The ABC's of Group IV cytosolic phospholipase A_2

摘要

The three known human Group IV phospholipase A_2 (PLA_2) paralogs, Group IVA, 1VB and IVC, were overexpressed in Sf9 insect cells using the baculovirus expression system. An endogenous, calcium-independent PLA_2 activity was identified in the insect cell lysates, which can be inhibited by bromoenol lactone (BEL). The Group IV PLA_2 enzymes were characterized in overexpressing insect cell lysates in the presence of BEL, enabling their differentiation from the endogenous PLA_2 activity. Group IVC PLA_2 was found to have significant lysophospholipase activity, while Group IVB PLA_2 did not. Of the three paralogs, only the Group IVA PLA_2 shows enhanced activity in the presence of PIP_2, which enables its differential detection in cell homogenates. RT-PCR was used to demonstrate the presence of all three enzymes in human U937 and human WISH cells, while only Group IVA and Group IVB PLA_2 were detected in tnurine P3S8D_1 cells and human astrocytes at the mRNA level.