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AMM > Cell-cell adhesion > Flashcards

Cell-cell adhesion Flashcards

1
Q

Which transmembrane adhesion protein makes up adherens junctions?

A

cadherin

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2
Q

What is the intracellular cytoskeletal attachment of adherens junctions?

A

Actin filaments

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3
Q

Which transmembrane adhesion proteins make up desmosomes?

A

cadherin (desmoglein and desmocollin)

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4
Q

Which intracellular cytoskeletal attachment makes up desmosomes?

A

Intermediate filaments

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5
Q

Which cadherins are involved in homophilic binding?

A

classical and desmosomal cadherins (cadherin interacts with same cadherin on another cell)

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6
Q

Which cadherins are involved in heterophilic binding?

A

Fat cadherin (binds to dachsous)
Classical cadherins

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7
Q

What ions are cadherin-mediated adhesions dependent on?

A

calcium

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8
Q

What is the structure of cadherin?

A

Short intracellular domain

Long extracellular domain

5 cadherin repeats linked by short linker segments

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9
Q

What happens to cadherin structure in presence of low calcium?

A

Cadherin becomes flexible and hook-shaped

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10
Q

How does calcium stabilise cadherin?

A

calcium ions bind at interphase between cadherin repeat domains and linker segments

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11
Q

Do cadherins bind with low or high affinity? How can it become higher?

A

Low
Become high affinity through velcro principle.

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12
Q

Which protein groups connect cadherins to the actin filaments?

A

Catenins
Vinvulin

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13
Q

What are filopodia?

A

finger-like protrusions made of actin filaments

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14
Q

What do filopodia become after Rac?

A

Lamellipodia

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15
Q

What happens in adherens junctions assembly when Rac is deactivated and Rho is activated?

A

Formation of parallel bundles of actin filaments.

Formation of myosin bundles (contraction structures)

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16
Q

Which desmosome is a key adapter protein linking intermediate filaments to desmosomal cadherins?

A

desmoplakin

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17
Q

What is an important molecule in the transduction of mechanical tension by adherens junctions?

A

Alpha-catenin

18
Q

During cadherin-cadherin binding, a pulling force occurs between cells.

What do the catenin proteins do at this time?

A

Extend to unfolded position.

Bind to vinculin.

Vinculin recruits more actin filaments.

19
Q

What is the adhesion belt?

A

Adherens junctions lining the lumen of gut.
Linked to actin filaments, circling the inner edge of epithelial cells.

20
Q

How does a sheet of epithelial cells become an epithelial tube?

A

Organised tightening of the adhesion belt.
Invagination of the epithelial sheet.
Pinching off of epithelial tube.

21
Q

What is cadherin-dependent cell-sorting dependent on?

A

cadherin type
cadherin levels

22
Q

Which cadherin is expressed by neuronal crest cells?

A

Cadherin 7

23
Q

What are the four main functions of adherens junctions?

A

Tube structure formation.
Cell sorting.
Dynamic cell-cell adhesion
Signalling platforms

24
Q

How does P120 catenin affect signalling of RhoA, NF-KappaB signalling and MAPK?

A

Blocks RhoA signaling
Blocks NF-kappaB signaling
Blocks the MAPK pathway

25
Q

What pathway is beta catenin involved in?

A

Wnt signaling pathway

26
Q

What does contact inhibition of cell proliferation ensure?

A

Tissue homeostasis

27
Q

During cell density sensing, what protein does alpha catenin bind to?

A

Scaffold protein 14-3-3 in cell cytoplasm

28
Q

Which protein does alpha-catenin/14-3-3 complex bind in the cytoplasm during cell density sensing?

A

Yap

29
Q

What is Yap protein?

A

Transcriptional co-activator

Promotes cell growth

Can serve as oncogene when deregulated

30
Q

Why does the alpha catenin-14-3-3 complex bind Yap when the cell is well connected via adherens junctions?

A

Bound Yap remains in the cytoplasm.
Prevents it from entering nucleus and promoting cell growth.

31
Q

What does disruption of adherens junctions lead to (regarding Yap)?

A

The alpha catenin/14-3-3 complex releases Yap.
Yap is phosphorylated and enters nucleus.

32
Q

When adherens junctions are disrupted and Yap is allowed to enter the nucleus, what does it bind to?

A

TEAD transcription factors

33
Q

How is cell proliferation inhibited in hair follicles?

A

Dermal stem cells in Bulge remain quiescent in G0 until hair needs to be generated.

Cell density detected by alpha-catenin-dependent adherens junctions.

34
Q

Which trans-membrane protein is involved in transient cell-cell interactions?

A

Selectins

35
Q

What are the three types of selectins (and where are they found)?

A

L-selectins (Leukocytes)
P-selectins (platelet)
E-selectins (endothelial cells)

36
Q

What are the three main domains of a selectin?

A

Lectin domain
EGF-like domain
Cytoplasmic domain

37
Q

What do selectins bind to?

A

carbohydrates

38
Q

Why are endothelial cells encouraged to express E-selectin during inflammation?

A

To attract WBCs expressing carbohydrates

39
Q

Why is the adhesion between endothelial cells and leukocytes (via selectins bonding to carbohydrates) weak?

A

so leukocytes can roll along the endothelial cells surface to site of inflammation.

40
Q

The weak adhesion and rolling of WBCs is selectin-dependent. The switch to strong adhesion is dependent on which protein?

A

Integrin

41
Q

What are two examples of Immunoglobulin (Ig)-like superfamily CAMs?

A

NCAM (neural)
ICAM (intracellular) - important in WBC binding to endothelial cells

42
Q

What is the main difference between cell-cell adhesion mediated by cadherins vs CAMs?

A

Calcium is required for cadherin-mediated cell-cell adhesions.

AMM (18 decks)

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