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Chapter 18 PowerPoint Presentation

Chapter 18

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Chapter 18

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  1. Chapter 18 • Cell Junctions, Cell Adhesion, and the Extracellular Matrix

  2. A cross-sectional view of part of the wall of the intestine Cell junctions to adjacent cells or Basal lamina Rich in ECM

  3. Cell junctions: Occluding junctions--seal cells together, prevent even small molecules from leaking from one side of the sheet to the other; Anchoring junctions--mechanically attach cells and their cytoskeleton to their neighbors or to the extracellular matrix; Communicating junctions--mediate the passage of chemical or electrical signals from one interacting cell to its partner

  4. The role of tight junctions in transcellular transport The structure of a tight junction Diffusion barrier Sealing strands: a long row of transmembrane adhesion proteins Claudins Occludins ZO (zonula occludens): anchor the strands to actin cytoskeleton

  5. Septate junctions: occluding junctions in invertebrates More regular a structure A continuous band around each epithelial cell Parallele rows of junctional proteins:regular periodicity Discs-large in fly in related to ZO

  6. Anchoring junction:connecting cytoskeleton to a neighbor or to the ECM Adherens junctions and desmosomes: among cells-cadherins Focal adhesions and hemidesmosomes-integrins Actin filaments Intermediate filaments

  7. Adherens junctions Actin bundles are linked via the cadherins and anchor proteins into an extensive transcellular network Adhesion belt contractile

  8. Desmosomes connect intermediate filaments from cell to cell Buttonlike Pemphigus: autoimmume disease-antibodies bind to and disrupt the desmosomes-blistering of the skin with leakage of body fluid into the loosened epithelium

  9. Focal adhesion actin vinculin Muscle cells attach to their tendons this way

  10. Desmosomes and hemidesmosomes integrins

  11. Gap junction Gap! Electrical and chemical coupling

  12. Summary of cell juctions in a vertebrate epithelial cell

  13. Plasmodesmata are the plant gap junctions Plant don’t need anchoring junctions

  14. Cells assemble to form a tissue

  15. The structure and function of cadherins Calcium-dependent Homophilic

  16. E-cadherin N-cadherin Cadherin-7 in ganglion cells from neural crest cells

  17. Three ways cell-surface molecules can mediate cell-cell adhesion Cadherin-dependent cell sorting

  18. Selectins mediate transient cell-cell adhesions in the bloodstream Calcium-dependent Carbohydate-binding proteins (lectins) Binding of white blood cell to endothelial cells

  19. Immonoglobulin superfamily proteins mediate Calcium-independent cell-cell adhesion

  20. Summary of the junctional and nonjunctional adhesive mechanisms

  21. The repeating disaccharide sequence of dermatan sulfate glycosaminoglycan (GAG) Negatively charged ECM: polysaccharide chains GAGs linked to protein(proteoglycans) And fibrous proteins (collagen, elastin, fibronectin, laminin)

  22. A model of the molecular structure of a basal lamina

  23. Dog aorta Covalent bonds Stretch and recoil like a rubber band Five times more extensible

  24. Plant cell walls are made of polysaccharide cellulose, the most abundant organic macromolecule on earth Long unbranched chains Of b1,4-linked glucose uints

  25. Summary Three types of cell junctions: structure and function Cell adhesion has important role in development and function Two main types of ECM molecules: proteoglycans and fibrous proteins