L27 Intermediate Filaments And Intracellular Junctions Flashcards
What are intermediate filaments
Rope like intermediate filaments are constructed of tetramers of rod like proteins that are tightly bounded in to long helical arrays
What are the categories for intermediate filaments
Kertains,desmin, vimentin, glial, fibrillary acidic protein, neurofilaments and nuclear lamins
How are intermediate proteins identified
By means of immunocytochemical methods and is a routine procedure to help identification of tumor origin
Types of intracellular junctions
Zonula: junctions completely encircle cells
Fascia: junctions form broad areas of contact between cells
Macula: junctions are spot welds on the cell surface
What are the common cell junctions according to function
▪️Occluding junctions: function in joining cells to form an impermeable barrier
▪️Anchoring junctions: function is maintaining cell to cell or cell to basal lamina adherence thus providing mechanical stability in tissues subjected to mechanical pressure
▪️communicating junctions: function in permitting movement of ions or signaling molecules between cells thus coupling adjacent cells both electrically and metabolically
How are they classified according to molecular struture
Zonula occludens
Zonula adherents
Desmosomes(macula adherents)
Gap junctions (nexus)
What are zonula occludens
▪️Tight junctions that form a belt like junction that encircles the entire circumference of the cell
▪️Established by fusion of outer layers of cell membranes of two cells in an UNINTERRUPTED pattern where fusion is represented by focal points
What happens in fusion sites of zonula occludens
Transmembrane junctional proteins called claudins and occludins bind to each other forming a seal
And third transmembrane protein celled cadherin reinforces other two types
What are zonula adherents
▪️Intercellular space between outer leaflets of two adjacent cell membranes is occupied by the extracellular moieties of cadherins
▪️intracytoplasmic aspect binds to a specialized region of cell web specifically a bundle of actin filaments
What are desmosomes
▪️spot weld like junctions that are randomly distributed along lateral cell membranes of adjacent cells
▪️disc shaped attachment plaques are located opposite each other on cytoplasmic aspects of plasma membranes of adjacent epithelial cells
How is disease pemphigus vulgaris produced and how is it treated
Autoantibodies against desmosomal proteins are produced resulting in the skin disease
They bind to desmosomal proteins and disrupt cell adhesion leading to widespread blistering and consequent loss of extracellular fluids
Treatment with systematic steroids or immunosuppressive agents
What are gap junctions
Built by 6 closely packed transmembrane channel forming proteins(connexins) that assemble to form channel structures called connexons
Whats the importance of connexons
When a connexon Of one plasma membrane fuses with another it forms an intracellular hydrophilic communication channel
