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BMS > Vessicle trafficking: Endo and Exocytosis > Flashcards

Vessicle trafficking: Endo and Exocytosis Flashcards

1
Q

The transfer of proteins is post-translationally mediated by specific signal sequences for all organelles except

A

ER

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2
Q

Protein transfer to all organelles except ER is post-translational and follows synthesis on

A

Free ribosomes

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3
Q

Protein transfer to all organelles except ER is post-translational and follows synthesis on free ribosomes and is mediated by organelle-specific

A

“signal” amino acid sequences

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4
Q

Unique amino acid sequences target proteins to different

A

Organelles

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5
Q

Proteins enter and leave the nucleus through

-mRNA also exits the nucleus through these structure

A

Nuclear pores

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6
Q

Made up of an outer octagonal ring of protein and an inner central pore

A

Nuclear pores

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7
Q

The nuclear pore is comprised of about

A

30 proteins

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8
Q

The nuclear pore mediates traffic in and out of the

A

Nucleus

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9
Q

Small molecules can diffuse through nuclear pores, but a transport system is needed for

A

Larger molecules

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10
Q

Nuclear protein “signal sequence” is recognized in the cytoplsm by

A

Importins

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11
Q

Proteins bound to importins are transferred through the nuclear pore and are then released from importins in the nucleus after binding to

A

RanGTP

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12
Q

Induces the dissociation of the cargo protein by binding to the β subunit of importin

A

RanGTP

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13
Q

To export from the nucleus, RanGTP induces binding of a cargo protein to

-transports protein to cytoplasm

A

Exportin

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14
Q

The RanGTP/importin β complex is transported back to the cytoplasm, where RanGTP is converted to RanGDP by

A

RanGTPase activating protein (RanGAP)

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15
Q

The RanGTP/importin β complex is transported back to the cytoplasm, where RanGTP is converted to RanGDP by RanGTPase activating protein (RanGAP), resulting in the release of

A

Importin β

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16
Q

Used at many steps in intracellular trafficking

A

Monomeric GTP binding proteins

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17
Q

The monomeric GTP binding proteins used at many steps in intracellular trafficking are inactive in their

A

GDP forms

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18
Q

GTP binding proteins are involved in multiple aspects of cell trafficking including

A
  1. ) release of nuclear proteins (Ran)
  2. ) Transport vesicle formation (Arf, Sar-1)
  3. ) Transport vesicle recognition (Rab)
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19
Q

Post-translational transport to peroxisomes uses an amino acid “signal” sequence” and is abolished in

A

Zellweger syndrome

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20
Q

Proteins for peroxisomes are synthesized by free cytosolic ribosomes and then transported into

-abundant in the liver

A

Peroxisomes

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21
Q

Phospholipids and membrane proteins are also transported to peroxisomes by the

A

ER

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22
Q

The major protein of the peroxisome

-decomposes hydrogen peroxide into water

A

Catalase

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23
Q

A tetramer of apocatalase molecules assembled within the peroxisome

A

Catalase

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24
Q

Added to each monomer to prevent it from moving back into the cytosol across the peroxisomal membrane

A

Heme

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25
Q

A lethal condition caused by the defective assembly of peroxisomes due to the lack of transport of enzyme proteins (but not membrane proteins) into the peroxisome

A

Zellweger syndrome

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26
Q

Cells in patients with Zellweger syndrome contain empty

A

Peroxisomes

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27
Q

Transfer from the ER to the golgi occurs

A

Co-translationally

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28
Q

Makes up 50% of the total cell membrane

A

ER

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29
Q

Associate with mRNA for secretory pathway proteins and begin translation in cytoplasm

A

Cytoplasmic ribosomes

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30
Q

While being synthesized on cytoplasmic ribosomes, the N-terminus of secretory pathway proteins binds the

A

Signal Recognition Particle (SRP)

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31
Q

There are three major steps during SRP-mediated protein translocation across the ER. The first step is that the binding of SRP to signal peptide causes a

A

Pause in translation

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32
Q

There are three major steps during SRP-mediated protein translocation across the ER. The second step is that the SRP bound ribosome attatches to the

A

SRP receptor in ER membrane

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33
Q

There are three major steps during SRP-mediated protein translocation across the ER. The third step is the dissociation of the

A

SRP and SRP receptor

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34
Q

What are some of the protein processing steps that begin during translocation through the ER?

A
  1. ) signal peptide is removed
  2. ) hydroxylation
  3. ) disulfide bond formation
  4. ) chaperone interaction
  5. ) glycosylation
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35
Q

No proteins are exported from the ER unless they are

A

Properly folded

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36
Q

A critical processing element for the protein to be able to exit the ER

A

Glycosylation

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37
Q

A pre-formed oligosaccharide with 9 mannoses is added to the protein co-translationally from membrane lipid donor to

A

Specific residues (usually Asn)

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38
Q

The oligosaccharide is then modified by

A

Compartment-specific enzymes

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39
Q

We can deduce how far a protein has progressed in its synthesis by the extend of its

A

Modifications

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40
Q

The ability to trace sugar processing through cell compartments was critical in showing that transport through these compartments post-ER was via

A

Vesicles

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41
Q

Used for transport in both biosynthetic/secretory and endocytic pathways

42
Q

What are the three generic steps for vesicle transport?

A
  1. ) Form vesicle
  2. ) Select cargo
  3. ) Have address
43
Q

What is the main advantage to vesicular transport?

A

Transporting cargo without crossing membranes

44
Q

Vesicles in vesicular transport fuse with the membrane of the organelle is is delivering cargo to. Thus, there is no need for

A

Membrane crossing

45
Q

To form the vesicle, you need protein “coats” which deform the

46
Q

The modifications and glycosylation of the protein will enable the vesicle to

A

Select its cargo

47
Q

Allow vesicles to identify specific targets

48
Q

Coat proteins, cargo to be transported, and address molecules all need to be assembled during

A

Vesicle formation

49
Q

Vesicle cargo is recruited by binding specific receptors that recognize specific signals on the

A

Cargo proteins

50
Q

What are the three different protein coats that are used to deform the membrane during vesicle formation?

A
  1. ) Clathrin
  2. ) Coatamer (COP) I
  3. ) Coatamer (COP) II
51
Q

The formation of clathrin-coated vesicles (used at several transport steps) looks like direct binding between clathrin and the plasma mebrane, but is it actually?

52
Q

Regulated by monomeric GTP binding proteins that cycle between active and inactive states

A

Assembly of COP-I and COP-II coats

53
Q

What are the GTP proteins involved in the first steps of vesicle formation for

  1. ) COP-I
  2. ) COP-II
A
  1. ) ARF

2. ) Sar-1

54
Q

The formation of the multi-subunit coatamer coated vesicles is initiated by binding to the donor membrane of a GTP binding protein that has become embedded in the

A

Plasma membrane

55
Q

When GTP is bound, the lipid tail of Sar-1 is exposed. Sar-1 then insertes its tail into the

A

Plasma membrane

56
Q

What happens once Sar-1 has used its tail to attach to the plasma membrane?

A

COP-II subunits bind the membrane

57
Q

Specific cargo receptors can then bind to these

A

COP-II subunits

58
Q

Used for transport from the ER to the cis-Golgi

59
Q

Used for retrograde transport, i.e. from trans-golgi to cis-golgi or from cis-golgi to ER

60
Q

Used fro transport from the cell surface to the early endosome, from the trans-golgi network to the late endosome, and from the late endosome to the trans golgi network

61
Q

Mediate vesicle-target recognition and fusion

A

v- and t-SNAREs

62
Q

Function as a lock and key. If there is a correct fit, they will form a coiled coil until the membranes fuse

A

v- and t-SNAREs

63
Q

Located on vesicles

A

v-SNAREs (vesicle SNAREs)

64
Q

Located on target compartments and bind v-SNAREs

A

t-SNAREs (target SNAREs)

65
Q

Can also function in vesicle targeting by binding “effectors” when GTP is bound

A

Rab proteins

66
Q

Cleave SNAREs and prevent vesicle fusion and neurotransmitter release

A

Botulinum and Tetanus Toxins

67
Q

Predicted that different complementary vesicle (v-) and target (t-) SNARE membrane proteins are used for recognition in different transport steps

A

SNARE hypothesis

68
Q

The process of cutting the budding vesicle from the membrane

69
Q

Once scission has occurred, there is an uncoating event that exposes the

70
Q

Before the vesicle is close enough for the v- and t-SNAREs to interact, there is a tethering even, whereby the vesicle is tethered to the new membrane, a process that likely involves

71
Q

What are the 7 steps of the formation and fusion of vesicles?

A
  1. ) Initiation
  2. ) Budding
  3. ) Scission
  4. ) Uncoating
  5. ) Tethering
  6. ) Docking
  7. ) Fusion
72
Q

If transport from the ER to the golgi is mis-routed, then there is retrieval of the vesicle by COP-I via

A

KDEL sequence on escaped proteins

73
Q

Sugar modifications that began in the ER continue in the Golgi by way of

A

Cisternal-specific Enzymes

74
Q

The sorting of proteins to lysosomes, cell membrane,and secretory vesicles occurs in the

A

Trans Golgi Network (TGN)

75
Q

Marked by the addition of phosphate to a mannose sugar residue

A

Lysosomal proteins

76
Q

This modification is recognized by specific M-6-P receptors in the

A

Trans Golgi Network

77
Q

Once the TGN recognizes that proteins are marked for the lysosome, the proteins are packaged into clathrin vesicles and delivered to the

A

Late endosome

78
Q

The acidic pH of the lysosome then causes the ligand and receptor to

A

Dissociate

79
Q

In which disease does M-6-P modification of mannose on lysosomal proteins not occur because the phosphotransferase required is mutated?

A

Human I-cell disease

80
Q

In human I-cell disease, what happens to all of the proteins that were supposed to be lysosomal proteins?

A

They are secreted w/ secretory proteins

81
Q

Enter constitutive or regulatory secretory pathways

A

Secretory proteins

82
Q

The default secretory pathway with no sorting information

A

Constitutive secretory pathway

83
Q

Proteins are greatly concentrated during

84
Q

During transport, prohormones are

85
Q

Entry into the cell occurs via

A

Phagocytosis and endocytosis

86
Q

The phagosome hijacks host vesicles and becomes like the RER in

-blocks delivery to lysosome and can replicate

A

Legionairre’s disease

87
Q

Acts as a sorting station

A

Early endosome

88
Q

What are two types of cells that perform phagocytosis?

A

Neutrophils and macrophages

89
Q

Can be followed by recycling of receptor, receptor

degradation in lysosome, or transcytosis to bypass tight junctions following sorting in the early endosome

A

Endocytosis

90
Q

The process where vesicles are sent from the early endosome to the cell membrane for incorporation

-Used to deliver antibodies to neonates

A

Transcytosis

91
Q

Following internalization, surface receptors an cargo are sorted in the

A

Early endosome

92
Q

The late endosome matures into the

93
Q

Carries cholesterol through circulation as a lipoprotein complex

94
Q

Cytoplasmic proteins that bind both clathrin and receptors for vesicle cargo as clathrin vesicles form

95
Q

A mutation in the receptor tail can interfere with receptor binding to

96
Q

Cargo bound to its receptor will not be incorporated into vesicles unless the receptor tail is bound to

97
Q

Mutation in the LDL receptor tail can prevent cholesterol clearance, which can lead to

A

Hypercholesterolemia

98
Q

Utilize endocytic and biosynthetic pathways for propogation

A

Enveloped viruses

99
Q

The envelop fuses to the endosome at

100
Q

Occurs when receptors are delivered to the lysosome to be degraded instead of being recycled

-Ex: EGF receptor

A

Receptor Down Regultion

BMS (62 decks)

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