High affinity D- and L-serine transporter Asc-1: cloning and dendritic localization in the rat cerebral and cerebellar cortices

System asc transporter Asc-1, expressed in the brain, transports D- and L-serine with high affinity. To determine the localization of Asc-1 in the rat brain, we isolated a cDNA for the rat orthologue of Asc-1. The encoded protein designated as rAsc-1 (rat Asc-1) exhibited 98% sequence identity to mouse Asc-1 (mAsc-1). Based on amino acid sequences of rAsc-1 and mAsc-1, twopolyclonal antibodies against Asc-1 were generated and used for the immunohistochemical analysis on the cerebral and cerebellar cortices of rats and mice. Asc-1 immunoreactivity was detected in neurons, including cerebellar Purkinje neurons and pyramidal neurons in the neocortex and hippocampus. It was clearly localized in dendrites as well as somata. The localization of Asc-1 in brain suggests the significant contribution of Asc-1 to amino acid mobilization in brains including the synaptic clearance of D-serine and the neuronal uptake of L-serine that is essential for survival and dendrite growth of Purkinje neurons in particular. (C) 2004 Elsevier Ireland Ltd. All rights reserved.