iTRAQ-based proteomic identification of proteins involved in anti-angiogenic effects of Panduratin A on HUVECs.

Panduratin A (PA), a cyclohexanyl chalcone from Boesenbergia rotunda (L.) Mansf. was shown to possess anti-angiogenic effects in our previous study. In the present study, the molecular targets and anti-angiogenic mechanisms of PA on human umbilical vein endothelial cells (HUVECs) were identified using an iTRAQ-based quantitative proteomics approach. A total of 263 proteins were found to be differentially regulated in response to treatment with PA. Ingenuity Pathway Analysis revealed that cellular growth and proliferation, protein synthesis, RNA post-transcriptional modification, cellular assembly and organization and cell-to-cell signaling and interaction were the most significantly deregulated molecular and cellular functions in PA-treated HUVECs. PA inhibited the expressions of ARPC2 and CTNND1 that are associated with the formation of actin cytoskeleton, focal adhesion and cellular protrusions. In addition, PA down-regulated CD63, GRB-2, ICAM-2 and STAB-1 that are implicated in adhesion, migration and tube formation of endothelial cells. The differential expressions of three targets, namely, ARPC2, CDK4, and GRB-2 were validated by western blot analyses. Furthermore, PA inhibited G1-S progression, and resulted in G0/G1 arrest in HUVECs. The blockage in cell cycle progression was accompanied with the suppression of mTOR signaling. Treatment of HUVECs with PA resulted in decreased phosphorylation of ribosomal S6 and 4EBP1 proteins, the two downstream effectors of mTOR signaling. We further showed that PA is able to inhibit mTOR signaling induced by VEGF, a potent inducer of angiogenesis. Taken together, by integrating quantitative proteomic approach, we identified protein targets in which PA mediates its anti-angiogenic effects. The present study thus provides mechanistic evidence to the previously reported multifaceted anti-angiogenic effects of PA. Our study further identified mTOR signaling as an important target of PA, and therefore highlights the potential of PA for therapeutic intervention against angiogenesis-related pathogenesis, particularly, metastatic malignancy.

Proteomic analysis of the oil palm fruit mesocarp reveals elevated oxidative phosphorylation activity is critical for increased storage oil production.

Palm oil is a highly versatile commodity with wide applications in the food, cosmetics, and biofuel industries. Storage oil in the oil palm mesocarp can make up a remarkable 80% of its dry mass, making it the oil crop with the richest oil content in the world. As such, there has been an ongoing interest in understanding the mechanism of oil production in oil palm fruits. To identify the proteome changes during oil palm fruit maturation and factors affecting oil yield in oil palm fruits, we examined the proteomic profiles of oil palm mesocarps at four developing stages--12, 16, 18, and 22 weeks after pollination--by 8-plex iTRAQ labeling coupled to 2D-LC and MALDI-TOF/TOF MS. It was found that proteins from several important metabolic processes, including starch and sucrose metabolism, glycolysis, pentose phosphate shunt, fatty acid biosynthesis, and oxidative phosphorylation, were differentially expressed in a concerted manner. These increases led to an increase in carbon flux and a diversion of resources such as ATP and NADH that are required for lipid biosynthesis. The temporal proteome profiles between the high-oil-yielding (HY) and low-oil-yielding (LY) fruits also showed significant differences in the levels of proteins involved in the regulation of the TCA cycle and oxidative phosphorylation. In particular, the expression level of the ß subunit of the ATP synthase complex (complex IV of the electron transport chain) was found to be increased during fruit maturation in HY but decreased in the LY during the fruit maturation. These results suggested that increased energy supply is necessary for augmented oil yield in the HY oil palm trees.