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摘要
The transmembrane alpha-amino-3-hydroxy5-methyl-4-isoxazole propionic acid (AMPA) receptor regulatory proteins (TARPs) are a family of auxiliary AMPA receptor subunits that differentially modulate trafficking and many functional properties of the receptor. To investigate which TARP isoforms may be involved in AMPA receptor-mediated spinal synaptic transmission, we have mapped the localization of five of the known TARP isoforms, namely gamma-2 (also known as stargazin), gamma-3, gamma-4, gamma-7 and gamma-8, in the rat spinal cord. Immunoblotting showed expression of all isoforms in the spinal cord to varying degrees. At the light microscopic level, immunoperoxidase labeling of gamma-4, gamma-7 and gamma-8 was found throughout spinal gray matter. In white matter, gamma-4 and gamma-7 immunolabeling was observed in astrocytic processes and in mature oligodendrocytes. In pepsin-treated spinal cord, gamma-7 often colocalized with GluA2 immunopositive puncta in the deep dorsal horn as well as in the ventral horn, but not in the superficial dorsal horn. Postembedding immunogold labeling was further used to assess the synaptic localization of gamma-2, gamma-7 and gamma-8 in the dorsal horn. Synaptic immunogold labeling of gamma-2 was sparse throughout the dorsal horn, with some primary afferent synapses weakly labeled, whereas relatively strong gamma-7 immunogold labeling was found at deep dorsal horn synapses, including at synapses formed by low-threshold mechanosensitive primary afferent terminals. Prominent immunogold labeling of gamma-8 was frequently detected at synapses established by primary afferent fibers. The spinal localization patterns of TARP isoforms reported here suggest that AMPA receptors at spinal synaptic populations and in glial cells may exhibit different functional characteristics owing to differences in auxiliary subunit composition.
- 出版日期2013-9-17
