polarity Flashcards
what polarity do epithelial cells have?
apical-basal polarity resulting from distribution of components
what does apico-basal polarity depend on?
action of par complex, crumbs complex, and scribble complex (all are mutually inhibitory)
what “locks” the asymmetry in place?
tight junctions (cadherins) which acts as fences against transmembrane diffusion
what is the main effector of apical identity?
aPKC (phosphorylates junctional and lateral polatiy factors)
what does the phosphorylation of Lgl inhibit?
its association with other proteins in the complex (aPKC inactivates Lgl)
what is Baz/Par-3?
scaffold for cadherins (propagate polarity in an epithelial to keep all cells polarized equally)
what does crumbs complex do?
it is the only transmembrane protein and links aPKC to membrane
what does loss of apicobasal polarity do?
overproliferation and metastasis
what is the epithelial-mesenchymal transition (EMT)?
process where epithelial cells lose their polarity and adhesion, and gain migratory and invasive properties
what are tumour cells?
mutated genes that lead to uncontrollable proliferation
what happens to scribble complex mutants?
they overprofilferate
what was the first tumour suprpesor gene?
lethal giant larvae
what is an imaginal disc?
sac epithelial structure in insect larva that overprofilerate (form tumours) without AP polarity
what is PCP?
planar cell polarity - the coordinated polarisation of cells within plane of tissue
what controls hari oreintation?
planar cell polarity
what is PCP controlled by?
core pathway and Ds-Ft pathway
what happens to PCP mutants?
disorganzied cell strucutres (trichomes)
what is the core pathway?
has six proteins that form asymmetrically localized intercellular complexes
how do the core proteins self-organize?
into mutually antagonistic sides
what do actin-binding proteins do?
restrict formation of actin-rich trichome to one side
what does the Ft-Ds pathway do?
aligns entire tissue
what is the Ft-Ds pathway?
are atypical cadherins (heterophilic complexes)
what drives asymmetric localization of Ft and Ds?
expression gradient of Fj (phosphorylates extracellular cadherin repeats) and Ds (modifies binding affinities)
what drives asymmetric cellular localization of core proteins?
usually a global cue
