Vesicular Inhibitory Amino Acid Transporter (VIAAT), also known as VGAT and SLC32A1, is a member of the amino acid/polyamine transporter 2 family of proteins. Human VIAAT/SLC32A1 is a 525 amino acid (aa) 10-transmembrane, nonglycosylated protein with a predicted molecular weight of 56-58 kDa. Its N-terminus (aa 1-133) and C-terminus (aa 511-525) are cytoplasmic. There is a 52 kDa short form of VIAAT/SLC32A1 that is not well characterized. Over aa 2-133, human VIAAT/SLC32A1 shares 95% aa identity with the mouse ortholog.
VIAAT/SLC32A1 is expressed in inhibitory neurons throughout the central nervous system, in both resting and activated lymphocytes, and in rodent pancreatic alpha-cells. VIAAT/SLC32A1 is believed to transport both GABA and glycine across synaptic vesicle membranes in an electrical and pH gradient-dependent manner. Once transported, these neurotransmitters are released at the presynaptic membrane, acting as inhibitory factors in the mature nervous system, and excitatory factors in the immature nervous system.