Pikkarainen Sampsa, Tokola Heikki, Majalahti-Palviainen Theresa, Kerkela Risto, Hautala Nina, Bhalla Suparna S, Charron Férdéric, Nemer Mona, Vuolteenaho Olli, Ruskoaho Heikki
Department of Pharmacology, Biocenter Oulu, University of Oulu, PO Box 5000, FIN-90014 University of Oulu, Finland.
J Biol Chem. 2003 Jun 27;278(26):23807-16. doi: 10.1074/jbc.M302719200. Epub 2003 Apr 17.
In overloaded heart the cardiomyocytes adapt to increased mechanical and neurohumoral stress by activation of hypertrophic program, resulting in morphological changes of individual cells and specific changes in gene expression. Accumulating evidence suggests an important role for the zinc finger transcription factor GATA-4 in hypertrophic agonist-induced cardiac hypertrophy. However, its role in stretch-induced cardiomyocyte hypertrophy is not known. We employed an in vitro mechanical stretch model of cultured cardiomyocytes and used rat B-type natriuretic peptide promoter as stretch-sensitive reporter gene. Stretch transiently increased GATA-4 DNA binding activity and transcript levels, which was followed by increases in the expression of B-type natriuretic peptide as well as atrial natriuretic peptide and skeletal alpha-actin genes. The stretch inducibility mapped primarily to the proximal 520 bp of the B-type natriuretic peptide promoter. Mutational studies showed that the tandem GATA consensus sites of the proximal promoter in combination with an Nkx-2.5 binding element are critical for stretch-activated B-type natriuretic peptide transcription. Inhibition of GATA-4 protein production by adenovirus-mediated transfer of GATA-4 antisense cDNA blocked stretch-induced increases in B-type natriuretic peptide transcript levels and the sarcomere reorganization. The proportion of myocytes with assembled sarcomeres in control adenovirus-infected cultures increased from 14 to 59% in response to stretch, whereas the values for GATA-4 antisense-treated cells were 6 and 13%, respectively. These results show that activation of GATA-4, in cooperation with a factor binding on Nkx-2.5 binding element, is essential for mechanical stretch-induced cardiomyocyte hypertrophy.
在超负荷心脏中，心肌细胞通过激活肥大程序来适应增加的机械和神经体液应激，导致单个细胞的形态变化和基因表达的特定改变。越来越多的证据表明锌指转录因子GATA-4在肥大激动剂诱导的心脏肥大中起重要作用。然而，其在牵张诱导的心肌细胞肥大中的作用尚不清楚。我们采用培养心肌细胞的体外机械牵张模型，并使用大鼠B型利钠肽启动子作为牵张敏感报告基因。牵张短暂增加了GATA-4的DNA结合活性和转录水平，随后B型利钠肽以及心房利钠肽和骨骼肌α-肌动蛋白基因的表达增加。牵张诱导性主要定位于B型利钠肽启动子的近端520 bp。突变研究表明，近端启动子的串联GATA共有位点与Nkx-2.5结合元件结合对于牵张激活的B型利钠肽转录至关重要。通过腺病毒介导的GATA-4反义cDNA转移抑制GATA-4蛋白产生，阻断了牵张诱导的B型利钠肽转录水平增加和肌节重组。在对照腺病毒感染的培养物中，具有组装肌节的心肌细胞比例在牵张刺激下从14%增加到59%，而GATA-4反义处理细胞的值分别为6%和13%。这些结果表明，GATA-4与结合在Nkx-2.5结合元件上的因子协同激活对于机械牵张诱导的心肌细胞肥大至关重要。
