the extracellular matrix michael malahy. ecm in epithelial sheets 3 types of molecules abundant in...
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The Extracellular Matrix
Michael Malahy
ECM in Epithelial Sheets
3 types of molecules abundant in ECM Proteoglycans
Cushion cells and bind extracellular molecules Collagen
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
Homo- or heterotrimeric 1 or more 3-stranded segments
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
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