membrane remodelling Flashcards
Where is membrane remodelling by viruses involved in?
- infection
- genome replication
- egress
- cell to cell spread
Which membranes are remodelled by which viruses?
ER:
- Polio
- HCV
- Corona
ER/Golgi/intermediate
- kunjin virus
Lysome/PM
- Rubella virus
- alpha virus
Mitochondria
- flock house virus
How can membranous bending be generated? Name Examples
By proteins via different mechanisms:
- membrane protein shape
- amphiphatic helix insertion !
- membrane protein oligimerization
- scaffolding by peripheral proteins
- lipid composition
Examples:
- clathrin coated vesicles
- coatamer proteins COPI and COPII
How can nidovirales induce the formation of double membrane vesicles?
different models:
1. protrusion and detachment model:
-ER cisterna start to bend, pinches off and seals
2. double buddig model: a single membrane vesicles buds into the lumen of the ER and then buds out again
where do SARS Cov 2 virons budd and assemble?
at the ERGIC membrane
What induces autophagy and how does it work?
- Reaction to stress, starvation and ifection
- compasing of cytoplasmatic parts with sickle shaped vacoules
- fusion with lysosomes
- content degradation in autophagosomes
How many autophagy related gene s (Atg) are there? What happens if ATG12 and lC3 are knocked down durin Poliovirus infection
27 atg
– > knock down does not inhibit replication of polio virus but agress of new viruses
What induces membrane concativity?
oligomeric viral membrane proteins
Do all + Strand RNA viruses modify intracellular mmebrane systems or generate vesicle like structues or vesicles networks? Why?
yes, because RNA replication always takes place at membranes
What are the functional properties of remodelling of membranes by + Strand RNA viruses?
- shielding of dsRNA intermediates from the innate immune system
- resistamce against RNases and proteases
- high local concentration of viral components
- contact with ER components of the cell
which protein plays a role in flock house remodelling of the mitochondrial outer membrane?
ptnA
Where does the alphavirus chikungunya virus replicate its genome? Which viral proteins play a role?
- in membrane spherules at the plasma membrane
- nsp1 is base for assembly of larger protein complex
- nsp1 recruits nsp2
Where does the energy for membrane remodelling by chikungunya virus come from?
from the released energy during RNA polymerization
How are progeny + strand RNA genomes released from replication vesicles? To what is it comparable?
RNA synthesis takes place close the the pore structure for the release of this RNA into the cytoplasm –> comparable to dsRNA synthesis which takes place in cores close to the exit channels
Describe the dengue virus vesicles. Where does budding occur?
- ER derived
- netwotk of convoluted membranes
- invagination of ER membranes
- have pores
- look like nests
- budding of virus particles on ER membranes opposed to pores –> budding occurs into the ER
Describe HCV rearrangements in HCV infected cells
- derived from ER
- vesicles are protrusions of the ER membrane
- membranous webs consisting of single and double membrane vesicles
- vesices are frequently connected to the ER membrane via a neck like structure
compare dengue and HCV membrane remodelling
both form vesicles derived from the ER but
- dengue: invaginations
- HCV: protrusions
describe the envelopment and cell egress of herpes viruses
- two proteins UL34 and UL31 enable the stride of the capsid through the nuclear membrane into the ER
- nuclear membrane istaken along as an envelope but this is lost during egress out of the ER
- entry of capsid into golgi –> envelopment with golgi membrane stays
- egress out of golgi via secretory vesicles leads to a second lipid envelope which is lost during the egress at the PM
where does herpes virus gets it envelope from?
golgi
Name mechanism through which cell-cell communication works
- synapses
- cytonemes
- gap junctions
- tunneling nanotubes
can filopodia be abused by viruses?
yes
Give an explanation why the time scale of spreas is not in line with speed of replication in vaccinia virus
due to selective infection of uninfected cells –> new particles are bounced off and onto neighboring cell via actin tail formation and membrane protrusions triggered by virus particles (A33 and A36 viral proteins)
–> optimal efficiency for viral spread
How do Poxvirus, HIV, MLV, ASFV, CMV and RSV do cell- to cell spread?
Pox: projection on actin tails
HIV: virological synapses, nanotubes
MLV: captur of filopodia
ASFV: induction of filopodia
CMV: cell to cell fusion
RSV: syncytium formation
What role do FAST proteins play in reoviurs encoded cell-cell fusion machinery for viral spread via formation of syncytia?
- is a NSP (so not in virion)
- mediate only the step of fusion
- only interact with membranes but not adhesion
- active actin remodelling required
Name modes for viral spread from cell to cell and give example viruses
- membrane fusions, synctia formation: Herpes, retro
- basolateral budding between tight junctions: herpes
- budding into synpatic cleft: herpes, rhabdo, paramyxo
- virus induced actin containing membrane structures carry virions into adjoining cell: murine leukemia virus
- actin containing nanotubes for transport into adjoining cells: HIV
- virological synpases
Which virus can induce membrane bdriges between cells? How?
retroviruses via contact between viral coating proteins in filopodia and cellular receptor in the target membrane
