Lecture 7: Junctions

Question 1

What is the structure of integrin?

What does the α-subunit require?

Which subunit determines specificity?

Answer 1

1. α-subunit and β-subunit spanning across the cellular mebrane
2. Metal ions
3. α-subunit

Question 2

Desmosome is a _______ type of junction, the linking protein is _______, the intracellular protein is _____, and the cytoskeletal protein (anchoring) is ______.

Answer 2

Cell-Cell

Cadherin-like

Plakoglobin, Plakophilin, Desmoplakin

Intermediate FIlaments

Question 3

What does mediates hemidesmosome junctions?

What are they bound to within the cell?

Answer 3

Integrins

Intermediate filaments

Question 4

What is the initial activation in the inflammation response of wound healing?

Answer 4

Selectins activate first, leading to eventual integrin activation and binding to leukocytes

Question 5

What do free floating leukocytes bind to on the enothelial cells?

Answer 5

Selectin, followed by integrin

Question 6

JAM, Occludin, and Claudin are what type of proteins?

What do they attach to within the cytosol?

Answer 6

Tight Junction Proteins

Actin

Question 7

What is the structure of cadherins?

How many types are there? How does that affect binding?

Answer 7

Extracellular protein that will find to other cadherin.

There are many types, they will only bind to like species

Question 8

Does integrin have enzymatic properties?

What disorders is it possibly related to?

Answer 8

No, but vital for downstream protein regulation

Autoimmune disorders

Question 9

What can errors in the WNT pathway result in?

Answer 9

Uncontrolled transcription activation

Question 10

What do cadherins bind to within the cell?

Answer 10

Actin cytoskeleton via intermediates

Question 11

What is the role of β-catenin in undifferentiated or cancer cells?

What enzyme causes this to occur?

Answer 11

β-catenin is not phosporylated, causing it to go to the nucleus and activate transcription

Occurs in presence of WNT

Question 12

What mediates the initial weak response in the immune system?

Answer 12

Selectins binding to carbohydrates

Question 13

What is the role of β-catenin in differentiated cells?

How is this regulated?

Answer 13

Activates transcription factors

Regulated by a distruction complex with represses transcription

Question 14

How does Integrin attach to Actin?

Is the bond strong?

Answer 14

Intermediate protein Talin

No, single bonds are weak, but 100s to 1000s are strong

Question 15

What forms an Adherens Junction?

Answer 15

Linked cadherins, anchored to actin filements via protein complexes (α-catenin, β-catenin)

Question 16

Focal Adhesion is a _______ type of junction, the linking protein is _______, the intracellular protein is _____, and the cytoskeletal protein (anchoring) is ______.

Answer 16

Cell-Matrix

Integrin

Talin, α-actinin

Actin

Question 17

Desmosomes

Answer 17

Cadherin like proteins which attach to intermediate filaments within the cell via intermediate proteins, connecting cells to eachother

Question 18

What do selectins bind to?

Answer 18

Selectins bind to oligosaccharides (sugar molecules)

Question 19

Adherens Junction is a _______ type of junction, the linking protein is _______, the intracellular protein is _____, and the cytoskeletal protein (anchoring) is ______.

Answer 19

Cell-Cell

Cadherin

Catenins

Actin

Question 20

What can a defect in the APC protein cause?

Answer 20

FAP

β-catenin is active for differentiated cells, often presents as polyps in colon and other cancers

Question 21

Hemidesmosome is a _______ type of junction, the linking protein is _______, the intracellular protein is _____, and the cytoskeletal protein (anchoring) is ______.

Answer 21

Cell-Matrix

Integrin

BP230, Plectin

Intermediate Filament

Question 22

What are desmosomes linked to within the cell?

Answer 22

Intermediate Filaments via Desmoplakin protein

Question 23

Does cadherin bind directly to actin?

Answer 23

No, requires intermediate “hardware” proteins

Question 24

What is the structure of a Gap Junction?

Answer 24

6 x Connexins forming a single Connexons

Question 25

What is the source of Pemphigus?

What is affected?

Answer 25

Autoimmune disorder caused by desmosomes

Mucus membranes and cardiac

Question 26

What is the role of Gap Junctions?

Answer 26

Movement of small molecules, such as ions