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1.1 POM Cells > Extracellular `Matrix > Flashcards

Extracellular `Matrix Flashcards

1
Q

What are the macromolecules making up ECM?

A
  1. Protein
  2. Carbohydrates
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2
Q

What is ECM?

A

Extracellular matrix

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3
Q

What are the 4 functions of ECM?

A
  1. Physical support
  2. Tissue properties
  3. Influences cell growth/adhesion/differentiation
  4. Organogenesis
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4
Q

Which cells deposit ECM?

A

Fibroblasts

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5
Q

What are the 3 components of ECM?

A
  1. Collagens
  2. Glycoproteins (multi-adhesive)
  3. Proteoglycans
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6
Q

What are the 4 types of collagens in connective tissue?

A
  1. I
  2. II
  3. III
  4. IV —> basement membrane
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7
Q

What are the 3 types of multi-adhesive glycoproteins in connective tissue?

A
  1. Fibronectin
  2. Fibrinogen
  3. Laminins —> basement membrane
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8
Q

What are the 4 types of proteoglycans in connective tissue?

A
  1. Aggrecan
  2. Versican
  3. Decorin
  4. Perlecan —> basement membrane
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9
Q

What are the 3 components of the basement membrane?

A
  1. Type IV collagen
  2. Laminins
  3. Perlecan
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10
Q

How do matrix components interact with cells?

A

Bind to integrins on cell surface (receptors)

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11
Q

What are integrins?

A

Transmembrane cell adhesion receptors —> mediating cell-to-cell and cell-ECM interactions

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12
Q

What are the 2 properties of tendon and skin tissue?

A
  1. Tough
  2. Flexible
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13
Q

What are the 2 properties of bone tissue?

A
  1. Hard
  2. Dense
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14
Q

What are the 2 properties of cartiledge tissue?

A
  1. Resilient
  2. Shock-absorbing
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15
Q

Are connective tissue properties consistent around the body?

A

No —> vary depending on tissue function

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16
Q

How does connective tissue vary its properties?

A
  1. Different ECM components (eg. collagen types)
  2. Different arrangements of collagen
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17
Q

How do ECM abnormalities arise? (4)

A
  1. Mutations affecting ECM proteins
  2. Mutations affecting ECM catabolism
  3. Excess ECM
  4. Loss of ECM
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18
Q

What are 5 examples of disorders resulting from mutated ECM proteins?

A
  1. Osteogenesis imperfecta (Brittle bones) - collagen I
  2. Marfan’s syndrome - fibrillin I
  3. Alport’s syndrome - collagen IV
  4. Epidermolysis Bullosa - laminin 5
  5. Muscular dystrophy (congenital) - laminin 2
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19
Q

What is an example of a disorder resulting from ECM catabolism issues?

A

Hurler’s syndrome - L-α-iduronidase

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20
Q

What are 3 examples of disorders resulting from excess ECM deposition? (fibrosis)

A
  1. Liver cirrhosis
  2. Diabetic nephropathy
  3. IPF (idiopathic pulmonary fibrosis)
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21
Q

What does excess ECM deposition lead to?

A

Fibrosis

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22
Q

What is an example of a disorder resulting from loss of ECM?

A

Osteoarthritis

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23
Q

What are collagens?

A

Family of fibrous proteins

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24
Q

Which organs are collagens essential for?

A
  1. Bones
  2. Tendons
  3. Skin
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25
Q

What is the most abundant protein in mammals?

A

Collagen

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26
Q

What proportion of the protein mass of mammals is collagens?

A

25%

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27
Q

What is the arrangement of collagen fibrils in skin/bone/cornea and why?

A

Successive layers at right angles
- High tensile force

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28
Q

How many types of collagens exist in humans?

A

28

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29
Q

How many genes encode the collagens in humans?

A

42

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30
Q

What is the quaternary structure of a collagen molecule?

A

3 α-chains form triple helix

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31
Q

What is the quaternary structure of type I collagen?

A

2 α1-chains and 1 α2-chain

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32
Q

What are the 3 chains making up type I collagen molecules?

A

2 α1 + 1α2

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33
Q

What is the tertiary structure of type II and III collagen?

A

3 α1-chains

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34
Q

What is the primary structure of α collagen chains?

A

Repeated gly-x-y
- Usually glycine-proline-hydroxyproline

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35
Q

Why is fibrillar collagen described as a left-hand helix?

A

3 α-chains coils left (anti-clockwise)

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36
Q

Why must every 3rd amino acid in a collagen molecule be glycine?

A

Small enough to occupy interior of coil

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37
Q

What are the 4 stages of collagen fibre synthesis?

A
  1. α-chain
  2. 3 α-chains in triple helix
  3. Fibril
  4. Fibre
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38
Q

What is the difference between procollagen and collagen?

A

Procollagen has non-collagenous N- and C-termini

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39
Q

How is procollagen turned into collagen?

A

N- and C-termini removed
- Post-secretion in fibrillar collagens
- Pre-secretion in non-fibrillar

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40
Q

What forms between collagen fibres and why?

A

Cross-links (covalent)
- increases strength and stability

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41
Q

What are the 7 steps of collagen fibre biosynthesis?

A

ER/Golgi
1. Pro-α chain synthesised
2. Hydroxylation of prolines and lysines (post-translational modifications)
3. Glycosylation of hydroxylysines
4. 3 pro-α chains assemble —> triple helix —> procollagen
5. Procollagen to cytoplasm via secretory vesicle and exocytosis

ECM
6. Propeptides cleaved —> collagen
7. Fibril assembly
8. Fibre assembly

42
Q

Where does collagen fibre biosynthesis occur? (2)

A
  1. ER/Golgi —> procollagen
  2. ECM —> collagen fibre
43
Q

How do collagen cross-links change with age?

A

Number increases with age —> joint stiffness

44
Q

What do prolyl and lysyl hydroxylases require? (2)

A
  1. Fe2+
  2. Vitamin C
45
Q

Which enzymes are involved in post-translational modification of collagen?

A

Prolyl and lysyl hydroxylases

46
Q

What type of bonding in collagen do hydroxylysine and hydroxyproline contribute to?

A

H-bonding

47
Q

Which amino acids contribute to interchain H-bond formation in collagen?

A
  1. Hydroxylysine
  2. Hydroxyproline
48
Q

When is collagen lysine and hydroxylysine modified? (2)

A

Post-translation in golgi/ER

49
Q

What does vitamin C deficiency lead to and why?

A

Scurvy
- vit C needed for hydroxylases —> under-hydroxylated collagens —> decreased tissue stability

50
Q

What is EDS?

A

Ehlers-Danlos Syndrome
- Group of inherited connective tissue disorders

51
Q

What are the 2 symptoms of EDS?

A
  1. Stretchy skin
  2. Loose joints
52
Q

When do mutations in collagen result is disorders? (3)

A
  1. Change production
  2. Change structure
  3. Change processing
53
Q

What are the 3 types of collagen?

A
  1. Fibrillar (I, II, III)
  2. Fibril-associated (IX, XII)
  3. Network-forming (IV)
54
Q

What is the function of fibril-associated collagens?

A

Regulate organisation of collagen fibrils

55
Q

What are the 2 fibril-associated collagens?

A
  1. IX
  2. XII
56
Q

Where is network-forming collagen found?

A

Basement membranes

57
Q

What collagen is network-forming collagen?

A

IV

58
Q

What category of collagen is type I, II and III?

A

Fibrillar

59
Q

What category of collagen is type IV?

A

Network-forming

60
Q

What category of collagen is type IX and XII?

A

Fibril-associated

61
Q

What type of collagen is in basement membranes?

A

IV

62
Q

What can be seen in a fibrotic lung?

A

Honeycombing (excess collagen)

63
Q

What are basement membranes?

A

Membranes separating different tissue layers

64
Q

What happens to the glomerular basement membrane in diabetics?

A

Fibrosis —> thickened

65
Q

Why can diabetes lead to renal failure?

A

Glomerular basement membrane fibrosis —> inhibits renal filtration

66
Q

What is the cause of Alport syndrome and why?

A

Mutation in collagen IV —> split and laminated glomerular basement membrane

67
Q

What are laminins?

A

Family of large, multidomain glycoproteins

68
Q

What is the quaternary structure of laminins?

A

Coil of 1α, 1β and 1γ chain

69
Q

What can the the N- and C-termini of α chains in laminins bind to?

A
  • N —> integrins
  • C —> integrins, dystroglycan and perlecan
70
Q

What can the the N-terminus of β and γ chains in laminins bind to?

A

Nidogen

71
Q

Why do laminins have stability?

A

Heterotrimeric coil structure

72
Q

What is the distinctive shape of laminins?

A

Cross

73
Q

What is the cause of muscular dystrophy?

A

LAMA2 mutation —> laminin-α2 deficiency (truncated protein)

74
Q

What is a heterotrimer?

A

Complex consisting of 3 different sub-units
- eg. Laminins

75
Q

What does LAMA2 gene truncation cause and how?

A

Congenital muscular dystrophy
- lamanin can’t bind to integrin (α7β1) or α-dystroglycan —> inhibits basement membrane assembly

76
Q

What are the 2 symptoms of muscular dystrophy?

A
  1. Muscle weakness
  2. Muscle degeneration
77
Q

Why do tissues have elasticity?

A

Elastic fibres

78
Q

Where are elastic fibres found? (3)

A
  1. Skin
  2. Blood vessels
  3. Lungs
79
Q

What are elastic fibres made up of?

A
  1. Elastin core
  2. Surrounded by fibrillin-rich microfibrils
80
Q

What is the arrangement of elastin?

A

Random coil

81
Q

What are the 2 domains in elastin and how are they arranged?

A
  • Hydrophobic and hydrophilic
  • Alternating
82
Q

How does crosslinking occur in elastin?

A

Via lysine residues in the hydrophilic domains

83
Q

What is the cause of Marfan’s syndrome?

A

Fibrillin-1 mutations

84
Q

Which 3 systems are primarily effected by Marfan’s syndrome?

A
  1. Skeletal
  2. Ocular
  3. Cardiovascular
85
Q

Which blood vessel does Marfan’s syndrome affect and how?

A

Aorta
- Fragmentation
- Disarray of elastic fibres

86
Q

What is fibronectin?

A

Glycoprotein in ECM

87
Q

What are the 5 functions of fibronectin?

A
  1. Interact with cell surface receptors and ECM molecules
  2. Regulate cell adhesion
  3. Regulate tissue repair
  4. Wound healing and blood clotting
  5. Regulate migration in embryogenesis
88
Q

What is the structure of fibronectin?

A

2 sub-units linked by di-sulfide bridge at C-terminus

89
Q

What is the identifiable shape of fibronectin?

A

Omega symbol worm

90
Q

What do fibronectins link in cells and how?

A

Cytoskeleton to ECM
- Cell attachment sites to integrins on cell surface membrane —> integrins bind to actin filaments inside the cell
- N-terminus ends bind to collagen fibril in ECM

91
Q

What are proteoglycans?

A

Core proteins with attached glycosaminoglycan chains (GAG)

92
Q

What are GAG chains?

A

Glycosaminoglycan chains
- Polymer of repeating disaccharides

93
Q

What can affect the charge of proteoglycans and what does this do?

A

Sulfation and carboxylation
- attract more water and cations

94
Q

What are the 4 types GAG and where are they made?

A
  1. Hyaluronan - membrane
  2. Chondroitin/dermatan sulfate - ER/golgi
  3. Heparan sulfate - ER/golgi
  4. Keratan sulfate - ER/golgi
95
Q

Where is the proteoglycan hyaluronan found?

A

High viscous tissues
- eg. Fluid of eyes and joints

96
Q

What is the key function of the proteoglycan hyaluronan?

A

Protect cartilaginous

97
Q

What is the structure of hyaluronan?

A
  • No core protein
  • Cluster of saccharide chains
98
Q

Where is the proteoglycan aggrecan found and why?

A

Cartilage matrix
- Resist compressive forces

99
Q

How does the proteoglycan aggrecan resist compressive forces?

A

Lose water under compressive load —> gain water when load is reduced

100
Q

What is the leading cause of lower extremity disability in adults?

A

Osteoarthritis

101
Q

What is osteoarthritis?

A

ECM degradation at bone ends

102
Q

What is the cause of osteoarthritis?

A

Aggrecan cleaved by aggrecanases and metalloproteinases —> cartilage at end of bones no longer cushioning

1.1 POM Cells (15 decks)

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