Solute carrier family 22 member 3 (SLC22A3) also known as the organic cation transporter 3 (OCT3) or extraneuronal monoamine transporter (EMT) is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

that in humans is encoded by the ''SLC22A3''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

. Polyspecific organic cation transporters in the liver, kidney, intestine, and other organs are critical for elimination of many endogenous small organic cations as well as a wide array of drugs and environmental toxins. This gene is one of three similar cation transporter genes located in a cluster on chromosome 6. The encoded protein contains twelve putative transmembrane domains and is a plasma integral membrane protein.

Distribution

OCT3 is widely distributed in brain tissue. It is not yet completely clear whether its location is primarily neuronal or glial. Areas of the brain in which it has been reported include: hippocampus, retrosplenial cortex, visual cortex, hypothalamus, amygdala, nucleus accumbens, thalamus, raphe nucleus, subiculum, superior and inferior colliculi, and islands of Calleja.

Pharmacology

Organic cation transporter 3 is a polyspecific transporter whose transport is independent of sodium. Known substrates for transport include:

histamine Histamine is an organic nitrogenous compound involved in local immune responses communication, as well as regulating physiological functions in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. Discovered in 19 ...

serotonin Serotonin (), also known as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter with a wide range of functions in both the central nervous system (CNS) and also peripheral tissues. It is involved in mood, cognition, reward, learning, ...

norepinephrine Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic compound, organic chemical in the catecholamine family that functions in the brain and human body, body as a hormone, neurotransmitter and neuromodulator. The ...

dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. It is an amine synthesized ...

and MPP⁺. Capacity for transport and affinity for these substrates may vary between rat and human isoforms however. Transport activity of OCT3 is inhibited by recreational and pharmaceutical drugs, including

MDMA 3,4-Methylenedioxymethamphetamine (MDMA), commonly known as ecstasy (tablet form), and molly (crystal form), is an empathogen–entactogenic drug with stimulant and minor Psychedelic drug, psychedelic properties. In studies, it has been used ...

phencyclidine Phencyclidine or phenylcyclohexyl piperidine (PCP), also known in its use as a street drug as angel dust among other names, is a dissociative anesthetic mainly used recreationally for its significant mind-altering effects. PCP may cause hall ...

(PCP), MK-801,

amphetamine Amphetamine (contracted from Alpha and beta carbon, alpha-methylphenethylamine, methylphenethylamine) is a central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, an ...

methamphetamine Methamphetamine (contracted from ) is a potent central nervous system (CNS) stimulant that is mainly used as a recreational drug use, recreational or Performance-enhancing substance, performance-enhancing drug and less commonly as a secon ...

and

cocaine Cocaine is a tropane alkaloid and central nervous system stimulant, derived primarily from the leaves of two South American coca plants, ''Erythroxylum coca'' and ''Erythroxylum novogranatense, E. novogranatense'', which are cultivated a ...

. Transport is also inhibited by the chemical

decynium-22 Decynium-22 is a cationic derivative of quinoline, and a potent inhibitor of the plasma membrane monoamine transporter (PMAT), as well as all members of the organic cation transporter (OCT) family in both human and rat cells. However, it has lit ...

and physiological concentrations of

corticosterone Corticosterone, also known as 17-deoxycortisol and 11β,21-dihydroxyprogesterone, is a 21-carbon steroid hormone of the corticosteroid type produced in the cortex of the adrenal glands. In the very rare case of congenital adrenal hyperplasia due ...

and

cortisol Cortisol is a steroid hormone in the glucocorticoid class of hormones and a stress hormone. When used as medication, it is known as hydrocortisone. Cortisol is produced in many animals, mainly by the ''zona fasciculata'' of the adrenal corte ...

. K_i values for decynium-22 and corticosterone inhibition of OCT3 transport are respectively 10 and 100 times lower than K_i values of OCT1 and OCT2. This effect of glucocorticoids is believed to explain the phenomenon of stress-induced relapse in recovering addicts, where dopamine transport inhibition causes reactivation of hypersensitive dopamine pathways involved in drug-seeking behavior and incentive salience.

Distribution

Pharmacology

See also

References

Further reading