Extracellular Matrix Flashcards
major protein components of the ECM
collagens (mainly Type 1)
glycoproteins
proteoglycans
glycoproteins
proteins that are studded with sugar groups (oligosaccharides)
have a branched group that could be n-linked or O-linked
proteoglycans
more polysaccharide than protein
The chains are much longer than glycoproteins, hundreds of sugars on each of the back chains
can be linked to cell surface, embedded in membrane, or free in ECM
**most are free in the extracellular matrix and not bound to cell
have only o-linked sugars
Type IV collagen is unlike the other collagens, why?
It does not form fibers, it forms networks
What makes up a collagen fiber?
a bundle of fibrils
What type of collagen produces stripes on EM imaging?
Type 1 collagen
Assembly of type 1 collagen
Collagen molecules (triple helices in braid like structure)
assemble into fibrils
fibrils assemble into fibers
then fibers undergo further assembly based on tissue
What is unique about type III collagen?
has fine fibrils and does not detach from the cell like most ECM components
forms a network in tissues
Most abundant collagen
type I collagen
Collagen only in cartilage and vitreous humor of eye
Type II collagen
Collagen that forms reticular connective tissue of spleen and lymph nods
type III collagen
Collagen of basal lamina
Type IV colagen
Ehlers-danlos syndrome
mutation in type V collagen
stretchy skin, hyperextension of joints
Osteogenesis imperfect
bone deformities and blue sclera, defect in type 1 collagen
Scurvy
vitamin C deficiency, which is a required cofactor for the enzyme that hydroxylates proline
Elastin
Gives connective tissue a rubbery-like consistency
found in aorta and other large blood vessels, the outer ear and the lungs/airways
How elastin works
Elastin sheets fold up and are connected by disulfide bonds. These are scrunched in the relaxed state.
When stretched, the proteins unfold and there is a thermodynamic force that wants to fold them back up again
fibrillin
scaffold/anchor for elastin fibers to lamina densa
also involved in signaling
marfan syndrome
mutation in fibrillin (which is involved with elastin)
causes long bones/fingers and often premature death due to aortic rupture
fibronectin
Responsible for cell adhesion and
mediates migration; possesses binding
sites for integrins, type IV collagen,
heparin, and fibrin
RGD (arginine, glycine, aspartic acid)
focal adhesion
link integrins to actin between cell and basal lamina
hemidesmosome
binds cell to basal lamina via intermediate filaments
basement membrane
basal lamina + reticular lamina
Basal lamina
made by epithelial cells
type IV collagen
lamina lucida and lamina densa
reticular lamina
made by connective tissue and is made of type III collagen
integrins
how cells bind to ECM
have an alpha chain and a beta chain
link cytoplasmic actin to extracellular matrix molecules like fibronectin
laminin
glycoprotein found in basal lamina
tenascin
glycoprotein found in developing tissues with anti-adhesive effects
