Center for Cardiovascular Research, Charité Medical School, Berlin, Germany; Applied Cachexia Research, Department of Cardiology, Charité Medical School, Berlin, Germany.
Int J Cardiol. 2013 Sep 30;168(2):1447-52. doi: 10.1016/j.ijcard.2012.12.094. Epub 2013 Jan 27.
The transcription factor TWIST1 has been described to regulate the microRNA (miR)-199/214 cluster. Genetic disruption of TWIST1 resulted in a cachectic phenotype and early death of the knock-out mice. This might be connected to the activity of the ubiquitin-proteasome-system (UPS), as miR-199a has been suggested to regulate the ubiquitin E2 ligases Ube2i and Ube2g1.
Cardiac tissue from explanted hearts of 42 patients with dilated cardiomyopathy and 20 healthy donor hearts were analysed for protein expression of TWIST1 and its inhibitors Id-1, MuRF-1 and MAFbx, the expression of miR-199a, -199b and -214, as well as the activity of the UPS by using specific fluorogenic substrates.
TWIST1 was repressed in patients with dilated cardiomyopathy by 43% (p=0.003), while Id1 expression was unchanged. This was paralleled by a reduced expression of miR-199a by 38 ± 9% (p=0.053), miR-199b by 36 ± 13% (p=0.019) and miR-214 by 41 ± 11% (p=0.0158) compared to donor hearts. An increased peptidylglutamyl-peptide-hydrolysing activity (p<0.0001) was observed in the UPS, while the chymotrypsin-like and trypsin-like activities were unchanged. The protein levels of the rate limiting ubiquitin E3-ligases MuRF-1 and MAFbx were up-regulated (p=0.005 and p=0.0156, respectively). Mechanistically silencing of TWIST1 using siRNA in primary rat cardiomyocytes led to a down-regulation of the miR-199/214 cluster and to a subsequent up-regulation of Ube2i.
The TWIST1/miR-199/214 axis is down-regulated in dilated cardiomyopathy, which is likely to play a role in the increased activity of the UPS. This may contribute to the loss of cardiac mass during dilatation of the heart.
转录因子 TWIST1 已被描述为调节 microRNA（miR）-199/214 簇。TWIST1 的基因缺失导致敲除小鼠出现恶病质表型和早期死亡。这可能与泛素-蛋白酶体系统（UPS）的活性有关，因为 miR-199a 已被提议调节泛素 E2 连接酶 Ube2i 和 Ube2g1。
从扩张型心肌病患者的 42 例心脏移植心脏和 20 例健康供体心脏中分析 TWIST1 及其抑制剂 Id-1、MuRF-1 和 MAFbx 的蛋白表达，miR-199a、-199b 和 -214 的表达，以及使用特定荧光底物的 UPS 活性。
TWIST1 在扩张型心肌病患者中被抑制了 43%（p=0.003），而 Id1 表达不变。这与 miR-199a 的表达减少 38±9%（p=0.053）、miR-199b 的表达减少 36±13%（p=0.019）和 miR-214 的表达减少 41±11%（p=0.0158）相对照。与供体心脏相比，UPS 的肽酰基谷氨酰肽水解活性增加（p<0.0001），而糜蛋白酶样和胰蛋白酶样活性不变。限速泛素 E3 连接酶 MuRF-1 和 MAFbx 的蛋白水平上调（p=0.005 和 p=0.0156）。在原代大鼠心肌细胞中使用 siRNA 沉默 TWIST1 导致 miR-199/214 簇下调，并随后导致 Ube2i 上调。
TWIST1/miR-199/214 轴在扩张型心肌病中下调，这可能在 UPS 活性增加中起作用。这可能导致心脏扩张过程中心脏质量的丧失。
