Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, Chiba University, Chuo-ku, Chiba, Japan.
J Cell Physiol. 2020 Mar;235(3):2300-2309. doi: 10.1002/jcp.29137. Epub 2019 Sep 6.
Niemann-Pick disease type C (NPC) is a genetic disorder in which patient cells have endosomal/lysosomal accumulation of cholesterol and sphingolipids. However, the relationship between sphingolipids and cholesterol accumulation in NPC cells has not been established. Here, we investigated the role of sphingomyelin (SM) on the accumulation of cholesterol in NPC cells. Reduction of SM by inhibition of the ceramide transfer protein CERT decreased the cholesterol accumulation in NPC cells. The accumulation of SM in NPC cells inhibited the transport of cholesterol to the endoplasmic reticulum. Overexpression of Rab9 in NPC cells reduced the cholesterol accumulation, which was recovered by treatment with SM. In NPC cells that overexpressed a Rab9 constitutively active mutant, SM treatment did not lead to the cholesterol accumulation. These results indicate that SM negatively regulates the Rab9-dependent vesicular trafficking of cholesterol, and a reduction in SM levels in NPC cells recovers the Rab9-dependent vesicular trafficking defect.
尼曼-匹克病 C 型(NPC)是一种遗传性疾病,患者细胞的内体/溶酶体中胆固醇和鞘脂积累。然而,NPC 细胞中鞘脂和胆固醇积累之间的关系尚未确定。在这里,我们研究了鞘磷脂(SM)在 NPC 细胞中胆固醇积累中的作用。通过抑制神经酰胺转移蛋白 CERT 减少 SM,可降低 NPC 细胞中的胆固醇积累。SM 在 NPC 细胞中的积累抑制了胆固醇向内质网的运输。在 NPC 细胞中过表达 Rab9 可减少胆固醇积累,用 SM 处理可恢复这种积累。在过表达 Rab9 组成性激活突变的 NPC 细胞中,SM 处理不会导致胆固醇积累。这些结果表明,SM 负调控 Rab9 依赖性胆固醇囊泡运输,而 NPC 细胞中 SM 水平的降低可恢复 Rab9 依赖性囊泡运输缺陷。