2024-25 ECM PDF

Prof Wanda Lattanzi Dept Life Science and Public Health Section of Biology Room 352bis 1st Floor Istituti Biologici [email protected]  Warning The contents of these slides are the exclusive property of the Instructor and/or granted by third parties (textbook...

Prof Wanda Lattanzi Dept Life Science and Public Health Section of Biology Room 352bis 1st Floor Istituti Biologici [email protected]  Warning The contents of these slides are the exclusive property of the Instructor and/or granted by third parties (textbooks’ reference for pictures) and are therefore protected by the current regulations governing the Protection of Copyright. All rights are reserved. The reproduction and/or diffusion, even partial, by any analogical and/or digital means, without the consent of the rights holder is FORBIDDEN. Any unauthorized use of the above mentioned "Contents" is under the full and exclusive responsibility of the users who will be responsible for it, according to the laws and regulations in force. It is allowed the use of the material for private and study use, however not for profit and without commercial purposes. Cell-extracellular matrix interactions Cell-cell and cell-environment mechanical interactions The cells of a multicellular organism physically interact with one another and with the extracellular environment. These interactions regulate diverse activities as cell migration, cell growth, and cell differentiation. They determine the 3D organization of tissues and organs that emerges during embryonic development.  Integrins Transmembrane receptors that mediate cell-extracellular matrix (ECM) adhesion. Family of integral proteins expressed on the plasma membrane of animal cells Bind ECM component and transduce the signal inside the cell They usually bind their ligand with lower affinity and are usually present at about 10-100fold higher concentration than other receptors on the cell surface (“Velcro principle”). Polypeptidic transmembrane chains  and  in various combinations with cell- and tissue-specific distribution Integrins 18 α subtypes and 8 β subtypes which together generate 24 known binding pairs of integrin heterodimers in humans Integrins Bind diverse matrix molecules thanks to the heterogeneity of the monomers The α subunit determines the ligand specificity for cell- ECM adhesion, The β subunit mediates subsequent mechanotransdu ction events. Integrins Integrin-based signaling Inside-out signalling Multiple signals (A) from inside the cell can trigger integrin activation They promote the recruitment of activators (e.g. talin) to the β-integrin cytoplasmic tail Talin binding to integrins promotes a conformational transition from a bent inactive receptor to an open and primed integrin that favors ligand binding. Hamidi et al. Br J Cancer 115, 1017–1023 (2016).  Integrins Outside-in signalling Integrin–ECM interaction elicits intracellular signals (signal B) Induces focal adhesion formation and actin cytoskeletal reorganization This affects downstream cellular processes Growth factor receptors are capable of eliciting specific signals (signal C) or in cross-talk with integrins feed into the same pathways to generate unique signals (signal D) in response to ECM cues. Hamidi et al. Br J Cancer 115, 1017–1023 (2016). Glycocalix Formed by the carbohydrate projections of glycoproteins included in the plasma membrane (especially in epithelia of GE tract mucosae) mediates cell–cell and cell–substrate interactions provides mechanical protection to cells serves as a barrier to particles moving toward the plasma membrane binds regulatory factors that act on the cell surface. Extracellular matrix (ECM) Network formed by molecules secreted by the cells. Provides mechanical support and holds cells together. Provides chemical and physical signals to stabilize cell morphology and tissue architecture, and to control cell and tissue homeostasis. Extracellular matrix (ECM) Interspersed among cells in connective tissues Forms the basement membrane (or basal lamina) in epithelia ECM composition The ECM may take diverse forms in different tissues and organisms, though it tends to be composed of a similar array of macromolecules ECM proteins are typically fibrous in their 3D structure; they are secreted into the extracellular space where they are capable of self-assembling into an interconnected three-dimensional network. ECM composition Three classes of proteins: ✓Structural proteins (collagens and elastins) ✓Protein-carbohydrate complexes (proteoglycans) ✓Adhesive glycoproteins (fibronectins and laminins) Structural ECM proteins Collagen and Elastin  Collagen Family of glycoproteins, conserved across animal species The most abundant protein in the whole body Confer high tensile strength to the ECM Produced by fibroblasts, smooth muscle cells, epithelial cells  Collagen types 28 different types of collagens (90% are types I-IV *) Formed by the alternative combination of 30 distinct polypeptide chains. Subdived into classes based on the structures they form, expressed in different tissues Each collagen type is restricted to particular locations within the body, but two or more different types are often present together in the same ECM.  Collagen structure Trimeric fibers made up of  chains that are either identical (homotrimer) or different from one another (heterotrimer). Functional complexity is provided by mixing several collagen types within the same fiber → different structural and mechanical properties  Collagen synthesis Many proline and lysine residues are hydroxylated and form hydrogen bonds between the polypeptide chains The proline hydroxylation is critical for the stabilization of the triple helix conformation and to ensure hydrosolubility. Specific hydroxylysine residues located in the helical domain of the molecule are glycosylated by the addition of galactose or glucose-galactose  Collagen synthesis Outside the cell, lysine and hydroxylysine residues can be oxidatively deaminated to produce reactive aldehydes that undergo a series of non-enzymatic condensation reactions to form covalent intra- and inter-molecular cross-links.  Collagen in diseases Failure to hydroxylate Pro and Lys of collagen chains leads to inappropriate collagen fiber formation, with impaired tensile strength and tissue integrity Scurvy, due to deficiency of vitamin C (ascorbic acid) Ascorbic acid is needed for proline hydroxylation collagen fibers  Collagen in diseases Mutations in collagen genes cause congenital defects affecting the structure and function of specific tissues Osteogenesis imperfecta caused by mutations in COL1A1 or COL1A2 genes  Collagen in diseases Mutations in collagen genes cause congenital defects affecting the structure and function of specific tissues Ehlers-Danlos disease caused by mutations in several different genes , including COL5A1, COL5A2, COL1A1, COL3A1 genes Elastin Highly insoluble protein, resistant to acids and alkali. Provides elasticity and resilience to tissues that must deform reversibly (blood vessels, lungs, skin, ligaments, elastic cartilage) Synthesized by fibroblasts and smooth muscle cells Owing to its extensive crosslinked structure, elastin degrades slowly in healthy tissues,with a half-life of about 70years Elastin Elastic fibers are the products of enzymatically cross linked tropoelastin monomers and microfibrillar proteins. Elastic fiber formation entails reticulation of tropoelastin monomers over a fibrillin-rich microfibril template. Elastin gene expression and protein synthesis occur from late embryonic development to the end of adolescence, producing no de novo elastin throughout adult life. Elastin in diseases Cutis laxa: rare congenital disorder caused by mutations in different genes leading to reduced, defective or absent elastin in tissues Protein-carbohydrate complexes of the ECM Proteoglycans  Proteoglycans Abundant in cartilage, bone and skin ECM Core protein molecule to which chains of glycosaminoglycans (GAGs) are covalently attached Each GAG is composed of a repeating disaccharide of two different sulfated sugars (chondroitin sulfate and keratan sulfate) GAGs are highly acidic due to the presence of both sulfate and carboxyl groups attached to the sugar rings Core proteins bind to hyaluronic acid, a giant nonsulfated GAG, through link proteins  Proteoglycans Proteoglycans bind water molecules and form a porous, hydrated gel that fills the extracellular space like packing material This confers to the ECM high resistance against crushing (compression) forces. Adhesive glycoproteins Fibronectins and laminins  Fibronectin Each polypeptide is a linear array of approximately 30 modular fibronectin (Fn) domains Each of them providing binding sites for ECM components  Laminin Family of glycoproteins 3 different polypeptide chains linked by disulfide bonds to form cross-shaped heterotrimer with three short arms and one long arm Bind tightly to the plasma membrane Bind to other laminins, collagen, and other ECM components Matrix metalloproteinases (MMP) Zinc-containing enzymes, produced as inactive precursors (zymogens) MMPs degrade ECM components to allow renewal and remodeling during embryonic development, tissue modeling and healing following injury.  MMP in wound healing Cutaneous wound the skin is damaged by a full-thickness injury Inflammation the wound is occupied with fibrin clot to seal the wound, and levels of MMP-2 and MMP-9 are increased. Fibroblasts and macrophages migrate into the wound site, where they are stimulated to release more MMPs to remodel the ECM. Angiogenesis - proliferation - remodeling upregulation of a variety of MMPs (including MMP-1, MMP- 8, MMP-9, and MMP-13) would stimulate epithelial cells (keratinocytes) to proliferate and migrate to re-epithelialize over the wound area. Prolonged inflammation could cause the wounds to become chronic, as it has been observed in diabetic foot ulcers. During chronic wounds, the irregular up-regulation of MMP-9 has been associated with reduction of MMP-8 and plays a detrimental role in ECM remodeling. Tissue remodeling and expression of MMPs are attenuated when the epithelial cells proliferate and differentiate in order to reform the new epithelium. During this last phase of wound Roles of Matrix Metalloproteinases in Cutaneous Wound Healing http://dx.doi.org/10.5772/64611 healing, fibroblasts can continue to remodel the underlying dermis over a period of several months.