Transcript GAG binding proteins - Glycobiology Research and Training

Discussion 8
Hyaluronan, Sulfated Glycosaminoglycans &
Glycosaminoglycan Binding Proteins
Glycosaminoglycans (GAG)
b4
Hyaluronan
b3
b4
b3
b4
b3
b4
b3
b4
b3
GlcNAc GlcA
IdoA
Chondroitin/
Dermatan
Sulfate
Heparin/
Heparan
Sulfate
6S
4S6S
b4
b3
b4
b3
4S
b4
b3
a4
b3
GalNAc
Gal
b4
4S
b4
4S
b3
a3
2S
b4
6S
a3
b3
b4
GalNAc GlcA
a4
b4
a4
b4
6S
a4
b4
NS
GlcNAc GlcA
Keratan
Sulfate
4S
6S
b3
b4
6S
b3
b4
6S
6S
IdoA
a4
NS3S
b3
6S
b4
b3
a4
2S
NS
b4
Sulfated Glycosaminoglycans
IdoA
6S
4S6S
b4
b3
b4
b3
4S
b4
b3
4S
b4
b4
b4
a4
b4
a4
b4
6S
a4
b4
NS
a3
6S
IdoA
a4
NS3S
a4
2S
NS
HONO
b3
6S
b4
4S
2S
GalNAc GlcA
a4
a3
4S
6S
b3
b4
6S
b3
b4
6S
b3
6S
b4
b3
b4
Sulfated GAG Biosynthesis
UDP-Glc
Dehydrogenase
UDP-GlcA
Decarboxylase
Nucleotide sugar
transporters
UDP-
Xylosyltransferases
UDPUDP-
Sulfotransferases
UDP-
S
UDPUDP-
UDPUDPUDP-
UDP-
Cytosol
n
S
Ser
S
GAG Synthases
Golgi
S
Galactosyltransferases
Glucuronosyltransferase I
Biosynthesis of a Heparan Sulfate Chain
GlcNAc/S
6-O-sulfotransferases
Epimerase (6OST) (3+ isozymes)
Copolymerase
Complex
EXT1/EXT2
6S
NS
GlcNAc N-deacetylase
N-sulfotransferases
(NDST) (4 isozymes)
NS
3S
IdoA 6S
6S
NS 2S NS
Uronic acid
2-O-sulfotransferase
GlcNH2/S
3-O-sulfotransferases
(3OST) (7 isozymes)
EXTL3
GlcNAc
GlcA Gal Gal Xyl
Proteoglycan Turnover
Heparanase
Endo-6-sulfatase
Proteolytic
Shedding
Plasma membrane
Endocytosis
Golgi
Heparanase
Protease
HS oligosaccharide
(~10 kDa)
HS oligosaccharide
(~5 kDa)
Step3
exoglycosidase
sulfatase
Aggrecan Family
Chondroitin sulfate
Interstitial Proteoglycans
SLRPs - 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
467 KDa
LDL
receptor-like
repeats
Laminin
repeats
Ig-like repeats
Laminin &
EGF motifs
Syndecans
Type I Membrane Proteins
4 members
Glypicans
GPI anchored proteins
6 members
Cell-Binding
Domain
TM
C1
V
C2
Hyaluronan
HO
OH
O
O
NHAc
HO2C
O
O
HO
OH
n ~ 50,000
b4
b3
b4
b3
b4
b3
b4
b3
b4
b3
Hyaluronan as a Scaffold
Aggrecan
Hyaluronic
Acid
A
B
C
Heparan Sulfate Structure is Complex
OSO3-
OH
O
O
OH
O
NSO3
-
COOOH
O
OSO3-
O
O
OSO3
-
OH
O
NSO3
-
COOOH
OSO3-
O
O
O
OSO3
-
O
OH
O
NSO3
-
O
O
OH
O
NAc
±OSO3-
COOO
OH
OH
O
OSO3-
O
NSO3
-
OSO3COOOH
O
O
O
OSO3
-
OH
O
NSO3-
Antithrombin-Heparin
OSO3O
O
OH
O
O
NAc
OSO3-
±OSO3-
COO-
O
O
OH
OH
OSO3
-
O
NHSO3-
COO
OH
O
O
O
OSO3-
OH
O
NHSO3-
Heparan Sulfate Proteoglycans
Wnt
Heparan sulfate
Basement
Membranes and
Other ECMs
Hh
Depots and
Gradients
Matrix
Proteins
Heparan sulfate
Coreceptors
Any Cell
FGF
FGF
Co
l
Fn
FGF-Heparin Hexasaccharide
Crystal structure shows surface
binding
119KRTGQYKLGSKTGPGQK135
Heparin
FGF
• Symmetric structure
FGF
• Heparin interacts with both
ligands and receptors
• Two heparin
oligosaccharides present
in crystal
Mulloy & Linhardt (2001) COSB 11:623
6S
NS
a4
a4
2S
6S
NS
a4
a4
2S
6S
NS
a4
a4
2S
6S
NS
a4
a4
2S
6S
NS
a4
2S
Heparin versus Heparan Sulfate
a4
b4
a4
b4
6S
NS
a4
a4
2S
6S
NS
a4
b4
6S
a4
NS3S
a4
2S
NS
The difference between heparin and heparan sulfate is
quantitative not qualitative