protein 1 (Freud-1) can repress the serotonin-1A (5-HT1A) receptor gene in rodent cells. In this study, we addressed the expression, localization and regulation of the human 5-HT1A receptor gene by a long isoform of human Freud-1 protein (Freud-1L). We show that human CC2D1A/Freud-1 RNA is expressed in brain and peripheral tissues and encodes short and long isoforms, which differ by an upstream in-frame translational start site. Whereas previous studies identified the short isoform of Freud-1 as the predominant isoform in rodent cells, we demonstrate that the long isoform is more abundant in human cells, especially in the nuclear fraction. The nuclear localization of Freud-1L was enriched upon inhibition of chromosome region maintenance 1/exportin 1-dependent nuclear export, indicating a dynamic regulation of Freud-1 nuclear localization. Consistent with a functional role in the nucleus, human Freud-1L bound specifically to its dual repressor element in the 5-HT1A receptor gene in vitro and repressed transcription from these sites. Importantly, chromatin immunoprecipitation using antibodies specific for human Freud-1L demonstrated that it is bound to the dual repressor element in chromatin, indicating a functional role in regulating the basal expression of the 5-HT1A receptor gene. Taken together, these results indicate that both the short and long isoforms of Freud-1 are expressed, although Freud-1L is the major isoform that regulates the human 5-HT1A receptor gene. Disruption of transcriptional regulation by mutation of Freud-1 may play a role in abnormal brain function leading to mental retardation.

Freud-1/CC2D1A is a transcriptional repressor of the serotonin-1A receptor gene and was recently genetically linked to non-syndromic mental retardation. To identify new Freud-1 gene targets, data base mining for Freud-1 recognition sequences was done. A highly homologous intronic element (D2-DRE) was identified in the human dopamine-D2 receptor (DRD2) gene, and the role of Freud-1 in regulating the gene at this site was assessed. Recombinant Freud-1 bound specifically to the D2-DRE, and a major protein-D2-DRE complex was identified in nuclear extracts that was supershifted using Freud-1-specific antibodies. Endogenous Freud-1 binding to the D2-DRE in cells was detected using chromatin immunoprecipitation. The D2-DRE conferred strong repressor activity in transcriptional reporter assays that was dependent on the Freud-1 recognition sequence. In three different human cell lines, the level of Freud-1 protein was inversely related to DRD2 expression. Knockdown of endogenous Freud-1 using small interfering RNA resulted in an up-regulation of DRD2 RNA and binding sites, demonstrating a crucial role for Freud-1 in DRD2 regulation. A previously uncharacterized single nucleotide A/G polymorphism (rs2734836) was located adjacent to the D2-DRE and conferred allele-specific Freud-1 binding and repression, with the major G-allele having reduced activity. These studies demonstrate a key role for Freud-1 to regulate DRD2 expression and provide the first mechanistic insights into its transcriptional regulation. Allele-specific regulation of DRD2 expression by Freud-1 may possibly associate with psychiatric disorders or mental retardation.Dopamine-D2 receptors function as both pre-synaptic autoreceptors and post-synaptic receptors, and play key roles in regulating dopaminergic neurotransmission. Increased levels of dopamine-D2 receptors or dopaminergic hyperactivity have been implicated in schizophrenia (1-3), and most antipsychotic drugs inhibit dopamine-D2 receptors (4 -6). Although transcriptional regulation of the rat dopamine D2 receptor (DRD2) 5 gene has been examined, very little is known regarding the regulation of the human DRD2 gene. A polymorphism in the putative DRD2 promoter confers decreased transcriptional activity and has been negatively associated with schizophrenia (7). However, the transcriptional mechanisms for regulation of the human DRD2 gene have yet to be elucidated.To identify new transcriptional regulators in the nervous system, we previously characterized the serotonin-1A (5-HT1A) receptor promoter region and identified a novel dual repressor element (DRE) that negatively regulates its expression (8, 9). The DRE consists of adjacent and partially overlapping repressor elements: 5Ј-repressor element (FRE; major regulator in neuronal cells) and 3Ј-repressor element (9). Analysis of DREbinding proteins revealed that a novel protein, Freud-1 (Five prime repressor under dual repression-binding protein-1)/ CC2D1A (Coiled-coil and C2 Domain containing 1A) binds to and represses the 5-HT1A receptor gene throug...

The CC2D1A gene family consists of two homologous genes, Freud-1/CC2D1A and Freud-2/CC2D1B, that share conserved domains, including several DM14 domains that are specific to this protein family, a C-terminal helix-loop-helix domain, and a C2 calcium-dependent phospholipid binding domain. Although the function of Freud-2 is unknown, Freud-1 has been shown to function as a transcriptional repressor of the serotonin-1A receptor gene that binds to a novel DNA element (FRE, 5'-repressor element). The DNA binding and repressor activities of Freud-1 are inhibited by calcium-calmodulin-dependent protein kinase. Recently, a deletion in the CC2D1A gene has been linked to nonsyndromic mental retardation. This deletion results in the truncation of the helix-loop-helix DNA binding and the C2 domains, crucial for Freud-1 repressor activity, and hence is predicted to generate an inactive or weakly dominant negative protein. The possible mechanisms by which inactivation of Freud-1 could lead to abnormal cortical development and cognitive impairment and the potential roles of Freud-1 gene targets are discussed.

the widely distribution of CXCL8 and its both receptor expression in several tissues and cell types suggests other functions beyond the regulation of leukocyte migration, e.g. angiogenesis, tumor growth or brain pathology. Several diseases of the eye were accompanied by inflammatory processes and migration and/or proliferation of neuroglia cells. Therefore, we examined the expression of CXCL8 and its receptors in human retinal glial cells. The primary cultured cells from human donor retinas were mainly immunoreactive for glia fibrillary acidic protein (GFAP) vimentin, S-100, S-100␤ and cellular retinaldehyd binding protein (CRALBP) and represent cell cultures of macroglial cells, i.e. astrocytes and Müller glial cells. Immunoreactivity for CXCL8, CXCR1 and CXCR2 could be observed in virtually all cultured glial cells. The expression of CXCL8, CXCR1 and CXCR2 was confirmed in immortilized human Müller cell line (MIO-M1) by immunohistochemistry, RT-PCR analysis and Western blotting. Calcium imaging experiments revealed functional CXCL8 receptors in Müller cells after stimulation with recombinant CXCL8. To our surprise, we could detect CXCR1 and CXCR2 expression in normal retinae of human organ donors by means immunohistochemistry. RT-PCR analysis and Western blotting. This suggests additional function of CXCL8 receptors in healthy retinal tissues beyond the involvement in pathological processes. Because of several similarities of cultured glial cells and gliotic glial cells of the retina and the expression of CXCL8 and both of its functional receptors, Müller glial cellsand asrocytes may participate in the inflammatory response of the retina in diseases of the eye.The human 5-HT1A receptor gene is negatively-regulated by several repressors including DEAF-1 and Hes5, which recognize the C-allele of a novel 26-bp palindrome element proximal to the C(-1019)G polymorphism that has been associated with major depression and related mental illnesses. We hypothesized that other Hes family protein might regulate 5-HT1A transcription through an N-box element located within the 26-bp palindrome. Hes proteins are regulators of neurogenesis that include Hes1 and Hes5, which are abundant in developing neurons and prevent neurogenesis, and Hes6, which promotes neurogenesis and persists into adulthood. The activity of human Hes1, -5, -6 was tested at the human 5-HT1A 26-bp palindrome in 5-HT1A negative L6 and 5-HT1A positive SN-48 (post-synaptic model) and RN46A raphe cells (pre-synaptic model). Like Hes5, Hes1 repressed transcription of the reporter construct, demonstrating more potent repression than Hes5 in the 5-HT1A-containing SN48 and RN46A cells. In 5-HT1A negative L6 cells, Hes6 alone had no effect on basal transcription, but antagonized both Hes1-and Hes5-induced repression. In 5-HT1A containing SN48 or RN46A cells, Hes6 alone enhanced basal transcription, likely due to antagonism of endogenous Hes1 and -5. Repressor activity of Hes1 and Hes5 was blocked upon mutation of the N-box, but unlike Hes5, Hes1 displayed signific...