Menco B P, Carr V M, Ezeh P I, Liman E R, Yankova M P
Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208-3520, USA.
J Comp Neurol. 2001 Oct 1;438(4):468-89. doi: 10.1002/cne.1329.
Microvilli of vomeronasal organ (VNO) sensory epithelium receptor cells project into the VNO lumen. This lumen is continuous with the outside environment. Therefore, the microvilli are believed to be the subcellular sites of VNO receptor cells that interact with incoming VNO-targeted odors, including pheromones. Candidate molecules, which are implicated in VNO signaling cascades, are shown to be present in VNO receptor cells. However, ultrastructural evidence that such molecules are localized within the microvilli is sparse. The present study provides firm evidence that immunoreactivity for several candidate VNO signaling molecules, notably the G-protein subunits G(ialpha2) and G(oalpha), and the transient receptor potential channel 2 (TRP2), is localized prominently and selectively in VNO receptor cell microvilli. Although G(ialpha2) and G(oalpha) are localized separately in the microvilli of two cell types that are otherwise indistinguishable in their apical and microvillar morphology, the microvilli of both cell types are TRP2(+). VNO topographical distinctions were also apparent. Centrally within the VNO sensory epithelium, the numbers of receptor cells with G(ialpha2)(+) and G(oalpha)(+) microvilli were equal. However, near the sensory/non-sensory border, cells with G(ialpha2)(+) microvilli predominated. Scattered ciliated cells in this transition zone resembled neither VNO nor main olfactory organ (MO) receptor cells and may represent the same ciliated cells as those found in the non-sensory part of the VNO. Thus, this study shows that, analogous to the cilia of MO receptor cells, microvilli of VNO receptor cells are enriched selectively in proteins involved putatively in signal transduction. This provides important support for the role of these molecules in VNO signaling.
犁鼻器（VNO）感觉上皮受体细胞的微绒毛伸入VNO管腔。该管腔与外界环境相通。因此，微绒毛被认为是VNO受体细胞与传入的VNO靶向气味（包括信息素）相互作用的亚细胞位点。参与VNO信号级联反应的候选分子已被证明存在于VNO受体细胞中。然而，关于这些分子定位于微绒毛内的超微结构证据却很少。本研究提供了确凿的证据，表明几种候选VNO信号分子，特别是G蛋白亚基G（αi2）和G（αo）以及瞬时受体电位通道2（TRP2）的免疫反应性显著且选择性地定位于VNO受体细胞的微绒毛中。尽管G（αi2）和G（αo）分别定位于两种细胞类型的微绒毛中，这两种细胞类型在顶端和微绒毛形态上无法区分，但两种细胞类型的微绒毛均为TRP2阳性。VNO的地形差异也很明显。在VNO感觉上皮的中央，具有G（αi2）阳性和G（αo）阳性微绒毛的受体细胞数量相等。然而，在感觉/非感觉边界附近，具有G（αi2）阳性微绒毛的细胞占主导。在这个过渡区中散在的纤毛细胞既不像VNO也不像主嗅觉器官（MO）的受体细胞，可能与在VNO非感觉部分发现的纤毛细胞相同。因此，本研究表明，类似于MO受体细胞的纤毛，VNO受体细胞的微绒毛选择性地富集了可能参与信号转导的蛋白质。这为这些分子在VNO信号传导中的作用提供了重要支持。
