Bragina L, Candiracci C, Barbaresi P, Giovedì S, Benfenati F, Conti F
Department of Neuroscience, Università Politecnica delle Marche, Via Tronto 10/A, Torrette di Ancona, I-60020, Ancona, Italy.
Neuroscience. 2007 Jun 8;146(4):1829-40. doi: 10.1016/j.neuroscience.2007.02.060. Epub 2007 Apr 19.
We investigated whether cortical glutamatergic and GABAergic release machineries can be differentiated on the basis of the proteins they express, by studying the degree of co-localization of synapsin (SYN) I and II, synaptophysin (SYP) I and II, synaptosomal-associated protein (SNAP)-25 and SNAP-23 in vesicular glutamate transporter (VGLUT) 1-, VGLUT2- and vesicular GABA transporter (VGAT)-positive (+) puncta in the rat cerebral cortex. Co-localization studies showed that SYNI and II were expressed in approximately 90% of VGLUT1+, approximately 30% of VGLUT2+ and 30-50% of VGAT+ puncta; SYPI was expressed in approximately 95% of VGLUT1+, 30% of VGLUT2+, and 45% of VGAT+ puncta; SYPII in approximately 7% of VGLUT1+, 3% of VGLUT2+, and 20% of VGAT+ puncta; SNAP-25 in approximately 94% of VGLUT1+, 5% of VGLUT2+, and 1% of VGAT+ puncta, and SNAP-23 in approximately 3% of VGLUT1+, 86% of VGLUT2+, and 22% of VGAT+ puncta. Since SYPI, which is considered ubiquitous, was expressed in about half of GABAergic axon terminals, we studied its localization electron microscopically and in immunoisolated synaptic vesicles: these studies showed that approximately 30% of axon terminals forming symmetric synapses were SYPI-negative, and that immunoisolated VGAT-positive synaptic vesicles were relatively depleted of SYPI as compared with VGLUT1+ vesicles. Overall, the present investigation shows that in the cerebral cortex of rats distinct presynaptic proteins involved in neurotransmitter release are differentially expressed in GABAergic and in the two major types of glutamatergic axon terminals in the cerebral cortex of rats.
我们通过研究大鼠大脑皮层中囊泡谷氨酸转运体（VGLUT）1、VGLUT2和囊泡GABA转运体（VGAT）阳性（+）小点中突触素（SYN）I和II、突触小泡蛋白（SYP）I和II、突触体相关蛋白（SNAP）-25和SNAP-23的共定位程度，来探究皮层谷氨酸能和GABA能释放机制是否可以根据它们所表达的蛋白质进行区分。共定位研究表明，SYNI和II在约90%的VGLUT1+、约30%的VGLUT2+和30 - 50%的VGAT+小点中表达；SYPI在约95%的VGLUT1+、30%的VGLUT2+和45%的VGAT+小点中表达；SYPII在约7%的VGLUT1+、3%的VGLUT2+和20%的VGAT+小点中表达；SNAP - 25在约94%的VGLUT1+、5%的VGLUT2+和1%的VGAT+小点中表达，而SNAP - 23在约3%的VGLUT1+、86%的VGLUT2+和22%的VGAT+小点中表达。由于被认为普遍存在的SYPI在约一半的GABA能轴突终末中表达，我们通过电子显微镜和免疫分离突触小泡研究了其定位：这些研究表明，形成对称突触的轴突终末中约30%为SYPI阴性，并且与VGLUT1+小泡相比，免疫分离的VGAT阳性突触小泡中SYPI相对缺乏。总体而言，本研究表明，在大鼠大脑皮层中，参与神经递质释放的不同突触前蛋白在GABA能以及大鼠大脑皮层中两种主要类型的谷氨酸能轴突终末中差异表达。
