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Advanced molecular & cell L2 > Lecture 12 - Principles of vesicular transport > Flashcards

Lecture 12 - Principles of vesicular transport Flashcards

1
Q

What is a good model for transport vesicle formation?

A

COPII coated vesicles

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2
Q

How accurate are vesicles to getting to their destination?

A

Vesicles are targeted with high fidelity to their destination

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3
Q

What is transport mediated by?

A

Vesicles and tubules

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4
Q

What 3 things can coat transport vesicles?

A
  • clathrin
  • COPI
  • COPII
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5
Q

Where do clathrin coated vesicles transport from and to?

A

from the plasma membrane to the endosome (a type of intracellular vesicle), and also in transport between different compartments of the Golgi apparatus.

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6
Q

Where do COPI coated vesicles transport from and to?

A

from the Golgi apparatus back to the endoplasmic reticulum (ER), or between Golgi compartments

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7
Q

Where do COPII coated vesicles transport from and to?

A

from the ER to the Golgi apparatus

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8
Q

What are the 3 essential components for all transport vesicles formation?

A
  • GTPase
  • adaptor proteins
  • coat
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9
Q

What are small GTPases?

A

molecular switches

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10
Q

Where is GTP usually found?

A

GTP form is membrane associated

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11
Q

Where is GDP usually found?

A

usually in the cytosol

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12
Q

Where is Ras found?

A

in many forms of cancer

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13
Q

How is COPII coated vesicle a paradigm for transport vesicle formation?

A

COPII components:
- GTPase - Sar1 (member of the Arf family)
- Adaptor: Sec23/24
- Coat: Sec13/31

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14
Q

What ensures proper protein folding?

A

Chaperones

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15
Q

Describe the formation of a COPII vesicle

A

Soluble cargo selected through signalling
- high surface area:volume ratio

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16
Q

What recognises the proteins?

A

The adaptor proteins

17
Q

What do coat proteins provide?

A

A structural scaffold

18
Q

What type of experiment allows us to study COPII?

A

Reconstitution experiments allow us to understand what makes a COPII vesicle.

  • centrifugation separates the different parts
19
Q

What does the ER membrane contain?

A

Ribophorin

20
Q

What do COPII vesicles contain?

A

p58 (cargo protein)

21
Q

What are the COPII components?

A
  • Sar1 GEF is Sec12
  • Sec23/24
  • Sec13/31
  • ATP
  • GTP
22
Q

Where are GTPases recruited from?

A

the cytosol

23
Q

What acts as a GAP for Sar1?

A

Sec23. GAP activity enhanced following recruitment of the coat Sec13/31

24
Q

Describe features of GTPases

A
  • mutant GTPases can be generated
  • GDP mutant: sequester GEFs
  • GTP mutant: cannot hydrolyse GTP
  • Cycles of GTPase activity are important
  • Mutant GTPases often have a dominant negative effect
  • Expression of Sar1GDP inhibits COPII formation
25
Q

What is transport through the secretory pathway mediated by?

A

Coated vesicles and tubules

26
Q

What is COPII used to transport?

A

Newly synthesised proteins

27
Q

What is COPI used to transport?

A

retrieved & newly synthesised proteins

28
Q

What is Clathrin (TGN) used to transport?

A

Lysosomal proteins, regulated secretory proteins

29
Q

What is Clathrin (PM) used to transport?

A

Endocytosed material

30
Q

What do adaptor proteins do?

A
  • recognise and select cargo ensuring specificity
  • link the coat to the membrane
  • adaptors recognise motifs (tags) in the cytoplasmic domains of the membrane protein

adaptor complexes also show a precise subcellular localization

31
Q

What is a tyrosine-based sorting signal in endocytic proteins?

A

TfR (Transferrin Receptor)

32
Q

What is a ubiquitin-based sorting signal in endocytic proteins?

A

EGFR (epidermal growth factor receptor)

33
Q

What does AP2 do?

A

AP2 recognises a variety of peptide motifs e.g. u & o subunits recognise sorting signals

34
Q

Explain the role of AP2 in endocytosis

A

AP2 is a major clathrin adaptor. Other adaptors allow cells to select what they internalize.

Advanced molecular & cell L2 (12 decks)

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