Lecture 9: Trans-Golgi Network (TGN)

Question 1

TGN is the most ___

Answer 1

distal region of the golgi complex

Question 2

TGN functions to modify and sort ____ from ____ and proteins & lipids from ____

Answer 2

newly synthesized proteins & lipids
-proximal golgi
-endocytic compartments

Question 3

defects in sorting/release of cargo in TGN associated which diseases?

Answer 3

-autoimmune disease, cancer, neuropathology, diabetes

Question 4

______ of viral proteins affect pathogenesis

Answer 4

TGN processing

Question 5

major function of TGN

Answer 5

-sort proteins (localization) but also modifies proteins

Question 6

TGN is _____ & _____distinct from golgi stack

Answer 6

-morphologically & biochemically

Question 7

morphological differences between TGN and golgi stack

Answer 7

-tubular network and associated vesicles
-cisternae are not flattened against golgi stack
-cisternae has peeled away from trans cisternae of golgi stack

Question 8

biochemical differences between TGN and golgi stack

Answer 8

-osmium reduced by unsaturated lipids in cis-golgi (reducing environment)
-TGN has acid phosphatase (acidic environment)

Question 9

TGN is considered _____ by many reasearchers

Answer 9

separate entity

Question 10

evidence that TGN is separate

Answer 10

-TGN reacts differently to drugs and temperatures that impair protein/membrane trafficking

Question 11

BFA (Brefeldin A) causes ___ (for golgi stack +TGN)

Answer 11

-TGN fuses with endosomal membranes
-Golgi stack fuses with ER

Question 12

Membrane an protein cargo blocked in TGN and ER at which temperatures?

Answer 12

-TGN: 20 C
-ERGIC: 15 C

Question 13

Enzymes of TGN do what?

Answer 13

-terminal glycosylation
-sulfation
-endoproteolysis

Question 14

TGN: terminal glycosylation (def.) + why?

Answer 14

-addition of sialic acid to N-linked oligosaccharides by dialytransferase (ST)
-keeps negative charge on cell surface
-keeps water at cell surface

Question 14

TGN: sulfation (def.)

Answer 14

-addition of sulfate groups to Tyrosine
-can affect protein-protein interactions

Question 15

human brain is rich in ____

Answer 15

sialic acid (4X) for neurotransmission + memory

Question 16

loss of tyrosine sulfation can affect ___

Answer 16

blood clotting (VIII)

Question 17

Furin is ___

Answer 17

a transmembrrane protein in TGN that cleaves pro-proteins

Question 18

Furin cleaves where?

Answer 18

R-X-(R/X)-R

Question 19

Furin + COVID-19

Answer 19

-furin cleavage of spike protein promote intereaction of virus particles with receptor ACE2 by exposing receptor binding domain (RBD)

Question 20

presence of cleavage site associated with _____

Answer 20

highly pathogenic influenza virus strains

Question 21

furin cleaves what?

Answer 21

mammalian, viral, bacterial substrates

Question 22

furin inhibitors are good antivirals but there is a problem: ____

Answer 22

-furin does many important function in mammals but viruses take advantage of it

Question 23

TGN is a _____ site for proteins/lipids in eukaryotic cells

Answer 23

major sorting site

Question 24

3 main sorting pathways of TGN +examples + signal needed?

Answer 24

-to endosomes (ex. lysosomal enzymes) + signal needed -to secretory granules (ex. regulated secretion) + signal needed -constitutive transport to PM + no signal needed (except in polarized cells)

Question 25

Alzheimer disease (AD) is caused by ___ due to

Answer 25

accumulation of plaque that contain AB oligomers due to abnormal cleavage of amyloid precursor protein by B-secretase (makes AB oligomers)

Question 26

Production of AB oligomers happens in ___ because ____

Answer 26

-TGN -b-secretase which are normally localized in endosomes but decrease in GGA or increase in retromer make B-secretase localize in TGN

Question 27

AB plaques make by ___ (2)

Answer 27

-B-secretase -gamma-secretase

Question 28

If movement of beta-secretase to TGN ___ or b-secretase to endosome is ____, cleavage of APP increases

Answer 28

-increases -blocked

Question 29

normal cleavage of APP is by ___

Answer 29

a-secretase

Question 30

live cell imaging allows for ____

Answer 30

visualization of cargo and interaction with membrane compartments and cytoskeleton

Question 31

temperature blocks are useful for ___

Answer 31

synchronizing cargo flow

Question 32

temperature block of TGN

Answer 32

20 C

Question 33

coat protein for constitutive transport from TGN

Answer 33

-no known coat protein

Question 34

carriers size for constitutive transport

Answer 34

-large structure (170 -1700nm) (half size of cisternia) -variable size

Question 35

shape of carriers for constitutive transport

Answer 35

-pleiomorphic-tubular-saccular (10,000 cargo molecules) -

Question 36

constitutive transport is ____sensitive and regulated by ___

Answer 36

-BFA -ARFs (small GTPases)

Question 37

constitutive transport requires ___motores (____), ____and ___

Answer 37

-molecular motors -kinases -rabs

Question 38

kinesin help with the movement of ____

Answer 38

carriers

Question 39

constitutive transport to PM: sorting signals ___

Answer 39

not needed (default pathway)

Question 40

VSG is a ___ targeted protein

Answer 40

basolaterally

Question 41

post TGN cargo (constitive transport) travels along ____

Answer 41

microtubules

Question 42

for polarized cells, ____ are needed for transport to apical/basolateral membranes

Answer 42

different signals

Question 43

TGN structure is key to ____

Answer 43

its sorting ability

Question 44

TGN is organized into ____

Answer 44

subdomains of different proteins & lipids

Question 45

TGN enriched in _____ which serves as _____

Answer 45

-PI4P -binding platrom for proeins involved in cargo sorting + vesciel formation

Question 46

organization of TGN subdomains dependent on ____

Answer 46

Rab GTPases

Question 47

TGN domains that sort cargo to different places have ___

Answer 47

different residues

Question 48

sorting of proteins in TGN real time method

Answer 48

live-cell imaging

Question 49

temperature block permits _____

Answer 49

synchronization of traffic moving through TGN

Question 50

GPI protein targeted to _____

Answer 50

apical surface

Question 51

adenoviruses are good for studying ____`

Answer 51

cargo targeting from the TGN

Question 52

Fluorescence microscopy helps use determine ____

Answer 52

when cargo is sorted and transport routes and which compartments are involved

Question 53

Post-golgi carriers _____ with endosomes

Answer 53

-don't intersect

Question 54

regulated secretion are in response to ___

Answer 54

-signal (hormone/neurotransmitter)

Question 55

subset of secretory proteins (inslunin neurotransmittes) are ___ in

Answer 55

concentrated (200-400x) and stored in specialized from mature granules

Question 56

mature granules are from ___

Answer 56

maturation of immature secretory (ISGs)

Question 57

contents of MSG secreted in response to _____

Answer 57

extracellular simulates (ex. neurotransmitter)

Question 58

MSG has ____ (desc.)

Answer 58

dense core that contains high conc of protein

Question 59

proteins aggerate in response to ___ and ___ invitro

Answer 59

low pH and Ca++

Question 60

pH of TGN is ____ than golgi stack and has more ____

Answer 60

-lower -Ca++

Question 61

when regulated secretory protein is expressed in cell that doesn't normally express it, ______

Answer 61

protein enters regulated secretory protein suggesting that protein contain inherent targeting signals

Question 62

selection of regulatory secretory pathway: sorting by entry

Answer 62

-proteins destined for SG aggregate in special regions of TGN (high Ca++ and low PH (6.5) -may/may not be signal mediated -confirmation-dependent signal binds to receptor to TGN --> individual proteins/aggregates into ISGS

Question 63

selection of regulatory secretory pathway: sorting by retention

Answer 63

-non-regulatory secretory proteins removed by CCVs (clathrin coated vesicles) -removal results in maturation into MSGs

Question 64

clathrin coats on ISG & TGN: selection method

Answer 64

selection by entry and selection by retention

Question 65

clathrin coats on ISG OR TGN: selection method

Answer 65

only one selection method is right TGN: entry ISG: retention

Question 66

antibodies that recognize either forms of proinsulin/insulin can be used ___

Answer 66

to determine where processing of regulated secretory protein occurs in membrane compartments

Question 67

Immuno-electron microscopy (def.)

Answer 67

gold particles coated in protein A used to detect antibody bound protein by transmission electron microcopy

Question 68

Cpn60 localizes in _____

Answer 68

secretory granules in pancreatic cells

Question 69

TM shows that proinsulin processing ____

Answer 69

happens after it leaves TGN and granules mature