L09

Question 1

which tissue types interact with the basal lamina

Answer 1

epithelial, muscle, and nervous

Question 2

what is ECM involved in

Answer 2

providing support and strength

cellular communication

cell migration, polarity and shape

Question 3

what ECM is involved in providing strength

Answer 3

basal lamina

bone/cartilage

Question 4

what signaling molecules travel through the ECM

Answer 4

hormones

growth factors

cytokines

Question 5

what processes require ECM cell migration, polarity and shape

Answer 5

embryonic development

angiogenesis

wound repair

tumour development

Question 6

what are the features of the basal lamina

Answer 6

very thin layer of ECM produced by cells above and below

evolutionary conserved

essential for maintaining epithelial tissues

composed of laminin, type IV, XVIII collagen, nidogen, perlecan fibronectin

Question 7

what are the features of the connective tissue

Answer 7

have reduced cellular content, (cell-cell contact is rare)
with increased ECM content, compared to epithelial, muscle and nervous tissue.

Question 8

what is the main stress-bearing component of connective tissue

Answer 8

ECM

Question 9

what type of cells are found in the connective tissue

Answer 9

indigenous and immigrants

Question 10

give examples for indigenous cells

Answer 10

primitive mesenchymal cells:

• undifferentiated cells that can lead to the generation of other connective tissue cells, fat cells (adipocytes), mast cells (release histamine), and fibroblasts (found in many connective tissues and synthesize most of the molecules found in the ECM)

specialized cells (adipocytes, mast cells, chondrocytes, osteoblasts):

• found in specialized connective tissues (e.g. cartilage, bone)

Question 11

give an example for immigrant cells

Answer 11

immune cell

Question 12

what is the composition of connective tissue ECM

Answer 12

similar content in most tissues but ratios and organization varies

1. high MW, highly charged polysaccharides (glycosaminoglycans (GAGs) covalently attached to proteins (proteoglycans) bind lots of water
2. fibrous proteins (members of collagen family)
3. glycoproteins (not part of collagen family) e.g. elastins, fibronectins

Question 13

Some specialized forms of connective tissue ECM become calcified or become transparent

Answer 13

True

Question 14

give examples of calcified ECM in connective tissue

Answer 14

Bone and teeth

Question 15

give an example of transparent ECM in connective tissue

Answer 15

Cornea

Question 16

what are the features of GAGs

Answer 16

most anionic molecules produced by animals

consist of repeating sulphated disaccharide units

are often linked to a core protein to form proteoglycans (PG)

Question 17

what are amino sulphated sugars called

Answer 17

N-acetylglucosamines

Question 18

what are sulphated sugars called

Answer 18

glucuronic acids

Question 19

give an example of a simple PG

Answer 19

decorin

Question 20

what are the features of decorin

Answer 20

small, single GAG chain, MW 40 KDa

Question 21

give an example of a complex PG

Answer 21

aggrecan

Question 22

what are the features of aggrecan

Answer 22

large, 100 GAG chains,

MW 3,000 KDa,

main component of cartilage

Question 23

what are the features of fibrous proteins

Answer 23

members of collagen family

most abundant proteins in mammals

long, stiff, triple stranded helical structure

provides tensile (pulling) strength of tissues

Question 24

what are the features of the collagen family of proteins

Answer 24

synthesized by indigenous ECM cells (e.g. fibroblasts)

40 different types encoded by different genes

3 polypeptides (a chains; rich in proline/glycine) form a coil

different a chain combinations lead to different types of collagen (Type I- XVIII) found in differing connective tissues

e.g. type II, IX found in cartilage type XVIII is found in the basal lamina

Question 25

describe the structure of collagen

Answer 25

3 polypeptides (alpha chains; rich in proline/glycine) form a coil, which can then self-agregrate into fibrils and then fibers

Question 26

what does procollagen do

Answer 26

prevents aggregation inside cells

Question 27

collagen is made as procollagen in the cells then released. enzymes chop off the ends allowing it to aggregate

Answer 27

True

Question 28

what other glycoproteins are there in the ECM

Answer 28

elastins fibronectins

Question 29

what are the features of elastins

Answer 29

provide elasticity to connective tissues (similar in structure to collagen) dominant component of ECM found in arteries

Question 30

what are the features of fibronectins

Answer 30

bind other matrix/cell membrane proteins organize matrix and provide cell-matrix link

Question 31

what receptor proteins bind to the basal lamina

Answer 31

integrins

Question 32

what are the features of integrins

Answer 32

24 different integrins alpha and beta chain with large N terminal domain have short intracellular domain that binds adapters -- similar to those seen with cadherins

Question 33

Integrins allow ECM to interact with cytoskeleton providing strength. what adapter molecule binds integrins with actin filaments

Answer 33

talin

Question 34

give an example of how integrins can indirectly bind to collagen fibrils in the ECM

Answer 34

through fibronectin

Question 35

Integrins exist in inactive/active conformation

Answer 35

true

Question 36

Why do integrins need an “inactive” conformation?

Answer 36

many cells in connective tissue are not stationary and migrate through ECM use integrins to “pull” themselves through the ECM cell-ECM contacts therefore need to be made and broken

Question 37

what is the function of integrins

Answer 37

providing cell-ECM contact for strength mediate signaling

Question 38

how do integrins mediate signaling

Answer 38

via recruitment of focal adhesion kinase (FAK) leads to altered gene expression (e.g. for ECM homeostasis)