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Miscellaneous > MCB Lecture 37 Junctions > Flashcards

MCB Lecture 37 Junctions Flashcards

0
Q

Where are Desmosomes localised? What do they connect?

A

They are localised in the apical region

They connect two cells

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1
Q

What is the function of Desmosomes?

A

Desmosomes connect two cells together.

Distribution of tensile forces

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2
Q

Describe the proteins involved in Desmosomes

A

Cadherin family proteins
Adaptor proteins: desmoplakin, plakoglobin
Intermediate filaments

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3
Q

What is the function of cadherin?

A

It forms the interaction between the two cells in a Desmosome

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4
Q

Which cytoskeletal element to Desmosomes connect to?

A

Intermediate filaments

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5
Q

What are two problems that can occur with Desmosomes ?

A
  1. Mutation in the intermediate filament (keratin)

2. Antibodies for the Desmosome interrupt it

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6
Q

What are focal adhesions? What is their function?

A

They are attachments between the cell and the extracellular matrix
They are involved with cell locomotion and signalling

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7
Q

Describe the protein involved with focal adhesions

A

Integrins attach cell to the ECM
Adaptor proteins: vinculin, Tallin
Actin filaments

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8
Q

Which cytoskeletal element is involved with focal adhesions?

A

Actin filaments

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9
Q

What is an integrin?
Describe its structure
How is there variability in integrin structure?
Which junctions have integrin?

A

It is a protein that connects cells together
It is made up of an alpha and beta subunit
Variability: different alpha and beta subunits present
Focal adhesions and hemidesmosomes have integrins

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10
Q

Describe how cells move

A
  1. Protrusion
  2. Adhesion
  3. Traction
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11
Q

What forces are produced by focal adhesions

A

Cell traction forces

CTF

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12
Q

Describe how focal adhesions are involved in cell signalling.
What are the two types?

A
  1. Inside out:
    Ligand binds to a receptor (GPCR, tyrosine kinase) on the cell membrane. This starts a signal transduction pathway, leading to the activation of talin. Talin binds, and now extracellular matrix proteins can be engaged
  2. Outside in:
    Binding of an ECM protein to the integrin initiates a signal transduction pathway
    Kinases (FAK) recruited
    Gene expression, cell proliferation etc.
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13
Q

Describe inside-out signalling with focal adhesions

A

Ligand binds to a receptor (GPCR, tyrosine kinase) on the cell membrane. This starts a signal transduction pathway, leading to the activation of talin. Talin binds, and now extracellular matrix proteins can be engaged

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14
Q

Describe outside -in signalling in focal adhesions

A

Binding of an ECM protein to the integrin initiates a signal transduction pathway
Kinases (FAK) recruited
Gene expression, cell proliferation etc.

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15
Q

What is FAK?

A

It is Focal adhesion Kinase
It is activated when ECM proteins bind to integrins in focal adhesions

It initiates a cascade of transduction events

16
Q

What is the function and location of hemi desmosomes?

A

These connect cells to the ECM

They give high tensile strength (eg in skin)

17
Q

What proteins are involved in hemi desmosomes?

A

Integrins
Adaptor proteins
Intermediate filaments

18
Q

Which cytoskeletal element is involved with hemi desmosomes?

A

Intermediate filaments

19
Q

How are hemi desmosomes involved with cell proliferation?

A

When tension is detected by the integrins, a transduction pathway is initiated, leading to cell proliferation and G1 progression

20
Q

What do mutations in integrins cause?

A

Skin blistering

21
Q

What are the anchoring cell junctions?

A

Desmosomes
Adherens
Hemi desmosomes
Focal adhesions

22
Q

Describe the function of Gap junctions

A

They allow for direct movement of materials from one cell to another through a small channel

23
Q

Describe the structure of gap junctions

A 
6 connexons form a connexon
Two connexons (one on each cell) line up to form a channel
24
Q

How much space is there between two cells linked by a gap junction?

A

2-4 nm

25
Q

What is meant by homo and heteromeric connexons?

A

Homo: only one type of connexin present
Hetero: different types of connexin

26
Q

What is meant by homo and heterotypic channels in gap junctions?

A

Homo: only one type of connexin
Hetero: different types of connexin in the channel

27
Q

What are the functions of gap junctions? (3)

A
  1. Movement of metabolites
  2. Movement of ions in synapses
  3. Electrical signalling
28
Q

What causes congenital deafness?

A

Defects in gap junction connexins

Miscellaneous (109 decks)

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