Extracellular Matrix Flashcards
1
Q
Why is the basement membrane considered an ECM?
A
- exterior to cells
- made by both epithelial and connective tissue
- main functions are communicating with cells and binding them to underlying connective tissue
2
Q
Describe some of the characteristics of ECM
A
- generally, medium is gel-like
- complex and intricate structural network that surrounds and supports cells within the connective tissue
- composed fibers (collagen/elastic), proteoglycans, proteins like laminin/fibronectin, GAG’s
3
Q
What allows for integrin and laminin to bind?
A
- this binding mediates the binding of the rest of the matrix
- integrins composed of alpha and beta structure
- dimer has binding site for amino acid motif RGD on outer membrane surface and binds to cytoskeleton on inner membrane surface
4
Q
Describe some characteristics of the interstitial matrix
A
- has cells scattered throughout
- cells are not connected to each other
- contains fibroblasts that have integrins, which bind with fibronectin, which in turn binds to proteoglycans and collagen
5
Q
fibronectin
A
- two chains linked via disulfide bridge
- contains several binding domains that interact with dif ECM molecules and integrin
- important in cell attachment to ECM
- in tissues, it forms fibers and aggregates
6
Q
fibrillar collagen
A
type I collagen
formed from braids of chains
7
Q
laminin
A
formed from three different protein chains
8
Q
tenascin
A
formed from six different protein chains
9
Q
type IV collagen
A
- long protein chain in kinks
- does not form fibers
10
Q
hyaluronan
A
- very long polysaccharide
- contains amino sugars (very unusual)
- also called glycosaminoglycan (GAG)
- no protein attached
- found outside animal tissue)
11
Q
decorin
A
- GAG chain and protein covalently attached
12
Q
perlecan
A
- present in cartilage almost exclusively
13
Q
aggrecan
A
- core protein of proteoglycan
- many chains attached
14
Q
Describe the EM of dense type I collagen ECM
A
- bundles of fibrils with striped pattern –> most prominent in type I collagen
- quasi-crystalline structure
- stain binds to different parts of the fiber in a regular fashion creating stripes
15
Q
Describe the assembly of type I collagen
A
- triple helices (tropocollagen aska collagen molecules)
- consists of two identical chains (both specified by same gene) and one dif chain (dif gene) - collagen molecules assemble into fibrils
- fibrils assemble into fibers
- depending on tissue type, fibers assemble into mesh (sometimes need strength in all directions) or in one direction (i.e. tendon)