Sigma Receptor

Sigma receptors (subtypes sigma-1 and sigma-2) are a unique class of binding sites expressed throughout the mammalian body. The endogenous ligand for these sites has not been identified, but steroid hormones (particularly progesterone), sphingolipid-derived amines and N,N-dimethyltryptamine can bind with fairly high affinity.

The sigma-1 receptor (σ1R) is an endoplasmic reticulum (ER)-resident chaperone protein that acts like an inter-organelle signaling modulator. It participates in many biological processes including nociception, cancer, stroke, memory, drug addiction, cardiac activity, and Alzheimer’s disease. The sigma-2 (σ2R) receptor is overexpressed in various human tumors. It has been validated as a biomarker for proliferating tumors.