Sigma non-opioid intracellular receptor 1 (Sigma-1 receptor) (SIGMAR1)

The Sigma non-opioid intracellular receptor 1, commonly known as the Sigma-1 receptor (SIGMAR1), is a unique ligand-operated molecular chaperone primarily localized at the mitochondria-associated endoplasmic reticulum membrane (MAM) [1, 2]. Unlike traditional cell-surface receptors, SIGMAR1 functions by stabilizing client proteins, such as the Inositol 1,4,5-trisphosphate receptor (IP3R), to facilitate essential calcium signaling between the ER and mitochondria [3, 5]. Under conditions of cellular stress or upon agonist binding, the receptor dissociates from its binding partner BiP/GRP78 and translocates to various cellular compartments, where it modulates the activity of diverse ion channels and G protein-coupled receptors [10, 14]. This regulatory versatility makes it a critical player in maintaining proteostasis, mitochondrial bioenergetics, and neurotransmission [5, 13]. SIGMAR1 has emerged as a high-priority therapeutic target for neurodegenerative and neuropsychiatric disorders, including Alzheimer’s disease, Amyotrophic Lateral Sclerosis (ALS), and major depression [3, 8, 10]. Loss-of-function mutations in the SIGMAR1 gene are directly linked to juvenile ALS and distal hereditary motor neuropathies [8, 10]. Pharmacological agonists, such as pridopidine and blarcamesine, are being investigated for their neuroprotective potential by restoring ER-mitochondrial crosstalk and reducing oxidative stress [3, 13]. Conversely, SIGMAR1 antagonists have shown efficacy in preclinical models for treating neuropathic pain and certain cancers, where they disrupt the receptor's pro-survival signaling in malignant cells [12, 14]. Despite its therapeutic promise, challenges remain regarding receptor selectivity and the systemic impact of its widespread expression in the human body [13, 15].

Other names

Sigma-1 receptorSIGMAR1S1ROPRS1Sigma-1RSR-BPSRBPSigma 1-type opioid receptorhSigmaR1

Functions as a ligand-regulated molecular chaperone that stabilizes Inositol 1,4,5-trisphosphate receptors (IP3R) at the mitochondria-associated ER membrane (MAM) to facilitate calcium signaling. It also modulates the conductance of voltage-gated ion channels and the trafficking of G protein-coupled receptors following translocation from the ER.