Distribution and pharmacology of alanine–serine–cysteine transporter 1 (asc‐1) in rodent brain

Publisher Website
Google Scholar
Abstract
A polyclonal antibody against the Na+‐independent alanine–serine–cysteine transporter 1 (asc‐1) was raised and the specificity of the antibody verified by Western blots performed on membranes prepared from HEK293 cells transiently transfected with the cloned murine asc‐1. The antibody was then used to localize the transporter in the brain of two rodent species by using immunohistochemistry at the light and electron microscopical level. asc‐1‐immunoreactivity (asc‐1‐ir) was widely distributed throughout the mouse and rat brain. Areas with high levels of asc‐1‐ir included hypothalamus, the medial septal area, globus pallidus, entopeduncular nucleus, cingulate and retrosplenial cortices. Moderate asc‐1‐ir was observed in several areas including layers III and V of the neocortex, thalamus, nucleus accumbens, caudate putamen, bed nucleus of stria terminalis, all amygdaloid nuclei, hippocampus (CA1–CA3 and hilus of the dentate gyrus), as well as several brainstem nuclei. asc‐1‐ir was observed as punctuate staining consistent with varicosities matching neuronal cell bodies and dendritic fields. At the ultrastructural level, asc‐1‐ir was mainly confined to presynaptic terminals. Immunostaining in either glial cell bodies or perivascular sites was not observed and white matter was completely devoid of asc‐1‐ir. Furthermore, the pharmacology of the Na+‐independent uptake site for [3H]d‐serine in rat brain synaptosomal P2 fractions was compared with the substrate specificity of the cloned human asc‐1 transporter and a high degree of correlation was demonstrated. We conclude that asc‐1‐ir is widespread in the brain and limited to neuronal structures and that asc‐1 may contribute to synaptic clearance of d‐serine in brain.