Retinoid X receptor alpha

Retinoid X receptor alpha (RXR-alpha), also known as NR2B1 (nuclear receptor subfamily 2, group B, member 1), is a nuclear receptor that in humans is encoded by the RXRA gene. RXR-alpha belongs to the family of nuclear receptors and is involved in mediating the effects of retinoic acid, a metabolite of vitamin A that plays key roles in cell growth and differentiation.

Structure

The RXR-alpha protein has a modular structure and contains several functional domains. The A/B domain at the N-terminus contains a ligand-independent activation function (AF-1), while the C domain, also known as the DNA-binding domain (DBD), is responsible for binding to specific DNA sequences known as hormone response elements (HREs). The D domain, or hinge region, connects the DBD to the E/F domain, which contains the ligand-binding domain (LBD) and a ligand-dependent activation function (AF-2).

Function

RXR-alpha forms heterodimers with several other nuclear receptors, including peroxisome proliferator-activated receptors (PPARs), vitamin D receptor (VDR), and thyroid hormone receptor (TR). These heterodimers bind to specific DNA sequences and regulate the transcription of target genes. RXR-alpha is also capable of forming homodimers that bind to DNA and regulate gene expression.

In addition to its role in gene regulation, RXR-alpha also plays a role in cell differentiation and apoptosis. It is involved in the regulation of lipid metabolism, glucose metabolism, and inflammation, and has been implicated in several diseases, including cancer, diabetes, and atherosclerosis.

Clinical significance

Alterations in the function of RXR-alpha have been associated with several diseases. For example, mutations in the RXRA gene have been linked to leukemia and lung cancer. In addition, abnormal expression of RXR-alpha has been observed in breast cancer, prostate cancer, and colorectal cancer.

See also

• Retinoid X receptor
• Nuclear receptor
• Retinoic acid