Andersen MCB Lecture

Question 1

CAMs are divided into two groups. What are they?

Answer 1

Calcium Dependent and Calcium Independent.

Question 2

What are the Ca+ Dependent and Ca+ Independent CAMs?

Answer 2

Dependent: Cadherins, Selectins.

Independent: Integrins, Immunoglobulin family.

Question 3

Classical cadherins include E, N, and P-cadherins. Where are they found?

Answer 3

E = Epithelial
N = Nerve cells.
P = Placenta

Question 4

The nonclassical cadherins are found in ___. Examples of these cadherins are __ and __.

Answer 4

Desmosomes.

Desmocollins and Desmogleins.

Question 5

Cadherin superfamily includes various different kinds of intracellular motifs, but they all share a common extracellular region called the __ __ __.

Answer 5

Cadherin domain motif.

Question 6

Binding between cadherins is generally ___, allowing precisely defined spacing between cell membranes at anchoring junctions because the binds are all the same. These binds occur at the _-terminal tips of cadherin molecules.

Answer 6

homophilic.

N-terminal

Question 7

Ca++ ions bind to sites near each hinge, functioning to do what?

Answer 7

Makes the cadherins more rigid, preventing it from flexing.

Question 8

Cadherins bind to each other with relatively high or low affinity? How do strong attachments result?

Answer 8

Low.

Strong attachments result from many, multiple weak cadherin bonds in parallel.

Question 9

Homophilic adhesions between Cadherins mediate selective recognition, enabling certain types of cells to stick together. This process is called:

Answer 9

Sorting out.

Question 10

Different types of cadherins can cause cells to ___ ___ and form different cell types and tissues throughout the embryo.

Answer 10

Migrate away.

Question 11

The appearance and disappearance of cadherin types play a role in the formation of the nervous system. Describe this process:

Answer 11

E-cadherin to N-cadherin transition happens as the neural tube forms and pinches off.

N-cadherin to Cadherin-7 transition occurs to hold the migrating neural crest cells together.

Then, when they form a ganglion, they re-express N-cadherin.

Question 12

These proteins, ___, bind cadherins that hold adjacent cells together to the actin filaments of those cells

They exist in three different forms. What are they?

Answer 12

Catenins.

B and gamma plakoglobin (they are attached to the cytoplasmic end of cadherin). alpha-actenin binds directly to cytoplasmic actin.

Question 13

These are the most common types of cadherins ___.

Answer 13

E-cadherins.

Question 14

These proteins, ___, bind carbohydrates, and lectin is one example.

Carbohydrates bind extracellularly to these proteins at what region?

T/F: Calcium is required for selectin to bind carbohydrates.

Answer 14

Selectins.

Carbohydrate-recognition domain. (CRD).

True.

Question 15

What are the three classes of selectins and what cells are they associated with?

Answer 15

P-selectins: platelets.
E-selectins: endothelial cells.
L-selectins: leukocytes.

Question 16

Integrins bind to the ___ ___ and to the cell’s ___.

Integrin consists of two subunits. What are they?

Integrins bind to ___ and ___ in the extracellular matrix.

Answer 16

extracellular matrix. cytoskeleton.

alpha and beta.

fibronectin and laminin.

Question 17

The laminin and fibronectin in the basement membrane (which integrins bind to) interact with what three proteins?

Answer 17

Collagen (type IV).
Heparan sulfate proteoglycans.
Entactin (nidogen).

Question 18

When the neutrophil slows down in the blood vessel and undergoes transendothelial migration, what proteins assist in this process?

Answer 18

Selectins slow down the rolling neutrophil.

VCAM and ICAM stop the cell, readying it for migration across the extravascular space.

Question 19

VCAMs and ICAMs belong to the ___ superfamily because of the shape of its extracellular segment.

Answer 19

Immunoglobulin superfamily. (extracellular portion is folded into two to six immunoglobulin-like domains)

Question 20

___ anchor cells together and are found on the basolateral surface.

___ establish an impermeable barrier between adjacent cells, preventing transport and maintaining concentration differences.

__ __ enable cells to rapidly exchange ions and small molecules among cells of that tissue.

Answer 20

Adherens.
Occludens.
Gap Junctions.

Question 21

The two types of junctions are __ and __.

Which type is associated with the adherens or occludens variety?

Which type is a “spot” or snap-like junction?

Macula are of the adherens variety, often referred to as ___ or ___. They are associated with intracellular intermediate filaments, aka ___.

Answer 21

Zonula and Macula.

Zonula.

Macula.

Desmosomes or hemidesmosomes.

tonofilaments.

Question 22

Desmosomes are associated with the ___ domains of epithelial cells.

Hemidesmosomes are associated with the ___ domains.

Answer 22

lateral.

basal.

Question 23

Adherens are anchoring junctions that contain these two cadherin proteins: ___ and ___.

The cadherin proteins are anchored to cytoplasmic plaques consisting of __ and __.

Answer 23

Desmogleins and desmocollins.

Desmoplakin and plakoglobin.

Question 24

In most epithelial cells, the intermediate filaments attached to the desmosome, which is on the ___ side of the cell, are ___ filaments.

Answer 24

cytoplasmic.

keratin.

Question 25

A membrane plaque links the hemidesmosome to the basal lamina via these two proteins: __ and __

Answer 25

laminin 5.

integrin a6B4.

Question 26

Pemphigus Foliaceus is a condition caused by what?

Answer 26

antibodies attacking desmoglein 1, causing a loss of adhesion of keratinocytes in the epidermis.

Question 27

Zonula Occludens is a belt-like occluding junction that is also referred to as this type of junction.

T/F: tight junctions prevent backflow of nutrient molecules from basal side of epithelium into the gut lumen.

Answer 27

Tight junction.

True.