In seed plants, a major pathway for sorting of storage proteins to the protein storage vacuole (PSV) depends on the Golgi-derived dense vesicles (DVs). However, the molecular mechanisms regulating the directional trafficking of DVs to PSVs remain largely elusive. Here, we report the functional characterization of the rice (Oryza sativa) glutelin precursor accumulation3 (gpa3) mutant, which exhibits a floury endosperm phenotype and accumulates excess proglutelins in dry seeds. Cytological and immunocytochemistry studies revealed that in the gpa3 mutant, numerous proglutelin-containing DVs are misrouted to the plasma membrane and, via membrane fusion, release their contents into the apoplast to form a new structure named the paramural body. Positional cloning of GPA3 revealed that it encodes a plant-specific kelch-repeat protein that is localized to the trans-Golgi networks, DVs, and PSVs in the developing endosperm. In vitro and in vivo experiments verified that GPA3 directly interacts with the rice Rab5a-guanine exchange factor VPS9a and forms a regulatory complex with Rab5a via VPS9a. Furthermore, our genetic data support the notion that GPA3 acts synergistically with Rab5a and VPS9a to regulate DV-mediated post-Golgi traffic in rice. Our findings provide insights into the molecular mechanisms regulating the plant-specific PSV pathway and expand our knowledge of vesicular trafficking in eukaryotes. 相似文献
Hormozgan Province plays a vital role in fishery, petroleum, and industrial activities in southern Iran. However, no comprehensive studies on organic pollution have been performed. PCBs and PAHs were analyzed in surface sediments from areas receiving industrial (nine sites), river (one site), and urban (two sites) effluents. The sediment samples were collected in March and September 2010 (in dry and wet seasons) at the highest tidal time. The overall pollution level of PCBs ranged from 2.5 ± 0.8 to 462.0 ± 206.7 ng/g dry weight. CB153 congener dominated in most of the sediment samples. Congener profiles of PCBs showed close similarity with formulations of commercial products such as Aroclor 1260 and 1254 g. A wide range of 55.3 to 1231.6 ng/g dry weight was detected for ∑PAHs. Results of PCA and PCA-MLR tests confirmed both petrogenic and pyrogenic origins for PAH pollution. The higher means of ∑PAHs and ∑PCBs in industrial and urban wastewaters were found near the shore, evidencing the role of these wastewaters in the PAH and PCB contamination in Hormozgan sediment. The concentrations of PAHs and PCBs in detected hotspots exceed the U.S. NOAA sediment quality guidelines. 相似文献
Shikonin, a natural naphthoquinone isolated from a traditional Chinese medicinal herb, can exert inhibitory effect on tumor cell growth. However, little has been known concerning the effect of shikonin on lung adenocarcinoma cell and underlying mechanisms. In the present study, we investigated the effect of shikonin on the proliferation, cell cycle arrest, and apoptosis in human lung adenocarcinoma cells. We found that shikonin significantly suppressed the proliferation of lung adenocarcinoma cells compared with control in dose- and time-dependent manner (P < 0.05). In the meantime, our results showed that shikonin markedly increased the proportion of A549 cells at stage G1 as well as induced apoptosis in A549 cells. Furthermore, suppressed CCND1 and elevated caspase3 and caspase7 expression levels at mRNA were found in this study, indicating that shikonin may inhibit the growth of lung adenocarcinoma cell by changing cell cycle and promoting cell apoptosis through the regulation of CCND1, caspase3, and caspase7. Although more studies are needed, this study suggests that shikonin has the potential to be used as an anti-cancer agent in the treatment of lung adenocarcinoma. 相似文献
Necroptosis is mediated by a signaling complex called necrosome, containing receptor-interacting protein (RIP)1, RIP3, and mixed-lineage kinase domain-like (MLKL). It is known that RIP1 and RIP3 form heterodimeric filamentous scaffold in necrosomes through their RIP homotypic interaction motif (RHIM) domain-mediated oligomerization, but the signaling events based on this scaffold has not been fully addressed. By using inducible dimer systems we found that RIP1–RIP1 interaction is dispensable for necroptosis; RIP1–RIP3 interaction is required for necroptosis signaling, but there is no necroptosis if no additional RIP3 protein is recruited to the RIP1–RIP3 heterodimer, and the interaction with RIP1 promotes the RIP3 to recruit other RIP3; RIP3–RIP3 interaction is required for necroptosis and RIP3–RIP3 dimerization is sufficient to induce necroptosis; and RIP3 dimer-induced necroptosis requires MLKL. We further show that RIP3 oligomer is not more potent than RIP3 dimer in triggering necroptosis, suggesting that RIP3 homo-interaction in the complex, rather than whether RIP3 has formed homo polymer, is important for necroptosis. RIP3 dimerization leads to RIP3 intramolecule autophosphorylation, which is required for the recruitment of MLKL. Interestingly, phosphorylation of one of RIP3 in the dimer is sufficient to induce necroptosis. As RIP1–RIP3 heterodimer itself cannot induce necroptosis, the RIP1–RIP3 heterodimeric amyloid fibril is unlikely to directly propagate necroptosis. We propose that the signaling events after the RIP1–RIP3 amyloid complex assembly are the recruitment of free RIP3 by the RIP3 in the amyloid scaffold followed by autophosphorylation of RIP3 and subsequent recruitment of MLKL by RIP3 to execute necroptosis.Necroptosis is a type of programmed necrosis characterized by necrotic morphological changes, including cellular organelle swelling, cell membrane rupture,1, 2, 3 and dependence of receptor-interacting protein (RIP)14 and RIP3.5, 6, 7 Physiological function of necroptosis has been illustrated in host defense,8, 9, 10, 11 inflammation,12, 13, 14, 15, 16 tissue injury,10, 17, 18 and development.19, 20, 21Necroptosis can be induced by a number of different extracellular stimuli such as tumor necrosis factor (TNF). TNF stimulation leads to formation of TNF receptor 1 (TNFR1) signaling complex (named complex I), and complex II containing RIP1, TRADD, FAS-associated protein with a death domain (FADD), and caspase-8, of which the activation initiates apoptosis. If cells have high level of RIP3, RIP1 recruits RIP3 to form necrosome containing FADD,22, 23, 24 caspase-8, RIP1, and RIP3, and the cells undergo necroptosis.25, 26 Caspase-8 and FADD negatively regulates necroptosis,27, 28, 29, 30 because RIP1, RIP3, and CYLD are potential substrates of caspase-8.31, 32, 33, 34 Necrosome also suppresses apoptosis but the underlying mechanism has not been described yet. Mixed-lineage kinase domain-like (MLKL) is downstream of RIP3,35, 36 and phosphorylation of MLKL is required for necroptosis.37, 38, 39, 40, 41, 42Apoptosis inducing complex (complex II) and necrosome are both supramolecular complexes.43, 44, 45 A recent study showed that RIP1 and RIP3 form amyloidal fibrils through their RIP homotypic interaction motif46 (RHIM)-mediated polymerization, and suggested that amyloidal structure is essential for necroptosis signaling.47 The RIP1–RIP3 heterodimeric amyloid complex is believed to function as a scaffold that brings signaling proteins into proximity to permit their activation. However, RIP1 and RIP3 also can each form fibrils on their own RHIM domains in vitro. It is unclear how the homo- and hetero-interactions are coordinated and organized on the amyloid scaffold to execute their functions in necroptosis. Here, we used inducible dimerization systems to study the roles of RIP1–RIP1, RIP1–RIP3, and RIP3–RIP3 interactions in necroptosis signaling. Our data suggested that it is the RIP1–RIP3 interaction in the RIP1–RIP3 heterodimeric amyloid complex that empowers to recruit other free RIP3; homodimerization of RIP3 triggers its autophosphorylation and only the phosphorylated RIP3 can recruit MLKL to execute necroptosis. 相似文献
AFP111 is a spontaneous mutant of Escherichia coli with mutations in the glucose-specific phosphotransferase system, pyruvate formate lyase system, and fermentative lactate dehydrogenase system, created to reduce byproduct formation and increase succinic acid accumulation. In AFP111, conversion of xylose to succinic acid only generates 1.67 ATP per xylose, but requires 2.67 ATP for xylose metabolism. Therefore, the ATP produced is not adequate to accomplish the conversion of xylose to succinic acid in chemically defined medium. An E. coli mutant was obtained by atmospheric and room-temperature plasmas and metabolic evolution strategies, which had the ability to use xylose and improve the capacity of cell growth. The concentration of ATP in the mutant was 1.33-fold higher than that in AFP111 during xylose fermentation. In addition, under anaerobic fermentation with almost 80 % xylose from corn stalk hydrolysate, a succinic acid concentration of 21.1 g l?1 was obtained, with a corresponding yield of 76 %. 相似文献
Proteoglycans (PGs) are major constituents of the extracellular matrix and have recently been proposed to contribute to synaptic plasticity. Hippocampal PGs have not yet been studied or linked to memory. The aim of the study, therefore, was to isolate and characterize rat hippocampal PGs and determine their possible role in spatial memory. PGs were extracted from rat hippocampi by anion‐exchange chromatography and analyzed by nano LC‐MS/MS. Twenty male Sprague–Dawley rats were tested in the morris water maze. PGs agrin, amyloid beta A4 protein, brevican, glypican‐1, neurocan, phosphacan, syndecan‐4, and versican were identified in the hippocampi. Brevican and versican levels in the membrane fraction were higher in the trained group, correlating with the time spent in the target quadrant. α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate receptor GluR1 was co‐precipitated with brevican and versican. Levels for a receptor complex containing GluR1 was higher in trained while GluR2 and GluR3‐containing complex levels were higher in yoked rats. The findings provide information about the PGs present in the rat hippocampus, demonstrating that versican and brevican are linked to memory retrieval in the morris water maze and that PGs interact with α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate receptor GluR1, which is linked to memory retrieval.