Nuclear hormone receptors NHR

The adaptive response to xenobiotics is orchestrated in the cell by a subset of receptors that act primarily in the nucleus. For this chapter, we will employ a liberal definition of nuclear receptor (NR) that includes all signaling molecules that function as ligand-binding transcription factors that bind to specific DNA enhancer sequences and upregulate the transcription of CYP genes. Two classes of NRs will be discussed in this chapter. Members of the nuclear hormone receptor (NHR) superfamily to be reviewed include the constitutive androstane receptor (CAR), the pregnane X-receptor (PXR), and the peroxisome prolifera-tor activated receptors (PPARs). A single member of the PAS superfamily, the aryl hydrocarbon receptor (AHR), will also be discussed. 

Nuclear hormone receptor (NHR) A transcription factor whose activity is regulated by a small molecule (the ligand), such as a steroid (estrogen, cortisol, etc.) or an amino acid (thyroid hormone). Most NHRs are transcriptional activators in the presence of ligand some NHRs also act as transcriptional repressors in its absence. 

The second example regarding HDAC targeting in transcriptional repression involves certain members of the nuclear hormone receptor (NHR) superfamily. Some of these proteins—GR, for example—are constitutively cytoplasmic and translocate to their site of action, the nucleus, only... 

Nuclear and steroid hormone receptors (NHRs), in contrast to GPCRs, are ligand-inducible transcription factors, which when liganded directly bind to... 

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