Biomedical Engineering Reference
In-Depth Information
LPC
O
O
P
O
O
O
+
CH
3
CH
3
N
OH
LPA
OH
O
O
CH
3
P
Signalling
O
O
OH
Structural
O
O
OH
OH
PC
P
O
O
O
CH
3
CH
3
+
CH
3
N
OH
O
AA
O
OH
O
PA
DAG
O
O
O
Eicosanoids
P
O
O
OH
OH
O
OH
OH
O
O
O
SM
OH
O
SPC
P
OH
O
O
O
CH
3
S1P
N
+
CH
3
P
OH
OH
O
NH
CH
3
O
NH
2
OH
O
CH
3
N
+
CH
3
P
OH
CH
3
O
OH
O
NH
2
OH
O
P
Sph
C1
OH
O
OH
OH
NH
OH
NH
2
O
GlcCer
Cer
OH
OH
OH
HO
OH
O
O
OH
OH
NH
NH
O
O
O
O
P
O
Pl
OH
OH
HO
OH
O
O
OH
OH
PIP
2
O
PIP
PIP
3
O
O
P
O
OH
P
HO
P
OO
O
OH
P
O
OH
O
Cholesterol
Fig. 3.1
The main eukaryotic membrane lipids are PCs. Their diacylglycerol (DAG) backbone
carries a PA esterified to either a choline, ethanolamine, serine, or inositol. The prototypical phos-
pholipid, dipalmitoyl-PtdCho, exhibits nearly cylindrical molecular geometry with a cross-sectional
surface area of 64Å
2
and a head-to-tail length of 19Å [
17
]. The phosphosphingolipid sphingomyelin
(SM) and the glycosphingolipid glucosylceramide (GlcCer) have a ceramide (Cer) backbone, con-
sisting of a sphingoid base (such as sphingosine; Sph), which is amide-linked to a fatty acid.
Yeast sphingolipids carry a C26 fatty acid and have phosphoinositol-X substituents that contain
additional mannoses and phosphates. Breakdown products of membrane lipids serve as lipid sec-
ond messengers. The glycerolipid-derived signaling molecules include lysoPtdCho (LPC), lysoPA
(LPA), PA and DAG. The sphingolipid-derived signaling molecules include sphingosylphosphoryl-
choline (SPC), Sph, sphingosine-1-phosphate (S1P), Cer-1-phosphate (C1P), and Cer. Arachidonic
acid (AA) yields the signaling eicosanoids and endocannabinoids (not shown). The various phos-
phorylated PtdIns molecules (PIPs; also known as the phosphoinositides) mark cellular membranes
and recruit cytosolic proteins. They are interconverted by the actions of kinases and phosphatases.
This figure is drawn based on a figure from [
32
] which was a modified version of an earlier figure
from [
31
] ©Macmillan Publishers Ltd
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