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BIOL 3800: EXTRACELLULAR MATRIX
How epithelial tissue and/or connective tissue is formed.
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cells interact with extracellular material to form defined tissues. |
glycocalyx |
a cell coat formed from carbohydrate projections from the plasma membrane.
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The glycocalyx mediates...
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cell-cell and cell-substratun interactions
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Extracellular Matrix (ECM)
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organized network beyond the plasma membrane
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Extracellular Matrix (ECM) determines...
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shape and activities of the cell
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Basement Membrane (Basal Lamina)
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continuous sheet that is under the epithelial tissue.
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Locations of Basement Membrane (Basal Lamina)
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surrounds blood vessels, nerve fibers, and fat cells.
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Function of Basement Membrane
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1. maintain cell attachment
2. serves as substratum for cell migration
3. Serves as a barrier to macromolecules
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4 Components of Extracellular Space
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1. Collagen
2. Proteoglycans
3. Fibronectin (Fn)
4. Laminins
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Collagen |
Fibrous glycoprotein only found in the Extracellular Matrix.
note: Collagen Type iV is non-fibrillar
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Properties of Collagen
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-most abundant protein in body
-high tensile strength
-trimer polypeptidie wound around one another
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Diseases resulting from improper collagen formation
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Osteogenesis imperfecta- mutation in gene that produces collagen
EhlerDanlos Syndrome- mutations in collagen gene
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Proteoglycans |
protein-polysaccharide complex with core protein attached to glycosaminoglycans (GAGs)
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Properties of Proteoglycans
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-repeating disaccharide structure
-negatively charged GAGs attract lots of cations which in turn attract h2o which makes a porous hydrated gel
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Fibronectin (Fn)
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a linear array of distinct polypeptides giving it a modular structure
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Properties of Fibronectin (Fn)
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-each polypeptide is approx. 30 Fn module
-Fn has binding site for other components of the ECM
-Fn guides migrating cells during embryogenesis
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RGD Loop
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component of a fibronectin structure
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Laminins |
extracellular glycoproteins that consist of three polypeptide chains linked by disulfide bonds.
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Properties of Laminins
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-help cell migration during development
-component of basement membranes (basal lamina)
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Properties of Extracellular Matrix
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-can be stretched during tension
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Matrix Metalloproteinases (MMPs)
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Proteins that can degrade materials of the ECM
-can possibly be involved in tissue remodeling, embryonic cell migration, cell healing, and formation of blood vessels
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Extracellular Materials that Interact with Cells
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1. Integrins
2. Focal Adhesions
3. Hemidesmosomes
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Interactions of Cells with Other Cells
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1. Selectins
2. Immunoglobulin Superfamily (IgSF)
3. Cadherins
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Hemidesmosomes
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basal attachments of epithelial cells to the basement membrane in vivo.
-contain dense plaque with filaments made of keratin which are linked to ECM by membrane spanning integrins
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Focal Adhesions
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scattered discrete site for cell adhesion to their substratum in vitro.
-help in cell movement
-contain integrins which are attached to intracellular contractile machinery
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Bullous Pemphigoid
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autoimmune disorder when antibodies are produced against the proteins forming extracellular parts of hemidesmosomes.
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Selectins |
integral membrane glycoproteins that bind to sugars on the surface of a cell
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3 Types of Selectins
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1. E-selectin-- found on endothelial cells
2. P-selectin-- found on platelets and endothelial cells
3. L-selectin-- found on white blood cells
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Immunoglobulin Superfamily (IgSF)
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mediate interaction of lymphocytes with cells required or immune response.
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Cadherins
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glycoproteins that mediate Ca2+ dependent cell-cell adhesion
-also involved in transmision of signals from ECM to cytoplasm
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Epithelial-Mesenchymal Transition (EMT)
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molecules formed by Cadherins that mediate many changes in adhesive contacts during embryonic development
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Adherens Junctions
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"belts" formed by Cadherins near junctional complexes
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Desmosomes
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disk-shaped linkages between cells
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Transmembrane signaling
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transfer of information across a plasma membrane
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Action of binding an integrin and its ligand induces...
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responses such as changes in growth potential
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Metastasis
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spread of a tumor to other parts of the body
-metastatic cells are less adhesive, able to invade normal cells, and can cross many barriers
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Tight Junctions
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adhesions between specific contacts between epithelial cells
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Gap Junctions
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sites between animal cells for intercellular communication
-composed of proteins called connexin
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