Functional mapping of the promoter region of the GNB2L1 human gene coding for RACK1 scaffold protein.

RACK1 (Receptor for Activated C Kinase 1) is a scaffold protein for different kinases and membrane receptors. Previously, we characterized an age-dependent decline of RACK1 protein expression which could be counteracted with DHEA (dehydroepiandrosterone) [Corsini, E., et al. 2002. In vivo dehydroepiandrosterone restores age-associated defects in the protein kinase C signal transduction pathway and related functional responses. J. Immunol. 168, 1753-1758. and Corsini, E., et al. 2005. Age-related decline in RACK-1 expression in human leukocytes is correlated to plasma levels of dehydroepiandrosterone. J. Leukoc. Biol. 77, 247-256.]. Hypothesizing a direct control of RACK1 expression by DHEA we studied the not yet characterized human promoter region of its coding gene GNB2L1. The FLOE (Fluorescently Labeled Oligonucleotide Extension) was used to map the transcription start site and a novel Gateway luciferase vector (GW luc basic; Del Vecchio, I., Zuccotti, A., Canneva, F., Lenzken, S.C., Racchi, M., 2007. Development of the first Gateway firefly luciferase vector and use of reverse transcriptase in FLOE (Fluorescently Labeled Oligonucleotide Extension) reactions. Plasmid 58, 269-274.) to obtain promoter region mutants. Human SH-SY5Y, THP1 and lymphoblastoid cells were used for transient transfections and treatments with lipopolysaccharide (LPS), phorbol myristate acetate (PMA), DHEA and cortisol (the first two molecules to differently activate NF-kB, a transcription complex able to regulate the murine Gnb2l1 gene expression, whereas DHEA and cortisol since they are known to be imbalanced during the aging and possess counteracting actions on the immune function). The primer extension demonstrated the existence of two alternative start sites of transcription respectively located at about 230 and 300 nt 5' of the Genbank mRNA entry for GNB2L1. Moreover, as a result of the luciferase study we were able to demonstrate that a little region of approximately 300 nt conserved sufficient elements for reporter expression. We also reported that the DHEA modulation of GNB2L1 endogenous expression could not be recapitulated with the luciferase assays. Indeed, the promoter was significantly modulated by means of LPS and PMA treatments but not using DHEA. Differently the use of cortisol led us to demonstrate a biologically significant decrease of luciferase activity only in the presence of a binding site for nuclear receptors of glucocorticoids. Interestingly, other binding sites for transcriptional factors were identified in silico: different c-Rel (NF-kB) and some cardiomyocitic specific cis-acting elements. All this data suggest that the DHEA mediated GNB2L1 regulation is modulated by distant elements (enhancers/silencers), whereas LPS, PMA and cortisol effect can act directly on the mapped GNB2L1 promoter. In conclusion we hypothesize that the imbalance between DHEA and cortisol during aging could be important in the previously demonstrated recovery of the RACK1 expression.

Cognition enhancers between treating and doping the mind.

Memory, attention and creativity represent three different cognitive domains, which are interconnected and contribute the "mental performance" of an individual. Modern neuroscience has investigated some of the neuronal circuits and of the neurotransmitters and molecular events underlying the above-mentioned cognitive functions. Within this renewed reference context, some of the properties of the components of the remedies to increase mental performance have been studied and validated in experimental models and, to date, these substances are named "smart drugs", "memory enhancing drugs" or "nootropic drugs" (from the Greek root noos for mind and tropein for toward). Recently pharmaceutical industries are increasingly focusing on the research for potential substances in this field: several "smart drugs" are in clinical trials and could be on the market in few years. Furthermore, a quick survey from Internet highlights the presence of a great variety of both approved and non-approved drugs, with some of them addressing to only medical and others to performance-oriented use, opening room to some reflections or speculations from scientific and ethical points of view. In order to point out the effect of nootropic drugs on cognition of healthy people, we reviewed the literature on drug enhancement of various cognitive functions, including memory, attention and creativity. As their simplest, memory is regarded as the ability to remember events or learned material, attention is the cognitive process of selectively concentrating on one aspect while ignoring distracters and creativity could be described as the ability to create products or ideas which are original and which possess a social usefulness. Reports from literature reveal that some medications currently available to patients with memory disorders may also increase performances in healthy people and that drugs designed for psychiatric disorders can also be used to enhance certain mental functions. However, the long-term effects of these drugs are unknown, but their apparent effectiveness allows room to their use and misuse. At variance with these literature data showing scientific, even if poor, evidence of the effect of smart drugs in the field of memory and attention, only indirect information on creativity can be obtained by studies of the effects of diseases and drugs on the artistic productivity of classic painters and famous authors, offering a link to understand the neuronal basis of this cognitive function and a cue to understand how drugs (used to correct the illness) may affect the function. On the basis of these cues, in this review we will discuss some critical aspects of the different cerebral circuits and molecular events regulating memory, attention and creativity in order to outline the neurobiological bases of the effects of "smart drugs" on cognitive functions, and to evaluate their putative pharmaceutical development.

Development of the first Gateway firefly luciferase vector and use of reverse transcriptase in FLOE (Fluorescently Labeled Oligonucleotide Extension) reactions.

To study promoters we usually use primer extension to map the transcription start site and a panel of PCR generated deletion mutants. This strategy is complex and time-consuming. Therefore, we decided to improve it by using Gateway and FLOE (Fluorescently Labeled Oligonucleotide Extension). In this report we developed the first luciferase reporter "destination vector" (GW luc basic) for the Gateway technology and tested its efficacy, accuracy and background level by transfecting two distant cell lines (THP1 monocytic and SH-SY5Y neural cells). This vector is a real advantage for the cloning of many PCR fragments and sustains reporter activity also in THP1 cells, which are known to be problematic for transfection/expression. FLOE is a straightforward method to map transcription start sites but a bias in the capillary electrophoretic migration pattern of ROX weight markers has been reported: ROX markers migrated as if they were some bp longer. We hypothesized that this could depend on the use of different enzymes for the two principal reactions (DNA polymerase for the dideoxy chain terminated reaction on DNA and reverse transcriptase for the primer extension on RNA). Therefore, we used the same reverse transcriptase enzyme on both reactions, demonstrating that the reported bias is not due to the use of different enzymes but is an intrinsic feature of the ROX markers. The proposed procedure is important not only because of the timeliness but also for the global impact on the study of the first layer of the gene regulation.

Nuclear mRNA retention and aberrant doppel protein expression in human astrocytic tumor cells.

Doppel (Dpl) is a paralogue of the mammalian Prion (PrP) protein. It is abundant in testis and, unlike PrP, it is expressed at low levels in the adult central nervous system (CNS). Besides, Dpl overexpression correlates with some prion-disease pathological features, such as ataxia and death of cerebellar neurons. Recently, ectopic expression of doppel was found in two different tumor types, specifically in glial and haematological cancers. In this study the doppel gene (PRND) mRNA and protein expression in PRT-HU2 and IPDDC-A2 astrocytoma-derived cell lines was investigated. Northern blot analysis revealed two equally abundant PRND mRNA isoforms, while real-time PCR, on nuclear and cytoplasmic RNA fractions, and cRNA in situ hybridization, on astrocytoma cells and bioptical specimens, showed a nuclear retention of PRND transcripts. Western blot analysis showed that the amount of protein expressed is low compared to the level of mRNA. Moreover deglycosylation studies indicated that Dpl undergoes unusual glycosylation processes. Immunohistochemistry experiments demonstrated that Dpl was mainly localised in the cytoplasm of the astrocytic tumor cells, and that it failed to be GPI-anchored to the cell membrane. This unusual cellular localization was also confirmed through EGFP-Dpl expression in astrocytomas; on the contrary, HeLa cells exhibited the expected Dpl membrane localization. Our findings suggest an aberrant doppel gene expression pattern, characterized by a substantial nuclear retention of the transcript, an altered post-translational modification of the protein and an unusual cytoplasmic localization.

The prion-like protein Doppel (Dpl) interacts with the human receptor for activated C-kinase 1 (RACK1) protein.

BACKGROUND: Doppel (Dpl) is a homologue of the prion protein (PrPC). In contrast to PrP(C), Dpl is dispensable for prion disease, but appears to have an essential function in male spermatogenesis. Recently, Dpl has been found to be aberrantly expressed in astrocytic and leukaemic tumor specimens, showing a peculiar cytosolic cellular localization. The aim of this study was to clarify some of the putative Dpl interacting proteins. MATERIALS AND METHODS: A yeast two hybrid system was employed and the results were verified by co-immunoprecipitation using transfected cells. RESULTS: Several potential Dpl-binding candidates were identified and, among them, the receptor for activated C-kinase (RACK1) protein was further investigated. RACK1 deletion mutants showed that some of its WD containing domains were directly involved in the binding with Dpl. Our data showed that Dpl interacts with RACK1 by means of its structured globular carboxyl-terminal region. CONCLUSION: This new Dpl interacting partner might suggest functional hypotheses about the role of this protein in an astrocytoma context where Dpl was found ectopically expressed.

Prion-like Doppel gene (PRND) in the goat: genomic structure, cDNA, and polymorphisms.

The genomic structure of the caprine Doppel gene (PRND) was determined using the ovine sequence as a scaffold to generate PCR fragments that were aligned with a cDNA sequence obtained from testicular mRNA. The caprine gene contains two exons, 89 and >2291 bp long, separated by a 1689-bp intron. Two mRNA isoforms of 3.2 and 4.8 kb were identified in the testis, as well as the exact transcription start site by fluorescently labeled oligonucleotide extension (FLOE). Like in sheep and cattle, the open reading frame (ORF) (537 bp) lies within exon 2 and is very much conserved in sheep (99.3%) and cattle (97%). The intronic sequence is also highly conserved (95.3%) compared with sheep, with the only exception of a 47-bp insertion. The PRND ORF was sequenced in 47 healthy and 17 TSE-affected goats of the Italian Ionica breed. Seven nucleotide positions showed variation: T28C, C65T, A151G, G286A, C385G, T451C, and T528C. Five were commonly represented polymorphisms: T28C, T451C, and T528C are silent mutations at codons L10, L151, and I176, respectively, while A151G and C385G determine a T51A and L129V amino acid change, respectively. The two remaining variants, C65T and G286A, were rare, leading to the amino acid substitutions S22F and E96K, respectively. None of the polymorphisms was significantly relatable to the TSE status, and the same result was obtained by the analysis of the combined haplotypes at the five major polymorphic sites, namely, T28C, C65T, A151G, G286A, and C385G.

Absence of interaction between doppel and GFAP, Grb2, PrPc proteins in human tumor astrocytic cells.

BACKGROUND: The doppel protein (Dpl) is a newly recognized cellular prion protein (PrP(C))-like molecule encoded by a novel gene locus, PRND, located on the same chromosomal region of the PrP(C) coding gene. Recently, Dpl was shown to be aberrantly expressed in astrocytic tumor specimens and in astrocytoma-derived cell lines, showing a peculiar cytoplasmic localization. Here, Dpl interactions with some of the prion-interacting proteins were studied. In particular, whether the tumor astrocytic environment is suitable for doppel interaction with GFAP and Grb2 proteins, as well as with the PrPC protein itself was investigated. MATERIALS AND METHODS: In order to verify our hypothesis, an innovative mammalian two-hybrid system and co-immunoprecipitation assays were employed. RESULTS: The results reported the absence of protein interactions. Our findings provided evidence that, in our astrocytoma cell-based model, Dpl does not share with PrP(C) the ability to interact with GFAP and Grb2. CONCLUSION: Identifying Dpl ligands may provide new insights into the involvement of Dpl in astrocytoma tumor progression.

Functional mapping of the bovine Doppel gene promoter region.

The PRND gene encodes Doppel (Dpl), a protein that is strongly expressed in testis and at much lower levels in other tissues. Despite the recent discovery of Dpl involvement in spermiogenesis and in apoptotic death of cerebellar neurons, respectively in wild type and transgenic mice, the physiological role of this prion-like protein remains unknown. To better understand which factors may contribute to the modulation of PRND activity, a study of the bovine promoter region was performed. First, the transcription start site of PRND mRNA was identified using an innovative fluorescently labelled oligonucleotide extension (FLOE) method. The initiation site mapped 129 nt upstream of the protein coding sequence and represents a refinement of a previous assignment based on RACE. Second, deletion mutants of the 4530 nt encompassing 2704 nt 5' of the bovine PRND, exon 1, intron 1, and the first 6 nt of exon 2, have been investigated with CAT-reporter assays in order to identify critical elements for the activation of the gene. The results showed that the region -323/+32 (+1 is the transcription start site mapped by FLOE) represents the promoter region and contains positive cis-acting elements (CCAAT and E box) confirming previous reports with the mouse gene. Additional regulatory elements, including binding sites for repressor molecules, have been identified upstream of that region and in the first portion of intron 1, suggesting a complex tissue-specific regulation of Doppel gene expression.

Differential expression of the prion-like protein doppel gene (PRND) in astrocytomas: a new molecular marker potentially involved in tumor progression.

The expression of the prion (PRNP) and prion like-doppel (PRND) genes and the presence of the proteins prion (PrP) and doppel (Dpl) were investigated in human gliomas. The PRNP and PRND expression profiles were evaluated by real-time reverse transcription-quantitative PCR in low- and high-grade astrocytomas, in glioblastoma-derived cell lines and in non-glial tumor specimens. The presence of PrP and Dpl proteins and their cellular localization were evaluated by Western blot and immunohistochemistry. High levels of PRNP expression were found in all tumoral samples studied. Unlike the non-tumoral controls, PRND was aberrantly expressed in glioblastoma multiforme and in two glioblastoma multiforme-derived cell lines, even in the absence of the PRND gene amplification. PRND expression was directly related to malignancy of the tumor: highest in glioblastoma multiforme, lower in anaplastic astrocytoma and even lower in the low-grade astrocytoma samples. High levels of PRND were also found in non-glial malignant tumor samples, such as gastric adenocarcinoma and anaplastic meningioma. Western blot analysis confirmed the PrP and Dpl expression, displaying variability in the electrophoretic patterns. Immunohistochemical analysis revealed a diffuse cytoplasmatic Dpl distribution in different astrocytic neoplastic cells, in infiltrating lymphocytes and in blood vessel endothelial cells. Of note, Dpl reactivity was different from that of the PrP, since PrP showed typical Golgi and membrane localised staining. Our findings suggest that the PRND gene might be a useful molecular marker in astrocytoma progression and in tumor grade definition. Understanding of the mechanisms of PRND increased expression might provide insight into the regulatory pathways of glioma development.