6 - Extracellular Matrix Biology II

Question 1

Why are glycoproteins multi-adhesive?

Answer 1

different regions of the molecule can bind to different molecules

They are very large modular proteins

Question 2

What shape are laminins?
How many chains does it contain?
Where is it found?

Answer 2

cross-shaped
contains 3 chains - α, β and γ
found in all basement membranes

Question 3

What is the cause of congenital muscular dystrophy?

Answer 3

absence of α2 in laminin 2

Question 4

What are the symptoms of congenital MD?

Answer 4

hypotonia
generalised weakness
deformities of the joints

Question 5

Where are fibronectins found?

Answer 5

(not in the BM)
a major connective tissue glycoprotein
can exist as insoluble fibrillar matrix or soluble plasma protein

Question 6

How are different form of fibronectin formed?

Answer 6

NOTE: fibronetins are only derived from one gene

different forms come fro different types of mRNA splicing

Question 7

Give some characteristic of fibronectin?

Answer 7

• large

- multi-adhesive

Question 8

What are fibronectins used for?

Answer 8

• regulating cell adhesion and migration in embryogenesis and tissue repair
• important for wound healing
• forms a mechanical continuum with the cacti cytoskeleton

NOTE: no known mutations in humans (suggests it is essential for life)

Question 9

How does fibronectin link collagen fibres to the actin filaments?

Answer 9

collagen fiber
fibronectin
integrin (embedded in the plasma membrane)
adaptor proteins
actin filament

Question 10

What are the structural characteristics of the GAG chains?

Answer 10

• one of the sugars in the repeating disaccharide is an amino acid
• highly negatively charged - many GAGs are sulphated or carboxylated

Question 11

What are the characteristic feature of hyaluronan?

Answer 11

a huge molecule (occupies around the same volume as a bacterium)

Question 12

What are the characteristics of decorin?

Answer 12

small proteoglycan
binds to collagen fibres - regulates collar fiber size and arrangement
(contributes to the strength of skin)

Question 13

How does hyaluronan play a part in hyaline cartilage?

Answer 13

(hyaluronan - more core protein, but it is a high molecule)
In hyaline cartilage, the core protein of aggrecan is led to hyaluronan

Additionally, it has a link protein. SO THE OVERALL COMPLEX IS VERY LARGE

Question 14

What effects does osteoarthritis have and how does this occur?

Answer 14

joint stiffness and the rubbing of bones against each other
this is due to loss of cartilage, inflammation and new bone formation
(aggrecan gets degraded and the fragments get lost in the synovial fluid)