Lecture #8v2 (2)

Lecture #8v2 (2) - 2/23/2009 Extracellular Matrix...

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2/23/2009 1 Extracellular Matrix Components Comprised of linear repeating modules organized into fibrous filament or network Collagen not aligned in register- strength - Fibrous glycoprotein - High tensile strength (stretches without breaking) - Produced primarily by fibroblasts in connective tissues, smooth muscle, and epithelial cells fibril fiber Lys Defective in Scurvy (Vit C def) Fig. 7.6 - Triple helix of α chains- >20 Types Gly-Pro-X repeat α chain - Types I, II, III, and IV- fibrillar diseases of hyperflexible joints, fragile bones, dwarfism, etc. - Type IV- nonfibrillar, sheet forming (cornea) non- α chain segments and globular ends allow assembly into lattice instead of filament
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2/23/2009 2 cornea fiber banding reflects fibril alignment Type V fibrillar Type I Type IV- nonfibrillar basement membrane EM of Collagen Types Fig. 7.6-7.8 Proteoglycans- In addition to collagen, extracellular matrices typically contain large amounts of a distinctive type of protein- polysaccharide complex called proteoglycan
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2/23/2009 3 Proteoglycans - Core protein with covalently attached glycosaminoglycans GAG = repeating disaccharide with SO 4 - and COO - groups SO 4 - bind cations and H 2 O, form hydrated gel packing material - Cross-linked into large matrix by hyaluronic acid (nonsulfated GAG) - Resist crushing forces; cushion cells - Provide binding sites for growth hormones to protect from proteases, regulate diffusion of small signaling molecules in developing embryo, etc. A proteoglycan from cartilage matrix actually contains abut 30 keratin sulfate and 100 chondroitin sulfate chains, whose structure is shown in b. Single proteoglycan: single core protein to which a large number of glycosaminoglycan chains are attached Extracellular Matrix Organized network of extracellular materials outside plasma membrane, provides support and determines shape and activity of cell Connecting Proteins-connect cell to EM and EM-EM Fig. 7.5
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2/23/2009 4 Fibronectin, laminin and other proteins of the ECM- The term matrix implies a structure made up of a network of interacting components which is apt for the extracellular matrix. In addition to collagen and proteoglycans there are many other proteins. Fibronectin is one of the best-studied extracellular proteins. Fibronectin, like other fibrous proteins of the ECM, consists of a linear series of distinct domains that gives each polypeptide a modular construction. Each of the two polypeptide chains that make up a fibronectin molecule contains : 1. Binding sites for other components of the ECM, such as collagen and proteoglycans . These binding sites facilitate interactions that link these diverse molecules into a stable, interconnected network (seen in Fig. 7.5) 2. Binding sites for receptors on the cell surface ( e.g., integrins ). These binding sites hold the ECM in a stable attachment to the cell .
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This note was uploaded on 08/25/2009 for the course BIO 315 taught by Professor Steiner during the Spring '08 term at Kentucky.

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Lecture #8v2 (2) - 2/23/2009 Extracellular Matrix...

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