Lecture 19 (Oct 12)

Lecture 19 (Oct 12) - Biological Sciences 110A:...

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Lecture 19: Intercellular interactions  Overview of types of cell-cell junctions  Cadherins: homophilic adhesion molecules  Adherens junctions: adhesion belts  Desmosomes: “spot-weld” junctions  Tight junctions: diffusion barriers  Gap junctions: direct communication  An overview of cell-cell communication Biological Sciences 110A: Introduction to Biology Kendal Broadie Reading in Chapter 7 (254-271) Karp
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Inside or out? Epithelia provide an interface between an organism  (animal) and its environment Epithelial cells are linked by cell junctions and attached underlying basal lamina
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Epithelial cells are linked to each other by intercellular junctions Types of intercellular junctions include :      1. adhering junctions (adherens and desmosomes)      2. occluding (tight) junctions      3. communicating (gap) junctions See Fig. 7.25 Karp
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Cadherin-family adhesion proteins link the cytoskeleton of  adjacent cells Cadherins  are transmembrane proteins. Their extracellular domains bind each other with high  affinity ( homophilic adhesion ). Their intracellular domains bind  linker proteins  (e.g.  α  and  β   catenins) that bind the  cytoskeleton . Thus, cadherin proteins “bridge” the cytoskeletons of cells  providing a strong linkage either during development/movement (transient) or mature tissues  (permanent). See   Fig.  7.21, 7.22,  7.23 Karp
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An example of transient cadherin-mediated adhesion during  nervous system development Neural folds (N-cadherin) Ectoderm (E-cadherin) Neural tube (N-cadherin) Ectoderm       (E- cadherin) Somites  (fibronectin) Gilbert Developmental Biology Figure 7.8 See Fig. 7.24 Karp
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In adherens junctions, cadherins link actin filaments in adjacent cells  to form permanent connections Adherens junctions  link actin  filament arrays ( adhesion belts that provide the primary  connective strength in many  tissues  
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Desmosomes link keratin intermediate filaments in adjacent cells via  Cadherin-family adhesion proteins
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Lecture 19 (Oct 12) - Biological Sciences 110A:...

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