Biosynthesis of Grayanotoxins in Leucothoe grayana Max.Incorporation of Mevalonic Acid and (—)-Kaurene into Grayanotoxin-III

The main subunits of glutenin were separated by preparative SDS-PAGE with a Laemmli system (U. K. Laemmli, Nature, 227, 680 (1970)) and their cysteine (Cys) contents were determined by amino acid analysis. Amino acid compositions of glutenin subunits, determined in the present study, were different from those determined by Danno et al. [G. Danno, K. Kanazawa and M. Natake, Agric. Biol. Chem., 40, 739 (1976)]. We found that these differences were due to the different methods of hydrolysis of subunit polypeptides. That is, hydrolysis of subunit polypeptides extracted from gel and hydrolysis of polypeptides in gel without extraction. Cys contents of glutenin subunits were determined as S-pyridylethyl cysteine (PE-Cys). Although no PE-Cys was detected in B-4 or B-4′, all other subunits were shown to have 4mol Cys per mol protein, respectively.     

A lysine-free mutant of epidermal growth factor as targeting moiety of a targeted toxin

AimsElevated levels of epidermal growth factor (EGF) receptor are observed on several human tumors, e.g. cervical carcinoma and mamma carcinomas. The natural ligand EGF is an alternative to established antibodies and tyrosine kinase inhibitors for targeting EGF receptor-overexpressing tumor cells for therapy. Conjugations of compounds to EGF lack the necessary homogeneity for an intended application, since several amino acids may react with the chemical linker.Main methodsWe designed an EGF variant (EGF^RR) in which the two lysines were substituted with arginine (K28R and K48R). EGF^RR was fused to the protein toxin saporin to obtain a model protein for detailed analyses on EGF receptor binding and on both the enzymatic activity of saporin and the cytotoxicity of the fusion protein.Key findingsThe mutation decreased the enzymatic activity of saporin 2.3-fold and the binding of EGF^RR retained its specificity for EGF receptor while increasing the Kd 5.5-fold. In spite of these differences the cytotoxicity of the fusion protein was unchanged in comparison to a fusion protein with EGF both when applied alone and in combination with cytotoxicity augmenting saponin.SignificanceWe conclude that EGF^RR retained its ability to bind with high specificity to EGF receptor and is thus suitable for a number of chemical linkage applications such as targeting drugs or dyes to EGF receptor-expressing cells.     

More Than one Alpha Variant May Exist in a GabaA/benzodiazepine Receptor Complex

Abstract

G A B A_A/Benzodiazepine receptors are formed by the assembly of presumably five polypeptides with unknown stoichiometry. Six α, three β, two λ, and one δ subunit have been characterized on the molecular level. In analogy to the nicotinic acetylcholine receptor, and supported by functional analysis of recombinantly expressed GABA_A receptor subunits, a structure containing at least three different polypeptides has been proposed for the functional GABA_A and benzodiazepine regulated Cl^?-channel. Using an α₁ subunit specific antiserum we could show that additional α variants are present in α₁ subunit containing GABA_A/Benzodiazepine receptor complexes. This suggests that the diversity of GABA_A/Benzodiazepine receptors may be larger than previously thought.     

Orientation of the cleavage map of the 200-kilodalton polypeptide encoded by the bottom-component RNA of cowpea mosaic virus

The genomic organization of the bottom-component RNA of cowpea mosaic virus was studied. In vivo, this RNA encodes at least eight different polypeptides of 170, 110, 87, 84, 60, 58, 32, and 4 kilodaltons (K), the last polypeptide representing the genome-bound protein VPg. In rabbit reticulocyte lysates, bottom-component RNA is translated into a 200K polypeptide which is then processed to give the 32 and 170K polypeptides also found in vivo. By pulse-labeling the 200K primary translation product, we now show that the 32 and 170K polypeptides are derived from the NH₂-terminal and COOH-terminal parts of this polypeptide, respectively. Comparison of the proteolytic peptide patterns of 170K polypeptides synthesized in vitro and pulse-labeled at either the NH₂-terminal or the COOH-terminal end with the patterns of the 170 and 110K polypeptides found in vivo demonstrates that the order within the 200K primary translation product of cowpea mosaic virus bottom-component RNA is as follows: NH₂-32K polypeptide-58K polypeptide-VPg-24K polypeptide-87K polypeptide-COOH.     

Identification of a subset of herpesvirus saimiri polypeptides synthesized in the absence of virus DNA replication.

The effects of phosphonoacetic acid on the synthesis of herpesvirus saimiri-specific polypeptides in productively infected cells were examined. At concentrations that inhibited virus DNA synthesis (greater than or equal to 150 micrograms/ml), phosphonoacetic acid prevented the synthesis of the majority of virus-specific polypeptides while allowing the synthesis of a subset of virus proteins (i.e., 110,000 [110K], 76K, 72K, 51K, 48K, 29K, 24K, and 20K or 21K) and the protracted synthesis of host-specified polypeptides. Other inhibitors of DNA synthesis (e.g., cytosine arabinoside) showed the same selective inhibition of late virus protein synthesis and identified the same resistant subset of early virus-specific polypeptides. This DNA synthesis-independent subset included the 51K phosphoprotein, which, together with the 110K, 48K, and 31K polypeptides, accumulated in the nuclear fraction of infected cells.     

Inhibition of the accumulation of viral polypeptides in the densonucleosis virus-infected midgut of the silkworm,Bombyx mori,reared at a supraoptimal temperature

Effect of a supraoptimal temperature on the accumulation of viral polypeptides in the midgut was examined by immunoblot analysis in the larvae of the silkworm, Bombyx mori, infected with Bombyx densonucleosis virus type 2. In the larvae reared continuously at 25°C, viral polypeptides were first detected in the midgut at 2 days postinfection (pi) and in the feces at 4 days pi. When the larvae inoculated per os with the virus for 24 hr at 25°C were immediately shifted to 35°C, there were no detectable viral polypeptides in both the midgut and feces throughout the experiment. In the infected larvae shifted from 25° to 35°C at 48 hr pi, viral polypeptides preexisting in the midgut decreased to an undetectable level within 48 hr after the temperature shift, and no viral polypeptides were detected thereafter. Viral polypeptides in the feces of these larvae became detectable at 48 hr (4 days pi) after the temperature shift, as in the larvae at 25°C, and disappeared by 96 hr (6 days pi). These results indicate that a supraoptimal temperature inhibits accumulation of viral polypeptides in the midgut. It is likely that inhibited production of viral polypeptides rather than enhanced discharge of the infected midgut cells is responsible for the inhibited accumulation of viral polypeptides in the midgut at 35°C.     

Mixed-Linkage Ubiquitin Chains Send Mixed Messages

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Highlights? K48 and K63 linkages in branched and unbranched tri-Ub retain their structural features ? Linkage-selective receptors recognize K48 and K63 linkages in the branched tri-Ub ? Linkage-specific deubiquitinases cleave their cognate Ub-Ub linkages in the mixed-linkage chains ? The 26S proteasome recognizes and processes branched K48- and K63-linked tri-Ub     

Progress Towards the Understanding of the Gabaa Receptor Structure

Abstract

The GABA_A receptor of mammalian brain is a ligand-gated channel protein with allosteric binding sites for the benzodiazepines and barbiturate drugs. The receptor is an acidic oligomeric membrane glycoprotein and it has been purified to homogeneity from bovine cerebral cortex, bovine cerebellum and rat cerebral cortex by benzodiazepine affinity chromatography. In each case, extraction and purification with the zwitterionic detergent CHAPS and exogenous phospholipid has demonstrated the coexistence of GABA, benzodiazepine and cage convulsant ligand binding sites on a single protein complex; in addition the allosteric interactions between these sites are preserved in the isolated protein. The receptor has a heterologous structure that is conserved at the subunit level between the aforementioned mammalian species and brain regions. SDS-PAGE has shown that the receptor consists of two subunits, α (M_r 53000) and β (M_r 57000) present in equal stoichiometry. A model consistent with the determination of the molecular weight of the native protein, i.e., M_r 230,000, is that of a tetramer α₂β₂. [³H] Flunitrazepam and [³H]muscimol have been employed as photoaffinity labels to map the benzodiazepine and GABA binding polypeptides respectively. Polyclonal and monoclonal antibodies have been raised to the native bovine GABA_A receptor and these have been employed for the further characterisation of the receptor protein.     

Purification and characterization of the glycine receptor of pig spinal cord

A large-scale purification procedure was developed to isolate the glycine receptor of pig spinal cord by affinity chromatography on aminostrychnine agarose. After an overall purification of about 10 000-fold, the glycine receptor preparations contained three major polypeptides of Mr 48 000, 58 000, and 93 000. Photoaffinity labeling with [3H]strychnine showed that the [3H]strychnine binding site is associated with the Mr 48 000 and, to a much lesser extent, the Mr 58 000 polypeptides. [3H]Strychnine binding to the purified receptor exhibited a dissociation constant KD of 13.8 nM and was inhibited by the agonists glycine, taurine, and beta-alanine. Gel filtration and sucrose gradient centrifugation gave a Stokes radius of 7.1 nm and an apparent sedimentation coefficient of 9.6 S. Peptide mapping of the [3H]strychnine-labeled Mr 48 000 polypeptides of purified pig and rat glycine receptor preparations showed that the strychnine binding region of this receptor subunit is highly conserved between these species. Also, three out of six monoclonal antibodies against the glycine receptor of rat spinal cord significantly cross-reacted with their corresponding polypeptides of the pig glycine receptor. These results show that the glycine receptor of pig spinal cord is very similar to the well-characterized rat receptor protein and can be purified in quantities sufficient for protein chemical analysis.     

Protein Synthesis in a Lymantria dispar Cell Line Infected by Cytoplasmic Polyhedrosis Virus

The efficiency of replication of a cytoplasmic polyhedrosis virus isolated from a member of the order Lepidoptera, Euxoa scandens, was studied in eight different lepidopterean cell lines. Lymantria dispar cells, which were found to support viral replication, more efficiently, were used to follow the kinetics of appearance of viral-specific polypeptides by a 2-h pulse with [³⁵S]methionine. Five polypeptides (ca. 120,000 molecular weight [120K], 105K, 66K, 46K, and 28K) were identified as components of the polyhedral inclusion bodies, and two polypeptides (112K and 39K) were assigned as viral-particle polypeptides. All these polypeptides were present after 24 h and were still being produced 96 h after infection. The rate of synthesis of the major polyhedral polypeptide (28K) increased in the time course of infection, whereas the background of cellular polypeptides seemed to be unaffected. An indirect immunoperoxidase technique, after sodium dodecyl sulfate-polyacrylamide gel electrophoresis was blotted to a nitrocellulose membrane, showed that traces of the major polyhedral polypeptide were found from 8 h postinfection.     

Major oligomeric structural proteins of the HeLa nucleus

The three predominant polypeptides of the insoluble proteinaceous fraction from the HeLa cell nucleus polymerize in vitro upon oxidation of intrinsic sulfhydryl groups. The ease and specificity of this reaction indicate that these polypeptides exist as ordered oligomers in vivo. The comparable insoluble fraction from the rat liver nucleus also contains three predominant polypeptides of the same molecular weights, 65,000 71,000, and 75,000. The insoluble protein of the avian erythrocyte nuclear envelope consists principally of the 71,000- and the 75,000-dalton polypeptides. Indeed, in the avian erythrocyte nucleus these are the predominant polypeptides of the entire nucleus (Shelton, K., Cobbs, C., Povlishock, J. and Burkat, R., 1976, Arch. Biochem. Biophys.174, 177). Further, these avian polypeptides each form homogeneous covalently linked oligomers upon sulfhydryl oxidation (Cochran, D., Cobbs, C. and Shelton, K., 1977, J. Cell Biol.75, 151a). The insolubility, oligomeric disposition, and relative prominence of these polypeptides in a wide variety of cells indicate a fundamental structural role in the nucleus. Morphological features which may reflect this structural or skeletal role could be the nuclear envelope, the fibrous lamina, or perhaps an intrachromatinic matrix. The metabolism of the oligomeric polypeptides has been investigated in HeLa cells. Turnover of the HeLa insoluble nuclear protein is similar to that of the histones which are known to be stable proteins. The insoluble protein, including the oligomeric polypeptides, is synthesized in G1, S, and G2 phases of the cell cycle. This metabolic behavior indicates that the oligomeric polypeptides are reutilized in successive cell cycles and that synthesis accompanies nuclear and cellular expansion rather than deoxyribonucleohistone synthesis. This suggests that neither degradation nor selective synthesis of oligomeric polypeptides at a particular phase of the cell cycle are responsible for the breakdown and reformation of the interphase cell morphological features that occur during mitosis.     

A phloem-specific,lectin-like protein is located in pine sieve-element plastids by immunocytochemistry

Two co-purifying phloem polypeptides of 24 and 25 kilodaltons (kDa) were isolated from homogenates of Pinus sabiniana Dougl. phloem by differential centrifugation, selective solubilization and electrophoresis, and rabbit antibodies raised against them. The antisera were found to be specific for doublet bands between 23 and 25 kDa in Western blots of whole phloem extracts of Pinus species; no xylem polypeptides were labelled, nor did labelling occur in blots of phloem extracts from other genera in the Pinaceae. Solubilized phloem polypeptides bind strongly to chitin (oligomeric N-acetylglucosamine) columns and are sensitive to thiol reagents, both characteristics which relate them to phloemspecific lectins isolated from angiosperm species (C. Allen, 1979, Biochem. J. 183, 133–137; A.K. Gietl et al., 1979, Planta 144, 367–371). Fluorescence microscopy and immuno-gold electron microscopic cytochemistry demonstrated antigenic sites specifically associated with protein crystals peculiar to the sieve-element plastids of the Pinaceae.Abbreviations DAB diamino benzidine tetrachloride - FITC fluorescein isothiocyanate - kDa kilodalton - PBS phosphate-buffered saline - PP phloem polypeptide(s) - SDS-PAGE Sodium dodecyl sulphate-polyacrylamide gel electrophoresis - Tris 2-amino-2-(hydroxymethyl)-1,3-propanediol     

Luteolin suppresses androgen receptor-positive triple-negative breast cancer cell proliferation and metastasis by epigenetic regulation of MMP9 expression via the AKT/mTOR signaling pathway

BackgroundTriple-negative breast cancer (TNBC) represents up to 20% of all breast cancers. This cancer lacks the expression of the estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. The current therapeutic strategy for patients with this subtype is the use of cytotoxic chemotherapy and surgery. Luteolin is a natural herbal flavonoid and a potential therapeutic candidate for multiple diseases. The use of a treatment that combines Chinese herbal medicine and western medicine is rising in Asia.PurposeThe present study evaluates the effects and molecular mechanisms involved with luteolin treatment and evaluates whether this herb affects androgen receptor-positive breast cancer cell proliferation or metastasis.Study DesignIn vitro evaluation of the effect of luteolin on androgen receptor-positive TNBC cell proliferation and metastasisMethodsCell viability analysis was used for the cytotoxicity test. Colony formation and Bromodeoxyuridine (BrdU) staining-based proliferation experiments were used for cell proliferation. Wound healing and transwell assays were used for in vitro migration/invasion. The RT-qPCR analysis was used for gene expression. Furthermore, ChIP-qPCR analysis was used for epigenetic modification of gene promoters.ResultsLuteolin significantly inhibited the proliferation and metastasis of androgen receptor-positive TNBC. Furthermore, luteolin inactivated the AKT/mTOR signaling pathway and reversed the epithelial-mesenchymal transition (EMT). The combination of luteolin and inhibitors of AKT/mTOR synergistically repressed an androgen receptor-positive TNBC cell proliferation and metastasis. Luteolin also downregulated MMP9 expression by decreasing the levels of the AKT/mTOR promoting H3K27Ac and H3K56A on the MMP9 promoter region.ConclusionOur findings indicate that luteolin inhibited the proliferation and metastasis of androgen receptor-positive TNBC by regulating MMP9 expression through a reduction in the levels of AKT/mTOR-inducing H3K27Ac and H3K56Ac.     

Association of adenovirus type 2 early proteins with a soluble complex that synthesizes adenovirus DNA in vitro

A soluble Ad2 DNA synthesizing complex was prepared from Ad2-infected KB cell nuclei and purified by exclusion chromatography on a BioGel A-50m column. The purified complex was able to synthesize DNA from all regions of the virus genome, as indicated by $\text{Eco}$RI restriction endonuclease analysis of $\text{in vitro}$ labeled DNA. Experiments were performed to identify Ad2-induced early polypeptides present in the complex. Ad2-infected and mock-infected cells were labeled with [³⁵S]methionine 7–10 h postinfection, then incubated for 8 h to allow the ³⁵S-labeled early polypeptides to become associated with the complex. The polypeptides in the purified complex and each of the cell fractions were identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis and autoradiography. The major components of the purified complex were the 73K DNA binding phosphoprotein and 11K, two adenovirus 2-induced early polypeptides. The 11K has a preferred nuclear location. Small quantities of other Ad2-induced early proteins, 21K, 15K, and possibly 8.3K were also associated with the complex.     

Water-soluble acetylcholine receptor from Torpedo californica. Solubilization,purification and characterization

The nicotinic acetylcholine receptor from electrogenic tissue of Torpedo californica was solubilized by tryptic digestion of membrane fragments obtained from autolysed tissue, without use of detergent. The water-soluble acetylcholine receptor was purified by affinity chromatography on a cobra-toxin-Sepharose resin. The purified receptor bound 4000–6000 pmol per mg protein of α-[¹²⁵]bungarotoxin, and toxin-binding was specifically inhibited by cholinergic ligands. Gel filtration revealed a single molecular species of Stokes radius $\text{125 ± 10}$ Å and on sucrose gradient centrifugation one major peak was observed of 20–22 S. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and β-mercaptoethanol revealed two major polypeptides of mol. wt. 30 000 and 48 000.     

泛素链的体外制备、磷酸化修饰与标记方法

目的 为了制备不同链种类、不同链长及磷酸化修饰的泛素样品。方法 本文主要以生物酶法为手段对以上样品的制备路线进行阐述。制备的主要方法分为两种,一是采用逐次添加的方式达到泛素链延长的目的,二是通过一次酶反应制备混合的多聚泛素链,然后对不同链长的泛素链进行纯化分离。结果 以上两种策略都能达到制备多聚泛素链的目的。进一步,通过对泛素进行磷酸化修饰,制备了磷酸化的泛素样品。通过K11和K48的泛素酶制备了K11/K48分支链泛素。结论 基于以上泛素链的制备路线,可以进一步对不同链接形式的不同亚基进行磷酸化修饰等翻译后修饰,也可以通过在特定亚基进行同位素标记及在特定位点引入小分子探针,进而进行NMR和FRET的测定。综上所述,本方法将为从事泛素信号通路和泛素生化研究的科学家提供借鉴和帮助。     

PROTEIN PROFILES OF RAT EMBRYO CEREBRAL CELLS DURING DIFFERENTIATION IN CULTURE

The protein composition of the particulate fraction of dissociated foetal rat cerebral cells during maturation in culture was investigated. SDS polyacrylamide gel electrophoresis showed a general decrease in the histonal components and significant changes in composition of a group of polypeptides with molecular weights ranging from 42 to 60 K. Two of these polypeptides coelectrophoresed with tubulin and actin whereas a 48 K polypeptide comigrated with the major component of the Wolfgram myelin protein. Its relative quantity appeared to approach a plateau after 8 days in culture. The myelin basic and proteolipid proteins were below detection levels in cultured cells at any time point investigated. A group of polypeptides with estimated molecular weights of 47, 51 and 52 K possibly representing synaptic proteins increased with time in culture. The appearance of a prominent band (60 K) in brain cultures and in other cells of divergent origin was demonstrated. This protein may be related to the process of cell adaptation to culture conditions. The developmental changes in the protein profile are discussed in the context of an in vitro myelinogenesis and synaptogenesis and compared with whole brain particulate and subcellular fractions.     

Immunological and Chemical Identification of Intracellular Forms of Adenovirus Type 2 Terminal Protein

Highly purified adenovirus type 2 terminal protein (TP) with an apparent M_r of 55,000 (55K) was prepared in quantities of 10 to 30 μg from guanidine hydrochloride- or sodium dodecyl sulfate-disrupted virions (60 to 120 mg). Guinea pigs were immunized with 14 to 20 injections of TP in amounts of 1 to 2 μg. Antiserum to TP was used to study the intracellular polypeptides related to adenovirus type 2 TP. By immunoprecipitation with anti-TP serum, we identified 80K and 76K polypeptides in the nucleoplasmic and cytoplasmic S100 fractions of [³⁵S]methionine-labeled cells early and late after infection with Ad2. By immunoautoradiographic analysis which eliminates coprecipitation of unrelated proteins, we identified an 80K polypeptide (probably an 80K-76K doublet) in unlabeled, late infected cells, using anti-TP serum and ¹²⁵I-labeled staphylococcal protein A. About two- to threefold-higher levels of the 80K and 76K polypeptides were present in the nucleoplasm than in the S100 fraction, and two- to threefold-higher levels were found in late infected cells than in early infected cells (cycloheximide enhanced, arabinofuranosylcytosine treated). We did not detect the 80K or 76K polypeptide in uninfected cells, indicating that these polypeptides are virus coded. Tryptic peptide map analysis showed that the 80K and 76K polypeptides are very closely related and that they share peptides with the DNA-bound 55K TP. Our data provide the first direct demonstration of intracellular 80K and 76K forms of TP. The intracellular 80K and 76K polypeptides are closely related or identical to the 80K polypeptide that Challberg and co-workers (Proc. Natl. Acad. Sci. U.S.A. 77:5105-5109, 1980) detected at the termini of adenovirus DNA synthesized in vitro and to the 87K polypeptide that Stillman and co-workers (Cell 23:497-508, 1981) translated in vitro. We did not detect the 55K TP in early or late infected cells, consistent with the proposal by Challberg and co-workers that the 80K polypeptide is a precursor to the virion-bound TP and that the conversion of the 80K polypeptide to the 55K TP occurs during virus maturation. The 80K and 76K polypeptides have many more methionine-containing tryptic peptides than does the 55K TP, and most of the tryptic peptides unique to the 80K and 76K polypeptides are very hydrophobic. Thus, the conversion of the 80K and 76K polypeptides to the 55K TP may involve the removal of a specific hydrophobic protein region.     

Antibody response to respiratory syncytial virus structural proteins in children with acute respiratory syncytial virus infection.

The purified respiratory syncytial virus (RSV), Randall strain contained 10 polypeptides (72,000 molecular weight [72K], 66K, 48K, 42K, 40K, 36K, 30K, 23K, 18K, and 15K), 8 of which proved to be virus specific, and polypeptides 48K and 23K were glycosylated. In addition, a high-molecular-weight (150K), virus-specific glycopolypeptide was immunoprecipitated from RSV-infected cell lysate. The antibody response in human sera serially collected from children with primary RSV infection was mainly directed against the polypeptides 30K, 48K, and 72K. The immune response against the other viral proteins was also already detectable in the acute-phase sera. These results indicate that the immune response in RSV infection differs significantly from those for other diseases caused by paramyxoviruses.     

Fluvoxamine and sigma-1 receptor agonists dehydroepiandrosterone (DHEA)-sulfate induces the Ser473-phosphorylation of Akt-1 in PC12 cells

AimsThe expression of brain-derived neurotrophic factor (BDNF) may be a downstream target of a variety of antidepressant treatments, and selective serotonin reuptake inhibitors (SSRIs) are used clinically for the treatment of depression. BDNF binds to and activates tyrosine kinases receptor (TrkB) to exert its effects. TrkB, after activation by ligands, stimulates phosphoinositide 3-kinase (PI3K). The downstream target of PI3K is Akt-1, a serine-threonine kinase. BDNF has signaling through the PLC-?IP₃/Ca²⁺ pathway. Furthermore, the PLC-?γ/IP₃/Ca²⁺ pathway is regulated by the sigma-1 receptors. Here, we examined whether fluvoxamine (FLV) activated Akt-1 and increased phosphorylation of Akt-1 via sigma-1 receptor in PC12 cells.Main methodsWe examined the effect of the SSRI, FLV and BDNF on the phosphorylation levels of serine-threonine kinase Akt-1 in PC12 cells using immunoblotting techniques.Key findingsTreatment with 10 μM and 100 μM FLV of PC12 cells stimulated a 2.4- and 3.8-fold maximal increase in Ser⁴⁷³-phosphorylated Akt-1 levels at 40 min, respectively. Treatment with 50 ng/ml BDNF also stimulated Ser⁴⁷³ -phosphorylated Akt-1 by 2.6-fold with a maximal increase at 5 min. In addition, the phosphorylation induced by FLV and BDNF was blocked by LY294002, a selective inhibitor of PI3K. The sigma-1 receptor agonists dehydroepiandrosterone (DHEA)-sulfate also stimulated a 2.1-fold increase in the level of Ser473-phosphorylated Akt-1.SignificanceThis study demonstrates that fluvoxamine treatment rapidly increased phosphorylation of Akt-1. And BDNF activated Akt-1 phosphorylation by the TrkB/PI3K/Akt-1 pathway. We conclude that the phosphorylation of Akt-1, downstream of PI3K, was the key to their antidepressant effects.