Cell-matrix interactions Flashcards
Label this extracellular matrix
Label the different cells of the body;
Tell me about collagens?
What its role is?
Where it is present?
- most abundant protein in the body
- major structural protein
- exists in fibrils or is associated to fibrils or in sheets
- most cells are within a collagenous matrix
Whats the typical sequence of Collagens?
Gly-X-Y (X,Y often lysine or proline)
many prolines and lysines converted to the -OH form
What does fibrillar collagens include?
Collagens I, II and III
Are Fibrillar collagens strong ?
They are very strong and resilient to stretching
How are Fibrillar collagens packed together?
- Loose connective tissue (more random)
- Dense connective tissue (reguarly packed into sheets)
Tell me the steps to the synthesis of the pro-alpha chain
Tell me about collagen molecules half lives?
They have a long half life (10 yrs +)
Where is collagen degraded/ reformed?
At points of stress, healing, growth and cell infiltration
What are MMPs?
Where are they released?
What do they regulate?
MMPs: Matrix Metalloproteinases
Released by cells as they migrate through connective tissues
Regulate the breakdown of collagenous matrix
What is scurvy caused by?
When are defects seen?
Scurvy is an Ascorbic acid deficiency
Defects are seen where there is a high turn over of collagen (cofactor for lysine and proline hydroxylase- needed for collagen crosslinks)
In its absence collagen trimers and fibrils are less stable. what structures see this weakness?
- Gums
- nail beds
- Poorly healing wounds and bruising
What does elastin provide?
Strength and resistance
What are elastic fibres formed from and what are they laid around?
Elastic fibres are formed from the polymer Elastin (monometic tropoelastin) and are laid around microfilaments of fibrilin
How are elastic fibres connected?
They are cross-linked to each other through similar lysine linkages as in collagen
What does elastin lack and what determines its behaviour?
Elastin lacks a defined structure but is highly hydrophobic giving random coils, hence behaviour
When does elastin synthesis occur?
What does this mean?
Synthesis of Elastin occurs in foetus and childhood and is limited later in life
Hence wrinkling of aging skin and loss of lung function with time
What is elastase secreted from?
Neutrophils
Elastin is not replaced after inflammation, instead what is used and what does this result in?
Instead collagen is layed down- this results in fibrosis and scarring
What do Proteoglycans provide?
Strength by water retention
they are resistant to compression (alters charge density on pressure)
Tell me about Proteoglycans protein core?
Has highly charged sugars attached, which attracts H2O and Na+ ions and forms a hydrated porous gel
Whats do hydrated gels allow?
motion of nutrients and waste products about isolated cells e.g. Chondrocytes
What does the high charge of proteoglycans provide?
give examples
Acts as a binding site for many moleucles
Example:
- Growth factors (FGFs)
- Cytokines (TGFb)
