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Unformatted text preview: Cell adhesion and extracellular matrix Integrating cells into tissues Cells Tissues: epithelial, connective, muscle, nervous and blood Organs: e.g. heart, brain, liver, lung, kidney, etc.... Whole body Two main ways in which animal cells are bound together: 1) Extracellular matrix 2) Cell-cell adhesions Overview of cell-cell and cell-matrix adhesions Four types of cell adhesion molecules Model for generation of cell-cell adhesions E-cadherin mediates Ca2+ dependent adhesion E-cadherin mediates cell-cell adhesion Intergrins Cell adhesion mediated cell-cell interactions Fibronectin plays a role in development ECM and in mouse development Intergrin plays a role in signaling Intergrin activation Four types of epithelia Functions of cell junctions 1. bind cells together to form tissues 2. water and salt-tight seal between cells 3. metabolically or electrically couple cells 4. anchor cells to ECM Cell junctions between epithelial cells Proteins in an adherin junction -Catenin and the Wnt signaling E-cadherin and cancer Desmosome Desmosome associated with hemidesmosome Tight junction Tight junction Occludins in tight junction Tight junctions prevent passage of large molecules Tight junction, polarity and transepithelial transport Gap junctions Gap junction
Hexagonal cylindrical particles that compose pores connecting the cytoplasms of adjacent cells. Pore size: 1.2 nm in diameter Composed of connexins (vertebrate, 12 homo- or hetero- connexins per channel, 6 per cell), innexins (invertebrate), or pannexins (both) Allows molecules smaller than 1.2 kD to pass (ions, vitamins, signaling molecules, small peptides, etc.) Permeability can be regulated by pH, Ca2+ concentration and connexin phosphorylation. In heart, for example, Ca2+ diffusion through gap junctions is important for coordinate contraction Mutations in the connexin genes cause 8 human diseases, such as neurosensory deafness. Gap junctions ...
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