Extracellular Matrix Questions and Answers(A+ Solution guide)

extracellular matrix - serves as physical structure to stabilize cells, molecular barrier against cell migration during infection and metastasis type IV collagenases - breakdown type IV collegen, epithelial-derived cancer cells cannot metastasize until they express these proteinases, Clostridium species which cause gas gangrene also produce these growth factors - important in normal cell proliferation and their mis-regulation can lead to cancer, they are often secreted in the ECM where thy bind to proteoglycans and are prevented from interacting with cell surface receptors, they are activated when the ECM is subjected to enzymatic attack by a group of proteases refferred to as matrix metalloproteinases (MMPs) ECM can transmit signals - ECM can transmit signals from the outside to the cell interior during morphogenesis, wound healing, and for the maintenance of the differentiated state. components of the extracellular matrix - fibrous protein, hydrated gel, multiadhesive matrix protein, cells hydrated gel - imbibes and retains water, is reinforced with fibrous proteins, usually composed of a combination of hyaluronic acid and proteoglycans keratohyaline and alpha keratin - keratohyaline is a specialized ground substance in ECMs for example nail and hair, it is reinforced with the fibrous protein alpha keratin fibrous proteins - provide strength to the ECM include collagens (white connective tissue), elastins (yellow connective tissue), and keratins (in nails and hair) multiadhesive proteins - involved in the signal transduction processes that mediate morphogenesis, wound healing, and maintenance of the differentiated state. have binding sites for various matrix proteins and membrane intercolated receptors, help to hold th ecells in the ECM (fibronectin, laminin, dthrombospondin, tenascin, vitronectin, van Willebrand factor, nidogen/entactin)Cells that produce ECM - different cell produce different type os matrices (fibroblasts, chondrocytes, osteoblasts) fibroblasts - main producer of ECM, involved in the synthesis of loose connective tissue chondrocytes - produce cartilage ECM osteoblasts - produce the bone ECM epithelial and endothelial cells - produce basement membrane Glycosaminoglycans (GAGs) - unbranched polysaccharides composed of repeated disaccharide units (usually uronic acid and an amino sugar), can be classified according to the amino sugar they contain, they carry a good deal of negative charge contributed by the carboxylic acid and sulfate functional groups, because of the negative charge they are osmotically active and imbibe large quantities of water, they are responsible for the porous hydrated nature of ECM