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Functional and immunocytochemical characterization of D‐serine transporters in cortical neuron and astrocyte cultures
Author(s) -
Shao Zongjun,
Kamboj Amit,
Anderson Christopher M.
Publication year - 2009
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.22086
Subject(s) - serine , transporter , nmda receptor , microbiology and biotechnology , astrocyte , extracellular , neuron , immunocytochemistry , glutamate receptor , biochemistry , excitotoxicity , biology , chemistry , receptor , neuroscience , central nervous system , endocrinology , gene , phosphorylation
Abstract D‐serine is an endogenous coagonist of N‐methyl‐D‐aspartate (NMDA) receptors that plays an important role in synaptic function, neuronal development, and excitotoxicity. Mechanisms of D‐serine transport are important in regulation of extracellular D‐serine concentration and therefore of these critical processes. D‐serine can be transported with low affinity through the Na + ‐dependent amino acid transporter termed ASCT2 , whereas high‐affinity D‐serine uptake has been reported through the Na + ‐independent transporter termed asc‐1 . We investigated immunoreactivity for ASCT2 and asc‐1 and D‐serine transport kinetics in cultured cortical neurons and astrocytes to gain insight into how D‐serine transporters regulate CNS D‐serine levels. Both neurons and astrocytes exhibited low‐affinity Na + ‐dependent D‐serine uptake (K T > 1 mM) with broad substrate selectivity that was consistent with uptake through ASCT2. Both neurons and astrocytes also stained positively for ASCT2 in immunocytochemistry studies. Neurons but not astrocytes stained positively for the high‐affinity D‐serine transporter asc‐1, but no evidence of functional asc‐1 could be detected in neurons with conditions that produced such activity in cortical synaptosomes. These data support ASCT2 function in both neuron and astrocyte cultures and identify a discrepancy between observed asc‐1 immunoreactivity and lack of functional asc‐1 activity in neuron cultures. Together these findings further our knowledge of the processes that govern D‐serine regulation. © 2009 Wiley‐Liss, Inc.