Choroid plexus (CP), the main production site of cerebrospinal fluid (CSF), is responsible for the inflammatory mediators involved in meningitis and immune systems. The mouse choroid plexus cell line ECPC-4 is known to be useful for analyses of CP functions. In this study, we performed the secretome analysis of ECPC-4 using twodimensional gel electrophoresis (2DE) followed by mass spectrometry. Twenty-two secreted proteins were identified in the conditioned medium of ECPC-4. They were a secreted protein acidic and rich in cysteine (SPARC), plasminogen activator inhibitor 1 (PAI-1), and others (vinculin, heat shock protein cognate 71 kDa, moesin, tubulin ß2A, fascin, calreticulin, gamma actin, alcohol dehydrogenase, malate dehydrogenase, Rho GDP dissociation inhibitor alpha, phosphoglyceratemutase 1, translationally controlled tumor protein, phosphatidylethanolamine binding protein1, peroxiredoxin1 type II, peroxiredoxin1, myosin light polypeptide 6, cofilin-1, nucleoside diphosphate kinase A, peptidyl-prolyl cis-trans isomerase A [PPI-A], and galectin1). These proteins could be classified as cytoskeleton/ intermediate filament, protein folding, signal transduction, cell growth, metabolism, and redox regulation groups, suggesting that they could be related to the CP functions. Furthermore, the level of four proteins was changed in the conditioned medium of ECPC-4 treated with lipid A. Proteasome subunit alpha type-1 and nucleoside diphosphate kinase A were significantly increased and gamma-actin and galectin-1 were significantly decreased, as compared with those in the conditioned medium of non-treated ECPC-4. Also, Western Blotting also validated the changes in proteasome subunit alpha type-1, galectin-1 and nucleoside diphosphate kinase A. Thus, it is suggested that these proteins play an important role in inflammation such as meningitis. ECPC-4, like CP epithelial cells, is useful to analyze the CP functions.
