Intercellular Architecture- Lecture 38-39

Question 1

Name the different types of cell adhesion molecules.

Answer 1

cadherins, the Ig superfamily, integrins, and selectins

Question 2

What are the characteristics of cadherins?

Answer 2

homophelic
Ca2+ binding
bind actins and IF

Question 3

What are the characteristics of integrins?

Answer 3

connect cells to extracellular matrix (heterophilic binding)

bind actins

Question 4

What are the characteristics of selectins?

Answer 4

mostly on immune cells help cells find their way out of blood stream

Question 5

What types of proteins are contained in the Extracellular Matrix?

Answer 5

collagen
proteoglycans
multi-adhesive proteins

Question 6

What is the function of the ER?

Answer 6

hold tissues together, provide cushoning (cartilage) and strength (tendons), act as reservoirs for growth factors

Question 7

Polarized cellular organization of epithelial cells allows for ______.

Answer 7

different functions such as absorbtion of nutrients on one membrane and their secretion from another

Question 8

How do the apical, lateral, and basal membranes differ?

Answer 8

apical usually has large surface area (due to presence of vili)
lateral and basal usually separated from apical via specialized cell junctions

Question 9

What is inside out signaling?

Answer 9

intracellular events promote interactions between the cell and the ECM

Question 10

What is outside-in signaling?

Answer 10

extracellular events such as ligand binding that cause interactions between the cell and the ECM

Question 11

Name the types of cell junctions found in epithelial cells.

Answer 11

tight (seal epithelial cells together in sheets– prevent passage of small molecules between cells)
anchoring (join cells to each other and to ECM via two different types: adherens junctions/ desmosomes and focal adhesions/ hemidesmosomes)

Question 12

What are cadherins?

Answer 12

large glycoproteins that link by a homophilic mechanism to actin cytoskeleton (via catenins alpha or beta)

Question 13

What are integrins?

Answer 13

cell matrix receptors on cells that bind ligand with low affinity
composed of alpha and beta subunits held together non-covalently
most are connected to bundled actin filaments (except alpha6beta4 which interacts with IF at hemidesmosomes) mediated by anchor proteins

Question 14

Provide examples of a conditions caused by mutations in connexons in gap junctions.

Answer 14

Charcot-Marie-Tooth X (neurodegenerative demyelinating disease)
sensorineural hearing loss (mutation in GBJ2)

Question 15

What are communicating (gap) junctions?

Answer 15

found in virtually every cell
composed of heximeric complexes called connexons in membranes forming channel
used for amplifying a response across a tissue from a local source such as a neuromuscular junction
allow for movement of molecules less than 1200 daltons across gap junctions

Question 16

Name the components of the ECM.

Answer 16

collagens, proteogycans, and multi-adhesive connectors (fibronectin and laminin)

Question 17

What is the structure and function of the basal lamina?

Answer 17

flexible mats of specialized matrix that underlies epithelial cell sheets and tubes, separating cells from surrounding connective tissue
serve as a highly selective filter

Question 18

What are the main components of the basil lamina for epithelium?

Answer 18

laminins
type IV collagen
perlecan
nidogen

Question 19

Provide an example of a collagen linked disease.

Answer 19

Scurvy- hydroxyproline requires vitamin C, and in its absence, the ECM becomes instable leading to teeth falling out

Question 20

Describe the structure and function of collagen.

Answer 20

trimeric triple helix in structure with regions containing Gly-X-X (X most often is proline or hydroxyl-proline) formed in the ER
withstands tensile forces (stretching)

Question 21

Describe the structure and function of proteoglycans.

Answer 21

formations of carbohydrates and proteins (mostly GAG chains) that bind water and provide hydration
resist compressive forces

Question 22

______ serve as bridges to reinforce the network and connect ECM to cells and other small molecules.

Answer 22

Multi-domain glycoproteins (eg. laminin or fibronectin)

Question 23

Describe the structure and function of elastin.

Answer 23

gllycine, rpoline, hydroxyproline righ fibers sheathed by microfibrils containing fibrillin
allow for recoil after transient stretch

Question 24

Describe Marfan’s Syndrome.

Answer 24

mutation in fibrillin leading to defects in tissues rich in elastic fibers (eg. the aorta)
also associated with increased TGFbeta

Question 25

Describe Duchenne Muscular Dystrophy.

Answer 25

X-linked recessive muscle wasting disease in the dystrophin gene which codes for the dystrophin glycoprotein compled (DGC) which helps stabilize the muscle cells in the context of teh ECM and integrate signaling pathways

Question 26

______ are lectins that mediate Ca2+ dependent cell:cell adhesion in the blood stream.

Answer 26

Selectins

Question 27

Describe the signaling of white blood cells to inflammation areas.

Answer 27

during inflammation, E-selectin is expressed on endothelial cells, which weakly binds the L-selectin on white blood cells and P-selectin on platelets first to coordinate a response with integrins then more strongly when they are present

Question 28

Name the proteases that remodel the ECM.

Answer 28

Matrix Metalloprotease (MMP)
Adamlysins
merpins
tissue plasmogin activation (TPA)
urokinase