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In-Depth Information
Inositol lipids
Phosphoinositide 3-kinase
Phosphatidylinositol (PI)
Phosphatidylinositol-4-phosphate (PIP)
Phosphatidylinositol-4,5-bisphosphate (PIP2)
Phospholipase C
Diacyl glycerol (DAG)
Inositol 1,4,5-trisphosphate (IP3)
Phosphatidic acid (PA)
Fig. 8.1
Phospholipase C-mediated pathway in generation of the second messengers IP3, DAG,
and PA (Adapted from Sang et al.
2001
; Anthony et al.
2006
)
4,5-bisphosphate (PIP
2
) to generate the second messengers diacylglycerol (DAG)
and inositol 1,4-bisphosphate (IP2) or inositol 1,4,5-trisphosphate (IP
3
), respec-
tively. IP
2
can be subsequently phosphorylated to IP
3
(Lanteri et al.
2008
). The sec-
ond product of PLC activity, DAG, can be phosphorylated to phosphatidic acid (PA)
through the action of DAG kinase (Munnik
2001
; Lanteri et al.
2008
). PA can be
dephosphorylated to DAG (Munnik et al.
1995
).
PA can also be synthesized by the action of PLD (Fig.
8.2
). PLD hydrolyzes
structural phospholipids such as phosphatidylcholine (PC) or phosphatidylethanol-
amine (PE) at the terminal phosphodiester bond to produce PA and free head groups
such as choline (Wang
2001
). Several specifi c elicitors or pathogen-associated
molecular pattern (PAMPs) are known to activate PLC/DAG kinase- enzymatic
pathway and biosynthesis of PA (Van der Luit et al.
2000
; de Jong et al.
2004
;
Yamaguchi et al.
2005
).
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