ATP-induced mitogenesis is modulated by phospholipase D2 through extracellular signal regulated protein kinase dephosphorylation in rat pheochromocytoma PC12 cells

Extracellular ATP has been known to have many functions as a fast transmitt er, and a co-transmitter, and to have morphogenic and mitogenic activity in neuronal cells. Although it was reported that ATP activates phospholipase D (PLD), the role of PLD versus the ATP function was unclear in neuronal ce lls. In this study, we investigated the role of PLD on the ATP-induced extr acellular signal regulated protein kinase (ERK) activation and mitogenic ef fect in rat pheochromocytoma PC12 cells. In these cells ATP caused PLD2 act ivation and ERK phosphorylation, which was dramatically reduced by wild-typ e PLD2-overexpression but not by lipase-inactive-mutant PLD2-overexpression . The accumulation of phosphatidic acid (PA) by preincubating PC12 cells wi th propranolol (an inhibitor of PA phosphohydrolase) also decreased the ERK phosphorylation. Inhibition of phosphatases; by okadaic acid or pervanadat e completely blocked PLD2-dependent ERK dephosphorylation. In addition, ATP -stimulated thymidine incorporation was reduced by the overexpression of wi ld-type PLD2, but not by the overexpression of lipase-inactive-mutant PLD2. Okadaic acid pretreatment overcame the decrease of ATP-induced thymidine i ncorporation by PLD2 overexpression. Taken together, we suggest that PLD2 a ctivity might play a negative role in ATP-induced ERK phosphorylation and m itogenic signal possibly through phosphatases. (C) 2001 Elsevier Science Ir eland Ltd. All rights reserved.