Download Extracellular Matrix of the Animal Cell

Extracellular Matrix of the
Animal Cell
What is the extracellular matrix
(ECM)?
• Something that is made by virtually all multi-cellular
organisms.
• Elaborate covering outside animal cell membranes,
occupying the space between cells. It is composed of:
– Collagen, proteoglycans, and fibronectin, which the
cell secretes.
– Different from the plant extracellular matrix, which is
composed of cellulose.
• Many ECM components are involved in cell-to-cell
interactions.
Components of the ECM
• Collagen
– Most abundant glycoprotein (about half of the total protein in the
body).
– Forms strong fibers outside of the cell.
• Fibers are embedded in a network made of proteoglycans.
• Proteoglycans
– Collagen fibers are embedded in a network made from
proteoglycans.
– Are another class of glycoproteins that consists of a small core
protein with many carbohydrate chains covalently attached.
– Large complexes can form when hundreds of proteoglycans
become non-covalently attached to a single long polysaccharide
molecule.
Components (cont.)
• Fibronectin
– Glycoprotein that attaches the ECM to the cell itself.
– Binds to cell surface receptors called integrins, which
are built into the plasma membrane of the cell.
• Integrins
– Cell surface receptor that connects to fibronectin,
which attaches to the ECM
– Span the membrane and bind on their cytoplasmic
side to associated proteins attached to microfilaments
of the cytoskeleton.
– Transmit’s changes between the ECM and the
cytoskeleton – it integrates changes occurring outside
and inside the cell.
Fig. 6-30
Collagen
Proteoglycan
complex
EXTRACELLULAR FLUID
Polysaccharide
molecule
Carbohydrates
Fibronectin
Core
protein
Integrins
Proteoglycan
molecule
Plasma
membrane
Proteoglycan complex
Microfilaments
CYTOPLASM
ECM Effect on Behavior
• By communicating with a cell through integrins, the ECM
can regulate a cell’s behavior.
• ECM can influence the activity of genes in the nucleus.
– Speculated that information probably reaches the nucleus by a
combination of chemical and mechanical signaling pathways.
• Mechanical includes fibronectin, integrins, and microfilaments of the
cytoskeleton.
• The cytoskeleton may then trigger chemical signaling pathways
inside the cell, leading to changes in the proteins being made by the
cell and therefore in its function.
• The ECM may help coordinate the behavior of all the
cells within that tissue.
– Direct connections (intercellular junctions) between cells also
function in this coordination.