Regulation nuclear receptor proteins

Steroid binding to a nuclear receptor protein allows the receptor to regulate the expression of specific genes. 

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptor proteins that play essential roles in the regulation of cell differentiation development and metabolism (McGuire and Lucas 1991 Gibson and Lake 1993 Berger and Moller... 

Thyroid hormones enter the extrathyroidal tissues by the action of specific transporters the organic anion transport protein (OATP) and the monocarboxylic transporter (MCT8) (Ekins et al. 1994 Friesema et al. 1999, 2005). Within some cells, deiodinating enzymes can remove an iodine atom from the T4 or T3 molecules and thereby modify the sensitivity of a cell to the actions of the thyroid hormones. The cellular actions of the thyroid hormones are mediated by nuclear receptor proteins, which bind to DNA and regulate transcription with at least two types of genes that encode these receptors (Barettino, Ruiz, and Stunnenberg 1994) these also provide a negative feedback action on the hypothalamic-pituitary axis. T4 is sometimes... 

As stated in Chapter 7, peroxisome proliferator-activated receptors (PPARs) are a group of nuclear receptor proteins that function as transcription factors regulating the expression of genes associated with cell differentiation, inflammation. 

Another example is a recently discovered second mode of action by which nuclear receptors modulate transcription. In contrast to DNA-binding-dependent mechanisms, cross talk refers here to gene regulation by protein-protein-interaction of nuclear receptors with other transcription factors, such as AP-1 or NF-kB. Consequently, the nuclear receptor acts as a corepressor or coactivator of transcription. 

Nuclear Receptor Regulation of Hepatic Cytochrome P450 Enzymes. Figure 1 General mechanism for transcriptional activation of CYP genes by xenochemicals that activate their cognate xeno-receptor proteins. In the case of Ah receptor, the receptor s heterodimerization partner is Arnt, whereas in the case of the nuclear receptors CAR, PXR, and PPARa, the heterodimerization partner is RXR. The coactivator and basal transcription factor complexes shown are each comprised of a large number of protein components. 

A nuclear receptor that is a key transcription factor in adipocytes. It plays a critical role in the control of adipocyte differentiation and is involved in the regulation of the expression of specific adipokines, including leptin and adiponectin. It has anti-inflammatory actions and is the target of the thiazolidinedione drugs. The preintegration complex is a complex of retroviral DNA and proteins that translocates from the cytosol into the nucleus prior to integration. Gene Therapy... 

The regulation of transcription by hormones requires a controlled limitation in order to guarantee that the protein is produced in adequate amounts. This process, nevertheless, is very poorly understood for members of the family of nuclear receptors. 

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