Barac Yaron D, Zeevi-Levin Naama, Yaniv Gal, Reiter Irina, Milman Felix, Shilkrut Mark, Coleman Raymond, Abassi Zaid, Binah Ofer
Rappaport Institute, Rappaport Faculty of Medicine, Technion, Haifa, Israel.
Cardiovasc Res. 2005 Oct 1;68(1):75-86. doi: 10.1016/j.cardiores.2005.05.015.
Cardiac hypertrophy is a compensatory response to increased mechanical load. Since Fas receptor activation is an important component in hypertrophy induced by pressure- and volume-overload, deciphering the underlying signaling pathways is of prime importance. Based on our previous work showing that in mice and rats ventricular myocytes the electrophysiological disturbances and diastolic [Ca2+]i-rise caused by 3 h of Fas activation are dependent on the Fas-->phospholipase C (PLC)-->1,4,5-inositol trisphosphate (1,4,5-IP3)-->sarcoplasmic reticulum (SR) [Ca2+]i release pathway, we tested the hypothesis that this pathway is also critical for Fas-mediated hypertrophy.
The effects of 24 h Fas activation in cultured neonatal rat ventricular myocytes (NRVM) were analyzed by means of RT-PCR, Western blot, immunofluorescence and fura-2 fluorescence.
Fas activation increased nuclei surface area, atrial natriuretic peptide and connexin43 (Cx43) mRNA, the protein levels of total Cx43 and non-phosphorylated Cx43, and sarcomeric actin, all indicating hypertrophy. Concomitantly, Fas activation decreased mRNA of SERCA2a, the ryanodine receptor (RyR) and nuclear IP3R3. Further, Fas activation caused NFAT nuclear translocation. The hypertrophy was abolished by U73122, xestospongin C (blockers of the 1,4,5-IP3 pathway), genistein and by the PI3K blocker LY294002.
Fas-mediated hypertrophy is dependent on the 1,4,5-IP3 pathway, which is functionally inter-connected to the PI3K/AKT/GSK3beta pathway. Both pathways act in concert to cause NFAT nuclear translocation and subsequent hypertrophy.
心脏肥大是对机械负荷增加的一种代偿性反应。由于Fas受体激活是压力和容量超负荷诱导的肥大的重要组成部分，因此解析其潜在的信号通路至关重要。基于我们之前的研究工作，该研究表明在小鼠和大鼠心室肌细胞中，Fas激活3小时所引起的电生理紊乱和舒张期[Ca2+]i升高依赖于Fas→磷脂酶C（PLC）→1,4,5-三磷酸肌醇（1,4,5-IP3）→肌浆网（SR）[Ca2+]i释放途径，我们检验了这一途径对Fas介导的肥大也至关重要的假说。
通过逆转录聚合酶链反应（RT-PCR）、蛋白质免疫印迹法、免疫荧光法和fura-2荧光法分析培养的新生大鼠心室肌细胞（NRVM）中Fas激活24小时的作用。
Fas激活增加了细胞核表面积、心钠素和连接蛋白43（Cx43）的mRNA、总Cx43和非磷酸化Cx43的蛋白质水平以及肌节肌动蛋白，所有这些均表明发生了肥大。同时，Fas激活降低了肌浆网钙ATP酶2a（SERCA2a）、兰尼碱受体（RyR）和细胞核肌醇三磷酸受体3（IP3R3）的mRNA。此外，Fas激活导致活化T细胞核因子（NFAT）核转位。U73122、西司他汀C（1,4,5-IP3途径的阻滞剂）、染料木黄酮以及磷脂酰肌醇-3激酶（PI3K）阻滞剂LY294002均可消除肥大。
Fas介导的肥大依赖于1,4,5-IP3途径，该途径在功能上与PI3K/蛋白激酶B（AKT）/糖原合成酶激酶3β（GSK3β）途径相互连接。两条途径协同作用导致NFAT核转位及随后的肥大。
