Seminar 3 ECM Flashcards
Definition of the extracellular matrix
A three dimensional network, which consists of proteins and carbohydrates and surrounds the cells of the connective tissues.
Components of ECM
- Basal membrane
- Interstitial matrix
+) Collagen
+) Proteoglycanes
+) Adhesive glycoproteins
Structure of collagens
- Repeating Gly-X-Y amino acid triplets (X is often: Pro; Y is often: Hydroxyprolin, Hydroxylysine)
- Cofactor of Prolil-hydroxylase, Lysil-hydroxylse: Vitamine C
- levorotatory alpha helix create one dextrorotatory triple helix
Function of collagen
providing the structure of the ECM
Identify 1 and 2
1 - Tropocollagen
2 - Procollagen
Identify 1 and 2
1 - Tropocollagen
2 - Procollagen
Describe Collagen macrostructure (monomers and interactions)
- Periodic organisation of collagen monomers
- Between monomers: cross-links, electrostatic and hydrophobic interactions
Name of this phenomenon
Cross-links in collagen
Cross-links can be formed between __
(3 pairs of AAs)
- Allysine – Lysine
- Allysine– Hydroxylysine
- Allysine – Histidine
Synthesis of collagen (8 steps)
- Synthesis of precollagen - RER
- Posttranslational modifications (Pro and Lys hydroxylation, Hydroxylysine glycosilation) - RER
- Synthesis of procollagen - RER
4-5. Translocation into Golgi, vesicule forming - Exocytosis into ECM
- Cleavage of procollagen (N-, C-peptidases)
- Creation of cross-links
Insufficient collagen synthesis
-> Name 2 diseases
- Scurvy
- Osteogenesis imperfecta
- Ehlers-Danlos syndrome
Causes of Scurvy
- Insufficient collagen synthesis
- Vitamine C deficit
- Defect in H bond and cross-link formation
Causes of Scurvy
- Insufficient collagen synthesis
- Vitamine C deficit
- Defect in H bond and cross-link formation
Symtomps of Scurvy
bleeding, muscle weakness, joint pain, gingivitis, acne, infectionsformation
Causes of Osteogenesis imperfecta
- Mutation of Type I. collagen
- Defect in triple helix formation
Symptoms of Osteogenesis imperfecta
bone and teeth developmental disorders, fragile bones, blue sclera
Insufficient collagen synthesis
-> Cause(s) of Ehlers-Danlos syndrome?
Lysil-hydroxylase mutation
Insufficient collagen synthesis
-> Symptoms of Ehlers-Danlos syndrome?
joint hypermobility, stretchy skin and tendons
Components of Proteoglycanes
- core proteins + glcosaminoglycane (GAG)
- Carbohydrate content: 95%
Structural features of proteoglycans
long, non branching, repetitve disaccharide units
Examples of glucosaminoglycane (GAG) in proteoglycans
chondroitin-sulfate, dermatan-sulfate, heparan-sulfate, hialuronic acid etc.
Function of proteoglycans
water retention, providing the volume of ECM
2 types of proteoglycans based on Localisation of proteoglycanes
- Matrix proteoglycanes
- Membrane-associated proteoglycanes
4 examples of matrix proteoglycans
- Aggrecan (cartilage)
- Perlecan (basement membrane)
- Versican (vessels)
- Biglycan
4 examples of membrane-associated proteoglycans
- Syndecan
- Glypican
- CD44
- Thrombomodulin
Components and structural features of Glycoproteins
- Carbohydrate content: 1-85%
- Branching structure
Function of glycoprotein
transmembrane receptors , ECM proteins
An example of glycoprotein
. Fibrillin-1
What happen if there is a mutation in . Fibrillin-1?
Marfan syndrome
Components of the basement membrane
- Type IV. collagen
- Proteoglycanes (perlecan)
- Adhesive glycoproteins
3 examples of Adhesive glycoproteins
- Laminin-1
- Nidogen
- Fibronectin
3 types of Epidermolysis bullosa
- Epidermolysis bullosa simplex (intraepidermal epithelial detachment)
- Junctional epidermolysis bullosa (lamina lucida detachment)
- Dystrophic epidermolysis bullosa (sub-lamina densa detachment)
2 enzymes that involve in ECM remodeling
- Matrix metalloproteinases (MMP)
- Tissue inhibitors of metalloproteinases (TIMP)
Characteristics of Matrix metalloproteinases (MMP)
- Zn2+ dependent endopeptidases
- Solubile or transmembrane types
Characteristics of Tissue inhibitors of metalloproteinases (TIMP)
- MMP:TMP = 1:1
- e.g. alpha-2-macroglobulin, RECK
Structure of matrix metalloproteinases
Common “minimal domain”:
- Signal sequence
- Prodomain
- Catalytic domain
Activation of matrix metalloproteinases
MMPs’ role in metastasis formation
- tumour formation, angiogenesis
- local invasion
- intravasation
- transport into circulation, adhesion in small vessels
- extravasation
- metastasis fomation and angiogenesis (colonisation)
Tumour and stroma
-> Cancer-associated fibroblasts (CAF) are formed in the presence of
- Growth factors: TGF-b, PDGF
- Inflammatory citokines: IL-6, IL-10, TNFa
- Originated from: tumour cells, fibrocyte, endothel, pericyte, adipocyte…
What is the Impact of cancer-associated fibroblasts (CAF)?
- Further growth of tumour cells
- Angiogenesis (VEGF)
- ECM remodeling
- Immune suppression
3 cell adhesion molecules in cell-cell connections
- Cadherins
- Immunglobulins
- Selectins
An example of cell adhesion molecules in cell-ECM connections
Integrins
Name 7 Activators of Tumour angiogenesis
1/ VEGF
2/ PDGF
3/ HIF-1
4/ TGF-b
5/ FGFs
6/ Angiopoetin 1
7/ MMP
Name 4 inhibitors of Tumour angiogenesis
1/ TIMP
2/ Thrombospondin
3/ Angiostatin
4/ Thrombostatin
4 steps of Wound healing and tissue regeneration
- Haemostasis (1-2. day)
- Inflammatory phase (1-2. day)
- Proliferation phase (2-10. day)
- Remodeling (1-12. month)
What do Throbocytes produce?
chemokins, PDGF, TGF-beta
Throbocytes produce: chemokins, PDGF, TGF-beta
-> The role of these molecules
- Leukocyta activation
- Fibroblast activation
Myofibroblasts – mechano-regulation
-> Identify
What does it mean if there is an Insufficient wound healing
When myofibroblasts do not die in apoptosis
-> May cause Hypertrophic scar and Keloid
What is Fibrosis?
Pathologic tissue regeneration
Where can fibrosis be present?
- Liver (cirrhosis)
- Kidneys
- Lungs
- Restenosis after PTA
etc.