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PXR

PXR, or pregnane X receptor, is a nuclear receptor that acts as a ligand-activated transcription factor regulating genes involved in xenobiotic metabolism and transport. It is encoded by NR1I2 and belongs to the nuclear receptor superfamily. When a suitable ligand binds, PXR forms a heterodimer with the retinoid X receptor (RXR) and binds to response elements in the promoter regions of target genes, promoting transcription.

Expression of PXR is highest in the liver and intestine, with detectable levels in kidney, brain, and

Ligands for PXR are diverse and include prescription drugs (notably rifampin in humans), natural products (e.g.,

Clinical and pharmacological relevance includes the potential for drug–drug interactions via altered clearance, variability in response

placenta.
Through
transcriptional
control
of
phase
I
enzymes
such
as
CYP3A4
and
CYP2B6,
phase
II
enzymes
such
as
UGTs,
and
transporters
including
MDR1/ABCB1
and
members
of
the
OATP
family,
PXR
coordinates
the
metabolism
and
disposition
of
a
broad
range
of
endogenous
and
exogenous
compounds.
hyperforin
from
St.
John's
wort),
bile
acids,
steroids,
and
other
xenobiotics.
Endogenous
ligands
may
reflect
metabolic
state
and
can
interact
with
other
nuclear
receptors,
leading
to
coordinated
responses
in
lipid
and
bile
acid
homeostasis.
due
to
NR1I2
genetic
differences,
and
implications
for
cholestasis
and
liver
cancer
biology
in
some
contexts.
PXR
is
the
subject
of
ongoing
research
into
receptor
structure,
ligand
specificity,
species
differences,
and
therapeutic
modulation.