bioRxiv (Cold Spring Harbor Laboratory),
Journal Year:
2023,
Volume and Issue:
unknown
Published: Dec. 6, 2023
ABSTRACT
How
intracellular
bacteria
subvert
the
major
histocompatibility
complex
(MHC)
class
I
pathway
is
poorly
understood.
Here,
we
show
that
obligate
bacterium
Orientia
tsutsugamushi
uses
its
effector
protein,
Ank5,
to
orchestrate
proteasomal
degradation
of
MHC
gene
transactivator,
NLRC5.
Ank5
a
tyrosine
in
fourth
ankyrin
repeat
bind
NLRC5
N-terminus
while
F-box
directs
host
SCF
ubiquitination
K1194
leucine-rich
region
dictates
susceptibility
-
and
Ank5-mediated
degradation.
The
ability
O.
strains
degrade
correlates
with
ank5
genomic
carriage.
Ectopically
expressed
can
but
not
protects
transactivator
during
infection.
Thus,
an
immunoevasin
bipartite
architecture
rid
cells
molecules.
This
study
offers
insight
into
how
pathogens
impair
expression
benefit
their
survival.
Infection and Immunity,
Journal Year:
2025,
Volume and Issue:
unknown
Published: Feb. 20, 2025
ABSTRACT
Cullin-1
(Cul1),
a
cullin–RING
ubiquitin
ligase
component,
represses
c-MYC
activity
in
the
nucleus.
Orientia
tsutsugamushi
causes
potentially
fatal
rickettsiosis,
scrub
typhus.
The
obligate
intracellular
bacterium
encodes
an
arsenal
of
ankyrin
repeat-containing
effectors
(Anks),
many
which
carry
eukaryotic-like
F-box
motif
that
binds
Cul1.
O.
reduces
Cul1
levels
This
phenomenon
is
not
due
to
alteration
neddylation
but
bacterial
burden-
and
protein
synthesis-dependent.
Five
11
Anks
capable
binding
(Ank1,
Ank5,
Ank6,
Ank9,
Ank17)
sequester
it
cytoplasm
when
each
ectopically
expressed.
Ank1
Ank6
proteins
with
alanine
substitutions
their
F-boxes
render
them
unable
bind
cannot
exclude
from
Coincident
reduction
nuclei
-infected
cells,
nuclear
are
elevated,
target
genes
differentially
Several
these
regulate
apoptosis.
resistance
cells
staurosporine-induced
apoptosis
recapitulated
uninfected
expressing
or
alanine-substituted
versions
thereof
Other
F-box-containing
nucleus
also
fail
confer
Overall,
modulates
Cul1:c-MYC
intranuclear
balance
as
anti-apoptotic
strategy
functionally
linked
subset
its
Anks.
Current Opinion in Microbiology,
Journal Year:
2023,
Volume and Issue:
74, P. 102318 - 102318
Published: April 18, 2023
Recent
discoveries
of
basal
extracellular
Rickettsiales
have
illuminated
divergent
evolutionary
paths
to
host
dependency
in
later-evolving
lineages.
Family
Rickettsiaceae,
primarily
comprised
numerous
protist-
and
invertebrate-associated
species,
also
includes
human
pathogens
from
two
genera,
Orientia
Rickettsia.
Once
considered
sister
taxa,
these
bacteria
form
distinct
lineages
with
newly
appreciated
lifestyles
morphological
traits.
Contrasting
other
rickettsial
Anaplasmataceae,
Rickettsia
species
do
not
reside
host-derived
vacuoles
lack
glycolytic
potential.
With
only
a
few
described
mechanisms,
strategies
for
commandeering
glycolysis
support
cytosolic
growth
remain
be
discovered.
While
regulatory
systems
this
unique
mode
intracellular
parasitism
are
unclear,
conjugative
transposons
provide
insights
that
critical
determining
how
obligate
overtake
eukaryotic
cytosol.
Anaplasma
phagocytophilum
causes
granulocytic
anaplasmosis,
a
globally
emerging
zoonosis
that
can
be
severe,
even
fatal,
and
for
which
antibiotic
treatment
options
are
limited.
A.
lives
in
an
endosomal-like
compartment
interfaces
with
multiple
organelles
from
it
must
ultimately
exit
to
spread
within
the
host.
How
bacterium
accomplishes
these
tasks
is
poorly
understood.
mSphere,
Journal Year:
2023,
Volume and Issue:
8(6)
Published: Oct. 18, 2023
Obligate
intracellular
bacteria,
or
those
only
capable
of
growth
inside
other
living
cells,
have
limited
opportunities
for
horizontal
gene
transfer
with
microbes
due
to
their
isolated
replicative
niche.
The
human
pathogen
Ot,
an
obligate
bacterium
causing
scrub
typhus,
encodes
unusually
high
copy
number
a
~40
mobile
genetic
element
that
typically
facilitates
across
microbes.
This
proliferated
is
heavily
degraded
in
Ot
and
previously
assumed
be
inactive.
Here,
we
conducted
detailed
analysis
this
eight
strains
discovered
two
at
least
one
intact
copy.
implies
the
still
moving
populations
suggests
genome
may
even
more
dynamic
than
appreciated.
Our
work
raises
questions
about
microbial
evolution
sounds
alarm
gene-based
efforts
focused
on
diagnosing
combatting
typhus.
Nature Communications,
Journal Year:
2024,
Volume and Issue:
15(1)
Published: Sept. 14, 2024
How
intracellular
bacteria
subvert
the
major
histocompatibility
complex
(MHC)
class
I
pathway
is
poorly
understood.
Here,
we
show
that
obligate
bacterium
Orientia
tsutsugamushi
uses
its
effector
protein,
Ank5,
to
inhibit
nuclear
translocation
of
MHC
gene
transactivator,
NLRC5,
and
orchestrate
proteasomal
degradation.
Ank5
a
tyrosine
in
fourth
ankyrin
repeat
bind
NLRC5
N-terminus
while
F-box
directs
host
SCF
ubiquitination
leucine-rich
region
dictates
susceptibility
Orientia-
Ank5-mediated
The
ability
O.
strains
degrade
correlates
with
ank5
genomic
carriage.
Ectopically
expressed
can
but
not
protects
transactivator
during
infection.
Thus,
an
immunoevasin
bipartite
architecture
rid
cells
reduce
surface
molecules.
This
study
offers
insight
into
how
pathogens
impair
expression.
bioRxiv (Cold Spring Harbor Laboratory),
Journal Year:
2025,
Volume and Issue:
unknown
Published: Jan. 4, 2025
Abstract
Orientia
tsutsugamushi
is
an
obligate
intracellular
bacterium
found
in
Leptotrombidium
mites
that
causes
the
human
disease
scrub
typhus.
A
distinguishing
feature
of
O.
its
extensive
strain
diversity,
yet
differences
virulence
between
strains
are
not
well
defined
nor
understood.
We
sought
to
determine
bacterial
drivers
pathogenicity
by
comparing
murine
infections
using
seven
combined
with
epidemiological
data
rank
each
terms
relative
virulence.
Murine
cytokine
expression
revealed
two
most
virulent
strains,
Ikeda
and
Kato,
induced
higher
levels
IL-6,
IL-10,
IFN-γ
MCP-1
than
other
consistent
increased
these
cytokines
severe
typhus
patients.
identify
mechanistic
basis
observed
differential
their
genomes,
vitro
growth
properties
cytokine/chemokine
induction
host
cells.
there
was
no
single
gene
or
group
correlated
virulence,
clear
pattern
rate
predicted
disease.
However,
microscopy-based
analysis
infection
cycle
only
fully
avirulent
our
study,
TA686,
differed
from
all
subcellular
localisation
surface
protein
ScaC.
conclude
distributed
throughout
genome,
likely
large
varying
arsenal
effector
proteins
encoded
different
interact
complex
ways
induce
differing
immune
responses
thus
outcomes
mammalian
hosts.
Author
Summary
Scrub
a
vector-borne
caused
tsutsugmushi
spread
mites.
There
numerous
this
some
causing
more
humans
others,
do
cause
any
illness
at
all.
The
factors
driving
understood,
gaining
insight
into
them
could
aid
vaccine
development
help
predict
severity
new
isolates.
To
better
typhus,
we
carried
out
experiments
which
compared
diverse
for
animals.
measured
ability
mice,
so
reliably
classify
as
model.
then
analysed
various
genomic
biological
aspects
markers
both
mice
humans.
report
here
factor
predicts
whether
will
be
pathogenic
not,
but
process
resulting
activity
multiple
genes
working
together
drive
host,
either
clearance
bacteria
escalating
Future
work
exploring
relationship
disentangle
detail.
Pathogens,
Journal Year:
2025,
Volume and Issue:
14(5), P. 478 - 478
Published: May 14, 2025
Scrub
typhus
is
an
emerging
chigger-borne
disease
caused
by
the
obligate
intracellular
bacterium
Orientia
tsutsugamushi.
Necroptosis
a
form
of
programmed
cell
death
(PCD)
mediated
RIPK3
(serine/threonine
kinase
receptor
interacting
protein
3)
and
its
downstream
effector
MLKL
(mixed-lineage
domain-like).
While
O.
tsutsugamushi
modulates
apoptosis,
another
PCD,
interplay
with
necroptosis
unknown.
Much
pathobiology
linked
to
ankyrin
repeat
(AR)-containing
effectors
(Anks).
Two
these,
Ank1
Ank6,
share
similarities
cowpox
AR
protein,
vIRD
(viral
inducer
degradation)
that
prevents
necroptosis.
Here,
we
show
Ank6
reduce
cellular
levels
although
not
as
robustly
mechanistically
distinct
from
vIRD.
infection
lowers
amounts
does
elicit
in
endothelial
cells.
In
HeLa
cells
ectopically
expressing
RIPK3,
fails
inhibit
phosphorylation
well
death.
colocalization
or
Listeria
monocytogenes,
intracytoplasmic
pathogen,
was
observed.
Thus,
reduces
but
cannot
this
PCD
pathway
once
it
induced.
This
study
first
step
toward
understanding
how
relationship
between
contributes
scrub
pathogenesis.
bioRxiv (Cold Spring Harbor Laboratory),
Journal Year:
2025,
Volume and Issue:
unknown
Published: May 17, 2025
Arthropods,
the
most
diverse
phylum
on
Earth,
are
hosts
to
a
plethora
of
bacterial
parasites
that
secrete
various
effectors
unknown
function
during
infection.
The
prevalent
these
is
intracellular
bacterium
Wolbachia
pipientis
.
microbe
infects
between
40-60%
insect
species,
causes
important
reproductive
manipulations,
and
limits
virus
replication
in
arthropod
vectors,
becoming
promising
biocontrol
agent.
Understanding
molecular
basis
infection
Wolbachia-
induced
phenotypes
critical
use
vector
control.
These
ankyrin
repeat
proteins
(WARPs)
represent
highly
dynamic
part
pangenome
remain
thus
far,
largely
uncharacterized.
Here,
we
perform
genetic
screens
identify
interactions
w
Mel
WARPs
their
target
host
Drosophila
melanogaster
Our
results
strong
two
proteins,
WARP434
WARP754,
with
targets
(CG11327
Ptp61F,
respectively).
Heterologous
expression
extremely
toxic
tissues
toxicity
dependent
domain
each
WARP.
Importantly,
knockdown
alleviates
toxicity,
confirming
WARP/target
interactions.
Finally,
antibodies
targeting
both
show
by
cells.
how
manipulates
its
biology
which
pathways
it
will
help
us
divine
parasite
Earth
interacts
at
level.
screen
first
step
towards
goal.
Molecular
drive
co-evolutionary
arms
races
pathogens.
shape
structure
enabling
immunity
or
virulence
details
unfold
events
illustrates
not
only
co-evolve
level
but
also
may
characterize
poorly
understood
proteins.
earth
pipientis,
insects
harboring
symbiont.
cells
tools
uses
alter
cell
used
symbiont
interface
specific
mechanisms
underlying
this
host-microbe
interaction
shed
light
an
symbiont,
control
populations
disease
transmission,
interact
protein
contributes
Infection and Immunity,
Journal Year:
2022,
Volume and Issue:
90(12)
Published: Nov. 14, 2022
Orientia
tsutsugamushi
is
an
etiologic
agent
of
scrub
typhus,
a
globally
emerging
rickettsiosis
that
can
be
fatal.
The
bacterium’s
obligate
intracellular
lifestyle
requires
its
interaction
with
host
eukaryotic
cellular
pathways.