Lecture 13: Polarized cells

Question 1

epithelial tissue (def.)

Answer 1

One of the major tissues types in human body—covers all surfaces…inside and out as well as forming glands (mammary) and organs (liver, lung)

Question 2

epithelial tissue functions

Answer 2

Protection
* Absorption,
* Secretion
* Sensory reception

Question 3

apical surface of epithelial tissue faces ___

Answer 3

outside world

Question 4

basolateral surface of epithelial tissue faces ___

Answer 4

ajacent cells and underlying CT and blood vessels

Question 5

loss of cell polarity in epithelial tissue lead to ___

Answer 5

metastatic phenotype!

Question 6

Carcinoma (def.)

Answer 6

type of cancer that develops from epithelial cells

Question 7

adenocarcinoma (def.)

Answer 7

cancer that forms in the glandular tissue

Question 8

cancer doesn’t form in ___

Answer 8

cells that don’t divide (ex. neuron)

Question 9

apical and basolateral membrane of epithelial tissue are _____ because ____

Answer 9

compositionally distinct because they are separated by tight junctions (creating membrane polarity)

Question 10

tight junctions do what?

Answer 10

restricts movement of macromolecules between cells
allow for directional movement of nutrients

Question 11

Establishment and maintenance of cell polarity in epithelial tissue involves ____

Answer 11

sorting at the TGN to apical/basolateral side

Question 12

studying epithelial cells requires ____ to identify Apical and Basolateral sorting signals

Answer 12

compartmentalized culture system

Question 13

compartmentalized culture system (descri.)

Answer 13

has monolayer of MDCK cells (highly polarized)
apical medium and basal medium
sits porous filter

Question 14

MDCK cells stands for ____

Answer 14

Madin-Darby Canine Kidney epithelial cells

Question 15

limitations of MDCK cells

Answer 15

less dog reagents available

Question 16

GH is a ___

Answer 16

non glycosylated secretory protein (usually)

Question 17

adding glycosylation sites to GH does what?

Answer 17

increase secretion to apical side

Question 18

blocking glycosylation of GH12 (glycos.) with tunicamycin results in what?

Answer 18

non-polarized secretion

Question 19

apical sorting signals

Answer 19

-N or O-linked carbohydrate in ectodomain (membrane protein)
-transmembrane GPI domain (membrane protein)

Question 20

ectodomain (def.)

Answer 20

part of membrane protein that faces extracellular space

Question 21

mechanism of apical sorting

Answer 21

partitioning in glycosphingolipid-cholesterol (lipid rafts) rafts in TGN with TGN-localized lectin as receptors

Question 22

Apical sorting is a ____ process in TGN which suggest that it uses ___

Answer 22

-saturable
-receptors to recruit cargo

Question 23

Lectins are defined as ____

Answer 23

proteins that bind to carbohydrates

Question 24

Lectin in TGN bind to ____ and partition into ____ for apical sorting

Answer 24

oligosaccharides
lipid rafts

Question 25

other pathway for apical sorting

Answer 25

biosynthetic (direct) route- directly from protein production -NSF-independent , SNARES, tethering factors

Question 26

PM is rich in ___ (from TGN)

Answer 26

lipid rafts

Question 27

RNAi knockdown of Galectin-3 causes ____

Answer 27

apically targeted membrane proteins to be found on basolateral side, suggesting that it is an apical sorting receptor

Question 28

Cation dependent M6P receptor (goes to _______)

Answer 28

basolateral surface/endosomes

Question 29

lysing cells with gentle non-ionic detergent retains ____

Answer 29

antibody-protein interactions

Question 30

antibody-protein can be recovered with ___ + detected (radioactive proteins) with ____

Answer 30

protein A sepharose SDS page + autoradiography

Question 31

Basolateral sorting like apical soring is ____

Answer 31

saturable (uses receptors)

Question 32

Basolateral sorting signals are found in ____

Answer 32

cytoplasmic regions of membrane proteins (need to be exposed to cytoplasm)

Question 33

basolateral sorting motifs are ___ which are similar to ___

Answer 33

tyrosine and di-leucine-based motifs endocytic/lysosomal targeting motifs

Question 34

other route for basolateral sorting

Answer 34

biosynthetic (direct) route- directly from protein production -NSF-independent , SNARES, tethering factors

Question 35

AP-1 adaptor protein + basolateral sorting

Answer 35

contain µ1B rather than µ1A which is part of “regular” AP1 complex sorted to basolateral side

Question 36

argeting to apical and basolateral domains requires ____Rabs, SNARES and tethering factors

Answer 36

different

Question 37

sorting signal hierarchy

Answer 37

Basolateral signals dominant>>>Apical sorting occurs in the absence of basolateral sorting signals

Question 38

Caveolae (general def.)

Answer 38

invaginations of apical plasma membrane (distinct morphology)

Question 39

Caveolae abundant on ____ and ___ cells

Answer 39

-endothelium and smooth muscle

Question 40

Caveolae absent in ___

Answer 40

lymphocytes, RBCs

Question 41

Caveolae coating description

Answer 41

striated

Question 42

Caveolae are a type of ____ containing the protein ____

Answer 42

lipid raft caveolin

Question 43

lipid rafts are present at ___ and ___

Answer 43

PM and TGN

Question 44

lipid raft properties

Answer 44

-rich in cholesterol and sphingolipids -rich in GPI anchored proteins -thicker regions

Question 45

not all ___ are caveolae but all caveolae are _____

Answer 45

lipid rafts

Question 46

_____ can determine lipid raft association

Answer 46

Membrane anchoring domains

Question 47

influenza virus and caveolae

Answer 47

HA and NA proteins of flu virus concentrate in lipid rafts to bud off, important for virus entry too

Question 48

Caveolin is a ____ that localizes at ___

Answer 48

* 21 kD phosphoprotein caveolae

Question 49

forms of caveolin

Answer 49

Cav-1,2 - form heterodimers Cav-3 (present only in muscle cells)

Question 50

expression of which caveolin promotes caveolae formation

Answer 50

Cav-1 Cav-3

Question 51

disruption of cholesterol in membranes by this drug prevent caveolae formation?

Answer 51

filipin (flattened structures)

Question 52

without ____ in membrane, caveolae can't form

Answer 52

cholesterol

Question 53

how caveolin forms caveolae

Answer 53

-caveolin forms hair pin in membrane (N/C termin. in cytoplasm) -binds cholesterol & sphingolipids -oligomerizes with 14-16 subunits -palmitoylated near C-termin.

Question 54

caveolae can form ____ structures

Answer 54

interconnected

Question 55

knout out caveolin-1 gene in mice results

Answer 55

-no caveolae in vascular endothelial cells -leaner, resistant to high fat -more fatty acids in blood serum (enlarged heart) -insulin resistance -hypersensitivity to cancer

Question 56

insulin resistance and caveolin-1

Answer 56

mutation in caveolin-binding domain of insulin receptor caveolin stabilizes insulin receptor

Question 57

caveolin and cancer

Answer 57

-caveolin-1 might be tumour suppressor -dominant-negative mutation in gene in some breast cancer

Question 58

are caveolae dynamic + involved in endocytosis?

Answer 58

yes

Question 59

caveolae and endocytosis

Answer 59

-GTP hydrolysis required -colocalize with intersectin (scaffolding) and dynamin (fission) at their necks

Question 60

where does intersection and dynamin localize in caveolae

Answer 60

-necks of caveolae

Question 61

Labelled _____can be used to follow caveolae-dependent transport

Answer 61

CTxB (Cholera toxin b-chain subunit )

Question 62

_____ is required for budding of caveolae from PM

Answer 62

dynamin (interconnected structure still forms without dynamin)