Lecture 9 - Connective tissue/ECM Flashcards
What are the major types of animal tissue? and what levels of cell-cell contact do they have?
Epithelial, Muscle, Nervous, Connective
E, M, and P have high cell-cell contact, and low ECM contact, they interact with a specialised ECM called the basal lamina
Connective has low cell-cell contact and high amounts of ECM
Why does epithelial tissue have high cell-cell contact?
To increase SA and improve absorption
What are the functions of ECM?
Strength and support - basal lamina and bone/cartilage
Cellular Communication - hormone, growth hormones, cytokines
Cell migration, shape and polarity - embryonic development, angiogenesis, wound repair, tumour development
What is angiogenesis? How does the ECM help?
Formation of new blood vessels, when blood vessels become damaged, the cells latch on to the ECM to allow formation of new blood vessels
What is the Basal Lamina?
Very thin layer of ECM produced by cells above and below
It is evolutionary conserved
Essential for maintaining epithelial tissues
Composed of laminin, type IV and XVIII collagen, nidogen, perlecan and fibronectin
What kind of cells can be found in connective tissue? and what are they?
Can either be indigenous or immigrant cells
Indigenous: primitive mesenchymal cells, fibroblasts, specialised cells (chondrocytes/osteoblasts)
Immigrant: immune cells
What are primitive mesenchymal cells and what do they do?
They are a kind of indigenous cell in connective tissue
They are undifferentiated cells that can lead to the generation of other connective tissue cells, fat cells and mast cells
What do fibroblasts do?
Produce the components of the ECM
What is the competitive of connective tissue?
High MW, highly charged polysaccharides, Glycosaminoglycans (GAGs) covalently attached to proteins to form proteoglycans, they bind lots of water as they are heavily sulphated
Fibrous proteins - members of the collagen family
Glycoproteins - not part of the collagen family
GAGs:
Glycosaminoglycans
The most anionic molecules produced by animals
Made of repeating sugars, each sugars is basically glucose which has been adapted, each has a sulphate group which makes the sugar extremely negative allowing it to bind water
Different GAGs have different repeating disaccharides
GAGs are often linked to core proteins to form proteoglycans
More than one GAG can bind to a core protein (aggrecan) or can just bind singularly (decorin)
GAGs can also self-aggregate
What family do fibrous proteins belong to?
Collagen family
How many different types of collagen are there? and how are they made?
Synthesis by indigenous ECM cells (e.g. fibroblasts) 40 different types encoded by different genes 3 polypeptides (alpha chain; rich in proline/glycine) form a coil Different alpha chain combinations lead to different types of collagen, found in different connective tissues
What prevents aggregation of collagen inside cells?
Procollagen
Once secreted out of the cell enzymes chop of the pro collagen pieces, allowing aggregation to occur
What are elastins? What do they do? Where are they found?
Glycoproteins that are not members of the collagen family, they provide elasticity to connective tissues
They are a dominant component of ECM found in arteries
Key in blood vessels to allow stretch
What are fibronectins? What do they?
Glycoproteins that are not members of the collagen family, they bond other matrix/cell membrane proteins, organise the matrix and provide cell-matrix link
What are interns?
Key receptors that bind ECM
They are transmembrane molecules expressed on the surface of cells
How many different integrins are there? What are they made of?
24, they are made of an alpha and a beta chain with a large N terminal domain, different alpha and beta combination allow a wide array of different ECM molecules to be bound, different combinations tell you where the integrins are found
What is the function of the intracellular domain of integrins?
Intracellular domain interacts with adapter proteins
Why do integrins need an active and inactive form?
To be able to bind and unbind to the matrix to all cells wot be able to move
The active form is more rigid allowing for better binding and better signalling
How are integrins activated?
Requires intracellular signalling
The cell receives a signal, this causes talin to interact with the intern and activate it
The intern then binds on to the ECM
The intern also alters its intracellular conformation allowing it to bind proteins inside the cell
Activation of integrins can generate another signal
