Vesicular glutamate transporter 3 expression identifies glutamatergic amacrine cells in the rodent retina
Vesicular glutamate transporter 3 expression identifies glutamatergic amacrine cells in the rodent retina
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DOI：
10.1002/cne.20250
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发表时间：
2004-09-27
影响因子：
2.5
通讯作者：
Copenhagen, DR
中科院分区：
文献类型：
--
作者：
Johnson, J;Sherry, DM;Copenhagen, DR
谷氨酸能神经元的突触传递需要谷氨酸囊泡转运蛋白（VGLUTs）将胞质谷氨酸浓缩到突触囊泡中。在视网膜中，谷氨酸能感光细胞和双极细胞只表达VGLUT1亚型，而神经节细胞表达VGLUT2亚型。令人惊讶的是，最近发现的VGLUT3异构体在假定的无分泌细胞中被发现，通常被认为是抑制性中间神经元。为了研究VGLUT3细胞的突触机制和可能的次级神经递质组成，并确定其潜在的功能作用，我们进一步研究了这些假定的谷氨酸能无突细胞在成年和发育中的啮齿动物视网膜中的作用。逆转录- pcr证实VGLUT3在小鼠视网膜中的表达。VGLUT3细胞未对神经节或双极细胞标记物进行免疫染色，证明它们是无突细胞。VGLUT3与突触囊泡标记物共定位，电镜显示VGLUT3免疫染色突触囊泡。VGLUT3细胞对无分泌细胞标记物-氨基丁酸、胆碱乙酰转移酶、calretinin或酪氨酸羟化酶没有免疫反应，尽管它们对甘氨酸有免疫染色。VGLUT3过程与神经节细胞树突产生突触接触，提示输入到这些细胞。VGLUT3免疫染色与代谢性谷氨酸受体4密切相关，这与这些细胞的谷氨酸能突触胞吐一致。在成熟的小鼠视网膜中，Western blot显示VGLUT3在出生后7/8天（P7/8）表达。在P8时首次观察到视网膜切片的VGLUT3免疫染色，在P12时达到成人模式。因此，VGLUT3的功能与vglut1介导的双极细胞的谷氨酸能传递大约同时开始。此外，VGLUT3细胞的一个子集表达生物钟基因周期1，暗示VGLUT3细胞是基于视网膜的可携带光的昼夜节律系统的一部分。
Synaptic transmission from glutamatergic neurons requires vesicular glutamate transporters (VGLUTs) to concentrate cytosolic glutamate in synaptic vesicles. In retina, glutamatergic photoreceptors and bipolar cells exclusively express the VGLUT1 isoform, whereas ganglion cells express VGLUT2. Surprisingly, the recently identified VGLUT3 isoform was found in presumed amacrine cells, generally considered to be inhibitory interneurons. To investigate the synaptic machinery and conceivable secondary neurotransmitter composition of VGLUT3 cells, and to determine a potential functional role, we further investigated these putative glutamatergic amacrine cells in adult and developing rodent retina. Reverse transcriptase-PCR substantiated VGLUT3 expression in mouse retina. VGLUT3 cells did not immunostain for ganglion or bipolar cell markers, providing evidence that they are amacrine cells. VGLUT3 colocalized with synaptic vesicle markers, and electron microscopy showed that VGLUT3 immunostained synaptic vesicles. VGLUT3 cells were not immunoreactive for amacrine cell markers gamma-aminobutyric acid, choline acetyltransferase, calretinin, or tyrosine hydroxylase, although they immunostain for glycine. VGLUT3 processes made synaptic contact with ganglion cell dendrites, suggesting input onto these cells. VGLUT3 immunostaining was closely associated with the metabotropic glutamate receptor 4, which is consistent with glutamatergic synaptic exocytosis by these cells. In the maturing mouse retina, Western blots showed VGLUT3 expression at postnatal day 7/8 (P7/8). VGLUT3 immunostaining in retinal sections was first observed at P8, achieving an adult pattern at P12. Thus, VGLUT3 function commences around the same time as VGLUT1-mediated glutamatergic transmission from bipolar cells. Furthermore, a subset of VGLUT3 cells expressed the circadian clock gene period 1, implicating VGLUT3 cells as part of the light-entrainable retina-based circadian system.