ECM Flashcards
What is ECM
Acellular component of present in all tissues and organs
list the 2 main types of ECM
Interstitial connective tissue matrix
Basement membrane
What are the components of ECM
Fibres: elastin + collagen
Ground substance: Glycosaminoglycans + Proteoglycans + Glycoproteins
List places where ECM is found
Bone Cartilage tendons blood vessel walls subcutaneous fat basemen membrane dermal layer of skin cornea
Describe what collagen is and its structure
a large, insoluble, fibrous protein
made up of 3 collagen polypeptides which form a triple helix structure
What assembles collagen molecules into its strong helical structure?
presence of Gly(cine)-X-Y repeat motif
what are the two types of collagen, what cartilage are they present in and what functional property do they have
Fibrillar: found in type 1 and 2, provides strength. Found in skin, tendon, bone
Sheet/network forming: found in type 4, provide support and filter. Found in basement membrane.
Where is type 1 collagen found?
bone, tendon, skin (dermis), ligaments
Where is type 2 collagen found?
Hyaline cartilage
Where is type 3 collagen found?
granulation tissue, liver, bone marrow, lymphoid organs
Where is type 4 collagen found?
basement membrane
Where is type 5 collagen found?
linker to Basement membrane, in cornea
describe elastin, how is it arranged and what property does it have?
elastin is a structural protein arranged as fibres.
It is found in tissues which need stretch and recoil properties
What is needed to assemble elastin?
A structural glycoprotein called Fibrillin
What organs in elastin found in?
Lungs, skin, blood vessels, bladder
what is ground substance?
An amorphous (shapeless), colour, gelatinous material. It is found in the space between cells and fibres.
What forms a proteoglycan
A core protein and many GAGs
what does ground substance consist mainly of?
water
what is another name for GAGs
mucopolysaccharides
list the four different types of GAG and where they are found
hyaluronic acid - found in synovial fluid
keratAn sulphate - found in cartilage
HeparAn sulphate - found in basement membrane
chondroitin sulphate - found in cartilage
what properties do GAGs have?
They are hydrophilic so absorb water.
They provide cushioning and have hydrating properties.
They enabled ECM to withstand high compressive forces.
what are proteoglycans also known as?
mucoproteins
proteoglycans are mostly what?
carbohydrates (90-95%)
list 4 types of Proteoglycans
Aggrecan
perlecan
Syndecan
Decorin
where is aggrecan found and what type of GAG is present?
In cartilage
Chondrotiin sulphate + KERATAn sulphate
where is perlecan found and what type of GAG is present?
in basement membrane
HepAran sulphate
where is syndecan found and what type of GAG is present?
in cartilage
Chondroitin sulphate + heparan sulphate
where is decorin found and what type of GAG is present?
widespread in connective tissues
Chondrotiin sulphate
Dermatan sulphate
list 5 glycoproteins
fibrillin fibronectin entactin tenascin laminin
what is the role of fibronectin?
found in basement membrane
attaches to integrins and creates a provisional matrix for keratinocytes to move along to close the wound
what makes the protein/fibres in the ECM?
Fibroblasts
what is collagen synthesised as, what post translational modification does it undergo and what is the protein assembly?
Procollagen
Glycosylation + hydroxylation
Triple helix
what is elastin synthesised as, what post translational modification does it undergo and what is the protein assembly?
tropoelastin
hydroxylation
fibrillin scaffold
cross linked fibres
how are proteoglycans synthesised?
core protein is made on rER
Addition of carbohydrates in Golgi apparatus
delivered to extracellular component by exocytosis
assembled with other ECM components by fibroblasts
If the ECM is never static what may it be undergoing?
Deposition
Degradation
Modification
how is ECM degraded when it is remodelled? wen may it need to be degraded for remodelling?
Broken down by proteases, MMPs, and elastase
Used for wound repair, embryogenesis and angiogenesis
how do pathogens degrade ECM? give an example pathogen
pathogens secrete collagenase which enables them to invade the host.
e.g. bacillus cereus
what are matrix metalloproteinases?
enzymes which break down proteins found in the ECM and need calcium and zinc to function
what is the basement membrane
a thin tough sheet of ECM
What are components of the busmen membrane ?
Collagen type 4 perlecan (PG) laminin (GP) entactin (gp) fibronectin (gp)
what are the 3 layers of the ECM?
Lamina lucida
Lamina densa
Lamina fibroreticularis
list some BM disorders
cancer
epidermolysis bullosa
goodpasture syndrome
Diabetes mellitus
Describe goodpastures syndrome
autoantibodies fo collagen type 4 destroy the BM in glomerulus and lung.
What is osteoid, how is it made and degraded?
ECM in bone. It forms the organic, unmineralised portion of bone matrix
It is made by osteoblasts and degraded by osteoclasts
what is the eCM in joints?
cartilage
what is the ECM in joints (cartilage) composed of ?
collagen type 2 aggrecan chondroitin sulphate Keratan sulpahte hyaluronic acid
give an example of a disease when elastin in ECM is damaged
Supravalvular Aortic Stenosis
give an example of a disease when Fibrillin-1 in ECM is damaged
Marfan Syndrome: skeletal, ocular & cardiovascular abnormalities
give an example of a disease when collagen in ECM is damaged
Ehlers-Danlos Syndrome: joint & skin abnormalities e.g. hypermobility, stretchy skin
give an example of a disease when keratin sulphate in ECM is damaged
Macular corneal dystrophy: corneal transparency
give an example of a disease when perlecan in ECM is damaged
Dyssegmental dysplasia Silverman-Handmaker : severe form of neonatal lethal dwarfism
