Davis J G, Burns F R, Navaratnam D, Lee A M, Ichimiya S, Oberholtzer J C, Greene M I
Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104, USA.
Proc Natl Acad Sci U S A. 1997 Jan 21;94(2):707-12. doi: 10.1073/pnas.94.2.707.
A gelatinous otolithic membrane (OM) couples a single calcified otolith to the sensory epithelium in the bluegill sunfish (Lepomis macrochirus) saccule, one of the otolithic organs in the inner ear. Though the OM is an integral part of the anatomic network of endorgan structures that result in vestibular function in the inner ear, the identity of the proteins that make up this sensory accessory membrane in teleosts, or in any vertebrate, is not fully known. Previously, we identified a cDNA from the sunfish saccular otolithic organ that encoded a new member of the collagen family of structural proteins. In this study, we examined biochemical features and the localization of the saccular collagen (SC) protein in vivo using polyclonal antisera that recognize the noncollagenous domains of the SC protein. The SC protein, in vivo, was identified as a 95-kDa glycoprotein in sunfish whole-saccule lysate and in homogenates of microdissected saccular OMs. Immunohistochemical analyses demonstrated that the SC protein was localized within one of the two distinct layers of the sunfish saccular OM. The SC protein was also detected within the cytoplasm of supporting cells at the edges of the saccular sensory epithelium, indicating that these cells are a primary site for the synthesis of this structural protein. Further studies of the organization of this matrix molecule in the OM may help clarify the role of this sensory accessory membrane in vestibular sensory function.
凝胶状耳石膜（OM）将单个钙化耳石与蓝鳃太阳鱼（Lepomis macrochirus）球囊（内耳中的耳石器官之一）中的感觉上皮相连。尽管OM是内耳中导致前庭功能的终器结构解剖网络的一个组成部分，但构成硬骨鱼或任何脊椎动物中这种感觉附属膜的蛋白质的身份尚不完全清楚。此前，我们从太阳鱼球囊耳石器官中鉴定出一个cDNA，它编码一种结构蛋白胶原家族的新成员。在本研究中，我们使用识别SC蛋白非胶原结构域的多克隆抗血清，检测了体内球囊胶原蛋白（SC）的生化特性和定位。在太阳鱼全球囊裂解物和显微解剖的球囊OM匀浆中，SC蛋白在体内被鉴定为一种95 kDa的糖蛋白。免疫组织化学分析表明，SC蛋白定位于太阳鱼球囊OM的两个不同层之一内。在球囊感觉上皮边缘的支持细胞胞质内也检测到了SC蛋白，这表明这些细胞是这种结构蛋白合成的主要场所。对OM中这种基质分子组织的进一步研究可能有助于阐明这种感觉附属膜在前庭感觉功能中的作用。
