Centre of Electron Microscopy, University of Lausanne, Bugnon 27, CH-1005 Lausanne, Switzerland.
Biol Cell. 2010 Apr 1;102(6):361-75. doi: 10.1042/BC20090139.
Sphingomyelin is one of the major phospholipids in the cell nucleus. However, its intranuclear distribution with regard to different functional nuclear domains as well as its possible involvement in the nuclear functional architecture remains to be elucidated.
We carried out an ultrastructural cytochemical study of the intranuclear distribution of SM (sphingomyelin) using an in situ binding assay of neutral SMase (sphingomyelinase) conjugated to colloidal gold particles. The enzymatic labelling was carried out on ultrathin sections of different mammalian cells prepared by means of various fixation and resin-embedding protocols. Transmission electron microscopic analysis revealed preferential localization of SM within the PR (perichromatin region), a functionally important nucleoplasmic domain containing sites of pre-mRNA synthesis and processing. In the nucleolus, SM is mostly associated with the dense fibrillar component containing transcriptionally active ribosomal genes. Microinjection of enzymatically active SMase into living cells resulted in a rapid degradation of intranuclear structure.
Our observations, supported by biochemical data, provide evidence for the involvement of SM in important nuclear functions. They bring additional information pointing out the PR as an essential functional nuclear domain. Furthermore, they suggest a role for SM in the internal nuclear architecture.
神经鞘磷脂是细胞核中主要的磷脂之一。然而，其在不同功能核区的核内分布及其在核功能结构中的可能作用仍有待阐明。
我们使用与胶体金颗粒偶联的中性神经鞘磷脂酶（神经鞘磷脂酶）的原位结合测定法，对 SM（神经鞘磷脂）在细胞核内的分布进行了超微结构细胞化学研究。用不同的固定和树脂包埋方案制备的不同哺乳动物细胞的超薄切片进行了酶标记。透射电子显微镜分析显示，SM 优先定位于 PR（染色质周围区）内，PR 是一个功能重要的核质区，包含 pre-mRNA 合成和加工的部位。在核仁中，SM 主要与含有转录活跃核糖体基因的致密纤维成分相关。将具有酶活性的神经鞘磷脂酶微注射到活细胞中，导致核内结构迅速降解。
我们的观察结果得到生化数据的支持，为 SM 参与重要的核功能提供了证据。它们提供了更多的信息，指出 PR 是一个重要的功能核区。此外，它们表明 SM 在核内结构中起作用。
