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EOM Test 2 > Protein Trafficking > Flashcards

Protein Trafficking Flashcards

1
Q

What are the three domains of the endoplasmic reticulum and their functions?

A

Smooth ER - lipid metabolsim

Rough ER - protein synthesis

ERGIC - vesicles exit to golgi

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2
Q

What are two destination pathways for proteins?

A

Cytosolic pathway

Secretory pathway

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3
Q

What are two ways proteins get into the ER?

A

Co-translational translocation

Post-translational translocation

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4
Q

What is the role of the signal recognition particle?

A

SRP binds the signal sequence, halting translation.

Also binds the SRP receptor on the RER

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5
Q

What is the function of the translocon?

A

To allow proteins to be translated into the ER and insert transmembrane portions into the membrane

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6
Q

What is the role of Hsp70 and Hsp40?

A

Maintains the protein in an unfolded state so that it can be transported to the ER.

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7
Q

What is the role of Sec62/63?

A

Recognizes the signal sequence of a completed polypeptide and causes translocon to open

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8
Q

What is the function of BiP?

A

Internal chaperone that acts as a molecular ratchet to drive translocation into the ER.

ATP-dependent

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9
Q

How does a transmembrane portion enter the membrane?

A

Exits the translocon laterally after it is translated.

Multiple domains mediated by SRP

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10
Q

What four protein processing mechanisms occur in the ER?

A
  • BiP mediates folding
  • Protein disulfide isomerase
  • N-linked glycosylation
  • GPI anchors
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11
Q

What are two types of export signals that trigger export from the ER to the golgi?

A
  • Di-acidic or di-hydrophobic AA signals in the cytosolic domain
  • GPI anchors
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12
Q

What is the ERES

A

Specialized region of the ER where proteins and phospholipids are exported.

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13
Q

How are proteins transported between the ER and golgi?

A

Proteins in the lumen of one organelle are packaged into budding transport vesicles, then released to the lumen of the recipient organelle

topology is maintained

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14
Q

What is the default pathway?

A

Pathway by which unmarked proteins in the ER can be packaged and transported to the golgi

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15
Q

What is the ERGIC?

A

ER-Golgi Intermediate complex

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16
Q

What is the role of the Golgi Apparatus?

A
  • Process and sort proteins coming from ER
  • Transport to endosomes, lysosomes, PM, or secretion
  • most glycolipids and sphingomyelin are synthesized here
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17
Q

What are the four regions of the Golgi and their functions?

A

Cis - receives molecules from the ERGIC

Medial and trans - modifications

Trans-Golgi network - sorting and distribution

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18
Q

What occurs to N-linked oligosaccharides

A
  • Mannoses are replaced with NAG, galactoses, and sialic acids
  • Fucose is added to origin NAG
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19
Q

How are the N-linked oligosaccharides of lysosomal proteins modified?

A

Mannose phosphorylation

Recognized by a mannose-6-phosphate receptor in the trans Golgi Netowrk

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20
Q

What is O-linked Glycosylation?

A

Carbohydrate addition ot serine and threonine in the Golge

21
Q

What happens to proteins that are destined to stay in the Golgi?

A

They are associated with the membrane and contain signals that prevent packaging and transport

22
Q

What are the three routes that transport from the Golgi to the cell surface can occur?

A
  • Direct transport
  • Recycling endosomes
  • Regulated secretory pathways
23
Q

What is regulated release and what types of molecules are regulated this way?

A

Contents are stored in granules until signals direct their fusion with the PM

Hormones and neurotransmitters

24
Q

What is the function of COPII-coated vesicles?

A

Carry proteins forward from the ER–>ERGIC–>Golgi

25
Q

What is the function of COPI-coated vesicles?

A

Bud from ERGIC or Golgi and carry their cargo backwards to earlier compartments

26
Q

What is the function of clatherin-coated vesicles?

A

transport in both directions between the trans Golgi network, endosomes, lysosomes, and PM

27
Q

What is the KDEL sequence?

A

Tags ER-resident soluble proteins for return to the ER by COPI vesicles

28
Q

What is the role of Mannose 6-phosphate?

A

Tags soluble lysosomal enzymes and secreted lysosomal enzymes for transport to lysosomes via Clatherin coated vesicles

29
Q

What are ARF1 and Sar1?

A

Small GTP-binding proteins that regulate the formation of coated vesicles

30
Q

How are clatherin-coated vesicles formed?

A
  • GEF activates ARF1
  • ARF binds an adaptor protein
  • The adaptor protein binds the cargo
  • Clatherin binds to the adaptor protein
31
Q

What mediates interaction between transport vesicles and target membranes?

A

Tethering factors

Rab proteins (small-GTP binding porteins)

32
Q

What three things drive membrane fusion?

A

vSNARES

tSNARES

Dynamin

33
Q

How do vesicles dock?

A

Active Rab proteins bind membrane tethering factors

Tethering factors bind coat proteins and the coat is removed.

34
Q

How do vesicles fuse?

A

The membranes are pulled together and fused via vSNARES and tSNARES interacting

35
Q

What is the mechanism of vSNARE and tSNARE interaction?

A

SNARE proteins have a central coiled-coil domain

Responsible for zipping the two SNARES together

36
Q

What are lysosomes?

A

membrane-enclosed organelles containing enzymes to break down all types of biological polymers

37
Q

What are lysosomal storage diseases?

A

Diseases that result from mutations in lysosomal enzymes

undegraded material accumulates in the lysosomes

38
Q

Most lysosomal enzymes are…?

A

Acid Hydrolases active at pH 5

39
Q

What is the significance of lysosomal enzymes only being active at pH 5?

A

Prevents cell contents digestion if the lysosome membrane breaks down

40
Q

How does material for digestion get into the cell?

A

Endocytosis

41
Q

How are lysosomes formed?

A

When transport vesicles fuse with a late endosome

42
Q

What two pathways intersect at endosomes?

A

Secretory and endocytic pathways

43
Q

What is the function of early endosomes?

A

Fuse with endocytic vesicles from PM

Separate molecules for recycling from molecules destined for degradation in lysosomes

44
Q

What is the function of recycling endosomes?

A

Serve as a site for molecules that are to be transported back to the plasma membrane

45
Q

What is the function of late endosomes?

A

Carry molecules to be degraded by lysosomes

46
Q

What happens during the maturation of late endosomes?

A

Transport vesicles carrying acid hydrolases fuse with late endosomes, forming lysosomes

47
Q

What are phagolysosomes?

A

Specialized lysosomes in phagocytic cells

48
Q

What is autophagy?

A

Digestion of the cell’s own components

49
Q

What normal roles does autophagy play?

A

Nutrient starvation - reutilized nonessential cellular components

Apoptosis

EOM Test 2 (20 decks)

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