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My MCD- Tissues > Lecture 6- Extracellular Matrix II > Flashcards

Lecture 6- Extracellular Matrix II Flashcards

1
Q

Describe the general properties of ECM proteins

A
  • LARGE
  • MODULAR structure: made of protein domains –> MULIFUNCTIONAL
  • MULT- ADHESIVE- bind matrix components and cell-surface receptors
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2
Q

What are laminins?

A

Basement membrane glycoproteins

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3
Q

Descibe the structure of laminins

A
  • made of three chains: alpha, beta, gamma which form a cross-shape molecule
  • Very Large
  • Multi-adhesive
  • Interact with surface receptors e.g. integrins, dystroglycan
  • Can self-associate (in BM matrix) or associate with collagens and proteoglycans
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4
Q

Mutations in laminin can cause which disorders?

A
  • Muscular dystrophy

- epidermolysis bullosa

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5
Q

Draw and label a molecule of laminin

A

1) Globular ends on alpha chain
2) Coiled-coil Domain
3) Self- assembly region- binds to other laminins
4) Integrin binding at tips of alpha chains and perlecan at bottom

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6
Q

What causes congenital muscular dystrophy? Describe some of its features

A
  • absence of a2 in laminin 2
  • symptoms visible from birth
  • Hypotonia (decreased muscle tension)
  • Generalised weakness
  • deformities of the joints
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7
Q

What is fibronectin?

A
  • connective tissue glycoprotein
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8
Q

Which two forms can fibronectin exist as?

A
  • insoluble fibrillar matrix
  • soluble plasma protein
  • both derived from the same gene
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9
Q

Describe its molecular structure and some of its features

A
  • Multi- adhesive
  • Large multi domain molecule
  • Interacts with cell surface receptors and other matrix molecules
  • forms a dimer linked by sulphide bridges
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10
Q

State three of the roles of fibronectin

A

1) Cell adhesion and migration in embryogenesis and tissue repair
2) Wound healing, promotes blood clotting
3) Forms mechanical continuum with actin cytoskeleton

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11
Q

How does fibronectin link to the actin cytoskeleton?

A

Fibronectin — integrin — Actin

Integris integrate the extracellular and intracellular environments

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12
Q

Briefly online the structure of proteoglycans

A
  • Core protein covalently bonded to one or more glycosaminoglycan chains
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13
Q

Describe the structure of GAGs

A
  • GAGs = long, unbranched sugars made of repeating disaccharides
  • one sugar is always an amino sugar
  • may be sulphated or carboxylated
  • Highle -vely charged
  • occupy huge volume relative to mass –> hydrated gel resistant to compression
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14
Q

What are the 4 main groups of GAG chains and what do they depend on?

A
  • Hyaluronan
  • Chondroitin sulfate and dermatan sulfate
  • Heparin sulfate
  • Keratan sulfate

– depends on sugar types

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15
Q

Give three examples of proteoglycans and their associate GAG chain

A
  • Decorin: DS
  • Syndecan: HS
  • Aggrecan: KS and CS
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16
Q
  • Describe the structure of Hyaluronan

- Where is Hyaluronan synthesised?

A
  • Simple carbohydrate chain with no core protein (not a proteoglycan)
  • insulated
  • single long chain
  • Synthesised at cell surface, not ER/ Golgi
17
Q

How are GAG chains and core proteins linked?

A

By a link tetrasaccharide

18
Q

What are the monomers of Dermatan sulphate and Chondroitin sulphate?

A

Dermatan: Iduronic acid and N-acetylgalactosamine-4-sulfate
Chondroitin: Glucuronic acid and N-acetylgalactosamine-4-sulfate

19
Q

Describe the structure of decorin and its function

A
  • small proteoglycan
  • binds to collagen fibers
  • essential for fibre formation
  • No decorin= weak collagen fibres = fragile skin
20
Q

What is the most abundant type of cartilage and where is it found?

A

Hyaline cartilage

- nose, larynx, trachea, bronchi, ventral end of ribs, articular end of long bones

21
Q

What is hyaline cartilage mostly made of and what is its function?

A
  • aggrecans (which form aggregates with hyaluronans)

- cushion ends of long bones

22
Q

Draw and annotate a molecule of aggrecan

A

1) Chondroitin S. attachment region
2) Keratan s. attachment region below this
3) Hyaluronan binding region below
4) Attached to Hyaluronan
5) Link protein next to this

23
Q

Describe the GAGs associated with aggrecan and how they contribute to aggrecans properties

A
  • Highly sulfated and also carboxylated
  • Multiple negative charges from these attract cations e.g. Na+ which are osmotically active
  • Retains large amounts of water
  • When compressed water is given up, but reabsorbed when load is removed
  • -> good for cartilage
24
Q

What is osteoarthritis?

A
  • Excessive loss of ECM
  • cushioning properties of cartilage over long bones lost
  • Leads to rubbing of bones and joint stiffness
  • Cleavage of aggrecan by aggrecanase and metalloproteinase
  • Aggrecan fragments –> synovial fluid

STRONG GENETIC COMPONENT

25
Q

What are fibrotic disorders?

A
  • Excessive production of fibrous connective tissue (mainly collagen)
  • normal cells replaced by stif collagen matrix

USUALLY NON-GENETIC

My MCD- Tissues (10 decks)

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