Cell adhesion & ECM

Question 1

What are the 3 main classes of junctions?

Answer 1

Anchoring - adhesion of cell-cell or cell-extracellular membrane adhesion

Occluding - create impermeable or semipermeable barrier between adjacent epithelial cells

Communicating - channels that mediate electrical signaling

Question 2

What are the 4 types of anchoring junctions?

Answer 2

Adherens Junction
Desmosome
Hemidesmosome
Focal Contact

Question 3

Function and adhesion molecule of:

Adherens Junction

Answer 3

Cell-Cell adhesion
Cadherins
Associated with ACTIN
Stabilized by Desmosomes

Question 4

Function and adhesion molecule of:

Desmosome

Answer 4

Cell-Cell adhesion
Desmosomal Cadherins (desmoglein, desmocollin)
Associated with intermediate filaments

Question 5

Function and adhesion molecule of:

Hemidesmosome

Answer 5

Basal Surface of Cell-Underlying ECM
Integrins (which interact with laminin and collagen)
Associate with Intermediate filaments

Question 6

Function and adhesion molecule of:

Focal Contacts

Answer 6

Found between cells basal surface and ECM
Adhesion of Cell-Substratum
Integrins
Associated with actin

Question 7

Function and Transmembrane proteins of:

Occluding Junction / Tight Junctions

Answer 7

Forms a regulated seal between plasma membrane of adjacent cells. Luminal surface from intercellular space and basal surface

TM proteins = claudins and occludin
ZO proteins link TM proteins to ACTIN

Question 8

Junctional Complex is composed of

Answer 8

Tight Junction
Adherens Junctions
Desmisomes

Question 9

Function and adhesion molecule of:

Gap Junctions

Answer 9

Hydrophilic Channel (small only)
Formed by 2 connexons (composed of connexin proteins)
Function: intercellular communication

Question 10

4 Major Families of Cellular Adhesion Molecules (CAMs)

Answer 10

Cadherin
Immunoglobulin
Integrin
Selectin

Question 11

Characteristics of cadherins

Answer 11

Cell-Cell (homophilic)
Bind to catenins, which bind to actin (necessary for function)
Beta-catenin stabilizes and also plays a role in cell turnover
Calcium dependent

Question 12

Characteristics of Immunoglobulin Super Family

Answer 12

Cell-Cell (homo-and hetero phillic)
Interacts with Self or integrins
Adhesion molecule: ICAM & VCAM
Bind to actin

Question 13

Characteristics of Integrins

Answer 13

Cell-Cell, Cell-ECM

Associated with actin & intermediate filaments

Question 14

Characteristics of Selectins

Answer 14

Cell-Cell in bloodstream (hetero)
Only bind to carbohydrates
Associated with ACTIN

Question 15

Function of fibroblasts?

Answer 15

Secretion of ECM proteins

Question 16

Components of ECM

Answer 16

Collagen
Basement Membrane
Laminin
Glycosaminoglycans
Proteoglycans
Elastic Fibres
Fibronectin
Fibrinogen

Question 17

Function of Collagen

Answer 17

Strength and stability of connective tissue

Question 18

Basement membrane function

Answer 18

Anchors epithelial cells to connective tissue

Connected to cells through integrins

Question 19

Laminin Function

Answer 19

Major component of basement membrane

Mediates hemidesmosomal attachments

Question 20

Glycosaminoglycans Function

Answer 20

Long Carb. Chain (polysacch)
Anionic groups (strong negative charge)
Hyaluronic Acid = non-sulphated GAG (helps cartilage resist compression)

Question 21

Elastic Fibres function

Answer 21

Allow recoil of stretched tissue

Elastin and fibrillin = major protein components

Question 22

Fibronectin function

Answer 22

Attaches cells to ECM components via integrins

Question 23

Fibrinogen function

Answer 23

protein component of blood clots
binds cells to other ecm components
Cleavage by thrombin