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MICB 308 > Intracellular Survival > Flashcards

Intracellular Survival Flashcards

1
Q

phagocytosis: what is involved in uptake (2)

A
  • microfilament rearrangements
  • lead to formation of a phagosome membrane
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2
Q

what does phagocytosis activate

A
  • activation of respiratory/oxidative burst
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3
Q

what host cell enzyme aids in the respiratory/oxidative burst

A
  • NADPH oxidase
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4
Q

respiratory/oxidative burst: NADPH oxidase (3)

A
  • an electron transport chain
  • moves from cytosol to the phagosome membrane
  • transfers electrons from NADPH in the cytosol across the vacuole membrane
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5
Q

oxygen-dependent killing (3)

A
  • transfer of electrons reduces oxygen (O2) to superoxide (O2-)
  • results in productive of reaction oxygen and nitrogen species
  • causes damage to DNA, protein, and lipids inside the phagosome
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6
Q

reactive oxygen species (4)

A
  • superoxide
  • hydrogen peroxide
  • hypochlorite
  • hydroxyl radicals
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7
Q

reactive nitrogen species (3)

A
  • nitric oxide
  • peroxynitride
  • nitrogen dioxide
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8
Q

oxygen-dependent killing: how is superoxide (O2-) produced

A
  • NADPH oxidase converts O2 and NADPH to O2-
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9
Q

oxygen-dependent killing: how is hydrogen peroxide produced

A
  • superoxide dismutase converts superoxide (O2-) to hydrogen peroxide (H2O2) using protons (H+)
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10
Q

oxygen-dependent killing: how are hydroxyl radicals created

A
  • hydrogen peroxide (H2O2) combines with superoxide (O2-) to produce hydroxyl radicals (OH)
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11
Q

oxygen-dependent killing: how is hypochlorite created

A
  • myeloperoxidase converts hydrogen peroxide (H2O2) into hypochlorite (OCl-) using Cl-
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12
Q

oxygen-dependent killing: how are singlet oxygens made

A
  • hypochlorite (OCl-) and hydrogen peroxide (H2O2) combine to form a single oxygen (1O2)
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13
Q

oxygen-independent killing (6)

A
  • acid pH
  • lysozyme
  • cationic proteins
  • bacteriostatic molecules
  • acid hydrolases
  • fusion with lysosome
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14
Q

oxygen-independent killing: acid pH (2)

A
  • vacuolar ATPase pumps H+ into the phagosome to create a acid pH environment
  • affect the bacterial surface
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15
Q

oxygen-independent killing: lysozyme

A
  • dissolves the cell of certain Gram-positive bacteria
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16
Q

oxygen-independent killing: cationic proteins

A
  • bactericidal activity/damages bacteria
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17
Q

oxygen-independent killing: bacteriostatic molecules (2)

A
  • lactoferrin sequesters iron
  • vitamin B12-binding proteins sequesters B12
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18
Q

oxygen-independent killing: acid hydrolases

A
  • post-mortem digestion of the microorganism
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19
Q

oxygen-independent killing: fusion with lysosome (2)

A
  • activation of lysosomal enzymes
  • acid hydrolases, cationic antimicrobial peptides, and lysozyme
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20
Q

oxygen-independent killing: result (2)

A
  • bacteria are killed and digested
  • damage to cell wall, cell membrane, and DNA
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21
Q

normal endocytic events (4)

A
  • early endosome
  • late endosome
  • fusion with lysosome to create the phagolysosome
  • destruction of the bacteria
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22
Q

Rabs

A
  • small GTPases
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23
Q

Rab5

A
  • early endosome marker
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24
Q

Rab7

A
  • late endosome marker
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25
Q

LAMP1 (2)

A
  • lysosomal associated membrane protein
  • phagolysosome fusion marker
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26
Q

what tools can we use to see where the phagosome is located in the pathway (3)

A
  • western blot
  • IH
  • IF
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27
Q

bacterial phagosome survival mechanisms (4)

A
  • failure to trigger oxidative burst by inhibiting phagosome acidification
  • inhibit/stall the fusion of the phagosome with the lysosome
  • survival within the phagolysosome
  • escape from the phagosome
28
Q

legionella pneumophila
- resulting illness
- spread
- demographic
- symptoms
- intracellular survival

A
  • causes Legionnaire’s Disease
  • spread by water droplets/aerosols
  • usually found in elderly or smokers
  • cough, pneumonia, high fevers
  • survives and grows in macrophages
29
Q

how does legionella pneumophila survive in macrophages; basic steps (6)

A
  • legionella pneumophila are taken up into a phagosome
  • phagosome does not become acidified or fuse with the lysosome (fusion may be delayed)
  • instead, phagosome is surrounded by ER studded with ribosomes
  • bacteria multiple in the phagosome
  • the phagosome ruptures, releasing the bacteria into the cytoplasm to further replicate
  • the bacterial lyse the host cell and escape
30
Q

how does legionella pneumophila release effectors into the host cyotsol

A
  • it delivers 280 proteins to the cytosol using the Dot system, a T4SS
31
Q

what is the name of the phagosome that Legionella is found in

A
  • Legionella containing vacuole (LCV)
32
Q

how does Legionella achieve early diversion of the endocytic pathway (3)

A
  • LCV membrane resembles the ER
  • reminiscent of an autophagous vacuole (autophagy)
  • does not contain Rab5 or Rab7 markers, and LAMP1 marker is delayed
33
Q

autophagy (2)

A
  • induced when cell undergoes starvation
  • mechanism for recycling proteins
34
Q

how does Legionella pneumophila stall phagosome maturation for several hours (3)

A
  • LCV has Rab1-GTP on membrane, a protein associated with autophagosomes
  • Legionella proteins LidA and DrrA ensure that Rab1 remains in GTP-bound state
  • results in delay of phagosome maturation and delayed fusion with lysosome
35
Q

what occurs while Legionella delays the phagosome maturation (2)

A
  • legionella pneumophila undergoes a developmental cycle
  • transformed bacterium is able to survive within the phagolysosome environment
36
Q

how does Legionella continue the phagosome maturation and allow for lysosomal fusion (3)

A
  • Legionella secretes LepB protein
  • LepB allows for conversion of Rab1-GTP to Rab1-GDP
  • LCV is now able to fuse with lysosomes and LAMP1 appears on the LCV membrane
37
Q

chlamydia
- type of pathogen
- varieties (3)

A
  • obligate intracellular pathogens
  • C. trachomatis
  • C. pneumonia
  • C. psittaci
38
Q

Chlamydia trachomatis (4)
- disease type
- early symptoms
- acute symptoms
- long-term symptoms

A
  • sexually transmitted disease
  • early stages are mild with few symptoms
  • painful urination, discharge from vagina/penis
  • can lead to pelvic inflammatory disease, infertility, and blindness
39
Q

Chlamydia pneumonia (2)
- symptoms
- linked to

A
  • causes pneumonia
  • linked to atherosclerosis
40
Q

Chlamydia psittaci

A
  • causes psittacosis in birds
41
Q

what is the name for the phagosome that contains Chlamydia

A
  • Inclusion
42
Q

how does Chlamydia generally survive inside the Inclusion (2)

A
  • it has a bi-phasic developmental cycle
  • cycle takes place entirely within the Inclusion
43
Q

bi-phasic developmental cycle of Chlamydia (2)

A
  • elementary body (EB): environmentally stable form that can infect cells
  • reticulate body (RB): intracellular replicative form
44
Q

life cycle of Chlamydia (5)

A
  • 0-2 hours: internalized EBs fuse to form an Inclusion
  • 2-6 hours: EBs differentiate into RBs
  • 12-24 hours: RBs replicate by binary fission and peak in numbers as the Inclusion matures; RB juxtaposed to Inclusion membrane
  • 24-40 hours: RBs differentiate back to EBs
  • 48-72 hours: lysis/release occurs and EBs exit
45
Q

Chlamydia: aberrant body (2)

A
  • RBs may transition into aberrant bodies during stress and remain dormant
  • aberrant bodies are reactivated in RBs when stress is reduced and continue through cycle
46
Q

how does Chlamydia release effectors into the host cytoplasm

A
  • releases multiple effectors using a T3SS
47
Q

Chlamydia: dynein-dynactin complex

A
  • causes trafficking of Inclusion toward ER
48
Q

Chlamydia Inclusion properties (4)

A
  • no Rab5 or Rab7 markers on the membrane
  • Rab4, Rab11, Rab1 markers found on secretory vesicles
  • found in peri-Golgi area of the cell
  • Chlamydia fuses Inclusion with vesicles in secretory pathway and stalls/delays secretion until cell lyses
49
Q

Chlamydia: Inc

A
  • bacterial Inclusion protein that prevents fusion with lysosomes and promotes interactions with recycling endosomes for iron acquisition
50
Q

Listeria monocytogenes and Shigella flexneri: escape from phagosome

A
  • although Listeria is gram positive and Shigella is gram negative, they have the same mechanism for survival/escape from phagosomes
51
Q

Listeria monocytogenes
- bacteria type
- growth and location
- type of illness
- symptoms (2)

A
  • gram positive, non-spore former
  • grows well at 4C (fridge) and is often found in unpasteurized milk and milk products
  • food-borne illness
  • causes flu-like symptoms in healthy individuals
  • can be fatal for fetus, newborns, immunocompromised individuals, elderly, and pregnant women
52
Q

Listeria monocytogenes: host cells (2)

A
  • infects a variety of cells
  • monocytes, macrophages, epithelial cells, etc
53
Q

how does Listeria monocytogenes invade cells (2)

A
  • invades via InlA/InlB using zipper-mediated uptake
  • following uptake, it is found in an early endosome
54
Q

how does Listeria monocytogenes escape the phagosome (2)

A
  • endosome containing Listeria becomes more acidic
  • at low pH, Listeria toxin Listeriolysin O (LLO) and phospholipase C gets activated and lyses the phagosome membrane
55
Q

how does Listeria monocytogenes escape the host cell after phagosome escape (2)

A
  • actin tails form at one end of the bacterium in the cytosol
  • serve to propel bacteria throughout the cytosol and to adjacent cells
56
Q

what is the process of Listeria monocytogenes escaping the host cell called and what is it mediated by (2)

A
  • actin nucleation
  • protein ActA
57
Q

ActA (4)

A
  • nucleates actin polymerization
  • asymmetry (only expressed at one pole)
  • initiates movement
  • increased velocity due to recruitment of host proteins profilin and VASP
58
Q

what occurs after Listeria is propelled into adjacent cells (3)

A
  • formation of phagosome with a double membrane in adjacent cells (one from original cell and one from adjacent host cell)
  • double membrane is lysed by Listeria Proteins called Phospholipases (PlcA, PlcB, PlcC) and LLO
  • cycle continues
59
Q

phagosome escape: Shigella flexneri

A
  • Shigella employs the same strategy as Listeria, but uses different proteins for phagosome escape
60
Q

Listeria proteins: Bacteria taken up in vacuole in host cell (2)

A
  • InlA
  • InlB
61
Q

Shigella proteins: Bacteria taken up in vacuole in host cell (2)

A
  • IpaB
  • IpaC
62
Q

Listeria proteins: Vacuole is lysed; bacterium escapes into cytosol and replicates (3)

A
  • LLO
  • PlcA
  • PlcC
63
Q

Shigella proteins: Vacuole is lysed; bacterium escapes into cytosol and replicates (2)

A
  • IpaB
  • IpaC
64
Q

Listeria proteins: Actin tail formation; intracellular movement; cell to cell spread

A
  • ActA
65
Q

Shigella proteins: Actin tail formation; intracellular movement; cell to cell spread

A
  • IcsA
66
Q

Listeria proteins: Lysis of double membrane vacuole in new host cell (3)

A
  • LLO
  • PlcA
  • PlcB
67
Q

Shigella proteins: Lysis of double membrane vacuole in new host cell

A
  • IcsB

MICB 308 (22 decks)

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