Subcellular distribution of prohibitin 1 in rat liver during liver regeneration and its cellular implication

BACKGROUND The function of prohibitin 1(Phb1)during liver regeneration(LR)remains relatively unexplored.Our previous research identified downregulation of Phb1 in rat liver mitochondria 24 h after 70%partial hepatectomy(PHx),as determined by subcellular proteomic analysis.AIM To investigate the potential role of Phb1 during LR.METHODS We examined changes in Phb1 mRNA and protein levels,subcellular distribution,and abundance in rat liver during LR following 70%PHx.We also evaluated mitochondrial changes and apoptosis using electron microscopy and flow cytometry.RNA-interference-mediated knockdown of Phb1(PHBi)was performed in BRL-3A cells.RESULTS Compared with sham-operation control groups,Phb1 mRNA and protein levels in 70%PHx test groups were downregulated at 24 h,then upregulated at 72 and 168 h.Phb1 was mainly located in mitochondria,showed a reduced abundance at 24 h,significantly increased at 72 h,and almost recovered to normal at 168 h.Phb1 was also present in nuclei,with continuous increase in abundance observed 72 and 168 h after 70%PHx.The altered ultrastructure and reduced mass of mitochondria during LR had almost completely recovered to normal at 168 h.PHBi in BRL-3A cells resulted in increased S-phase entry,a higher number of apoptotic cells,and disruption of mitochondrial membrane potential.CONCLUSION Phb1 may contribute to maintaining mitochondrial stability and could play a role in regulating cell proliferation and apoptosis of rat liver cells during LR.

Intrinsic apoptotic pathway and G2/M cell cycle arrest involved in tubeimoside I-induced EC109 cell death

Objective： Squamous esophageal carcinoma is highly prevalent in developing countries, especially in China. Tu Bei Mu （TBM）, a traditional folk medicine, has been used to treat esophageal squamous cell carcinoma （ESCC） for a long term. tubeimoside I （TBMS1） is the main component of TBM, exhibiting great anticancer potential. In this study, we investigated the mechanism of TBMS1 cytotoxic effect on EC109 cells. Methods： Comparative nuclear proteomic approach was applied in the current study and we identified several altered protein spots. Further biochemical studies were carried out to detect the mitochondrial membrane potential, cell cycle and corresponding proteins＇ expression and location. Results： Subcellular proteomic study in the nucleus from EC109 cells revealed that altered proteins were associated with mitochondrial function and cell proliferation. Further biochemical studies showed that TBMSl-induced molecular events were related to mitochondria-induced intrinsic apoptosis and P21-cyclin B 1/cdc2 complex-related G2/M cell cycle arrest. Conclusions： Considering the conventional application of TBM in esophageal cancer, TBMS1 therefore may have a great potential as a chemotherapeutic drug candidate for ESCC.

Retrograde signaling in plants: A critical review focusing on the GUN pathway and beyond

Plastids communicate their developmental and physiological status to the nucleus via retrograde signaling,allowing nuclear gene expression to be adjusted appropriately.Signaling during plastid biogenesis and responses of mature chloroplasts to environmental changes are designated“biogenic”and“operational”controls,respectively.A prominent example of the investigation of biogenic signaling is the screen for gun(genomes uncoupled)mutants.Although the first five gun mutants were identified 30 years ago,the functions of GUN proteins in retrograde signaling remain controversial,and that of GUN1 is hotly disputed.Here,we provide background information and critically discuss recently proposed concepts that address GUN-related signaling and some novel gun mutants.Moreover,considering heme as a candidate in retrograde signaling,we revisit the spatial organization of heme biosynthesis and export from plastids.Although this review focuses on GUN pathways,we also highlight recent progress in the identification and elucidation of chloroplast-derived signals that regulate the acclimation response in green algae and plants.Here,stress-induced accumulation of unfolded/misassembled chloroplast proteins evokes a chloroplast-specific unfolded protein response,which leads to changes in the expression levels of nucleus-encoded chaperones and proteases to restore plastid protein homeostasis.We also address the importance of chloroplast-derived signals for activation of flavonoid biosynthesis leading to production of anthocyanins during stress acclimation through sucrose non-fermenting 1-related protein kinase 1.Finally,a framework for identification and quantification of intercompartmental signaling cascades at the proteomic and metabolomic levels is provided,and we discuss future directions of dissection of organelle-nucleus communication.