Matrix,extracellular

The ECM has a very wide variety of functions it establishes mechanical connections between cells it creates structures with special mechanical properties (as in bone, cartilage, tendons, and joints) it creates filters (e. g., in the basal membrane in the renal corpuscles see p.322) it separates cells and tissues from each other (e.g., to allow the Joints to move freely) and it provides pathways to guide migratory cells (important for embryonic development). The chemical composition of the ECM is just as diverse as its functions. 

Collagens (see p. 344), of which there are at least 19 different varieties, form fibers, fibrils, networks, and ligaments. Their characteristic properties are tensile strength and flexibility. Elastin is a fiber protein with a high degree of elasticity. 

Adhesive proteins provide the connections between the various components of the extracellular matrix. Important representatives include laminin and fibronectin (see B). These multifunctional proteins simultaneously bind to several other types of matrix component. Cells attach to the cell surface receptors in the ECM with the help of the adhesive proteins. 

Due to their polarity and negative charge, proteoglycans (see C) bind water molecules and cations. As a homogeneous cement, they fill the gaps between the ECM fibers. 

Fibronectins are typical representatives of adhesive proteins. They are filamentous dimers consisting of two related peptide chains (each with a mass of 250 kDa) linked to each other by disulfide bonds. The fibronectin molecules are divided into different domains, which bind to cell-surface receptors, collagens, fibrin, and various proteoglycans. This is what gives fibronectins their molecular glue characteristics. 

Ascarelli and J. C. Morrison Use of fetal fibronectin in clinical practice. Obstetrical and Gynecological Survey 52(Suppl.), SI (1997). 

Hynes Integrins Versatility, Modulation and Signalling in Cell Adhesion. Cc//69, II (1992). 

Piez History of extracellular matrix A personal review. MatrixBiology 16,85(1997). 

Labat-Robert, M. Bihari-Varga, and L. Robert Extracellular Matrix. FiiBS Letters 268,386(1990). 

Stadelmann, A. G. Digens, and G. R. Tobin Physiology and healing dynamics of chronic cutaneous wounds. American Journal of Surgery 176(Suppl. 2A), 265 (1998). 

---

Oberhauser et al., 1998] Oberhauser, A. F., Marszalek, P. E., Erickson, H., and Fernandez, J. The molecular elasticity of tenascin, an extracellular matrix protein. Nature. In Press. 

Kielty, C.M., Hopkinson, 1., Grant, M.E. Collagen structure, assembly and organization in the extracellular matrix. In Connective Tissue and its Heritable Disorders Wiley-Liss, Chichester, pp. 103-147, 1993. 

Extracellular matrix The surfaces of animal cells are covered with a flexible and sticky layer of complex carbohydrates, proteins, and lipids. This complex coating is cell-specific, serves in cell-cell recognition and communication, creates cell adhesion, and provides a protective outer layer. 

Proteoglycans may be soluble and located in the extracellular matrix, as is the case for serglycin, versican, and the cartilage matrix proteoglycan, or they may be integral transmembrane proteins, such as syndecan. Both types of proteoglycan... 

Secreted or extracellular matrix proteoglyeans Large aggregating cartilage proteoglycans CS/KS 220,952 2124... 

Cathepsins are intracellular proteinases that reside within lysosomes or specific intracellular granules. Cathepsins are used to degrade proteins or pqffides that are internalised from the extracellular space. Some cathepsins such as cathepsin-G or cathepsin-K may be released from the cell to degrade specific extracellular matrix proteins. All cathepsins except cathepsin-G (serine) and cathepsin-D (aspartyl) are cysteine proteinases. 

Integrins, selectins, cadherins, claudins and other cell adhesion molecules are involved in the interaction of cells with other cells or with extracellular matrix components. Some of them also serve as receptors by inducing outside-in or additional inside-out signaling. 

In biology, extracellular matrix (ECM) is the extracellular part of animal tissue that usually provides structural support to the cells in addition to performing various other important functions. ECM is the defining feature of connective tissue in animals. ECM includes the interstitial matrix and the basement membrane. 

Heparin sulfate proteoglycans (HSPGs) are heavily glycosylated proteins that are part of the extracellular matrix. Interaction with HSPGs help to stabilize and localize extracellular Wnts. 

Integrins constitute a large family of a (3 heterodimeric cell surface, transmembrane proteins that interact with a large number of extracellular matrix components through a metal ion-dependent interaction. The term integrin reflects their function in integrating cell adhesion and migration with the cystoskeleton. 

Reelin is an extracellular matrix protein, which is secreted by neuronal cells and binds to two lipoprotein receptors (VLDLR and ApoER2) that relay the Reelin signal inside target neurons by docking the tyrosine kinase adapter disabled-1 (Dabl). This allows neurons to complete migration and adopt their ultimate positions in laminar structures in the central nervous system. In... 

---