Extracellular matrix

What is the extracellular matrix?

Network of secreted macromolecules that determines the physical properties of tissue

Influences: cell shape, migration, proliferation, function and development

What are collagens?

Most abundant animal protein

High tensile strength, triple helix structure of 3 alpha chain polypeptides

amino acid of glycine-x-y

resist tension

formed from collagen fibrils to collagen fibres

What effect does fibril-associated collagen have?

influence fibrillar collagen arrangement

What are glycosaminoglycans?

polysaccharides linked to proteins (proteoglycans)

GAG chains produce hydrated space as hydrophilic

resists compression

What is hyaluronan?

most simple evolutionary form of GAGs

present in all tissues

example of an atypical GAG as perfect disaccharide repeats, no covalently bound proteins, synthesised at membranes

space filler and lubricant

What is fibronectin?

glycoprotein

binds intern receptors and ECM components

adhesion, migration and growth

Functions of proteoglycans?

Regulate activity of signalling molecules

Act as co-receptors, by localising signalling molecules and facilitate signalling

Regulate activity by binding to proteolytic enzymes or inhibitors which allows regulation of tissue

example is metalproteinase

What is the basal lamina?

Specific extracellular matrix where tissue have junction with connective tissue

Underline all epithelia

separates cell layers, acts as scaffold to regenerate cells and as a selective molecular filter

What are the three cell junction types?

Two categories of cell-cell and cell-matrix

tight junctions seal cells into junctions and prevent leakage of molecules

Anchoring junctions attachment of cells to neighbours or to the ECM

Gap junctions allow chemicals to pass and electrical signals

What is the structure of tight junctions?

Encircle epithelial cells

split cell into apical surface and basolateral

What is the structure of anchoring junctions?

Actin-dependent or intermediate filament dependent

contains intracellular attachment protein and trans-membrane linker proteins

either cell-cell adherent, cell-matrix adherens or cell-cell/cell-matrix(desmosome/hemidesmosome)

at cell-matrix adherens actin terminates at focal adhesions and interns act as linker

How do gap junctions work?

widespread and have channel-forming proteins

allows passage of small water soluble molecules, inorganic ions which allows metabolic/electrical coupling between cells

either electrically excitable cells which facilitate signals and synchronise cell populations

Non excitable cells share nutrients and coordinate development