Microcantilever-based Nanomechanical Studies of the Orphan Nuclear Receptor Pregnane X Receptor-Ligand Interactions

Kasey L Hill,Pampa Dutta,Michael J Sepaniak,Zhou Long

doi:10.4236/jbnb.2011.22017

Kasey L Hill, Pampa Dutta + Show 2 more

Open Access

https://doi.org/10.4236/jbnb.2011.22017

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Abstract

Human pregnane X receptor (PXR) is of vital importance in pharmaceutical and exogenous compound metabolism within the body. This provides strong motivation for investigating this orphan receptor’s activation by various pharmaceuticals, xenobiotics, and endocrine disrupting chemicals (EDCs). A nanomechanical transducer is developed to study xenobiotic and EDC interactions with the bioreceptor PXR’s ligand binding domain (LBD). The combination of immobilized LBD PXR with a nanostructured microcantilever (MC) platform allows for the sensitive, label-free study of ligand interaction with the receptor. PXR shows real-time, reversible responses when exposed to a specific pharmaceutical, EDCs, and xenobiotic ligands. Three EDCs binding interactions are tested, which include phthalic acid, nonylphenol, and bisphenol A, with PXR. PXR LBD was exposed to rifampicin, a potent PXR activator, with various injection and recovery times to study their interaction. A two protein array of PXR and estrogen receptor ? (ER-?) directly compares the nanomechanical responses of these receptors with rifampicin on a single platform.

Highlights

Humans are exposed to harmful chemicals and contaminants each day
Our studies focus on developing MC systems utilizing the nuclear receptor pregnane X receptor (PXR) as the immobilized bioreceptor phase
We demonstrate that our immobilization process does not appreciably denature the PXR

Summary

Introduction

It is essential that these toxins are removed or detoxed from the body These foreign compounds or xenobiotics, which include environmental toxins, endogenous hormones, steroids, pharmaceuticals, and dietary supplements, trigger a line of defense mechanisms within the body. The family of cytochrome P450 enzymes are the main xenobiotic defenders for mammals. Cytochrome P4503A4 (CYP3A4), a critical member of our defense system, makes the removal of many unwanted xenobiotics possible [2]. When xenobiotic ligands bind to a specific nuclear hormone receptor, the interaction transcriptionally activates CYP3A4 [5]. In 1998, a novel orphan human nuclear receptor was identified and termed pregnane X receptor (PXR), steroid and xenobiotic receptor (SXR), pregnane activated receptor (PAR), and NR1I2 [6,7,8,9].

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