An opioid is a psychoactive chemical that works by binding to opioid receptors, which are found principally in the central and peripheral nervous system and the gastrointestinal tract. The receptors in these organ systems mediate both the beneficial effects and the side effects of opioids.
Opioids are among the world's oldest known drugs; the use of the opium poppy for its therapeutic benefits predates recorded history. The analgesic (painkiller) effects of opioids are due to decreased perception of pain, decreased reaction to pain as well as increased pain tolerance. The side effects of opioids include sedation, respiratory depression, constipation, and a strong sense of euphoria. Opioids can cause cough suppression, which can be both an indication for opioid administration or an unintended side effect. Opioid dependence can develop with ongoing administration, leading to a withdrawal syndrome with abrupt discontinuation. Opioids are well known for their ability to produce a feeling of euphoria, motivating some to recreationally use opioids.
1. FUNCTION: Functions in lipid transport from the endoplasmic reticulum and is involved in a wide array of cellular functions probably through regulation of the biogenesis of lipid microdomains at the plasma membrane. Involved in the regulation of different receptors it plays a role in BDNF signaling and EGF signaling. Also regulates ion channels like the potassium channel and could modulate neurotransmitter release. Plays a role in calcium signaling through modulation together with ANK2 of the ITP3R-dependent calcium efflux at the endoplasmic reticulum. Plays a role in several other cell functions including proliferation, survival and death. Originally identified for its ability to bind various psychoactive drugs it is involved in learning processes, memory and mood alteration.
2. SUBUNIT: Forms a ternary complex with ANK2 and ITPR3. The complex is disrupted by agonists. Interacts with KCNA4 (By similarity).
3. SUBCELLULAR LOCATION: Nucleus inner membrane. Nucleus outer membrane. Endoplasmic reticulum membrane. Lipid droplet. Cell junction. Cell membrane. Cell projection, growth cone. Note=Targeted to lipid droplets, cholesterol and galactosylceramide-enriched domains of the endoplasmic reticulum. Enriched at cell-cell communication regions, growth cone and postsynaptic structures. Localization is modulated by ligand- binding.
4. ALTERNATIVE PRODUCTS: Event=Alternative splicing; Named isoforms=5; Name=1; IsoId=Q99720-1; Sequence=Displayed; Name=2; IsoId=Q99720-2; Sequence=VSP_021982; Name=3; Synonyms=Sigma-R1A; IsoId=Q99720-3; Sequence=VSP_021986; Name=4; IsoId=Q99720-4; Sequence=VSP_021984, VSP_021985; Name=5; IsoId=Q99720-5; Sequence=VSP_021981, VSP_021983; Note=No experimental confirmation available;
5. TISSUE SPECIFICITY: Widely expressed with higher expression in liver, colon, prostate, placenta, small intestine, heart and pancreas. Expressed in the retina by retinal pigment epithelial cells.
6. MISCELLANEOUS: Depletion by RNAi inhibits growth and survival signaling cascades and induces cell death. The antagonist rimcazole produces the same effect.
7. SIMILARITY: Belongs to the ERG2 family.
8. WEB RESOURCE: Name=Wikipedia; Note=Sigma-1 receptor entry; URL="http://en.wikipedia.org/wiki/Sigma_1_Receptor";