Nuclear Receptors

Nuclear receptors are a class of proteins found within cells that are responsible for sensing steroid and thyroid hormones and certain other molecules. They are called "nuclear" receptors because they are typically found in the cell nucleus, and their primary function is to regulate gene expression, which they do by interacting directly with DNA.Nuclear receptors have a common structure, including a DNA-binding domain (which allows them to bind to specific DNA sequences) and a ligand-binding domain (which binds to the hormone or other signaling molecule). When a nuclear receptor binds to its ligand, it undergoes a conformational change that allows it to regulate gene transcription.Nuclear receptors can be classified into two main groups:Endocrine receptors: These receptors bind to hormones that are secreted by endocrine glands and travel through the bloodstream to reach their target cells. Examples include the estrogen receptor, progesterone receptor, androgen receptor, glucocorticoid receptor, and thyroid hormone receptor.Adopted orphan receptors: These are nuclear receptors for which no endogenous ligand was known initially. However, over time, endogenous ligands have been identified for some of them, hence the term "adopted". Examples include peroxisome proliferator-activated receptors (PPARs), liver X receptors (LXRs), and farnesoid X receptors (FXRs).Nuclear receptors play critical roles in a wide variety of biological processes, including development, metabolism, and reproduction. Due to their role in regulating gene expression, they are also implicated in various diseases, including cancer, diabetes, and inflammatory diseases. As such, nuclear receptors are important targets for drug development.