Background. Diurnal rhythms of protein synthesis controlled by the biological clock underlie rhythmic physiology in the fruit fly, Drosophila melanogaster. Self-sustained autonomous circadian oscillations were documented all over the organs of the fly. In this study, we conducted a proteome-wide investigation of rhythmic protein accumulation in D. melanogaster. Materials and Methods. We have used the whole fly for the proteomic study as performed in typical proteotypic peptide (PTP) studies and followed the same protocol with trypsin digestion. Total protein collected from fly samples harvested at 4h intervals over the 24-h period were subjected to two dimensional (2-D) gel electrophoresis, trypsin digestion and MS/MS analysis. Protein spots/clusters were identified with MASCOT search engine and Swiss-Prot database. Expression of proteins was documented as percentage of volume contribution using the Image Master 2D Platinum software. Results. A total of 124 protein spots/clusters were identified using MS/MS analysis. A significant variation in the expression of 88 proteins over the 24-h period was observed. Our present results suggested that the synthesis/regulation of numerous proteins is regulated by the biological clock in D. melanogaster. Relatively higher number of proteins was upregulated during nighttime as compared to daytime. Conclusion. As these rhythmically varying proteins/enzymes involve in metabolism, muscle activities, ion channels, protein synthesis, redox homeostasis and apoptosis our results indicate that these cellular processes could be regulated at the level of temporal expression of protein profile.
2-D LC-MS/MS Analysis of secreted proteins from HepG2 cells: Combination with various sample preparation methods before in-solution trypsin digestion