Discussion 8 Hyaluronan, Sulfated Glycosaminoglycans & Glycosaminoglycan Binding Proteins

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