tight junctions occluding junctions sealing strands are rows of transmembrane proteins
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Anchoring Junctions
• Attach cytoskeleton to neighboring cell or to extracellular matrix
• Intracellular anchor proteins
• Transmembrane adhesion proteins
Adherens Junctions
• Connect actin filaments in neighboring cells
• Cadherin transmembrane adhesion proteins
• Catenin anchor proteins
Desmosomes
• Connect intermediate filaments in neighboring cells• Cadherin transmembrane adhesion proteins• Complex of anchoring proteins• Pemphigus autoimmune disease
Focal Adhesions
• Connect actin filaments to extracellular matrix
• Integrin transmembrane adhesion proteins
• Various anchor proteins
Hemidesmosomes
• Connect intermediate filaments to basal lamina
• Integrin transmembrane adhesion proteins
• Plectin anchor protein
Types Of Anchoring Junctions Junction Transmembrane Extracellular Cytoskeletal Intracellular
Adhesion Protein Attachment Attachment AnchorProtein
Cell-CellAdherens cadherins cadherin actin filaments cateninsJunction (E-cadherin) (- and -)
Desmosome cadherins cadherin intermediate catenins,(desmoglein, desmocollin) filaments desmoplakin
Cell-MatirxFocal integrins extracellular actin filaments talin, vinculin,adhesion matrix proteins others
Hemi- integrin 64 extracellular intermediate plectindesmosome matrix proteins filaments
Glycosaminoglycans
• Unbranched polysaccharide chain with repeating disaccharide unit
• Large volume, high negative charge result in gel-like form
• Most GAGs covalently attached to protein• Synthesized in Golgi apparatus• Link tetrasaccharide added to serine; other
sugars added one at a time
Proteoglycans
Collagens
• Multiple chains associate in different combinations
oProline- ring, stabilizes helixoGlycine- small, tight chain packing
• Triple helix from three collagen chains• Rich in proline and glycine
• Synthesized as pro--chain precursors• Cleavage of pro-peptides following secretion• Self-assembly into fibrils and aggregation into fibers
Synthesis of Collagens
Hydroxylation In Collagen
• Certain lysine and proline residues• Form interchain hyrodrogen bonds• Requires vitamin C; deficiency results
in easy bruising, petechiae, scurvy
Cross-Linking Of Collagen
• Occurs between lysine residues of separate molecules to strengthen fibrils
Genetic Diseases Affecting Collagen
AffectedDisease Collagen Mutant Phenotype
Osteogenesis imperfecta I weak bones, fractures
Chondrodysplasias II cartilage deficiency
Ehlers-Danlos syndrome III fragile skin & blood vessels, loose joints