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z:Cell 300 > Lecture 14: Bacterial and Plant Toxins > Flashcards

Lecture 14: Bacterial and Plant Toxins Flashcards

1
Q

Toxins are ___

A

soluble substances that alter the metabolism of host cells with deleterious effects on the host

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2
Q

Toxins are the ___ factor for pathogenic bacteria

A

primary virulence factor

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3
Q

Toxins often require _____ to achieve virulent form

A

re-arrangement or cleavage

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4
Q

target of toxins in host cells

A

cytoplasmic enzymes or structural proteins

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5
Q

Ricin is from ___

A

castor bean plant (seed)- plant itself is harmless

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6
Q

anthrax spores are highly-_____

A

resistant

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7
Q

how cholera works generally?

A

cholera toxin increase cAMP production in intestinal epithelial cells to increase secretion of salts and water, affecting ability to retain water causing diarrhea and dehydration

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8
Q

toxins serve as tools for cell biologists to reveal ____

A

new intracellular trafficking pathways

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9
Q

2 types of toxins

A

-pore forming toxins
-ab toxins

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10
Q

pore forming toxins create ____ of host cells

A

holes in PM

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11
Q

type of toxin: a-toxin of S.aureus (flesh eating disease)

A

pore-forming toxin

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12
Q

a-toxin of S.aureus method

A

-released by bacterium as 33 kDa protein
-monomers target PM
-forms homo-heptamer form (7 rings)
-inserts in membrane and forms channel
-damge to membrane cause ions to leak out –> swelling + death of cell

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13
Q

A-chain of ab toxin contains ____

A

catalytic domain (“toxin” part)

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14
Q

A-chain of ab toxin modifies ___

A

cytosolic enzyme

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15
Q

B-chain of ab toxin is _____

A

targeting subunit (gets A-chain into cytoplasm)

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16
Q

B-chain of ab toxin interacts with _____ and guides _____

A

cell surface receptor (protein, glycolipid or carbohydrate)
A subunit to final destination

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17
Q

Depending upon toxin, A and B chains are _____

A

separated by different mechanisms (some no cleavage, some cleavage by bacteria or host cell)

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18
Q

In all cases, A and B chains of ab toxin require ____ in ____ to separate

A

-reduction of disulfide bond
cytoplasm of host cell

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19
Q

Botulinum and tetanus toxins: A chain cleaves____

A

cleaves specific SNAREs and blocks vesicle targeting and exocytosis

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20
Q

Botulinum and tetanus toxins: A chain recognize ____

A
  • Recognize 9 aa residue motifs unique to SNAREs
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21
Q

_____recognize different SNAREs and sometimes the same SNAREs at different sites

A

Different toxins

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22
Q

Botulinum and tetanus toxins are examples of ___

A

molecular scalpels

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23
Q

Cons of Botulinum and tetanus toxins

A

-block exocytosis
-interrupts neurotransmission (muscle can’t work)

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24
Q

which type of cells have Botulinum and tetanus toxin receptors?

A

neuronal (non-neuronal cells don’t have them)

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25
Q

Pros of Botulinum and tetanus toxins

A

-inject in or near spastic muscle for relaxation
-migraine treatment

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26
Q

“A” subunits of AB Toxins enter cytoplasm via_____

A

different mechanisms

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27
Q

different ways A subunits enter cytoplasm

A

-some enter through ER
-some enter through endosomes

28
Q

A-toxin entry in cytoplasm through ER

A

-endosome->retrograde transport from golgi to ER then enter cytoplasm through Sec61 (retro translocation)

29
Q

A-toxin entry in cytoplasm through endosomes

A

-endosome
-at low ph (5-6) B chain of toxin becomes hydrophobic and penetrates endosome bilayer
-forms channel that translocate unfolded A-chain

29
Q

AB toxins that entry through endosomes

A

-cholera, pertussis

30
Q

AB toxins that entry through ER

A

-anthrax

31
Q

____toxins take advantage of retrograde
transport pathways in host cells

A

Shiga and cholera

32
Q

cons of Shiga and cholera toxins

A

blocks protein synthesis and kills cells

33
Q

pros of Shiga and cholera toxins

A

Identified novel retrograde pathway from endosomes back to ER

34
Q

Shiga and cholera toxins can be used as markers of ____

A

retrograde carriers

35
Q

2 ways to study toxin transport in host cells

A
  1. Genetically modified toxins containing acceptor
    sites for N-linked glycosylation
    2.Fluorescent toxins for live cell imaging
36
Q

Genetically modifying toxins with acceptor
sites for N-linked glycosylation tells us what?

A

-can deduce where toxin enters cytoplasm
-n-glycosylation of toxins doesn’t occur in bacterial cells

37
Q

tagging toxins with fluroresnt atges tells us what?

A

-Follow movement of fluorescent toxins (or use anti-toxin antibodies) after entering cells
-allows us to inhibit specific transport steps

38
Q

Some toxins gain access to _____ and are transferred to cytoplasm when they reach the ER

A

secretory pathway by endocytosis

39
Q

Genetically modifying toxins with acceptor
sites for N-linked glycosylation : Shiga toxin

A

it toxin reaches ER, glycosylation observed (increase in MW)

40
Q

Glycosylation of toxin can be detected
by subjecting cell lysates to _____

A

SDSPAGE and immunoblotting with antibodies to toxin.

41
Q

endosome temperature block

A

19 C

42
Q

GPP130 is a ____ protein that is important of transport of ___

A

Golgi-associated
shiga toxin

43
Q

Shiga toxin bypasses _____en route from
early endosomes to Golgi?

A

-late endosomes/lysosomes

44
Q

GPP130 is a protein that cycles between
_____

A

early endosomes and Golgi

45
Q

GP73 is a _____ protein that has _____ on toxin transport

A

Golgi
no effect

45
Q

GPP130 is needed for ____

A

movement of shiga toxin for endosome to golgi

46
Q

addition of what salt that induces degradation of GPP130

A

-Manganese (Mn)

47
Q

Manganese (Mn) induces ____ in ____

A

specific degradation of GPP130 in lysosomes

48
Q

Leupeptin blocks ____

A

lysosomal degradation of proteins

49
Q

Manganese (Mn) and shiga toxin trafficking

A

-rest toxin in endosomes

50
Q

Manganese (Mn) and cholerat oxin trafficking

A

-toxin rest in golgi complex

51
Q

Manganese (Mn) dosing

A

toxic in high doses, but at lower concentrations, can protectmice from Shiga toxin (prevents kidney damage)

52
Q

KDEL receptor brings ___

A

things back to ER

53
Q

Rab6 brings ___

A

things back to ER

54
Q

PM transport temperature block

A

4 C

55
Q

STB and Rab6 detected in ___vesicles and tubules

A

same

56
Q

STB and KDEL receptor in ___vesicles and tubules

A

different

57
Q

Looking transport of STB, KDEL receptor and Rab6 from golgi to ER can __

A

help us determine how shiga toxin gets from golgi to ER

58
Q

anti COPI antibodies inhibited movement of _____

A

KDEL-R containing vesicles

59
Q

Anti-COPI antibodies had no effect on ___

A

Rab6-containing vesicles

60
Q

expression go dominant negative form of protein will __

A

block function of wildtype protein, prevent function of protein overall

61
Q

effect of shiga toxin on protein synthesis

A

Shiga toxin blocks protein synthesis

62
Q

cells expressing Rab6-DN (dominant negative) have ___

A

More protein synthesis

63
Q

delivery of STB to ER from golgi requires ___

A

Rab6

64
Q

Toxins enter through ER because ___

A

> ER contains machinery for unfolding and dislocation of protein (A subunit needs to unfold to thread through Sec 61 in ER)

65
Q

Toxins aren’t degraded by proteasome after retro translocation through Sec61 because _____

A

degradation by proteasome needed ubiquitination of lysine residues and many toxins don’t have lysine residues

z:Cell 300 (17 decks)

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