Department of Biological, Chemical and Physical Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA.
BMC Neurosci. 2010 Aug 27;11:108. doi: 10.1186/1471-2202-11-108.
One of the fundamental questions in olfaction is whether olfactory receptor neurons (ORNs) behave as independent entities within the olfactory epithelium. On the basis that mature ORNs express multiple connexins, I postulated that gap junctional communication modulates olfactory responses in the periphery and that disruption of gap junctions in ORNs reduces olfactory sensitivity. The data collected from characterizing connexin 43 (Cx43) dominant negative transgenic mice OlfDNCX, and from calcium imaging of wild type mice (WT) support my hypothesis.
I generated OlfDNCX mice that express a dominant negative Cx43 protein, Cx43/β-gal, in mature ORNs to inactivate gap junctions and hemichannels composed of Cx43 or other structurally related connexins. Characterization of OlfDNCX revealed that Cx43/β-gal was exclusively expressed in areas where mature ORNs resided. Real time quantitative PCR indicated that cellular machineries of OlfDNCX were normal in comparison to WT. Electroolfactogram recordings showed decreased olfactory responses to octaldehyde, heptaldehyde and acetyl acetate in OlfDNCX compared to WT. Octaldehyde-elicited glomerular activity in the olfactory bulb, measured according to odor-elicited c-fos mRNA upregulation in juxtaglomerular cells, was confined to smaller areas of the glomerular layer in OlfDNCX compared to WT. In WT mice, octaldehyde sensitive neurons exhibited reduced response magnitudes after application of gap junction uncoupling reagents and the effects were specific to subsets of neurons.
My study has demonstrated that altered assembly of Cx43 or structurally related connexins in ORNs modulates olfactory responses and changes olfactory activation maps in the olfactory bulb. Furthermore, pharmacologically uncoupling of gap junctions reduces olfactory activity in subsets of ORNs. These data suggest that gap junctional communication or hemichannel activity plays a critical role in maintaining olfactory sensitivity and odor perception.
嗅觉的一个基本问题是嗅觉受体神经元（ORNs）是否在嗅上皮内作为独立实体发挥作用。基于成熟的 ORNs 表达多种连接蛋白，我推测缝隙连接通讯调节外周的嗅觉反应，并且 ORNs 中的缝隙连接中断会降低嗅觉敏感性。从特征化连接蛋白 43（Cx43）显性负性转基因小鼠 OlfDNCX 中收集的数据，以及从野生型（WT）小鼠的钙成像中收集的数据支持我的假说。
我生成了 OlfDNCX 小鼠，该小鼠在成熟的 ORNs 中表达一种显性负性 Cx43 蛋白 Cx43/β-gal，以失活由 Cx43 或其他结构相关连接蛋白组成的缝隙连接和半通道。OlfDNCX 的特征表明，Cx43/β-gal 仅在成熟 ORNs 所在的区域表达。实时定量 PCR 表明，与 WT 相比，OlfDNCX 的细胞机制正常。电嗅觉图记录显示，与 WT 相比，OlfDNCX 对辛醛、庚醛和乙酸乙酯的嗅觉反应降低。根据嗅球中近球细胞气味诱导的 c-fos mRNA 上调来测量的嗅球中辛醛诱发的肾小球活性，在 OlfDNCX 中局限于肾小球层的较小区域，与 WT 相比。在 WT 小鼠中，应用缝隙连接去耦试剂后，对辛醛敏感的神经元的反应幅度减小，并且这种效应是神经元亚群特异性的。
我的研究表明，ORNs 中 Cx43 或结构相关连接蛋白的组装改变调节嗅觉反应，并改变嗅球中的嗅觉激活图。此外，缝隙连接的药理学去耦降低了 ORNs 亚群中的嗅觉活性。这些数据表明，缝隙连接通讯或半通道活性在维持嗅觉敏感性和气味感知中起着关键作用。
