Principles of cell signaling - UT Southwestern

39057_ch14_cellbio.qxd 8/28/06 5:11 PM Page 610
lipid species play numerous roles in cell signaling.
Because their analysis has been more difficult
than for soluble messengers, many
probably remain to be discovered and understood.
FIGURE 14.17 shows the structure of some
of these lipids.
Phospholipase Cs (PLCs) are the prototypical
lipid signaling enzymes. PLC isoforms catalyze
the hydrolysis of phospholipids between
the 3-sn-hydroxyl and the phosphate group to
yield a diacylglycerol and phosphate ester. In
animals and fungi, PLCs specific for the substrate
Structures of some lipid second messengers
O
Phosphatidylinositol (PI)
O
O
O
HO
OH
O
2
O
3
P
1
O -
O
6 OH
4 5
OH
OH
O
Phosphatidylinositol-3,4,5-trisphosphate (PIP 3 )
O
O
O
H - O 3 PO
HO
OH
OH
O -
O
P
O
O
6 OH
2 1 4 5
3
OPO 3 H -
OPO 3 H -
O
Diacylglycerol (DAG)
O
O
O
OH
OPO 3 H -
6 OH
2 1 4 5
3
Inositol trisphosphate (IP 3 )
OPO 3 H -
OPO 3 H -
O
Phosphatidic acid (PA)
O
O
O
O
O-
P
O -
O
FIGURE 14.17 Structures of some lipid second messengers and the common precursor phosphatidylinositol.
The acyl side chain structures shown here are the most common for mammalian PI lipids. Much of the PA in
cells is derived from PC, and its acyl chains may differ from those shown.
610 CHAPTER 14 Principles of cell signaling