Wekesa K S, Anholt R R
Department of Zoology, Box 7617, North Carolina State University, Raleigh, NC 27695-7617, USA.
Brain Res. 1999 Aug 7;837(1-2):117-26. doi: 10.1016/s0006-8993(99)01630-3.
Transmembrane signaling events at the dendrites and axons of olfactory receptor neurons mediate distinct functions. Whereas odorant recognition and chemosensory transduction occur at the dendritic membranes of olfactory neurons, signal propagation, axon sorting and target innervation are functions of their axons. The roles of G proteins in transmembrane signaling at the dendrites have been studied extensively, but axonal G proteins have not been investigated in detail. We used immunohistochemistry to visualize expression of alpha subunits of G(o) and G(i2) in the mouse olfactory system. G(o) is expressed ubiquitously on axons of olfactory receptor neurons throughout the olfactory neuroepithelium and in virtually all glomeruli in the main olfactory bulb. In contrast, expression of G(i2) is restricted to a sub-population of olfactory neurons, along the dorsal septum and the dorsal recess of the nasal cavity, which projects primarily to medial regions of the olfactory bulb, with the exception of glomeruli adjacent to the pathway of the vomeronasal nerve. In contrast to the overlapping expression patterns of G(o) and G(i2) in the main olfactory system, neurons expressing G(o) and those expressing G(i2) in the accessory olfactory bulb are more clearly separated, in agreement with previous studies. Vomeronasal axons terminating in glomeruli in the rostral region of the accessory olfactory bulb express G(i2), whereas those projecting to the caudal region express G(o). Characterization of the expression patterns of G(i2) and G(o) in the olfactory projection is essential for future studies aimed at relating transmembrane signaling events to signal propagation, axon sorting and target innervation.
嗅觉受体神经元树突和轴突上的跨膜信号传导事件介导不同的功能。气味识别和化学感觉转导发生在嗅觉神经元的树突膜上，而信号传播、轴突分选和靶标支配则是其轴突的功能。G蛋白在树突跨膜信号传导中的作用已得到广泛研究，但轴突G蛋白尚未得到详细研究。我们使用免疫组织化学方法来观察G(o)和G(i2)的α亚基在小鼠嗅觉系统中的表达情况。G(o)在整个嗅觉神经上皮的嗅觉受体神经元轴突上以及主嗅球的几乎所有肾小球中普遍表达。相比之下，G(i2)的表达仅限于嗅觉神经元的一个亚群，沿着鼻中隔和鼻腔背侧隐窝分布，这些神经元主要投射到嗅球的内侧区域，但不包括与犁鼻神经通路相邻的肾小球。与G(o)和G(i2)在主嗅觉系统中的重叠表达模式不同，副嗅球中表达G(o)的神经元和表达G(i2)的神经元分布更为清晰，这与之前的研究一致。终止于副嗅球前部区域肾小球的犁鼻轴突表达G(i2)，而投射到后部区域的轴突则表达G(o)。表征G(i2)和G(o)在嗅觉投射中的表达模式对于未来旨在将跨膜信号传导事件与信号传播、轴突分选和靶标支配联系起来的研究至关重要。
