Extracellular Matrix Flashcards
What is the extracellular matrix:
An extracellular space filled with a network of macromolecules
Tissue organisation
In epitheal: there is a thin layer of ECM with tightly bound cells (mechanical stresses transmitted cell to cell here)
In connective tissue: there is alot of componentslike collagen fibers with few cells like fat cells immune cells (mechanical stresses transmitted directly to matrix here)
Tissue organisation
In epitheal: there is a thin layer of ECM with tightly bound cells (mechanical stresses transmitted cell to cell here)
In connective tissue: there is alot of componentslike collagen fibers with few cells like fat cells immune cells (mechanical stresses transmitted directly to matrix here; it helps resistance to compressive forces (elasticity) and strength
Types of connective tissue
Tendon - ropelike, high tensile strength (collagen fibrils)
Blood vessel walls – resilient, flexible (elastic fibres)
Cartilage – tensile strength and elastic properties (collagen and proteoglycan aggrecan)
Bone – rigid and incompressible (calcified collagen)
Vitreous content of eye - transparent jelly (collagen fibres and hyaluronan
What are the TWO components of the matrix?
1) Glycosaminoglycans (GAGS) - linked to protein, ie a proteoglycan
2) Fibrous proteins like collagen
What is fribrinogen an example of?
adhesive glycoproteins which act as adapters, providing molecular interactions by binding matrix proteins, cells or both
Describe GAGS?
1) UNBRANCHED polysaccharide chains made up od wo sugar repeats (disaccharides - aminosugar and uronic sugar.
It is highly negative due to carboxyl groups and so water is attracted to them (water reabsorption)
It has four main groups.
An example of GAG is Hyaluronan
This has a long chainacting as a NON OMPRESSIBLE SPACE FILLER
It makes pressure by attracting water
What is the structure of a protoglycan eg, betaglycan, aggrecan in cartilage
GAG attached to a link tetrasaccharide with is atached to the serine of a protein via the glycsyl transferase in E.R
What is major fibrous extracellular matrix component?
Collagens. (in skin and bone) various forms expressed in different tissues.
Some form fibrils in connective tissue via INTRERMOLECULAR COVALENT CROSS LINKS (lysines and hydroxysines)
Describe the structure of collagen.
alpha chains form trimers of three tightly bound chains
chains fold into a helix with 3 aa per turn.
Trimers to fibrils to fibers
Describe the structure of collagen. (5 fibril forming types)
alpha chains form trimers of three tightly bound chains
chains fold into a helix with 3 aa per turn.
Trimers to fibrils to fibers
How do Fibril-associated collagens compare to normal ones?
don’t form fibrils
- non-helical domains interrupt triple helix, making molecule more flexible
- retain propeptides, so don’t aggregate into fibrils
bind to fibrils of fibrillar collagens
- mediate fibril interactions with each other and with other ECM molecules to determine fibril organisation
Describe elastin.
- hydrophobic protein
- secreted as tropoelastin, then highly CROSSLINKED to form network of fibres and sheets
elastic fibres also covered in MICROFIBRILS – made from other glycoproteins e.g. fibrillin
Describe elastin.
- hydrophobic protein
- secreted as tropoelastin, then highly CROSSLINKED to form network of fibres and sheets
elastic fibres also covered in MICROFIBRILS – made from other glycoproteins e.g. fibrillin
forms elastic fibers for resilliance.
What is fibronectin?
a complex that forms DIMERS of functional domains showing different adhesive functions to bind to cells and COLLAGEN
What is the basal lamina?
very thin, tough, flexible sheet of ECM that underlies epithelia, kidney glomerus, surrounds muscle and nerve cells used for connecting epidermis to dermis.
It is needed for polarisation.
roles of basal lamina
physical support
selective cell barrier
filtration
act as template for tissue regeneration
determine cell polarity
influence cell metabolism
organises plasma membrane proteins
promote cell survial
What is used to modify this structure?
Nidogen and periecan
What is Laminin?
A complex consisting of a heterotrimer alpha, beta and gamma chains which binds to cells and binds layers together
List some cells found in the matrix and their effect on its orgainsation.
fibroblasts, chondroblasts (cartilage), osteoblasts (bone)
not only secrete but orientate/remodel the matrix by pulling fribers; they aplly tenion via the INEGRINS on the lamin.
This allows wound healing, development, migration
What is MMP?
a cellular protease : matrix metalloproteases that can degrade the ECM allowing for removal of invaders.
Summary of ECM roles
structural integrity of connective tissues
scaffold for cells
pool of growth factors and cytokines
provides pathways for cell migration
regulates cell shape, polarity, survival, proliferation and function
regulates tissue development
What is ECM made of?
made of polysaccharides (GAGs), which can be in the form of proteoglycans, fibrous proteins and adhesive glycoproteins
secreted and remodelled by cells within the ECM
