L09 Flashcards
which tissue types interact with the basal lamina
epithelial, muscle, and nervous
what is ECM involved in
providing support and strength
cellular communication
cell migration, polarity and shape
what ECM is involved in providing strength
basal lamina
bone/cartilage
what signaling molecules travel through the ECM
hormones
growth factors
cytokines
what processes require ECM cell migration, polarity and shape
embryonic development
angiogenesis
wound repair
tumour development
what are the features of the basal lamina
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
what are the features of the connective tissue
have reduced cellular content, (cell-cell contact is rare)
with increased ECM content, compared to epithelial, muscle and nervous tissue.
what is the main stress-bearing component of connective tissue
ECM
what type of cells are found in the connective tissue
indigenous and immigrants
give examples for indigenous cells
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)
give an example for immigrant cells
immune cell
what is the composition of connective tissue ECM
similar content in most tissues but ratios and organization varies
- high MW, highly charged polysaccharides (glycosaminoglycans (GAGs) covalently attached to proteins (proteoglycans) bind lots of water
- fibrous proteins (members of collagen family)
- glycoproteins (not part of collagen family) e.g. elastins, fibronectins
Some specialized forms of connective tissue ECM become calcified or become transparent
True
give examples of calcified ECM in connective tissue
Bone and teeth
give an example of transparent ECM in connective tissue
Cornea
what are the features of GAGs
most anionic molecules produced by animals
consist of repeating sulphated disaccharide units
are often linked to a core protein to form proteoglycans (PG)
what are amino sulphated sugars called
N-acetylglucosamines
what are sulphated sugars called
glucuronic acids
give an example of a simple PG
decorin
what are the features of decorin
small, single GAG chain, MW 40 KDa
give an example of a complex PG
aggrecan
what are the features of aggrecan
large, 100 GAG chains,
MW 3,000 KDa,
main component of cartilage
what are the features of fibrous proteins
members of collagen family
most abundant proteins in mammals
long, stiff, triple stranded helical structure
provides tensile (pulling) strength of tissues
what are the features of the collagen family of proteins
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
describe the structure of collagen
3 polypeptides (alpha chains; rich in proline/glycine) form a coil, which can then self-agregrate into fibrils and then fibers
what does procollagen do
prevents aggregation inside cells
collagen is made as procollagen in the cells then released. enzymes chop off the ends allowing it to aggregate
True
what other glycoproteins are there in the ECM
elastins
fibronectins
what are the features of elastins
provide elasticity to connective tissues (similar
in structure to collagen)
dominant component of ECM found in arteries
what are the features of fibronectins
bind other matrix/cell membrane proteins
organize matrix and provide cell-matrix link
what receptor proteins bind to the basal lamina
integrins
what are the features of integrins
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
Integrins allow ECM to interact with
cytoskeleton providing strength. what adapter molecule binds integrins with actin filaments
talin
give an example of how integrins can indirectly bind to collagen fibrils in the ECM
through fibronectin
Integrins exist in inactive/active conformation
true
Why do integrins need an “inactive”
conformation?
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
what is the function of integrins
providing cell-ECM contact
for strength
mediate signaling
how do integrins mediate signaling
via recruitment of focal adhesion
kinase (FAK)
leads to altered gene expression
(e.g. for ECM homeostasis)
