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  • 1
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: ICER (inducible cyclic AMP early repressor), a member of the cyclic AMP response element (CRE) modulator (CREM) family of transcription factors, is a powerful repressor of cyclic AMP-mediated transactivation. Our studies characterize the regulation of ICER in C6 glioma cells and investigate its role in repressing transcription of the β1-adrenergic receptor (β1AR) gene. Incubation with isoproterenol (100 nM) results in a rapid induction in levels of mRNA for ICER and its splice variant ICERγ, with maximal induction occurring after 2 h of treatment. Incubation with isoproterenol also increased levels of CREM isoforms within 1 h; this was unexpected given previous reports that these isoforms are not rapidly induced. Increased expression of ICER and CREM was accompanied by induction of two CRE-binding complexes. The presence of ICER in these two CRE-binding complexes is demonstrated by their disruption with CREM antibody and by their comigration with recombinant ICER. Because the time course for isoproterenol induction of ICER mRNA and CRE binding corresponds to that for down-regulation of β1AR mRNA levels in C6 glioma cells, the influence of ICER on β1AR transcription was directly examined. Coexpression of ICER significantly decreased transcriptional activity of a rat β1AR promoter-luciferase reporter construct that contains a CRE. In contrast, coexpression of ICER did not influence two truncated rat β1AR promoter constructs that lack the CRE site. These data demonstrate that ICER can interact at the β1AR promoter to repress transcription.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: Rapid expression of ICER (inducible cyclic AMP early repressor), an inducible member of the CREM (cyclic AMP response element modulator) family of transcription factors, has been reported in neuroendocrine tissues and cell lines, but not in brain. In the present study, we demonstrate that acute electroconvulsive seizure (ECS) increases the expression of ICER in several rat brain regions. RNase protection analysis demonstrated that 1–2 h after administration of ECS, levels of mRNA for ICER and a splice variant, ICERγ, were significantly increased in hippocampus, frontal cortex, and cerebellum. It is surprising that ECS also increased levels of mRNA for several CREM isoforms that previous studies have reported were not rapidly inducible. In situ hybridization analysis confirmed these findings and demonstrated that ECS induction of ICER was most obvious in the dentate gyrus granule cell layer of hippocampus and deep layers of cerebral cortex. Induction of ICER and CREM was accompanied by increased expression of two small CRE-binding complexes. Gel supershift analysis with CREM/ICER antisera confirmed that the inducible CRE-binding complexes contain CREM/ICER. Induction of CREM and ICER may contribute to negative feedback regulation of gene transcription that is increased by acute seizure and activation of CREB (cyclic AMP response element-binding protein).
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 68 (1997), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: A receptor-type protein tyrosine phosphatase, PTP NE-6, was identified from rat olfactory epithelial cDNA and cloned from a rat brain cDNA library. PTP NE-6 mRNA is abundant in brain and expressed at lower levels in olfactory tissue and adrenal gland. In situ hybridization demonstrates that PTP NE-6 mRNA is expressed throughout the brain, with highest levels in the medial habenula and at intermediate levels in layer IV of cortex, medial geniculate nucleus, inferior colliculus, hypothalamus, and thalamus. The predicted amino acid sequence demonstrates that PTP NE-6 contains a single catalytic domain that diverges from the consensus protein tyrosine phosphatase catalytic domain by expressing an aspartate instead of the conserved alanine residue in the catalytic site. Recombinantly expressed PTP NE-6 does not exhibit detectable phosphatase activity. Upon mutation of the aspartate to the consensus alanine, phosphatase activity toward p-nitrophenyl phosphate is observable with a kcat value of 3.7 s−1 and a Km of 980 µM. These data demonstrate that the inactivity of native PTP NE-6 toward p-nitrophenyl phosphate is due to the divergent aspartate in the catalytic site and not to variant amino acids within the phosphatase domain.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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