Glycine Transporter 1 (GLYT1)

Glycine transport is mediated by 2 sodium-dependent carriers, GLYT1 and GLYT2, that have distinct tissue distributions. While the 3-prime sequences of these 2 cDNAs were identical, the 5-prime noncoding regions and the N termini were completely different. GLYT1b was found only in the white matter of the CNS, while GLYT1a was found in the gray matter of the CNS as well as in macrophages and mast cells in peripheral tissues. Tissue-specific alternative splicing or alternative promoter usage from a single gene resulted in 2 mRNA products encoding similar but distinct glycine transporters. The anatomic distribution of GLYT1a mRNA supported the emerging status of glycine as a supraspinal neurotransmitter and suggested that glycine may function as a chemical messenger outside the CNS.