三磷酸肌醇受体参与心肌钙调神经磷酸酶信号通路的激活

Inositol 1,4,5-trisphosphate receptor involved in the activation of calcineurin signaling pathway in myocardium

目的:研究激活心肌细胞三磷酸肌醇受体(IP3R)是否触发钙调神经磷酸酶(CaN)介导的心肌肥厚信号通路。方法:培养的乳鼠心肌细胞检测心肌细胞蛋白合成,细胞内钙变化,CaN、活化T细胞核因子3(NFAT3)及锌指转录因子(GATA4),胚胎基因(αskeletalactin,βMHC)及即刻早期基因(cfos,cmyc)蛋白表达。结果:三磷酸肌醇(IP3)能显著致原代培养的心肌细胞时间和剂量依赖性地增加心肌细胞蛋白合成,能显著致心肌细胞的早期即刻基因和胚胎基因表达,能显著增加心肌细胞内游离钙。IP3剌激IP3受体,能显著激活心肌细胞CaN/NFAT3/GATA4信号通路,使心肌细胞早期即刻基因(cfos、cmyc)及胚胎基因(αskeletalactin,βMHC)表达增加。结论:激活IP3R介导的CaN/NFAT3/GATA4信号通路能显著地促使心肌细胞肥大,这条信号通路不同于已知的G蛋白偶联受体介导的心肌肥厚信号转导途径。

AIM:To investigate whether the activation of InsP_3R mediated calcineruin( CaN)/nuclear factor of activated T-lymphocyte-3(NFAT_3)/GATA_4 (Zinic finger transcription factor ) pathway plays a potential role in regulation of cardiomyocyte hypertrophy and whetherheparin may antagonize this signaling pathway. METHODS:Primary neonatal rat cardiomyocytes were measured using rationmetric Fura-2 fluorescence. Protein synthesis of cardiomyocytes was performed by ~3H-Leucine incorporation. Western blotting was used to evaluate the semi-quantification of CaN, NFAT_3, GATA_4, α-skeletal actin, c-fos, c-myc protein expressions of CaN, NFAT_3 . RT-PCR was used to analyze the mRNA expression of β-myosin heavy chain. RESULTS: Inositol 1,4,5-trisphosphate (lnsP_3) (1 nmol/L~ 1 μmol/L) caused a dose-dependent increase in cytostolic free calcium concentration of cardiomyocytes. InsP_3 also promoted the protein synthesis(~3H-Leu incorporation) of cardiomyocytes in a time and dose-dependent manner. c-fos, c-myc, α-skeletal-actin protein and β-MHC mRNA expressions of cardiomyocytes were significantly enhanced by administration of InsP_3. Stimulation of cardiomyocytes was also significantly enhanced by administration of InsP_3. Stimulation of cardiomyocytes with InsP_3 revealed a time - dependent increase in the expressions of CaN, NFAT_3, and GATA_4. CONCLUSION: Alteration of InsP_3 sensitive calcium pool can be coupled to activation of the cardiac hypertrophic gene regulatory pathways.Antagonizing InsP_3R/ CaN/ NFAT_3 signaling pathway may be a valuable therapeutic target for cardiac hypertrophy.