CULTURED LEPTOMENINGEAL CELLS SECRETE CEREBROSPINAL-FLUID PROTEINS

To extrapolate the function of the leptomeninges, we examined the prof ile of the proteins secreted from the cultured leptomeningeal cells pr epared from 1-2-day-old rats. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the medium conditioned with the cultu red cells, 20-25 differentially distinctive protein bands were noted. Through several chromatographic procedures (Sephadex G-75, Mono Q, and 7C(8)-300), altogether 18 proteins were purified to homogeneity, and the partial amino acid sequence of each protein was determined, Homolo gy search revealed that the major proteins included prostaglandin-D-sy nthase or beta-trace protein, insulin-like growth factor (IGF)-II, IGF -binding protein-2, apolipoprotein E, beta 2-microglobulin, cystatin C , transferrin, peptidyl-prolyl cis-trans isomerase or cyclophilin C, s ecreted protein acidic and rich in cysteine, ubiquitin, lysozyme C, ex tracellular superoxide dismutase, and collagen alpha-1 (III), Most of these proteins are known to be the major brain-derived protein constit uents of CSF and are thought to play important roles in certain biolog ical events in the brain, Considering the morphological features, the present findings suggest the importance of the leptomeninges as an ori gin of such proteins in CSF.