RESUMO
alpha1-Adrenergic receptors mediate several biological effects of catecholamines, including the regulation of myocyte growth and contractility and transcriptional regulation of the atrial natriuretic factor (ANF) gene whose promoter contains an alpha1-adrenergic response element. The nuclear pathways and effectors that link receptor activation to genetic changes remain poorly understood. Here, we describe the isolation by the yeast one-hybrid system of a cardiac cDNA encoding a novel nuclear zinc finger protein, Zfp260, belonging to the Krüppel family of transcriptional regulators. Zfp260 is highly expressed in the embryonic heart but is downregulated during postnatal development. Functional studies indicate that Zfp260 is a transcriptional activator of ANF and a cofactor for GATA-4, a key cardiac regulator. Knockdown of Zfp260 in cardiac cells decreases endogenous ANF gene expression and abrogates its response to alpha1-adrenergic stimulation. Interestingly, Zfp260 transcripts are induced by alpha1-adrenergic agonists and are elevated in genetic models of hypertension and cardiac hypertrophy. The data identify Zfp260 as a novel transcriptional regulator in normal and pathological heart development and a nuclear effector of alpha1-adrenergic signaling.
Assuntos
Núcleo Celular/metabolismo , Receptores Adrenérgicos alfa 1/metabolismo , Transdução de Sinais , Transativadores/química , Adenoviridae/genética , Sequência de Aminoácidos , Animais , Fator Natriurético Atrial/metabolismo , Sequência de Bases , Western Blotting , Proliferação de Células , Clonagem Molecular , DNA Complementar/metabolismo , Regulação para Baixo , Técnica Indireta de Fluorescência para Anticorpo , Regulação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Biblioteca Gênica , Genes Reporter , Células HeLa , Coração/embriologia , Humanos , Hipertensão/genética , Hipertrofia/genética , Imuno-Histoquímica , Óperon Lac , Dados de Sequência Molecular , Miocárdio/metabolismo , Miócitos Cardíacos/metabolismo , Oligonucleotídeos Antissenso/química , Plasmídeos/metabolismo , Regiões Promotoras Genéticas , Estrutura Terciária de Proteína , RNA/metabolismo , RNA Mensageiro/metabolismo , Ratos , Ratos Endogâmicos WKY , Ratos Sprague-Dawley , Proteínas Recombinantes/química , Homologia de Sequência de Aminoácidos , Fatores de Tempo , Transativadores/biossíntese , Transcrição Gênica , Ativação Transcricional , Dedos de ZincoRESUMO
Adrenomedullin (AM) may function as an autocrine and/or paracrine factor in the heart, but the exact mechanisms regulating cardiac AM gene expression are unknown. The aim of the present study was to characterize the role of mechanical load in regulating gene expression of AM by using two hypertensive rat strains as experimental models. Acute pressure overload was produced by arginine(8)-vasopressin (AVP, 0.05 microg/kg/min, i.v.) infusion in conscious spontaneously hypertensive rats (SHR) and double transgenic rats (dTGR) harboring both the human renin and angiotensinogen genes and in their respective normotensive strains. A significant increase in left ventricular AM mRNA levels was seen in the left ventricles of all rat strains, the increase being augmented in hypertensive strains. Direct left ventricular wall stretch in isolated, perfused rat heart preparation also activated AM gene expression. However, stretching of cultured neonatal ventricular myocytes resulted in inhibition of AM gene expression, and stretch also blocked hypoxia-induced increase in AM gene expression. The present study shows that cardiac AM gene expression is upregulated in response to pressure overload and that this upregulation may be mediated via cell types other than cardiac myocytes.