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MICB 308 > Intracellular Survival > Flashcards

Intracellular Survival Flashcards

(67 cards)

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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
LAMP1 (2)
- lysosomal associated membrane protein - phagolysosome fusion marker
26
what tools can we use to see where the phagosome is located in the pathway (3)
- western blot - IH - IF
27
bacterial phagosome survival mechanisms (4)
- 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
legionella pneumophila - resulting illness - spread - demographic - symptoms - intracellular survival
- 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
how does legionella pneumophila survive in macrophages; basic steps (6)
- 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
how does legionella pneumophila release effectors into the host cyotsol
- it delivers 280 proteins to the cytosol using the Dot system, a T4SS
31
what is the name of the phagosome that Legionella is found in
- Legionella containing vacuole (LCV)
32
how does Legionella achieve early diversion of the endocytic pathway (3)
- LCV membrane resembles the ER - reminiscent of an autophagous vacuole (autophagy) - does not contain Rab5 or Rab7 markers, and LAMP1 marker is delayed
33
autophagy (2)
- induced when cell undergoes starvation - mechanism for recycling proteins
34
how does Legionella pneumophila stall phagosome maturation for several hours (3)
- 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
what occurs while Legionella delays the phagosome maturation (2)
- legionella pneumophila undergoes a developmental cycle - transformed bacterium is able to survive within the phagolysosome environment
36
how does Legionella continue the phagosome maturation and allow for lysosomal fusion (3)
- 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
chlamydia - type of pathogen - varieties (3)
- obligate intracellular pathogens - C. trachomatis - C. pneumonia - C. psittaci
38
Chlamydia trachomatis (4) - disease type - early symptoms - acute symptoms - long-term symptoms
- 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
Chlamydia pneumonia (2) - symptoms - linked to
- causes pneumonia - linked to atherosclerosis
40
Chlamydia psittaci
- causes psittacosis in birds
41
what is the name for the phagosome that contains Chlamydia
- Inclusion
42
how does Chlamydia generally survive inside the Inclusion (2)
- it has a bi-phasic developmental cycle - cycle takes place entirely within the Inclusion
43
bi-phasic developmental cycle of Chlamydia (2)
- elementary body (EB): environmentally stable form that can infect cells - reticulate body (RB): intracellular replicative form
44
life cycle of Chlamydia (5)
- 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
Chlamydia: aberrant body (2)
- 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
how does Chlamydia release effectors into the host cytoplasm
- releases multiple effectors using a T3SS
47
Chlamydia: dynein-dynactin complex
- causes trafficking of Inclusion toward ER
48
Chlamydia Inclusion properties (4)
- 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
Chlamydia: Inc
- bacterial Inclusion protein that prevents fusion with lysosomes and promotes interactions with recycling endosomes for iron acquisition
50
Listeria monocytogenes and Shigella flexneri: escape from phagosome
- although Listeria is gram positive and Shigella is gram negative, they have the same mechanism for survival/escape from phagosomes
51
Listeria monocytogenes - bacteria type - growth and location - type of illness - symptoms (2)
- 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
Listeria monocytogenes: host cells (2)
- infects a variety of cells - monocytes, macrophages, epithelial cells, etc
53
how does Listeria monocytogenes invade cells (2)
- invades via InlA/InlB using zipper-mediated uptake - following uptake, it is found in an early endosome
54
how does Listeria monocytogenes escape the phagosome (2)
- 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
how does Listeria monocytogenes escape the host cell after phagosome escape (2)
- actin tails form at one end of the bacterium in the cytosol - serve to propel bacteria throughout the cytosol and to adjacent cells
56
what is the process of Listeria monocytogenes escaping the host cell called and what is it mediated by (2)
- actin nucleation - protein ActA
57
ActA (4)
- nucleates actin polymerization - asymmetry (only expressed at one pole) - initiates movement - increased velocity due to recruitment of host proteins profilin and VASP
58
what occurs after Listeria is propelled into adjacent cells (3)
- 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
phagosome escape: Shigella flexneri
- Shigella employs the same strategy as Listeria, but uses different proteins for phagosome escape
60
Listeria proteins: Bacteria taken up in vacuole in host cell (2)
- InlA - InlB
61
Shigella proteins: Bacteria taken up in vacuole in host cell (2)
- IpaB - IpaC
62
Listeria proteins: Vacuole is lysed; bacterium escapes into cytosol and replicates (3)
- LLO - PlcA - PlcC
63
Shigella proteins: Vacuole is lysed; bacterium escapes into cytosol and replicates (2)
- IpaB - IpaC
64
Listeria proteins: Actin tail formation; intracellular movement; cell to cell spread
- ActA
65
Shigella proteins: Actin tail formation; intracellular movement; cell to cell spread
- IcsA
66
Listeria proteins: Lysis of double membrane vacuole in new host cell (3)
- LLO - PlcA - PlcB
67
Shigella proteins: Lysis of double membrane vacuole in new host cell
- IcsB

MICB 308 (22 decks)

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