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Molecular biology of the cell > 2.7 Extra cellular matrix > Flashcards

2.7 Extra cellular matrix Flashcards

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1
Q

What is an extra cellular matrix

A

complex network of proteins and carbohydrates filling spaces between cells
composed of fibrilar and non fibrilar parts

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2
Q

What are the key functions of the ECM (4)

A
  • provides physical support
  • determines mechanical and physiochemical properties of the tissue
  • influences the growth, adhesion and differentiation of the cells and tissues with which it interacts
  • essential for tissue function, organogenesis and development
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3
Q

Which collagens are fibrilar

A

1-3

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4
Q

Which collagen is used in the basement membrane

A

collagen 4

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5
Q

What are the 3 multi adhesive proteins

A

Laminins, fibrinogen and fibronectin

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6
Q

What are 4 proteoglycans

A

aggrecan
decorin
versican
perlecan

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7
Q

What is the ECM part that is disturbed in 1)osteogenesis imperfecta

2) Marfans syndrome
3) Alports syndrome
4) epidermolysis bullosa
5) congenital muscular dystrophy

A

1) Collagen 1 where cysteine is coded for
2) Fibrilin 1
3) Type 4 collagen
4) Laminin 5
5) Laminin 2

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8
Q

What are the symptoms of Alports syndrome

A

progressive loss of kidney function

hearing loss

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9
Q

What are the causes and symptoms of Marfans syndrome

A

problems in gene coding for fibrilin
spider like fingers
susceptible to aortic rupture

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10
Q

What is the arrangements of collagen fibrils in the skin, mature bone and cornea

A

Successive layers are at right angles to each other to resist tensile force

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11
Q

What type of collagen is a heterotrimer

A

collagen 1

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12
Q

What is the i) characteristic repeat in collagen and 2) what secondary structure does this lead to

A

i) gly -x - y with x and y often being proline and hydroxyproline
ii) glycine is small enough to occupy the interior space and so forms a left handed helix

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13
Q

What are non collegenous domains and in which cases are they removed

A

All newly synthesized collagen chains have non collengenous domains at the N and C terminals

In fibrilar collagen, they are removed after secretion but not so in non fibrilar collagen

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14
Q

What are the 9 stages of collagen assembly (and where do they happen )

A

1) formation of pro alpha chain ( in ER/ golgi)
2) hydroxylation of proline/lysine ( in ER/ golgi)
3) Glycosylation (of hydroxlysine in ER/ golgi)
4) self assembly of pro alpha chains ( in ER/ golgi)
5) procollagen triple helix formation ( in ER/ golgi)
6) secretion (in secretory vesicle)
7) Cleavage of propeptides (forming a collagen molecule )
8) self assembly into fibrils (10- 300nm long )
9) self aggregation into fibres (0.5 to 3 micrometers long)

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15
Q

What are the 2 types of cross linking formed

A

1) intermolecular - between hydroxyl and carboxyl group

2) intramolecular - between collagen molecules

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16
Q

How does hydroxylation happen

A

lysine and proline can by hydroxylated by lysyl and prolyl hydroxylases which require vitamin C and Fe2+ as co factors
which contributes to interchain hydrogen bond formation

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17
Q

What is scurvy

A

reduced vitamin c intake
reduced hydroxylation of proline and lysine ( as vitamin C is a co factor )
reduced tissue stability

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18
Q

What is Ehlers Dahl syndrome

A

group of inherited connective tissue disorders
symptoms are stretchy skin and loose joints
due to disorders that negatively effect:
collagen production
collagen structure
collagen processing

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19
Q

What do collagens 9 and 12 do

A

regulate the organisation of collagen fibrils

20
Q

how do collagen 4 organise

A

sheets that form network that is called a basement membrane

21
Q

What are the 4 stages of collagen molecule assembly

A

1) have a monomer with a collagenous and non collagenous end
2) non collogenous ends attach to form a dimer
3) a tetramer is former
4) a supramolecular aggregate is formed

22
Q

What is diabetic nephropathy

A

Accumulation of ECM leading to a highly thickened basement membrane
restricts renal filtration and can cause renal failure

23
Q

What disorder can arise from fibrilin

A

Disorders of fibrilin 1 lead to marfans leading to :

1) increased susceptibility to aortic rupture
2) spider like fingers

24
Q

what is collagen important for

A

high tensile strength

25
Q

What are elastic fibres made of

A

microfibrils, elastin and fibrilin

26
Q

how is stretching reduced

A

collagen and elastic fibres are interwoven

27
Q

What are some features of laminins

A
  • multi adhesive proteins
  • form a ‘cross like structure’
  • can bind to dystroglycan, perlecan and integrins
  • has alpha, beta and gamma sub units
  • can self associate
  • can interact with other matrix components such as type 4 collagen, nidogen and proteogylcans
28
Q

What problems can laminin defects cause and what are their symptoms (2)

A

1) muscular dystrophy
symptoms: hypotonia ( decreased muscle tension ), generalised weakness and deformities of the joints
Arises from lack of a2 chain in laminin 2
2) epidermolysis bullosa

29
Q

What are some features of fibronectins

A
  • multi adhesive proteins
  • insoluble extra cellular matrix or soluble plasma protein
  • in some cells is continous with the mechanical actin cytoskeleton
  • can bind to collagen, heparin and integrins
  • can join ligands to cell receptors ( eg collagen can bind to fibronectin which binds to integrins on the cell surface membrane )
  • play roles in cell adhesion, migration and formation of blood clots
30
Q

What are proteoglycans

A

core proteins attached to 1 or 2 glycosaminoglycan side chains
GAGs are formed of repeating disaccharide units with one of the 2 being an amino sugar
many GAGs are carboxylated or sulfated and so have a high negative charge which attracts Na+ and so water too

31
Q

Give an example of a basement membrane proteoglycan

A

perlecan

32
Q

Give an example of a small leucine rich proteoglycan and the GAG side chain its associated with

A

Decorin and D ermatan sulfate

33
Q

Give an example of a cell surface proteoglycan and the GAG associated with it

A

syndecans 1-4

heparan sulfate

34
Q

aggregating proteoglycans and the GAG associated with it

A

aggrecan

hylonuran, keratan sulfate and chondroitin sulfate

35
Q

What is cartilage

A

collagen +GAGs trapped in the mesh

36
Q

What are the 4 types of GAG chains

A

hyaluronan
chondroitin and dermatan sulfate
heparan sulfate
keratan sulfate

37
Q

what is the repeating disaccharide unit in hyulauronan

A

glucuronic acid

N acetyl glucosamine

38
Q

why can hyulauronan chains have a high volume

A

high degree of polymerisation - in the range of 10,000 disaccharides

39
Q

Where can hyulauronan be found

A

vitreous humour of eyes

synovial fluid of joints

40
Q

what role does hyulauronan play in the synovial fluid of joints

A

protects cartilagenous surface from damage

41
Q

How is hyulauronan spun out

A

directly from an enzyme embedded in the plasma membrane

42
Q

What is osteoporosis

A

with age, aggrecanases and metalloporinases cleave aggrecan, disturbing its cushioning properties

43
Q

how do fibrotic diseases occur

A

excessive production of fibrous ECM

44
Q

Mutations in the protein fibrillin-1 are associated with Marfan’s syndrome which has diverse manifestations. Whare are some potential features of Marfan’s syndrome

A

Tall and slender build
Spider like fingers
susceptibility to aortic rupture

45
Q

What properties of the molecule aggrecan means it can resist large compressive forces

A

highly negative charge due to sulfates (chondroitin and keratan sulfate) and carboyxl group means attracts Na+ which attracts water, acting as a cushion

Molecular biology of the cell (8 decks)

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