6. Extracellular Matrix Flashcards
what roles does the Extracellular matrix play?
what things require an appropriate ECM?
organization: control of cell behavior by binding of growth factors and interaction with cell surface receptors
protection: milieu for inflammatory response, retains water, buffering against extracellular change
mechanical: tensile and compressive strength, elasticity
cell differentiation, migration, proliferation all require ECM
what forms does the ECM take?
what are the major proteins of these structures?
consists of
basil laminae:
-collagen type 4, proteoglycans, glycoproteins
fibrils:
-collagen 1, 2, 3, fibroncectin, and elastin
amorphous matrix (ground substance):
- hyaluronic acid
- proteoglycans, and glycoproteins
where is basal lamina found?
especially in what cells?
underlies all epithelia including endothelium in blood vessels;
the epithelial cells rest on the basal lamina
especially in the muscle, epithelium , schwa cells in peripheral nerve, and kidney glomerulus where it helps keep protein from filtering through
what are some of the major proteins in the network of basal laminae proteins?
what are they linked by?
-type 4 collagen fibers, integrin, laminin, and heparan sulfate proteoglycans which are all linked together by smaller protein nidogen
what is the clinical importance of basal lamina?
- regeneration of epithelium (e.g. after burns)
- neccessary for regeneration of muscle fibers and peripheral axons
- inhibits growth of tumors
- can have autoimmune diseases bc of attachment structures
what is the amorphous matrix?
how does it stain?
functions?
-stains poorly
-consists of hyaluronic acid
-sulfated proteoglycans
-adhesive glycoproteins
collagens type I and/or III
serum proteins and growth factors
functions:
1) suspend and support connective tissue cells
2) permits diffusion of gas and solutes
3) inhibits invasion of bacteria
what are proteoglycans?
what are glycosaminoglycans?
glycosaminoglycans: GAG
- glycos: long chains of repeating disacharides
- amino: attached to protein core
- glycans: protein core is sulfated—> highly negative charge
proteoglycans are proteins with covalently attached glycosaminoglycan side chains (like a bottle brush)
what is the function of GAGs and proteoglycans in the ground substance?
- hydration of the ECM …especially aggrecan in cartilage and hyaluronic acid in embryos
- Shock absorption (negative charges repel with pressure applied)
- filtration (think kidney glomerular basement)
- link ECM to cytoskeleton
- lubrication
the cartilage proteoglycan- aggrecan is important bc?
this proteoglycan acts as shock absorber in the amorphous ground substance
-aggrecan is pretty big (size of 0.3 micrometers) and has hyaluronic acid and GAGs including chondroitin sulfate and derma tan sulfate
what are important proteoglycans in the basal lamina?
what are they important for?
perlecan and agrin
- agrin important as major heparin sulfate proteoglycan in the glomerular basement membrane
- sulfate groups charge keep proteins from leaking into the urine
why is syndecan important?
it is an integral membrane proteoglycan that links actin cytoskeleton to ECM molecules
-hydrophobic tail allows it to integrate into the lipid bilayer
what is fibronectin? what are the 2 types?
adhesive glycoproteins
-necessary for cells to attach and spread on a collagen substrate in culture
- its in the amorphous matrix
1) cellular: insoluble, occursin fibrils laid down by cells
2) plasma: very soluble, binds to fibrin and involved in blood clotting
what are integrins and why are they important?
they are receptors for firbonectin and other ECM proteins. they link the ECM to the cytoskeleton
what is laminin?
how does it bind?
large adhesive glycoprotein of basal lamina
- essential for epithelial cell function and polarity
- ** essential for epithelial cell differentiation
-binds epithelial cells to basal lamina via the integrins
what are the fibers of connective tissue? describe them
collagen: 1-20 um in diameter. made up of microfibrils
elastic: smaller in diameter than collagen, much longer, branched
- veerrry stretchy ( 5 x more elastic than rubber bands)
- consist of elastin protein
- form plates with walls of some arteries
histology: elastic fibers are thin and branched while collagen fibers are thick and ropy
reticular fibers: composed of type III collagen, small diameter and short. inelastic, but flexible.
-form stroma (supporting structure) of many soft tissues such as liver and spleen
