Dynamic 14-3-3/client protein interactions integrate survival and apoptotic pathways

Usnic Acid Targets 14-3-3 Proteins and Suppresses Cancer Progression by Blocking Substrate Interaction

The anticancer therapeutic effects of usnic acid (UA), a lichen secondary metabolite, have been demonstrated in vitro and in vivo. However, the mechanism underlying the anticancer effect of UA remains to be clarified. In this study, the target protein of UA was identified using a UA-linker-Affi-Gel molecule, which showed that UA binds to the 14-3-3 protein. UA binds to 14-3-3, causing the degradation of proteasomal and autophagosomal proteins. The interaction of UA with 14-3-3 isoforms modulated cell invasion, cell cycle progression, aerobic glycolysis, mitochondrial biogenesis, and the Akt/mTOR, JNK, STAT3, NF-κB, and AP-1 signaling pathways in colorectal cancer. A peptide inhibitor of 14-3-3 blocked or regressed the activity of UA and inhibited its effects. The results suggest that UA binds to 14-3-3 isoforms and suppresses cancer progression by affecting 14-3-3 targets and phosphorylated proteins.

High expression of 14-3-3ơ indicates poor prognosis and progression of lung adenocarcinoma

Lung adenocarcinoma (LUAD) is one of the leading causes of cancer-related death worldwide. 14-3-3ơ is an intracellular phosphoserine-binding protein that has been proposed to be involved in tumorigenesis. However, the biofunctional role of 14-3-3ơ and its clinicopathological/prognostic significance in LUAD have remained elusive. In the present study, western blot and immunohistochemical analyses of cancer tissues/cells and the corresponding normal controls were performed to verify that 14-3-3ơ was upregulated in LUAD. Univariate and multivariate logistic regression analysis indicated that high expression of 14-3-3ơ predicted poor overall survival and progression-free survival of patients with LUAD. Furthermore, in vivo and in vitro experiments demonstrated that overexpression of 14-3-3ơ markedly promoted cell proliferation, colony formation, anchorage-independent growth and tumor growth, whereas 14-3-3ơ depletion produced the opposite effects. Of note, 14-3-3ơ was identified as an independent prognostic factor for patients with LUAD. Collectively, the present results revealed that high expression of 14-3-3ơ may serve as an independent biomarker, contributing to poor prognosis and progression of LUAD.

Quercetin increases mitochondrial proteins (VDAC and SDH) and downmodulates AXL and PIM-1 tyrosine kinase receptors in NRAS melanoma cells

Melanoma is a type of skin cancer with low survival rates after it has metastasized. In order to find molecular differences that could represent targets of quercetin in anti-melanoma activity, we have chosen SKMEL-103 and SKMEL-28 melanoma cells and human melanocytes as models. Firstly, we observed that quercetin was able in reducing SKMEL-103 cell viability, but not in SKMEL-28. Besides that, quercetin treatment caused inhibition of AXL in both cell lines, but upregulation of PIM-1 in SKMEL-28 and downregulation in SKMEL-103. Moreover, HIF-1 alpha expression decreased in both cell lines. Interestingly, quercetin was more effective against SKMEL-103 than kinases inhibitors, such as Imatinib, Temsirolimus, U0126, and Erlotinib. Interestingly, we observed that while the levels of succinate dehydrogenase and voltage-dependent anion channel increased in SKMEL-103, both proteins were downregulated in SKMEL-28 after quercetin's treatment. Furthermore, AKT, AXL, PIM-1, ABL kinases were much more active and chaperones HSP90, HSP70 and GAPDH were highly expressed in SKMEL-103 cells in comparison with melanocytes. Our findings indicate, for the first time, that the efficacy of quercetin to kill melanoma cells depends on its ability in inhibiting tyrosine kinase and upregulating mitochondrial proteins, at least when SKMEL-103 and SKMEL-28 cells response were compared.

Tissue microarray profiling and integrative proteomics indicate the modulatory potential of Maytenus royleanus in inhibition of overexpressed TPD52 in prostate cancers

Maytenus roylanus (MEM) is a plant with anti-proliferative effects against prostate cancer. We aimed to explore the mechanism of action of MEM in prostate cancer (PCa) by employing an in vitro global proteome approach to get useful information of various signaling pathways and effected genes to define the mechanism of MEM action in prostate cancer. We conducted a global proteome analysis of CWR22Rv1after treatment with methanolic extract of MEM. The result of the proteomic profiling of in vitro PCa cells demonstrated the reduction in tumor protein D52 (TPD52) expression after treatment with methanolic extract of MEM. Down-regulation of TPD52 expression at mRNA level was observed by MEM treatment in CWR22Rν1 and C4-2 cells in a dose-dependent fashion probably by cleavage of Caspase 3 and PARP, or by modulation of cyclin-dependent kinases in CWR22Rν1 and C4-2 cells. The progressive character of the TRAMP model demonstrates a chance to evaluate the potential of chemo-preventive agents for both initial and late stages of prostate cancer development, and induction in TPD52 protein expression with development as well as the progression of prostate cancer was observed in the TRAMP model. Analyses of the tissue microarray collection of 25 specimens confirmed the clinical significance of our findings identifying TPD52 as a potential marker for PCa progression. We determined that knockdown of TPD52 (CWR22Rν1 cells), a considerable downregulation was seen at the protein level. Downregulation of TPD52 inhibited the migration and invasive behavior of prostate cancer cells as observed. Moreover, we observed that the siRNA-TPD52 transfection of CWR22Rν1 cells resulted in tumor growth inhibition with a marked reduction in the secretion of prostate-specific antigen (PSA) in the serum. Intraperitoneal injection of MEM considerably slowed tumor growth in athymic mice, inhibited TPD52 expression, and caused a marked reduction in PSA levels of serum as demonstrated by immunoblot screening and immune-histochemical staining. This report illustrates a molecular overview of pathological processes in PCa, indicating possible new disease biomarkers and therapeutic targets.

YWHAE/14-3-3ε expression impacts the protein load, contributing to proteasome inhibitor sensitivity in multiple myeloma

High protein load is a feature of multiple myeloma (MM), making the disease exquisitely sensitive to proteasome inhibitor (PIs). Despite the success of PIs in improving patient outcome, the majority of patients develop resistance leading to progressive disease; thus, the need to investigate the mechanisms driving the drug sensitivity vs resistance. With the well-recognized chaperone function of 14-3-3 proteins, we evaluated their role in affecting proteasome activity and sensitivity to PIs by correlating expression of individual 14-3-3 gene and their sensitivity to PIs (bortezomib and carfilzomib) across a large panel of MM cell lines. We observed a significant positive correlation between 14-3-3ε expression and PI response in addition to a role for 14-3-3ε in promoting translation initiation and protein synthesis in MM cells through binding and inhibition of the TSC1/TSC2 complex, as well as directly interacting with and promoting phosphorylation of mTORC1. 14-3-3ε depletion caused up to a 50% reduction in protein synthesis, including a decrease in the intracellular abundance and secretion of the light chains in MM cells, whereas 14-3-3ε overexpression or addback in knockout cells resulted in a marked upregulation of protein synthesis and protein load. Importantly, the correlation among 14-3-3ε expression, PI sensitivity, and protein load was observed in primary MM cells from 2 independent data sets, and its lower expression was associated with poor outcome in patients with MM receiving a bortezomib-based therapy. Altogether, these observations suggest that 14-3-3ε is a predictor of clinical outcome and may serve as a potential target to modulate PI sensitivity in MM.

Signaling Pathways That Control Apoptosis in Prostate Cancer

Prostate cancer is the second most common malignancy and the fifth leading cancer-caused death in men worldwide. Therapies that target the androgen receptor axis induce apoptosis in normal prostates and provide temporary relief for advanced disease, yet prostate cancer that acquired androgen independence (so called castration-resistant prostate cancer, CRPC) invariably progresses to lethal disease. There is accumulating evidence that androgen receptor signaling do not regulate apoptosis and proliferation in prostate epithelial cells in a cell-autonomous fashion. Instead, androgen receptor activation in stroma compartments induces expression of unknown paracrine factors that maintain homeostasis of the prostate epithelium. This paradigm calls for new studies to identify paracrine factors and signaling pathways that control the survival of normal epithelial cells and to determine which apoptosis regulatory molecules are targeted by these pathways. This review summarizes the recent progress in understanding the mechanism of apoptosis induced by androgen ablation in prostate epithelial cells with emphasis on the roles of BCL-2 family proteins and "druggable" signaling pathways that control these proteins. A summary of the clinical trials of inhibitors of anti-apoptotic signaling pathways is also provided. Evidently, better knowledge of the apoptosis regulation in prostate epithelial cells is needed to understand mechanisms of androgen-independence and implement life-extending therapies for CRPC.

Investigation and Functional Enrichment Analysis of the Human Host Interaction Network with Common Gram-Negative Respiratory Pathogens Predicts Possible Association with Lung Adenocarcinoma

Haemophilus influenzae (Hi), Moraxella catarrhalis (MorCa) and Pseudomonas aeruginosa (Psa) are three of the most common gram-negative bacteria responsible for human respiratory diseases. In this study, we aimed to identify, using the functional enrichment analysis (FEA), the human gene interaction network with the aforementioned bacteria in order to elucidate the full spectrum of induced pathogenicity. The Human Pathogen Interaction Database (HPIDB 3.0) was used to identify the human proteins that interact with the three pathogens. FEA was performed via the ToppFun tool of the ToppGene Suite and the GeneCodis database so as to identify enriched gene ontologies (GO) of biological processes (BP), cellular components (CC) and diseases. In total, 11 human proteins were found to interact with the bacterial pathogens. FEA of BP GOs revealed associations with mitochondrial membrane permeability relative to apoptotic pathways. FEA of CC GOs revealed associations with focal adhesion, cell junctions and exosomes. The most significantly enriched annotations in diseases and pathways were lung adenocarcinoma and cell cycle, respectively. Our results suggest that the Hi, MorCa and Psa pathogens could be related to the pathogenesis and/or progression of lung adenocarcinoma via the targeting of the epithelial cellular junctions and the subsequent deregulation of the cell adhesion and apoptotic pathways. These hypotheses should be experimentally validated.

Genetic Association Analysis of Cell Cycle Regulators Reveals YWHAZ Has Prognostic Significance in Prostate Cancer

BACKGROUND/AIM

This study aimed to identify the genes that cause biochemical recurrence (BCR) following radical prostatectomy (RP) in men with localized prostate cancer.

PATIENTS AND METHODS

A two-stage genetic association study of 19 single-nucleotide polymorphisms in 11 key cell cycle regulation genes was carried out. BCR-free survival after RP was evaluated in a discovery cohort of 458 patients with prostate cancer, and replication was investigated in another cohort of 185 patients.

RESULTS

A consistent association was found between BCR and rs2290291 (discovery: p=0.008; replication: p=0.029). rs2290291 is located in the tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein zeta (YWHAZ), and was predicted to possess a regulatory function that affected YWHAZ expression. Furthermore, YWHAZ expression was frequently up-regulated in advanced tumours, and associated with poorer survival in patients with prostate cancer.

CONCLUSION

YWHAZ rs2290291 was found to be associated with BCR. YWHAZ may function as a putative oncogene during prostate cancer progression.

Overexpression of 14-3-3σ Modulates Cholangiocarcinoma Cell Survival by PI3K/Akt Signaling

The protein 14-3-3σ is involved in numerous cellular processes through its ability to bind phosphorylated serine/threonine residues. It is a key regulator of the cell cycle involving in G2 arrest by p53. Deregulation of 14-3-3σ expression has been associated with a large variety of human cancers. However, its physiological function and therapeutic significance have rarely been investigated in cholangiocarcinoma. Using immunohistochemistry (IHC), we evaluated 14-3-3σ expression in 65 human extrahepatic cholangiocarcinomas. As a result, we found that 14-3-3σ is expressed in the tissue of 56 patients (86.2%), and its expression is positively correlated with tumor size, lymph node metastasis, and tumor stage. We also explored the significance of 14-3-3σ and found that 14-3-3σ exerts cell type-dependent effects on cell proliferation through PI3K/Akt signaling in both in vitro and in vivo xenograft models. These results suggest that 14-3-3σ assumes a constitutive role in tumorigenesis rather than acting as a cell cycle regulator in cholangiocarcinoma, which makes 14-3-3σ a new potential target for therapeutic intervention.

Excess active P13K rescues huntingtin-mediated neuronal cell death but has no effect on axonal transport defects

High levels of oxidative stress is detected in neurons affected by many neurodegenerative diseases, including huntington's disease. Many of these diseases also show neuronal cell death and axonal transport defects. While nuclear inclusions/accumulations likely cause cell death, we previously showed that cytoplasmic axonal accumulations can also contribute to neuronal death. However, the cellular mechanisms responsible for activating cell death is unclear. One possibility is that perturbations in normal axonal transport alter the function of the phosphatidylinositol 3-kinase (PI3K)-protein kinase B (AKT)-pathway, a signal transduction pathway that promotes survival/growth in response to extracellular signals. To test this proposal in vivo, we expressed active PI3K in the context of pathogenic huntingtin (HTT-138Q) in Drosophila larval nerves, which show axonal transport defects and neuronal cell death. We found that excess expression of active P13K significantly suppressed HTT-138Q-mediated neuronal cell death, but had no effect on HTT-138Q-mediated axonal transport defects. Expression of active PI3K also rescued Paraquat-mediated cell death. Further, increased levels of pSer9 (inactive) glycogen synthase kinase 3β was seen in HTT-138Q-mediated larval brains, and in dynein loss of function mutants, indicating the modulation of the pro-survival pathway. Intriguingly, proteins in the PI3K/AKT-pathway showed functional interactions with motor proteins. Taken together our observations suggest that proper axonal transport is likely essential for the normal function of the pro-survival PI3K/AKT-signaling pathway and for neuronal survival in vivo. These results have important implications for targeting therapeutics to early insults during neurodegeneration and death.

Screening of Differentially Expressed Microsporidia Genes from Nosema ceranae Infected Honey Bees by Suppression Subtractive Hybridization

The microsporidium Nosema ceranae is a high prevalent parasite of the European honey bee (Apis mellifera). This parasite is spreading across the world into its novel host. The developmental process, and some mechanisms of N. ceranae-infected honey bees, has been studied thoroughly; however, few studies have been carried out in the mechanism of gene expression in N. ceranae during the infection process. We therefore performed the suppressive subtractive hybridization (SSH) approach to investigate the candidate genes of N. ceranae during its infection process. All 96 clones of infected (forward) and non-infected (reverse) library were dipped onto the membrane for hybridization. A total of 112 differentially expressed sequence tags (ESTs) had been sequenced. For the host responses, 20% of ESTs (13 ESTs, 10 genes, and 1 non-coding RNA) from the forward library and 93.6% of ESTs (44 ESTs, 28 genes) from the reverse library were identified as differentially expressed genes (DEGs) of the hosts. A high percentage of DEGs involved in catalytic activity and metabolic processes revealed that the host gene expression change after N. ceranae infection might lead to an unbalance of physiological mechanism. Among the ESTs from the forward library, 75.4% ESTs (49 ESTs belonged to 24 genes) were identified as N. ceranae genes. Out of 24 N. ceranae genes, nine DEGs were subject to real-time quantitative reverse transcription PCR (real-time qRT-PCR) for validation. The results indicated that these genes were highly expressed during N. ceranae infection. Among nine N. ceranae genes, one N. ceranae gene (AAJ76_1600052943) showed the highest expression level after infection. These identified differentially expressed genes from this SSH could provide information about the pathological effects of N. ceranae. Validation of nine up-regulated N. ceranae genes reveal high potential for the detection of early nosemosis in the field and provide insight for further applications.

Expanding the genotype-phenotype correlation of de novo heterozygous missense variants in YWHAG as a cause of developmental and epileptic encephalopathy

Developmental and Epileptic encephalopathies (DEE) describe heterogeneous epilepsy syndromes, characterized by early-onset, refractory seizures and developmental delay (DD). Several DEE associated genes have been reported. With increased access to whole exome sequencing (WES), new candidate genes are being identified although there are fewer large cohort papers describing the clinical phenotype in such patients. We describe 6 unreported individuals and provide updated information on an additional previously reported individual with heterozygous de novo missense variants in YWHAG. We describe a syndromal phenotype, report 5 novel, and a recurrent p.Arg132Cys YWHAG variant and compare developmental trajectory and treatment strategies in this cohort. We provide further evidence of causality in YWHAG variants. WES was performed in five patients via Deciphering Developmental Disorders Study and the remaining two were identified via Genematcher and AnnEX databases. De novo variants identified from exome data were validated using Sanger sequencing. Seven out of seven patients in the cohort have de novo, heterozygous missense variants in YWHAG including 2/7 patients with a recurrent c.394C > T, p.Arg132Cys variant; 1/7 has a second, pathogenic variant in STAG1. Characteristic features included: early-onset seizures, predominantly generalized tonic-clonic and absence type (7/7) with good response to standard anti-epileptic medications; moderate DD; Intellectual Disability (ID) (5/7) and Autism Spectrum Disorder (3/7). De novo YWHAG missense variants cause EE, characterized by early-onset epilepsy, ID and DD, supporting the hypothesis that YWHAG loss-of-function causes a neurological phenotype. Although the exact mechanism of disease resulting from alterations in YWHAG is not fully known, it is possible that haploinsufficiency of YWHAG in developing cerebral cortex may lead to abnormal neuronal migration resulting in DEE.

Reversal of sorafenib resistance in hepatocellular carcinoma: epigenetically regulated disruption of 14-3-3η/hypoxia-inducible factor-1α

Sorafenib resistance is one of the main obstacles to the treatment of advanced/recurrent hepatocellular carcinoma (HCC). Here, sorafenib-resistant HCC cells and xenografts in nude mice were used as experimental models. A cohort of patients with advanced recurrent HCC who were receiving sorafenib therapy was used to assess the clinical significance of this therapy. Our data showed that 14-3-3η maintained sorafenib resistance in HCC. An analysis of the underlying molecular mechanisms revealed that 14-3-3η stabilizes hypoxia-inducible factor 1α (HIF-1α) through the inhibition of ubiquitin-dependent proteasome protein degradation, which leads to the maintenance of cancer stem cell (CSC) properties. We further found that microRNA-16 (miR-16) is a competent miRNA that reverses sorafenib resistance by targeting the 3'-UTR of 14-3-3η and thereby inhibits 14-3-3η/HIF-1α/CSC properties. In HCC patients, significant negative correlations were found between the expression of miR-16 and 14-3-3η, HIF-1α, or CSC properties. Further analysis showed that low miR-16 expression but high 14-3-3η expression can prognosticate sorafenib resistance and poor survival. Collectively, our present study indicated that miR-16/14-3-3η is involved in sorafenib resistance in HCC and that these two factors could be potential therapeutic targets and biomarkers for predicting the response to sorafenib treatment.

Differentially expressed mRNAs, proteins and miRNAs associated to energy metabolism in skeletal muscle of beef cattle identified for low and high residual feed intake

Background

Feed efficiency is one of the most important parameters that affect beef production costs. The energy metabolism of skeletal muscle greatly contributes to variations in feed efficiency. However, information regarding differences in proteins involved in the energy metabolism of the skeletal muscle in beef cattle divergently identified for feed efficiency is scarce. In this study, we aimed to investigate energy metabolism of skeletal muscle of Nellore beef cattle, identified for low and high residual feed intake using a proteomics approach. We further assessed the expression of candidate microRNAs as a one of the possible mechanisms controlling the biosynthesis of the proteins involved in energy metabolism that were differentially abundant between high and low residual feed intake animals.

Results

A greater abundance of 14–3-3 protein epsilon (P = 0.01) was observed in skeletal muscle of residual feed intake (RFI) high animals (RFI-High). Conversely, a greater abundance of Heat Shock Protein Beta 1 (P < 0.01) was observed in the skeletal muscle of RFI-Low cattle. A greater mRNA expression of YWHAE, which encodes the 14–3-3 protein epsilon, was also observed in the skeletal muscle of RFI-High animals (P = 0.01). A lower mRNA expression of HSPB1, which encodes the Heat Shock Protein Beta 1, was observed in the skeletal muscle of RFI-High animals (P = 0.01). The miR-665 was identified as a potential regulator of the 14–3-3 protein epsilon, and its expression was greater in RFI-Low animals (P < .001). A greater expression of miR-34a (P = 0.01) and miR-2899 (P < .001) was observed in the skeletal muscle of RFI-High animals, as both miRNAs were identified as potential regulators of HSPB1 expression.

Conclusion

Our results show that Nellore cattle divergently identified for feed efficiency by RFI present changes in the abundance of proteins involved in energy expenditure in skeletal muscle. Moreover, our data point towards that miR-665, miR34a and miR-2899 are likely involved in controlling both 14-3-3 epsilon and HSPB1 proteins identified as differentially abundant in the skeletal muscle of RFI-High and RFI-Low Nellore cattle.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5890-z) contains supplementary material, which is available to authorized users.

14-3-3ζ promotes gliomas cells invasion by regulating Snail through the PI3K/AKT signaling

14-3-3ζ has been reported to function as critical regulators of diverse cellular responses. However, the role of 14-3-3ζ in gliomas progression remains largely unknown. The expression level of 14-3-3ζ and Snail was detected by Western blot analysis and quantitative polymerase chain reaction in different grades of human gliomas. The effect of 14-3-3ζ on gliomas progression was measured using cell migration and invasion assay, the colony formation experiment, and CCK-8 assay. The effect of 14-3-3ζ on PI3K/AKT/Snail signaling protein expression levels was tested by Western blotting. Firstly, 14-3-3ζ was often up-regulated in high-grade gliomas relative to low-grade gliomas, and this overexpression was significantly related to tumor size, Karnofsky Performance Scale score and weaker disease-free survival. Secondly, the overexpression of 14-3-3ζ promoted gliomas cells proliferation, migration, and invasion. Conversely, the knockdown of 14-3-3ζ suppressed gliomas cells proliferation, migration, and invasion. Furthermore, subsequent mechanistic studies showed that 14-3-3ζ could activate PI3K/AKT/Snail signaling pathway to facilitate gliomas cells proliferation, migration, and invasion. This study shows that the overexpression of 14-3-3ζ can promote remarkably gliomas cells proliferation, migration, and invasion by regulating the Snail protein expression through activating PI3K/AKT signaling, and it may serve as a potential prognostic marker and therapeutic target for gliomas.

3D Cultures of Parkinson's Disease-Specific Dopaminergic Neurons for High Content Phenotyping and Drug Testing

Parkinson's disease (PD)-specific neurons, grown in standard 2D cultures, typically only display weak endophenotypes. The cultivation of PD patient-specific neurons, derived from induced pluripotent stem cells carrying the LRRK2-G2019S mutation, is optimized in 3D microfluidics. The automated image analysis algorithms are implemented to enable pharmacophenomics in disease-relevant conditions. In contrast to 2D cultures, this 3D approach reveals robust endophenotypes. High-content imaging data show decreased dopaminergic differentiation and branching complexity, altered mitochondrial morphology, and increased cell death in LRRK2-G2019S neurons compared to isogenic lines without using stressor agents. Treatment with the LRRK2 inhibitor 2 (Inh2) rescues LRRK2-G2019S-dependent dopaminergic phenotypes. Strikingly, a holistic analysis of all studied features shows that the genetic background of the PD patients, and not the LRRK2-G2019S mutation, constitutes the strongest contribution to the phenotypes. These data support the use of advanced in vitro models for future patient stratification and personalized drug development.

14-3-3 Proteins Reduce Cell-to-Cell Transfer and Propagation of Pathogenic α-Synuclein

α-Synuclein (αsyn) is the key protein that forms neuronal aggregates in the neurodegenerative disorders Parkinson's disease (PD) and dementia with Lewy bodies. Recent evidence points to the prion-like spread of αsyn from one brain region to another. Propagation of αsyn is likely dependent on release, uptake, and misfolding. Under normal circumstances, this highly expressed brain protein functions normally without promoting pathology, yet the underlying endogenous mechanisms that prevent αsyn spread are not understood. 14-3-3 proteins are highly expressed brain proteins that have chaperone function and regulate protein trafficking. In this study, we investigated the potential role of the 14-3-3 proteins in the regulation of αsyn spread using two models of αsyn spread. In a paracrine αsyn model, 14-3-3θ promoted release of αsyn complexed with 14-3-3θ. Despite higher amounts of released αsyn, extracellular αsyn showed reduced oligomerization and seeding capability, reduced internalization, and reduced toxicity in primary mixed-gender mouse neurons. 14-3-3 inhibition reduced the amount of αsyn released, yet released αsyn was more toxic and demonstrated increased oligomerization, seeding capability, and internalization. In the preformed fibril model, 14-3-3 θ reduced αsyn aggregation and neuronal death, whereas 14-3-3 inhibition enhanced αsyn aggregation and neuronal death in primary mouse neurons. 14-3-3s blocked αsyn spread to distal chamber neurons not exposed directly to fibrils in multichamber, microfluidic devices. These findings point to 14-3-3s as a direct regulator of αsyn propagation, and suggest that dysfunction of 14-3-3 function may promote αsyn pathology in PD and related synucleinopathies.SIGNIFICANCE STATEMENT Transfer of misfolded aggregates of α-synuclein from one brain region to another is implicated in the pathogenesis of Parkinson's disease and other synucleinopathies. This process is dependent on active release, internalization, and misfolding of α-synuclein. 14-3-3 proteins are highly expressed chaperone proteins that interact with α-synuclein and regulate protein trafficking. We used two different models in which toxicity is associated with cell-to-cell transfer of α-synuclein to test whether 14-3-3s impact α-synuclein toxicity. We demonstrate that 14-3-3θ reduces α-synuclein transfer and toxicity by inhibiting oligomerization, seeding capability, and internalization of α-synuclein, whereas 14-3-3 inhibition accelerates the transfer and toxicity of α-synuclein in these models. Dysfunction of 14-3-3 function may be a critical mechanism by which α-synuclein propagation occurs in disease.

IL-4 enhances survival of in vitro-differentiated mouse basophils through transcription-independent signaling downstream of PI3K

Interleukin 4 (IL-4) is a critical cytokine implicated with T_H2 immune reactions, which are linked to pathologic conditions of allergic diseases. In that context, the initiation of T_H2 responses can critically depend on early basophil-derived IL-4 to activate T-cell responses, which then amplify IL-4 secretion. As a pleiotropic cytokine, IL-4 acts on a broad variety of hematopoietic and non-hematopoietic cells. However, the effect of IL-4 on basophils themselves, which are emerging as relevant players in allergic as well as autoimmune diseases, was only scarcely addressed so far. Here we used in vitro-differentiated mouse basophils to investigate the direct effects of IL-4 on cellular viability and surface expression of the high-affinity receptor for IgE, FcεRI. We observed that IL-4 elicits pronounced pro-survival signaling in basophils, delaying spontaneous apoptosis in vitro to a degree comparable to the known pro-survival effects of IL-3. Our data indicate that IL-4-mediated survival depends on PI3K/AKT signaling and—in contrast to IL-3—seems to be largely independent of transcriptional changes but effectuated by post-translational mechanisms affecting BCL-2 family members among others. Additionally, we found that IL-4 signaling has a stabilizing effect on the surface expression levels of the critical basophil activation receptor FcεRI. In summary, our findings indicate an important regulatory role of IL-4 on in vitro-differentiated mouse basophils enhancing their survival and stabilizing FcεRI receptor expression through PI3K-dependent signaling. A better understanding of the regulation of basophil survival will help to define promising targets and consequently treatment strategies in basophil-driven diseases.

Leucine-Rich Repeat Kinase 2 in Parkinson's Disease: Updated from Pathogenesis to Potential Therapeutic Target

BACKGROUND

Parkinson's disease (PD) is characterized by the selective loss of dopaminergic neurons in the midbrain. The pathogenesis of PD is not fully understood but is likely caused by a combination of genetic and environmental factors. Several genes are associated with the onset and progression of familial PD. There is increasing evidence that leucine-rich repeat kinase 2 (LRRK2) plays a significant role in PD pathophysiology.

SUMMARY

Many studies have been conducted to elucidate the functions of LRRK2 and identify effective LRRK2 inhibitors for PD treatment. In this review, we discuss the role of LRRK2 in PD and recent progress in the use of LRRK2 inhibitors as therapeutic agents. Key Messages: LRRK2 plays a significant role in the pathophysiology of PD, and pharmacological inhibition of LRRK2 has become one of the most promising potential therapies for PD. Further research is warranted to determine the functions of LRRK2 and expand the applications of LRRK2 inhibitors in PD treatment.

14-3-3 proteins in platelet biology and glycoprotein Ib-IX signaling

Members of the 14-3-3 family of proteins function as adapters/modulators that recognize phosphoserine/phosphothreonine-based binding motifs in many intracellular proteins and play fundamental roles in signal transduction pathways of eukaryotic cells. In platelets, 14-3-3 plays a wide range of regulatory roles in phosphorylation-dependent signaling pathways, including G-protein signaling, cAMP signaling, agonist-induced phosphatidylserine exposure, and regulation of mitochondrial function. In particular, 14-3-3 interacts with several phosphoserine-dependent binding sites in the major platelet adhesion receptor, the glycoprotein Ib-IX complex (GPIb-IX), regulating its interaction with von Willebrand factor (VWF) and mediating VWF/GPIb-IX-dependent mechanosignal transduction, leading to platelet activation. The interaction of 14-3-3 with GPIb-IX also plays a critical role in enabling the platelet response to low concentrations of thrombin through cooperative signaling mediated by protease-activated receptors and GPIb-IX. The various functions of 14-3-3 in platelets suggest that it is a possible target for the treatment of thrombosis and inflammation.

A proteomic approach to elucidate the multiple targets of selenium-induced cell-growth inhibition in human lung cancer

BACKGROUND

  Methylseleninic acid (MSA) has been implicated as a promising anticancer agent for lung cancer. However, the underlying molecular mechanism(s) responsible for MSA's action is not well understood. Our study aimed to examine the cellular effects of MSA on L9981 human high-metastatic large cell lung cancer cells and gain insights into its possible molecular mechanism(s) through a proteomic approach.

METHODS

  L9981 cells were exposed to MSA at different concentrations and time points. The effects of MSA on cell proliferation and apoptosis were detected by cell viability analyzer Vi-CELL and flow cytometric analysis, respectively. We analyzed the alterations in the proteome profile of L9981 cells induced by MSA using the 2-D difference in gel electrophoresis (2-D DIGE) and identified the differentially expressed proteins using a liquid chromatography system followed by tandem mass spectrometry (LC-MS/MS).

RESULTS

  We found that MSA inhibited cell proliferation in a dose-dependent manner and significantly induced early apoptosis in L9981 cells. 2-D DIGE showed that MSA induced significant changes (>1.29 fold) in the expression levels of 42 protein spots compared to the untreated control (P < 0.05). As identified by LC-MS/MS, proteins that underwent changes in response to MSA were related to various biological functions, including: (i) endoplasmic reticulum stress (upregulation of molecular chaperones like heat shock protein A5, protein disulfide-isomerase precursor, and calreticulin precursor); (ii) oxidative stress response/ thioredoxin system (decreased thioredoxin-like protein 1 and increased thioredoxin reductase 1); (iii) translation regulation (downregulation of translation factors like elongation factor 1-beta and eukaryotic translation initiation factor 6); (iv) mitochondrial bioenergetic function (upregulation of adenosine triphosphate synthase subunit beta and mitochondria); and (v) cell signal transduction regulation (decreased peptidyl-prolyl cis-trans isomerase A and 14-3-3 protein gamma). The protein and gene expression levels of those proteins of interest were further confirmed by Western blot and/or real-time reverse transcription polymerase chain reaction.

CONCLUSION

  Our results suggest that MSA may inhibit cell proliferation and induce apoptosis in lung cancer by modulating multiple targets involved in various crucial cellular processes.

14-3-3ζ/TGFβR1 promotes tumor metastasis in lung squamous cell carcinoma

14-3-3ζ is involved in tumor cell growth and apoptosis. However, the mechanism of 14-3-3ζ in lung squamous cell carcinoma (SCC) metastasis has not been illuminated. In our studies, we found that the expression of 14-3-3ζ was highly expressed in lung SCC compared to normal lung tissues. High expression of 14-3-3ζ was associated with pTNM stage (p<0.05) and lymph node metastasis (p<0.05). Furthermore, the expression of 14-3-3ζ protein was associated with high levels of TGFβR1 protein (p=0.005), and pSMAD3 (p=0.033). Lung SCC patients with high 14-3-3ζ expression have significantly shorter OS and DFS compared to patients with low 14-3-3ζ expression. Additionally, 14-3-3ζ knockdown inhibited cell proliferation, migratory and invasive properties of human lung SCC cells. TGFβR1 was involved in 14-3-3ζ-mediated cell proliferation and metastasis of lung SCC cells. Additionally, sh-14-3-3ζ can suppress tumor growth and metastasis in vivo. Thus, these data provide the evidence that 14-3-3ζ promote tumor metastasis and might be a prognostic biomarker and target for therapeutic strategy in lung SCC.

LRRK2 Phosphorylation: Behind the Scenes

Mutations in the gene encoding leucine-rich repeat kinase 2 (LRRK2) are known today as the most common genetic cause of Parkinson's disease (PD). LRRK2 is a large protein that is hypothesized to regulate other proteins as a scaffold in downstream signaling pathways. This is supported by the multiple domain composition of LRRK2 with several protein-protein interaction domains combined with kinase and GTPase activity. LRRK2 is highly phosphorylated at sites that are strictly controlled by upstream regulators, including its own kinase domain. In cultured cells, most pathogenic mutants display increased autophosphorylation at S1292, but decreased phosphorylation at sites controlled by other kinases. We only begin to understand how LRRK2 phosphorylation is regulated and how this impacts its physiological and pathological function. Intriguingly, LRRK2 kinase inhibition, currently one of the most prevailing disease-modifying therapeutic strategies for PD, induces LRRK2 dephosphorylation at sites that are also dephosphorylated in pathogenic variants. In addition, LRRK2 kinase inhibition can induce LRRK2 protein degradation, which might be related to the observed inhibitor-induced adverse effects on the lung in rodents and non-human primates, as it resembles the lung pathology in LRRK2 knock-out animals. In this review, we will provide an overview of how LRRK2 phosphorylation is regulated and how this complex regulation relates to several molecular and cellular features of LRRK2.

14-3-3ε is a nuclear matrix protein, and its altered expression and localization are associated with curcumin-induced apoptosis of MG-63 cells

The 14-3-3 protein family may regulates protein interaction, transportation and cellular localization. The regulatory role of 14-3-3ε is influenced by its altered localization. In the present study, human osteosarcoma MG-63 cells were treated with curcumin to induce apoptosis. Subsequently, the altered expression and localization of 14-3-3ε and its co-localization with other apoptosis-associated proteins during apoptosis was investigated. Analysis of nuclear matrix proteins (NMPs), using two-dimensional gel electrophoresis with matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry, revealed that 14-3-3ε existed on the nuclear matrix of MG-63 cells, and its expression was decreased compared with that in control cells following curcumin treatment. In addition, western blot analysis validated that the expression level of 14-3-3ε was downregulated during curcumin-induced apoptosis of MG-63 cells compared with that in control cells. Using immunofluorescence labeling, it was observed that 14-3-3ε was located on the nuclear matrix of MG-63 cells and the distribution of 14-3-3ε on the nuclear matrix was decreased following treatment with curcumin, compared with that in control cells. Double immunofluorescence staining and laser-scanning confocal microscopy demonstrated that 14-3-3ε was co-localized with B-cell lymphoma-2 (Bcl-2), Bcl-2-associated-X protein, p53 and c-FOS transcription factor in MG-63 cells. Furthermore, following treatment with curcumin, these co-localization regions were decreased. The results of the present study revealed that 14-3-3ε is an NMP in MG-63 cells, and its altered expression and co-localization with apoptosis-associated proteins indicated an important function of 14-3-3ε in apoptosis of MG-63 cells. Additional studies are required to investigate the results of the present study.

Long non-coding RNA HOX transcript antisense RNA promotes expression of 14-3-3σ in non-small cell lung cancer

Evidence suggests that both 14-3-3σ and long non-coding RNA HOX transcript antisense RNA (HOTAIR) are involved in the tumorigenesis and progression of lung cancer. In the present study, the potential association between 14-3-3σ and HOTAIR in non-small cell lung cancer (NSCLC) was investigated. In tissue samples collected from 54 patients with NSCLC, expression of HOTAIR and 14-3-3σ was analyzed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). After stable ectopic expression of HOTAIR and stable HOTAIR knockdown in PC9 cancer cells, the effect of HOTAIR on levels of mRNA and protein 14-3-3σ expression levels were detected using RT-qPCR and western blotting, respectively. Expression of HOTAIR and 14-3-3σ in NSCLC tissues was significantly higher than in adjacent non-cancerous lung tissue (P<0.05). Correlation analysis also identified a correlation between levels of HOTAIR and 14-3-3σ expression in NSCLC tissues (r=0.725, P=0.0005). In addition, overexpression and knockdown of HOTAIR in the human NSCLC cell line PC9 led to the upregulation and downregulation of 14-3-3σ, respectively, at both the mRNA and protein levels (all P<0.05). To the best of our knowledge, the present study provides the first in vivo and in vitro evidence to suggest that HOTAIR promotes the expression of 14-3-3σ in NSCLC. The potential association between HOTAIR and 14-3-3σ indicates that both biomolecules may be viable targets in anticancer therapy.

Dysregulation of 14-3-3 proteins in neurodegenerative diseases with Lewy body or Alzheimer pathology

Objective

The highly conserved 14‐3‐3 proteins interact with key players involved in Parkinson's disease (PD) and other neurodegenerative disorders. We recently demonstrated that 14‐3‐3 phosphorylation is increased in PD models and that increased 14‐3‐3 phosphorylation reduces the neuroprotective effects of 14‐3‐3 proteins. Here, we investigated whether 14‐3‐3 phosphorylation is altered in postmortem brains from control, PD, Alzheimer's Disease (AD), Alzheimer's with Lewy Bodies (ADLB), Dementia with Lewy Bodies (DLB), and Progressive Supranuclear Palsy (PSP) subjects at three conserved sites: serine 58 (S58), serine 185 (S185), and serine 232 (S232).

Methods

S58, S185, and S232 phosphorylation was measured by western blot analysis of Triton X‐100 soluble and insoluble fractions from postmortem temporal cortex.

Results

The ratio of soluble phospho‐S232 to insoluble phospho‐S232 was reduced by 32%, 60%, 37%, and 52% in PD, AD, ADLB, and DLB, respectively. S185 and S58 phosphorylation were mildly elevated in the soluble fraction in DLB. We also noted a dramatic reduction in soluble pan 14‐3‐3 levels by ~35% in AD, ADLB, and DLB. Lower ratios of soluble to insoluble S232 phosphorylation (pointing to higher insoluble pS232) correlated with lower soluble pan 14‐3‐3 levels, suggesting that S232 phosphorylation may promote insolubilization of 14‐3‐3s. The phospho‐S232 ratio and soluble pan 14‐3‐3 levels correlated with clinical and pathological severity.

Interpretation

These data reveal dysregulation of 14‐3‐3 proteins in neurodegeneration associated with Lewy body or Alzheimer pathology. S232 phosphorylation may drive insolubilization of 14‐3‐3s and thus contribute to the pathophysiology in neurodegenerative disorders associated with Lewy body or Alzheimer pathology.

Meiotic failure in cyclin A1-deficient mouse spermatocytes triggers apoptosis through intrinsic and extrinsic signaling pathways and 14-3-3 proteins

Cyclin A1 (Ccna1), a member of the mammalian A type cyclins, is most abundantly expressed in spermatocytes and is essential for spermatogenesis in the mouse. Ccna1- deficient spermatocytes arrest at late meiotic prophase and undergo apoptosis. To further delineate the mechanisms and key factors involved in this process, we have examined changes in expression of genes involved in both intrinsic and extrinsic signaling pathways that trigger apoptosis in the mutant spermatocytes. Our results show that both pathways are involved, and that the factors involved in the intrinsic pathway were expressed earlier than those involved in the extrinsic pathway. We have also begun to identify in vivo Ccna1-interacting proteins, using an unbiased biochemical approach, and identified 14-3-3, a key regulator of apoptosis, as a Ccna1-interacting protein. Expression levels of 14-3-3 proteins remain unchanged between wild type and mutant testes but there were differences in the subcellular distribution. In wild type control, 14-3-3 is detected in both cytosolic and nuclear fractions whereas it is restricted to the cytoplasm in mutant testes. This differential distribution of 14-3-3 may contribute to the induction of apoptosis in Ccna1-deficient spermatocytes. These results provide insight into the apoptotic mechanisms and pathways that are triggered when progression through the meiotic cell cycle is defective in male gametogenesis.

Low dose perfluorooctanoate exposure promotes cell proliferation in a human non-tumor liver cell line

Perfluorooctanoate (PFOA) is a well-known persistent organic pollutant widely found in the environment, wildlife and humans. Medical surveillance and experimental studies have investigated the potential effects of PFOA on human livers, but the hepatotoxicity of PFOA on humans and its underlying mechanism remain to be clarified. We exposed a human liver cell line (HL-7702) to 50μM PFOA for 48h and 96h, and identified 111 significantly differentially expressed proteins by iTRAQ analysis. A total of 46 proteins were related to cell proliferation and apoptosis. Through further analysis of the cell cycle, apoptosis and their related proteins, we found that low doses of PFOA (50-100μM) promoted cell proliferation and numbers by promoting cells from the G1 to S phases, whereas high doses of PFOA (200-400μM) led to reduced HL-7702 cell numbers compared with that of the control mainly due to cell cycle arrest in the G0/G1 phase. To our knowledge, this is the first report on the promotion of cell cycle progression in human cells following PFOA exposure.

Phosphomimetic mutation of a conserved serine residue in Arabidopsis thaliana 14-3-3ω suggests a regulatory role of phosphorylation in dimerization and target interactions

14-3-3s are evolutionarily conserved eukaryotic regulatory proteins that are involved in diverse biological processes. The common mode of action for the 14-3-3 proteins is through the binding of phosphorylated target proteins. In many species, multiple 14-3-3 isoforms exist and these different isoforms can exhibit distinct ranges of target interactions. The dimerization of 14-3-3s is central to their function. 14-3-3 isoforms can form different combinations of homo- and heterodimers, which contribute to the broad functional diversity of the family. In this study, we showed that phosphomimetic mutation of a conserved serine residue in the dimerization interface of 14-3-3 isoforms, Ser-62, not only affects the ability of Arabidopsis 14-3-3ω to form homodimers, but alters the range of 14-3-3 family members with which it can form heterodimers. Furthermore, we demonstrated that the phosphorylation status of Ser-62 can regulate the binding of 14-3-3ω to target proteins, suggesting that Ser-62 might be a conserved key element to modulate target binding in both plants and animals.

14-3-3 Proteins regulate mutant LRRK2 kinase activity and neurite shortening

Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common known cause of inherited Parkinson's disease (PD), and LRRK2 is a risk factor for idiopathic PD. How LRRK2 function is regulated is not well understood. Recently, the highly conserved 14-3-3 proteins, which play a key role in many cellular functions including cell death, have been shown to interact with LRRK2. In this study, we investigated whether 14-3-3s can regulate mutant LRRK2-induced neurite shortening and kinase activity. In the presence of 14-3-3θ overexpression, neurite length of primary neurons from BAC transgenic G2019S-LRRK2 mice returned back to wild-type levels. Similarly, 14-3-3θ overexpression reversed neurite shortening in neuronal cultures from BAC transgenic R1441G-LRRK2 mice. Conversely, inhibition of 14-3-3s by the pan-14-3-3 inhibitor difopein or dominant-negative 14-3-3θ further reduced neurite length in G2019S-LRRK2 cultures. Since G2019S-LRRK2 toxicity is likely mediated through increased kinase activity, we examined 14-3-3θ's effects on LRRK2 kinase activity. 14-3-3θ overexpression reduced the kinase activity of G2019S-LRRK2, while difopein promoted the kinase activity of G2019S-LRRK2. The ability of 14-3-3θ to reduce LRRK2 kinase activity required direct binding of 14-3-3θ with LRRK2. The potentiation of neurite shortening by difopein in G2019S-LRRK2 neurons was reversed by LRRK2 kinase inhibitors. Taken together, we conclude that 14-3-3θ can regulate LRRK2 and reduce the toxicity of mutant LRRK2 through a reduction of kinase activity.

Klotho Regulates 14-3-3ζ Monomerization and Binding to the ASK1 Signaling Complex in Response to Oxidative Stress

The reactive oxygen species (ROS)-sensitive apoptosis signal-regulating kinase 1 (ASK1) signaling complex is a key regulator of p38 MAPK activity, a major modulator of stress-associated with aging disorders. We recently reported that the ratio of free ASK1 to the complex-bound ASK1 is significantly decreased in Klotho-responsive manner and that Klotho-deficient tissues have elevated levels of free ASK1 which coincides with increased oxidative stress. Here, we tested the hypothesis that: 1) covalent interactions exist among three identified proteins constituting the ASK1 signaling complex; 2) in normal unstressed cells the ASK1, 14-3-3ζ and thioredoxin (Trx) proteins simultaneously engage in a tripartite complex formation; 3) Klotho's stabilizing effect on the complex relied solely on 14-3-3ζ expression and its apparent phosphorylation and dimerization changes. To verify the hypothesis, we performed 14-3-3ζ siRNA knock-down experiments in conjunction with cell-based assays to measure ASK1-client protein interactions in the presence and absence of Klotho, and with or without an oxidant such as rotenone. Our results show that Klotho activity induces posttranslational modifications in the complex targeting 14-3-3ζ monomer/dimer changes to effectively protect against ASK1 oxidation and dissociation. This is the first observation implicating all three proteins constituting the ASK1 signaling complex in close proximity.

14-3-3 inhibition promotes dopaminergic neuron loss and 14-3-3θ overexpression promotes recovery in the MPTP mouse model of Parkinson's disease

14-3-3s are a highly conserved protein family that plays important roles in cell survival and interact with several proteins implicated in Parkinson's disease (PD). Disruption of 14-3-3 expression and function has been implicated in the pathogenesis of PD. We have previously shown that increasing the expression level of 14-3-3θ is protective against rotenone and 1-methyl-4-phenylpyridinium (MPP(+)) in cultured cells. Here, we extend our studies to examine the effects of 14-3-3s in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. We first investigated whether targeted nigral 14-3-3θ overexpression mediated by adeno-associated virus offers neuroprotection against MPTP-induced toxicity. 14-3-3θ overexpression using this approach did not reduce MPTP-induced dopaminergic cell loss in the substantia nigra nor the depletion of dopamine (DA) and its metabolites in the striatum at three weeks after MPTP administration. However, 14-3-3θ-overexpressing mice showed a later partial recovery in striatal DA metabolites at eight weeks after MPTP administration compared to controls, suggesting that 14-3-3θ overexpression may help in the functional recovery of those dopaminergic neurons that survive. Conversely, we investigated whether disrupting 14-3-3 function in transgenic mice expressing the pan 14-3-3 inhibitor difopein exacerbates MPTP-induced toxicity. We found that difopein expression promoted dopaminergic cell loss in response to MPTP treatment. Together, these findings suggest that 14-3-3θ overexpression promotes recovery of DA metabolites whereas 14-3-3 inhibition exacerbates neuron loss in the MPTP mouse model of PD.

Physiological, pathological, and structural implications of non-enzymatic protein-protein interactions of the multifunctional human transglutaminase 2

Transglutaminase 2 (TG2) is a ubiquitously expressed member of an enzyme family catalyzing Ca(2+)-dependent transamidation of proteins. It is a multifunctional protein having several well-defined enzymatic (GTP binding and hydrolysis, protein disulfide isomerase, and protein kinase activities) and non-enzymatic (multiple interactions in protein scaffolds) functions. Unlike its enzymatic interactions, the significance of TG2's non-enzymatic regulation of its activities has recently gained importance. In this review, we summarize all the partners that directly interact with TG2 in a non-enzymatic manner and analyze how these interactions could modulate the crosslinking activity and cellular functions of TG2 in different cell compartments. We have found that TG2 mostly acts as a scaffold to bridge various proteins, leading to different functional outcomes. We have also studied how specific structural features, such as intrinsically disordered regions and embedded short linear motifs contribute to multifunctionality of TG2. Conformational diversity of intrinsically disordered regions enables them to interact with multiple partners, which can result in different biological outcomes. Indeed, ID regions in TG2 were identified in functionally relevant locations, indicating that they could facilitate conformational transitions towards the catalytically competent form. We reason that these structural features contribute to modulating the physiological and pathological functions of TG2 and could provide a new direction for detecting unique regulatory partners. Additionally, we have assembled all known anti-TG2 antibodies and have discussed their significance as a toolbox for identifying and confirming novel TG2 regulatory functions.

Proteomic changes occurring in the malaria mosquitoes Anopheles gambiae and Anopheles stephensi during aging

The age of mosquitoes is a crucial determinant of their ability to transmit pathogens and their resistance to insecticides. We investigated changes to the abundance of proteins found in heads and thoraces of the malaria mosquitoes Anopheles gambiae and Anopheles stephensi as they aged. Protein expression changes were assessed using two-dimensional difference gel electrophoresis and the identity of differentially expressed proteins was determined by using either matrix-assisted laser desorption ionization tandem time-of-flight mass spectrometry or capillary high-pressure liquid chromatography coupled with a linear ion-trap (LTQ)-Orbitrap XL hybrid mass spectrometer. Protein biomarkers were validated by semi quantitative Western blot analysis. Nineteen and nine age dependent protein spots were identified for A. stephensi and A. gambiae, respectively. Among the proteins down-regulated with age were homologs of ADF/Cofilin, cytochome c1, heat shock protein-70 and eukaryotic translation initiation factor 5A (eIF5a). Proteins up-regulated with age included probable methylmalonate-semialdehyde dehydrogenase, voltage-dependent anion-selective channel and fructose bisphosphate aldolase. Semi quantitative Western blot analysis confirmed expression patterns observed by 2-D DIGE for eIF5a and ADF/Cofilin. Further work is recommended to determine whether these biomarkers are robust to infection, blood feeding and insecticide resistance. Robust biomarkers could then be incorporated into rapid diagnostic assays for ecological and epidemiological studies.

BIOLOGICAL SIGNIFICANCE

In this study, we have identified several proteins with characteristic changes in abundance in both A. gambiae and A. stephensi during their aging process. These changes may highlight underlying mechanisms beneath the relationship between mosquito age and factors affecting Plasmodium transmission and mosquito control. The similarity of changes in protein abundance between these species and the primary dengue vector Aedes aegypti, has revealed conserved patterns of aging-specific protein regulation.

Destabilisation of dimeric 14-3-3 proteins as a novel approach to anti-cancer therapeutics

14-3-3 proteins play a pivotal role in controlling cell proliferation and survival, two commonly dysregulated hallmarks of cancers. 14-3-3 protein expression is enhanced in many human cancers and correlates with more aggressive tumors and poor prognosis, suggesting a role for 14-3-3 proteins in tumorigenesis and/or progression. We showed previously that the dimeric state of 14-3-3 proteins is regulated by the lipid sphingosine, a physiological inducer of apoptosis. As the functions of 14-3-3 proteins are dependent on their dimeric state, this sphingosine-mediated 14-3-3 regulation provides a possible means to target dimeric 14-3-3 for therapeutic effect. However, sphingosine mimics are needed that are not susceptible to sphingolipid metabolism. We show here the identification and optimization of sphingosine mimetics that render dimeric 14-3-3 susceptible to phosphorylation at a site buried in the dimer interface and induce mitochondrial-mediated apoptosis. Two such compounds, RB-011 and RB-012, disrupt 14-3-3 dimers at low micromolar concentrations and induce rapid down-regulation of Raf-MAPK and PI3K-Akt signaling in Jurkat cells. Importantly, both RB-011 and RB-012 induce apoptosis of human A549 lung cancer cells and RB-012, through disruption of MAPK signaling, reduces xenograft growth in mice. Thus, these compounds provide proof-of-principle for this novel 14-3-3-targeting approach for anti-cancer drug discovery.

Increased 14-3-3 phosphorylation observed in Parkinson's disease reduces neuroprotective potential of 14-3-3 proteins

14-3-3 proteins are key regulators of cell survival. We have previously demonstrated that 14-3-3 levels are decreased in an alpha-synuclein (αsyn) mouse model of Parkinson's disease (PD), and that overexpression of certain 14-3-3 isoforms is protective in several PD models. Here we examine whether changes in 14-3-3 phosphorylation may contribute to the neurodegenerative process in PD. We examine three key 14-3-3 phosphorylation sites that normally regulate 14-3-3 function, including serine 58 (S58), serine 184 (S184), and serine/threonine 232 (S/T232), in several models of PD and in human PD brain. We observed that an increase in S232 phosphorylation is observed in rotenone-treated neuroblastoma cells, in cells overexpressing αsyn, and in human PD brains. Alterations in S58 phosphorylation were less consistent in these models, and we did not observe any phosphorylation changes at S184. Phosphorylation at S232 induced by rotenone is reduced by casein kinase inhibitors, and is not dependent on αsyn. Mutation of the S232 site affected 14-3-3θ's neuroprotective effects against rotenone and 1-methyl-4-phenylpyridinium (MPP(+)), with the S232D mutant lacking any protective effect compared to wildtype or S232A 14-3-3θ. The S232D mutant partially reduced the ability of 14-3-3θ to inhibit Bax activation in response to rotenone. Based on these findings, we propose that phosphorylation of 14-3-3s at serine 232 contributes to the neurodegenerative process in PD.

Proteomic analysis of BmN cells (Bombyx mori) in response to infection with Nosema bombycis

Nosema bombycis (N. bombycis, Nb) is an obligate intracellular parasite, which can cause pebrine disease in the silkworm. To investigate the effects of N. bombycis infection on the host cells, proteomes from BmN cells that had or had not been infected with N. bombycis at different infection stages were characterized with two-dimensional gel electrophoresis and MALDI-TOF/TOF mass spectrometry, which identified 24 differentially expressed host proteins with significant intensity differences (P < 0.05) at least at one time point in mock- and N. bombycis infected cells. Notably, gene ontology analyses showed that these proteins are involved in many important biological reactions. During the infection phase, proteins involved in energy metabolism and oxidative stress had up-regulated expression. Two proteins participated in ubiquitin-dependent protein catabolic process had down-regulated expression. Quantitative real-time polymerase chain reaction was used to analyze the transcriptional profiles of these identified proteins. Taken together, the abundance changes, putative functions, and participation in biological reactions for the identified proteins produce a host-responsive protein model in N. bombycis-infected BmN cells. These findings further our knowledge about the effect of energy defect parasites on the host cells.

Cables1 complex couples survival signaling to the cell death machinery

Cables1 is a candidate tumor suppressor that negatively regulates cell growth by inhibiting cyclin-dependent kinases. Cables1 expression is lost frequently in human cancer but little is known about its regulation. Here, we report that Cables1 levels are controlled by a phosphorylation and 14-3-3-dependent mechanism. Mutagenic analyses identified two residues, T44 and T150, that are specifically critical for 14-3-3 binding and that serve as substrates for phosphorylation by the cell survival kinase Akt, which by binding directly to Cables1 recruits 14-3-3 to the complex. In cells, Cables1 overexpression induced apoptosis and inhibited cell growth in part by stabilizing p21 and decreasing Cdk2 kinase activity. Ectopic expression of activated Akt (AKT1) prevented Cables1-induced apoptosis. Clinically, levels of phosphorylated Cables1 and phosphorylated Akt correlated with each other in human lung cancer specimens, consistent with pathophysiologic significance. Together, our results illuminated a dynamic regulatory system through which activated Akt and 14-3-3 work directly together to neutralize a potent tumor suppressor function of Cables1.

Alternative 3' UTR selection controls PAR-5 homeostasis and cell polarity in C. elegans embryos

Cell polarity in one-cell C. elegans embryos guides asymmetric cell division and cell-fate specification. Shortly after fertilization, embryos establish two antagonistic cortical domains of PAR proteins. Here, we find that the conserved polarity factor PAR-5 regulates PAR domain size in a dose-dependent manner. Using quantitative imaging and controlled genetic manipulation, we find that PAR-5 protein levels reflect the cumulative output of three mRNA isoforms with different translational efficiencies mediated by their 3' UTRs. 3' UTR selection is regulated, influencing PAR-5 protein abundance. Alternative splicing underlies the selection of par-5 3' UTR isoforms. 3' UTR splicing is enhanced by the SR protein kinase SPK-1, and accordingly, SPK-1 is required for wild-type PAR-5 levels and PAR domain size. Precise regulation of par-5 isoform selection is essential for polarization when the posterior PAR network is compromised. Together, strict control of PAR-5 protein levels and feedback from polarity to par-5 3' UTR selection confer robustness to embryo polarization.

Proteomic identification of 14-3-3ϵ as a linker protein between pERK1/2 inhibition and BIM upregulation in human osteosarcoma cells

Despite advancements in multimodality chemotherapy, conventional cytotoxic treatments still remain ineffective for a subset of patients with aggressive metastatic or multifocal osteosarcoma. It has been shown that pERK1/2 inhibition enhances chemosensitivity to doxorubicin and promotes osteosarcoma cell death in vivo and in vitro. One of the pro-apoptotic mechanisms is upregulation of Bim by pERK1/2 inhibitors. To this end, we examined proteomic changes of 143B human osteosarcoma cells with and without treatment of PD98059, pERK1/2 inhibitor. Specifically, we identified 14-3-3ϵ protein as a potential mediator of Bim expression in response to inhibition of pERK1/2. We hypothesized that 14-3-3ϵ mediates upregulation of Bim expression after pERK1/2 inhibition. We examined the expression of Bim after silencing 14-3-3ϵ using siRNA. The 14-3-3ϵ gene silencing resulted in downregulation of Bim expression after PD98059 treatment. These data indicate that 14-3-3ϵ is required for Bim expression and that it has an anti-cancer effect under pERK1/2 inhibition in 143B cells. By playing an essential role upstream of Bim, 14-3-3ϵ may potentially be a coadjuvant factor synergizing the effect of pERK1/2 inhibitors in addition to conventional cytotoxic agents for more effective osteosarcoma treatments.

Identification of O-GlcNAc modification targets in mouse retinal pericytes: implication of p53 in pathogenesis of diabetic retinopathy

Hyperglycemia is the primary cause of the majority of diabetes complications, including diabetic retinopathy (DR). Hyperglycemic conditions have a detrimental effect on many tissues and cell types, especially the retinal vascular cells including early loss of pericytes (PC). However, the mechanisms behind this selective sensitivity of retinal PC to hyperglycemia are undefined. The O-linked β-N-acetylglucosamine (O-GlcNAc) modification is elevated under hyperglycemic condition, and thus, may present an important molecular modification impacting the hyperglycemia-driven complications of diabetes. We have recently demonstrated that the level of O-GlcNAc modification in response to high glucose is variable in various retinal vascular cells. Retinal PC responded with the highest increase in O-GlcNAc modification compared to retinal endothelial cells and astrocytes. Here we show that these differences translated into functional changes, with an increase in apoptosis of retinal PC, not just under high glucose but also under treatment with O-GlcNAc modification inducers, PUGNAc and Thiamet-G. To gain insight into the molecular mechanisms involved, we have used click-It chemistry and LC-MS analysis and identified 431 target proteins of O-GlcNAc modification in retinal PC using an alkynyl-modified GlcNAc analog (GlcNAlk). Among the O-GlcNAc target proteins identified here 115 of them were not previously reported to be target of O-GlcNAc modification. We have identified at least 34 of these proteins with important roles in various aspects of cell death processes. Our results indicated that increased O-GlcNAc modification of p53 was associated with an increase in its protein levels in retinal PC. Together our results suggest that post-translational O-GlcNAc modification of p53 and its increased levels may contribute to selective early loss of PC during diabetes. Thus, modulation of O-GlcNAc modification may provide a novel treatment strategy to prevent the initiation and progression of DR.

Gene cloning, expression, and function analysis of SpL14-3-3ζ in Spodoptera litura and its response to the entomopathogenic fungus Nomuraea rileyi

The 14-3-3 proteins, a highly evolutionarily conserved and ubiquitous protein family in eukaryotic cells, have a range of biological functions including regulation of signal transduction, stress response, apoptosis, and control of the cell cycle. To investigate the function of 14-3-3 in Spodoptera litura, the full length of 14-3-3ζ was cloned from S. litura on the basis of an expressed sequence tag of 14-3-3ζ from the S. litura fat body suppression subtractive hybridization library, and named SpL14-3-3ζ. SpL14-3-3ζ cDNA was 1196 bp with an open reading frame of 744 bp, encoding 247 amino acids. Multiple alignment analysis revealed the putative amino acids shared >80% homology with 14-3-3ζ from other organisms and shared typical conservative structures. Phylogenetic analysis confirmed SpL14-3-3ζ was closely related to other available Lepidoptera 14-3-3ζ. Real-time PCR analysis indicated SpL14-3-3ζ was expressed throughout the developmental stages of S. litura, with a relatively high expression level in pre-pupa, and was expressed constitutively in all examined tissues with relatively high levels in hemocytes and midgut. Moreover, the transcription level of SpL14-3-3ζ could be induced by Nomuraea rileyi infection, up-regulated in hemocytes, followed by head, fat body and midgut. Knocking down SpL14-3-3ζ transcripts by RNAi significantly increased S. litura sensitivity to fungal infection, and resulted in higher mortality of S. litura during the larval development. These results provide novel insights into the 14-3-3ζ signal regulation which may be related to host defense as well as larval development in S. litura.

Increased 14-3-3ζ expression in the multidrug-resistant leukemia cell line HL-60/VCR as compared to the parental line mediates cell growth and apoptosis in part through modification of gene expression

BACKGROUND

Acute myeloid leukemia (AML) recurrence is largely a result of multidrug resistance (MDR). We aimed to examine the role of 14-3-3ζ in AML chemosensitivity using HL-60 and vincristine-resistant HL-60/VCR cells.

METHODS

The effects of 14-3-3ζ siRNA on the growth and cell cycle progression of HL-60 and HL-60/VCR cells were determined. The effect of 14-3-3ζ siRNA on topotecan (TPT)-induced apoptosis was evaluated by several assays.

RESULTS

Compared to HL-60 cells, HL-60/VCR cells had increased 14-3-3ζ mRNA and protein expression. Increased mdr-1 mRNA as well as mdr-1, Bcl-2 and Mcl-1 protein expression were observed in HL-60/VCR cells. In both HL-60 and HL-60/VCR cells, 14-3-3ζ was observed in the cytoplasm and nuclear compartments. 14-3-3ζ siRNA significantly reduced HL-60 and HL-60/VCR cell growth after 48 h and increased the proportion of cells in the G0/G1 phase. Moreover, 14-3-3ζ siRNA significantly increased the sensitivity of both HL-60 and HL-60/VCR cells to TPT, possibly through the inhibition of Bcl-2, Mcl-1 and mdr-1 protein expression.

CONCLUSIONS

Silencing of 14-3-3ζ increased the sensitivity of both sensitive and resistant HL-60 cells to TPT-induced apoptosis, possibly through altering the expression of apoptosis-associated proteins, suggesting that it may be a potential target for MDR AML.

Knockdown of 14-3-3ζ enhances radiosensitivity and radio-induced apoptosis in CD133(+) liver cancer stem cells

14-3-3ζ is related to many cancer survival cellular processes. In a previous study, we showed that silencing 14-3-3ζ decreases the resistance of hepatocellular carcinoma (HCC) to chemotherapy. In this study, we investigated whether silencing 14-3-3ζ affects the radioresistance of cancer stem-like cells (CSCs) in HCC. Knockdown of 14-3-3ζ decreased cell viability and the number of spheres by reducing radioresistance in CSCs after γ-irradiation (IR). Furthermore, the levels of pro-apoptotic proteins were upregulated in CSCs via silencing 14-3-3ζ after IR. These results suggest that 14-3-3ζ knockdown enhances radio-induced apoptosis by reducing radioresistance in liver CSCs.

Proteins differentially expressed in human beta-cells-enriched pancreatic islet cultures and human insulinomas

In view of the great demand for human beta-cells for physiological and medical studies, we generated cell lines derived from human insulinomas which secrete insulin, C-peptide and express neuroendocrine and islet markers. In this study, we set out to characterize their proteomes, comparing them to those of primary beta-cells using DIGE followed by MS. The results were validated by Western blotting. An average of 1800 spots was detected with less than 1% exhibiting differential abundance. Proteins more abundant in human islets, such as Caldesmon, are involved in the regulation of cell contractility, adhesion dependent signaling, and cytoskeletal organization. In contrast, almost all proteins more abundant in insulinoma cells, such as MAGE2, were first described here and could be related to cell survival and resistance to chemotherapy. Our proteomic data provides, for the first time, a molecular snapshot of the orchestrated changes in expression of proteins involved in key processes which could be correlated with the altered phenotype of human beta-cells. Collectively our observations prompt research towards the establishment of bioengineered human beta-cells providing a new and needed source of cultured human beta-cells for beta-cell research, along with the development of new therapeutic strategies for detection, characterization and treatment of insulinomas.