* Dept of Chemistry and $ Dept of
Veterinary & Biomedical Sciences, Pennsylvania State
University, University Park, PA, # Laboratory of Clinical Science,
National Institute of Mental Health, Bethesda, MD
The
serotonin neurotransmitter system is a vital regulator of mood,
anxiety, cognition, motor activity, and addictive behaviors. The
serotonin transporter (SERT), a presynaptic 12 transmembrane domain
Na+/Cl--dependent transporter, is the principal target of the most
widely used anti-anxiety and antidepressant medications, as well as
many drugs of abuse. The SERT gene-linked polymorphic region (5-HTTLPR)
is comprised of a 43 bp “indel” in the gene
promoter that influences the expression of SERT such that the short or
“S” allele drives lower SERT expression compared to
the long “L” allele. Individuals expressing S/L or
S/S genotypes show increased anxiety-related personality traits,
particularly neuroticism compared to individuals expressing the L/L
genotype. We hypothesize that subtle but measurable variations in 5-HT
transporter function exist between the S/S and S/L groups that have not
been explored until now. In the present study, we determined 5-HT
uptake rates in cultured human lymphoblasts, which express the same
SERT gene as that in brain. We utilized high-speed chronoamperometry, a
highly sensitive microelectrode voltammetry method that has a single
second temporal resolution. We have previously demonstrated that using
this technique, we can detect modest decreases in Vmax (and measure Km)
in brain synaptosomes prepared from mice lacking one intact copy of the
SERT gene versus wildtype mice that are not detectable by radiochemical
methods. In the present study, we have been able to differentiate
uptake rates on the order of 50% between the S/S and L/L genotypes in
lymphoblasts. We are currently investigating uptake rates in S/L
expressing lymphoblasts, as well as examining the effects of other SERT
polymorphisms including the rs25531 single nucleotide polymorphism and
the VNTR (STin repeats). Additionally, we are investigating rarer point
mutations including a gain-of-function isoleucine to valine mutation
(I425V) in the SERT coding region that has been investigated only in
transfected non-neuronal cells and is associated with a severe cluster
of psychiatric disorders that includes obsessive compulsive disorder.
The
serotonin neurotransmitter system is a vital regulator of mood,
anxiety, cognition, motor activity, and addictive behaviors. The
serotonin transporter (SERT), a presynaptic 12 transmembrane domain
Na+/Cl--dependent transporter, is the principal target of the most
widely used anti-anxiety and antidepressant medications, as well as
many drugs of abuse. The SERT gene-linked polymorphic region (5-HTTLPR)
is comprised of a 43 bp “indel” in the gene
promoter that influences the expression of SERT such that the short or
“S” allele drives lower SERT expression compared to
the long “L” allele. Individuals expressing S/L or
S/S genotypes show increased anxiety-related personality traits,
particularly neuroticism compared to individuals expressing the L/L
genotype. We hypothesize that subtle but measurable variations in 5-HT
transporter function exist between the S/S and S/L groups that have not
been explored until now. In the present study, we determined 5-HT
uptake rates in cultured human lymphoblasts, which express the same
SERT gene as that in brain. We utilized high-speed chronoamperometry, a
highly sensitive microelectrode voltammetry method that has a single
second temporal resolution. We have previously demonstrated that using
this technique, we can detect modest decreases in Vmax (and measure Km)
in brain synaptosomes prepared from mice lacking one intact copy of the
SERT gene versus wildtype mice that are not detectable by radiochemical
methods. In the present study, we have been able to differentiate
uptake rates on the order of 50% between the S/S and L/L genotypes in
lymphoblasts. We are currently investigating uptake rates in S/L
expressing lymphoblasts, as well as examining the effects of other SERT
polymorphisms including the rs25531 single nucleotide polymorphism and
the VNTR (STin repeats). Additionally, we are investigating rarer point
mutations including a gain-of-function isoleucine to valine mutation
(I425V) in the SERT coding region that has been investigated only in
transfected non-neuronal cells and is associated with a severe cluster
of psychiatric disorders that includes obsessive compulsive disorder.
