Cullin-4B E3 ubiquitin ligase mediates Apaf-1 ubiquitination to regulate caspase-9 activity.

Apoptotic protease-activating factor 1 (Apaf-1) is a component of apoptosome, which regulates caspase-9 activity. In addition to apoptosis, Apaf-1 plays critical roles in the intra-S-phase checkpoint; therefore, impaired expression of Apaf-1 has been demonstrated in chemotherapy-resistant malignant melanoma and nuclear translocation of Apaf-1 has represented a favorable prognosis of patients with non-small cell lung cancer. In contrast, increased levels of Apaf-1 protein are observed in the brain in Huntington's disease. The regulation of Apaf-1 protein is not yet fully understood. In this study, we show that etoposide triggers the interaction of Apaf-1 with Cullin-4B, resulting in enhanced Apaf-1 ubiquitination. Ubiquitinated Apaf-1, which was degraded in healthy cells, binds p62 and forms aggregates in the cytosol. This complex of ubiquitinated Apaf-1 and p62 induces caspase-9 activation following MG132 treatment of HEK293T cells that stably express bcl-xl. These results show that ubiquitinated Apaf-1 may activate caspase-9 under conditions of proteasome impairment.

Selecting Bacterial Antagonists for Cucurbit Downy Mildew and Developing an Effective Application Method.

To identify new bacterial antagonists for cucurbit downy mildew (CDM) caused by Pseudoperonospora cubensis, 163 bacterial isolates were recovered from different microenvironments of field-grown cucumber plants. In the greenhouse, 19 representative isolates were applied to cucumber plants as a foliar spray (FS); 7 isolates achieved the efficacy over 60% against CDM, with 5 (DS22, HS10, DP14, HP4, and DS57) identified as Bacillus pumilus, B. licheniformis, Enterobacter sp., Bacillus sp., and Stenotrophomonas maltophilia, respectively. Strains DP14, DS22, and HS10 were assessed for their biocontrol effect on naturally occurring CDM in 2-year field trials (2010 and 2011), in which their overall efficacy relative to that of propamocarb was 106.25 to 117.17% with foliar spray plus root drench (FS+RD) but only 70.98 to 84.03% with FS. Coincidently, DP14 and HS10 applied as root drench (RD) alone also significantly reduced CDM. Under field conditions, DP14, DS22, and HS10 all successfully colonized cucumber leaves and the rhizosphere, and also significantly increased fruit yield by 37.60 to 51.03%, as well as nutrient levels. Taken together, Enterobacter sp. DP14, B. licheniformis HS10, and B. pumilus DS22 are plant-growth-promoting rhizobacteria effective in controlling CDM in the field, whose efficacy increased with FS+RD compared with FS alone.

Improvement of memory recall by quercetin in rodent contextual fear conditioning and human early-stage Alzheimer's disease patients.

Patients with Alzheimer's disease (AD) experience a wide array of cognitive deficits, which typically include the impairment of explicit memory. In previous studies, the authors reported that a flavonoid, quercetin, reduces the expression of ATF4 and delays memory deterioration in an early-stage AD mouse model. In the present study, the effects of long-term quercetin intake on memory recall were assessed using contextual fear conditioning in aged wild-type mice. In addition, the present study examined whether memory recall was affected by the intake of quercetin-rich onion (a new cultivar of hybrid onion 'Quergold') powder in early-stage AD patients. In-vivo analysis indicated that memory recall was enhanced in aged mice fed a quercetin-containing diet. Memory recall in early-stage AD patients, determined using the Revised Hasegawa Dementia Scale, was significantly improved by the intake of quercetin-rich onion (Quergold) powder for 4 weeks compared with the intake of control onion ('Mashiro' white onion) powder. These results indicate that quercetin might influence memory recall.

Expanded polyglutamine embedded in the endoplasmic reticulum causes membrane distortion and coincides with Bax insertion.

The endoplasmic reticulum (ER) is important in various cellular functions, such as secretary and membrane protein biosynthesis, lipid synthesis, and calcium storage. ER stress, including membrane distortion, is associated with many diseases such as Huntington's disease. In particular, nuclear envelope distortion is related to neuronal cell death associated with polyglutamine. However, the mechanism by which polyglutamine causes ER membrane distortion remains unclear. We used electron microscopy, fluorescence protease protection assay, and alkaline treatment to analyze the localization of polyglutamine in cells. We characterized polyglutamine embedded in the ER membrane and noted an effect on morphology, including the dilation of ER luminal space and elongation of ER-mitochondria contact sites, in addition to the distortion of the nuclear envelope. The polyglutamine embedded in the ER membrane was observed at the same time as Bax insertion. These results demonstrated that the ER membrane may be a target of polyglutamine, which triggers cell death through Bax.

CED-4 is an mRNA-binding protein that delivers ced-3 mRNA to ribosomes.

Cell death abnormal (ced)-3 and ced-4 genes regulate apoptosis to maintain tissue homeostasis in Caenorhabditis elegans. Apoptosome formation and CED-4 translocation drive CED-3 activation. However, the precise role of CED-4 translocation is not yet fully understood. In this study, using a combination of immunoprecipitation and reverse transcription-polymerase chain reaction methods in cells and a glutathione-S-transferase pull down assay in a cell-free system, we show that CED-4 binds ced-3 mRNA. In the presence of ced-3 mRNA, CED-4 protein is enriched in the microsomal fraction and interacts with ribosomal protein L10a in mammalian cells, increasing the levels of CED-3. These results suggest that CED-4 forms a complex with ced-3 mRNA and delivers it to ribosomes for translation.

Quercetin reduces eIF2α phosphorylation by GADD34 induction.

The production of amyloid ß (Aß) in the brain from Aß precursor protein (APP) through γ-secretase is important for the pathogenesis of Alzheimer's disease (AD). Our previous studies have demonstrated that autophagy impairment and endoplasmic reticulum stress increase presenilin 1 expression and enhance γ-secretase activity through the phosphorylation of eukaryotic translation initiation factor 2α (eIF2α) and the translation of activating transcription factor 4 (ATF4). However, the inhibitory molecules for γ-secretase are largely unknown. Here, we demonstrate that the levels of ATF4 expression are increased in the brain of APP23 AD model mice; furthermore, these levels enhanced in the brain of APP23 mice crossed with obese and diabetic db/db (Lepr(db/db)) mice. A polyhydroxylated flavonoid, quercetin, suppressed presenilin 1 expression and Aß secretion in autophagy-impaired cells by the induction of growth arrest and DNA damaged-inducible gene (GADD) 34, which mediates eIF2α dephosphorylation, leading to decreased ATF4 expression. GADD34 induction was observed in the brain of wild-type mice, and APP23 mice fed quercetin in their diet. After the long-term feeding of quercetin, deterioration in memory assessed by freezing behavior was delayed in APP23 mice. These results indicate that quercetin may reduce eIF2α phosphorylation and ATF4 expression through GADD34 induction in the brain, leading to the improvement of memory in aged mice and the delay of deterioration in memory at the early stage of AD in AD model mice.

Polyglutamine expansion disturbs the endoplasmic reticulum formation, leading to caspase-7 activation through Bax.

The endoplasmic reticulum (ER) plays a pivotal role in cellular functions such as the ER stress response. However, the effect of the ER membrane on caspase activation remains unclear. This study reveals that polyglutamine oligomers augmented at ER induce insertion of Bax into the ER membrane, thereby activating caspase-7. In line with the role of ER in cell death induced by polyglutamine expansion, the ER membrane was found to be disrupted and dilated in the brain of a murine model of Huntington's disease. We can conclude that polyglutamine expansion may drive caspase-7 activation by disrupting the ER membrane.

Rhizocompetence and antagonistic activity towards genetically diverse Ralstonia solanacearum strains--an improved strategy for selecting biocontrol agents.

Bacterial wilt caused by Ralstonia solanacearum is a serious threat for agricultural production in China. Eight soil bacterial isolates with activity against R. solanacearum TM15 (biovar 3) were tested in this study for their in vitro activity towards ten genetically diverse R. solanacearum isolates from China. The results indicated that each antagonist showed remarkable differences in its ability to in vitro antagonize the ten different R. solanacearum strains. Strain XY21 (based on 16S rRNA gene sequencing affiliated to Serratia) was selected for further studies based on its in vitro antagonistic activity and its excellent rhizocompetence on tomato plants. Under greenhouse conditions XY21 mediated biocontrol of tomato wilt caused by seven different R. solanacearum strains ranged from 19 to 70 %. The establishment of XY21 and its effects on the bacterial community in the tomato rhizosphere were monitored by denaturing gradient gel electrophoresis of 16S rRNA gene fragments PCR-amplified from total community DNA. A positive correlation of the in vitro antagonistic activities of XY21 and the actual biocontrol efficacies towards seven genetically different R. solanacearum strains was found and further confirmed by the efficacy of XY21 in controlling bacterial wilt under field conditions.

Olfaxin as a novel Prune2 isoform predominantly expressed in olfactory system.

Prune homolog 2 (Drosophila) (PRUNE2) encodes a BCH motif-containing protein that shares homology with the Cayman ataxia-related protein Caytaxin. Caytaxin is a substrate of caspase-3 and is specifically expressed at the presynapse of vesicular-type glutamate transporter (VGLUT)-positive neurons, where it plays a role in glutamate neurotransmission primarily in the cerebellum and hippocampus. Here, we showed that a novel Prune2 isoform contains a BCH motif and localizes predominantly to the synaptic cytosol, similar to Caytaxin. However, the isoform is expressed predominantly in the olfactory bulb and layer Ia of the piriform cortex, where Caytaxin is scarcely expressed. The isoform expression is upregulated during development, similar to that in the presynaptic-localizing proteins Synapsin I and Bassoon. Prune2 and its previously identified isoforms have been shown to be a susceptibility gene for Alzheimer's disease, a biomarker for leiomyosarcomas, a proapoptotic protein, and an antagonist of cellular transformation. In addition, a novel isoform may develop new roles for Prune2 at the synapse in olfactory systems.

Endoplasmic reticulum stress enhances γ-secretase activity.

The endoplasmic reticulum (ER) copes with unfolded proteins in the lumen (ER stress) by activating three distinct intracellular signaling pathways of unfolded protein response (UPR). ER stress contributes to the pathogenesis of obesity and diabetes, which are risk factors for Alzheimer's disease (AD) that accelerate the pathogenesis of AD. However, whether ER stress is involved in the development of AD remains unclear. In this study, we demonstrate that ER stress induces presenilin-1 expression through activating transcription factor 4 (ATF4), resulting in increased amyloid-ß (Aß) secretion by γ-secretase activity, which is suppressed by quercetin by modifying UPR signaling. This result suggests that ER stress may be stimulated in obesity and type 2 diabetes, thereby enhancing γ-secretase activity that is the underlying molecular mechanism affecting the pathogenesis of AD.

The expression and localization of Prune2 mRNA in the central nervous system.

A family of Bcl-2/adenovirus E1B 19kDa-interacting proteins (BNIPs) plays critical roles in several cellular processes such as cellular transformation, apoptosis, neuronal differentiation, and synaptic function, which are mediated by the BNIP2 and Cdc42GAP homology (BCH) domain. Prune homolog 2 (Drosophila) (PRUNE2) and its isoforms -C9orf65, BCH motif-containing molecule at the carboxyl terminal region 1 (BMCC1), and BNIP2 Extra Long (BNIPXL) - have been shown to be a susceptibility gene for Alzheimer's disease, a biomarker for leiomyosarcomas, a proapoptotic protein in neuronal cells, and an antagonist of cellular transformation, respectively. However, precise localization of PRUNE2 in the brain remains unclear. Here, we identified the distribution of Prune2 mRNA in the adult mouse brain. Prune2 mRNA is predominantly expressed in the neurons of the cranial nerve motor nuclei and the motor neurons of the spinal cord. The expression in the dorsal root ganglia (DRG) is consistent with the previously described reports. In addition, we observed the expression in another sensory neuron in the mesencephalic trigeminal nucleus. These results suggest that Prune2 may be functional in these restricted brain regions.

Cayman ataxia-related protein is a presynapse-specific caspase-3 substrate.

Caspase plays an important role in apoptosis and physiological processes such as synaptic plasticity. However, the caspase substrate at the synapse is still unknown. Here we used an in vitro cleavage assay with a small-pool human brain cDNA library. We identified the presynaptic protein Caytaxin as a substrate of caspase-3 and caspase-7. Deficiency in Caytaxin causes Cayman ataxia, a disorder characterized by cerebellar dysfunction and mental retardation. Caytaxin cleavage in cerebellar granule neurons is dependent on caspase-3 activation. The cleavage site is upstream of the cellular retinal and the TRIO guanine exchange factor domain, producing a C-terminal fragment that may play an alternative role in inhibiting MEK2 signaling. Thus, we concluded that Caytaxin is a novel substrate of caspase-3 at the presynapse.

Autophagy impairment stimulates PS1 expression and gamma-secretase activity.

Gamma-secretase plays an important role in the development of Alzheimer disease (AD). Gamma-secretase activity is enriched in autophagic vacuoles and it augments amyloid-beta (Abeta) synthesis. Autophagy-lysosomal dysfunction has been implicated in AD, but whether gamma-secretase activity is affected by autophagy remains unclear. Here we report that gamma-secretase activity is enhanced in basal autophagy-disturbed cells through the alpha subunit of eukaryotic translation initiation factor 2 (eIF2alpha) kinase, general control nonderepressible 2 (GCN2). Presenilin-1 (PS1) expression was increased even in the presence of nutrients in autophagy-related 5 knockdown (Atg5KD) human embryonic kidney (HE K293) cells expressing a short hairpin RNA as well as in chloroquine-treated HE K293 cells. However, PS1 expression induction was prevented in GCN2KD and ATF4KD cells. Furthermore, Atg5KD cells showed an increase in Abeta production and Notch1 cleavage. These were reduced by an autophagy inducer, resveratrol. Thus, we conclude that the autophagy-lysosomal system regulates gamma-secretase activity through GCN2.

An alternative spliced mouse presenilin-2 mRNA encodes a novel gamma-secretase inhibitor.

The gamma-secretase, composed of presenilin-1 (PS1) or presenilin-2 (PS2), nicastrin (NCT), anterior pharynx-defective phenotype 1 (APH-1), and PEN-2, is critical for the development of Alzheimer's disease (AD). PSs are autoproteolytically cleaved, producing an N-terminal fragment (NTF) and a hydrophilic loop domain-containing C-terminal fragment. However, the role of the loop domain in the gamma-secretase complex assembly remains unknown. Here, we report a novel PS2 isoform generated by alternative splicing, named PS2beta, which is composed of an NTF with a hydrophilic loop domain. PS2beta disturbed the interaction between NCT and APH-1, resulting in the inhibition of amyloid-beta production. We concluded that PS2beta may inhibit gamma-secretase activity by affecting the gamma-secretase complex assembly.

[RAPD analysis of plant pathogenic coryneform bacteria].

RAPD analysis was used for the taxonomy of plant pathogenic coryneform bacteria, especially for the classification of two new pathogens (Curtobacterium flaccumfaciens pv. basellae pv. nov. and Curtobacterium flaccumfaciens pv. beticola pv. nov.). 20 random primers were screened from 50 ones to detect polymorphism among the total strains used. 80.4% were polymorphic bands among the 225 ones produced. The results of pairwise similarity and UPGMA cluster analysis suggest that the two new pathovars of sugar beet (Beta vulgaris var. saccharifera) and malabar spinach (Basella rubra) are genetically close related with Curtobacterium flacumfaciens, and the minimal similarity coefficient is 0.6511. According to the RAPD analysis and previous research, some newly made taxonomic changes of the plant pathogenic coryneform bacteria are discussed.