Pathogens II

Question 1

How viruses enter cells - integral membrane proteins

Answer 1

Integral membrane proteins in envelopes of the enveloped viruses drive fusion with pm of target cells

Question 2

How viruses enter cells - In some cases

Answer 2

The fusion with pm of target cells = involves immediate fusion with cell surface (hiv, measles)

Question 3

How viruses enter cells - Common way of fusion

Answer 3

For enveloped viruses to only fuse with pm after exposure to low ph in endosomes - usually early endosomes

Question 4

How viruses enter cells -Non enveloped viruses

Answer 4

Must usually disrupt endosome membrane to get their nucleic acid into the cytoplasm

Question 5

How viruses enter cells - Enveloped ex image

Answer 5

HIV - aids = fusion with membrane

Question 6

How viruses enter cells - Non evenloped ex image

Answer 6

Endocytosis
Inject nucleic acid directly or by break open lysosome

Question 7

Name picornaviruses

Answer 7

Poliovirus
Rhino virus - do not replicate well at 37 degrees
Norovirus

Question 8

Describe picornaviruses - ex

Answer 8

Endocytosis
Proteolytic processing
Genome replication - replication organelle
Virus particles assemble n cytoplasm
Then lytic release = get into cytoplasm

Question 9

What happens when picornaviruses in endosome

Answer 9

Once in endosome = exposed to low ph
= inject rna genome into cytoplasm

Question 10

picornaviruses = after endosome, describe their genome

Answer 10

Genome can function directly as a messenger rna, leading to synthesis of first virtual proteins including rna directed rna polymerase

Question 11

picornaviruses = descrive what they do - after in endosome specifically

Answer 11

Rna genome threaded through wall of endosome and goes into cytoplasm
—> pore formation, genome release - virtual replciation

Question 12

Describe replication organelle - picornaviruses

Answer 12

Arise from er membranes
Also - especially for poliovirus = virus modifies ribosome so it will recognize viral rna more = so cell with produce more viral rnas = boost virus replciation

Question 13

What is propose of replciation organelle - picornaviruses

Answer 13

Replication in secluded area helps virus avoid detection by host cells
Prevent autophagy/apoptosis and antiviral measures

Question 14

Describe picornaviruses - ps vesicles

Answer 14

Phosphotidyl serine rich surrounds autophagsome (maybe, looks like autophagosome but not sure)
Then fuse with cell surface
—> endocytosis by next cell = get many viral rna genomes = speeds up infection process

Question 15

picornaviruses- late endosome

Answer 15

Can sometimes fuse with pm then release internal vesicles = exosomes

Question 16

picornavirus life cycle = binds

Answer 16

Virus binds receptor on cell surface and is endocytosed

Question 17

picornavirus life cycle = after endocytosis

Answer 17

= exposed to low endosomal ph
Viral rna is threaded through a pore made in endosomal membrane by a viral protein (vp4)

Question 18

picornavirus life cycle = rna

Answer 18

The rna fed through pore = binds ribosomes and is translated, producing viral proteins, including rna directed rna poly

Question 19

picornavirus life cycle = once viral replciation

Answer 19

Once viral rep begins = viral replciation organelles created that are associated with er membranes - modify er membranes
= viral particles - assembled in cytoplasm, do not actually have membrane

Question 20

picornavirus life cycle = ribosomes

Answer 20

Modificed so that they preferentially translate viral mRNA
Most translation of cellular proteins stops - eventually leads to death host cell

Question 21

picornavirus life cycle = viral structure proteins

Answer 21

Vp1, vp2, vp3 (viral protein) associate with viral rna in cytoplasm to form virus particles
Particles can be released when cell dies

Question 22

picornavirus life cycle = process

Answer 22

Process where multiple virus particles are enclosed in a phosphoserine rich membrane

Question 23

picornavirus life cycle = phosphoserine rich membrane

Answer 23

Phosphoserine rich membrane is itself enclosed in an autophagosome like structure, which fused with pm
Releasing phosphoserine rich vesicle while infected cell still alive
Vesicles can be endocytosed by adjacent cell = resulting in its infection
(Recall = non envelope virus)

Question 24

Describe how sars cov 2 can enter cells - Gen

Answer 24

SARS cov 2 can enter plasma cells directly at pm (at cell surface, binds ace2r) or by fusion with endosomal membrane depending on variant!!!

Question 25

Describe how sars cov 2 can enter cells - specifically fusion of membranes

Answer 25

Spike protein undergoes conformational change = exposes hydrophobic areas =destabilize area they are bound to = leads to membrane fusion Also have rna that is directly recognizable that has ribosome binding sites = can get everything going

Question 26

Describe how sars cov 2 can enter cells - spike protein

Answer 26

Spike protein on a virus particle binds to ace2 receptor at cell surface

Question 27

Describe how sars cov 2 can enter cells - conformational Change

Answer 27

Conformational change in spike protein = causes virus envelope to fuse with cells membrane Depends on variation =virus may fuse directly at cell surface (delta) or be endocytosed and fuse with endosomal membrane (omicron, for most variants)

Question 28

Describe how sars cov 2 can enter cells - fusion results

Answer 28

Fusion results in entry of entire nucelocapsid including viral rna into cytoplasm Genome of sars cov 2 virus can bind directly to a ribosome and be translated

Question 29

How does hiv enter cell - enveloped vrisues

Answer 29

The env protein complex of hiv binds cd4 protein on surface of T cells And virus fuses directly with pm

Question 30

How does infleunza enter cell - enveloped vrisues

Answer 30

Ha protein of influenza virus binds to sialic acids on N-glycosylations of cell surface proteins Virus then endocytsoed and a ph induced (low ph) conformational change in HA leads to fusion with endosomal membrane

Question 31

Describe SARS cov 2 virus factories

Answer 31

Produces proteins that insert into er membrane and modify them Integral membrane protein nsp6 = forms highly tabulated er membranes = dsdna hides in crevices = cell unlikely to detect it until too late

Question 32

What does sars cov 2 do to er membranes

Answer 32

Recognizes er membranes to Shield viral rna during replication = internal shielded space where viral dna replicates multiple genomes - starts to produce viral structure protein - introduced into er with translocation apparatus - early infection - go to golgi/internal membranes

Question 33

Describe ex of enveloped virus budding - integral membrane proteins

Answer 33

Integral membrane proteins found in virus envelope must use secretory pathway to reach destination where virus budding occurs - usually (but not always) cell surface (ex - semliki forest virus)

Question 34

Describe ex of enveloped virus budding - process

Answer 34

Capsid binds to e1e2 = protein at cell surface Envelope proteins - synthesized in er —> golgi —> cell surface, reg secretory pathway

Question 35

Describe ex of enveloped virus budding - image

Answer 35

Nucelocapsid induced assembly of evenlope proteins - upon signal Then budding = can see in em

Question 36

Budding of many enveloped viruses is very simple - nucleocapsid

Answer 36

Nucelocapsid composed of proteins associated with viral nucleic acids (rna/dna depending on virus) = assembles in cytoplasm

Question 37

Budding of many enveloped viruses is very simple - meanwhile

Answer 37

One or more viral integral membrane envelope proteins synthesized and translocated to er - then traverse secretory Pathway normally and reach cell surface

Question 38

Budding of many enveloped viruses is very simple - viral nucleocapsid

Answer 38

Binds to cytoplasmic domains of envelope proteins at cell surface - this interaction leads to budding

Question 39

Is sars cov 2 a simple one

Answer 39

NAHHHH

Question 40

Ex enveloped virus = sars cov 2 = gen

Answer 40

VIRAL envelope proteins found in Vtcs Then viral nucleocapsid bind and viral particles bind into vtcs

Question 41

Ex enveloped virus = sars cov 2 = theory 1

Answer 41

NOT SUPER CLEAR Can find protein in golgi —> but after certain time in infection = do not have Golgi - cannot recognize morphologically = so cannot track

Question 42

Ex enveloped virus = sars cov 2 = theory 2

Answer 42

Maybe = SARS cov 2 = reported to bud into lysosomes, lysosomal ph = also modified to be less acid - so that lysosomal enzymes inactive, ion channel encoded by virus maybe be responsible for deacidifying endosomes (e protein) Means that envelop proteins of sars cov 2 (spike and 3 smaller proteins) must be targeted to enodosome/lysosome system Not worked how these proteins targeted here

Question 43

Ex enveloped virus = sars cov 2 = theory 2 E protein specifically

Answer 43

Ion change Accumulates in lysosomal membrane and renders it neutral = so lysosome neutral ph = harmless to virus Then fuses with pm and releases vrisues out

Question 44

How does sars cov 2 bud

Answer 44

Buds into multiple intracellualr membranes - including Ergic and vtcs

Question 45

Describe sars cov 2 Virus particles

Answer 45

Virus particles may traverse Golgi - however = what happens in cell not clear And Golgi highly disrupted during infection

Question 46

Evidence for sars cov 2 - lysosome

Answer 46

Evidence that viral particles end up in lysosomes One of envelope proteins - E acts as ion channel, collapsing ph gradient and deacidifying lysosome Lysosome then fused with pm = releasing virus particles

Question 47

sars cov 2- what is exact story

Answer 47

Exact story not universally accepted Internal membranes are highly disrupted= making identification of organelles difficult Something along these lines happens (recall- lysosome evidence)

Question 48

sars cov 2 - if get diff variant

Answer 48

Still abs kinda effective Helps lessen symptoms