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ANAT 212 pre midterm > Professor Uglade Lecture 12 > Flashcards

Professor Uglade Lecture 12 Flashcards

1
Q

What is in the secretory pathway for vesicle traffic?

A

multiple donor and acceptor (target) membranes in secretory pathway

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2
Q

What are the 2 mechanisms that ensure that vesicles transport thei contents to the correct acceptor membrane?

A

-Rab GTPase proteins provide specificity of vesicle targeting and attachment to acceptor membrane
-SNARE fusion proteins provide specificity during fusion of vesicles with acceptor membrane

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3
Q

How is the golgi organized, what maintains this?
What is the old model vs the new model of vesicle transport in golgi?

A

-into a stack of membranes:cis, medial, trans
-cytosolic protein matrix maintains the stacks
-old model: vesicles transport cargo between layers
-new model:each layer matures and becomes the next layer

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4
Q

How does the new model of transport through golgi work?

A

-golgi resident proteins are carried backwards by COP-I vesicles
-then clathrin coated vesicles carry cargo to PM and endosomes

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5
Q

How are N-linked glycans modified in golgi?

A

-modified by removal of mannoses and addition of diff sugars, often with negative charge

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6
Q

How are other oligosaccharides attached?
What is many combinations of oligosaccharides called?

A

-attached to Ser and Thr side chains (O-linked glycosylation)
-heterogeneity

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7
Q

How does glycoylation promote protein folding?

A

-makes folding intermediates more soluble (prevents aggregation)
-sequential modificatoins–>Glyco-code–>progression folding or degeneration

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8
Q

How does sugars having limited flexibility aid the golgi?
What else does glycosylation contribute in golgi function?

A

-they protect from proteases, stabilizes protein structure (protective coat)
-it is a signaling hub (regulation of development)

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9
Q

What happens to the some PM and extracellular proteins that are made as longer inactive forms in the ER?
WHat do proprotein convertases/proteases recognize?

A

-they are cut by proprotein convertases into shorter active forms in the golgi
-they recognize the pattern of amino acids and cleave to get rid of inhibitory part, to make the protein active

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10
Q

How is proinsulin an example for proprotein convertase use?

A

-Proinsulin is made as one inactive polypeptide, to prevent premature signaling by insulin at the ER
-convertases remove the middle section, the 2 remaining sections form active insulin

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11
Q

How do proteases regulate the golgi traffic?

A

ATF6 is activated by converyase proteolysis in the Golgi
-regulation is by trafficking
-BiP covers ER exit signalon ATF6, and proteases are only in the golgi

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12
Q

What are Rab-proteins?
What type of things in the cell have sets of rab proteins?

A

-large subfamily of Ras-related proteins
-different organelles and vesicles types in the secretory pathway have unique sets of Rab proteins

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13
Q

What are Rab proteins turned on and off by?
What does Rab-GTP bind?

A

-switched on by GEF, switched off by GAP
-RAB-GTP binds to a large number of rab effector proteins which mediate vesicle targeting

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14
Q

Where do Rab proteins act in?
What do they assist with and connect?

A

-Rabs can act at several steps in vesicle targeting
-they assist cargo selection and coat formation during vesicle budding
-they connect vesicle to motors on cytoskelton for transport
(diff rab is used in each step)

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15
Q

What do Rabs thether and recruit?

A

-they thether vesicles to the acceptor membrane for specificity
-they recruit SNARE fusion proteins

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16
Q

What are Rabs composed of/where?
What is Rab in the GDP-bound state?
what hides the lipid and prenyl group?

A

-rabs have 2 prenyl lipid groups attached at their C-termini (prenylation)
-In the GDP bound state Rab is soluble and not associated with the membrane
-lipid and prenyl group is covered up by other proteins (GDI, GDF) when interacting with Rab

17
Q

What happens to Rab in the GTP-bound state?
What happens to the Rab effector proteins?

A

-the lipid modifications are exposed and anchor Rab to the membrane
-the Rab effector proteins become attached to the membrane through Rab-GTP

18
Q

How is Rab activated?

A

A specific GEF on membrane produces anchored, active Rab-GTP
-GEF is linked to the formation of vesicle coat

19
Q

How does Rab-GTP work through effector proteins?
How is more Rab-GTP made?

A

-attaches vesicle to motor proteins
-tethers vesicle to target membrane
-activates PI kinases and GEFs to make more Rab-GTP in clusters on acceptor membrane

20
Q

1.What activates vesicle Rab, what does Rab interact with?

A

GEF on the donor membrane activates GEF and packages onto vesicles
-some interact with cargo, assist uncoating, or attache motors

21
Q

2.What happens after Rab is activated, where does it bind?

A

-vesicle Rab-GTP binds specifically to tethers on acceptor membrane

22
Q

What occurs after Rab tethering on acceptor membrane?

A

-after fusion to membrane, GAPs (GTPase-activating proteins) on target membrane inactivate Rab

23
Q

What happens in vesicle Rab cycle after Rab is inactivated?

A

inactiavted vesicle Rab-GDP is recycled through cytosol to donor membrane

24
Q

what provides structure to the cells?

A

cytoskelton-protein filament (actin) and microtubules (tubulin) run through cytosol and provide strcuture to cells

25
Q

What is the difference between actin filaments (AF) and microtubules (MT)?
How are they both connected?

A

AF-shorter, often clustered at PM, highly crosslinked into network, and they anchor organelles
MT-longer, thicker, organized around centrosome near nucleus
-they are both connected to each other and anchored to organelles and PM (cortical cytoskeleton)

26
Q

Where do motor proteins transport vesicles?
Where are the motor proteins?
What energy do they rely on?

A

-transport vesicles along cytoskeleton
-myosins on actin
-dyneins and kinesins on microtubules
-different families and mechanisms but are all ATP-dependent

27
Q

DO motor proteins provide specificity?

A

-they dont provide spcificity, but bring vesicle to general location of acceptor membrane

28
Q

What do many Rab effectors act as?

A

-many act as thethers-which are long proteins that connect the vesicle with its acceptor

29
Q

where are tethers bound on Rab?
What is the site on the acceptor membrane?

A

-tethers are bound to a specific vesicle Rab on one end, and a specific membrane site on the other end
-site on acceptor is a Rab in some cases, different proteins in other cases

30
Q

What do tethers determine?

A

they are the first determinant of vesicle targeting specificity

31
Q

What are the different types of tethers?

A

-coiled coiled tethers and multisubunit tethers?

32
Q

where do coiled coiled tethers act?
where do multisubunit tethers act?

A

-coiled-coiled tethers mostly withtin the Golgi and on endosomes
-multisubunit tethers act at other compartments
-ER to/from golgi
-Golgi to PM
-Endosome and Lysosome

33
Q

What are coiled coiled tethers composed of?
What do they form/maintain?
What do they connect?

A

-they are composed of 2 alpha helices
-they form the golgi matrix, and maintain the organization of the golgi stack
-they connect vesicles to the Golgi

34
Q

where are coiled coil tethers anchored, what do they have on them?

A

-anchored to membrane, or attached by GTPases (always around the golgi to recruit rab)
-long filaments with multiple Rab binding sites

35
Q

For what pathways are multisubunit thethers used for, and what proteins are used for each?

A

-ER to Golgi within the golgi (TRAPPI, and TRAPII)
-endosome and lysosome (HOPS/CORVET)
-ER and PM: CATCHR family (exocyst, GARP, COG, Dsl1)

36
Q

How does TRAPPI work when going from ER to Golgi?
What does it act with, bind, thether and organize?

A

TRAPPI works together with coiled coiled thether p115
1. TRAPPI acts as GEF for Rab1 on golgi
2. Rab binds coiled coiled (CC) tether
3. CC tether binds to vesicles and hands vesicles to TRAPPI, closer to membrane
4. TRAPPI helps organize SNAREs

37
Q

How does exocyst at PM (CATCHR family) work?
-Where are the subunits, what forms the tether, what does it bring to start fusion?

A
  1. before tethering but after uncoating, some subunits are on either vesicle or PM
  2. complete 8-mer complex forms tether
    3.may bring SNARE to membrane to start fusion

ANAT 212 pre midterm (9 decks)

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