Lecture 10 - Cartilage Structure And Composition

Question 1

What stabilises collagen?

Answer 1

Covalent cross-links

Question 2

How is a cross link formed?

Answer 2

Formed by two lysine residues which are joined together to form an aldol cross link

Question 3

What is ehlers danlos - type 5?

Answer 3

It is a syndrome where collagen should be strengthen but instead you get stretchiness

Question 4

What is SCAD?

Answer 4

Spontaneous coronary artery dissection - which means that the coronary artery splits as the collagen is ineffective in holding the vessel together and results in a heart attack

Question 5

What are heterofibrils collagens used in adult articular cartilage?

Answer 5

Type 9 and type 11, type 2 is the main collagen type in adults

Question 6

What can mutations in collagens 9 and 11 result in?

Answer 6

Chondrodysplasia syndromes

Question 7

What collagen can be seen in cartilage?

Answer 7

Type 3 - it seems to get more prevalent in oesteroarthitus

Question 8

What is noticeable in the histology with someone who has osteoarthritis (OA)?

Answer 8

There are fewer cells - the cells are dividing but there are spaces where they are no cells

Question 9

What makes a proteoglycan?

Answer 9

Protein and glycan (polysaccharide)

Question 10

Proteoglycans are a special class of …..

Answer 10

Glycoproteins

Question 11

What are proteoglycans normally low and high in?

Answer 11

Low in proteins and high in polysaccharide chains

Question 12

What type of specialised polysaccharide chains are attached to proteoglycans?

Answer 12

Glycoaminoglycans (GAG chains) which are joined by their reducing terminal sugar residues to the protein

Question 13

What do proteoglycans give?

Answer 13

‘Bottle-brush’ confirmation (how it looks)

Question 14

What is attached to the central protein core of a proteoglycan?

Answer 14

GAG chains - which forms the bottle brush Structure

Question 15

Are GAGs highly negatively charged or positively charged?

Answer 15

Highly negatively charged with lots of esters attached to

Question 16

What is an aggrecan?

Answer 16

An aggrecan is a cartilage proteoglycan (all glycoproteins end in can)

Question 17

Why is cartilage proteoglycan called an aggrecan?

Answer 17

Because it aggregates which means it can form gel like properties

Question 18

How can aggrecans be measured?

Answer 18

By finding an increase in viscosity

Question 19

What is the structure of aggrecans?

Answer 19

3 globular domains with a protein core, an N terminal G1, two types of GAGs and keratan sulphate chains (KS) and Chondroitin chains (Cs)

Question 20

What globular chain is very important in aggregation?

Answer 20

G1 which is also the N terminal

Question 21

What are the two ways the Cs chains can be arranged?

Answer 21

Regulatory spaced (Gs1) and in clusters (Gs2)

Question 22

What sulphate chains are shorter, keratan or chondroitin?

Answer 22

Keratan are shorter

Question 23

What is the structure for keratan?

Answer 23

A repeating disaccharide structure, for every disaccharide you get more negative charge

Question 24

What is different for the structure of Keratan and the structure for chondroitin?

Answer 24

Chondroitin has a Glucuronic acid (glucosamine) and keratan has galactose (galactosamine)

Question 25

What is imporant when you stop growing?

Answer 25

Need to stabilise the matrix, stabilise the cartilage so C-6 sulphate is important as well as Keratan

Question 26

What is different to babies and adult cartilage?

Answer 26

The cartilage in babies need to be remodelled, as babies grow therefore cartilage needs to be broken down or calcified to be converted into bone

Question 27

What could happen when you damage cartilage?

Answer 27

The body could use the wrong proteoglycans - could used foetal proteoglycans

Question 28

What happens after every repeating disaccharide in chondroitin cartilage?

Answer 28

Get two negative charges

Question 29

What specific linkage so GAGs have?

Answer 29

Glycosidic linkage (O)

Question 30

What does the level of glycosylation depend on?

Answer 30

The age of the tissue

Question 31

What does aggrecan glycosylation contain?

Answer 31

100 CS chains, 30-60Ks, CS-1 evenly distributed and CS-2 clusters with a MW of 2 million

Question 32

How many repeating disaccharide units does aggrecan glycosylation have in Cs chains?

Answer 32

40 repeating disaccharides with 80 negative charged per chain

Question 33

What is the aggrecan glycosylation like Ks chains?

Answer 33

8000Mw, 8-16 repeating chains with 8-16 negative charges over chain

Question 34

What is the aggrecan protein core like?

Answer 34

G1 - is the N terminal globular region which interacts with another glycosaminoglycan (HYALURONAN)

Question 35

Is hyaluronan sulphated?

Answer 35

NO

Question 36

What is the size of the proteoglycan aggregate dependent on?

Answer 36

How long the hyaluronic acid is

Question 37

What are proteoglycans in the extracellular matrix present as?

Answer 37

Multi molecular aggregates

Question 38

What do aggregates consist of?

Answer 38

Many proteoglycan monomers bound to a single molecule of hyaluronan by an IONIC interaction

Question 39

What does the ionic interaction do in proteoglycan aggregates?

Answer 39

It is stabilised by 2 link proteins with MW of 40,000 and 50,000

Question 40

How large can aggregates be?

Answer 40

Can have a MW weight up to 1million

Question 41

What is hyaluronan important in?

Answer 41

In developing the hindlimb

Question 42

HAS =

Answer 42

Hyaluronic acid synthetase (HAS2) - important in developing the hindlimb

Question 43

What happens if you delete HAS2 genes?

Answer 43

Results in much shorter limbs and the joint is not properly formed

Question 44

What is the development of the joint and limbs like?

Answer 44

Starts off as cartilage and as the joints develop it gets calcified and becomes bone

Question 45

What is the structure of link proteins?

Answer 45

Has immunoglobulin like folds - two other globulin domains which are tandem repeats

Question 46

What is the structure of G1?

Answer 46

It has a similar structure to link proteins, it has N linked sugars which would be linked to asparagine

Question 47

What can G1 interact with?

Answer 47

Hyaluronic acid, it has one A and two B domains, the B domains are involved in binding to hyaluronic acid, A domains bind to each other binding to the link proteins

Question 48

How many sugars of hyaluronic acid is important for binding?

Answer 48

It needs 10 sugars to = 5nm

Question 49

How big are the globular domains?

Answer 49

3x3nm which is big enough to get the 10 sugars of hyaluronic acid

Question 50

What is involved in maintain hydrophobic amino acid?

Answer 50

Tryptophan and is maintains the globular conformation of G1

Question 51

What is necessary to get a reaction between the G1 region and reaping unit of hyaluronan?

Answer 51

3-Nacetyl groups

Question 52

What is the interaction between proteoglycan and hyaluronan like under physiological conditions?

Answer 52

An equilibrium exists between PGS, HA and the complex, equilibrium will shift in favour of the complex group, there is no equilibrium once you add link proteins

Question 53

What has been found in recent studies to do with HAS2?

Answer 53

On cartilage specific HAS2 knockout mice - in the absence of HAS2 gene expression it resulted in severely abnormal Skeleton and perinatal death - Roughley P.J (2006)