Synaptosomal plasma membrane transport of excitatory sulphur amino acid transmitter candidates: Kinetic characterisation and analysis of carrier specificity
Article first published online: 11 OCT 2004
Copyright © 1992 Wiley-Liss, Inc.
Journal of Neuroscience Research
Volume 32, Issue 1, pages 60–68, May 1992
How to Cite
Grieve, A., Butcher, S. P. and Griffiths, R. (1992), Synaptosomal plasma membrane transport of excitatory sulphur amino acid transmitter candidates: Kinetic characterisation and analysis of carrier specificity. J. Neurosci. Res., 32: 60–68. doi: 10.1002/jnr.490320108
- Issue published online: 11 OCT 2004
- Article first published online: 11 OCT 2004
- Manuscript Accepted: 4 DEC 1991
- Manuscript Revised: 13 NOV 1991
- Manuscript Received: 3 SEP 1991
- transport kinetics;
- synaptosomal fractions;
- HPLC analysis
The transport kinetics of the excitatory sulphur-containing amino acid (SAA) transmitter candidates, L-cysteine sulphinate (L-CSA), L-cysteate (L-CA), L-homocysteine sulphinate (L-HCSA), and L-homocysteate (L-HCA), together with their plasma membrane carrier specificity, was studied in cerebrocortical synaptosome fractions by a sensitive high performance liquid chromatographic assay. A high affinity uptake system could be demonstrated for L-CSA (Km =; 57 ± 6 μM; Vmax =; 1.2 ± 0.1 nmol/min/mg protein) and L-CA (Km =; 23 ± 3 μM; Vmax =; 3.6 ± 0.1 nmol/min/mg protein), whereas L-HCSA (Km =; 502 ± 152 μM; Vmax =; 6.1 ± 1.3 nmol/min/mg protein) and L-HCA (Km =; 1550 ± 169 μM; Vmax =; 10.3 ± 1.1 nmol/min/mg protein) exhibited much lower affinity as transport substrates. In all cases, only a single, saturable Na+-dependent component of uptake could be identified, co-existing with a non-saturable, Na+-independent influx component. Plasma membrane carrier specificity of the SAAs was established following comparison with other high-affinity neurotransmitter systems. High-affinity L-CSA and L-CA transport and low-affinity L-HCSA and L-HCA transport demonstrate strong positive correlations in inhibition profiles when compared against each other or individually against the high-affinity transport of L-[3H]glutamate, L-[3H]aspartate, or D-[3H]aspartate. Moreover, the transport systems for the excitatory SAAs exhibited a negative correlation when compared in inhibition profiles with the high affinity transport of both [3H] γ-aminobutyric acid (GABA) and [3H]taurine. Taken together, these results strongly suggest that L-CSA, L-CA, L-HCSA, and L-HCA share a common synaptosomal plasma membrane transport system with L-glutamate, L-aspartate, and D-aspartate. © 1992 Wiley-Liss, Inc.