Phospholipase A2 products retain a neuron specific gamma isoform of PKC on the plasma membrane through the C1 domain--a molecular mechanism for sustained enzyme activity.

To clarify molecular mechanism for sustained activation of gamma protein kinase C (gammaPKC), a neuron-specific subtype, we investigated the involvement of phospholipase A2 (PLA2) products in the membrane association of gammaPKC upon activation of G protein coupled purinoceptors in CHO-K1 and NG 108-15 cells. In addition, the functional domain responsible for PLA2-product mediated retention of gammaPKC on the plasma membrane was determined by simultaneously monitoring two different fluorescence-tagged gammaPKCs and mutants in the same living CHO-K1 cells. Purinoceptor activation by UTP induced a transient translocation of gammaPKC from the cytoplasm to the plasma membrane. Interestingly, PLA2 inhibitors, bromoenol lactone (BEL) and arachidonyl-trifluoromethyl ketone (AACOF3), shortened the retention time of gammaPKC on the plasma membrane in cells treated with UTP, while a DAG kinase inhibitor did not affect it. The C1 domain deficient mutant (DeltaC1-gammaPKC) also showed short membrane association compared with wild type gammaPKC, when cells are treated with UTP or arachidonic acid (AA) plus a Ca(2+) ionophore. However, deletion of C1A or C1B subdomains (DeltaC1A-gammaPKC or DeltaC1B-gammaPKC) did not alter the retention time on the plasma membrane, whereas PLA2 inhibitor shortened the retention times of both mutants. These results indicate that PLA2 products prolong the retention of gammaPKC on the plasma membrane through the C1A and/or C1B subdomain in purinoceptor-stimulated CHO-K1 cells. The importance of PLA2 product and C1 domain for the retention of gammaPKC on the membrane was also confirmed using neuronal cell line, suggesting that these are part of molecular machinery for sustaining enzyme activity in neurons.