Transcript The Extracellular Matrix - University of Central Oklahoma

The Extracellular Matrix
Michael Malahy
ECM in Epithelial Sheets
 3 types of molecules abundant in ECM

Proteoglycans


Collagen


Cushion cells and bind extracellular molecules
Mechanical strength and resilience
Multiadhesive Matrix Proteins

Bind and cross-link adhesion receptors and other
ECM components
Basal Lamina
 Type IV Collagen
 Trimeric, rod-like and globular, 2D
 Laminins
 Multiadhesive proteins that form 2D network with
collagen and bind integrins
 Entactin
 Rod-like, cross-link collagen and laminin and helps
incorporate other ECM components
 Perlecan
 Multidomain proteoglycan, binds and cross-links ECM
components and cell-surface molecules
Type IV Collagen
 Trimeric

Collagen α chains


1 or more 3-stranded segments



Homo- or heterotrimeric
Each strand is left-handed
3 strands twisted right-handed
Glycine, Proline and Hydroxyproline


Unusual abundance
Gly-X-Y
 Lysine and Hydroxylysine
Figure 6.14
Figure 6.16
Proteoglycans
 Membrane associated or secreted core
proteins covalently linked to GAG chains

Glycosaminoglycans (GAG)


Sulfated Disaccharides
Syndecans

Cell-surface
 Bind collagen, fibronectin and external signaling
molecules such as growth factors
 Regulate cellular metabolism and function
Fibrillar Collagens
 Produced largely by Fibroblasts
 Trimeric Type I Collagen Polymers

Fibrils
 Larger bundles

Fibers
 Form tendons

Gram for gram higher tensile strength than
steel
Fibronectin
 Multiadhesive matrix protein
 All isoforms from alternative splicing of RNA from a
single gene
 Essential for migration differentiation in
embryogenesis
 Promote blood clotting and facilitate migration of
immune cells to a wound
 Attach cells to ECM by binding fibrous collagen and
heparan sulfate proteoglycans to cell-surface
adhesion receptors such as integrins
Fibronectins cont’d
 Influence shape and movement of cells
 Influence organization of the cytoskeleton
 Dimer of 2 similar polypeptides


6 functional regions with ligand-binding
specificities
Each region contains certain repeating
sequences



Type I, II or III
Beads on a string
Arg-Gly-Asp

RGD sequence recognizes several integrins