Liver X receptor

Liver X Receptor

Structure of the LXRα-RXR complex.

The Liver X Receptor (LXR) is a type of nuclear receptor that functions as a transcription factor regulating the expression of genes involved in cholesterol, fatty acid, and glucose metabolism. LXRs are activated by oxysterols, which are oxidized derivatives of cholesterol.

Types

There are two isoforms of the Liver X Receptor:

• LXRα (NR1H3) - Predominantly expressed in the liver, adipose tissue, intestine, and macrophages.
• LXRβ (NR1H2) - Ubiquitously expressed in various tissues throughout the body.

Function

LXRs play a crucial role in maintaining cholesterol homeostasis by regulating the expression of genes involved in cholesterol efflux, transport, and excretion. They also influence lipogenesis and gluconeogenesis.

Cholesterol Metabolism

LXRs promote the expression of genes such as ABCA1 and ABCG1, which are involved in the efflux of cholesterol from cells to high-density lipoprotein (HDL) particles. This process is essential for the reverse transport of cholesterol from peripheral tissues to the liver for excretion.

Lipid Metabolism

In addition to cholesterol metabolism, LXRs regulate genes involved in the synthesis and storage of fatty acids. They activate SREBP-1c, a key transcription factor that promotes the expression of enzymes required for fatty acid synthesis.

Glucose Metabolism

LXRs also have a role in glucose metabolism by modulating the expression of genes involved in gluconeogenesis and insulin sensitivity.

Mechanism of Action

LXRs function as heterodimers with the retinoid X receptor (RXR). Upon binding to their ligands, LXRs undergo a conformational change that allows them to bind to specific DNA sequences known as LXR response elements (LXREs) in the promoter regions of target genes.

Polar contacts in the LXR-RXR complex.

Clinical Significance

Due to their role in lipid and glucose metabolism, LXRs are considered potential therapeutic targets for the treatment of atherosclerosis, diabetes, and metabolic syndrome. Agonists of LXRs have been shown to reduce atherosclerotic plaque formation in animal models.

Related Pages

• Nuclear receptor
• Cholesterol metabolism
• Transcription factor
• Retinoid X receptor