ANHB3323 (9) - cell-cell interactions

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19 Terms

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2 Main ways animal cells are bound together

Epithelial cells:

  • Anchored cell to cell and cell to ECM

Mesenchymal cells (Cancer Type):

  • cell-ECM dominant

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Cell Junction types

1. tight junction

2. cell-cell anchoring junctions

3. channel-forming junctions

4. cell-matrix anchoring junctions

<p>1. tight junction</p><p>2. cell-cell anchoring junctions</p><p>3. channel-forming junctions</p><p>4. cell-matrix anchoring junctions</p>
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Tight junctions

seals gap between epithelial cells - prevent uncontrolled molecule movement

  • contain strands of transmembrane adhesion proteins

Proteins:

  • Claudin and Occludin

Mice with no claudin-1 gene

  • fail to make tight junctions = lose water rapidly

<p>seals gap between epithelial cells - prevent uncontrolled molecule movement</p><ul><li><p>contain strands of transmembrane adhesion proteins</p></li></ul><p>Proteins:</p><ul><li><p>Claudin and Occludin</p></li></ul><p>Mice with no claudin-1 gene</p><ul><li><p>fail to make tight junctions = lose water rapidly</p></li></ul><p></p>
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Gap Junctions - channel forming

Allows passage of small water-soluble molecules from cell to cell

  • connect cells electrically (ions) and metabolically (molecules)

  • Diameter of gap dictates size of molecules that can pass

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Gap junction structure

Connexins

  • 2 types of proteins that make up the channel

Connexon

  • Half og channel

  • Heteromeric (mix of the two types of connexins)

  • Homomeric (only one type of connexin)

Intercellular channel

  • both sides of the channel from each cell combines

<p>Connexins </p><ul><li><p>2 types of proteins that make up the channel </p></li></ul><p>Connexon </p><ul><li><p>Half og channel </p></li></ul><ul><li><p>Heteromeric (mix of the two types of connexins)</p></li><li><p>Homomeric (only one type of connexin)</p></li></ul><p>Intercellular channel </p><ul><li><p>both sides of the channel from each cell combines </p></li></ul><p></p>
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Cell-cell anchoring junction types

Adherens junction (actin filament)

Desmosomes (intermediate filaments)

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Adherens junction

connects actin filament bundle in one cell with that in the next cell

<p>connects actin filament bundle in one cell with that in the next cell</p><p></p>
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Adherens junction mechanism

Tension (extracellular) is required to expose the binding side of the actin fimalent and unfold the alpha-catenin molecule

  • allows for binding of vinculin

  • Junction is activated by tug of war tension between cadherins

<p>Tension (extracellular) is required to expose the binding side of the actin fimalent and unfold the alpha-catenin molecule </p><ul><li><p>allows for binding of vinculin </p></li><li><p>Junction is activated by tug of war tension between cadherins </p></li></ul><p></p>
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Desmosomes

connects the intermediate filaments in one cell with that in the next cell

  • utilise non-classic cadherin proteins

  • Connected to hemidesmosomes via intermediate filament

<p>connects the intermediate filaments in one cell with that in the next cell</p><ul><li><p>utilise non-classic cadherin proteins</p></li></ul><ul><li><p>Connected to hemidesmosomes via intermediate filament</p></li></ul><p></p>
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Desmosome elements and their protein types

Cytoskeleton→ Intermediate filament

Intracellular adaptor protein

  • plakoglobin, plakophilin, desmoplakin

Transmembrane Adhesion protein

  • desmoglein, desmocollin (non-classical cadherin proteins)

Extracellular Ligand

  • desmoglein, desmocollin

<p>Cytoskeleton→ Intermediate filament </p><p>Intracellular adaptor protein</p><ul><li><p> plakoglobin, plakophilin, desmoplakin </p></li></ul><p>Transmembrane Adhesion protein </p><ul><li><p>desmoglein, desmocollin (non-classical cadherin proteins) </p></li></ul><p>Extracellular Ligand </p><ul><li><p>desmoglein, desmocollin</p></li></ul><p></p>
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Cell-matrix anchoring junctions (types)

Actin linked cell-matrix junction

Hemidesmosome

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Actin-linked cell matrix junction

Anchors actin filaments in cell to extracellular matrix

Adhesion proteins:

  • Integrin heterodimer (with alpha (24) and beta (8) subunits)

Adaptor proteins:

  • Talin & Vinculin

<p>Anchors actin filaments in cell to extracellular matrix</p><p></p><p>Adhesion proteins:</p><ul><li><p>Integrin heterodimer (with alpha (24) and beta (8) subunits)</p></li></ul><p>Adaptor proteins: </p><ul><li><p>Talin &amp; Vinculin</p></li></ul><p></p>
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Hemidesmosome

Anchors intermediate filaments in a cell to extracellular matrix

adhesion proteins

  • Integrin a6B4 + Collagen XVII

adaptor proteins

  • BP230 + Plectin

<p>Anchors intermediate filaments in a cell to extracellular matrix</p><p>adhesion proteins</p><ul><li><p>Integrin a6B4 + Collagen XVII</p></li></ul><p>adaptor proteins</p><ul><li><p>BP230 + Plectin</p></li></ul><p></p>
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Transmembrane adhesion proteins

Go through the cell membrane to adhere to something outside

  • connects to intracellular adaptor proteins → which link to the filaments

(found in anchoring junctions, cell-cell or cell-ecm)

<p>Go through the cell membrane to adhere to something outside</p><ul><li><p>connects to intracellular adaptor proteins → which link to the filaments </p></li></ul><p>(found in anchoring junctions, cell-cell or cell-ecm)</p>
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Intracellular adaptor proteins

Connect the cytoskeleton filaments to the transmembrane adhesion membrane.

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cell-cell vs cell-ecm transmembrane adhesion proteins

Cell-cell = connect same kind of adhesion proteins

Cell-ECM = asymmetric

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Classical Cadherins - adhesion molecules

A transmembrane membrane adhesion protein

  • The extracellular part has 5 domains, separated by flexible hinge regions

  • Each hinge has calcium channels that create a velcro-like mechanism holding cells together

Present homophilic bonding which allows for sorting by types and level of expression

<p>A transmembrane membrane adhesion protein</p><ul><li><p>The extracellular part has 5 domains, separated by flexible hinge regions </p></li><li><p>Each hinge has calcium channels that create a velcro-like mechanism holding cells together</p></li></ul><p>Present homophilic bonding which allows for sorting by types and level of expression</p><p></p>
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What do Cadherins use to connect to cytoskeleton?

Catenins and Vinculin used to connect to actin filament

  • happens via force feeling upon homophilic binding

<p>Catenins and Vinculin used to connect to actin filament</p><ul><li><p>happens via force feeling upon homophilic binding</p></li></ul><p></p>
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Activation of integrin leads to...

intracellular signalling

(integrin beta subunit will be activated upon binding to ECM = recruits intracellular adaptor proteins)

<p>intracellular signalling</p><p>(integrin beta subunit will be activated upon binding to ECM = recruits intracellular adaptor proteins)</p>