Extracellular matrix

Question 1

Define extracellular matrix

Answer 1

Network of molecules deposited by cells that form an insoluble extracellular environment

Question 2

What is the function of the ECM?

Answer 2

Provide physical support
Determine mechanical and physiochemical properties of tissue
Influence growth, adhesion and differentiation status of cells/tissues
Essential for development, function and organogenesis

Question 3

What is the relationship between the ECM and connective tissue?

Answer 3

Specific composition of the ECM determines the biochemical properties of the corresponding connective tissue

Question 4

What are the types disorders resulting from ECM pathology and examples of each?

Answer 4

Gene mutations affecting matrix proteins - Marfan’s
Gene mutations affecting ECM catabolism - Hurler’s
Fibrotic disorders due to XS ECM deposition - Liver fibrosis - cirrhosis
Disorder due to XS loss of ECM - Osteoarthritis

Question 5

What are the major components of the ECM?

Answer 5

Collagens
Elastic fibres
Basal laminae (basement membranes)
Multi-adhesive glycoproteins
Proteoglycans

Question 6

What is the structure of collagen?

Answer 6

3 alpha chains form a left-handed triple helix (each 3rd AA is glycine)
Multiple helices form fibrils which form fibres
Sometimes fibres arranged at 90° to each other in layers

Question 7

What is the purpose of collagen?

Answer 7

Provide tensile strength

Question 8

How many types of collagens are there?

Answer 8

28

Question 9

Explain the biosynthesis of collagen

Answer 9

1) Synthesis of pro-alpha chain
2) Hydroxylation of selected prolines and lysines
3) Glycosylation of slected hydroxylysines
4) Self-assembly of 3 pro-alpha chains
5) Procollagen triple helix formation
6) Secretion out of golgi compartment
7) Cleavage of propeptides
8) Self assembly into fibrl
9) Aggregation of fibrils to form fibre

Question 10

Why are some prolines and lysines hydroxylated during collagen biosynthesis?

Answer 10

Contributes to interchain hydrogen bond formation and allows for covalent crosslinks
Provides tensile strength and stability

Question 11

Define elastic fibres

Answer 11

Provide elasticity to tissues

Question 12

What are elastic fibres composed of?

Answer 12

Core of elastin surrounded by microfibrils, rich in fibrillin protein

Question 13

What is elastin?

Answer 13

Protein consisting of hydrophobic regions and alpha-helical regions (rich in alanine and lysine)
Many lysine side chains are covalently cross linked

Question 14

Define basement membrane/basal laminae

Answer 14

Flexible, thin mats of ECM underlying epithelial sheets and tubes

Question 15

What is the function of the BM?

Answer 15

Separate epithelial cells from connective tissue

Surround muscle, fat and nerve cells

Question 16

What are the 5 major components of the BM?

Answer 16

Nidogen
Perlecan
Laminin
Collagen IV
Integrin