Standard-flow LC and thermal focusing ESI elucidates altered liver proteins in late stage Niemann-Pick, type C1 disease.

Aim: Mass spectrometry (MS)-based proteomics, particularly with the development of nano-ESI, have been invaluable to our understanding of altered proteins related to human disease. Niemann-Pick, type C1 (NPC1) disease is a fatal, autosomal recessive, neurodegenerative disorder. The resulting defects include unesterified cholesterol and sphingolipids accumulation in the late endosomal/lysosomal system resulting in organ dysfunction including liver disease. Materials & methods: First, we performed MS analysis of a complex mammalian proteome using both nano- and standard-flow ESI with the intent of developing a differential proteomics platform using standard-flow ESI. Next, we measured the differential liver proteome in the NPC1 mouse model via label-free quantitative MS using standard-flow ESI. Results: Using the standard-flow ESI approach, we found altered protein levels including, increased Limp2 and Rab7a in liver tissue of  Npc1 ^-/- compared to control mice. Conclusion: Standard-flow ESI can be a tool for quantitative proteomic studies when sample amount is not limited. Using this method, we have identified new protein markers of NPC1.