ECB Chapter 20: Extracellular Matrix and Connective Tissue PDF

ECB Chapter 20 Extracellular matrix and Connective tissue  Multicellular organisms: different cell types and fluid in between 21_01_built_of_cells.jpg  Why do we need connective tissue? 21_02_tissues.jpg Connective tissue offers protection against mechanical stress and...

ECB Chapter 20 Extracellular matrix and Connective tissue  Multicellular organisms: different cell types and fluid in between 21_01_built_of_cells.jpg  Why do we need connective tissue? 21_02_tissues.jpg Connective tissue offers protection against mechanical stress and is involved in transport of oxygen and nutrients Connective tissue and extracellular matrix: Collagen pulling forces Proteoglycans pressure forces Basal lamina (collagen and laminin) adhesion Cell-connections (extracellular matrix - cytoskeleton) Tight junction Adherence junction Desmosome Hemidesmosome Gap junction  Collagen genes Different collagens are made from different genes. They are used at different sites in the body Bone is connective tissue Connective tissue provides sturdiness Bone is connective tissue and calcium phosphate deposit Bone is almost completely extracellular matrix Within bone, collagen is the major component of the extracellular matrix Protein Molecule Fibril Fiber Fiber cross section Fiber longitudinal section The skin without collagen fibers: 21_11_elastic_skin.jpg James Morris (elastic skin man, 1890) had a genetic defect resulting in the loss of collagen fibers Stacking collagen to increase strength The cornea of the eye can resist a lot of force and stay intact The cornea has perpendicular stacking of collagen fibers Fibroblasts make collagen Collagen fiber Fibroblasts secrete collagen molecules Fibroblast Fibroblasts: ‘selforganizing’ collagen fibers 21_13_align_collagen.jpg  Fibroblasts have a grip on collagen The adhesion between fibroblast and matrix and (focal point) can be made and broken: how does this work?  Integrins: connection between cytoskeleton and extracellular matrix actin – adapter protein – integrin – fibronectin - collagen Fibronectin: connection between extracellular and intracellular skeleton 21_14_Integrins_link.jpg Two-way communication via integrins Integrin activity can be modulated Active through binding to fibronectin (outside- to-inside activation) Active through binding to the cytoskeleton (inside-to-outside activation) Regulating integrin activity determines ‘behaviour’ of the cell Integrin activity can be modulated by intracellular signals Via this mechanism, the fibroblast can attach to and release from a substrate Kinases and phosphatases regulate binding Connective tissue and extracellular matrix: Collagen pulling forces Proteoglycans pressure forces Basal lamina (collagen and laminin) adhesion Cell-connections (extracellular matrix - cytoskeleton) Tight junction Adherence junction Desmosome Hemidesmosome Gap junction Glycosaminoglycans (GAG): negatively charged polysaccharides Negative charge Hyaluronic acid: GAG in cartilage (25,000 repeats of the sugar) Proteoglycans form large complexes built of proteins and glycosaminoglycans Polysaccharides (blue and red) Protein (green and black) Glycosaminoglycans & proteoglycans can protect against focal pressure Na+ ions attract H2O This forms a ‘gel’ Gel cannot be compressed The eye is filled with it Connective tissue and extracellular matrix Collagen pulling forces Proteoglycans pressure forces Basal lamina (collagen and laminin) adhesion Cell-connections (extracellular matrix - cytoskeleton) Tight junction Adherence junction Desmosome Hemidesmosome Gap junction Epithelium stands on Basal Lamina 21_17_epithelial_sheet.jpg  Basal lamina: surface binding epithelial cells at their basal side Collagen IV Laminin Laminin also binds to integrins  Polarised orientation 21_18_sheet_polarized.jpg  Polarisatie van de cel is functioneel Polarised cells in the gut epithelium 21_20_polarize_line_gut.jpg Nutrients Mucus Connective tissue and extracellular matrix Collagen pulling forces Proteoglycans pressure forces Basal lamina (collagen and laminin) adhesion Cell-connections (extracellular matrix - cytoskeleton) Tight junction Adherence junction Desmosome Hemidesmosome Gap junction  Verschillende Polarised cells typen cel-cel contacten and cell-to-cell contacts 21_21_cell_cell_junction.jpg Belangrijk plaatje: vat de verschillende contacten samen Tight junctions: water barriers Tight junctions 21_22_Tight_junctions.jpg Tight junction barrier for: water membrane proteins  Verschillende Polarised cells typen cel-cel contacten and cell-to-cell contacts 21_21_cell_cell_junction.jpg Belangrijk plaatje: vat de verschillende contacten samen Adherence junction/adhesion belt: cell-to-cell contacts by actin filaments Adhesion belt contains actin fibers Actin fibers can contract Contraction of the adhesion belt can change the shape of the epithelium Examples 21_25_tube_or_vesicle.jpg Neural tube Lens of the eye Cadherins between cells: connect intermediary filaments/ actin cytoskeleton Intermediary filaments in green GFP tagged cadherin molecules  Verschillende Polarised cells typen cel-cel contacten and cell-to-cell contacts 21_21_cell_cell_junction.jpg Belangrijk plaatje: vat de verschillende contacten samen Desmosome: cell-to-cell contact of intermediate filaments 21_26_Desmosomes.jpg  Verschillende Polarised cells typen cel-cel contacten and cell-to-cell contacts 21_21_cell_cell_junction.jpg Belangrijk plaatje: vat de verschillende contacten samen Hemidesmosome: connects intermediate filaments and the extracellular matrix Resembles the focal contacts of migrating fibroblasts  Verschillende Polarised cells typen cel-cel contacten and cell-to-cell contacts 21_21_cell_cell_junction.jpg Belangrijk plaatje: vat de verschillende contacten samen Gap Junctions: exchange of small molecules Gap junctions can be open or closed Gap junction conductance can be regulated (as shown for the transmitter dopamine) 21_29_coupling_gap.jpg What did we discuss today? Connective tissue and extracellular matrix: Collagen pulling forces Proteoglycans pressure forces Basal lamina (collagen and laminin) adhesion Cell-connections (extracellular matrix - cytoskeleton) Tight junction Adherence junction Desmosome Hemidesmosome Gap junction