The S100 protein family: history, function, and expression

The S100 family of calcium binding proteins contains approximately 16 members each of which exhibits a unique pattern of tissue/cell type specific expression. Although the distribution of these proteins is not restricted to the nervous system, the implication of several members of this family in nervous system development, function, and disease has sparked new interest in these proteins. We now know that the original two members of this family, S100A1 and S100B, can regulate a diverse group of cellular functions including cell-cell communication, cell growth, cell structure, energy metabolism, contraction and intracellular signal transduction. Although some members of the family may function extracellularly, most appear to function as intracellular calcium-modulated proteins and couple extracellular stimuli to cellular responses via interaction with other cellular proteins called target proteins. Interaction of these proteins with target proteins appear to involve cysteine residues (one in S100A1 and two in S100B), as well as a stretch of 13 amino acids, in the middle of the molecule called the linker region, which connects the two EF-hand calcium binding domains. In addition to the amino acid sequence and secondary structures of these proteins, the structures of the genes encoding these proteins are highly conserved. Studies on the expression of these proteins have demonstrated that a complex mixture of transcriptional and postranscriptional mechanisms regulate S100 expression. Further analysis of the function and expression of these proteins in both nervous and nonnervous tissues will provide important information regarding the role of altered S100 expression in nervous system development, function and disease.

DARPP-32: regulator of the efficacy of dopaminergic neurotransmission

Dopaminergic neurons exert a major modulatory effect on the forebrain. Dopamine and adenosine 3',5'-monophosphate-regulated phosphoprotein (32 kilodaltons) (DARPP-32), which is enriched in all neurons that receive a dopaminergic input, is converted in response to dopamine into a potent protein phosphatase inhibitor. Mice generated to contain a targeted disruption of the DARPP-32 gene showed profound deficits in their molecular, electrophysiological, and behavioral responses to dopamine, drugs of abuse, and antipsychotic medication. The results show that DARPP-32 plays a central role in regulating the efficacy of dopaminergic neurotransmission.

Dendritic cells genetically modified with an adenovirus vector encoding the cDNA for a model antigen induce protective and therapeutic antitumor immunity

Dendritic cells (DCs) are potent antigen-presenting cells that play a critical role in the initiation of antitumor immune responses. In this study, we show that genetic modifications of a murine epidermis-derived DC line and primary bone marrow-derived DCs to express a model antigen beta-galactosidase (betagal) can be achieved through the use of a replication-deficient, recombinant adenovirus vector, and that the modified DCs are capable of eliciting antigen-specific, MHC-restricted CTL responses. Importantly, using a murine metastatic lung tumor model with syngeneic colon carcinoma cells expressing betagal, we show that immunization of mice with the genetically modified DC line or bone marrow DCs confers potent protection against a lethal tumor challenge, as well as suppression of preestablished tumors, resulting in a significant survival advantage. We conclude that genetic modification of DCs to express antigens that are also expressed in tumors can lead to antigen-specific, antitumor killer cells, with a concomitant resistance to tumor challenge and a decrease in the size of existing tumors.

Proteolytic release and nuclear translocation of Notch-1 are induced by presenilin-1 and impaired by pathogenic presenilin-1 mutations

The Notch family of proteins consists of transmembrane receptors that play a critical role in the determination of cell fate. Genetic studies in Caenorhabditis elegans suggest that the presenilin proteins, which are associated with familial Alzheimer's disease, regulate Notch signaling. Here we show that proteolytic release of the Notch-1 intracellular domain (NICD), an essential step in the activation of Notch signaling, is markedly reduced in presenilin-1 (PS1)-deficient cells and is restored by PS1 expression. Nuclear translocation of the NICD is also markedly reduced in PS1-deficient cells, resulting in reduced transcriptional activation. Mutations in PS1 that are associated with familial Alzheimer's disease impair the ability of PS1 to induce proteolytic release of the NICD and nuclear translocation of the cleaved protein. These results suggest that PS1 plays a central role in the proteolytic activation of the Notch-1-signaling pathway and that this function is impaired by pathogenic PS1 mutations. Thus, dysregulation of proteolytic function may underlie the mechanism by which presenilin mutations cause Alzheimer's disease.

Gp60 activation mediates albumin transcytosis in endothelial cells by tyrosine kinase-dependent pathway

We investigated the function of gp60, an endothelial cell membrane 60-kDa albumin-binding protein localized in caveolae, and the mechanism of its activation in regulating endothelial permeability of albumin. Gp60 organization on the bovine pulmonary microvessel endothelial cell (BPMVEC) surface was punctate as shown by immunofluorescence using an anti-gp60 antibody (Ab) conjugated with bisfunctional, N-hydroxysuccinimidyl fluorophore (Cy3). Addition of a secondary Ab to anti-gp60 Ab-treated BPMVEC induced cross-linking of gp60 as evident by increased size of fluorescent particles and cell surface gp60 clustering. Gp60 cross-linking also produced 2-3-fold increases in the endothelial cell uptake and the luminal to abluminal permeability of 125I-albumin as well as the fluid-phase tracer, horseradish peroxidase. The increased transendothelial permeability of macromolecules was the result of transcytosis as it was not associated with an increase in the paracellular pathway. Incubation of anti-gp60 Ab with BPMVEC at 37 degrees C caused internalization of gp60, and thereby reduced the uptake of the macromolecules. Activation of gp60 by either albumin (the gp60 ligand) or gp60 cross-linking induced the phosphorylation of both gp60 and caveolin-1 (the major structural caveolar protein) on tyrosine residues. Gp60 activation also phosphorylated the Src family tyrosine kinases pp60(c-Src) and Fyn. The activated pp60(c-Src) and Fyn co-immunoprecipitated with caveolin-1 in BPMVEC membrane. Protein tyrosine kinase (PTK) inhibitors, herbimycin A and genistein, prevented gp60-activated macromolecule uptake and transcytosis in a concentration-dependent manner, indicating the functional significance of the PTK pathway in activating albumin transcytosis. These findings indicate that activation of gp60 stimulates the Src PTK signaling pathway, and thus regulates the transcytosis of albumin across the endothelial cell monolayer.

First-line icotinib versus cisplatin/pemetrexed plus pemetrexed maintenance therapy for patients with advanced EGFR mutation-positive lung adenocarcinoma (CONVINCE): a phase 3, open-label, randomized study

BACKGROUND

Icotinib has been previously shown to be non-inferior to gefitinib in non-selected advanced non-small-cell lung cancer patients when given as second- or further-line treatment. In this open-label, randomized, phase 3 CONVINCE trial, we assessed the efficacy and safety of first-line icotinib versus cisplatin/pemetrexed plus pemetrexed maintenance in lung adenocarcinoma patients with epidermal growth factor receptor (EGFR) mutation.

PATIENTS AND METHODS

Eligible participants were adults with stage IIIB/IV lung adenocarcinoma and exon 19/21 EGFR mutations. Participants were randomly allocated (1 : 1) to receive oral icotinib or 3-week cycle of cisplatin plus pemetrexed for up to four cycles; non-progressive patients after four cycles were maintained with pemetrexed until disease progression or intolerable toxicity. The primary end point was progression-free survival (PFS) assessed by independent response evaluation committee. Other end points included overall survival (OS) and safety.

RESULTS

Between January 2013 and August 2014, 296 patients were randomized, and 285 patients were treated (148 to icotinib, 137 to chemotherapy). Independent response evaluation committee-assessed PFS was significantly longer in the icotinib group (11.2 versus 7.9 months; hazard ratio, 0.61, 95% confidence interval 0.43-0.87; P = 0.006). No significant difference for OS was observed between treatments in the overall population or in EGFR-mutated subgroups (exon 19 Del/21 L858R). The most common grade 3 or 4 adverse events (AEs) in the icotinib group were rash (14.8%) and diarrhea (7.4%), compared with nausea (45.9%), vomiting (29.2%), and neutropenia (10.9%) in the chemotherapy group. AEs (79.1% versus 94.2%; P < 0.001) and treatment-related AEs (54.1% versus 90.5%; P < 0.001) were significantly fewer in the icotinib group than in the chemotherapy group.

CONCLUSIONS

First-line icotinib significantly improves PFS of advanced lung adenocarcinoma patients with EGFR mutation with a tolerable and manageable safety profile. Icotinib should be considered as a first-line treatment for this patient population.

A role for the proteasome in the light response of the timeless clock protein

The cyclic expression of the period (PER) and timeless (TIM) proteins is critical for the molecular circadian feedback loop in Drosophila. The entrainment by light of the circadian clock is mediated by a reduction in TIM levels. To elucidate the mechanism of this process, the sensitivity of TIM regulation by light was tested in an in vitro assay with inhibitors of candidate proteolytic pathways. The data suggested that TIM is degraded through a ubiquitin-proteasome mechanism. In addition, in cultures from third-instar larvae, TIM degradation was blocked specifically by inhibitors of proteasome activity. Degradation appeared to be preceded by tyrosine phosphorylation. Finally, TIM was ubiquitinated in response to light in cultured cells.

Novel pH-sensitive citrate cross-linked chitosan film for drug controlled release

Turbidimetric titration revealed that there were electrostatic attractive interactions between citrate and chitosan in the pH region of 4.3-7.6, depending on their degree of ionization. Citrate cross-linked chitosan film was prepared simply by dipping chitosan film into sodium citrate solution. The swelling ratio of citrate/chitosan film was sensitive to pH, ionic strength etc. Under acidic conditions, citrate/chitosan film swelled and even dissociated in the pH less than 3.5, and the model drugs (brilliant blue and riboflavin) incorporated in the film were released quickly (usually within 2 h released completely in simulated gastric fluid at 37 degrees C) while under neutral conditions the swelling ratio of citrate/chitosan film was less significant and the release rate of brilliant blue and riboflavin was low (less than 40% released in simulated intestinal fluid in 24 h). Sodium chloride weakened the electrostatic interaction between citrate and chitosan, and therefore facilitated the film swelling and accelerated drug release. The parameters of film preparation such as citrate concentration, solution pH etc. influencing the film swelling and drug release profiles were examined. The lower concentration and the higher pH of citrate solution resulted in a larger swelling ratio and quicker riboflavin release. To improve the drug controlled release properties of citrate/chitosan film, heparin, pectin and alginate were further coated on the film surface. Among them only the coating of alginate prolonged riboflavin release noticeably (for 80% of drug released the time was extended from 1.5 to 3.5 h with 0.5% w/v alginate used). The results indicated that the citrate/chitosan film was useful in drug delivery such as for the site-specific drug controlled release in stomach.

Epidermal growth factor receptor agonists increase expression of glutamate transporter GLT-1 in astrocytes through pathways dependent on phosphatidylinositol 3-kinase and transcription factor NF-kappaB

The glial glutamate transporter GLT-1 may be the predominant Na(+)-dependent glutamate transporter in forebrain. Expression of GLT-1 correlates with astrocyte maturation in vivo and increases during synaptogenesis. In astrocyte cultures, GLT-1 expression parallels differentiation induced by cAMP analogs or by coculturing with neurons. Molecule(s) secreted by neuronal cultures contribute to this induction of GLT-1, but little is known about the signaling pathways mediating this regulation. In the present study, we determined whether growth factors previously implicated in astrocyte differentiation regulate GLT-1 expression. Of the six growth factors tested, two [epidermal growth factor (EGF) and transforming growth factor-alpha] induced expression of GLT-1 protein in cultured astrocytes. Induction of GLT-1 protein was accompanied by an increase in mRNA and in the V(max) for Na(+)-dependent glutamate transport activity. The effects of dibutyryl-cAMP and EGF were additive but were independently blocked by inhibitors of protein kinase A or protein tyrosine kinases, respectively. The induction of GLT-1 in both EGF- and dibutyryl-cAMP-treated astrocytes was blocked by inhibitors targeting phosphatidylinositol 3-kinase (PI3K) or the nuclear transcription factor-kappaB. Furthermore, transient transfection of astrocyte cultures with a constitutively active PI3K construct was sufficient to induce expression of GLT-1. These data suggest that independent but converging pathways mediate expression of GLT-1. Although an EGF receptor-specific antagonist did not block the effects of neuron-conditioned medium, the induction of GLT-1 by neuron-conditioned medium was completely abolished by inhibition of PI3K or nuclear factor-kappaB. EGF also increased expression of GLT-1 in spinal cord organotypic cultures. Together, these data suggest that activation of specific signaling pathways with EGF-like molecules may provide a novel approach for limiting excitotoxic brain injury.

Modulation of the neuronal glutamate transporter EAAT4 by two interacting proteins

Glutamate is the main excitatory neurotransmitter in the mammalian central nervous system and is removed from the synaptic cleft by sodium-dependent glutamate transporters. To date, five distinct glutamate transporters have been cloned from animal and human tissue: GLAST (EAAT1), GLT-1 (EAAT2), EAAC1 (EAAT3), EAAT4, and EAAT5 (refs 1-5). GLAST and GLT-1 are localized primarily in astrocytes, whereas EAAC1 (refs 8, 9), EAAT4 (refs 9-11) and EAAT5 (ref 5) are neuronal. Studies of EAAT4 and EAAC1 indicate an extrasynaptic localization on perisynaptic membranes that are near release sites. This localization facilitates rapid glutamate binding, and may have a role in shaping the amplitude of postsynaptic responses in densely packed cerebellar terminals. We have used a yeast two-hybrid screen to identify interacting proteins that may be involved in regulating EAAT4--the glutamate transporter expressed predominately in the cerebellum--or in targeting and/or anchoring or clustering the transporter to the target site. Here we report the identification and characterization of two proteins, GTRAP41 and GTRAP48 (for glutamate transporter EAAT4 associated protein) that specifically interact with the intracellular carboxy-terminal domain of EAAT4 and modulate its glutamate transport activity.

Expression and clinical significance of the stem cell marker CD133 in hepatocellular carcinoma

BACKGROUND

Although the primitive haematopoietic and neuronal stem cell marker CD133 is known to be present in cancer stem cells (CSCs) in hepatocellular carcinoma (HCC), the postresection prognostic impact of CD133 in HCC patients remains limited.

METHODS

Sixty-three resected specimens were collected from HCC patients. The expression of CD133 protein was analysed by immunohistochemistry and the association of CD133 expression with clinicopathological characteristics, tumour recurrence and survival of the patients was evaluated.

RESULTS

Immunohistochemical analysis of 63 HCC tissue specimens revealed that CD133 positive tumour cells were frequently present in HCC. Increased CD133 immunostaining was found in 26 specimens (41.3%). Increased CD133 expression levels were correlated with increased tumour grade, advanced disease stage, and elevated serum alpha-fetoprotein levels. Kaplan-Meier analysis indicated that patients with increased CD133 levels had shorter overall survival and higher recurrence rates compared with patients with low CD133 expression. Multivariate analyses revealed that increased CD133 expression was an independent prognostic factor for survival and tumour recurrence in patients with HCC.

CONCLUSIONS

These findings suggest that reactivated CD133 positive cells are frequently present in HCC. Additionally, increased CD133 expression corresponds with higher stage tumours in HCC, thus indicating a poor prognosis for patients. These data support the CSC hypothesis.

Oxidative stress potentiates BACE1 gene expression and Abeta generation

Alzheimer's Disease (AD) is the most common neurodegenerative disorder leading to dementia and its prevalence increases with age. The pathological features of AD are characterized by the beta-amyloid protein (A(beta)) deposits in the core of neuritic plaques and abnormal neurofibrillary tangles in the brain of AD patients. BACE1 is the major beta-secretase to cleave the beta-amyloid precursor protein (APP) to generate A(beta). Oxidative stress has been shown to affect A(beta) generation in the AD pathogenesis and the mechanism of such effect is unknown. In this report we generated a novel promoterless enhanced green fluorescent protein (EGFP) reporter gene cloning vector and cloned a 1.9-kb BACE1 gene promoter fragment in this vector. The BACE1 promoter fragment can efficiently activate EGFP or luciferase gene transcription. Oxidative stress induced by hydrogen peroxide resulted in significant increase in the BACE1 promoter activity. Furthermore, hydrogen peroxide treatment facilitated beta-secretase activity and A(beta) generation. Thus, upregulation of BACE1 transcription by oxidative stress may contribute to the pathogenesis of Alzheimer's disease.

Supramolecular origins of product selectivity for methanol-to-olefin catalysis on HSAPO-34

Ethylene selectivity in methanol-to-olefin (MTO) catalysis is related to the number of methyl groups on benzene rings trapped in the nanocages of the preferred catalyst HSAPO-34. By correlating the time evolutions of the catalysts' 13C NMR spectra and the volatile product distribution following abrupt cessation of methanol flow, we discovered that (in the absence of other adsorbates) propene is favored by methylbenzenes with four to six methyl groups but ethylene is predominant from those with two or three methyl groups. We substantially increased ethylene selectivity by operating at lower methanol partial pressures or higher temperatures, either of which reduces the steady-state average methyl substitution. As a step toward a kinetic analysis of the MTO reaction on HSAPO-34, we treated each nanocage with a methylbenzene molecule as a supramolecule capable of unimolecular dissociation into ethylene or propene and a less highly substituted methylbenzene. Addition of a water molecule to a nanocage containing a methylbenzene produces a distinct supramolecule with unique properties. Indeed, co-feeding water with methanol significantly increased the average number of methyl groups per ring at steady state relative to identical conditions without additional water, and also increased ethylene selectivity, apparently through transition state shape selectivity.

Molecular links between Alzheimer's disease and diabetes mellitus

Substantial epidemiological evidence shows an increased risk for developing Alzheimer's disease (AD) in people with diabetes. Yet the underlying molecular mechanisms still remain to be elucidated. This article reviews the current studies on common pathological processes of Alzheimer's disease and diabetes with particular focus on potential mechanisms through which diabetes affects the initiation and progression of Alzheimer's disease. Impairment of insulin signaling, inflammation, oxidative stress, mitochondrial dysfunction, advanced glycation end products, APOEε4 and cholesterol appear to be important mediators and are likely to act synergistically in promoting AD pathology.

Regional suppression of tumor growth by in vivo transfer of a cDNA encoding a secreted form of the extracellular domain of the flt-1 vascular endothelial growth factor receptor

Vascular endothelial growth factor (VEGF), a potent angiogenic mediator, is overexpressed in most solid tumors. On the basis of the knowledge that solid tumor growth beyond a small volume is critically dependent on angiogenesis, and that adenovirus (Ad) vectors can mediate efficient in vivo gene transfer and expression, we hypothesized that Ad-mediated transfer of a secreted form of the extracellular domain of the flt-1 VEGF receptor (Adsflt) would suppress tumor growth on a regional basis. To evaluate this concept, three tumor models were examined using a murine colon carcinoma cell line and syngeneic BALB/c mice. First, mice with preestablished splenic CT26.CL25 tumors and liver metastases were given Adsflt on AdNull intravenously and, after 15 days, spleens and livers were harvested to quantify tumor burden. Adslft-treated animals had minimal residual splenic tumors and liver metastases; in contrast, control animals had bulky splenic tumors and extensive liver metastases (p < 0.003). Second, mice with preestablished lung metastases showed a significant reduction in pulmonary metastases with regionally administered Adslft (intratracheal, p < 0.02) but not when the vector was systemically administered (intravenous, p > 0.9). Finally, mice with primary subcutaneous tumors treated with intratumoral administration of Adslft showed significant tumor suppression (p < 0.05) not observed in AdNull-treated mice or mice given Adslft intravenously (p > 0.3). We conclude that Ad-mediated in vivo regional delivery of a secreted form of the extracellular domain of the flt-1 VEGF receptor can effectively inhibit regional tumor growth, a strategy that may provide a means to control tumor growth within the treated organ without the risk of systemic antiangiogenesis.

Direct regeneration of cathode materials from spent lithium iron phosphate batteries using a solid phase sintering method

A direct regeneration of cathode materials from spent LiFePO₄ batteries using a solid phase sintering method has been proposed in this article.

"BPSA," a specific molecular form of free prostate-specific antigen, is found predominantly in the transition zone of patients with nodular benign prostatic hyperplasia

OBJECTIVES

The biologic mechanism for the increased proportion of noncomplexed ("free") prostate-specific antigen (PSA) found in the serum of patients with benign prostate disease is unknown. We recently reported that most of the PSA found in benign, hyperplastic, and cancerous prostatic tissue is in the free form. To determine whether specific molecular forms of free PSA are associated differentially with normal, hyperplastic, or cancerous prostatic tissue, we have further characterized the free PSA in each type of prostatic tissue.

METHODS

PSA was purified by immunoaffinity chromatography from matched prostatic tissue samples of peripheral zone cancer (PZ-C), PZ noncancer (PZ-N), and transition zone (TZ) tissue from 10 large-volume (greater than 50 g) and 8 small-volume (less than 25 g) radical prostatectomy specimens. Eight TZ specimens obtained during transurethral resection of the prostate for benign prostatic hyperplasia (BPH) were also analyzed. The different molecular forms of PSA were further resolved by high-performance hydrophobic interaction chromatography. Clipped forms of PSA were identified by N-terminal amino acid sequencing.

RESULTS

More than 99% of the PSA in prostatic tissues was in the free, noncomplexed form. Specimens from the prostate TZ were found to contain elevated levels of an altered form of PSA, which we designated BPSA. Purified BPSA contained a distinctive cleavage at lysine 182. The median percent BPSA (%BPSA) was 11.4 in the TZ of specimens with nodular BPH compared with a %BPSA of 4.1 in the TZ of specimens without nodular BPH (P <0.0014). The median %BPSA levels of the PZ-N and PZ-C tissues ranged from 3.2 to 4.9 and were not significantly different from one another or from the %BPSA level of TZ tissues without nodular BPH.

CONCLUSIONS

We have identified a specific molecular form of clipped free PSA, called BPSA, that is increased within the prostatic TZ of patients exhibiting nodular BPH. Higher levels of percent free PSA in serum have been found to correlate strongly with prostate volume, which in turn is closely associated with the progressive enlargement of nodular BPH tissue within the TZ of the prostate. Thus, it is possible that a proportion of the serum percent free PSA found in patients with BPH may be composed of BPSA released into the serum.

Photic signaling by cryptochrome in the Drosophila circadian system

Oscillations of the period (per) and timeless (tim) gene products are an integral part of the feedback loop that underlies circadian behavioral rhythms in Drosophila melanogaster. Resetting this loop in response to light requires the putative circadian photoreceptor cryptochrome (CRY). We dissected the early events in photic resetting by determining the mechanisms underlying the CRY response to light and by investigating the relationship between CRY and the light-induced ubiquitination of the TIM protein. In response to light, CRY is degraded by the proteasome through a mechanism that requires electron transport. Various CRY mutant proteins are not degraded, and this suggests that an intramolecular conversion is required for this light response. Light-induced TIM ubiquitination precedes CRY degradation and is increased when electron transport is blocked. Thus, inhibition of electron transport may "lock" CRY in an active state by preventing signaling required either to degrade CRY or to convert it to an inactive form. High levels of CRY block TIM ubiquitination, suggesting a mechanism by which light-driven changes in CRY could control TIM ubiquitination.

Tumor necrosis factor-alpha induces apoptosis via inducible nitric oxide synthase in neonatal mouse cardiomyocytes

OBJECTIVE

It has been demonstrated that tumor necrosis factor-alpha (TNF alpha) induces apoptosis in cardiac myocytes. However, its mechanism of action is still not well understood. In the present study, we hypothesized that TNF alpha induces myocardial apoptosis by induction of inducible nitric oxide synthase (iNOS).

METHODS

Neonatal cardiac myocytes were isolated from iNOS (-/-) mutant and C57BL6 wild type mice. Cells were cultured for 3 days before treatment with an NO donor or TNF alpha. Following treatment with S-nitroso-N-acetyl-penicillamine (SNAP) or TNF-alpha, cells were tested for apoptosis by terminal deoxynucleotidyl transfer-mediated end labeling (TUNEL) staining and cell death detection ELISA. NO production was measured by nitrite concentration in the culture medium. Cardiomyocyte expression of iNOS and TNF type 1 receptor (TNFR1) mRNA was determined by reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

SNAP (0.01-100 microM) induced apoptosis of cardiac myocytes in a concentration-dependent manner in the wild type mice (n = 5, P < 0.01). TNFR1 mRNA was expressed in neonatal cardiomyocytes from both wild type and iNOS (-/-) mutant mice. TNF alpha induced a concentration-dependent increase in iNOS mRNA expression and nitrite production as well as significant apoptosis of cardiomyocytes in the wild type mice (n = 4, P < 0.01). However, without iNOS expression, the apoptotic effects of TNF-alpha were significantly attenuated in cardiomyocytes from iNOS (-/-) mutant mice (n = 4, P < 0.05).

CONCLUSION

TNF alpha induces apoptosis via iNOS expression and NO production in neonatal mouse cardiomyocytes.

Rice endophyte Pantoea agglomerans YS19 promotes host plant growth and affects allocations of host photosynthates

AIMS

The aims of the study were to identify the effects of rice endophyte Pantoea agglomerans YS19 on host plant growth and allocations of photosynthates.

METHODS AND RESULTS

Endophytic diazotrophic YS19 showed nitrogen-fixing activity in N-free medium, and produced four categories of phytohormones which were indole-3-acetic acid, abscisic acid, gibberellic acid and cytokinin in Luria-Bertani medium. Inoculation of YS19 improved the biomass of the 12-day-cultivated host rice seedlings by 63.4% on N-free medium or by 18.7% on N-supplemented medium. Spraying of YS19 cell culture onto the rice plants at the premilk stage enhanced the transportation of the photosynthetic assimilation product from the source (flag leaves) to the sink (stachys) significantly. The formation of the plant sink was obviously inhibited when YS19 cell culture was applied at the late milk stage.

CONCLUSIONS

This research suggests that endophyte YS19 promotes host rice plant growth and affects allocations of host photosynthates.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings suggested that YS19 possesses the potential for increasing rice production in field application. Meanwhile, a suitable plant growth stage must be selected for the foliar spraying of YS19 cell culture.

Translocation of the B cell antigen receptor into lipid rafts reveals a novel step in signaling

The cross-linking of the B cell Ag receptor (BCR) leads to the initiation of a signal transduction cascade in which the earliest events involve the phosphorylation of the immunoreceptor tyrosine-based activation motifs of Ig alpha and Ig beta by the Src family kinase Lyn and association of the BCR with the actin cytoskeleton. However, the mechanism by which BCR cross-linking initiates the cascade remains obscure. In this study, using various A20-transfected cell lines, biochemical and genetic evidence is provided that BCR cross-linking leads to the translocation of the BCR into cholesterol- and sphingolipid-rich lipid rafts in a process that is independent of the initiation of BCR signaling and does not require the actin cytoskeleton. Translocation of the BCR into lipid rafts did not require the Ig alpha/Ig beta signaling complex, was not dependent on engagement of the FcR, and was not blocked by the Src family kinase inhibitor PP2 or the actin-depolymerizing agents cytochalasin D or latrunculin. Thus, cross-linking or oligomerization of the BCR induces the BCR translocation into lipid rafts, defining an event in B cell activation that precedes receptor phosphorylation and association with the actin cytoskeleton.

Role of Sec61alpha in the regulated transfer of the ribosome-nascent chain complex from the signal recognition particle to the translocation channel

Targeting of ribosome-nascent chain complexes to the translocon in the endoplasmic reticulum is mediated by the concerted action of the signal recognition particle (SRP) and the SRP receptor (SR). Ribosome-stripped microsomes were digested with proteases to sever cytoplasmic domains of SRalpha, SRbeta, TRAM, and the Sec61 complex. We characterized protein translocation intermediates that accumulate when Sec61alpha or SRbeta is inactivated by proteolysis. In the absence of a functional Sec61 complex, dissociation of SRP54 from the signal sequence is blocked. Experiments using SR proteoliposomes confirmed the assembly of a membrane-bound posttargeting intermediate. These results strongly suggest that the Sec61 complex regulates the GTP hydrolysis cycle of the SRP-SR complex at the stage of signal sequence dissociation from SRP54.