Talk:2009 Lecture 13

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ANAT3231 - Cell Biology
Lecture 12 and 13
School of Medical Sciences
The University of New South Wales Dr Mark Hill Cell Biology Laboratory Room G20 Wallace Wurth Building Email:

UNSW Copyright Notice ExtraCellular Matrix (ECM) Cell-Cell, Cell-Matrix Adhesions

ECM References Essential Cell Biology Ch19 p594-604 Molecular Biology of the Cell p971-1009 Animal and Plant ECM Material secreted and deposited by cells

ANAT3231 Lecture 8 Extracellular matrix ECM Function

Support for cells
Pattern of ECM regulates

Polarity cell division adhesion motility Development migration differentiation Growth factors ECM Structure- Glycoproteins Fibers Collagen- main fibers Elastin Hydrated Matrix Proteoglycans high carbohydrate Adhesive Glycoprotein Laminin Fibronectin Shapes and Sizes ECM molecules Collagen tensile strength and elasticity Tendons Cartilage Bone half total body proteins (by weight) Collagen Components Insoluble glycoprotein protein + carbohydrate Protein high glycine and 2 modified amino acids hydroxylysine hydroxyproline (gly-X-Y)n Carbohydrate glucose galactose Collagen Structure Collagen Protein 3 polypeptide (a) chains left hand helix, forms fibers 14 different (vertebrate) collagens by different combinations of a-chains numbered I - XIV Type I, II, III main fibers, flexible Type I bone, skin, tendons 90% of all collagen Type II cartilage Collagen Fibers Type I, II, III cross striated showing overlapping packing of individual collagen molecules Type IV fine unstriated sheet-like supportive meshwork mature basal laminae tracks for embryonic migration barriers for cell migration Type V-XII smaller diameter fibers than I-III no striations Collagen Fibers Collagen Non-striated Collagen Synthesis Endoplasmic Reticulum mRNA attached to ER protein synthesized into ER lumen 3 proto-a-chains form soluble procollagen moved to golgi apparatus Golgi Apparatus packed into secretion vesicles fuse with membrane Outside Cell procollagen processed by enzymes outside cell assemble into collagen fibers Collagen Biosynthesis Collagen Diseases - Excess excess collagen fibrosis lung- pulmonary fibrosis overproduction of collagen I liver- over consumption of alcohol arteries- atherosclerosis Collagen Diseases - Insufficient insufficient collagen Ehlers-Danlos syndrome rubber-man skin and tendons easily stretched contortionists often suffer from this disease Osteogenesis imperfecta brittle-bone syndrome mutation in Type I procollagen fail to assemble triple helix degrade imperfect collagen Leads to fragile bones Collagen Diseases scurvy dietary Vitamin C deficiency needed for hydroxylation Proline -> Hydroxyproline form too few hydrogen bonds in collagen skin, bone, teeth weakness and malformation blood vessels weakened, bleeding Glycosaminoglycans (Gags) 10% by weight but fill most of space unbranched polysaccharide chains disaccharide subunits amino sugar 4 groups hyaluronan chondroitin sulphate, dermatan sulphate heparan sulphate, heparin keratan sulphate Glycosaminoglycans- Hyaluronan Also called hyluronic acid or hyaluronate Development produce a “cell-free” space for cell proliferation and migration into heart, cornea Adult in areas of compression tissues, joints Hyaluronan Synthesis synthesized at plasma membranes nascent chains directly extruded into ECM Proteoglycans Proteoglycans- Function trap water resistant to compression return to original shape occupy space link to collagen fibers form network in bone combined with calcium hydroxyapatite, calcium carbonate Cell adhesion embryonic migration Proteoglycan- Disease Cancer development altered types and kinds of proteoglycans formed by cells normal cells -> malignant Arthritis Cartilage breakdown chondrocytes elicit a catabolic response which exceeds anabolism of new matrix molecules Degrade proteoglycan (aggrecan) Also a mouse model generates antibodies to proteogycan