EXTRACELLULAR MATRIX: ORGANIZATION AND FUNCTION MOLECULAR ORGANIZATION AND FUNCTION SUBMITTED BY:- MINA KUMARI CHETRY

CONTENTS:- INTRODUCTION ORGANIZATION OF EXTRACELLULAR MATRIX GLYCOSAMINOGLYCAN(GAG) TYPES OF GLYCOSAMINOGLYCAN FIBROUS PROTEIN TYPES OF FIBROUS PROTEIN CONCLUSION REFERENCE

INTRODUCTION The substance or macromolecule are secreted and synthesized by local cells in the tissue is called extracellular matrix. It has an active and complex role in regulating the behavior of the cells.

Organization of extracellular matrix In most connective tissues, the matrix macromolecules are secreted largely by cells called fibroblasts. In certain specialized types of connective tissues, such as cartilage and bone, however, they are secreted by the cells of fibroblast family that have more specific names: chondroblasts, for example, form cartilage and osteoblasts form bone.

TWO MAIN CLASSESOF EXTRACELLULAR MATRIX GLYCOSAMINOGLYCAN FIBROUS PROTEIN

GLYCOSAMINOGLYCANS(GAG) Glycosaminoglycans (GAGs) are unbranched polysaccharide chains composed of repeating disaccharide units. They are called GAGs because one of the two sugar (N-acetylglycosamine or N-acetylgalactosamine) which in most cases are sulfated. The second sugar is usually a uronic acid(glucuronic or idouronic).

TYPES OF GLYCOSAMINOGLYCANS (GAG) CHAIN Hyaluronan Chondroitin sulfate and dermatan sulfate Heparan sulfate Keratan sulfate

HYALURONAN STRUCTURE AND ORGANIZATION Simplest GAG Consist of regular repeating sequence of up to 25000 disaccharide unit It is found in variable amount in all tissues Abundant in early embryos Contain no sulfated sugar All its disaccharide unit are identical It is not linked covalently to any core protein

FUNCTIONS OF HYALURONAN It has role resisting compressive forces in tissue and joints. It is important as a space pillar during embryonic development. In the developing heart Hyaluronan synthesis helps in formation of valves and septa that’s separate heart chambers. Hyaluronan produce in large quantities during wound healing It is an important constituent of joint fluid which serves as an lubricant.

PROTEOGLYCANS GAGs are covalently attached to protein to form proteoglycans. It is produced by mostly animal cells. Membrane bound ribosome's make the core protein of proteoglycans which is then threaded into the lumen of endoplasmic reticulum. Proteoglycans can be huge or small.

CHONDROITIN AND DERMATAN SULFATE CHONDROITIN SULPHATE Major constituent of mammalian tissue(bone, cartilage, tendon, heart, valves, skin, cornea etc) It consist of repeating disaccharide unit of D- glucuronic acid and N- acetylgalactosamine 4- sulfate DERMATAN SULFATE Mostly found in skin. It consist of repeating disaccharide units of L- iduronic acid and N-acetylgalactosamine 4-sulfate

FUNCTION OF CHONDROITIN AND DERMATAN SULFATE The function of chondroitin sulfate is to deliver nutrients to the join cartilage It helps to inhibit the emzyme which decompose the joint cartilage Dermatan sulfate help role in coagulation, cardio vascular disease, infection wound repair and carcinogenisis

HEPARAN SULFATE Heparan molecule is present on many cell surface as a proteoglycans. It contains D-glucosamine with fewer N-sulfates and D- glucuronic acid. HSPGs are glycoproteins which contain one or more covalently attached heparan sulfate chain

FUNCTION OF HEPARAN SULFATE Act as receptors. Participate in mediation of cell growth. Also participate cell to cell communication.

KERATAN SULFATE Heterogenous GAG with variable sulfate content Consists of alternating unit of D-galactosamine and N- acetylglucosamine 6-sulfate.

FIBROUS PROTEIN Important component of extracellular matrix. Elongated shape. Special fibrous proteins are :- collagen, elastin and fibronectin. Have low solubility in water. Fibrous protein have amino acid sequences that favour a particular kind of secondary structure.

COLLAGEN Family of fibrous protein found in multicellular animals. Major component of skin and bone. Most abundant proteins in mammals. It is long , stiff, and has triple stranded helical structure. Extremely rich in proline and glycine. 40 types of collagen molecules have been found.

FUNCTION OF COLLAGEN Collagen imparts strength, support, shape and elasticity. Collagen provides flexibility, support and movement to cartilage. It contributes to proper alignment of cells for cell proliferation and differentiation. Protects delicate organs like kidneys and spleen.

ELASTIN A network of elastic fibers in the extracellular matrix of these tissue gives them the required resilience. Main component is elastin- hydrophobic protein which contains hydroxylysine Soluble tropoelastin is secreted into the extracellular space and assembled into elastic fibers close to the plasma membrane. Elastin composed of two types of short segments :- Hydrophobic segments- responsible forelastic properties of molecule. Alanine and lysine – rich in alpha helicals segments which form cross link between adjacent molecules.

Functions of elastin It provide elasticity and resilience to the tissue. It allows many tissues in the body to resume their shape after stretching or contracting. It helps to keep out skin flexible but tight. It also helps to keep skin smooth as its stretches to accommodate normal activities like flexing a muscles or opening and closing of mouth to talk or eat

ADHESIVE PROTEIN Adhesive is the process by which cells interact and attach to neighboring cells through specialized molecules of the cells surface. There are three types of adhesive protein: 1) fibronectin 2) laminin

FIBRONECTIN STRUCTURE AND ORGANIZATION: Fibronectin is a large glycoprotein found in all vertebrates and important for many cell matrix. Fibronectin is dimer composed of two very large subunits joined by sulfide bonds at one end. The integrins provide a linkage from the fibronectin outside the cell to the actins cytoskeleton. The linkage provide tension to the fibronectin molecules.

FUNCTION OF FIBRONECTIN It helps to cell adhesion, differentiation, growth, migration. Fibronectin forms a blood clot, along with fibrin. Fibronectin and fibronectin receptor function are needed for cleft formation, the initial stage of salivary gland branching morphogenesis.

LAMININ Laminin are the family of extracellular glycoprotein that consist of three different polypeptide chains linked by disulfide bonds. 15 different laminin have been identified. Like fibronectin, extracellular laminin can greatly influence a cell’s potential for migration, growth, and differentiation.

Conclusion:- The substances or macromolecule which are secreted and synthesized by local cell is called extracellular matrix. It plays a vital role in every cells some of them are:- 1) Provides support and anchorage for cells. 2) Regulates and determine cells dynamic behavior : - polarity of cells - cell differentiation - adhesion - migration 3) provide mechanical support for tissues and organ architecture. - growth - regenerative and healing processes.

REFERENCES:- THE CELL(5TH EDITION) BY :- BRUCE ALBERT PRINCIPLES OF BIOCHEMISTRY(5TH EDITION) BY:-DAVID L. NELSON MICHAEL M. COX ILLUSTRATE BIOCHEMISTRY(21ST EDITION) BY:-VICTOR W RODWELL PETER A MAYES