Vl 3 - host vesicle transport Flashcards
Why would parasites exploit host vesicular transport?
- To invade
- To avoid the immune response
- To obtain resources
Which existing cellular entry routes are used by pathogens for invasion?
All routes are used:
- phagocytosis (lysosome)
- macropinocytosis (early endosome)
- clathrin dependent endocytosis (early endosome)
- caveolin dependent endocytosis (early endosome)
- independent endocytosis (early endosome)
What is the first part of the Leishmania life cycle after the sandfly injects it into the mammalian host?
- phagocytic cells recruited to biting site
- metacyclic promastigotes actively invade macrophages and granulocytes or are phagocytised
- promastigotes transform into amastigotes ⇒ multiply by simple cell division
- amastigotes leave infected cell and infect new macrophages (or get taken up)
What are the biggest virulence factors in Leishmania during the invasion?
- Lipophosphoglycan (LPG)
- gp63 (protease that cleaves C3b)
how can Leishmania enter the host cell?
- classic path: Via antigen detection
- alternative: Leishmania gp63 cleaves C3b (attached antigen on surface) ⇒ inactive product still recognized by CR3 (host receptor) ⇒ CR3-mediated phagocytosis does NOT cause oxidative burst in macrophage ⇒ Leishmania does not die upon entrance
What does Leishmania Glycophospholipid (LPG) do?
- LPG inserted into phagosomal membrane
⇒ inhibits insertion of SytV (exocytosis and fusion regulator) into phagosomal membrane
⇒ excludes vesicular proton ATPase (V-ATPase) from phagosome
⇒ pH does not decrease
⇒ phagosome maturation is delayed.
⇒ phagosome can’t fuse with lysosome
⇒ parasite does not die, but differentiates to amastigote (which is resistant to lysosome function) and multiplies
How can phagosomes or the process of phagocytosis be made visible under the microscope?
- Staining of LAMP-1 and dextran
Which proteins regulate the binding and fusion of two membranes?
v-SNARE and t-SNARE
how does trypanosma cruzi enter it’s host cell??
T. cruzi wounds host cell membrane ⇒ Ca2+ influx increase ⇒ recruitment and fusion of host lysosomes around the parasite ⇒ trypomastigote ends up in lysosome-derived vacuole ⇒ escape of vacuole ⇒ differentiation to amastigote and replication
General mechanism in the cell:
- Ca2+ Influx
- lysosomes recruited, secrete ASM (acid sphingomyelinase) near wound
- ASM binds to plasma membrane, ceramides generation - plasma membrane wounds are endocytosed via ceramide vesicles
- Inside these vesicles is ASM (and parasite)
⇒ T. cruzi uses the mechanisms of cell wound healing to invade the cells.
What other functions does gp63 have?
- immune evasion by degradation of VAMP8 (a SNARE)
⇒ inhibits antigen presentation of infected macrophages to T cells and thus T cell activation
- VAMP8 mediates NOX2 (NADPH-oxidase subunit) delivery to phagosome (needed for MHC I presentation to T-cells)
function of LC3?
role in plasmodium invasion?
how is this process called?
- Light Chain 3. Microtubule-associated soluble protein.
- Main component of the autophagosome (hence its marker).
- Facilitates the administration of autophagosomal membranes to lysosomes
- Plasmodium liver stage surrounded by LC3 in non-canonical way ⇒ Plasmodium takes up LC3 to bypass elimination by autophagy process in hepatocytes (autophagy through formation of autolysosome)
PAAR response: Plasmodium-associated autopagy related response)
what is ATG5 and what happens in respect of plasmodium survival if it’s inhibited or knocked out??
ATG5 (Autophagy related 5):
- coded protein functions in combination with ATG12
- takes part in autophagic vesicle assembly
- no autophagic vesicle formation when ATG5 inhibited ⇒ no autophagy ⇒ better survival for plasmodium (autophagy can kill parasite BUT parasite size is larger with autophagy on ⇒ some advantage if not shut down)
- autophagy is used by cells to degrade things they dont want
how can cell autophagy be stimulated
- via starvation of ressources (In lab: amino acid-starvation)
what are LAMP1/2 proteins? function?
Lysosome-associated membrane proteins
- needed for intake of host cholesterol (crucial for plasmodium survival) into PV
- LDL-derived-cholesterol transported into the cell via late endosomes
- NPC (Niemann–Pick type C) and LAMP mediate cholesterin exit from late endosomes
- exit blocked ⇒ plasmodiom growth inhibited
- Filipin (chemical component) blocks entrance of cholesterin into PV
how does T.gondii interact with host organelles?
- recruits host organelles (mitochondria, microtubuli, ER, etc) to parasitophous vacuole
- fragmentates host golgi and assiociates it to PV
- takes host sphingolipides
- interacts with rab-protein membranes of the hosts ⇒ Rab14, Rab11 are found in toxo PV
