Cullingford Timothy E, Markou Thomais, Fuller Stephen J, Giraldo Alejandro, Pikkarainen Sampsa, Zoumpoulidou Georgia, Alsafi Ali, Ekere Collins, Kemp Timothy J, Dennis Jayne L, Game Laurence, Sugden Peter H, Clerk Angela
National Heart and Lung Institute Division, Faculty of Medicine, Imperial College London, Armstrong Road, London SW7 2AZ, UK.
Genome Biol. 2008;9(2):R32. doi: 10.1186/gb-2008-9-2-r32. Epub 2008 Feb 14.
Endothelin-1 stimulates Gq protein-coupled receptors to promote proliferation in dividing cells or hypertrophy in terminally differentiated cardiomyocytes. In cardiomyocytes, endothelin-1 rapidly (within minutes) stimulates protein kinase signaling, including extracellular-signal regulated kinases 1/2 (ERK1/2; though not ERK5), with phenotypic/physiological changes developing from approximately 12 h. Hypertrophy is associated with changes in mRNA/protein expression, presumably consequent to protein kinase signaling, but the connections between early, transient signaling events and developed hypertrophy are unknown.
Using microarrays, we defined the early transcriptional responses of neonatal rat cardiomyocytes to endothelin-1 over 4 h, differentiating between immediate early gene (IEG) and second phase RNAs with cycloheximide. IEGs exhibited differential temporal and transient regulation, with expression of second phase RNAs within 1 h. Of transcripts upregulated at 30 minutes encoding established proteins, 28 were inhibited >50% by U0126 (which inhibits ERK1/2/5 signaling), with 9 inhibited 25-50%. Expression of only four transcripts was not inhibited. At 1 h, most RNAs (approximately 67%) were equally changed in total and polysomal RNA with approximately 17% of transcripts increased to a greater extent in polysomes. Thus, changes in expression of most protein-coding RNAs should be reflected in protein synthesis. However, approximately 16% of transcripts were essentially excluded from the polysomes, including some protein-coding mRNAs, presumably inefficiently translated.
The phasic, temporal regulation of early transcriptional responses induced by endothelin-1 in cardiomyocytes indicates that, even in terminally differentiated cells, signals are propagated beyond the primary signaling pathways through transcriptional networks leading to phenotypic changes (that is, hypertrophy). Furthermore, ERK1/2 signaling plays a major role in this response.
内皮素 -1刺激Gq蛋白偶联受体，以促进分裂细胞的增殖或终末分化心肌细胞的肥大。在心肌细胞中，内皮素 -1迅速（在数分钟内）刺激蛋白激酶信号传导，包括细胞外信号调节激酶1/2（ERK1/2；但不包括ERK5），表型/生理变化大约在12小时后出现。肥大与mRNA/蛋白质表达的变化有关，推测是蛋白激酶信号传导的结果，但早期短暂信号事件与已发展的肥大之间的联系尚不清楚。
使用微阵列，我们确定了新生大鼠心肌细胞对内皮素 -1在4小时内的早期转录反应，通过放线菌酮区分即时早期基因（IEG）和第二阶段RNA。IEG表现出不同的时间和瞬时调节，第二阶段RNA在1小时内表达。在30分钟时上调的编码已知蛋白的转录本中，28种被U0126（抑制ERK1/2/5信号传导）抑制>50%，9种被抑制25 - 50%。只有四种转录本的表达未被抑制。在1小时时，大多数RNA（约67%）在总RNA和多聚核糖体RNA中的变化相同，约17%的转录本在多聚核糖体中增加程度更大。因此，大多数蛋白质编码RNA表达的变化应反映在蛋白质合成中。然而，约16%的转录本基本上被排除在多聚核糖体之外，包括一些蛋白质编码mRNA，推测其翻译效率低下。
内皮素 -1在心肌细胞中诱导的早期转录反应的阶段性、时间性调节表明，即使在终末分化细胞中，信号也通过转录网络在初级信号通路之外传播，导致表型变化（即肥大）。此外，ERK1/2信号传导在这种反应中起主要作用。
