Phospholipase Cβ4 isozyme is expressed in human, rat, and murine heart left ventricles and in HL-1 cardiomyocytes

Phospholipase C-β (PLCβ) isozymes (PLCβ1 and PLCβ3) have been extensively characterized in cardiac tissue, but no data are available for the PLCβ4 isozyme. In this study, PLCβ(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 PLCβ4 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 PLCβ4. Although there were unexpected significant interspecies differences in the PLCβ(1–4) mRNA expression, PLCβ4 mRNA was the main transcript expressed in all left ventricles studied. Thus, whereas in human and rat left ventricles PLCβ4 > PLCβ3 > PLCβ2 > PLCβ1 mRNA pattern of expression was found, in murine left ventricle the pattern of expression was different, i.e., PLCβ4 > PLCβ1 > PLCβ3 > PLCβ2. However, results obtained in mouse HL-1 cardiomyocytes showed PLCβ3 ≈ PLCβ4 > PLCβ1 > PLCβ2 pattern of mRNA expression indicating a probable cell type specific expression of the different PLCβ isozymes in cardiomyocytes. Finally, RT-PCR experiments showed a trend, even though not significant (P = 0.067), to increase PLCβ4 mRNA levels in HL-1 cardiomyocytes after angiotensin II treatment. These results demonstrate the presence of PLCβ4 in the heart and in HL-1 cardiomyocytes showing a different species-dependent pattern of expression of the PLCβ(1–4) transcripts. We discuss the relevance of these findings in relation to the development of cardiac hypertrophy.