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topic 13_rivier_252 - MCB 252 Topic 13 Cell Junctions...

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MCB 252 Topic 13 Cell Junctions Lodish 19.0 - 19.2 and 5.5
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Types of cell junctions First defined by EM I. Anchoring junctions: attach cells to each other or to extracellular matrix A. Adherens junctions: cell/cell via actin B. Desmosomes: cell/cell via IFs C. Hemidesmosomes: cell/ECM via IFs D. Focal adhesion: cell/ECM via actin
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Types of cell junctions II. Occluding junctions: function as barriers Tight junctions (zonula occludens) in vertebrates Septate junctions in invertebrates III. Communicating junctions Gap junctions Synapses (neurons) Plasmodesmata (plants)
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Lodish Table 19- 2
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Types of Anchoring Junctions Alberts 19-3
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Original description of junctional complexes in epithelia (Farquhar and Palade, 1963) By EM, characterized tripartite junctional complex in numerous different types of epithelial cells: mucosal epithelia of stomach, gall bladder, oviduct, uterus glandular epithelia of liver, pancreas, stomach, thyroid epithelia of pancreatic, hepatic, and salivary ducts, kidney Lodish, Fig. 6-5b
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Adherens junctions Extracellular adhesion molecules: Cadherins Linked to actin cytoskeleton via adaptor proteins (Lodish Fig. 19- 12) Alberts, et al. Fig. 19-15
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Proteins that link Cadherin intracellular domain to the actin cytoskeleton Lodish, Fig. 19-12
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Desmosomes Cell/cell adhesions via intermediate filaments Alberts, et al. Fig. 16-20 EM view
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Desmosomes What is the adhesion molecule? Clue came from autoimmune disorders: Pemphigus vulgaris, blistering of skin and mucous membranes http://tray.dermatology.uiowa.edu/PemVul01.htm Auto-antibodies disrupt adhesion between epithelial cells. (treat cells w/antibodies: lose adhesion) What is the antigen? How would you figure it out? Identified new Cadherin family member: Desmoglein 3 Pemphigus foliaceous: another auto-immune disorder leading to blistering of superficial epidermis Auto-antibodies directed against Cadherin family member: Desmoglein-1
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Desmosome structure Lodish, Fig. 19-14 Alberts, et al. Fig. 19-11
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Desmosome components Alberts, et al. Fig. 19-17 Extracellular adhesion molecules: Desmogleins and Desmocollins (the Desmosomal Cadherins) Intracellular domain binding proteins: Plakoglobin: similar to Beta-Catenin Plakophilin: similar to Gamma-Catenin Linkage between IFs and intracellular domain binding proteins: Desmoplakin
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Anchoring Junctions Tight junctions Gap junctions For Each Description What do they do?
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