Extracellular Matrix (ECM) PDF

**Definition**: Specialized ECM separating epithelia from connective tissue. Laminin, Type IV collagen, Nidogen, Perlecan. **Composition**:...

**Definition**: Specialized ECM separating epithelia from connective tissue. Laminin, Type IV collagen, Nidogen, Perlecan. **Composition**: Basal Lamina Selective filter for molecules/cells. Scaffold for tissue regeneration. **Functions**: **Definition**: ECM is a dynamic structure Example: Retains synaptic organization during surrounding cells in tissues. neuromuscular junction regeneration. Proteins (e.g., collagen, elastin). Collagen. Polysaccharides (e.g., glycosaminoglycans, **Composition**: proteoglycans). GAGs/proteoglycans. Dimer with binding sites for: Introduction Synthesized locally and assembled into a Integrins (cell receptors). network. Fibronectin **Abundance**: ECM is 95% of bone and cartilage tissue. Facilitates cell adhesion, migration, and ECM interactions. **Structural role**: Fills spaces and provides mechanical support. Cross-shaped heterotrimer found in basal Adhesion Proteins lamina. **Functions**: Influences cell survival, development, shape, and function. Integrins. **Regulatory role**: Example: Cancer cells use ECM for migration. Type IV collagen. Binds to: Laminin Nidogen, proteoglycans. Acts as a hydrated gel matrix. Forms scaffolds in the basal lamina. **Proteoglycans**: Proteins bonded to Provide hydration and resist compression (e.g., Ground Substance glycosaminoglycans (GAGs). cartilage). Cross-linked elastin molecules via lysine Non-sulfated GAG. residues. **Structure**: **Hyaluronic Acid**: Forms elastic networks. Elastin Extracellular Matrix Key Components of ECM Facilitates cell migration, tissue repair, and shock absorption. Elasticity in skin, lungs, and arteries. (ECM) Provide structural and adhesive properties. **Functions**: Anchored to collagen to prevent over- **Collagen**: Tensile strength. stretching. **Elastin**: Elasticity in tissues like skin and Fibrous Proteins blood vessels. Triple helix of polypeptide α-chains. Facilitate adhesion and migration. Glycine: Tight packing. **Fibronectin and Laminin**: Amino acids: **Structure**: Anchor cells to the ECM. Proline, Hydroxyproline: Stabilize helix. Synthesized as procollagen intracellularly, Unbranched polysaccharides with repeating cleaved extracellularly. Collagen disaccharide units. Example: Type I in bone, skin, tendons. **Fibril-Forming Collagens**: **Structure**: Composed of sugar acid and amino sugar. Example: Type IV in basal lamina. **Network-Forming Collagens**: **Types and Organization**: Highly negative charge (sulfate/carboxyl groups attract cations). Example: Type IX stabilizes Type II in cartilage. **Fibril-Associated Collagens (FACIT)**: Hydrated gel formation for resistance to compression. Core protein linked to 100+ GAG chains via tetrasaccharide linkage. **Functions**: Attract Na+ for osmotic pressure. **Structure**: Glycosaminoglycans (GAGs) Synthesized in rough ER (protein) and Golgi Example: Knee cartilage withstands high (GAG addition, sulfation). pressures. **Aggrecan**: Cartilage, resists compression. Hyaluronan: Simplest, non-sulfated, tissue repair. **Decorin**: Regulates collagen fibril assembly. **Functions**: Proteoglycans Chondroitin/Dermatan Sulfates: Resilience in cartilage. **Syndecans**: Cell signaling and adhesion. **Types**: Proteoglycans bound to hyaluronic acid via link Heparan Sulfate: Filtration in basement proteins. membranes. **Proteoglycan Aggregates**: Example: Aggrecan aggregates in cartilage Keratan Sulfate: Present in cornea and cartilage. resist compression.