Lecture 3 Flashcards
What are the three types of intercellular junctions ? Describe them
1) Tight junctions : create epithelia, prevent leakage of fluid, ions, … (watertight). Protein complex = occludin, claudin 1
2) Desmosomes (anchoring junctions) : on lateral side of membranes -> adhesion protein (cadherin) connected to cytoskeleton bridges the space between the cells -> strong mechanical attachment
3) Gap junctions : assembly of 6 proteins connexins creates a connexon with a gap in the middle -> communication through exchange of materials (selective)
What are the two types of ECM ?
Intersititial matrix and basement membrane
Describe intersitial matrix : where, composition
In connective tissue, synthesized by mesenchymal cells, forms amorphous gel structure.
Collagen, fibronectin, elastin, proteoglycan, hyaluronate, …
Describe basement membrane : where, composition
Highly organized around epithelial cells, endothelial cells and smooth muscle cells.
Synthesized by mesenchymal and epithelial cells.
Porous flat lamellar mesh.
Collagen IV, laminin, sulfated proteoglycans.
4 main functions of ECM
1) mechanical / structural support
2) control of cell proliferation (growth factors and cytokines)
3) scaffolding for tissue renewal
4) establishement of tissue microenvironments
What are the three groups of proteins composing ECM ? fourth ?
1) fibrous structural proteins : collagen, elastins, fibrillin -> tensile strength and elasticity
2) Water-hydrated gels (proteoglycans) -> compressive resistance and lubrication
3) adhesive glycoproteins and receptors : fibronectin, laminin and integrin -> connect ECM and cells
4) water
structure of collagen
amino acids in form of triple helices (3 alpha chains) -> fibrils -> fibers
role of integrin ?
link ECM to cytoskeleton (creates focal adhesion complexes) and initiate intracellular signaling cascades
Different things that adhesion can influence
1) cell shape : cell can spread depending on the nb of focal adhesions
2) cell proliferation
3) cell migration
4) differentiation (depending on what is secreted / produced in the ECM)
What happens if we have no vitamin C ?
Problem in collagen production -> scurvy : poor vessel suuport, impaired wound healing, …
What is the result of a collagen I defficiency ?
osteogenesis imperfecta : brittle bones, short height, …