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MICB 308 > Phagocytosis > Flashcards

Phagocytosis Flashcards

1
Q

autophagy (2)

A
  • removal of unnecessary or dysfunctional components
  • lysosome-dependent regulated mechanism
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2
Q

endocytosis (2)

A
  • the ingestion of large particles
  • the uptake of fluids or macromolecules in small vesicles
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3
Q

pinocytosis

A
  • a type of endocytosis that involves the ingestion of large particles
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4
Q

phagocytosis

A
  • the type of endocytosis that involves the uptake of fluids or macromolecules in small vesicles
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5
Q

what facilitates phagocytosis of pathogens

A
  • complement system (C’)
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6
Q

what is the involved in the C’ facilitation of phagocytosis (2)

A
  • C’ receptors
  • receptors for antibodies
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7
Q

what are pathogens opsonized by (2)

A
  • C3b or iC3b
  • IgM/IgG
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8
Q

what are the receptors for opsonization ligands (4)

A
  • CR1
  • CR3
  • CR4
  • Fc-gamma
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9
Q

what is the ligand for CR1 (2)

A
  • C3b
  • C4b
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10
Q

what is the ligand for CR3

A
  • iC3b
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11
Q

what is the ligand for CR4

A
  • iC3b
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12
Q

what is the ligand for Fc-gamma

A
  • IgG
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13
Q

describe the interaction between the bacterium and the phagocyte during phagocytosis (2)

A
  • initial interaction is electrostatic and involves divalent cations
  • interaction is then facilitated by opsonins
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14
Q

phagocytosis: what does uptake involve (2)

A
  • microfilament rearrangements
  • formation of a phagosome membrane
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15
Q

what does the act of phagocytosis result in

A
  • activation of the respiratory/oxidative burst
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16
Q

what does the respiratory/oxidative burst involve (2)

A
  • NADPH oxidase host cell enzyme
  • electron transport chain
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17
Q

NADPH oxidase role (2)

A
  • enzyme moves from cytosol to the phagosome membrane
  • transfers electrons from NADPH in the cytosol across the vacuole membrane
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18
Q

oxygen-dependent killing (2)

A
  • transfer of electrons reduces oxygen (O2) to superoxide (O2-)
  • results in productive of reaction oxygen and nitrogen species
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19
Q

what does oxygen-dependent killing damage inside of the phagosome (3)

A
  • DNA
  • protein
  • lipids
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20
Q

reactive oxygen species (4)

A
  • superoxide
  • hydrogen peroxide
  • hypochlorite
  • hydroxyl radicals
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21
Q

reactive nitrogen species (3)

A
  • nitric oxide
  • peroxynitride
  • nitrogen dioxide
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22
Q

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

A
  • NADPH oxidase converts O2 and NADPH to O2-
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23
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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24
Q

oxygen-dependent killing: how are hydroxyl radicals created

A
  • hydrogen peroxide (H2O2) combines with superoxide (O2-) to produce hydroxyl radicals (OH)
25
Q

oxygen-dependent killing: how is hypochlorite created

A
  • myeloperoxidase converts hydrogen peroxide (H2O2) into hypochlorite (OCl-) using Cl-
26
Q

oxygen-dependent killing: how are singlet oxygens made

A
  • hypochlorite (OCl-) and hydrogen peroxide (H2O2) combine to form a single oxygen (1O2)
27
Q

oxygen-independent killing (6)

A
  • acid pH
  • lysozyme
  • cationic proteins
  • bacteriostatic molecules
  • acid hydrolases
  • fusion with lysosome
28
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
29
Q

oxygen-independent killing: lysozyme

A
  • dissolves the cell of certain Gram-positive bacteria
30
Q

oxygen-independent killing: cationic proteins

A
  • bactericidal activity/damages bacteria
31
Q

oxygen-independent killing: bacteriostatic molecules (2)

A
  • lactoferrin sequesters iron
  • vitamin B12-binding proteins sequesters B12
32
Q

oxygen-independent killing: acid hydrolases

A
  • post-mortem digestion of the microorganism
33
Q

oxygen-independent killing: fusion with lysosome (2)

A
  • activation of lysosomal enzymes
  • acid hydrolases, cationic antimicrobial peptides, and lysozyme
34
Q

oxygen-independent killing: result (2)

A
  • bacteria are killed and digested
  • damage to cell wall, cell membrane, and DNA
35
Q

vacuole (3)

A
  • space or vesicle within the cytoplasm of a cell
  • enclosed by a membrane
  • typically containing fluid
36
Q

how is oxygen-independent killing initiated (3)

A
  • drop in pH of the vacuole
  • phagosome fuses with lysosomes
  • results in activation of lysosomal enzymes
37
Q

lysosomal enzymes (3)

A
  • acid hydrolases
  • cationic antimicrobial peptides
  • lysozyme
38
Q

what cells carry out phagocytosis (4)

A
  • monocytes
  • macrophages
  • dendritic cells
  • neutrophils
39
Q

what cell is the most efficient phagocyte

A
  • neutrophils
40
Q

neutrophil characteristics (2)

A
  • kill efficiently
  • short half-life compared to monocytes/macrophages
41
Q

TB: phagocytosis normally (3)

A
  • two-step acidification
  • degradation
  • presentation of microbial peptides
42
Q

TB: phagocytosis with Mtb (4)

A
  • acidification is blocked
  • no degradation
  • no presentation of bacterial peptides
  • no lysosomal fusion
43
Q

co-localization graph: E. coli and phagocytosis

A
  • E. coli co-localizes with the lysosomes in the graph (green and red combine to form orange)
44
Q

co-localization graph: Mtb and phagocytosis

A
  • Mtb and lysosome do not co-localize (green and red do not combine to form orange)
45
Q

what is an important molecule secreted by Mtb

A
  • protein tyrosine phosphatase A (PtpA)
46
Q

protein tyrosine phosphatase A: secretion

A
  • one of two mycobacterial secreted tyrosine phosphatases in Mtb
47
Q

protein tyrosine phosphatase A (2)

A
  • essential for Mtb ability to replicate in human macrophages
  • substrate is located in the host
48
Q

PtpA and Mtb: in-vitro gene knock-out (2)

A
  • mutant was indistinguishable from its parental strain
  • highlights how PtpA is not important in-vitro
49
Q

PtpA and Mtb: in-vivo gene knock-out, competitive infection (2)

A
  • macrophage was able to clear the PtpA knockout more easily than the WT Mtb
  • suggest that PtpA is a key molecule in defending against the host immune system
50
Q

PtpA and Mtb: in-vivo gene knock-out, independent growth (2)

A
  • WT Mtb and complemented mutant showed better growth compared to PtpA mutant
  • suggest that PtpA is a key molecule in growth inside the host system
51
Q

PtpA and Mtb: in-vivo knock-out, mouse model (2)

A
  • PtpA mutants are indistinguishable from the WT and complemented Mtb
  • suggests that PtpA is only essential for Mtb replication in humans
52
Q

how was the substrate for PtpA determined (2)

A
  • construction of “trapping” mutant protein to “fish” the cognate substrate
  • mutant protein does not release the substrate
53
Q

how was the trapping mutant found when trying to determine the PtpA substrate (2)

A
  • showed a higher band on Western Blot compared to WT
  • indicates that the substrate is trapped
54
Q

what trapping PtpA mutant was used to find the host substrate (2)

A
  • D126A mutant
  • mutant in the function of protonation of the phenolic group
55
Q

what is the host substrate for PtpA (2)

A
  • human vacuolar protein sorting protein VPS33B
  • macrophage ATPase subunit H
56
Q

how does PtpA function in the host: VPS33B (2)

A
  • upon infection, PtpA binds to VPS33B
  • inhibits phagolysosome fusion
57
Q

how does PtpA function in the host: ATPase subunit H

A
  • prevents normal ATPase action of driving proton transport to reduce pH
58
Q

how does PtpA function in the host: VPS33B and ATPase

A
  • blocks recruitment of substrates to the Mtb phagosome

MICB 308 (22 decks)

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