Extracellular Matrix Flashcards
What is the extracellular matrix?
3d network of proteins and polysaccharides
Where is the ECM most abundant?
Connective tissue. Also present supporting epithelial cells and surrounding muscle, adipose, and peripheral nerve cells.
Two components of the basement membrane
Basal Lamina (superficial) Reticular Lamina (deep)
Function of Epithelia
- Barrier
- Absorption and Secretion
- Removal of particular matter
- Gas Exchange
- Filtration
Role of ECM
- Supports adhesion of cells
- Transmits signals through adhesion receptors
- Binds, stores, and presents growth factors
- Shapes tissue structures
- Guides and supports migrating cells
Collagen (I)
Fibril-forming type. Most common; found in skin, bone, tendons, cartilage, and ligaments. Perpendicular layering and lots of Gly-X-Y repeats for strength
Collagen Structure
Gly-X-Y repeats and triple helix.
Collagen (III)
Plays a role in wound repair as part of the provisional extracellular matrix / skin. Later replaced by collage I
Collagen (IV)
Network-forming variety. Found in the basal laminae. Sheet-like mesh from breaks in the Gly-X-Y. Important for filtration (kidney’s glomerulus, for ex).
Non-helical domains kept.
Collagen (VII)
Anchoring fibrils. Keeps the basement membrane intact and is crucial for the epidermis-dermis junction. Lots of Gly-X-Y repeats like collagen I but retains the non-helical domains.
Osteogenesis Imperfecta
Collagen I disorder. Incorrect formation of bones, featuring Ser-X-Y repeats instead of Gly-X-Y
Alport Syndrome
Collagen IV disorder. Progressive nephritis, hearing loss, and ocular lesions.
Dystrophic Epidermolysis Bulosa
Collagen VII disorder. Issues with dermis-epidermis anchoring. Blistering from heat/friction.
Glycosaminoglycans (GAGs)
long disaccharide chains, usually sulfated (negative charge is important for electrostatic interactions)
Proteoglycans
Long GAG chain joined to core protein. Mostly carbohydrate, little protein.
Location of proteoglycans
Extracellular matrix, membrane, floating in the cytosol. Also a major component of joint fluid.
Roles of Proteoglycans (4)
- regulate distribution of extracellular signaling molecules
- modulate signaling events at cell surface
- serve as structural constituents of ECM
- regulate movement of molecules between intracellular and extracellular compartments
What needs to bind to fibroblast growth factor (FGF) to activate it?
proteoglycans bind and then it can attach to the cell surface receptor
What is aggrecan?
It’s a major proteogylcan in cartilage. Its enzymatic destruction can be an early sign of arthritis.
What does heparanase do?
Cleaves heparan sulfate-PG to release the sequestered growth factor.
Fibrillin
elastic fiber coming in two forms (1, 2) which provides the scaffolding for tissues and sequesters growth factors.
What protein fiber is found in the skin, lens of the eye, aorta, and periosteum (connective tissue covering the surface of bones)?
Fibrillin
Marfan Syndrome
Mutated fibrillin-1 gene. Causes malformation of digits, limbs, and anterior chest wall. It can also cause nearsightedness and aneurysms (weakens aortic wall)
Fibronectin
Protein involved in blood clotting (attaches to fibrin in clot), wound healing, platelet adhesion/aggregation, cell adhesion, binding to bacteria, and to screen for premature delivery.
