Discussion 8
Hyaluronan, Sulfated Glycosaminoglycans & Glycosaminoglycan Binding Proteins
GalNAc GlcA
Chondroitin/Dermatan
Sulfate
GlcNAc GlcA
Hyaluronan
6S 4S4S4S6S 4S 4S
2S
Glycosaminoglycans (GAG)
IdoA
6S 6S
NS NS3S 2S NS
GlcNAc GlcA
IdoAHeparin/Heparan Sulfate
6S 6S 6S 6S 6S
GalNAc Gal
KeratanSulfate
6S 6S
NS NS3S 2S NS
IdoA
Sulfated Glycosaminoglycans
6S 6S 6S 6S 6S
HONO
GalNAc GlcA
6S 4S4S4S6S 4S 4S
2S
IdoA
Cytosol Golgi
Ser
Galactosyltransferases
Glucuronosyltransferase I
UDP-
Nucleotide sugartransporters
n
GAG Synthases
Sulfated GAG Biosynthesis
UDP-
UDP- UDP-
UDP-
UDP-GlcDehydrogenase
UDP-
UDP-
UDP-GlcADecarboxylase
UDP-
Xylosyltransferases
UDP- UDP-
S S
Sulfotransferases
SS
Biosynthesis of a Heparan Sulfate Chain
NSNS NSNS
6S6S
GalGalGlcA
CopolymeraseComplex
EXT1/EXT2
GlcNAc N-deacetylaseN-sulfotransferases(NDST) (4 isozymes)
3S
GlcNH2/S3-O-sulfotransferases(3OST) (7 isozymes)
2S
Uronic acid2-O-sulfotransferase
IdoA
Epimerase
GlcNAc/S6-O-sulfotransferases(6OST) (3+ isozymes)
6S GlcNAc
EXTL3
Xyl
Proteoglycan Turnover
Plasma membrane
Endocytosis
Step3exoglycosidasesulfatase
Golgi
HS oligosaccharide(~10 kDa)
HS oligosaccharide(~5 kDa)
ProteolyticSheddingEndo-6-sulfatase
HeparanaseProtease
Heparanase
Aggrecan Family
Chondroitin sulfate
Interstitial ProteoglycansSLRPs - Small Leucine Rich Proteoglycans
Gene Knockouts
Decorin(single CS chain)
• Fragile skin• Thin dermis• Increased resistance to
Borrelia burgdorfei
Biglycan(two CS chains)
• Decrease in bone mass and dentin mineralization
• Fewer osteoblasts• Mild muscular dystrophy
Fibromodulin(keratan sulfate)
• Ectopic tendon ossification
Lumican (keratan sulfate)
• Corneal opacification
Perlecan - Basement Membrane Proteoglycan
LDLreceptor-like
repeats
Lamininrepeats
Ig-like repeats Laminin &EGF motifs
467 KDa
Cell-BindingDomain
TM
C1
C2
V
Glypicans GPI anchored proteins
6 members
Syndecans Type I Membrane Proteins
4 members
Hyaluronan
n ~ 50,000
Hyaluronan as a Scaffold
HyaluronicAcid
Aggrecan
A B C
OO
OOH
NSO3-
OSO3-
OCOO-
OH
OSO3-
OO
OOSO3
-
NSO3-
±OSO3-
O
COO-
OH
OH
OOH
NAc
OSO3-
OOO
O
OOH
NSO3-
OSO3-
OCOO-
OH
OSO3-
OO
OOH
NSO3-
OSO3-
OCOO-
OH
OSO3-
OOH
NSO3-
OH
OO
Heparan Sulfate Structure is Complex
Antithrombin-Heparin
OO
OOH
NHSO3-
OSO3-
OCOO-OH
OSO3-
OO
OOSO3
-
NHSO3-
±OSO3-
O
COO-
OH
OH
OOH
NAc
OSO3-
OO
FGF
Heparan sulfate
FGF
Any Cell
Coreceptors
Heparan sulfate
Depots and Gradients
Hh
WntBasement
Membranes andOther ECMs
MatrixProteins
Col Fn
Heparan Sulfate Proteoglycans
FGF-Heparin Hexasaccharide
Crystal structure shows surface binding
119KRTGQYKLGSKTGPGQK135
FGF FGF
Mulloy & Linhardt (2001) COSB 11:623
• Symmetric structure
• Heparin interacts with both ligands and receptors
• Two heparin oligosaccharides present in crystal
Heparin
6S
NS
6S
NS
6S
NS2S 2S 2S
6S
NS
6S
NS2S 2S
Heparin versus Heparan Sulfate
The difference between heparin and heparan sulfate is quantitative not qualitative
6S6S
NS NS3S 2S NS
2S
6S
NS