10- Extracellular Matrix Flashcards
hemidesmosome
Link intermediate filaments in cell to basement membrane
Cell matrix anchoring junction
actin-linked cell-matrix adhesion anchors
actine filaments in cell linked to ECM
Cell matrix anchoring junction
adheren junctions
Adheres actin filaments from one cell to another.
Cell-cell anchoring junction
Desmosome
connects intermediate filaments form one cell to another
Cell-cell anchoring junction
gap junctions
allow for small water soluble molecules to pass from cell to cell.
Channel forming junctions
Basement membrane
Part of ECM
Fibrous extracellular layer that separates epithelium from underlying connective tissue or tissue layers
Basal lamina- what epithelial are sitting on. (made of laminin and collagen)
Reticular layer- what fuses basal lamina to connective tissue below. (made of fibernectin and also collagen)
Connective tissue
Part of ECM
Consists predominantly of ECM (bone cartilage)
Ground substance
a gel-like substance formed from polysaccharides
The stuff that makes up ECM
GAGs
Glycosaminoglycans
Sugars with sulfate group added, (-) charged
– trap (+) ions, accumulate water, provide mechanical support
Ex. chondroitin sulfate, heparin sulfate
Hyaluron
specialized GAG, non-sulfated
Can bind and organize proteoglycans
Proteoglycans
combination of protein and GAGs
interact with other structural components
Collagen
Major protein of ECM (single most abundant protein in human body)
Embeded in ground substance
What is the sequence of collagen?
Glycine-proline-hydroxyproline
Some variation
Glyc is small and allows for tight compacting
Prolylhydroxylase
Enzyme in ER.
Produces hydroxyproline from proline.
REQUIRES vitamin C
Vitamin C deficiency
Could result in deficiency to produce mature collagen fibrils.
stages of collagen
Procollagen- soluble precursor with non-helical domains, cleaved after secretion
Tropocollagen- Collagen molecules, tightly packed triple helix.
Collagen fibrils- Self-assembled collagen molecules, align head to tail, crosslinks stabilize
Collagen fibers
Thick accumulations of collagen fibril
Wavy appearance
Non-fiber forming Collagens
Do not polymerize into fibers
contribute to basement membrane or form structural networks.
Reticular fibers
found at boundary of connective tissue and cells.
Collagen fibrils in MESH like network
Formed during wound healing.
Elastic Fibers
Another substance in ECM
Can stretch then recoil to it’s original state
Made of:
Elastin: randomly coiled, hydrophobic, crosslink to one another (covalent)
Fibrillin: surounding network of microfibrils, glycoproteins used to support elastin assembly.
What is the forms of elastic fibers?
tropoelastin: secreted form
lysyl oxidase: crosslinking enzyme located on the cell surface
Crosslinked aggregates assemble on preexisting fibrilin microfilaments
Fibronectin
Matrix ADHESION protein
Principle adhesion protein of connective tissue
contains multiple adhesion domains.
- Collagen binding domain
- GAG binding domain
- Integrin binding domain
Laminin
Matrix ADHESION protein
Principle adhesion protein of basal lamina
T shaped hetrotrimers
Form mesh-like network
Also contain multiple adhesion domains
Integrins
Cell surface receptors
Majorly responsible for cell matrix interactions
Bind to ECM: collagen, fibronectin, laminin
Anchor to intracellular cytoskeleton
- actin
- intermediate filaments
