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FunMed Week 2 > Molecules for Life - Extracellular Matrix and Cell Adhesion > Flashcards

Molecules for Life - Extracellular Matrix and Cell Adhesion Flashcards

1
Q

what does integrin do?

A

it is a adhesion protein, found in lipid bilayer of cells. helps to hold up the cell on the ECM

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2
Q

what is ecm made from?

A

network of secreted macromolecules:

  1. fibrous proteins
  2. glycosaminoglycans
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3
Q

how would you describe the ecm? (

A

hydrated, jelly like environment

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4
Q

what do actin filaments do?

A

found in cytoplasm, part of cytoskeleton:

  1. cause the cell to be held in place
  2. structural support
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5
Q

what is the role of the ecm?

A
  1. provides a 3D framework for the organisation of tissues
  2. regulates:
    a) proliferation
    b) differentiation
    c) migration
    e) cell to cell interaction
  3. adhesion - linkage between cells and matrix
  4. provides structure
  5. presents growth factors to their receptors
  6. sequesters and stores growth factors
  7. sense and tranduces mechanical signals
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6
Q

how does ecm provide structure?

A
  1. defines tissue boundaries between different cell types
  2. provides integrity and elasticity to developing organs
  3. degraded by invasive cells during development and disease
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7
Q

can you give two examples of when cells migrate?

A
  1. embryo development
  2. cancer development
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8
Q

how does ECM work to be an adhesive substrate?

A

gives linkage between cell and the matrix

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9
Q

how does cell whether to respond to stress because of ECM?

A

ECM is attached to the cell. therefore as the ECM stretches or is spoiled - cell will sense that is stressed and will respond

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10
Q

name main components of ecm (4)

A

cells produce an extracellular, excreted macromolecular network of:

  1. collagens
  2. elastin
  3. glycoproteins
  4. proteoglycans
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11
Q

where do the cells produce the macrocmolecular network?

A

outside of the cell - gives them a home

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12
Q

the macromolecules form what sort of env for the cell?

A

3D gelatinous bed

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13
Q
A
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14
Q

what do changes in ECM characteristics show?

A

associated with chronic diseases

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15
Q

what is fibrosis?

A

when too much ECM made and is tough

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16
Q

which is the most common protein in ECM?
how much is this protein of the body?

A

collagen
25% of total protein in body

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17
Q

how many different types of collagen are there?

A

25 ID so far

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18
Q

what is role of collagen?

how many types of collagen?

A
  • primary structural component in connective tissue and architecture /integrity.
  • mediates cell to cell and cell to matrix interactions
  • 25 types of collagen (distinct peptide chains)
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19
Q

what is structure of collagen?

A

- every 3rd amino is glycine (Gly). as Gly is small, it means that collagen can fit into crowded core. Gly-X-Y (often proline-hydroxyproline)

  • 3 peptide chains of collagen wind together = triple helical structutre -> tight rope like structure -> collagen fibrils -> collagen fibres
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20
Q

what are X-Y usually in Gly-X-Y?

A

X-proline
Y- hydroproline

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21
Q

larger structure of collagen looks like?

A

tight rope structure - collagen fibrils

all collagen fibrils together - collagen fibres

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22
Q

how can you divide types of collagen?

A

fibrillar - fibril forming. Type I, II…
non-fibrillary - type IV, VI..

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23
Q

describe structure of fibrillar and what that means its function is

A

forms well-organised banded fibrils, with provide high tensile strength. therefore is used for major components in tendons, ligaments, skin etc

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24
Q

describe structure of non-fibrillar collagen and what that means its function is

A

forms microfibrils or mesh-like structures.

therefore is used for anchorage of cells and filtration

e.g. major structural components of basement membranes - relatively thin layers of ECM

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25
Q

what is Osteogenesis imperfecta?

A

brittle bone disorder

26
Q

how is Osteogenesis imperfecta formed?

A

in type 1 collagen:

single base mutations cause Gly to convert to bulky amino acid. this prevents the corrected triple helix formation of collagen into fibrils. therefore is loose triple helix

27
Q

what is Osteogenesis imperfecta characterised by/

A

fragile bones, thin skin, abnormal teeth, thin sclera (so look blue) and weak tendons

28
Q

what are the two types ofOsteogenesis imperfecta?

A

Type 1:

a) autosomal dominant
b) most common - 50% of cases
c) mildest type
d) COL1A1 & A2 genes are mutated on chr. 17 and 7 respectively. causes an amino acid change - looser collagen chain and looser triple helix.

Type 2:

  • more severe - babies born with so many broken bones they die.
  • usually new mutation
  • dominant if affected individuals survive
29
Q

what is other main protein ECM (apart from collagen)

A

elastin - the predominant protein of elastic fibres

30
Q

what is structure of elastin like?

A
  • rich in glycine and proline - like collagen, but has more valine which interacts with hydrophobic domains, therefore makes it elastic.
  • elastin fibres are normally covered by the g_lycoprotein fibrillin._
  • can stretch in 2D.
  • when in relaxed state, fibres are jumbled. when stretch - stretches out and gives flex.

-

31
Q

give examples of where elastin is used

A

gives flexibility required for blood vessels, lungs, ligaments and skin

32
Q

how many more times stretchy is elastin than collagen? what does mean with structure

A

1000x more. therefore is covered by fibrillin - gives more structure and defined boundary. allows to stretch without breaking

33
Q

what is Marfan syndrome?

A
  • rare genetic disease (1/10000)
  • fibrillin protein is mutated and usually absent:

characteristics:
tall stature, long arms and legs, arachnodactyly (spider fingers), loose joints, floppy cardiac valves, eye problems, aortic aneurysms

34
Q

what is another role of elastin?

A

modulates binding and sequesters growth factors:
- controls amount of TGF - Beta.

35
Q

what does TGF - Beta do?

A

stimulates growth of collagen, if ECM is damaged TGF - Beta indudes fibroblast to make new protein and repair damage.

BUT - have LTBP-1: keeps the TGF-Beta locked away and out of ECM when not needed. controls how much TGF-Beta is in ECM.

36
Q

what happens in Marfan syndrome?

A

TFG-Beta is not bound with ECM.

37
Q

what is structure of glycoprotein?

A

polypeptide chain with oligosaccharide unit on the end

38
Q

what are roles of glycoproteins in ECM?

A

receptors of cell surfaces for:
- bacteria, viruses and toxins. START immune response

hormones

strength and support to ECM

slime layer of bacteria and flagella

39
Q

what do glycoproteins do with water?

A

attract water - produce mucous around cells which means that protects them from damage

40
Q

name two glycoproteins in ECM

A

laminin and fibronectin

41
Q

role of laminin in ECM?

A

cell adhesion to the ECM.

cell migration

cytoskeleton organisation
.

42
Q

e.g. of laminin working?

A

in basement membrane (mesh of collagen). glycoprotein gives attachment to epithelial cell.

43
Q

role of fibronectin?

A

cell adhesion to the ECM.

cell migration

cell shape

cell differentiation

cytoskeleton organisation

44
Q

how do glycoproteins work to allow cell migration?

A

if cell adhesion molecule is broken down then it gives the cell the ability to move and find new home

45
Q

what are proteoglycans?

A

peptide chain with covalently bound sugars. - mainly made of GAGs (glycosaminoglycans)

95% carb, 5% protein

gel forming components of ECM.

46
Q

how do proteoglycans attract water?

A

GAG side chains have sulphate group - gives a negative charge. this attracts water and so water moves into ECM

47
Q

where and how do you find proteoglycans?

A

is most cells, they aggregate. form centipede like structure. (core protein and side sugar chains).

this means that gives compressive strength to tissues due to jelly like matrix formed by proteoglycans.

48
Q

how do proteoglycans change with age?

A

decrease with age

  • shorter core and fewer side chains
  • draw and hold less water in tissue
  • more likely to be damaged

e.g. in vertebral discs lose water - THIS IS WHY YOU GET SMALLER IN AGE

49
Q

proteoglycans are important in …. process, How?

A

healing process:

  • normally proteoglycans are up-regulated when tissue is damaged.
  • causes initial swelling
  • this causes more nutrients and growth factors
50
Q

how can cell adhesion occur?

A
  1. direct contact between cell surfaces
  2. indirect contact - cells attach to ECM
51
Q

what can cell adhesion regulate?

A

signal transduction for cells to detect and respond to changes in env

cell migration and tissue development

52
Q

how does cell adhesion work?

A

interaction of cell adhesion molecules (CAM). transmembrane proteins found on cell surface

53
Q

which protein families can CAMs belong to?

A
  1. cadherins
  2. Ig super family
  3. mucins
  4. selectins
  5. integrins
54
Q

which CAMS are homophilic and which are heterophilic?

A

HOMO: cadherins and Ig superfamily

HETERO: mucins, selectin, integrins

55
Q

what is the basic principe for cell migration?

A

ON FLAT / 2D SUBSTRATE

  1. polymerization of actin filaments at leading edge gives a protrusive force. EXTENSION
  2. new adhesions are linked to network of actin filaments ADHESION.
  3. combined activity of retrograde actin movment and contractile forces produced by stress forward generates tension to ull cell forward TRANSLOCATION

4 forces produced by contractile network combined with actin filament and dissaembly help to tract trailing cell edge DE-ADHESION

56
Q

how does cell migration occur if substrate is 3D?

A

amoeboid movement, e.g in fibrillar ECM

57
Q

70% of white blood cells are ? where found?

A

neutrophils - in blood.

58
Q

what happens if infection occurs with regards to neutrophils?

A

extravasation - have to get from blood into cells

59
Q

how does extravasation occur?

A

on surface have modified glycoprotein. have integrin CAM. when signalled - they attach to selectin (CAM).
integrin goes into high affinity state - makes a stable attachment.

white blood cells can then push through basement membrane and the endothelial cell using AMOEBOID movement.

60
Q

what can cancer cells do. (GO OVER LECTURE FOR THIS).

A

cleavage of cell-adhesion molecules

degrdation of ECM allows invasive cells to migrate into surrounding tissue

activation of cytokines, increases cell migration and metastasis

61
Q

how does cancer metasasis occur?

A

normal epithelial cell attached to basement membrane - but isolated from ECM. epithelial to mesenchymal transition (EMT), induces transcription factors

loss of cell adhesion and loss of apoptosis but get uncontrolled proliferation

basement membrane breaks down and get cancer cells through

62
Q

describe structure of fibrillar collagen and function?

A

forms well organised fibrils

  • high tensile strength
  • major components in ligaments and tendons

FunMed Week 2 (10 decks)

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