Lecture 2 Cell Adhesion Molecules and Junctional Complexes

Question 1

Basement membrane

Answer 1

Separates an epithelial layer from its connective tissue support
Exception is capillaries, no connective tissue

Question 2

Characteristics of the basement membrane

Answer 2

50-80 nm thick

Two components 1. basal lamina 2. reticular lamina

Question 3

Two components of basement membrane

Answer 3

1. Basal lamina

2. Reticular lamina

Question 4

Basal lamina

Answer 4

Sits on reticular lamina

Produced by the epithelium

Question 5

Reticular lamina

Answer 5

Produced by the connective tissue

Question 6

Basement membrane is composed of

Answer 6

Intracellular matrix

Question 7

4 Components of the basal lamina

Answer 7

1. Laminin
2. Type IV collagen
3. Entactin (nidogen)
4. Proteoglycans

Question 8

Laminin

Answer 8

Component of basal lamina
Made of 3 polypeptide chains
-alpha, beta and gamma
Binding sites for entactin and proteoglycans

Question 9

Type IV Collagen

Answer 9

Component of basal lamina
Does not form fibrils like type I collagen
This is collagen produced by epithelial cells, unlike type I collagen which is secreted by fibroblasts

Question 10

Collagen

Answer 10

Connective tissue
most ubiquitous protein in your protein in your body (tendons/ligaments)
20 different kinds, made by 20 different genes

Question 11

Fibronectin

Answer 11

How we hold things together
Made up of two polypeptide chains cross-linked by disulfide bonds
Has binding sites for
-Heparin
-Integrins
-Collagen
-Fibrin

Question 12

4 Things Fibronectin has binding sites for

Answer 12

1. Heparin
2. Integrins
3. Collagen
4. Fibrin

Question 13

Cell Adhesion Molecules

Answer 13

Depending on the need for calcium in their interactions with other molecules, cell adhesion molecules are divided into two groups

1. Calcium dependent
2. Calcium independent

Question 14

Calcium Dependent Cell Adhesion Moleucles

Answer 14

Cadherins

Selectins

Question 15

Calcium Independent Cell Adhesion Molecules

Answer 15

Integrins

Immunoglobulin superfamily molecules

Question 16

Two groups of CAMs

Answer 16

Calcium dependent

Calcium independent

Question 17

3 Types of Cadherins

Answer 17

1. E-Cadherins
2. N-Cadherins
3. P-Cadherins

Question 18

E-Cadherins

Answer 18

Most common type of cadherins
They are found in epithelial tissues
form diners

Question 19

Most common type of cadherin

Answer 19

E-Cadherin

Question 20

Dimers

Answer 20

Generic term for two molecules held together

Question 21

Loss of e-cadherins

Answer 21

Associated with invasive behavior of tumor cells. Occur because of mutations, not all tumors are invasive

Question 22

E-Cadherin dimers

Answer 22

HVA binding face
Dimers between epithelial tissues form homophilic interactions
Loss of e-cadherins is associated with invasive behavior of tumor cells

Question 23

N-Cadherins

Answer 23

These are found in nerve tissues

Question 24

P-Caderins

Answer 24

Found in placenta

Question 25

Catenins

Answer 25

Cytoplasmic domains of cadherins are linked to actin through catenins

Question 26

Alpha Catenin

Answer 26

(sounds like actin) | Bind directly to actin

Question 27

Beta Catenin

Answer 27

Bind to cadherin and to y-catenin/plakoglobin | Involved in colorectal carcinogenesis

Question 28

Characteristics of selectins

Answer 28

1. Selectins bind to carbohydrates, therefore they belong to the lectin group 2. Selectins are involved int he movement of leukocytes from blood to tissues (extravasation)

Question 29

Extravasation

Answer 29

Selectins are involved in the movement of leukocytes from blood to tissues

Question 30

Leukocytes

Answer 30

Make in bone marrow involved in immune response

Question 31

3 Classes of Selectins

Answer 31

1. P-selectins 2. E-selectins 3. L-selectins

Question 32

P-Selectins

Answer 32

Platelets (surface of)

Question 33

E-Selectins

Answer 33

Activated Endothelial cells | -during inflammatory process, they are activated

Question 34

L-Selectins

Answer 34

Leukocytes

Question 35

Integrins

Answer 35

Calcium independent Mainly involved in cell-extracellular matrix interactions Integrins bind to both the extracellular matrix and to the cytoskeleton Integrins are heterodimers The extracellular domains of integrins bind to molecules in the basement membrane

Question 36

Integrins bind to both

Answer 36

The extracellular matrix and to the cytoskeleton

Question 37

Heterodimers

Answer 37

Different types of molecules involved | Integrins are these

Question 38

2 major molecules in basement membrane

Answer 38

1. Fibronectin | 2. Laminin

Question 39

Integrins interact with

Answer 39

``` the RGD (Arg-Gly-Asp) sequence in fibronectin and laminin -if sequence is disrupted, they won't bind ```

Question 40

Laminin and fibronectin in the basement membrane interact with

Answer 40

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

Question 41

Integrin Heterodimers

Answer 41

Each consists of one alpha subunit (17 kinds) and one beta subunit (8 kinds) *combined in different ways The cytoplasmic domain of the beta subunit is linked to actin filaments via connecting proteins Connection proteins include: - Talin - Vinculin - Alpha-actinin

Question 42

3 Connecting proteins include

Answer 42

1. Talin 2. Vinculin 3. Alpha-actinin

Question 43

Characteristics of the Immunoglobulin superfamily

Answer 43

Members of this family possess an extracellular segment with one or more folded domains characteristic of immunoglobulins

Question 44

Members of the Ig-superfamily

Answer 44

N-CAM | I-CAM-1 and I-CAM-2

Question 45

N-CAM

Answer 45

Member of Ig-superfamily These are neural adhesion molecules They mediate both homophilic and heterophilic interactions

Question 46

I-CAM-1

Answer 46

Facilitates transoendothelial migration of leukocytes

Question 47

Adherens

Answer 47

Bind cells together. Can bind cells to the basement lamina too Type of junction Designed to anchor cells together Can be found on the basolateral surfaces of epithelial cells

Question 48

Occludens

Answer 48

Junctional complexes that establish an impermeable barrier between adjacent cells, especially epithelial cells, that prevents paracellular transport.