Abstract
Extracellular ATP has been known to modulate various cellular responses including mitogenesis, secretion and morphogenic activity in neuronal cells. In the ATP-induced morphogenic activity, focal adhesion kinase(s) such as Fak have been suggested to play a critical role. Binding of ATP to its specific cell surface receptor in PC12 cells induces phospholipase D (PLD) activity. However, the role of PLD on ATP-induced Fak activation in PC12 cells remains unclear. In this study, we investigated the role of PLD on the ATP-induced Fak activation and paxillin phosphorylation using two established cell lines: wild type PLD2- and lipase-inactive mutant PLD2-inducible PC12 cells. Stimulation of cells with ATP caused PLD2 activation via classical protein kinase C activation. ATP also induced Fak activation, and paxillin phosphorylation, and were dramatically reduced by wild type PLD2 overexpression but not by lipase-inactive mutant PLD2 overexpression. When the PC12 cells were pretreated with propranolol, a specific inhibitor for phosphatidic acid phosphohydrolase resulting in the accumulation of PA, ATP-induced Fak activation and paxillin phosphorylation were also reduced. We found that inhibition of tyrosine phosphatases by pervanadate completely blocked PLD2-dependent Fak and paxillin dephosphorylation. Taken together, we suggest that PLD2 activity might play a negative role in ATP-induced Fak and paxillin phosphorylation possibly through tyrosine phosphatases.
Highlights
Purinergic receptors have been reported to play important roles on the regulation of neuronal cell functions (Communi et al, 2000; Di Iorio et al, 1998)
Only Gö6976 but not rottlerin inhibited ATP-induced PLD2 activity. These results indicate that ATP stimulates PLD2 activity via classical protein kinase C (PKC) in PC12 cells
We showed that overexpression of PLD2 inhibited ATP-induced focal adhesion kinase (Fak) and paxillin phosphorylation (Figure 2 and 3)
Summary
Purinergic receptors have been reported to play important roles on the regulation of neuronal cell functions (Communi et al, 2000; Di Iorio et al, 1998). Stimulation of cells with ATP induces tyrosine phosphorylation of several cytoskeletal proteins and focal adhesion molecules such as focal adhesion kinase (Fak), prolinerich tyrosine kinase (Pyk2), and paxillin (Soltoff et al, 1998; Schindelholz et al, 2000). Since these cytoskeleton-associated proteins have been regarded as important factors for the regulation of neuronal cell functions, the study on the regulatory mechanism for the proteins remains an important issue. We investigated the role of PLD2 activity on ATPinduced Fak and paxillin phosphorylation in PC12 cells
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