Tryptophan Transport in Human Fibroblast Cells—A Functional Characterization
Open Access
- 1 January 2011
- journal article
- research article
- Published by SAGE Publications in International Journal of Tryptophan Research
- Vol. 4, IJTR.S6913-27
- https://doi.org/10.4137/ijtr.s6913
Abstract
There are indications that serotonergic neurotransmission is disturbed in several psychiatric disorders. One explanation may be disturbed transport of tryptophan (precursor for serotonin synthesis) across cell membranes. Human fibroblast cells offer an advantageous model to study the transport of amino acids across cell membranes, since they are easy to propagate and the environmental factors can be controlled. The aim of this study was to functionally characterize tryptophan transport and to identify the main transporters of tryptophan in fibroblast cell lines from healthy controls.Tryptophan kinetic parameters ( Vmaxand Km) at low and high concentrations were measured in fibroblasts using the cluster tray method. Uptake of3H (5)-L-tryptophan at different concentrations in the presence and absence of excess concentrations of inhibitors or combinations of inhibitors of amino acid transporters were also measured. Tryptophan transport at high concentration (0.5 mM) had low affinity and high Vmaxand the LAT1 isoform of system-L was responsible for approximately 40% of the total uptake of tryptophan. In comparison, tryptophan transport at low concentration (50 nM) had higher affinity, lower Vmaxand approximately 80% of tryptophan uptake was transported by system-L with LAT1 as the major isoform. The uptake of tryptophan at the low concentration was mainly sodium (Na+) dependent, while uptake at high substrate concentration was mainly Na+independent. A series of different transporter inhibitors had varying inhibitory effects on tryptophan uptake.This study indicates that tryptophan is transported by multiple transporters that are active at different substrate concentrations in human fibroblast cells. The tryptophan transport trough system-L was mainly facilitated by the LAT1 isoform, at both low and high substrate concentrations of tryptophan.Keywords
This publication has 50 references indexed in Scilit:
- Tryptophan metabolism, from nutrition to potential therapeutic applicationsAmino Acids, 2010
- Abnormal glycosylation of EAAT1 and EAAT2 in prefrontal cortex of elderly patients with schizophreniaSchizophrenia Research, 2010
- A high-affinity, tryptophan-selective amino acid transport system in human macrophagesJournal of Leukocyte Biology, 2006
- Tyrosine transport in fibroblasts from healthy volunteers and patients with schizophreniaNeuroscience Letters, 2006
- Human LAT1, a Subunit of System L Amino Acid Transporter: Molecular Cloning and Transport FunctionBiochemical and Biophysical Research Communications, 1999
- Tyrosine transport in schizophreniaSchizophrenia Research, 1994
- Decreased tyrosine transport in fibroblasts from schizophrenic patientsLife Sciences, 1987
- A Rapid and Sensitive Method for the Quantitation of Microgram Quantities of Protein Utilizing the Principle of Protein-Dye BindingAnalytical Biochemistry, 1976
- A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye bindingAnalytical Biochemistry, 1976
- Transport of dibasic amino acids, cystine, and tryptophan by cultured human fibroblasts: absence of a defect in cystinuria and Hartnup diseaseJCI Insight, 1972