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POM| Molecular Biology of The Cell > Extracellular Matrix > Flashcards

Extracellular Matrix Flashcards

1
Q

What does ECM consist of?

A

Both fibrillar and non-fibrillar components - proteins and carbohydrates filling spaces between cells

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2
Q

What are the key functions of ECM?

A
  • Provides physical support
  • Determines the mechanical and physicochemical properties of the tissue
  • Influences the growth, adhesion and differentiation status of cells
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3
Q

Which tissue is composed of ECM+component cells?

A

Connective tissue

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4
Q

Which collagens are components of connective tissue?

A

Types I, II, III (fibrillar)
Type IV (basement membrane)

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5
Q

Which glycoproteins are components of connective tissue?

A

Fibronectin
Fibrinogen
Laminins (basement membrane)

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6
Q

Which proteoglycans are components of connective tissue?

A

Aggrecan
Versican
Decorin
Perlecan (basement membrane)

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7
Q

What are the properties of connective tissue in the form of tendon and skin?

A

Tough but flexible

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8
Q

What are the properties of connective tissue in the form of bone?

A

Hard and dense

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9
Q

What are the properties of connective tissue in the form of cartilage?

A

Resilient and shock-absorbing

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10
Q

How do different types of connective tissue have different properties?

A

Different types and arrangements of oxygen

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11
Q

List the genetic disorders affecting ECM proteins

A

Osteogenesis imperfecta (OI)
Marfan’s syndrome
Alport’s syndrome
Epidermolysis bulllosa
Congenital muscular dystrophy (CMD)

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12
Q

What is a genetic disorder affecting ECM catabolism?

A

Hurler’s syndrome

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13
Q

Which ECM component is affected in OI?

A

Type I collagen

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14
Q

Which ECM component is affected in Marfan’s syndrome?

A

Fibrillin-1

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15
Q

Which ECM component is affected in Alport’s syndrome?

A

Type IV collagen (α5 chain)

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16
Q

Which ECM component is affected in Epidermolysis bullosa?

A

Laminin 5 (in all 3 chains)

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17
Q

Which ECM component is affected in CMD?

A

Laminin 2 (α2 chain)

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18
Q

Which genetic disorder disrupts the function of L-α-iduronidase?

A

Hurler’s syndrome

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19
Q

Identify the fibrotic disorders due to excessive ECM deposition?

A

Liver fibrosis - cirrhosis
Kidney fibrosis - diabetic nephropathy
Lung fibrosis - idiopathic pulmonary fibrosis (IPF)

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20
Q

What causes osteoarthritis?

A

excessive loss of ECM

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21
Q

What is a disorder caused by excessive loss of ECM

A

osteoarthritis

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22
Q

Which group of proteins are most abundant in mammals?

A

Collagens - 25% of total protein mass

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23
Q

How are collagen fibrils aligned in skin?

A

successive layers nearly at right angles to each other

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24
Q

How many collagen types are there in humans?

A

28 types

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25
Q

How many genes code for different types of collagens?

A

42 genes

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26
Q

How many α chains are in a collagen?

A

3 α chains forming a triple helix

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27
Q

What’s the composition of Type I collagen?

A

Type I

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28
Q

What’s the composition of Type II collagen?

A

Type II

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29
Q

What’s the composition of Type III collagen?

A

Type III

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30
Q

What is the amino acid pattern of an α chain?

A

x-y-glycine
(usually x=proline and y=hydroxyproline)

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31
Q

How long is each α chain in fibrillar collagens?

A

Approx 1000 amino acids

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32
Q

What are added to the newly synthesised collagen chains?

A

non-collagenous domains at N- and C-termini

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33
Q

When are the propeptides on N and C termini removed from the collagen?

A

after secretion in the case of fibrillar collagens (they remain part of the collagen in most other types)

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34
Q

What are some post-translational modifications of α helices?

A
  • Hydroxylation of prolines and lysines
  • Glycosylation of hydroxylysines
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35
Q

What happens to the α helices after modifications?

A

Self-assembly of three α chains

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36
Q

Which organelles carry out the synthesis, modification and secretion of α helices?

A

ER and Golgi

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37
Q

What type of links are made between collagens and inside collagen?

A

inter- and intra-molecular covalent cross-links

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38
Q

Which amino acids are involved in crosslinks (collagen)?

A

Lysine and hydroxylysine

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39
Q

Which molecules (cofactors) are required for hydroxylation of proline and lysine?

A

Iron (II) - Fe2+
Vitamin C

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40
Q

What type of bonding does hydroxylation aid?

A

(Interchain) H bonding

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41
Q

What is the result of Vitamin C deficiency (biochemical and tissue stability-wise)?

A

Under-hydroxylation of collagens
Dramatically reduced tissue stability
Scurvy - swollen bleeding gums and reopened wounds

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42
Q

Name the syndrome that is a spectrum of inherited connective tissue disorders

A

Ehlers-Danlos syndrome (EDS)

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43
Q

What are the common symptoms of EDS?

A

Stretchy skin and loose joints

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44
Q

What are the 3 main parts of collagen cycle affected by genetic mutations in EDS?

A
  • Collagen production
  • Collagen structure
  • Collagen processing
45
Q

Which types are fibril-associated collagens?

A

Types IX and XII

46
Q

What are fibril-associated collagens?

A

Collagens regulating the organisation of collagen fibrils (but not forming fibrils themselves)

47
Q

Wich type is a network-forming collagen and is found in all basement membranes?

A

Type IV

48
Q

Which type of collagens doesn’t undergo cleavage and interact using N,C-terminal polypeptides?

A

Type IV

49
Q

What is rotary shadowing?

A

A technique used in electron microscopy to study the three-dimensional structure of biological molecules

50
Q

What is the network of collagens formed in the basement membrane (Type IV) called?

A

Supramolecular aggregate

51
Q

What is the result of excessive production of fibrous connective tissue?

A

Fibrotic disorders

52
Q

Why does the amino acid glycine feature so frequently in the primary sequence of a collagen chain?

A

Its small sidechain occupies the interior of the triple helix, allowing for tight packing

53
Q

What is the diagnosis here, given that this is liver?

A

Fibrotic liver → cirrhosis

54
Q

What causes diabetic nephropathy?

A

Accumulation of excessive ECM leading to a thickened glomerular basement membrane (GBM) in the glomerulus

55
Q

What happens as a result of thickened GBM in diabetic nephropathy?

A

Restricted renal filtration potentially leading to renal failure

56
Q

How to identify a fibrotic lung from normal lung?

A

Large areas of honeycombing

57
Q

What is obesrved in stained slices of fibrotic lung?

A

Excessive blue staining due to increased collagen production

58
Q

What happens on a moleculer level in Alport syndrome?

A

Mutations in collagen IV → abnormally split and laminated GBM → progressive loss of kidney function

59
Q

What are the observations from pathological slides for Alport syndrome?

A

Basement membrane not intact/abnormally split

60
Q

What is the basal lamina made up of (collagen and glycoprotein components)?

A

Collagen IV and Laminin

61
Q

What are laminins made up of?

A

Heterotrimeric protein:
α, β, γ chains in cross shaped arrangement

62
Q

How many laminin variant are there?

A

genome codes for 5α, 3β, 3γ chains
giving rise to 16 variants

63
Q

What do the N-termini of laminin associate with?

A

Self-assemnly
Integrins
Nidogens
Collagen IV

64
Q

How many N-termini are present in a laminin?

A

3 N-termini

65
Q

What does the C terminus of laminin associate with?

A

Cell surface receptors (i.e. integrins)
Dystroglycan
Perlecan

66
Q

What is regulated via the C-terminus associations of laminin?

A

Cell adhesion

67
Q

What is the gene coding for laminin-α2 chain?

A

LAMA2

68
Q

Which laminin variant forms a trimer with laminin-α2 chain?

A

laminin-211
α2, β1, γ1

69
Q

What does laminin-211 associate with?

A

α7β1 integrin and α-dystroglycan
for adhesion and basal membrane assembly (in muscles)

70
Q

What is deficient in CMD?

A

LAMA2

71
Q

What is the result of LAMA2 deficiency?

A

no laminin-α2 → no laminin-211 → no integrin or dystroglycan association → basal lamina disrupted → progressive muscle weakness and degeneration

72
Q

What is the role of elastic fibers?

A

Provide elasticity to tissues

73
Q

Where are elastic fibres found?

A

Found in skin, blood vessels, and lungs

74
Q

What are elastic fibres composed of?

A

An elastin core and surrounding microfibrils rich in the protein fibrillin

75
Q

What is a small protein of around 2 kDa arranged in a random coil?

A

Elastin

76
Q

What are the domains of elastin?

A

Alternating hydrophilic and hydrophobic domains

77
Q

What happens during the formation of mature elastin?

A

Lysine residues in hydrophilic domain are crosslinked

78
Q

Which parts of the body are manifested in Marfan’s syndrome?

A

Skeletal, ocular and cardiovascular

79
Q

Which genetic disorder is related with abnormal thickening of the aorta?

A

Marfan’s syndrome

80
Q

What is the major physiological finding in people with Marfan’s syndrome?

A

Abnormal thickening of the aorta

81
Q

What causes the abnormal thickening of the aorta in Marfan’s syndrome?

A

Fibrillin-1 mutations → Fragmentation and disarray of elastic fibres → thickening of the aorta

82
Q

What is the anticipated fatal risk of Marfan’s syndrome?

A

Individuals can be predisposed to aortic ruptures

83
Q

Which ECM protein is a 500kD dimer which is disulphide linked?

A

Fibronectin

84
Q

What interactions does fibronectin have?

A

Cell surface receptors:
- integrins
- heparins
Collagen binding

85
Q

What are the roles of fibronectin?

A

Regulate cell adhesion
Migration in embryogenesis
Tissue repair
Promoting coagulation

86
Q

What is the association between actin and fibronectin?

A

Fibronectins link
ECM and actin cytoskeleton (through integrins)

87
Q

What are proteoglycans made up of?

A

Glycosamineglycans (GAG) attached to a core protein

88
Q

What are GAG chains made up of?

A

Repeating disaccharides
(one of two sugars includes amine groups)

89
Q

What is observed in microscopic slide of aortic tissue in Marfan’s syndrome?

A

larger diameter - thickening
disaarray of elastic fibers

90
Q

What are the two forms of fibronectins?

A

Insoluble in ECM
Soluble plasma proteins

91
Q

How are the charge of GAG chains modified?

A

Through sulfation or carboxylation to increase the (negativity of) charge

92
Q

Why is the negative charge of GAG chains important?

A

It attracts cations such as Na+ which draws a significant aamount of water into the ECM

93
Q

What are the 4 main varieties of GAG chains?

A
  • Hyaluronan
  • Chondroitin/Dermatan sulfate
  • Heparan sulfate
  • Keratan sulfate
94
Q

Which GAG chain is found in decorin?

A

Dermatan sulfate (DS)

95
Q

Which GAG chain is found in snydecan?

A

Hepaaran sulfate (HS)

96
Q

Which GAG chains are found in aggrecan?

A

Keratan sulfate (KS) and Chondroitin sulfate (CS)

97
Q

Which GAG chain is different than others in terms of its components as a proteoglycan?

A

Hyaluronan - it is not attached to a core protein and it is unsulfated

98
Q

Where is hyaluronan found in the body?

A

Highly viscous tissues - vitreous humour of the eye and synovial fluid of joints

99
Q

What is the role of hyaluronan?

A

Protecting the cartilaginous surface from damage

99
Q

Which proteoglycan is a major constituent of cartilage?

A

Aggrecan

100
Q

Where is aggrecan located and what does it do there?

A

Located in the cartilage matrix being perfectly suited to resist compressive forces

101
Q

What are the 2 proteoglycans protecting cartilage from damage?

A

Aggrecan and Hyaluronan

102
Q

Which property of aggrecan allows it to resist compressions?

A

Highly sulfated GAG chains increasing the negative charge → Osmatically active cations are attracted → Drawing water to the site → Water is given up under compressive load to increase tensile strength

103
Q

Which disorder is the leading leading cause of lower extremity disability in older adults?

A

Osteoarthritis (OA)

104
Q

What is lost in OA?

A

ECM is lost via degradation - cartilage damage

105
Q

What happens to the proteoglycans in OA?

A

Aggrecan cleavage by aggrecanases and metalloproteinases

106
Q

Which property of cartilage is lost?

A

Cushioning properties of cartilage over the end of bones are lost

107
Q

What are integrins?

A

Cell surface receptors that bind to ECM molecules

POM| Molecular Biology of The Cell (10 decks)

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