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Principles of Medicine > Extracellular matrix > Flashcards

Extracellular matrix Flashcards

1
Q

What is the extracellular matrix

A

Complex network of proteins and carbohydrates filling spaces between cells

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2
Q

What are the key functions of extracellular matrix

A

Provides physical support

Determines the mechanical and physiological properties of the tissue

Influences growth, adhesion and differentiation status of cells and tissues

Essential for development, tissue function and organogenesis

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3
Q

What are the components of connective tissue

A

COLLAGEN: Type 1, 2, 3 (fibrillar), Type 4 (basement membrane)

MULTI-ADHESIVE GLYCOPROTEIN: fibronectin, fibrinogen, laminins (basement membrane)

PROTEOGLYCANS: aggrecan, versican, decorin, perlecan (basement membrane)

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4
Q

What are the varied proerties of connective tissues

A

Tendon and skin: tough and flexible

Bone: hard and dense

Cartilage: resililent and shock-absorbing

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5
Q

Epidermyolysis Bullosa

A

Laminin 5 (in all 3 chains)

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6
Q

Congenital Muscular Dystrophy

A

Laminin 2 (a2 chain)

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7
Q

Hurler’s syndrome

A

L-a-iduronidase (degrades GAGs)

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8
Q

What are some fibrotic disorders due to excessive ECM deposition

A

Liver fibrosis - cirrhosis

Kidney fibrosis - diabetic nephropathy

Lung fibrosis- idiopathic pulmonary fibrosis

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9
Q

What is a disorder due to excessive loss of ECM

A

oesteoarthritis

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10
Q

What percent mass of protein is collagen

A

25%

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11
Q

What is the aligment of collagen fibrils in different

A

SKIN: successive layers nearly at right angles to each other

MATURE BONE AND CORNEA: same arrangement

High tensile strength

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12
Q

How many genes are encoding collagens

A

42 genes

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13
Q

How are the helixes of collagen formed

A

Type 1 - heterotrimer (two alpha 1, one alpha 2)

Type 2 and 3 collagen - homotrimer (three alpha 1,2, three alpha 1,3)

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14
Q

Why is glycine used in the triple helix

A

Glycine is small enough to occupy the interior

gly - x - y

x normally proline

y normally hydroxyproline

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15
Q

Assembly of collasgen fibres

A
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16
Q

What are the non collagenous domains of procollagen cone

A

N terminal and C terminal

Removed after secretion out of cell

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17
Q

Why are crosslinking in collagen imporatn

A

Tensile strength and stability

Lysine and hydroxylysine residues are involved

Type and extent of crosslinking is tissue specific

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18
Q

What enzymes carry out post translation modification

A

prolyl and lysyl hydroxlases

require Fe2+ and vitamin C

19
Q

What is Ehlers-Danlos syndromes

A

Elastic skin

Hypermobile joints

Negatively affect collagen production, structure and processing

20
Q

What are fibril-associated collagens

A

Types 9 and 7 collagen which regulate the organisation of collagen fibrils

21
Q

What type of collagen is type 4

A

Network-forming collagen, present in all basement membranes

22
Q

How is collagen type 4 assemblied

A

N and C terminals not cleaved

Interact with each other

Disruption in the triple helix

23
Q

Where do basement membranes surround

A

Muscle, peripheral nerve and fat cells, most epithelia

24
Q

Diagram of kidney glomerulus

25
What happens in diabetic nephropathy
Accumulation of extracellular matrix leading to a highly thickened basement membrane
26
What happens in alport syndrome
Mutations in collagen 4 result in abnormally split and laminated GBM which is associated with a progressive loss of kidney functions
27
What are elastic fibres made up of
Protein elastin Microfibrils - rich in fibrillin
28
What is Marfan's syndrome
Mutations in fibrillin-1 Skeletal, ocular and cardiovascular systems Aortic ruptures Arachnodactyly (spider-like fingers)
29
What is the structure of elastin
Contains two types of segments that alternate along polypeptide chain hydrophobic regions and a helical regions rich in alanine and lysine Lysine side chains are covalently cross linked
30
What does modular architercture mean for ECM
Characteristic protein domains which are multi-adhesive
31
What is the structure of laminins
Made up of a chain, b chain and y chain Moelcular weight of between 160 and 400 kDa Multi-adhesive proteins which can interact with intergirns and dystroglycan Self-associate as part of BM matrix but also interact with other matrix components such as type 4 collagen, nidogen and proteoglycans
32
Congenital muscular dystrophy
Absence of a2 chain in laminin 2 Hypotonia (decreased muscle tension) General weakness Deformity of the joints
33
Facts about fibronectins
Family of closely related glycoproteins Exist as insoluble fibrillar matrix or as a soluble plasma protein Derived from a single gene 500kD dimer Regulate cell adhesion and migration - embrygenesis and tissue repair Important for wound healing to promot blood clotting Form a mechanical continuum with the actin cytoskeleton of many cell types
34
What do integrin receptors on fibronectins do
Provide linkage between matrix and cytoskeleton
35
What are proteoglycans
Core proteins which are covalently attached to one or more glycosaminoglycan (GAG) chains
36
What are GAG chains
Repeating disaccharide units where one sugar is an amino sugar Many GAGs are sulfated or carboxylated and carry a high negative charge which attract a cloud of cations including Na+ Results in water being sucked into extracellular matrix
37
What are the different types of proteoglycans
Basement membrane proteoglycans: perlecan Aggregating proteoglycans: aggrecan Small leucine-rich proteoglycans - decorin Cell surface proteoglycans - syndecans 1-4
38
What does cartilage contain
Matrix rich in collagen with large quantities of GAGs Balance of swelling pressure is negated by tension in the collagen fibres
39
How are GAG chains grouped
Based on repeating disaccharide unit Hylauronan - spun out directly from enzyme embedded in plasma membrane Condroitin sulfate and dermatan sulfate Heparan sulfate Keratan sulfate (synthesised in endoplasmic reticulum and golgi apparatus)
40
Facts about hyaluronan
Extracellular matrix of soft connective tissue Simply a carbohydrate chain without a core protien Unsulfated Can undergo a high degree polymerisation High viscosity - vitreous humour of eye and synovial fluid of joints, protection of cartilaginous surface
41
Facts about aggrecan
Major constituent of cartilage extracellular matrix GAGs are highly sulfated, large number of negatively carboxyl groups Na+ attracted which increases quantities of water Under compressive load, water is given up but regained once load is reduced
42
Facts about osteoarthritis
Erosive disease resulting in excessive extracellular matrix degradation Cushing properties of cartilage are lost Aggrecan is cleaved by aggrecanases and metalloproteinases which leads to loss of aggrecan fragements to synovial fluid
43
Alcoholic liver cirrhosis
Excessive blue staining
44
Fibrotic lung

Principles of Medicine (12 decks)

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