cell-cell interactions Flashcards
what is the structure of tight junctions?
located at the apical end
composed of occludin/claudin/JAM dimer complexes
zona proteins act as a scaffold protein and anchor the tight junction to the actin skeleton
what is the function of tight junctions?
seals gap between neighbouring cells
adhere cells together
serve as a barrier to the free diffusion of water and molecules
some are permeable to specific ions or solutes
what are examples of tight junction diseases?
mutation in zo2 protein results in the mislocalisation of claudin resulting in non-functional bile cannaliculi which presents disease in the liver
irritable bowel disease
what are the symptoms of irritable bowel disease?
abdominal pain along with diarrhoea, constipation and a change in bowel habits
there are many secondary symptoms
what is thought to be the cause of irritable bowel disease?
claudin 2 functions in creating pores in the tight junction to allow paracellular permeability
it localises with zo proteins to form functional pores
in irritable bowel disease there is an increase in the amount of claudin 2 meaning more pores are formed which increases permeability which causes the symptoms
what method can be used to show levels of cell-cell adhesion proteins?
western blotting
what is irritable bowel disease also known as?
Crohn’s disease
what is the structure of gap junctions?
composed entirely of connexin which are organised into complexes known as connexons
two connexons from neighbouring cells join and form a communication tunnel
what is the function of gap junctions?
allow direct connection between two neighbouring cells
ions, molecules and electrical impulses can pass through allowing communication
what is the structure of adheren junctions?
compromised of primarily E-cadherin in epithelial cells
generation is mediated by proteins which directly influences the developments of other junctional complexes
how do adheren junctions inhibit Wnt signalling?
usually beta catenin forms part of the cadherin complex at the adheren junction where is acts as a conversion molecule for cadherin to F-actin
a lack of beta catenin inhibits Wnt signalling
axin cant be sequestered at the membrane and so cytoplasmic beta catenin cant translocate to the nucleus and transcribe proliferation genes
what is the structure of desmosomes?
compromised of desmosome intermediate filament complexes
has connecting filaments and cytoplasmic plaque which joins the cytoskeleton to the junction
what is the function of desmosomes?
they adhere cells together
where are desmosomes found in greater quantities?
in tissues that are subject to greater mechanical stress
