抄録
Two-dimensional liquid chromatography coupled with tandem mass spectrometry (2D LC-MS/MS) technique has high capability of resolving peptides, and is used for analysis of highly complex protein mixtures. In this report, we used this technique to analyze proteins secreted from human hepatoma cell line, HepG2, and identified over 400 secreted proteins. Recently, liver has been demonstrated to secrete proteins in the same manner as adipocytes which secrete adipocytokines regulating lipid and glucose metabolism. As the hepatic lipid homeostasis is regulated by a cross talk between peroxisome proliferator-activated receptor-alpha and liver X receptor (LXR), both of which are nuclear receptors, we attempted to identify the LXR-regulated proteins secreted from HepG2 cells using the two-dimensional differential in-gel electrophoresis technology (2D-DIGE) followed by the identification of proteins with significantly different expression using LC-MS/MS. We identified one of the upregulated proteins in response to LXR activation as apolipoprotein E. These findings indicate that the combinatorial mass spectrometry-based approach utilizing multi-dimensional chromatography and two-dimensional electrophoresis is useful to identify the target molecules for clinical drugs from complex protein mixtures.
