polarity

Question 1

what polarity do epithelial cells have?

Answer 1

apical-basal polarity resulting from distribution of components

Question 2

what does apico-basal polarity depend on?

Answer 2

action of par complex, crumbs complex, and scribble complex (all are mutually inhibitory)

Question 3

what “locks” the asymmetry in place?

Answer 3

tight junctions (cadherins) which acts as fences against transmembrane diffusion

Question 4

what is the main effector of apical identity?

Answer 4

aPKC (phosphorylates junctional and lateral polatiy factors)

Question 5

what does the phosphorylation of Lgl inhibit?

Answer 5

its association with other proteins in the complex (aPKC inactivates Lgl)

Question 6

what is Baz/Par-3?

Answer 6

scaffold for cadherins (propagate polarity in an epithelial to keep all cells polarized equally)

Question 7

what does crumbs complex do?

Answer 7

it is the only transmembrane protein and links aPKC to membrane

Question 8

what does loss of apicobasal polarity do?

Answer 8

overproliferation and metastasis

Question 9

what is the epithelial-mesenchymal transition (EMT)?

Answer 9

process where epithelial cells lose their polarity and adhesion, and gain migratory and invasive properties

Question 10

what are tumour cells?

Answer 10

mutated genes that lead to uncontrollable proliferation

Question 11

what happens to scribble complex mutants?

Answer 11

they overprofilferate

Question 12

what was the first tumour suprpesor gene?

Answer 12

lethal giant larvae

Question 13

what is an imaginal disc?

Answer 13

sac epithelial structure in insect larva that overprofilerate (form tumours) without AP polarity

Question 14

what is PCP?

Answer 14

planar cell polarity - the coordinated polarisation of cells within plane of tissue

Question 15

what controls hari oreintation?

Answer 15

planar cell polarity

Question 16

what is PCP controlled by?

Answer 16

core pathway and Ds-Ft pathway

Question 17

what happens to PCP mutants?

Answer 17

disorganzied cell strucutres (trichomes)

Question 18

what is the core pathway?

Answer 18

has six proteins that form asymmetrically localized intercellular complexes

Question 19

how do the core proteins self-organize?

Answer 19

into mutually antagonistic sides

Question 20

what do actin-binding proteins do?

Answer 20

restrict formation of actin-rich trichome to one side

Question 21

what does the Ft-Ds pathway do?

Answer 21

aligns entire tissue

Question 22

what is the Ft-Ds pathway?

Answer 22

are atypical cadherins (heterophilic complexes)

Question 23

what drives asymmetric localization of Ft and Ds?

Answer 23

expression gradient of Fj (phosphorylates extracellular cadherin repeats) and Ds (modifies binding affinities)

Question 24

what drives asymmetric cellular localization of core proteins?

Answer 24

usually a global cue