Two-dimensional gel analysis of proteins in cell lines from the central nervous system of larval Drosophila.

High resolution two-dimensional gel electrophoresis was used to quantitatively analyze the patterns of protein synthesis in three different clones of a nerve cell line (ML-DmBG2) of Drosophila melanogaster. When patterns of pulse-labeled proteins of the three different clones were compared, I observed quantitative variations affecting the rate of synthesis by twofold or more in 25-30% of the polypeptides and qualitative differences, always affecting less than 2% of the polypeptides. Patterns of protein synthesis were analyzed during the 24 d of culture, revealing both quantitative (increase or decrease; 40%) and qualitative (presence or absence; 3%) differences. More than 70 proteins synthesized in these cultures were secreted into the medium. Among them were two major groups of acidic proteins which disappeared with culture time. When cell lines and intact central nervous systems were compared, large differences in protein synthesis were observed. In fact, only 20% of the synthesized proteins were common to both isolated cells grown in vitro and the original nervous system in vivo.