Cell Adhesion and the Extracellular Matrix Flashcards
What is in the extracellular matrix?
+ Fibrillar proteins
- collagen
- elastin
- fibronectin
- laminin
+ Polysaccharides glycosaminoglycans (in proteoglycans)
What are GAGs?
Glycosaminoglycans: when organised by specific proteins they make proteoglycans
+ Long chains of repeating disaccharide units
+ Highly chahrged (-ve) and highly hydrated
What do fibroblasts synthesise?
+ Collagen
+ Elastin
+ Proteoglycans
Where is collagen synthesised and how is it released?
It is synthesised in the RER and assembled to form a triple helix (needs vitamin C)
It is released via the secretory pathway (through golgi, as procollagen)
What happens once procollagen has been secreted?
It is trimmed to tropocollagen and then cross-linked to make a fibril
What makes collagen secretion special?
Collagen is packaged into specialised (large) vesicles in the RER
What is the membrane tube surrounding fibroblasts called?
Fibropositor: these are oriented along the tendon direction in groups - collagen fibres
What do proteoglycans provide to the ECM?
+ Matrix support/cushioning/hydration
+ Glue-like function
+ Links between proteins of the ECM and ECM and cell surface
Name some different versions of GAG chains
+ Keratan sulfate (KS)
+ Chondroiton sulfate (CS)
+ Dermatan sulfate (DS)
+ Hearan sulfate (HS)
How does linking extracellular matrix to cytoskeleton work?
Collagen/proteoglycans bind Fibronectin that links to Integrins within the plasma memberane
Integrins themselves then bind via Adaptors to Actin cytoskeleton
What are the functions of myofibroblasts?
+ Fibroblast-like; secrete collagen
+ Smooth muscle-like; synthesis actin, myosin and desmin
What is the role of myofibroblasts in tissue damage?
+ Proliferate
+Secrete collagen (scaffold)
+ Consolidate damaged area (fibrous scar)
+ Contract (reduce size of damaged area; express focal adhesions and smooth muscle actin)
When are myofibroblasts also active, besides wound healing?
In tissue fibrosis e.g liver cirrhosis
What are the functions of adipocytes?
+ Insulation
+ Packing
+ Energy store
