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MD2001 Week 5 > Cell Adhesion and the Extracellular Matrix > Flashcards

Cell Adhesion and the Extracellular Matrix Flashcards

1
Q

What does the connective tissue consist of?

A

Cells and extracellular matrix.

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2
Q

What does the ECM consist of?

A

Fibrillar proteins and hydrated gel of GAGs.

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3
Q

What are GAGs?

A

Glycosaminoglycans- maintain and support collagen, elastin and turgidity (bounce) in the cellular spaces and keep protein fibres in balance and proportion.

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4
Q

What are the cells in the connective tissue?

A

Fibroblasts, myofibroblasts, blood deriver, chondroblasts, osteoblasts and adipocytes.

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5
Q

What are the blood derived cells in connective tissue?

A

Mast cells, plasma cells and macrophages.

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6
Q

What are adipocytes?

A

White blood cells.

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7
Q

What do the fibrillar proteins in the ECM consist of?

A

Collagen, elastin, fibronectin and laminin.

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8
Q

What are the long chains of sugar in the ECM called?

A

Polysaccharides glycosaminoglycans GAG’s (in proteoglycans).

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9
Q

What do fibroblasts do?

A

Synthesise and secrete collagen, elastin and proteoglycans.

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10
Q

How is collagen formed?

A

Fibroblast, tropocollagen, enzyme catalysed cross-linking to make a fibril, builds periodic collagen fibrils.

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11
Q

What makes collagen secretion special?

A

Collagen is packaged into specialised (large) vesicles in the RER.

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12
Q

How is collagen secreted?

A

Collagen secretion occurs by exocytosis at specialised sites.

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13
Q

Where are collagen fibrils produced?

A

In a membrane tube called a fibripositor.

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14
Q

How are fibroblasts orientated?

A

Along the tendon direction in groups- collagen fibres.

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15
Q

What is the main driving force for the recoil of elastin?

A

Hydrophobic effect.

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16
Q

Where is elastin produced?

A

Made in fibroblasts and also smooth muscle cells and chondroblasts.

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17
Q

What are proteoglycans?

A

Assemblages of glycosaminoglycans and proteins.

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18
Q

How are proteoglycans related to the matrix?

A

Provides matrix support/cushioning/hydration.

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19
Q

What is another function of proteoglycans?

A

Glue-like function.

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20
Q

What do proteoglycans provide links between?

A

Links between proteins of ECM and EMC and cell surface.

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21
Q

What is the structure of GAGs?

A

Long chains of repeating disaccharide units. Highly charged (-ve) and highly hydrated.

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22
Q

What does GAGs stand for?

A

Glycosaminoglycans.

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23
Q

What initially links the ECM to intracellular cytoskeleton?

A

Collagen/proteoglycans.

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24
Q

How does collagen/proteoglycan link the ECM to the intracellular cytoskeleton?

A

They bind Fibronectin that links to integrins which themselves bind via Adaptors to the actin cytoskeleton.

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25
Q

What are the two functions of a myofibroblast?

A

Fibroblast-like and smooth muscle-like.

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26
Q

How is a myofibroblast “fibroblast-like”?

A

They secrete collagen.

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27
Q

How is a myofibroblast “smooth muscle-like”?

A

They synthesise actin, myosin and desmin.

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28
Q

How are myofibroblasts involved in tissue damage?

A

They: proliferate, secrete collagen, consolidate and contract.

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29
Q

How does myofibroblasts secreting collagen help with tissue damage?

A

Secreting collagen provides a scaffold.

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30
Q

How do myofibroblasts consolidate the damaged area?

A

By producing a fibrous scar.

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31
Q

How does contracting of myofibroblasts help with tissue damage?

A

It reduces the size of the damaged area; (express focal adhesions and smooth muscle actin).

32
Q

What is included in mast cell granules?

A

Content includes heparin and histamine.

33
Q

What is the function of plasma cells in the ECM?

A

Antibody production through the secretory pathway.

34
Q

What are the functions of macrophages in the ECM?

A

Ingesting Listeria bacteria/paramecium.

35
Q

What are the function of adipocytes?

A

Insulation, packing and as an energy store.

36
Q

Where in the body is there packing of adipocytes used?

A

In the eye.

37
Q

What do cell junctions/adhesion proteins link cells and their cytoskeleton to?

A

Other cells and to the ECM.

38
Q

What is the function of the tight junction?

A

Control passage of substances between cells.

39
Q

Is the tight junction polar?

A

Yes, this allows the junction to fence-off membrane lipids and proteins.

40
Q

What can tight junctions link to?

A

Actin cytoskeleton.

41
Q

In an adherens junction, what anchors actin filaments at the membrane?

A

Plaque

42
Q

How do adherens junctions compare to desmosomes?

A

They are not as dense as desmosomes.

43
Q

What are cadherins?

A

A type of cell adhesion molecule that is important in the formation of adherens junctions to bind cells with eachother.

44
Q

Are there different cadherins?

A

Yes, there are distinct cadherins that provide cell adhesion in different tissues

45
Q

What type of cadherin provides cell adhesion in the epithelia?

A

E-cadherin.

46
Q

Where does N-cadherin provide cell adhesion?

A

In neurons and in heart muscle.

47
Q

Where does P-cadherin provide cell adhesion?

A

In the placenta and in the epidermis.

48
Q

What type of cadherin provides cell adhesion in the endothelial cells?

A

VE-cadherin.

49
Q

What provides the link from different cadherins?

A

An anchor of catenin to actin.

50
Q

What is a desmosome?

A

A structure by which two adjacent cells are attached.

51
Q

What is a desmosome made of?

A

Formed from protein plaques in the cell membranes linked by filaments.

52
Q

What is the structure of the plaque of a desmosome?

A

Cytoplasmic dense plaque.

53
Q

What are the types of protein in the desmosome plaque?

A

Desmoplakin and plakoglobin proteins.

54
Q

What is the structure of the filaments in desmosomes?

A

Keratin filaments anchored to the cytoplasmic dense plaque.

55
Q

What is the function of a gap junction?

A

Communication and letting small molecules pass.

56
Q

What type of channel does a gap junction form?

A

A hydrophilic channel.

57
Q

What are focal adhesions?

A

They link the outside of the cell through transmembrane proteins with cytoskeleton.

58
Q

What are the transmembrane proteins categorised as in focal adhesions?

A

Integrins.

59
Q

What forms the cytoskeleton that is linked by focal adhesions?

A

Actin filaments.

60
Q

What do hemidesmosomes link?

A

The outside of the cell through transmembrane proteins with cytoskeleton.

61
Q

What else do hemidesmosomes link?

A

They link to laminin in the basement membrane.

62
Q

What are integrins?

A

Large family of proteins: bridges between cytosol and ECM.

63
Q

What causes Duchenne’s muscular dystrophy?

A

Gene mutation: absence of dystrophin due to premature termination of translation.

64
Q

What are the effects of muscular dystrophy?

A

Muscle wasting, muscle weakness and unable to walk by 12 years.

65
Q

What is PTC 124?

A

Experimental drug thought to override premature stop signal mutation to produce normal dystrophin.

66
Q

What is the first step of microinvasion of cancer?

A

Cells convert to “mesenchymal” cells and expression of cadherins reduced.

67
Q

What are invadipodia?

A

Actin-based protrusions.

68
Q

What is the function of invadipodia?

A

They aid microinvasion.

69
Q

What are MMPs when talking about microinvasion?

A

Metalloproteases.

70
Q

What happens after the secretion of metalloproteases in microinvasion?

A

The basement membrane is breached.

71
Q

What happens in microinvasion after the basement membrane is breached?

A

Invading tumours lead to cells expressing integrins.

72
Q

How does the increased expression of integrins in microinvasion affect cells?

A

It promotes interaction with ECM and non-epithelial cells during movement.

73
Q

What increases motility of tumour cells and decreases E-cadherin?

A

Autocrine motility factors from tumour.

74
Q

What promotes vascularisation in a tumour?

A

Angiogenesis factors.

75
Q

What is metastasis also known as?

A

Dissemination.

76
Q

Describe the formation of carcinoma through the transition from epithelial to mesenchymal cells?

A

Basement membrane begins intact

The micro invasive cells have protrusions called invadipodia which break the BM

The cells also increase metalloproteases which breakdown the BM

Integrin and cadherin expression is changed to reduce adhesion to other cells and ECM

Cells start to produce factors for angiogenesis and break off to metastasize

MD2001 Week 5 (10 decks)

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