Polar Lipid Synthesis. Lipids: Role in Signaling.

Polar Lipid Synthesis

glycerol

phosphatidic acid

C

C

C

O

O O X

O

O

-

P

O C R1

O

CR2

O

OHOH

OH

HOOH

CH2 C NH3

COO-

+

CH2CH2NH3

+

CH2CH2N(CH3)3

+

H

H

H

Hwater

ethanolamine

choline

serine

inositol

glycerol CH2CH(OH)CH2OH

glycerophospholipidformula of XX-OH

phosphatidic acid

phosphatidylethanolamine

phosphatidylcholine

phosphatidylserine

diphosphatidylgycerol (cardiolipin)

phosphatidylinositol

CH2CH(OH)CH2O

CH2OCR1

R2COCH

CH2

O

OP

O-

O

phosphatidylglycerol

phosphatidylglycerol

O H

C H2

O H

N H2

+sphinganine

C

C

C

OH

glycerol-3-P

HO

C

C

C

OH

C

C

C

HO

O O-

O

O-

P O O-

O

O-

P

O

O O-

O

O-

P

C

C

C O O-

O

O-

P

O

O C R1

O

O C R1

O

dihydroxacetone-P

1-acylglycerol-3-P 1-acyldihydroxyacetone-P

C

C

C

O

O O-

O

O-

P

O C R1

O

CR2

O

C

C

C

O

OH

O C R1

O

CR2

O

phosphatidic acid

diacylglycerol

glycerol-3-Pacyltransferase

dihydroxyacetone-Pacyltransferase

CoACoA

R1-C-CoA

O

R1-C-CoA

O

R2-C-CoA

O

CoA

CDP-diacylglycerol

CTP

PPi

phosphatidatecytidylyltransferase

ATP

ADP

phosphatidic acidphosphatase

NADPHNADP+

reductase

C

C

C

O

OH

O C R1

O

CR2

O C

C

C

O

OH

O C R1

O

CR2

O

diacylglycerol

C

C

C

O

O OCH2CH2NH3

O

O-

P

O C R1

O

CR2

O

phosphatidylethanolamine

+

C

C

C

O

O OCH2CH2N(CH3)3

O

O-

P

O C R1

O

CR2

O

phosphatidylcholine

+

HOCH2CH2N(CH3)3HOCH2CH2NH3

-O

O

O-

P O

O

O-

POCH2CH2NH3 OCH2CH2N(CH3)3

-O

O

O

P-O

O

O

P O

O

O-

P OCH2CH2N(CH3)3O

O

O-

P OCH2CH2NH3

ethanolamine choline

phosphoethanolamine phosphocholine

CDP-ethanolamine CDP-choline

ethanolaminekinase

cholinekinase

CTP: phosphoethanolaminecytidylyltransferase

CTP: phosphocholinecytidylyltransferase

ATP

ADP

ATP

ADP

CTPCTP

PPiPPi

CMPCMP

cytidinecytidine

CDP-choline:1,2-diacylglycerolphosphocholinetransferase

CDP-ethanolamine:1,2-diacylglycerolphosphoethanolaminetransferase

C

C

C

O

O OCH2CH2NH3

O

O-

P

O C R1

O

CR2

O

phosphatidylethanolamine

+

C

C

C

O

O OCH2CH2N(CH3)3

O

O-

P

O C R1

O

CR2

O

phosphatidylcholine

+

C

C

C

O

O OCH2CH2NH2

O

O-

P

O C R1

O

CR2

O

+

C

C

C

O

O OCH2CH2NH

O

O-

P

O C R1

O

CR2

O

+

S-adenosylmethionine

S-adenosylhomocysteine

S-adenosylmethionine

S-adenosylmethionine

S-adenosylhomocysteine

S-adenosylhomocysteine

CH3

CH3

CH3

C

C

C

O

O O

O

O-

P

O C R1

O

CR2

O

CH2 C NH3

COO-

+

phosphatidylserine

serine serine

ethanolamineethanolamine

CO2

phosphatidylserinedecarboxylase

base exchange reaction

C

C

C

O

O

O C R1

O

CR2

O C

C

C

O

O

O C R1

O

CR2

O

P O

O

O-

CMP

CDP-diacylglycerol

C

C

C

O

O

O C R1

O

CR2

O C

C

C

O

O

O C R1

O

CR2

O

P O

O

O

C

C

C

O

O

O C R1

O

CR2

O C

C

C

O

O

O C R1

O

CR2

O

P

O

O-

O

CH2

C

CH2

P O

O

O-

-O

OH

phosphatidylglycerolphosphate

phosphatidylglycerol

cardiolipin

glycerol-3-phosphate

phosphatase

CMP

glycerophosphatephosphatidyltransferase

Pi

CMP

CDP-diacylglycerol

cardiolipinsynthase

inositol

CMP

phosphatidylinositolsynthase

OHOH

OH

HO

OH

phosphatidylinositol

C

C

C

O

O OCH2CH2NH3

O

O-

P

O R1

CR2

O

1-alkyl-2-acylglycerophosphoethanolamine

+

C

C

C

O

O OCH2CH2NH3

O

O-

P

O

CR2

O

+

C C R1CH2CH2

plasmalogen

NADH H+ NAD+ 2 H2OO2 ++ +

C

C

C

O

O OCH2CH2N(CH3)3

O

O-

P

O

C

O

+

R1CH2CH2C

C

C

HO

O OCH2CH2N(CH3)3

O

O-

P

O

+

R1CH2CH2

H2O

O-C

O

CH3

C

O

CH3 CoA CoA

platelet activating factor1-alkyl-2-lysophosphatidylcholine

desaturase

acetylhydrolase

acetylCoA transferase

C

C

C

O

O OCH2CH2N(CH3)3

O

O-

P

O C

O

C

O

dipalmitoylphosphatidylcholine

+

(CH2)14CH3

CH3(CH2)14

1-palmitoyl-2-acylglycerophosphocholine

1-palmitoyl-2-lysoglycerophosphocholine

phospholipase A2

acyltransferase

O-C

O

R2

CoA

C

O

CH3(CH2)14 CoA

CH3

CoA

O

O

OH

OH

OH

CH2OH

CH2OH

CH2OH

CH2OH

NH3

NH3

+

+

NH

NH

CH3-(CH2)n

CH3-(CH2)n

O

O

C

CH2OH

COO-

H3N H+

NADPH

NADP

fatty acyl-CoA

CoA

CO2CoA

NAD(P)H

NAD(P)

1/2 O2

H2O+

+

+

+

palmitoyl CoA

serine

ketosphinganine

sphinganine

dihydroceramide

ceramide

serinepalmitoyltransferase

ketosphinganinereductase

dihydroceramidesynthase

dihydroceramidedesaturase

+

CH2OH

CH2O_P_O_CH2_CH2-N(CH3)3

OH

NH

O

CH3_(CH2)n

O

O

+

-

sphingomyelin

ceramide

sphingomyelinsynthase

PC

DG

OH

NH

O

CH3_(CH2)n

Cerebroside and ganglioside synthesisOccurs on the lumenal side of the Golgi

Ceramide

UDP-Glc UDP-GalUDP UDP

Glc-ceramide Gal-ceramide

UDP-Gal PAPS UDP-Gal UDP 3’-P-PMP UDP

3-SO3—Gal-ceramide Gal-Gal-ceramide

Gal-Glc-ceramide

UDP-Gal CMP-NeuAc UDP CMP

Gal-Gal-Glc-ceramide NeuAc-Gal-Glc-ceramide

UDP-GalNAc NeuAc UDP-GalNAc UDP UDP

GalNAc-Gal-Glc-ceramide GalNAc-Gal-Glc-ceramide

NeuAc UDP-Gal

UDP

Gal-GalNAc-Gal-Glc-ceramide

Ganglioside and cerebroside catabolism

Gal-GalNac-Gal-Glc-ceramide (GM1)

NeuAc β-galactosidas e [1]

Gal

GalNAc-Gal-Glc-ceramide (GM2) GalNAc-Gal-Ga-l Glc-ceramide

NeuAc β-N-acetylhexosaminidas e A[2] β-N-acetylhexosaminidase

GalNAc GalNAc

NeuAc-Gal-Glc-ceramide (GM3) Ga-l Ga-l Glc-ceramide

Neuraminidase α-galactosidas eA [3]

NeuAc GalGa-l Glc-ceramide

β-galactosidase

Gal

Glc-ceramide

β-glucosidas e[4] Glc

Gal GalGa-l Ga-l ceramide Ga-l ceramide Ceramide

α-galactosidase β-galactosidas e[5] ceramidase [6]

S 4O 2- long-chai n baseArylsulfata seA [7] Fatt y acid

3-SO3-Gal-ceramide

Disease Deficient enzyme activity Reaction

Farber’s lipogranulomatosis ceramidase (6)ceramide = fatty acid + long-chain base

Niemann-Pick disease sphingomyelinase sphingomyelin = ceramide + phosphocholine

Gaucher’s disease B-glucosidase (4)Glc-ceramide = Glc + ceramide

Fabry’s disease a-galactosidase A (3)Gal-Gal-Glc-ceramide = Gal + Gal-Glc-ceramide

Tay-Sachs disease hexosaminidase A (2)GM2 = GM3 + GalNAc

Sandhoff’s disease hexosaminidase A + B (2)GM2 = GM3 + GalNAc

Sulfatide lipidosis arylsulfatase A (7)3’-SO3—Gal-ceramide = Gal-ceramide + SO4

2-

Galactosylceramide lipidosis B-galactosidase (5)Gal-ceramide = Gal + ceramide

GM1 gangliosidosis GM1-B-galactosidase (1)

GM1 = Gal + GM2

Lipids: Role in Signaling

1st messenger (hormone, neurotransmitter, growth factor, etc.)

2nd messenger (calcium, cAMP, IP3, DAG, ceramide)

Signal amplification

Modulator ( G protein, receptor tyrosine kinase)

Enzyme activation (phospholipases, adenylate cyclase)

Enzyme activation (PKA, PKC, phosphatases)

substrates

Discovery of the "phospholipid effect" by Hokin MR et al. : phosphorus incorporation into phospholipids showed a remarkable increase in pigeon pancreas slices on stimulation with acetylcholine (J Biol Chem 1953, 203, 967).

Michell RH in a famous review proposed for the first time that the "phosphoinositide effect” discovered in 1953 by Hokin plays a role in cellular calcium mobilization (Biochim Biophys Acta 1975, 415, 81)

Univ. of Birmingham, UK

A com mon paradigm in the transmission of signals across a cellmembrane by agents such as hormones, neurotransmitters, etc. isthe catabolism of complex membrane lipids. When the lipid substrateis a glycerolipid, catabolism is initiated by a group of enzymes knownas phospholipases that release bioactive lipids. These enzymes arenamed according to their site of cleavage of the complex lipid:

Phospholipases C and D release diacylglycerol (DG) andphosphatidic acid (PA), respectively. The other metabolic products ofthese reactions are a headgroup or its phosphorylated derivative.

Phospholipase A1 and A2 b oth release fatty acids from the par entlipid. In the case of phospholipase A2, t he released fatty acid isusually arachidonic acid (AA) that serves as a precursor forprostaglandin, leukotriene, and thromboxane synthesis.

DG, PA, and AA are all bioactive and capable of activating variouscellular targets. The water-soluble products, which are also releasedby t hese lipases, are typically inactive except for the case of PLCcleavage of PIP2, i n which case the released headgroup, inositoltrisphosphate IP3, also serves as a signaling molecule.

When the lipid substrate is a sphingolipid, catabolism is the result ofcleavage by sphingomyelinase, a specific type of p hospholipase Cthat generates ceramide and phosphocholine. Ceramide is anotherbioactive lipid metabolite that plays an important role in non-proliferative cell biologies such as g rowth arrest, differentiation, andprogrammed cell death (apoptosis).

C

C

C

O

O OX

O

O-

P

O C R1

O

CR2

O

C

C

C

O

OH

O C R1

O

CR2

O C

C

C

O

O OH

O

O-

P

O C R1

O

CR2

O

C

C

C

O

O OX

O

O-

P

OH

CR2

O C

C

C

HO

O OX

O

O-

P

O C R1

O

-O OX

O

O-

P HOX

-O C R1

O

O-CR2

O

phospholipase C phospholipase D

phospholipase A1 phospholipase A2

diacylglycerol phosphatidic acid

monoacylglycerolphosphate monoacylglycerolphosphate

glycerophospholipid

usually acrachidonicacid

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Rates of lipid flip-flop across bilayers

Diacylgycerol 0.1 sec

Ceramide 10 min

Phosphatdiylcholine 10 hr

Lysophosphatidic acid >10 hr

Ganglioside >>10 hr

Conclusion: as the headgroup becomes more polar or larger and as the hydrophobic moiety becomes smaller, the lipid flips less readily

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CH2O_P_O_CH2_CH2-N(CH3)3

OH

NH

O

CH3_(CH2)n

O

O

+

-

sphingomyelin

CH2OH

ceramide

OH

NH

O

CH3_(CH2)n

phosphocholine

sphingomyelinase

ceramide

Ceramide-activatedprotein phosphatase(PP2A, PP1)

Ceramide-activated protein kinase

Protein kinase C zeta

Rb dephosphorylation

Growth arrest inflammation

?

?

?

Lipids as receptor agonists

– Platelet-activating factor

– Lysophosphatidic acid

– Sphingosine phosphate

– Lipopolysaccharide

Platelet-activating factor (PAF) or 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine

– an ether analogue of phosphatidylcholine

– causes aggregation of platelets at picomolar concentrations

– acts through a G-protein coupled receptor

Model of G-protein coupled receptor (PAF receptor)signal transduction

Lysophosphatidic acid or 1-acyl-sn-glycerol-3-phosphate (LPA)

–metabolite of phosphatidic acid

–is an important serum mitogen

–acts through the EDG family of G-protein coupled receptors

CH2OP-O-

NH3

OHO-

O

Sphingosine phosphate

–Synthesized by sphingosine kinase

–Acts through the EDG family of G protein coupled receptors

–Also considered to be mitogenic

Bacterial cell wall organization