Akil Omar, Chang Jolie, Hiel Hakim, Kong Jee-Hyun, Yi Eunyoung, Glowatzki Elisabeth, Lustig Lawrence R
Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco, San Francisco, California 94143-0449, USA.
J Neurosci. 2006 Dec 13;26(50):13076-88. doi: 10.1523/JNEUROSCI.3746-06.2006.
After a yeast two-hybrid screen identified prosaposin as a potential interacting protein with the nicotinic acetylcholine receptor (nAChR) subunit alpha10, studies were performed to characterize prosaposin in the normal rodent inner ear. Prosaposin demonstrates diffuse organ of Corti expression at birth, with gradual localization to the inner hair cells (IHCs) and its supporting cells, inner pillar cells, and synaptic region of the outer hair cells (OHCs) and Deiters' cells (DCs) by postnatal day 21 (P21). Microdissected OHC and DC quantitative reverse transcriptase-PCR and immunohistology localizes prosaposin mRNA to DCs and OHCs, and protein predominantly to the apex of the DCs. Subsequent studies in a prosaposin knock-out (KO) (-/-) mouse showed intact but slightly reduced hearing through P19, but deafness by P25 and reduced distortion product otoacoustic emissions from P15 onward. Beginning at P12, the prosaposin KO mice showed histologic organ of Corti changes including cellular hypertrophy in the region of the IHC and greater epithelial ridge, a loss of OHCs from cochlear apex, and vacuolization of OHCs. Immunofluorescence revealed exuberant overgrowth of auditory afferent neurites in the region of the IHCs and proliferation of auditory efferent neurites in the region of the tunnel of Corti. IHC recordings from these KO mice showed normal I-V curves and responses to applied acetylcholine. Together, these results suggest that prosaposin helps maintain normal innervation patterns to the organ of Corti. Furthermore, prosaposin's overlapping developmental expression pattern and binding capacity toward the nAChR alpha10 suggest that alpha10 may also play a role in this function.
在酵母双杂交筛选确定了 prosaposin 是一种与烟碱型乙酰胆碱受体（nAChR）α10 亚基潜在相互作用的蛋白后，开展了相关研究以表征正常啮齿动物内耳中的 prosaposin。出生时，prosaposin 在柯蒂氏器中呈弥漫性表达，到出生后第 21 天（P21）逐渐定位于内毛细胞（IHC）及其支持细胞、内柱细胞，以及外毛细胞（OHC）和Dieters 细胞（DC）的突触区域。显微解剖的 OHC 和 DC 的定量逆转录聚合酶链反应及免疫组织学研究将 prosaposin mRNA 定位于 DC 和 OHC，而蛋白主要定位于 DC 的顶端。随后在 prosaposin 基因敲除（KO）（-/-）小鼠中的研究表明，在 P19 之前听力完整但略有下降，但到 P25 时出现耳聋，且从 P15 起畸变产物耳声发射减少。从 P12 开始，prosaposin KO 小鼠的柯蒂氏器出现组织学变化，包括 IHC 区域和较大上皮嵴处的细胞肥大、耳蜗顶端 OHC 的丢失以及 OHC 的空泡化。免疫荧光显示 IHC 区域听觉传入神经突过度生长，以及柯蒂氏管区域听觉传出神经突增殖。这些 KO 小鼠的 IHC 记录显示 I-V 曲线正常且对施加的乙酰胆碱有反应。总之，这些结果表明 prosaposin 有助于维持柯蒂氏器的正常神经支配模式。此外，prosaposin 重叠的发育表达模式及其与 nAChR α10 的结合能力表明，α10 可能也在该功能中发挥作用。
