Specific 14-3-3 isoform detection and immunolocalization in prion diseases

Formation of amyloid fibrils by the regulatory 14-3-3ζ protein

The 14-3-3 proteins are a highly conserved adaptor protein family with multi-layer functions, abundantly expressed in the brain. The 14-3-3 proteins modulate phosphorylation, regulate enzymatic activity and can act as chaperones. Most importantly, they play an important role in various neurodegenerative disorders due to their vast interaction partners. Particularly, the 14-3-3ζ isoform is known to co-localize in aggregation tangles in both Alzheimer's and Parkinson's diseases as a result of protein-protein interactions. These abnormal clumps consist of amyloid fibrils, insoluble aggregates, mainly formed by the amyloid-β, tau and α-synuclein proteins. However, the molecular basis of if and how 14-3-3ζ can aggregate into amyloid fibrils is unknown. In this study, we describe the formation of amyloid fibrils by 14-3-3ζ using a comprehensive approach that combines bioinformatic tools, amyloid-specific dye binding, secondary structure analysis and atomic force microscopy. The results presented herein characterize the amyloidogenic properties of 14-3-3ζ and imply that the well-folded protein undergoes aggregation to β-sheet-rich amyloid fibrils.

Differential Expression of Proteins Associated with Bipolar Disorder as Identified Using the PeptideShaker Software

The prevalence of bipolar disorder (BD) in modern society is growing rapidly, but due to the lack of paraclinical criteria, its differential diagnosis with other mental disorders is somewhat challenging. In this regard, the relevance of proteomic studies is increasing due to the development of methods for processing large data arrays; this contributes to the discovery of protein patterns of pathological processes and the creation of new methods of diagnosis and treatment. It seems promising to search for proteins involved in the pathogenesis of BD in an easily accessible material-blood serum. Sera from BD patients and healthy individuals were purified via affinity chromatography to isolate 14 major proteins and separated using 1D SDS-PAGE. After trypsinolysis, the proteins in the samples were identified via HPLC/mass spectrometry. Mass spectrometric data were processed using the OMSSA and X!Tandem search algorithms using the UniProtKB database, and the results were analyzed using PeptideShaker. Differences in proteomes were assessed via an unlabeled NSAF-based analysis using a two-tailed Bonferroni-adjusted t-test. When comparing the blood serum proteomes of BD patients and healthy individuals, 10 proteins showed significant differences in NSAF values. Of these, four proteins were predominantly present in BD patients with the maximum NSAF value: 14-3-3 protein zeta/delta; ectonucleoside triphosphate diphosphohydrolase 7; transforming growth factor-beta-induced protein ig-h3; and B-cell CLL/lymphoma 9 protein. Further exploration of the role of these proteins in BD is warranted; conducting such studies will help develop new paraclinical criteria and discover new targets for BD drug therapy.

14-3-3 Proteins are Potential Regulators of Liquid-Liquid Phase Separation

The 14-3-3 family proteins are vital scaffold proteins that ubiquitously expressed in various tissues. They interact with numerous protein targets and mediate many cellular signaling pathways. The 14-3-3 binding motifs are often embedded in intrinsically disordered regions which are closely associated with liquid-liquid phase separation (LLPS). In the past ten years, LLPS has been observed for a variety of proteins and biological processes, indicating that LLPS plays a fundamental role in the formation of membraneless organelles and cellular condensates. While extensive investigations have been performed on 14-3-3 proteins, its involvement in LLPS is overlooked. To date, 14-3-3 proteins have not been reported to undergo LLPS alone or regulate LLPS of their binding partners. To reveal the potential involvement of 14-3-3 proteins in LLPS, in this review, we summarized the LLPS propensity of 14-3-3 binding partners and found that about one half of them may undergo LLPS spontaneously. We further analyzed the phase separation behavior of representative 14-3-3 binders and discussed how 14-3-3 proteins may be involved. By modulating the conformation and valence of interactions and recruiting other molecules, we speculate that 14-3-3 proteins can efficiently regulate the functions of their targets in the context of LLPS. Considering the critical roles of 14-3-3 proteins, there is an urgent need for investigating the involvement of 14-3-3 proteins in the phase separation process of their targets and the underling mechanisms.

14-3-3 Proteins: Novel Pharmacological Targets in Neurodegenerative Diseases

14-3-3 proteins are a family of proteins expressed throughout the body and implicated in many diseases, from cancer to neurodegenerative disorders. While these proteins do not have direct enzymatic activity, they form a hub for many signaling pathways via protein-protein interactions (PPIs). 14-3-3 interactions have proven difficult to target with traditional pharmacological methods due to the unique nature of their binding. However, recent advances in compound development utilizing a range of tools, from thermodynamic binding site analysis to computational molecular modeling techniques, have opened the door to targeting these interactions. Compounds are already being developed targeting 14-3-3 interactions with potential therapeutic implication for neurodegenerative disorders, but challenges still remain in optimizing specificity and target engagement to avoid unintended negative consequences arising from targeting 14-3-3 signaling networks.

14-3-3/Tau Interaction and Tau Amyloidogenesis

The major function of microtubule-associated protein tau is to promote microtubule assembly in the central nervous system. However, aggregation of abnormally phosphorylated tau is a hallmark of tauopathies. Although the molecular mechanisms of conformational transitions and assembling of tau molecules into amyloid fibril remain largely unknown, several factors have been shown to promote tau aggregation, including mutations, polyanions, phosphorylation, and interactions with other proteins. 14-3-3 proteins are a family of highly conserved, multifunctional proteins that are mainly expressed in the central nervous system. Being a scaffolding protein, 14-3-3 proteins interact with tau and regulate tau phosphorylation by bridging tau with various protein kinases. 14-3-3 proteins also directly regulate tau aggregation via specific and non-specific interactions with tau. In this review, we summarize recent advances in characterization of tau conformation and tau/14-3-3 interaction. We discuss the connection between 14-3-3 binding and tau aggregation with a special emphasis on the regulatory role of 14-3-3 on tau conformation.

14-3-3β exerts glioma-promoting effects and is associated with malignant progression and poor prognosis in patients with glioma

Glioma is a type of tumor that affects the central nervous system. It has been demonstrated that 14-3-3β, a protein that is mainly concentrated in the brain, serves an important role in tumor regulation. However, the mechanism of action of 14-3-3β that underlies the pathogenesis of glioma remains to be elucidated. In the present study, 14-3-3β was silenced by RNA interference in the human glioma cell line U373-MG. Following knockdown of 14-3-3β, the proliferation, colony formation, cell cycle progression, migration and invasion of U373-MG cells were significantly decreased (P<0.01), whereas cell apoptosis was increased (P<0.01). Furthermore, in a tumor xenograft experiment, silencing 14-3-3β significantly inhibited the in vivo tumor growth of U373-MG cells (P<0.01). The results demonstrated that 14-3-3β levels were significantly higher in human glioma tissues compared with normal brain tissues (P<0.01) and high 14-3-3β expression was significantly associated with advanced pathological grade (P<0.03) and low Karnofsky performance scale (P<0.003). Patients with glioma who had high 14-3-3β levels had a significantly shorter survival time compared with those with low expression of 14-3-3β (P=0.031), suggesting that 14-3-3β may be an effective predictor of the prognosis of patients with glioma. The results of the present study indicate that 14-3-3β serves an oncogenic role in glioma, suggesting that 14-3-3β may have potential as a promising therapeutic target for glioma.

Dual binding of 14-3-3 protein regulates Arabidopsis nitrate reductase activity

14-3-3 proteins represent a family of ubiquitous eukaryotic proteins involved in numerous signal transduction processes and metabolic pathways. One important 14-3-3 target in higher plants is nitrate reductase (NR), whose activity is regulated by different physiological conditions. Intra-molecular electron transfer in NR is inhibited following 14-3-3 binding to a conserved phospho-serine motif located in hinge 1, a surface exposed loop between the catalytic molybdenum and central heme domain. Here we describe a novel 14-3-3 binding site within the NR N-terminus, an acidic motif conserved in NRs of higher plants, which significantly contributes to 14-3-3-mediated inhibition of NR. Deletion or mutation of the N-terminal acidic motif resulted in a significant loss of 14-3-3 mediated inhibition of Ser534 phosphorylated NR-Mo-heme (residues 1-625), a previously established model of NR regulation. Co-sedimentation and crosslinking studies with NR peptides comprising each of the two binding motifs demonstrated direct binding of either peptide to 14-3-3. Surface plasmon resonance spectroscopy disclosed high-affinity binding of 14-3-3ω to the well-known phospho-hinge site and low-affinity binding to the N-terminal acidic motif. A binding groove-deficient 14-3-3ω variant retained interaction to the acidic motif, but lost binding to the phospho-hinge motif. To our knowledge, NR is the first enzyme that harbors two independent 14-3-3 binding sites with different affinities, which both need to be occupied by 14-3-3ω to confer full inhibition of NR activity under physiological conditions.

Functional characterization of G-protein-coupled receptors: a bioinformatics approach

Complex molecular and cellular mechanisms regulate G protein-coupled receptors (GPCRs). It is suggested that proteins intrinsically disordered regions (IDRs) are to play a role in GPCR's intra and extracellular regions plasticity, due to their potential for post-translational modification and interaction with other proteins. These regions are defined as lacking a stable three-dimensional (3D) structure. They are rich in hydrophilic and charged, amino acids and are capable to assume different conformations which allow them to interact with multiple partners. In this study we analyzed 75 GPCR involved in synaptic transmission using computational tools for sequence-based prediction of IDRs within a protein. We also evaluated putative ligand-binding motifs using receptor sequences. The disorder analysis indicated that neurotransmitter GPCRs have a significant amount of disorder in their N-terminus, third intracellular loop (3IL) and C-terminus. About 31%, 39% and 53% of human GPCR involved in synaptic transmission are disordered in these regions. Thirty-three percent of receptors show at least one predicted PEST motif, this being statistically greater than the estimate for the rest of human GPCRs. About 90% of the receptors had at least one putative site for dimerization in their 3IL or C-terminus. ELM instances sampled in these domains were 14-3-3, SH3, SH2 and PDZ motifs. In conclusion, the increased flexibility observed in GPCRs, added to the enrichment of linear motifs, PEST and heteromerization sites, may be critical for the nervous system's functional plasticity.

Implication of 14-3-3ε and 14-3-3θ/τ in proteasome inhibition-induced apoptosis of glioma cells

Proteasome inhibitors represent a novel class of anticancer agents that are used in the treatment of hematologic malignancies and various solid tumors. However, mechanisms underlying their anticancer actions were not fully understood. It has been reported that strong 14-3-3 protein expression is observed and associated with tumor genesis and progression of astrocytoma. In addition, global inhibition of 14-3-3 functions with a general 14-3-3 antagonist difopein induces apoptosis of human astrocytoma cells, validating 14-3-3 as a potential molecular target for anticancer therapeutic management. In the current study, for the first time we demonstrated that proteasome inhibitors downregulated 14-3-3ε and 14-3-3θ/τ in U87 and SF295 glioma cells. Overexpression of 14-3-3ε and 14-3-3θ/τ significantly suppressed apoptosis of human glioma cells induced by proteasome inhibitors. We also demonstrated that MG132 activated ASK1 and siASK1 compromised the MG132-induced apoptosis of glioma cells. Furthermore, overexpression of 14-3-3ε and 14-3-3θ/τ markedly suppressed activation of ASK1. Collectively, the current study supported that proteasome inhibitors, at least in part, caused cytotoxicity of glioma cells via downregulation of 14-3-3ε and 14-3-3θ/τ and subsequent activation of ASK1.

Role of 14-3-3-beta in the migration and invasion in human malignant glioma cell line U87MG

PURPOSE

To assess the influence of 14-3-3-beta in modulating the migration and invasion of human glioma cells.

METHODS

To profile the genes associated with malignant glioma cell motility, differential display-polymerase chain reaction was performed and the findings were validated by Northern blotting in the U343MG-A, U87MG, and U87MG-10' human glioma cell lines. Antisense 14-3-3-beta cDNA plasmid was transfected into U87MG ('U87-YA-3'). To follow motility changes after transfection, simple scratch test and matrigel assay were performed. Morphological and cytoskeletal changes were documented by light and confocal microscopy. In addition, doubling times of the transfectant and endogenous 14-3-3-beta levels were determined in various glioma cell lines with different motilities.

RESULTS

14-3-3-beta was highly expressed in U87MG cells. U87-YA-3 cells became small and flat, and actin was depolarized. Furthermore, U87-YA-3 cell motility was inhibited markedly versus parental U87MG cells. The doubling times of transfected and parent cells were 32 and 37 hours, respectively. Endogenous 14-3-3-beta expression in the human glioma cell lines was proportional to their migratory and invasive abilities.

CONCLUSION

14-3-3-beta modulates the migration and invasion in U87MG cells, which may be useful in developing therapeutic approaches for the treatment of glioma.

14-3-3s are potential biomarkers for HIV-related neurodegeneration

Over the last decade, it has become evident that 14-3-3 proteins are essential for primary cell functions. These proteins are abundant throughout the body, including the central nervous system and interact with other proteins in both cell cycle and apoptotic pathways. Examination of cerebral spinal fluid in humans suggests that 14-3-3s including 14-3-3ε (YWHAE) are up-regulated in several neurological diseases, and loss or duplication of the YWHAE gene leads to Miller-Dieker syndrome. The goal of this review is to examine the utility of 14-3-3s as a marker of human immune deficiency virus (HIV)-dependent neurodegeneration and also as a tool to track disease progression. To that end, we describe mechanisms implicating 14-3-3s in neurological diseases and summarize evidence of its interactions with HIV accessory and co-receptor proteins.

14-3-3 proteins in neurodegeneration

Among the first reported functions of 14-3-3 proteins was the regulation of tyrosine hydroxylase (TH) activity suggesting a possible involvement of 14-3-3 proteins in Parkinson's disease. Since then the relevance of 14-3-3 proteins in the pathogenesis of chronic as well as acute neurodegenerative diseases, including Alzheimer's disease, polyglutamine diseases, amyotrophic lateral sclerosis and stroke has been recognized. The reported function of 14-3-3 proteins in this context are as diverse as the mechanism involved in neurodegeneration, reaching from basal cellular processes like apoptosis, over involvement in features common to many neurodegenerative diseases, like protein stabilization and aggregation, to very specific processes responsible for the selective vulnerability of cellular populations in single neurodegenerative diseases. Here, we review what is currently known of the function of 14-3-3 proteins in nervous tissue focussing on the properties of 14-3-3 proteins important in neurodegenerative disease pathogenesis.

The expression of seven 14-3-3 isoforms in human meningioma

14-3-3 proteins comprise a large family of highly conserved, acidic polypeptides, expressed in all eukaryotic organisms, with highest concentration found in the brain. Multiple isoforms of 14-3-3 proteins have been shown to play an essential role in regulating differentiation, proliferation and transformation. In the previous study, the expression levels of all seven 14-3-3 isoforms were examined in astrocytoma. However, the expression of seven 14-3-3 isoforms in meningioma still remains unknown. This study is the first examination of 14-3-3 isoforms in three grades of meningioma by immunohistochemistry. 14-3-3epsilon, zeta and theta were specifically expressed in meningioma, and their expression levels increased with the increase of pathological grade of meningioma. The 14-3-3 eta, beta, gamma and sigma isoforms were negatively expressed in meningioma. In conclusion, The 14-3-3 epsilon, zeta and theta may be involved in tumorigenesis of meningioma and be efficient markers for predicting the degree of malignancy in meningioma.

Identification of a novel 14-3-3zeta binding site within the cytoplasmic domain of platelet glycoprotein Ibalpha that plays a key role in regulating the von Willebrand factor binding function of glycoprotein Ib-IX

RATIONALE

The interaction between platelet glycoprotein (GP) Ib-IX and von Willebrand factor (VWF) is initiated by conformational changes in immobilized VWF and is also regulated by the intraplatelet proteins 14-3-3zeta and filamin A. Both 14-3-3zeta and filamin A associate with the cytoplasmic domain of GPIbalpha, whereas little is known about their relationship in regulating the VWF binding function of GPIb-IX.

OBJECTIVE

To explore the mechanism underlying the roles of 14-3-3zeta and filamin A in regulating the VWF binding function of GPIb-IX.

METHODS AND RESULTS

A truncation mutant of GPIbalpha (Delta565) deleting the C-terminal 14-3-3zeta binding sites retained 14-3-3zeta binding function, in contrast, deletion of the C-terminal residues 551 to 610 of GPIbalpha totally abolished 14-3-3zeta binding, indicating that the residues 551 to 564 of GPIbalpha are important in the interaction between 14-3-3zeta and GPIb-IX. An antibody recognizing phosphorylated R557GpSLP561 sequence reacted with GPIbalpha suggesting phosphorylation of a population of GPIbalpha molecules at Ser559, and a membrane permeable phosphopeptide (MP-P), R557GpSLP561 corresponding to residues 557 to 561 of GPIbalpha eliminated the association of 14-3-3zeta with Delta565. MP-P also promoted GPIb-IX association with the membrane skeleton, and inhibited ristocetin-induced platelet agglutination, VWF binding to platelets and platelet adhesion to immobilized VWF. Furthermore, a GPIb-IX mutant replacing Ser559 of GPIbalpha with alanine showed an enhanced association with the membrane skeleton, reduced ristocetin-induced VWF binding, and diminished ability to mediate cell adhesion to VWF under flow conditions.

CONCLUSIONS

These data suggest a phosphorylation-dependent binding of 14-3-3zeta to central filamin A binding site of GPIbalpha, and the dimeric 14-3-3zeta binding to both the C-terminal site and central RGpSLP site inhibits GPIb-IX association with the membrane skeleton and promotes the VWF binding function of GPIb-IX.

Glial cell type-specific subcellular localization of 14-3-3 zeta: an implication for JCV tropism

14-3-3 Isoforms are shown to be upregulated or accumulated in the glial cells of autopsied patient brains affected with progressive multifocal leukoencephalopathy (PML), a demylinating disease caused by JC virus (JCV). The possible involvement of 14-3-3 in JCV tropism, however, has never been examined. To investigate a potential relationship between 14-3-3 isoforms and JCV in vitro, we examined the localization of six 14-3-3 isoforms in human neural progenitors and progenitor-derived astrocytes (PDAs) in cells without JCV exposure. The 14-3-3 zeta isoform was initially localized in the progenitor cytoplasm. When differentiation of progenitors into PDAs was induced, the zeta isoform was translocated into the nucleus. However, upon JCV infection, progenitor cells exhibited an uncharacteristic 14-3-3 zeta nuclear presence in the few cells that became infected. JCV-treated PDAs showed elevated levels of 14-3-3 zeta compared with noninfected PDAs. Treatment with TGF-beta1, a known stimulant of JCV multiplication, increased the overall number of infected cells and the otherwise absent nuclear presence of 14-3-3 zeta in progenitors. These results suggest that the nuclear presence of 14-3-3 zeta may play a role in JCV infection, and that the isoform may in part determine JCV susceptibility in these cell types.

14-3-3zeta contributes to tyrosine hydroxylase activity in MN9D cells: localization of dopamine regulatory proteins to mitochondria

The 14-3-3 proteins stimulate the activation of tyrosine hydroxylase (TH), the rate-limiting catecholamine biosynthetic enzyme. To explore if particular endogenous 14-3-3 isoforms specifically affected TH activity and dopamine synthesis, we utilized rodent nigrostriatal tissues and midbrain-derived MN9D dopaminergic cells. Extracts from ventral midbrain and MN9D cells contained similar pools of 14-3-3 mRNAs, with 14-3-3zeta being relatively abundant in both. Protein levels of 14-3-3zeta were also abundant. [(32)P]Orthophosphate labeling of MN9D cells, followed by co-immunoprecipitation with pan-TH and pan-14-3-3 antibodies brought down similar amounts of phosphorylated TH in each, confirming that 14-3-3-bound phosphorylated TH in our cells. Co-immunoprecipitation of striatal tissues with a pan-TH antibody precipitated 14-3-3zeta but not another potential TH regulatory isoform, 14-3-3eta. In whole cell extracts from MN9D cells after 14-3-3 small interfering RNA treatments, we found that 14-3-3zeta knockdown significantly reduced TH activity and dopamine synthesis whereas knockdown of 14-3-3eta had no effect. 14-3-3zeta was found co-localized on mitochondria with TH, and its knockdown by small interfering RNA reduced TH phosphorylation and TH activity in the mitochondrial pool. Together the data support a role for 14-3-3zeta as an endogenous activator of TH in midbrain dopaminergic neurons and furthermore, identify mitochondria as a potential novel site for dopamine synthesis, with implications for Parkinson disease.

Binding of 14-3-3 proteins to a single stranded oligodeoxynucleotide aptamer

A synthetic library of ca. 10(13) single stranded oligodeoxynucleotides, each comprising a randomized 40mer sequence and homogeneous 10mer flanking regions, was screened for binding to recombinant human 14-3-3gamma. A single aptamer, which showed similar affinities (K(D) approximately 10(-8)M) for six isoforms of the protein, has been shown to bind to undenatured 14-3-3 protein in the cerebral spinal fluid of scrapie infected sheep.

Identification of 14-3-3 protein isoforms in human astrocytoma by immunohistochemistry

The 14-3-3 proteins are highly conserved, ubiquitous molecules involved in a variety of biologic events, such as cell cycle control, and apoptosis. In our previous study, it has been proved that they are expressed in primary human nervous system tumors. However, the isoform-specific expression of 14-3-3 protein is still need to be identified. This study is the first detection of 14-3-3 isoforms' specific expression in human astrocytoma. In the normal brain tissues, all the seven 14-3-3 isoforms' immunoreactivity was localized mainly in the neurons, while only weak expression of epsilon, zeta and theta was found in some glial cells. However, beta, epsilon, zeta, eta and theta isoforms' immunoreactivity was seen in the majority of astrocytoma samples and its immunoreactivity score was increased markedly with an increase in the pathologic grade of human astrocytomas. These results indicate that the five isoforms may play an important role in tumorigenesis of human astrocytoma.

The ε Isoform of 14-3-3 Protein Is a Component of the Prion Protein Amyloid Deposits of Gerstmann-Sträussler-Scheinker Disease

The 14-3-3 proteins are highly conserved, ubiquitous molecules involved in a variety of biologic events, such as transduction pathway modulation, cell cycle control, and apoptosis. Seven isoforms have been identified that are abundant in the brain, preferentially localized in neurons. Remarkable increases in 14-3-3 are seen in the cerebrospinal fluid of patients with Creutzfeldt-Jakob disease (CJD), and it has been found in pathologic inclusions of several neurodegenerative diseases. Moreover, the zeta isoform has been detected in prion protein (PrP) amyloid deposits of CJD patients. To further investigate the cerebral distribution of 14-3-3 in prion-related encephalopathies, we carried out an immunohistochemical and biochemical analysis of brain tissue from patients with Gerstmann-Sträussler-Scheinker disease (GSS) and sporadic, familial and acquired forms of CJD, using specific antibodies against the seven 14-3-3 isoforms. The study showed a strong immunoreactivity of PrP amyloid plaques of GSS patients for the 14-3-3 epsilon isoform, but not for the other isoforms. The epsilon isoform of 14-3-3 was not found in PrP deposits of CJD. These results indicate that the epsilon isoform of 14-3-3 is a component of PrP amyloid deposits of GSS and suggest that this is the sole 14-3-3 isoform specifically involved in the neuropathologic changes associated with this disorder.

14-3-3 protein detection in the cerebrospinal fluid of patients with influenza-associated encephalopathy

Influenza-associated encephalopathy is characterized by high fever, convulsions, and loss of consciousness associated with influenza infection in children, but its pathophysiology remains to be clarified. We examined 14-3-3 proteins, which are acidic brain proteins, in cerebrospinal fluid by immunoblotting in four patients with influenza-associated encephalopathy, four patients with influenza without encephalopathy, and four patients with another encephalopathy. Interestingly, we detected 14-3-3 proteins in all four patients with influenza-associated encephalopathy (100%) but not in any of the other patients. 14-3-3 isoforms, including beta, gamma, epsilon, xi, and theta, were found in the cerebrospinal fluid of the patients with influenza-associated encephalopathy, suggesting extensive damage to the brain. We conclude that 14-3-3 proteins in cerebrospinal fluid are highly detectable in influenza-associated encephalopathy and thus can be used as a rapid diagnostic marker.

Immunocytochemical detection of 14-3-3 in primary nervous system tumors

14-3-3 proteins have attracted much recent interest in the etiopathogenesis of human cancers owing to their involvement in the prevention of apoptosis. However, the expression of 14-3-3 in primary nervous system tumors has not been previously characterized. In this paper, Immunohistochemistry using a specific anti-14-3-3 antibody was performed on formalin-fixed, paraffin embedded archival tissue from 124 primary human nervous system tumors and 10 normal brain tissues. In the normal control brains, 14-3-3 immunoreactivity was localized mainly in the neuronal somata and processes, and some glial cells showed only weak immunoreactivity. However, 14-3-3 immunoreactivity was seen in the majority of astrocytomas [grade I (9/11), II (16/21), III (13/17), IV (17/21)]. There was no difference between the positive expression rates of 14-3-3 in different grades of astrocytomas (P = 0.968). But the intensity and degree of 14-3-3 immunoreactivity in diffuse astrocytomas, anaplastic astrocytoma, and glioblastoma multiformes showed trends with tumor grade, with glioblastomas having the highest positivity (P = 0.048). The 14-3-3 immunoreactivity was also seen in the majority of other gliomas [oligodendroglioma (2/3), anaplastic oligodendroglioma (4/4), ependymoma (1/2), anaplastic ependymoma (2/2), choroid plexus papilloma (3/3), pineocytoma (2/2), medulloblastoma (5/8)]. All meningiomas [syncytical (3), fibrous/fibroblastic (4), angiomatous (4), transitional/mixed (3)] were intensely and diffusely positive. All schwannomas (4), neurofibromas (2), pituitary adenomas (6) and craniopharyngiomas(4) also showed intense positive staining. These results showed that 14-3-3 is expressed in the majority of the primary human nervous system tumors. The up-regulated expression of 14-3-3 may be a common mechanism for evading apoptosis in most primary human nervous system tumors, and targeting 14-3-3 may be a novel promising strategy for the treatment of these tumors, especially for malignant tumors.

Unchanged survival rates of 14-3-3gamma knockout mice after inoculation with pathological prion protein

The diagnosis of sporadic Creutzfeldt-Jakob disease (CJD) is based on typical clinical findings and is supported by a positive 14-3-3 Western blot of cerebrospinal fluid. However, it is not clear whether 14-3-3 indicates general neuronal damage or is of pathophysiological relevance in CJD. The fact that the 14-3-3 isoform spectrum in cerebrospinal fluid does not correspond to that found in the brain points to a regulated process. To investigate a possible role of 14-3-3 proteins in transmissible spongiform diseases, we generated a 14-3-3gamma-deficient mutant mouse line by using a classical knockout strategy. The anatomy and cage behavior of the mutant mice were normal. Western blot analyses of brain homogenates revealed no changes in the protein expression of other 14-3-3 isoforms (epsilon, beta, zeta, and eta). Proteomic analyses of mouse brains by two-dimensional differential gel electrophoresis showed that several proteins, including growth hormone, 1-Cys peroxiredoxin, CCT-zeta, glucose-6-phosphate isomerase, GRP170 precursor, and alpha-SNAP, were differentially expressed. Mutant and wild-type mice were inoculated either intracerebrally or intraperitoneally with the Rocky Mountain Laboratory strain of scrapie, but no differences were detected in the postinoculation survival rates. These results indicate that 14-3-3gamma is unlikely to play a causal role in CJD and related diseases.

Neuroprotection with delayed initiation of prolonged hypothermia after in vitro transient global brain ischemia

Prolonged therapeutic hypothermia (32-34 degrees C for 12-24 h) improves the functional outcome of comatose cardiac arrest survivors. It is generally believed that rapidly achieving target temperature optimizes neuroprotection. However, this hypothesis has not been tested systematically. In this study, we compared the neuroprotective effect of prolonged hypothermia initiated between 0 and 8 h after reoxygenation using an in vitro model of simulated global brain ischemia. Organotypic hippocampal slices were prepared from 5-day-old Wistar rat pups and cultured for 1 week prior to analysis. Ischemia was simulated by normothermic oxygen-glucose deprivation (OGD). Hypothermia (33 degrees C) was initiated 0-8 h after reoxygenation and maintained until 24 h post-injury. CA1 regional cell death was quantified by propidium iodide (PI) fluorescence. Release of 14-3-3 beta protein was evaluated as a potential surrogate maker for neuroprotection. Hypothermia initiated 0, 1, 2, or 4 h after 30 min OGD reduced 24 h CA1 regional PI fluorescence by 47 +/- 34%, 85 +/- 4%, 88 +/- 3%, and 88 +/- 5% (P < 0.05 for all versus normothermic reoxygenation). Direct comparison of hypothermia initiated 4 or 8 h after reoxygenation revealed equivalent neuroprotection following 15 and 30 min OGD, but neither was protective after 60 min OGD. Hypothermia initiated 4 or 8 h after 30 min OGD reduced 14-3-3 beta release by 73 +/- 11% and 92 +/- 4%, respectively (P < 0.01 for both versus normothermic reoxygenation). In this model, the neuroprotective effect of prolonged post-ischemic hypothermia is both optimal and equivalent when initiated between 1 and 8 h after reoxygenation. These results suggest the need for further in vivo studies to define the therapeutic window within which prolonged hypothermia is optimally neuroprotective after cardiac arrest.

Unlocking the code of 14-3-3

One of the most striking 'rags to riches' stories in the protein world is that of 14-3-3, originally identified in 1967 as merely an abundant brain protein. The first clues that 14-3-3 would play an important role in cell biology came almost 25 years later when it was found to interact with various proto-oncogene proteins and signaling proteins. The subsequent identification of 14-3-3 as a phosphoserine/phosphothreonine-binding protein firmly established its importance in cell signaling. 14-3-3 family members are found in all eukaryotes - from plants to mammals - and more than 100 binding partners have been identified to date. The targets of 14-3-3 are found in all subcellular compartments and their functional diversity is overwhelming - they include transcription factors, biosynthetic enzymes, cytoskeletal proteins, signaling molecules, apoptosis factors and tumor suppressors. 14-3-3 binding can alter the localization, stability, phosphorylation state, activity and/or molecular interactions of a target protein. Recent studies now indicate that the serine/threonine protein phosphatases PP1 and PP2A are important regulators of 14-3-3 binding interactions, and demonstrate a role for 14-3-3 in controlling the translocation of certain proteins from the cytoplasmic and endoplasmic reticulum to the plasma membrane. New reports also link 14-3-3 to several neoplastic and neurological disorders, where it might contribute to the pathogenesis and progression of these diseases.

Fusicoccin signaling reveals 14-3-3 protein function as a novel step in left-right patterning during amphibian embryogenesis

To gain insight into the molecular mechanisms underlying the control of morphogenetic signals by H+ flux during embryogenesis, we tested Fusicoccin-A (FC), a compound produced by the fungus Fusicoccum amygdali Del. In plant cells, FC complexes with 14-3-3 proteins to activate H+ pumping across the plasma membrane. It has long been thought that FC acts on higher plants only; here, we show that exposing frog embryos to FC during early development specifically results in randomization of the asymmetry of the left-right (LR) axis (heterotaxia). Biochemical and molecular-genetic evidence is presented that 14-3-3-family proteins are an obligate component of Xenopus FC receptors and that perturbation of 14-3-3 protein function results in heterotaxia. The subcellular localization of 14-3-3 mRNAs and proteins reveals novel cytoplasmic destinations, and a left-right asymmetry at the first cell division. Using gain-of-function and loss-of-function experiments, we show that 14-3-3E protein is likely to be an endogenous and extremely early aspect of LR patterning. These data highlight a striking conservation of signaling pathways across kingdoms, suggest common mechanisms of polarity establishment between C. elegans and vertebrate embryos, and uncover a novel entry point into the pathway of left-right asymmetry determination.