Cytosolic phospholipase A₂ activity during the ongoing cell cycle

Abstract

Cytosolic phospholipase A(2) (cPLA(2)) is of special interest because it selectively releases arachidonic acid from membrane phospholipids. Arachidonic acid has been implicated to play an important role in various cellular responses. Recently arachidonic acid release and prostaglandin synthesis have been shown to be cell cycle dependent and therefore the activity of cPLA(2) during the ongoing cell cycle was investigated, using the mitotic shake off method for cell synchronisation. cPLA(2) activity was high in mitotic cells and decreased rapidly in the early G1 phase. A strong increase in activity was measured following the G1/S transition in both neuroblastoma and Chinese hamster ovary cells. The changes in activity were not due to a difference in cPLA(2) expression but due to phosphorylation of cPLA(2). Phosphorylation of cPLA(2) occurs through MAPK since the use of a specific MAPK kinase inhibitor and serum depletion of synchronised cells inhibited cPLA(2) activity.

Inhibitors of phosphatidylinositol 3-kinase activity prevent cell cycle progression and induce apoptosis at the M/G1 transition in CHO cells

“…In figure 2, the expression pattern of cyclin A is shown 0, 2, 4, 6, 8, 10, and 12 h after mitosis, in the absence and presence of the PI3-kinase inhibitor LY294002, added to the cells during mitosis. At 8 h after mitosis, corresponding to late G1/early S phase, a significant increase in cyclin A expression was observed in control cells, as has been described earlier [30]. The increase in cyclin A expression was not caused by changes in protein as deduced from p42 MAPK expression used as a loading control ( fig.…”

“…Mitotic CHO cells were collected by the shake-off procedure described in Materials and methods. The effect of PI3-kinase inhibition at different points during the G1 phase on the proliferative capacity of the cells was examined by determination of thymidine incorporation in the absence or presence of LY294002[30]. (A) 3 HTdR incorporation was measured after 14 h of cell growth in the absence (Control) or presence (0, 2, 4 and 6 h) of the PI3-kinase inhibitors wortmannin (100 nM, left bar) and LY294002 (20 mM, right bar).…”

PPARγ ligand production is tightly linked to clonal expansion during initiation of adipocyte differentiation

“…Of the known families of phospholipases, PLA 2 , PLC, and PLD, only PLA 2 releases the free fatty acid directly. Interestingly, the activity of cytoplasmic phospholipase A 2 (cPLA 2 ) is upregulated by proliferation ( 44 ). The activity and localization of cPLA 2 are regulated by an activating phosphorylation by p42/p44 MAPKs.…”

Cell cycle dependent regulation of gap junction coupling and apoptosis in GFSHR-17 granulosa cells

“…To achieve a synchronisation of the GFSHR-17 granulosa cells, mitotic cells were isolated from a monolayer using the mitotic-shake-off technique [21]. This technique is based on the observation that cells in mitosis do not adhere very well to the surface.…”