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Gerald Karp
Cell and Molecular Biology
Fifth Edition
CHAPTER 7 Part 2
Interactions Between Cells
and Their Environment
Copyright © 2008 by John Wiley & Sons, Inc.
Integrins link ECM to cytoskeletons
• Focal adhesion (in vitro with actin)
• Hemidesmosomes (in vivo with keratin,
• Out-side-in
• Normal cells (integrin dependent) and
malignant cells (integrin independent)
Bullous pemphigoid
• Individual’s bp proteins (autoantibodies) present in
these adhesive structures.
• These autoantibodies cause the lower layer of the
epidermis to lose attachment to the underlying
basement membrane.
• The leakage of fluid into the space beneath the
epidermis results in severe blistering of the skin.
• Epidermis, GI, urinary tracts
7.3 interactions of cells with
other cells
• Cells can recognize the surfaces of other
• Interacting with some and ignoring
Little was known about the nature of the
molecules that mediate cell-cell adhesion
• The development of techniques for
purifying integral membrane proteins
• The isolation and cloning of genes that
encode these proteins
Four distinct families of integral
membrane proteins play a major role
in mediating cell-cell adhesion
• Cell-cell adhesion molecules
• 1. Selectins
• 2. Certain members of IgSFs and
• 3. Cadherins
• 4. Adherenes junctions and desmosomes:
anchoring cells to other cells
1. Selectins
• LEU-CAM1 (L-selctins)
in vivo: lymphocytes homing
• A family of intergral membrane
• Bind to the oligosaccharides of other cells
• Possess a small cytoplasmic domain and a
large extracellular segment
• Role of selectins in inflammation (P.263)
2. Immunoglobulins and integrins
• Ig domains: 70-100 amino acids
• Most IgSF mediate lymphocytes and
macrophages and target cells for immune
• Calcium-independent cell-cell adhesion
• Some IgSF such as VCAM, NCAM and L1
mediate interaction between nonimmune cells
i.e. nerve outgrowth, synapse formation,
nervous development
• Deformed babies due to L1 mutation, water on
the brain, mental retardation
• Integrins α4β1 binds to VCAM on blood vessels
3. Cadherins
• Transmit signals from ECM to the
• Mediate Ca2+-dependent cell-cell
• E-cadherins, N-cadherins, P-cadherins
4. Adherins junctions and
desmosomes: anchoring cells to other
• Adhesive junctions (ca2+dependent):
1.adherens junctions
3.junctional complexes (tight junction and
gap junction)