CAMs

Question 1

What are the two classes of cadherins?

Answer 1

Classical- E cadherins, typically form cis and trans homphilic dimers.

Non-Classical- desmocollins and desmogleins
(Found in desmosomes)

Question 2

What is the role of E-cadherins?

Answer 2

To link the cells’ cytoskeletons together.

Question 3

Where can E-cadherins be found and how do they bind?

Answer 3

They can be found at the tip of the extracellular end of cadherin and they form dimers via HVA binding face. Calcium ions bind to four extracellular domains and facilitates cis-homophilic dimers.

Question 4

What are catenins?

Answer 4

Small proteins that link the cytoplasmic end of the cadherin with cytoplasmic actin.

Question 5

How many types of catenin are there? And where are they located?

Answer 5

3 types alpha beta and gamma. Located at the cytoplasmic end of cadherin.

Question 6

What are the roles of alpha beta and gamma catenin?

Answer 6

Beta may be a transcription factor. But also binds to alpha

Alpha binds directly to actin.

Question 7

What a are selectins?

Answer 7

They have 2 binding sites, one for carbohydrates and one for calcium.
They move leukocytes from blood to tissues.

Question 8

What is the role of integrins?

Answer 8

Integrins bind the cell to the cytoskeleton and extra cellular matrix (basement membrane).

Question 9

What do the domains of integrin bind to?

Answer 9

The alpha and beta domains bind to fibronectin and laminin in the basement membrane via tonofilaments.

Question 10

What sequence in fibronectin and laminin do integrins interact with?

Answer 10

The RGD sequence

Question 11

Describe the immunoglobulin family.

Answer 11

They possess an extracellular segment with one or more folded domains.
Members: N-CAM and I CAM 1 and I CAM 2

Question 12

What is the role of adherens?

Answer 12

To anchor cells together on the basolateral surface.

Question 13

Adherens have intercellular spaces filled with which proteins?

Answer 13

Cadherin proteins desmogleins 1 and 2 and desmocollins.
Disorder of desmogleins 1 leads to blisters
The cadherin proteins are anchored to cytoplasmic plaques containing desmoplakin and plakoglobin.

Question 14

What are occludens?

Answer 14

They establish an impermeable barrier between cells in order to maintain concentration differences between environments.

Question 15

What is the zonula?

Answer 15

Can either be an adherens or occulens. It travels around the cells linking them together (belt like).
Associated with actin with help from the desmogleins and democollins.

Question 16

What is the macula?

Answer 16

Are a variety of adherens, called desmosomes(lateral) and hemidesosomes (basal)

Question 17

What are gap junctions?

Answer 17

Molecular pores that allow cells to rapidly exchange ions and help coordinate activities.

Question 18

What are hemidesosomes

Answer 18

They anchor the basal domain of the cell.
They’re made of a cytoplasmic plate associated with intermediate filaments like keratin.
A membrane plaque links the hemidesosomes to the basal lamina via laminin and integrin.

Question 19

Name the 4 types of CAMs and specify which ones are calcium dependent.

Answer 19

Cadherins and Selectins- calcium dependent

Integrins and immunoglobulin supper family- calcium independent.

Question 20

What is the structure of gap junctions

Answer 20

They’re made of connexons which are made up of 6 connexins which form a hexagonal structure with a hollow center.
They’re often clusters into patches
They facilitate movement of molecules up to 1.2 nm in diameter
They close when Calcium levels are high
They are responsible for chemical and electrical coupling