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BIOL1013 > Cell-Cell interactions > Flashcards

Cell-Cell interactions Flashcards

1
Q

Name the 4 main categories of signalling and any sub-categories that are included

A
  1. Cytoplasmic connections between cells
  2. Cell-to-cell signals
  3. Cell-matrix
  4. Free diffusion of chemical signals between cells
  • Adjacent cells (paracrine/ synaptic)
  • Distant cells (endocrine)
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2
Q

Whats a juxtacrine signal?

A

Cell-to-cell contacts at the plasma membrane

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3
Q

Tell me about juxtacrine signals

A
  • Have to have physical contact between cells
  • signalling occurs at all cell-cell contact centres
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4
Q

In cell-cell contact, what happens at speciaised regions on the membrane and at non-specialised regions on the membrane ?

A

Specialised regions on the membrane

  • Signalling and tissue organisation and behaviour

Non-specialised regions on the membrane

  • Signalling and movement/ migration
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5
Q

What can cells have specialised regions for?

A

Cell-cell signals (desmosomes-tight junctions etc) in some cases

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6
Q

Name the cell adhesion molecules

Label which are the specialised contact cells

Label which are the non-specialised contact cells

Label which experience Homophilic interactions

Label which experience heterophilic interactions

A
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7
Q

What are the subtypes of cell-cell specialised junctions and their sub-sub types

A

1. cell-cell contacts at organised junctions

  • tight junctions (vertebrates)
  • Septate junctions (invertebrates)

2. Anchoring junctions

  • Adherence junctions-adhering protein’s present (actin attachment sites)
  • Desmosomes (intermediate filament attachment sites e.g. Keratin)

3. Communicating junctions

  • Gap junctions
  • Electrical synapses
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8
Q

Label the junctions of the epithelial cell

A
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9
Q

Whats a Functional syncytia?

A

Fused cells with multiple nuclei with intercellular cytoplasmic connections

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10
Q

What size molecules can diffuse through the limited size cytoplasmic pores ?

A

<1000 Da

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11
Q

What does the plasmodesmata between cells allow?

A

Electrical coupling from one cell to the other

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12
Q

The cell-cell gap junctions are made of what?

A

Homo and heteromeric made of connexin 4 pass proteins- 14 family members present either in singla gap junctions or in groups of thousands (e.g. cardiac intercalated discs)

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13
Q

Is the pores in cell-cell gap junctions regulatable ?

A

yes

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14
Q

What are the different types of connecting forms in cell-cell gap junctions ?

A
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15
Q

Can gap junctions be concentrated together?

A

yes

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16
Q

Tell me about the regulation of gap junctions?

A

The channels close at high Ca2+ concentrations and low pH, allowing regulation of the coupling of cells (stops apoptosis of one cell affecting those connected via gap junctions)

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17
Q

is phosphorylation reversable and regulated?

A

yes

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18
Q

Where does histidine and aspartate phosphorylation occur?

A

In plants and prokaryotes

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19
Q

What does phosphorylation cause a conformational change in?

A

Many enzymes and receptors causing activation or deactivation

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20
Q

What does the addition of a phosphate to a weakly polar R group such as serine/ threonine cause?

A

Turns a hydrophobic region into a hydrophilic/ charged region

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21
Q

what does conformational change allow?

A

substrate binding to occur at these regions

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22
Q

What two things can happen in cell signalling ?

A
  1. Either a cell surface receptor is a kinase which is activated by binding to its ligand
  2. A signal at the cell surface causes transmembrane proteins to cluster and bring binding parterns including kinase and their substrates together
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23
Q

What are kinase receptors activated by?

A

binding its ligand, dimerisation and autophosphorylation

24
Q

what do kinase receptors produce?

A

An amplifying signalling cascade

25
Q

What do non-kinase receptors lack?

A

catalytic domains

26
Q

How do non-kinase receptors signal?

A

By clustering bringing binding partners e.g. kinases and their substrates together

27
Q

What do tight junctions seperate?

A

Seperation of a lumen about an epithelium

28
Q

Whats the main role of tight junctions?

A

Tight junctions also compartmentalise the membrane as well as the surrounding of the cells

This means that concentrations can be different in the apical and basolateral membrane

29
Q

What transmembrane proteins can be found in tight junctions?

What do they form?

A
  • Occludin
  • Claudin

These form bands at the apex of the epithelial cells

They interact to form an impermeable seal

Act as signalling centres

Form homophilic interactions

30
Q

Tell me the functions of the tight junctions ?

A
  • Restricting apical/basolateral intramembrane diffusion
  • Regulating signal cascades (PKA)
  • Regulating gene expressions (transcription and mRNA processing) (ZONAB)
  • Gating paracellular permeability
31
Q

How do tight junctions maintain osmotic variance across epithelia?

A

By producing impermeable bonds between cells which limits the paracellular permeability

32
Q

Name 2 anchoring junctions which strengthen links between cells ?
What do they both contain?

How do they vary?

A

Anchoring junctions

  • Actin cytoskeleton (adherence junctions)
  • Intermediate filaments (desmosomes)

Both contains members of the cadherin family

Variability:

  • steaks or punctuate in non-epithelia
  • belt desmosome- needed for formation of the tight junctions
33
Q

Label this cell

A
34
Q

What does the presence of Ca2+ cause in anchoring junctions?

A

dimerization of cadherins

35
Q

What binding is present in anchoring junctions?

A

The binding is homophilic

36
Q

How many cadherin repeats form a dimer in a cell?

A

5

37
Q

Name the different cadherin’s in different junctions and examples of each?

And where they are found

A
  • Classical Cadherins: E (epithelial) , N(Neuronal), P (placental) and VE (vascular endothelia) cadherins found in adherens junctions
  • Atypical Cadherins: Desmoglein, Desmocollin found in desmosomes
38
Q

How can Ca2+ be removed?

A

using EDTA

39
Q

Cadherins also act as signalling centres concentrating kinases and their substrates, give an example

A

PI3 kinase

40
Q

Anchoring junctions links

A
41
Q

What do beta-catenin regulate?

A

Cell division

42
Q

Tell me the role of PI3 Kinase?

A

drives cell growth

proliferation

differentiation

motility

survival

43
Q

Tell me the role of Beta-catenin ?

A

cell proliferation

stem cell fates

44
Q

Tell me about cell sorting importance in early formation of CNS- in vivo

A
45
Q

What does too much N cadherin mean?

A

Neuronal tube can’t close which can lead to spina bifida and problems in brain formation

46
Q

Where was the notch gene first described?

What did it show?

A

in the fly

It showed genetic inheritance is carried on chromosomes

47
Q

Whats the ligand in the notch called?

A

delta

48
Q

Tell me the steps to Notch signaling ?

A

1= Protease in golgi

2= Extracellular plasma membrane bound enzyme e.g. TACE

3= Intracellular membrane bound enzyme e.g. Gamma-secretase

49
Q

What does Notch signaling regulate?

A

cell division

cell fate

proliferation

50
Q

Lateral inhibition in fly’s

A
51
Q

Tell me about Notch expression in;

Notch, ligands and receptor?

A
  • induces and responds to notch
  • Notch signaling inhibits cell division and induces differentiation
52
Q

Tell me about notch expression in Notch and ligand?

A
  • can induce a signal but doesn’t respond to one
53
Q

Loss of notch ligand in skin cell remains in dividing state and results in what?

A

Hyperproliferation of cells and tumour formation

54
Q

What are selectins?

A

A type of Lectin (sugar binding proteins)

Transmembrane proteins

55
Q

Tell me types of Selectins and when they are expressed?

A

E (activated endothelia) and P (activated endothelia and platlets) selectin expressed by vein endothelial cells in inflammation

56
Q

How do selectins work?

A

By binding to sugars on cell membranes and can cause cell attachmemnt to tissues

BIOL1013 (9 decks)

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