Experimental Unit, Hospital Donostia, San Sebastián, Spain.
Mol Cell Biochem. 2010 Apr;337(1-2):167-73. doi: 10.1007/s11010-009-0296-x. Epub 2009 Oct 24.
Phospholipase C-beta (PLCbeta) isozymes (PLCbeta(1) and PLCbeta(3)) have been extensively characterized in cardiac tissue, but no data are available for the PLCbeta(4) isozyme. In this study, PLCbeta((1-4)) isozymes mRNA relative expression was studied by real-time PCR (RT-PCR) in human, rat, and murine left ventricle and the presence of PLCbeta(4) isozyme at the protein level was confirmed by Western blotting in all species studied. Confocal microscopy experiments carried out in HL-1 cardiomyocytes revealed a sarcoplasmic subcellular distribution of PLCbeta(4). Although there were unexpected significant interspecies differences in the PLCbeta((1-4)) mRNA expression, PLCbeta(4) mRNA was the main transcript expressed in all left ventricles studied. Thus, whereas in human and rat left ventricles PLCbeta(4) > PLCbeta(3) > PLCbeta(2) > PLCbeta(1) mRNA pattern of expression was found, in murine left ventricle the pattern of expression was different, i.e., PLCbeta(4) > PLCbeta(1) > PLCbeta(3) > PLCbeta(2). However, results obtained in mouse HL-1 cardiomyocytes showed PLCbeta(3) approximately PLCbeta(4) > PLCbeta(1) > PLCbeta(2) pattern of mRNA expression indicating a probable cell type specific expression of the different PLCbeta isozymes in cardiomyocytes. Finally, RT-PCR experiments showed a trend, even though not significant (P = 0.067), to increase PLCbeta(4) mRNA levels in HL-1 cardiomyocytes after angiotensin II treatment. These results demonstrate the presence of PLCbeta(4) in the heart and in HL-1 cardiomyocytes showing a different species-dependent pattern of expression of the PLCbeta((1-4)) transcripts. We discuss the relevance of these findings in relation to the development of cardiac hypertrophy.
磷酯酶 C-β（PLCβ）同工酶（PLCβ（1）和 PLCβ（3））在心肌组织中已被广泛研究，但 PLCβ（4）同工酶的数据尚未见报道。本研究采用实时定量 RT-PCR（RT-PCR）检测人、鼠和鼠左心室 PLCβ（1-4）同工酶的相对mRNA 表达，并用 Western blot 法证实所有研究物种均存在 PLCβ（4）同工酶。在 HL-1 心肌细胞中进行的共聚焦显微镜实验显示 PLCβ（4）存在于肌浆网亚细胞结构中。尽管 PLCβ（1-4）mRNA 的表达在不同物种之间存在显著的差异，但在所有研究的左心室中，PLCβ（4）mRNA 是主要的转录本。因此，在人及大鼠左心室中发现的 PLCβ（4）mRNA 表达模式为 PLCβ（4）＞PLCβ（3）＞PLCβ（2）＞PLCβ（1），而在鼠左心室中表达模式不同，即 PLCβ（4）＞PLCβ（1）＞PLCβ（3）＞PLCβ（2）。然而，在鼠 HL-1 心肌细胞中获得的结果显示 PLCβ（3）≈PLCβ（4）＞PLCβ（1）＞PLCβ（2）的 mRNA 表达模式，提示不同 PLCβ 同工酶在心肌细胞中可能存在细胞类型特异性表达。最后，RT-PCR 实验显示，尽管无统计学意义（P=0.067），血管紧张素 II 处理后 HL-1 心肌细胞中 PLCβ（4）mRNA 水平有升高的趋势。这些结果表明心脏和 HL-1 心肌细胞中存在 PLCβ（4），并且 PLCβ（1-4）转录本的表达模式存在物种依赖性。我们讨论了这些发现与心肌肥厚发展之间的相关性。
