The extracellular matrix
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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

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The Extracellular Matrix

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The extracellular matrix

The Extracellular Matrix

Michael Malahy


Ecm in epithelial sheets

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

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

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 6.14


Figure 6 16

Figure 6.16


Proteoglycans

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

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

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

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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