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Biochemistry Exam 3 > Intracellular Vesicular Transport > Flashcards

Intracellular Vesicular Transport Flashcards

0
Q

Three types of coated vesicles

A

Clathrin
COPI
COPII

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1
Q

Three steps of vesicular transport

A

Particular region of membrane pinches off to form coated vesicle
Vesicle finds and docks on its target compartment
Fusion of the membranes from the vesicle and target compartment

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2
Q

Where do clathrin coated vesicles transport to/from?

A

From golgi to ER
from plasma
Endosomes as well

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3
Q

Where does COPI transport from/to?

A

From Golgi to ER

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4
Q

Where does COPII transport from/to?

A

From ER to golgi

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5
Q

Describe the structure made by clathrin

A

Three heavy chains and three light chains that form a three legged structure called a triskelion

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6
Q

What is adaptin?

A

Coat protein that function as link between clathrin and various transmembrane receptors. At least 4 types specific for different set of cargo receptors

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7
Q

What is dynamin?

A

A GTP-ase that helps the clathrin coated vesicle bud

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8
Q

When is the clathrin coat lost?

A

Shortly after budding

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9
Q

ARF protein does what?

A

Helps with assembly of COPI and clathrin coat assemblies. GTPase

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10
Q

Sar1 protein does what?

A

GTPase required for COPII coated vesicle formation

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11
Q

What three complexes guide transport vesicles to target membranes?

A

t-SNARE, v-SNARE, and GTPase Rabs

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12
Q

What is the SNARE hypothesis?

A

v-SNARE (vesicle) and t-SNARE (target) are complementary. The fitting together is monitored by GTPase Rab protein. When docking connection lasts long enough, Rab is able to hydrolyze its GTP to GDP leading to a lock of the vesicle. NSF then induces the two membranes to fuse.

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13
Q

What is required to separate fused SNAREs?

A

NSF, pries apart interacting SNAREs so they can be used again

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14
Q

How to viruses fuse into cells?

A

Chemokine interaction with the virus allows for membrane insertion ad fusion of the membrane and nucleocapsid release into cell

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15
Q

Transport from the ER is mediated by what coat protein?

A

COPII

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16
Q

COPII coated vesicles do what?

A

Quickly shed coat after formation and then quickly fuse together on their way to the cis-golgi network

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17
Q

Retrieval of soluble ER resident proteins back to the ER is accomplished by?

A

KDEL receptors

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18
Q

As we move from ER towards the trans Golgi network, the pH gets?

A

More acidic

19
Q

How is retrograde ER transport acheived?

A

KDEL signals (lys-asp-glu-leu) bind to KDEL receptors and are packaged into COPI coated vesicles and move back to Golgi. KDEL sequence on C-terminal

20
Q

Describe the constitutive secretory pathway

A

Default pathway of protein secretion. Used by all cells. Supplies plasma membrane proteins and lipids. Involved in exocytosis

21
Q

Describe the regulated secretory pathway

A

Specialized secretory cells sort proteins and selective package them into secretory vesicles at the TGN through clathrin coated vesicles. Proteins are greatly condensed and proteolytic cleavage occurs. These are released upon trigger

22
Q

Membrane recycling is facilitated by what coat?

A

Clathrin

23
Q

Where are proteins concentrated into vesicles?

A

TGN

24
Q

Three best understood pathways of protein sorting in the TGN

A

Signal mediated diversion to lysosomes
Constitutive secretory pathway
Signal mediated diversion to secretory pathway

25
Q

What are synaptogamin and syntaxin?

A

The v-SNARE and t-SNARE equivalents, respectively, at the synapse

26
Q

What is Rab3?

A

A synaptic vesicle specific G-protein

27
Q

Two types of endocytosis

A

Phagocytosis

Pinocytosis

28
Q

Where does phagocytosis occur?

A

Macrophages and neutrophils

29
Q

T or F: Receptor mediated endocytosis occurs in coated pits

A

T, usually clathrin

30
Q

T or F: Pinocytosis occurs in all cells

A

T, except for RBC or other few exceptions

31
Q

What is non-selective pinocytosis?

A

Fluid phase uptake of ECM

32
Q

What is receptor-mediated pinocytosis?

A

Take up of macromolecules

33
Q

Describe receptor mediated endocytosis of LDL

A

Binding of LDL to receptor in clathrin coated pit. Pinched off. Uncoating. Fusion with endosome. Separation of LDL from receptor. Aggregation of receptor to endosome to return to membrane. Transfer of LDL to lysosome. Degradation of apo B and cholesterol ester leading to reduction in HMG-CoA reductase and receptor number

34
Q

One receptor mediated defect in familial hypercholesteremia

A

LDL receptor does not accumulate in clathrin pit. Mutations in cytoplasmic domain.

35
Q

What sequence is required for LDL clathrin interaction?

A

Phe-Arg-X-Tyr on the C-terminus of LDL for adaptin binding

36
Q

Three outcomes of endocytosis

A 
Receptor recycles (LDL, transferrin)
Receptor degraded (ligand too)
Transcytosis (Epithelial cells transfer from one ECM to other)
37
Q

Describe transferrin pathway

A

Transferrin binds Fe ions in ECM at 7 pH. Loaded and delivers to endosome. Acidic pH dissociates to apotransferrin. Apotransferrin brought back to surface. Iron released to cell

38
Q

Describe how IgG gets from mom to baby

A

Transcytosis to the ECM through epithelial out from intestinal lumen. Gut is 6.0 and ECM is 7.0. Binds at low pH and released at high pH

39
Q

T or F: Growth factor receptors are recycled

A

F, not usually

40
Q

Describe EGFR process

A

not in coated pits de-facto, dimerize with ligand, both are degraded. This is down-regulation. Only accumulate in pits following dimerization

41
Q

Describe maturation of endosome from plasma membrane on

A

Early endosome, Late endosome, endolysosome, lysosome

42
Q

What is a lysosome?

A

Contains wide range of hydrolases. All acidic. pH optimum around 5.

43
Q

Three pathways to degradation in lysosomes

A

Endocytosis
Phagocytosis
Autophagy

44
Q

How are lysosomes formed?

A

Lysosomal proteins synthesized in the RER and transported through golgi. Tagged with mannose-6-phosphate on the N-terminal in the cis-Golgi by N-acetylglucosaminephosphotransferase and N-acetylglucosaminylphosphodiesterase

45
Q

What protein coats lysosomes from the TGN?

A

Clathrin

46
Q

What is inclusion cell disease?

A

Faulty lysosomal targeting. Lack of GlcNAc-phosphotransferase (first step of mannose-6-P). Lysosomal enzymes are secreted out of cell by default pathway

Biochemistry Exam 3 (11 decks)

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