Cytosolic phospholipase A 2 and lipoxygenase are involved in cell cycle progression in neuroblastoma cells

Abstract

Arachidonic acid has been implicated in regulating cellular proliferation, and is preferentially released by the 85-kDa cytosolic phospholipase A2 (cPLA2). Recently, we demonstrated that cPLA2 is activated at distinct periods during the ongoing cell cycle of neuroblastoma cells. The purpose of the present study was to establish the role of these cPLA2 activity peaks in cell cycle progression. Inhibition of cPLA2 activity with arachidonyl trifluoromethylketone (ATK) in early G1 phase reduced DNA synthesis markedly. A 24-h incubation with ATK revealed no significant difference in cell number compared to untreated cells, although cPLA2 activity was still inhibited. This suggests redundancy of different PLA2 enzymes. Lipoxygenase inhibition in early G1 resulted in G1 phase arrest, whereas inhibitors for cyclooxygenase had no effect. Furthermore, cells stopped progressing through S phase when lipoxygenase was inhibited in early S phase, demonstrating the requirement of lipoxygenase products for S phase progression.

Focal adhesion signaling and actin stress fibers are dispensable for progression through the ongoing cell cycle

“…We used these cell types because they yield relatively high numbers of mitotic cells and because we have thoroughly characterized cell cycle regulation from mitosis to S phase in both cell lines in previous studies (Hulleman et al, 1999a;Hulleman et al, 1999b;van Rossum et al, 2002). The experimental design is outlined schematically in Fig.…”

Signaling and interplay mediated by phospholipases A2, C, and D in LA-N-1 cell nuclei

“…During these phases, elevations in cPLA 2 activity are due to increased phosphorylation rather than increased cPLA 2 protein expression. This suggestion is supported by studies in which phosphatase treatment of cPLA 2 reduces its activity [42]. The inhibition of cPLA 2 with arachidonyl trifluoromethylketone in early G1 phase markedly reduces DNA synthesis suggesting that cPLA 2 plays an important role in progression of the cell cycle.…”

“…The inhibition of cPLA 2 with arachidonyl trifluoromethylketone in early G1 phase markedly reduces DNA synthesis suggesting that cPLA 2 plays an important role in progression of the cell cycle. Cyclooxygenase inhibitors have no effect on cell cycle progression into S phase [42], indicating that the cPLA 2 -dependent progression is not mediated by arachidonic acid metabolites generated by cyclooxygenase. However, the lipoxygenase inhibitors caffeic acid and nordihydroguaiaretic acid inhibit DNA synthesis when added in early G1 phase [42].…”

Signal Transduction and Actin in the Regulation of G1-Phase Progression

“…49,50 We have shown that cPLA 2 activity increased transiently during mid-G1 phase of the ongoing cell cycle of CHO and neuroblastoma N2A cells, this activity being dependent upon the activity of p42/44. 51,52 By using different inhibitors of cPLA 2 , it was demonstrated that the activity of cPLA 2 in mid-G1 phase was required for entry into S phase. The effects of cPLA 2 inhibition on cell-cycle progression were mediated by lipoxygenase rather than cyclooxygenase products, because G1/S transition was only inhibited when lipoxygenase activity was prevented.…”

“…The effects of cPLA 2 inhibition on cell-cycle progression were mediated by lipoxygenase rather than cyclooxygenase products, because G1/S transition was only inhibited when lipoxygenase activity was prevented. 52,53 In addition to the ERK1/2 pathways, MAP kinase homologs have been identified in mammalian cells such as the JNK/SAPK and the p38 HOG1 kinase. These MAP kinases respond to distinct extracellular stimuli and have different intracellular substrates.…”