Proteomic Signatures in Neuronal and Glial Cell Models of Niemann-Pick Disease Type C

Niemann-Pick disease type C (NPC) is a lysosomal storage disorder characterized by the accumulation of unesterified cholesterol and glycosphingolipids in the late endosomal/lysosomal system, resulting in region-specific neurodegeneration. While the mechanism through which defective NPC1 protein and thus altered cholesterol transport engenders neurodegeneration is unknown, selective reintroduction of the NPC1 gene in different cell types in the mouse brain can alleviate disease symptoms, suggesting that neuronal and glial cells may play distinct roles in disease mechanisms. Here, in an in vitro NPC model, we evaluate cell-specific changes in the proteome upon treatment with a small-molecule cholesterol-trafficking inhibitor, U18666A, which inhibits NPC1 function across three immortalized cell lines in the central nervous system (CNS): mouse hippocampal neuronal cells (HT-22), mouse microglial cells (SIM-A9), and human hybridized oligodendrocytes (MO3.13). Using nanoliquid chromatography-mass spectrometry (LC-MS) techniques, we observe 21 common proteins upregulated in all U18666A-treated cells. We also note that markers of activated microglia were significantly altered in SIM-A9 microglial cells, whereas cytoskeletal and membrane-related proteins were elevated in MO3.13. In HT-22 hippocampal neuronal cells, we identify protein changes associated with altered glucose metabolism and postulate that ATP-citrate lyase (ACLY), a protein central to multiple biological pathways, might play a role in responding to aberrant cholesterol trafficking and metabolism in NPC.