Calcium-independent phospholipase A2 in rabbit ventricular myocytes.
We have previously reported that the majority of phospholipase A2 (PLA2) activity in rabbit ventricular myocytes is membrane-associated, calcium-independent (iPLA2), selective for arachidonylated plasmalogen phospholipids and inhibited by the iPLA2-selective inhibitor bromoenol lactone (BEL). Here, we identified the presence of iPLA2 in rabbit ventricular myocytes, determined the full length sequences for rabbit iPLA2beta and iPLA2gamma and compared their homology to the human isoforms. Rabbit iPLA2beta encoded a protein with a predicated molecular mass of 74 kDa that is 91% identical to the human iPLA2beta short isoform. Full length iPLA2gamma protein has a predicated molecular mass of 88 kDa and is 88% identical to the human isoform. Immunoblot analysis of iPLA2beta and gamma in membrane and cytosolic fractions from rabbit and human cardiac myocytes demonstrated a similar pattern of distribution with both isoforms present in the membrane fraction, but no detectable protein in the cytosol. Membrane-associated iPLA2 activity was inhibited preferentially by the R enantiomer of bromoenol lactone [(R)-BEL], indicating that the majority of activity is due to iPLA2gamma.
Beckett
Caroline S
CS
Department of Pathology, Saint Louis University School of Medicine, 1402 S. Grand Blvd., St. Louis, MO 63104, USA.
McHowat
Jane
J
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry; D005260:Female; D006352:Heart Ventricles / Q000201:enzymology; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D032383:Myocytes, Cardiac / Q000201:enzymology*; D009281:Naphthalenes / Q000494:pharmacology; D054512:Phospholipases A2, Calcium-Independent / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D011753:Pyrones / Q000494:pharmacology; D011817:Rabbits
D018076:DNA, Complementary; D007527:Isoenzymes; D009281:Naphthalenes; D011753:Pyrones; C068314:6-(bromomethylene)tetrahydro-3-(1-naphthaleneyl)-2H-pyran-2-one; D054512:Phospholipases A2, Calcium-Independent