The serotonin transporter is a monoamine transporter protein. It allows neurons, platelets, and other cells to accumulate the chemical neurotransmitter serotonin, which affects emotions and drives. Neurons communicate by using chemical messages like serotonin between cells. The transporter protein , by recycling serotonin, regulates its concentration in a gap, or synapse, and thus its effects on a receiving neuron’s receptor.

Medical studies have shown that changes in serotonin transporter metabolism appear to be associated with many different phenomena, including alcoholism, clinical depression, obsessive compulsive disorder (OCD) and romantic love.

Pharmacology

Transporters are important sites for agents that treat psychiatric disorders. Drugs that reduce the binding of serotonin to transporters (selective serotonin reuptake inhibitors, or SSRIs) are used to treat mental disorders. About half of patients with OCD are treated with SSRIs. Fluoxetine is an example of a selective serotonin reuptake inhibitor.

Genetics

In humans, the serotonin transporter is encoded by the human serotonin transporter gene (hSERT).

Researchers have found an uncommon mutation in hSERT, in some unrelated families with OCD, that leads to faulty transporter function and regulation. A second variant in the same gene of some patients with this mutation suggests a genetic "double hit," resulting in greater biochemical effects and more severe symptoms.

References

• Norio Ozaki et. al. Serotonin transporter missense mutation associated with a complex neuropsychiatric phenotype. Molecular Psychiatry 2003 Volume 8, number 11, pages 933-936.
• Marazziti D, Akiskal HS, Rossi A, Cassano GB. Alteration of the platelet serotonin transporter in romantic love. Psychol Med. 1999 May;29(3):741-5.
• NIH press release: Serotonin Transporter Gene Shown to Influence College Drinking Habits
• Roiser JP, Cook LJ, Cooper JD, Rubinsztein DC, Sahakian BJ. Association of a Functional Polymorphism in the Serotonin Transporter Gene With Abnormal Emotional Processing in Ecstasy Users. Am J Psychiatry. 2005 Mar;162(3):609-612.

This article is adapted from the public domain NIMH press release at http://www.nimh.nih.gov/events/prmutationa.cfm