RESUMO
Upon binding of cortisol, the glucocorticoid receptor (GR) regulates the transcription of specific target genes, including those that encode the stress hormones corticotropin-releasing hormone (CRH) and adrenocorticotropic hormone. Dysregulation of the stress axis is a hallmark of major depression in human patients. However, it is still unclear how glucocorticoid signaling is linked to affective disorders. We identified an adult-viable zebrafish mutant in which the negative feedback on the stress response is disrupted, due to abolition of all transcriptional activity of GR. As a consequence, cortisol is elevated, but unable to signal through GR. When placed into an unfamiliar aquarium ('novel tank'), mutant fish become immobile ('freeze'), show reduced exploratory behavior and do not habituate to this stressor upon repeated exposure. Addition of the antidepressant fluoxetine to the holding water and social interactions restore normal behavior, followed by a delayed correction of cortisol levels. Fluoxetine does not affect the overall transcription of CRH, the mineralocorticoid receptor (MR), the serotonin transporter (Serta) or GR itself. Fluoxetine, however, suppresses the stress-induced upregulation of MR and Serta in both wild-type fish and mutants. Our studies show a conserved, protective function of glucocorticoid signaling in the regulation of emotional behavior and reveal novel molecular aspects of how chronic stress impacts vertebrate brain physiology and behavior. Importantly, the zebrafish model opens up the possibility of high-throughput drug screens in search of new classes of antidepressants.
Assuntos
Transtornos do Humor/genética , Mutação/genética , Receptores de Glucocorticoides/genética , Análise de Variância , Animais , Animais Geneticamente Modificados , Ansiolíticos/farmacologia , Ansiolíticos/uso terapêutico , Arginina/genética , Encéfalo/metabolismo , Linhagem Celular Transformada , Chlorocebus aethiops , Hormônio Liberador da Corticotropina/genética , Hormônio Liberador da Corticotropina/metabolismo , Cisteína/genética , Diazepam/farmacologia , Diazepam/uso terapêutico , Modelos Animais de Doenças , Reação de Fuga/efeitos dos fármacos , Reação de Fuga/fisiologia , Comportamento Exploratório/efeitos dos fármacos , Comportamento Exploratório/fisiologia , Fluoxetina/farmacologia , Fluoxetina/uso terapêutico , Reação de Congelamento Cataléptica/fisiologia , Antagonistas de Hormônios/farmacologia , Humanos , Hidrocortisona/sangue , Relações Interpessoais , Mifepristona/farmacologia , Transtornos do Humor/dietoterapia , Transtornos do Humor/metabolismo , Transtornos do Humor/patologia , Agitação Psicomotora/genética , Agitação Psicomotora/patologia , Radioimunoensaio , Receptores de Glucocorticoides/metabolismo , Serotonina/genética , Serotonina/metabolismo , Transfecção , Peixe-ZebraRESUMO
The acetylation state of histones plays a central role in determining gene expression in chromatin. The reestablishment of the acetylation state of nucleosomes after DNA replication and chromatin assembly requires both deacetylation and acetylation of specific lysine residues on newly incorporated histones. In this study, the MYST family acetyltransferase Sas2 was found to interact with Cac1, the largest subunit of Saccharomyces cerevisiae chromatin assembly factor-I (CAF-I), and with the nucleosome assembly factor Asf1. The deletions of CAC1 (cac1Delta), ASF1 (asf1Delta), and SAS2 (sas2Delta) had similar effects on gene silencing and were partially overlapping. Furthermore, Sas2 was found in a nuclear protein complex that included Sas4 and Sas5, a homolog of TAF(II)30. This complex, termed SAS-I, was also found to contribute to rDNA silencing. Furthermore, the observation that a mutation of H4 lysine 16 to arginine displayed the identical silencing phenotypes as sas2Delta suggested that it was the in vivo target of Sas2 acetylation. In summary, our data present a novel model for the reestablishment of acetylation patterns after DNA replication, by which SAS-I is recruited to freshly replicated DNA by its association with chromatin assembly complexes to acetylate lysine 16 of H4.
Assuntos
Acetiltransferases/metabolismo , Proteínas de Ciclo Celular/metabolismo , Cromatina/metabolismo , Proteínas Cromossômicas não Histona , Proteínas de Ligação a DNA/metabolismo , Inativação Gênica , Histonas/metabolismo , Saccharomyces cerevisiae , Acetilcoenzima A/metabolismo , Acetilação , Acetiltransferases/química , Acetiltransferases/genética , Sítios de Ligação , Western Blotting , Proteínas de Ciclo Celular/genética , Cromatina/química , Fator 1 de Modelagem da Cromatina , DNA Fúngico/genética , DNA Fúngico/metabolismo , DNA Ribossômico/genética , DNA Ribossômico/metabolismo , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/genética , Deleção de Genes , Regulação Fúngica da Expressão Gênica , Histona Acetiltransferases , Histonas/química , Histonas/genética , Substâncias Macromoleculares , Chaperonas Moleculares , Mutação/genética , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Fenótipo , Ligação Proteica , Subunidades Proteicas , Saccharomyces cerevisiae/enzimologia , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/química , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Técnicas do Sistema de Duplo-Híbrido , Dedos de ZincoRESUMO
Cancer cachexia is a complex syndrome which occurs in more than two-thirds of patients who die with advanced cancer. The main components of this pathological state are anorexia and metabolic abnormalities such as glucose intolerance, fat depletion, and muscle protein catabolism among others. The aim of the present study is to review the different therapeutic approaches that have been designed to fight and counteract cancer cachexia.
