Intercellular Adhesions

• What are PROMINENT in epithelia?

  Junctions
• What provides a means for anchoring cells between adjacent epithelial cells and the basal laminae?

  Adhesions and junctions
• What are the 4 types of Intercellular adhesions and other junctions?

  Tight junctions, Adherins, Gap junctions, hemidesmosomes
• Tight junction is also known as what?

  Occluding junctions
• Adherens is also known as what?

  Anchoring junctions
• Tight or occluding junctions: form a seal between ADJACENT cells
• Adherens of anchoring junctions: sites of strong cell adhesion
• Gap junctions: channels for communication between adjacent cells
• Hemidesmosomes: anchors cells to the basal lamina
• Tight junctions are also known as what?

  Zonulae occludens
• What type of junction are the MOST APICAL?

  Tight junctions
• In tight junction, the seal between the two cell membranes is due to tight interactions between the transmembrane proteins what?

  claudins and occludin
• Tight junctions: serve as fences restricting movements of membrane lipids and proteins at the apical cell surface into the lateral and basal surfaces, and vice versa.
• Adherens junction is also known as what?

  Zonula adherens
• What type of junction is immediately below the TIGHT JUNCTION?

  Adherens junction
• Adherens junctions firmly anchors a cell to its neigbors mediated by what?

  Cadherins
• At their cytoplasmic ends, cadherins bind to what that link to actin filaments with actin-binding proteins?

  Catenins
• The actin filaments linked to the adherens junctions form part of the “TERMINAL WEB,” a cytoskeletal feature at the apical pole in many epithelial cells
• Desmosomes is also known as what?

  Macula adherens
• What type of junction resembles a single “spot-weld” and does not form a belt around the cell?

  Desmosomes
• Desmosomes: disc-shaped structures at the surface of one cell that are matched with identical structures at an adjacent cell surface - provide firm cellular ad
• Gap junctions: mediate intercellular communication rather than adhesion or occlusion between cells
• What type of junction is functionally important in nearly all mammalian tissues as, it permit intercellular exchange of molecules with small ( <1.5 nm) diameters?

  Gap junctions
• INTEGRINS of hemidesmosomes bind primarily to LAMININ molecules in the basal lamina
• Which among the junction has NO cytoskeletal component?

  Gap junction
• Gap junctions: allows DIRECT TRANSFER of small molecules and ions from one cell to another.
• Desmosome: Autoimmunity against DESMOGLEIN I leads to dyshesive skin disorders characterized by reduced cohesion of epidermal cells
• Gap junctions: Mutations in various CONNEXIN genes have been linked to certain types of DEAFNESS and peripheral neuropathy
• HEMIDESMOSOME: Mutations in INTEGRIN-B4 gene are linked to some types of EPIDERMOLYSIS BULLOSA, a skin blistering disorder
• DESMOSOME: Cadherin family proteins like desmogleins and desmocolin
• TIGHT JUNCTION: Seals ADJACENT CELLS to one another, controlling passage of molecules between them, separates apical and basolateral membrane domains
• What is the cytoskeletal component of tight junction?

  Actin filament
• Adherent junction: LOSS of E-cadherin in epithelial cell tumors (carcinomas) promotes tumor invasion and the shift to malignancy
• What type of cytoskeletal component do hemidesmosome have?

  Intermediate filaments
• What type of cytoskeletal component do adherent junction have?

  actin filaments
• Gap junction: connexin
• HEMIDESMOSOME: Integrins
• ADHERENT JUNCTION: Provides points linking the cytoskeletons of adjacent cells; strengthens and stabilizes nearby tight junctions
• ADHERENT JUNCTION: E-cadherin and catenin complexes
• HEMIDESMOSOME: Anchors cytoskeleton to the basal lamina