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Cells into Tissues
By Kevin Huyen
6.1 Cell-Cell and Cell-Matrix Adhesions
• Cell-adhesion molecules (CAMS) mediate direct cell-cell adhesions
• Cell-surface adhesion receptors mediate cell-matrix (ECM)
adhesions.
These interactions bind cells into tissues and facilitate communication
between cells and their environment
6.2 Junctions & Adhesion Molecules
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Three major classes of cell
junctions that assemble cells into
sheets and mediate
communication between them.
1. Anchoring Junctions
2. Tight Junctions
3. Gap Junctions
Anchoring Junctions
Are specialized regions of the
cell surface containing CAMs
or adhesion receptors that
interact with other cells, the
ECM, or cytoskeletal fibers.
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Two Major Types:
Mediate cell-cell adhesion
Adherens junctions
Desmosomes
Mediate cell-matrix adhesion
Hemidesmosomes
Tight Junctions
Type of cell-to-cell junction that prevents diffusion of
macromolecules and many small molecules and ions in
the spaces between cells. Specifically, they limit and
regulate the extracellular flow of water and solutes.
Gap Junction
 Permit the rapid diffusion of small, water-soluble
molecules between the cytoplasm of adjacent cells.
Overall Scheme
of the 3
Junctions
6
Major Families of CAMs
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•
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Cadherins
Ig (immunoglobulin) super family
Selectins
Mucins
Integrins
Cadherin Family
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Found in Adherens junctions and
desmosomes
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Cadherins are key molecules in
cell-cell adhesion and cell
signaling.
Adheren Junction
Desmosomal Cadherins
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Contain two specialized
proteins
1) Dismoglein
2) Dismocollin
Selectins
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Family of CAMs that mediate
leukocyte-vascular cell
interactions.
Extravasation of leukocytes
require the successive
formation and breakage of cellcell contacts between
leukocytes in the blood and
endothelial cells lining the
vessels
Blood
Sialyl
Lewis-x
antigen
Sugar binding
lectin domain
P-selectin
Endothelial cell
Purpose of Selectins
Integrins
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A large family of alpha beta heterodimeric cell surface
proteins that mediate both cell-cell and cell-matrix
adhesions
Integrins typically exhibit low affinities for their ligands
IIb3 integrin
platelet
*Accelerates a
formation of clotting
Collagen or
factors
thrombin
Conformational change of IIb3 integrin
platelet
Fibrinogen
Activated platelet
Summary
Cell to cell contact through
cell adhesion molecules or
adhesion receptors
Summary (continued)
3 types of specific
types of adhesions
called Junctions are:
Anchoring
Tight
Gap