cell junction ad adhesion Flashcards
where are claudins found and what is their function?
claudins are the transmembrane proteins that make up tight junctions. they are expressed highly in renal tubules involved in calcium and magnesium reabsorbtion
what happens to a patient with a defect in claudins in terms of ion (Ca and Mg) levels in the blood
calcium and magnesium levels in the blood will be lower than a normal person and higher in urine because claudins are involved in calcium and Magnesium reabsorbtion and if they are not working, Ca and Mg will not be reabsorbed and thus will remain in the urine
what is the main adhesion protein that holds epithelial cells together? and where are they found?
cadherines (calcium dependent adherins). they are found in belt desmosomes
what are the steps to cadherin activation?
each caderin protein has 4 calcium binding spots. once all four spots are bound by calcium, the cadherin forms a dimer with another activated cadherin. the dimerizeation adheres epithelial cells together.
what is the clinical manifestation of removing calcium from epithelial tissue
cadherins need calium to bind to hold epithelial cells together. if there is no calcium, epithelial cells will not be held togehter and tissue cohesiveness will be distrupted.
if spot desmosomes and belt desmosomes are both made of cadherins, how do you dicipher which is the one for the spot desmosomes?
their names all have Plaque in it. desmoplaquin, plakoglobin, desmocollins, desmogleins
where are intermediate filaments found in an epithelial cell
they are found in the basal lamina
who is the protein intermediate for hemidesmosome binding to the basal lamina?
it is a protein called alpha-6-beta-4
what are focal adhesions made of and where are they found?
adhesion protein- integrins
cytoplasmic proteins-vinculin, talin
intermediate filament- actin
in pemphigus disease, which transmembrane protein is defective?
the desmogleins of spot desmosome causes loss of adhesion to nearby cells
Pemphigoid
defect in hemidesmosomes casues detachement of epithelial cells from basal lamina
what are some factors that regulate communications junctions?
pH, voltage, calcium, and other metabolites
what makes up a connexon?
multiple connexin proteins combine to form a channel called a connexon
how do you tell each cell adhesion type apart on EM?
a
what are the two examples of non junctional adhesion proteins? what do they do?
- selectins- play a inflamation and migration of lymphocytes.
- immunoglobulins (VCAm-1 and NCAM1)- play an important role in T cell migration
what role to Selectins and VCAM/NCAM play together in leukocyte adherance to epithelium?
they work as speed bumps at the spot of inflamation to slow down the leukocyte until it stops and binds to the seletin and the migrtes through the endothlium with the help f integrins in the basal lamina.
