extracellular matrix Flashcards
extracellular matrix molecular structure: list the major components of the ECM, summarise their molecular characteristics and functional specialisation
properties of soluble extracellular matrix
contains large proteins, modular architecture, multi-adhesive so multifunctional
components of soluble extracellular matrix
glycoproteins, proteoglycans and glycosaminoglycan
examples of glycoproteins in soluble extracellular matrix
laminins, fibronectin
examples of proteoglycans in soluble extracellular matrix
decorin, aggrecan
where is laminin located
only in basement membranes as a sheet-like network
structure of laminin
3 a, B and y chains cross-shaped, forming a “coiled-coil”, with globular regions at the N-terminus
properties of laminin
very large and multi-adhesive, as different regions have different binding capacities with cell surface receptors
self-association with basement membrane
laminins, basement membrane matrix, collagen IV, proteoglycans
genetic diseases caused by laminin mutation
congenital muscular dystrophy. epidermolysis bullosa
chain mutation causing congenital muscular dystrophy
absence of a2 in laminin 2
consequences of congenital muscular dystrophy
weakness, joint deformities
fibronectin location
insoluble fibrillar matrix or soluble plasma matrix
fibronectin structure
V-shaped; 2 chain dimer connected by disulphide bridge
fibronectin derivation
derived from one gene with alternate mRNA splicing
properties of fibronectin
large and multi-adhesive, interacting with cell surface receptors and other matrix molecules
fibronectin function
regulates cell adhesion, migration in embryogenesis, tissue repair and wound healing
fibronectin in wound healing
forms mechanical continuum between EC collagen fiber with IC actin using integrin and adapter protein within the membrane
fibronectin necessity
no known mutations so essential for life
what is the fibronectin binding site for integrin
RGD molecule
define proteoglycan
core protein with 1 or more glycosaminoglycan chain covalently attached via link tetrasaccharide
define glycosaminoglycan
long, unbranched sugars with repeating disaccharides; 1 sugar is always amino; high -ve charge as sulfated/carboxylated
what do glycosaminoglycans form and significance
hydrated gels which occupy large volumes so are resistant to compression
families of proteoglycans
basement membrane, aggregating, small leucine-rich, cell surface
what proteoglycan is located at the basement membrane
perlecan
what proteoglycan is aggregating
aggrecans
what proteoglycan is small leucine-rich
decorin
what proteoglycan is located at the cell surface
syndecans I-IV
4 regions on proteoglycans
hyaluron, chondroitin sulfate/dermatan sulfate, heparan sulfate, keratan sulfate
hyaluron: structure, location of synthesis and properties
no core protein - just glycosaminoglycan chain; synthesised at cell surface not ER/Golgi; unsulfated and can be very large
decorin: function and absence
small; binds to collagen fibres; regulates size and arrangement of collagen fibre size; absence causes fragile skin and reduced tensile strength
what is embedded in the network of proteoglycans
type III cartilage matrix
which proteoglycan is abundant in hyaline cartilage
aggrecan
what regions are present in aggrecan
chondroitin sulfate and keratin sulfate
consequence of presence of negative chondroitin sulfate and keratin sulfate in hyaline cartilage
attracts osmotically active cations e.g. Na+, meaning large amounts of water retained, forming hydrated gel which, under compression, water is forced out from, before returning after compression relieved; cushioning effect at long bone ends
composition of aggrecan aggregates
aggrecan, hyaluronan and link protein
