the extra cellular matrix of cell

1. • Provides support anchorage and for cells.
• Regulates and determine cells dynamic behaviour :
- polarity of cells
- cell differentiation
- adhesion
- migration
• Provides mechanical support for tissues and organ architecture.
- growth
- regenerative and healing processes
- determination and maintenance of the
structure
• Place for active exchange of different metabolites, ions, water.
Function of ECM

2. EXTRACELLUJLAR MATRIX
The extracellular matrix (ECM) is the noncellular component present within all
tissues and organs, and provides not only essential physical
scaffolding for the cellular constituents but also initiates crucial biochemical and
biomechanical cues that are required for tissue morphogenesis, differentiation and
homeostasis
Cell adhesion to the ECM is mediated by ECM receptors, such as integrins, discoidin
domain receptors and syndecans
the ECM
directs essential morphological organization
and physiological function by binding growth
factors (GFs) and interacting with cell-surface
receptors to elicit signal transduction and
regulate gene transcription.

3. The
main fibrous ECM proteins are collagens,
elastins, fibronectins and laminins ..PGs
fill the
majority of the extracellular interstitial
space
within the tissue in the form of a
hydrated gel

4. • collagen
– the main ECM component, forms the main fibres
• elastin
• proteoglycans
- heteropolysacharides
• structural glycoproteins
- fibronectin, lamininaaaaa
Structure of ECM

5. • The most abundant protein in the body, making 25%-35% of all the
whole-body proteins.
• Collagen contributes to the stability of tissues and organs.
• It maintains their structural integrity.
• It has great tensile strenght.
• The main component of fascia, cartilage, ligaments, tendons, bone and
skin.
• Plays an important role in cell differentiation, polarity, movement
• Plays an important role in tissue and organ development
Collagen

6. Synthesis--fibroblasts

7. Formation of Collagen Networks
Fig. 19-52

8. Collagen is insoluble glycoprotein (protein + carbohydrate)
Collagen polypeptide structure:
- G – X – A – G – A – A – G – Y – A – G – A – A – G – X – A – G – A –
– A – G – X – A – G – A – A – G – Y – A – G – A – A – G – X – A – G –
– A – A – G – X – A – G – A – A – G – Y – A – G – A – A – G – X – A –
G - glycine, X - proline or hydroxyproline, Y – lysin or hydroxylysine, A – amino acid
• Proline and hydroxyproline constitute about 1/6 of the total
sequence, provide the stifness of the polypeptide chain.
• Carbohydrates : glucose, galactose
Collagen structure

9. Collagen Distribution
Type Molecule composition Tissue
Fibrilar Collagens
I [a1(I)2a2(I)] Skin, tendon,bone, ligaments, dentin
II [a1(II)]3 Cartilage, vitreus humor
III [a1(III)]3 Skin, muscle, blood vessels
V [a1(V)]3 Similar to type I, fetal tissue
Sheet-forming collagen
IV [a1(IV)2a2(IV)]
[a1(IV)a2(IV)a3(IV)] All basal laminaes

10. • Elastin is a major protein component of
tissues that require elasticity such as
arteries, lungs, bladder, skin and elastic
ligaments and cartilage.
• It is composed of soluble tropoelastin
protein containing primarily, glycine and
valine and modified alanine and proline
residues.
• Tropoelastin is a ~65kDa protein that is
highly cross-linked to form an insoluble
complex.
• The most common interchain cross-link in
elastins is the result of the conversion of the
amine groups of lysine to reactive aldehydes
by lysyl oxidase. This results in the
spontaneous formation of desmosine cross-
links.
Elastin

11. Proteoglycans
Proteoglycans represent a special class of glycoproteins
that are heavily glycosylated (95%).
They consisit of core protein with one or more attached glycosamino
glycan chain(s).

12. Function of Proteoglycans
• organize water molecules
- resistant to compression
- return to original shape
- repel negative molecules
• occupy space between cells and collagen
• high viscosity
- lubricating fluid in the joints
• specific binding to other macromolecules
• link to collagen fibers
- form network
- in bone combine with calcium
salts (calcium carbonate,
hydroxyapatite)
• cell migration and adhesion
- passageways between cells
• anchoring cells to matrix fibers

13. • Direct linkage to collagen or proteoglycans
- anchoring collagen fibers to cell membrane
- covalent attachment to membrane lipid
• Major adhesive structural glycoproteins
Structural Glycoproteins
(Adhesive glycoproteins)
• Extracellular
– Fibronectins
– Laminins
• Cell surface
– Integrins

14. Fibronectin Function
• cell adhesion
• cell differentiation
• anchoring basal laminae to other ECM
• blood clothing
- clothing process, link to fibrin

15. Fibronectin Structure
• Dimer connected at C-terminal by S-S linkage
• Rigid and flexible domains
• Cell binding domain RGDS
(arg, gly, asp, ser)
- binding receptor in cell membranes
• Domain is binding to
- collagen type I, II and III
- heparin sulfate
- hyaluronic acid
- fibrin

16. Laminin Structure
and Function
• cross-shaped glycoprotein
• 3 polypeptide chains
• domain bind
- collagen type IV
- heparin
- heparin sulfate
• cell surface receptor
• cell adhesion
• cell differentiation
• anchoring the glycoprotein to basal
laminae

17. What binds the cells to the ECM?

18. Integrins
• Groups of
transmembran
e proteins
• Link
cytoskeleton
to ECM
• Fibronectin
receptor is
best known