Download Animal Cells

Cell Adhesion and
Communication
Shu-Ping Lin, Ph.D.
Institute of Biomedical Engineering
E-mail: [email protected]
Website: http://web.nchu.edu.tw/pweb/users/splin/
Date: 12.13.2010
Extracellular Matrix (ECM) –
Animal Cells
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What leads to the variety of the ECM?
 Different kinds of molecules; both proteins and
proteoglycans; ratio of different components
Besides providing stability to the physical structure of
tissues, why else is the ECM important to cell function?
 Influences migration and development of cells, cell
proliferation, cell shape
The ECM is usually associated with connective tissue. What
are some examples of connective tissue?
 Bone, ligaments, tendons, cartilage
Cell-cell and cell-substrate adhesion molecules (CAMs
and SAMs, respectively) are candidates for morphoregulators.
Soluble Ligand-ReceptorMediated Communication
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Cell-cell signaling carried out by soluble ligands is a prominent mode of
cell-cell communication in animals.
Common elements of all these signaling modes are signal-receiving
proteins or receptors, transducers and effectors
Ligand signaling:
 Endocrine signaling
 Paracrine signaling
 Autocrine signaling
http://www.ncbi.nlm.nih.gov/books/NBK28317/
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Endocrine signaling: hormones act on target cells distant from
their site of synthesis. In animals, blood transports hormones from
their sites of release to their targets.
Paracrine signaling: signaling molecules only affect cells in close
proximity  Conduction of electrical impulse from one nerve cell to
another and to muscle cell by neurotransmitters and neurohormones
Autocrine signaling: cells respond to substrates (growth factors)
that they themselves release, utilizing signal amplification component
of pathway to alter growth and differentiation. Tumor cells
overproduce and release growth factors that stimulate uncontrolled
growth.
http://www.ncbi.nlm.nih.gov/books/NBK28317/
Extracellular Matrix (ECM)
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Cells in multicellular organism are in contact with other cells or
with extracellular matrix (ECM).
2 fundamental types of ECM:
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3-dimensional matrix: completely surrounds cells and found
commonly in tissues such as bone, cartilage, and tendon, as well
as surrounding epithelial components of glandular organs such as
breast or prostate glands
2-dimensional basal lamina: interacts with basal surface of
all epithelia
Epithelial cells form sheets that contact one another at their
lateral borders and contact the 2-dimensional extracellular
matrix at basal surface.
2-dimensional basal lamina is in turn in contact with a 3dimensional ECM in which other cells are suspended.
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2D and 3D ECMs of animal cells are made up of 4 major components:
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Structural components, one or more members of collagen family, such as
fibrous collagens (type I, 3D ECM) and nonfibrous collagens (type IV, 2D ECM)
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Adhesive component responsible for interacting with cells and with other ECM,
glycoproteins – attach cells to matrix – fibronectins (3D ECM) & laminins (2D
ECM)
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Space fillers, such as sulfated and hydrated glycosominoglycans and
proteoglycans, heparin and heparan sulfate vary in their carbohydrate, sulfate,
and linker protein content from tissue to tissue.
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Elastic components such as elastin. These ECMs highly found in lungs is
continually exposed to stretching forces.
Modes of cell-ECM interactions.
Endothelial cells are deposited on
2D basal lamina surface,
migrating fibroblasts interact
with 3D matrix. Cell-ECM
interactions lead to imposition of
physical force onto cells. Figure
illustrates interaction of circulating
white blood cell with endothelial
cells by cell-cell adhesion, arrows
are direction of blood flow and
forces.
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Epithelial Cell Adhesion to Basal
Lamina – Cell Fate
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Cells in contact with ECM and with neighboring epithelial cells
are limited in their ability to proliferate.
Cells lose contact with other cells while adhering to ECM can
proliferate (a), whereas loss of attachment to ECM results
in apoptosis (b).
Many tumor cells do not undergo apoptosis when detached
from ECM and have subverted role of cell adhesion in
regulation of cell proliferation.
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Plants
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Cell Junctions Molecular Staples
Plasmodesmata
Animals
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Animal cells have no cell walls
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Some are surrounded by a
matrix of cell secretions and
other material
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Tight junctions
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Adherens junctions
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Gap junctions
plasmodesma
Animal Cell Junctions
free surface of
epithelial tissue
(not attached to
any other tissue)
examples
of proteins
that make
up tight
junctions
gap
junctions
adhering junction
basement membrane