Cloning and cellular distribution of a group II phospholipase A(2) expressed in the heart

Phospholipase A(2) has been considered to play a role in physiological membrane turnover in cardiac tissue and in the degradation of membrane lipids under pathophysiological conditions, such as ischemia and reperfusion. We report the cloning of a cDNA encoding a member of the Ca2+-dependent, low molecular mass phospholipase A(2) (PLA(2)) present in rat heart. The cDNA predicts a mature protein of 146 amino acid residues including a 21 amino acid sequence at the N-terminal end, which has the features characteristic of eukaryotic secretory signal peptides. The deduced amino acid sequence constitutes an enzyme of the group II class of PLA(2)s, and resembles PLA(2)s from other mammalian sources. A Northern blot analysis performed to determine the tissue distribution showed that rat ileum contains the largest amount of the PLA(2) transcript among the tissues examined, a weaker signal was present in heart, spleen and soleus muscle, and no signal could be detected in EDL muscle, stomach, liver, kidney, brain and lung. Northern blot analysis and reverse transcriptase-polymerase chain reaction (RT-PCR) techniques indicate the presence of this enzyme in neonatal and adult rat cardiomyocytes and in a cultured rat cardiac fibroblast-like cell line, but not in rat cardiac-derived endothelial cell lines. Transcription levels of rat heart group II PLA(2) in isolated neonatal rat cardiomyocytes were found to increase after stimulating the cells with tumor necrosis factor-alpha (TNF-alpha) or the alpha(1)-adrenergic agonist phenylephrine. (C) 1997 Academic Press Limited.