manipulation of host cell compartments

lipid markers of cellular compartments

PI4P - endocytosis
PI3P - exocytosis
PI5P - lysosomal

protein markers of cellular compartments

TfR - recycling endosome
EEA1 - early endosome
LAMP1 - late endosome
CathD - lysosome

Rab control of vesicle budding

1. GEF stimulates GDP-GTP exchange and GDI released from Rab
2. Rab-GTP incorporated into budding vesicle
3. Vesicle docks and fuses with target membrane
4. GAP stimulates Rab GTP hydrolysis and GDI binds

SNARE mediated membrane fusion

v SNAREs are donors
t SNAREs are acceptors
Rab controls SNAREpin complex

methods of intracellular survival

arrest phagosome maturation
avoid endocytic pathway
survive in vacuole
vacuole lysis or motility

SCV

arrest phagosome maturation

biogenesis of SCV

1. early SCV - Rab5
2. intermediate SCV - Rab7
3. late SCV - coat

early SCV

retained cholesterol for flexibility
SopB PPase maintains PI3P lipid signature of early endosome and mediates Rab5 recruitment
recruitment of SNX1 which prevents M6PR recruitment and lysosomal transition

SopB experiment

immunofluorescence
mutant SopB had no Rab5 or PI3P recruitment

intermediate SCV

Rab7 replaces Rab5 and recruits RILP
RILP binds dynactin and links to dynein
migration toward golgi

experimental identification of SPI2

signature tagged mutagenesis shows which genes important for survival
mutants not present in output pool = important for survival
SPI2 - T3SS and effectors

late SCV

docks golgi and builds cytoskeletal coat
T3SS injects SSeF and G which tether to golgi
Sifs - dynamic lipid tubules that may help with SCV mobility
SifA required for SCV integrity - binds SKIP

role of SifA

sequesters Rab9 which is required for lysosomal hydrolase delivery
formed by fusion of nascent tubules with late endocytic compartments

LCV biogenesis

avoiding host endocytic pathway - phagocytosis

1. legionella in phagosome engages with vesicular components
2. recruitment of mitochondria and vesicles
3. LCV surrounded by RER

LCV - icms

group of genes with homology to E.coli pilus
acquire via HGT

LCV - Arf1 and Rab1

GTPases that modulate ER/golgi trafficking
early ER recruitment in LCV requires Arf1

LCV - RalF

Arf GEF mimic
recruits Arf to LCV

SidM

high affinity for Rab1-GDP
removes GDI
AMPylates Rab1 to lock in GTP active form
blocks GAP access

LidA

enhances Rab1 recruitment

SidD

deAMPylase - antagonises SidM to allow LepB GAP to convert Rab1 to inactive form
constantly active so Rab1 maintained on LCV

LepB

GAP inactivates Rab1

AnkX

inhibits Rab1 controlled by Lem3

SidC

maintains LCV vacuole
secretory marker
Ub ligase

T4SS

functions in conjugation

chlamydia inclusion

pseudo-organelle specialised for intracellular replication
reduced genome - exploits host for activity
has T3SS and effectors
associates with ER membrane

inclusion proteins

40 proteins in membrane with no homology to other bacterial proteins
may use tails to bind host proteins to acquire nutrients or subvert trafficking

chlamydia IncA

SNARE mimic
fuses inclusions in the same cell

chlamydia IncD and V

hijack ER ceramide transport pathway to acquire sphingomyelin
recruit mitochondria to get sphingomyelin through VAP/CERT pathway

plasmodium PVM

contains rbc and parasite membrane
no rbc proteins
rbc doesn't get smaller or synthesise new lipids
rhoptry membrane persists - membranous whorls

cryptosporidium PV

no moving junction
forms buds on membrane
forms circular pedestal
remodels cytoskeleton and membrane

leishmania LPG

invades phagocytic cells by exploiting phagocytosis
blocks complement lysis
engages FcgR with gp63
engage complement receptors for silent entry with gp63

T.cruzi PV

needs acidic environment for development
membrane wounding and repair provides entry route
exits vacuole via TcTOX pore forming proteins

plasmodium maurer's clefts

compartment beneath erythrocyte membrane
tethered via MAHRP2
receive exported proteins via J dots

plasmodium knobs

mediate cytoadherance
PfEMP1 embedded in KARHP

plasmodium soluble nutrient uptake

Clag3 on PM
EXP2 on PVM
EXP2 expressed throughout whole life cycle

plasmodium hemaglobin uptake

cytosome transport to food vacuole
double membraned invagination of PVM and parasite membrane where lumen is continuous with rbc cytosol
depends on dynamin

plasmodium protein export

PTEX complex transports unfolded proteins that get folded in cytosol
only 3-5 exported during liver stage due to MHCI and apoptosis pathways