Epithelium 2

Question 1

Junctional complexes are found pretty much in every types of cells except…

Answer 1

blood cells

Question 2

When referring to the apical portion of the cell domain, which part of the cell does it pertain to?

Answer 2

top

Question 3

What are zonula occludens and where are they normally found in a cell?

Answer 3

tight junctions normally found near the apical portion of the lateral domain

Question 4

Where are zonula adherens normally found in a cell?

Answer 4

immediately below zonula occludens

Question 5

What are maculae adherens?

Answer 5

desosomes: spot connections between two cells (think of staples between two sheets of paper)

Question 6

In what order will you find the junctional complexes in the epithelium?

Answer 6

zonula occludens (apical)
zonula adherens
macula adherens

Question 7

What is another name for gap junction?

Answer 7

nexus

Question 8

Where do you find hemidesmosomes?

Answer 8

in basal domain

Question 9

What is the general blueprint for a junctional complex?

Answer 9

1) cytoskeletal elements (actin microfilaments or intermediate filaments)
2) intracellular anchor proteins
3) CAMs (aka transmembrane adhesion proteins)

Question 10

What does intracellular anchor proteins anchor?

Answer 10

connects cytoskeletal component to CAMs

Question 11

What are occludins and claudins and what do they do?

Answer 11

CAMs, they form tight connection with one another (ex. occludin from one cell connects to the occludin of the next cell, not occludin to claudin)

Question 12

What does the baterium Helicobacter pylori do to zonula occludens?

Answer 12

disrupts occludins (tight junctions) in the stomach, making cells more susceptible to acidic injury

Question 13

What does cholera toxins do to zonula occludens?

Answer 13

toxic to zonula occludens proteins (intracellular), dirsupts the junctional complex, leading to loss of fluids

Question 14

Gene encoding for a specific claudin in renal epithelial cells results in what?

Answer 14

excessive loss of magnesium ions in urine

Question 15

Which claudin protein is lost in brain cancers?

Answer 15

claudin 5

Question 16

Which missing claudin protein can cause deafness?

Answer 16

claudin 9

Question 17

Why is the ratio of claudins to occludins important?

Answer 17

ratio of claudins to occludins dictates the degree of permeability that exist in tight junctions.

Question 18

If you want less permeability in tight junctions, which should be higher? Claudins or occludins?

Answer 18

high claudins and low occludins

Question 19

What would the ratio of claudin to occludin be in the blood brain barrier?

Answer 19

high occludin and low claudin (low permeability)

Question 20

What role do tight junctions play in establishing polarity within a cell?

Answer 20

tight junctions keep receptors at the apical domain because they can’t cross, this allows for establishment of polarity within the cell

Question 21

What type of cytoskeletal elements will you find in macula adherens?

Answer 21

intermediate filaments (not actin)

Question 22

What’s an example of CAM found in zonula adherens?

Answer 22

E-cadherin

Question 23

What kind of CAMs can be found in macula adherens?

Answer 23

desmocollin and desmoglein

Question 24

What causes Pemphigus?

Answer 24

the body produces antibodies against demogleins (important CAM found in desmosomes)

Question 25

What are focal adhesions?

Answer 25

anchors cell to proteins of the ECM

Question 26

What kind of CAMs can be found in focal adhesions?

Answer 26

integrin

Question 27

What is hemidesmosome?

Answer 27

anchor basement domain of cell to underlying basal lamina

Question 28

What transmembrane protein is involved in hemidesmosomes?

Answer 28

collagen type XVII

Question 29

What is bullous pemphigoid?

Answer 29

body produces antibodies against collagen XVII, causes separation between the cell and basal lamina allowing fluid to build up in between

Question 30

Based on the general blueprint for junctional complexes, what component does integrin represent?

Answer 30

CAM

Question 31

What do nexus (gap junctions) do?

Answer 31

allow cells to communicate with each other

Question 32

What transmembrane protein (CAM) can be found in nexus?

Answer 32

connexins

Question 33

Describe the structure of connexon.

Answer 33

made up of 6 connexins

Question 34

Why would disruptions in nexus cause cardiac arrhythmias?

Answer 34

cardiac muscles have to contract in unison, without gap junctions, the cells cannot communicate with each other

Question 35

What other conditions can disruptions of nexus cause?

Answer 35

- female infertility - neuropathy - deafness - congenital cataracts

Question 36

What can cause loosening of junctional complexes?

Answer 36

mutation in cadherin, catenin, or integrin

Question 37

Where are catenin and vinculin found?

Answer 37

intracellular proteins found in zonula adherens

Question 38

What does loosening of junctional complexes provide for cancer cells?

Answer 38

the ability to become motile (one of the steps to become metaplasia)

Question 39

What type of molecule is cadherin?

Answer 39

CAM

Question 40

Loss of cadherin is found in what and why?

Answer 40

cancerous cells because junctional complexes have been disrupted

Question 41

What does altered expression of integrin do?

Answer 41

allow cells to migrate to extracellular environment