Abstract
Glutamate decarboxylase (GAD) is an enzyme that produces γ-amino butyrate (GABA) from ^<L->glutamate. GAD is expressed as two independent gene products, GAD65 and GAD67. We have found that GAD67 is specifically expressed in the type III taste bud that is the only cell connected to the nerve cells. We also found that GABA is synthesized inside the taste bud and may activate chloride ion channel that can be a candidate for salt receptor. In this study, we have investigated the traffics how the substrate, glutamate, is coming into the taste bud and how the product, GABA, is utilized within the taste bud by using GAD67-GFP knock-in mouse tongue. We have employed immunohistochemical techniques and RT-PCR analyses to demonstrate the presence of glutamate transporter, GABA receptor and GABA transporter. We describe possible role(s) of GAD in the taste signal transduction.
