Tavazzani Elisa, Tritto Simona, Spaiardi Paolo, Botta Laura, Manca Marco, Prigioni Ivo, Masetto Sergio, Russo Giancarlo
Department of Brain and Behavioral Sciences, University of Pavia Pavia, Italy.
Department of Brain and Behavioral Sciences, University of Pavia Pavia, Italy ; Laboratory of Neurophysiology, Brain Connectivity Center, C. Mondino National Neurological Institute Pavia, Italy.
Front Cell Neurosci. 2014 Dec 17;8:428. doi: 10.3389/fncel.2014.00428. eCollection 2014.
The function of the enzyme glutamate decarboxylase (GAD) is to convert glutamate in γ-aminobutyric acid (GABA). Glutamate decarboxylase exists as two major isoforms, termed GAD65 and GAD67, that are usually expressed in GABA-containing neurons in the central nervous system. GAD65 has been proposed to be associated with GABA exocytosis whereas GAD67 with GABA metabolism. In the present immunofluorescence study, we have investigated the presence of the two GAD isoforms in the semicircular canal cristae of wild type and GAD67-GFP knock-in mice. While no evidence for GAD65 expression was found, GAD67 was detected in a distinct population of peripherally-located supporting cells, but not in hair cells or in centrally-located supporting cells. GABA, on the other hand, was found in all supporting cells. The present result indicate that only a discrete population of supporting cells use GAD67 to synthesize GABA. This is the first report of a marker that allows to distinguish two populations of supporting cells in the vestibular epithelium. On the other hand, the lack of GABA and GAD enzymes in hair cells excludes its involvement in afferent transmission.
谷氨酸脱羧酶（GAD）的功能是将谷氨酸转化为γ-氨基丁酸（GABA）。谷氨酸脱羧酶以两种主要的同工型存在，即GAD65和GAD67，它们通常在中枢神经系统中含GABA的神经元中表达。有人提出GAD65与GABA胞吐作用有关，而GAD67与GABA代谢有关。在本免疫荧光研究中，我们研究了野生型和GAD67-GFP基因敲入小鼠的半规管嵴中两种GAD同工型的存在情况。虽然未发现GAD65表达的证据，但在一群位于外周的支持细胞中检测到了GAD67，而在毛细胞或位于中枢的支持细胞中未检测到。另一方面，在所有支持细胞中都发现了GABA。目前的结果表明，只有一群离散的支持细胞利用GAD67合成GABA。这是关于一种能够区分前庭上皮中两种支持细胞群体的标志物的首次报道。另一方面，毛细胞中缺乏GABA和GAD酶排除了其参与传入神经传递的可能性。
