REINHART 2 Flashcards
how is an epithelial tube formed?
start from a sheet of epithelial cells
epithelial cells are invaginated caused by a tightening along adhesion belts by actin
epithelial tube pinches off
can make a neural tube (very early central nervous system development)
how are two cells anchored to each other
vacherin family proteins (desmoglein/desmocollin) bind to each other with homophonic binding
those are attached to the anchoring complex (cytoplasm plaque made of intracellular anchor proteins such as desmoplakin, plakoglobin, plakophilin)
those anchoring complexes are themselves attached to keratin filaments
how is the anchoring complex organised
plakoglobin (80kDAa) is attached to either desmoglein or desmocollin
desmoplakin (260-330kDa) is a dimer, coiled coil bridge to intermediate filaments, found in and out the cell
what are the coiled coil interactions that hold that structure together?
hydrophobic interactions with amino acids inside
ionic interactions with other side chains
the outside side chains are polar and interact with water
how does immunofluorescence work?
primary antibody against a certain something
secondary antibody against the primary antibody, marked with fluorescent dye
visualise
how are epithelial cells anchored to the basement membrane (basal lamina)?
inside the cell:
intermediate filament (keratin for a skin cell)
pectin (anchoring protein)
outside;
a6b4 integrin (heterodimer)
on the basement membrane: laminin
collagen (IV)
those two are always in the basement membrane
what is the difference between desmosomes and hemidesmosomes?
Desmosomes are junctions involved in intercellular adhesion of epithelial cells and hemidesmosomes are junctions involved in adhesion of epithelia to basement membranes.
what are gap junctions?
connect two cells
things can go through the junctions
(tested with fluorescent dyes of different sizes)
what size of molecules can go through gap junctions and what types of molecules are those?
smaller than 1kDa can go through without problem
protons (pH)
Amino acids
monossaccharides (sugars)
small vitamins
ATP
what types of molecules cannot go through the gap junctions?
proteins, enzymes, RNA
what is the size of the gap, and what is the width of the channel?
gap of 2-4nm
channel is 1.5nm in diameter
what is the structure of connexin?
4 pass transmembrane proteins
the N and C termini are in the cytosolic side
how many different connexins are there?
21
what is the size of connexins?
20-60kDa
what are connexons?
made of six connexins
can be homomeric or heteromeric
