Gudeman D M, Brightman M W, Merisko E M, Merril C R
Howard Hughes Medical Institute, National Institutes of Health, Bethesda, Maryland.
J Neurosci Res. 1989 Oct;24(2):184-91. doi: 10.1002/jnr.490240209.
Protein synthesis and secretion by the choroid plexus (CP) has been implicated as a major source of certain proteins in cerebrospinal fluid (CSF), such as transthyretin. The suggestion that proteins are elaborated from CP through apocrine secretion has been borne out by the presence of newly labeled proteins in apical protrusions from CP (Agnew et al.: Cell and Tissue Research 208:261-281, 1980a). When the protrusions (aposomes) separate from the cells, they continue to incorporate labeled amino acids (Gudeman et al.: Tissue and Cell 19:101-109, 1987). In the present work the formation of aposomes in live CP explants indicated that these spheroids were not the result of fixation. Aposomes were also identified within rat CSF by immunohistochemistry with monoclonal directed against aposomes as well as with anti-transthyretin serum. The protein product of aposomes was characterized by 2-dimensional SDS-PAGE and compared to the protein products of whole CP tissue. Paradoxically, transthyretin, a heavily labeled protein in the tissue, was virtually undetected in the aposome synthetic profile. However, four other proteins were expressed in relatively equivalent amounts by the aposomes. The presence of mRNA in aposomes was detected with a poly dT probe, and the presence of actin was revealed by phalloidin staining of aposomes. These studies provide a more comprehensive definition of aposomes, but the functions of their secreted proteins remains to be determined.
脉络丛（CP）的蛋白质合成与分泌被认为是脑脊液（CSF）中某些蛋白质的主要来源，如转甲状腺素蛋白。CP通过顶浆分泌产生蛋白质这一观点已被CP顶端突起中新标记蛋白质的存在所证实（阿格纽等人：《细胞与组织研究》208:261 - 281，1980a）。当这些突起（顶质体）与细胞分离后，它们仍会继续掺入标记氨基酸（古德曼等人：《组织与细胞》19:101 - 109，1987）。在本研究中，活的CP外植体中顶质体的形成表明这些球体并非固定所致。通过针对顶质体的单克隆抗体以及抗转甲状腺素蛋白血清进行免疫组织化学检测，在大鼠脑脊液中也鉴定出了顶质体。顶质体的蛋白质产物通过二维SDS - PAGE进行表征，并与整个CP组织的蛋白质产物进行比较。矛盾的是，转甲状腺素蛋白在组织中是一种高度标记的蛋白质，但在顶质体的合成图谱中几乎未被检测到。然而，其他四种蛋白质在顶质体中的表达量相对相当。用聚dT探针检测顶质体中mRNA的存在，并用鬼笔环肽对顶质体进行染色以显示肌动蛋白的存在。这些研究对顶质体进行了更全面的定义，但其分泌蛋白的功能仍有待确定。
