Formation of siliceous spicules in the marine demosponge Suberites domuncula
Formation of siliceous spicules in the marine demosponge Suberites domuncula
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DOI：
10.1007/s00441-005-1141-5
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发表时间：
2005-08-01
影响因子：
3.6
通讯作者：
Schröder, H
中科院分区：
文献类型：
--
作者：
Müller, WEG;Rothenberger, M;Schröder, H
海绵动物的硅质骨架由骨针构成。本文研究了土生苏合香原变种骨针的形成。扫描电子显微镜和透射电子显微镜（TEM）分析显示，在针状体的中心，一个轴向通道，是0.3-1.6 μ m宽，充满了轴向细丝。这种纤维由合成针状体的酶silicatein组成。透射电镜分析表明，骨针的形成开始于细胞内，结束于细胞外。在初始阶段，轴向管仅由silicatein组成，而膜结构和原纤维（宽度为10-15 nm）随后也可以被识别，这表明细胞内组分突出到轴向管中。针对silicatein的抗体已被应用于Western印迹;在细胞内，silicatein被加工成成熟形式（24 kDa），而在细胞外检测到具有前肽（33 kDa）的酶原。硅酸盐蛋白在五个位点发生磷酸化。免疫组织学分析表明，silicatein存在于轴向管（轴丝）和骨针的表面上，表明它们通过并置生长。最后，我们已经证明，酶反应的silicatein抑制抗silicatein抗体。这些数据首次提供了骨针形成的全面轮廓。
The siliceous skeleton of demosponges is constructed of spicules. We have studied the formation of spicules in primmorphs from Suberites domuncula. Scanning electron microscopy and transmission electron-microscopical (TEM) analyses have revealed, in the center of the spicules, an axial canal that is 0.3-1.6 mu m wide and filled with an axial filament. This filament is composed of the enzyme silicatein, which synthesizes the spicules. TEM analysis has shown that spicule formation starts intracellularly and ends extracellularly in the mesohyl. At the initial stage, the axial canal is composed only of silicatein, whereas membranous structures and fibrils (10-15 nm in width) can later also be identified, suggesting that intracellular components protrude into the axial canal. Antibodies against silicatein have been applied for Western blotting; intracellularly, silicatein is processed to the mature form (24 kDa), whereas the pro-enzyme with the propeptide (33 kDa) is detected extracellularly. Silicatein undergoes phosphorylation at five sites. Immunohistological analysis has shown that silicatein exists in the axial canal (axial filament) and on the surface of the spicules, suggesting that they grow by apposition. Finally, we have demonstrated that the enzymic reaction of silicatein is inhibited by anti-silicatein antibodies. These data provide, for the first time, a comprehensive outline of spicule formation.