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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

A
25
Q

What happens in diabetic nephropathy

A

Accumulation of extracellular matrix leading to a highly thickened basement membrane

26
Q

What happens in alport syndrome

A

Mutations in collagen 4 result in abnormally split and laminated GBM which is associated with a progressive loss of kidney functions

27
Q

What are elastic fibres made up of

A

Protein elastin

Microfibrils - rich in fibrillin

28
Q

What is Marfan’s syndrome

A

Mutations in fibrillin-1

Skeletal, ocular and cardiovascular systems

Aortic ruptures

Arachnodactyly (spider-like fingers)

29
Q

What is the structure of elastin

A

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
Q

What does modular architercture mean for ECM

A

Characteristic protein domains which are multi-adhesive

31
Q

What is the structure of laminins

A

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
Q

Congenital muscular dystrophy

A

Absence of a2 chain in laminin 2

Hypotonia (decreased muscle tension)

General weakness

Deformity of the joints

33
Q

Facts about fibronectins

A

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
Q

What do integrin receptors on fibronectins do

A

Provide linkage between matrix and cytoskeleton

35
Q

What are proteoglycans

A

Core proteins which are covalently attached to one or more glycosaminoglycan (GAG) chains

36
Q

What are GAG chains

A

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
Q

What are the different types of proteoglycans

A

Basement membrane proteoglycans: perlecan

Aggregating proteoglycans: aggrecan

Small leucine-rich proteoglycans - decorin

Cell surface proteoglycans - syndecans 1-4

38
Q

What does cartilage contain

A

Matrix rich in collagen with large quantities of GAGs

Balance of swelling pressure is negated by tension in the collagen fibres

39
Q

How are GAG chains grouped

A

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
Q

Facts about hyaluronan

A

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
Q

Facts about aggrecan

A

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
Q

Facts about osteoarthritis

A

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
Q

Alcoholic liver cirrhosis

A

Excessive blue staining

44
Q

Fibrotic lung

A

Principles of Medicine (12 decks)

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