Animal cell culturelecture -3-

Cell – matrix interaction

By: Saib H. Al OwiniFrom

Cell – matrix interaction

• The extracellular matrix, where most animal cells in tissues are embedded, fills the spaces between cells and binds cells and tissues together.

• The wide matrix in CT• May be calcified, transparent, liquid,• Matrix form basal lamina between CT and

Epith.

• Basal laminae is a sheetlike extracellular matrix that supports epithelial cells and surrounds muscle cells, adipose cells, and peripheral nerves.

• Matrix play more active and complex role in regulation the behavior of cells that contact it.

• Proliferation , migration, development, shape

and function.

• Extracellular matrix is made and oriented by cells within it.

• Extracellular matrices are composed of :

1- A gel-like polysaccharide ground substance—a design basically similar to that of plant cell walls.

2-Tough fibrous proteins .

1 -GlycosaminoglycansGAGs

• GAGs, are gel-forming polysaccharides of the extracellular matrix that consist of repeating units of disaccharides.

• Five major types, have Differences in: ( sulphate group and its location, linkage type).

GAGs

GAGs+protein=

• Proteoglycans are proteins linked to glycosaminoglycans and consist of up to 95% polysaccharide by weight.

• Eg ( aggrecan lage , decorine small)

• A number of proteoglycans interact with hyaluronan to form large complexes in the extracellular matrix.

GAGs function

1- GAGs act as filter gel• Heparan sulphat proteoglycans golmerular basal

lamina filter

2-Bind to growth factors AS stimulation of ( FGF)

3- Regulation of secretory proteins by :( immobilize, delayed, prolong action )

2-Tough fibrous proteins.

• Collagen, the major structural protein of the extracellular matrix, is the single most abundant protein in animal tissues.

• The collagens are a large family of proteins containing at least 27 different members

-Stiff -Long

-Triplehelix -With prolin and glycin-27 types the famous

-Type 1 in CT .

Elastin

• Elastic fibers, found in connective tissues, are particularly abundant in organs that regularly stretch and then return to their original shape.

• Elastin is cross-linked into a network by covalent bonds formed between the side chains of lysine residues and the protein that elastic fibers are principally composed of.

Matrix adhesion proteins

- The final class of extracellular matrix constituents, are responsible for linking the components of the matrix to one another and to the surfaces of cells.

• Fibronectin is the principal adhesion protein of connective tissues

1-Fibronectin

• Large glycoprotein • Dimer of tow lager subunits linked by disulfide

bond.

2 -Laminin ,

• BASAL LAMINA : • Flexible thin 40-120 nm • Influence cell metabolism • Induce cell differentiation • From the cells which set on . • tow layer ( from collagen , perelecan –

heparan sulphate proteiglycan-, laminin entactin )

• Laminin is the principal adhesion protein of basal laminae.

• Entactin, another adhesion molecule that is associated with laminins, binds to type IV collagen.

laminins

integrins

• Integrins are the major cell surface receptors responsible for the attachment of cells to the extracellular matrix.

• In addition to attaching cells to the extracellular matrix, integrins serve as anchors for the cytoskeleton.

integrins

• Focal adhesions are a type of cell-matrix junction that attach a variety of cells, including fibroblasts, to the extracellular matrix.

• The ability of integrins to reversibly bind matrix components is dependent on their ability to change conformation between active and inactive states.