Effect of hemin, baicalein and heme oxygenase-1 (HO-1) enzyme activity inhibitors on Cd-induced accumulation of HO-1, HSPs and aggresome-like structures in Xenopus kidney epithelial cells.

Cadmium is a highly toxic environmental pollutant that can cause many adverse effects including cancer, neurological disease and kidney damage. Aquatic amphibians are particularly susceptible to this toxicant as it was shown to cause developmental abnormalities and genotoxic effects. In mammalian cells, the accumulation of heme oxygenase-1 (HO-1), which catalyzes the breakdown of heme into CO, free iron and biliverdin, was reported to protect cells against potentially lethal concentrations of CdCl.

Effect of isothiocyanates, BITC and PEITC, on stress protein accumulation, protein aggregation and aggresome-like structure formation in Xenopus A6 kidney epithelial cells.

Numerous studies have elucidated the health benefits of organosulfur compounds, known as isothiocyanates (ITCs), derived from cruciferous vegetables. As electrophiles, ITCs have the ability to directly bind and modify thiol-containing compounds such as glutathione and cellular protein, including tubulin. While the biochemical effects of ITCs have been well characterized, less information is available regarding their effects on the accumulation of stress-inducible heme oxygenase-1 (HO-1), heat shock proteins (HSPs) and the possible formation of aggregated protein due to thiol modification.

Characterization of cadmium chloride-induced BiP accumulation in Xenopus laevis A6 kidney epithelial cells.

Endoplasmic reticulum (ER) stress can result in the accumulation of unfolded/misfolded protein in the ER lumen, which can trigger the unfolded protein response (UPR) resulting in the activation of various genes including immunoglobulin-binding protein (BiP; also known as glucose-regulated protein 78 or HSPA5). BiP, an ER heat shock protein 70 (HSP70) family member, binds to unfolded protein, inhibits their aggregation and re-folds them in an ATP-dependent manner. While cadmium, an environmental contaminant, was shown to induce the accumulation of HSP70 in vertebrate cells, less information is available regarding the effect of this metal on BiP accumulation or function.

The expression and function of hsp30-like small heat shock protein genes in amphibians, birds, fish, and reptiles.

Small heat shock proteins (sHSPs) are a superfamily of molecular chaperones with important roles in protein homeostasis and other cellular functions. Amphibians, reptiles, fish and birds have a shsp gene called hsp30, which was also referred to as hspb11 or hsp25 in some fish and bird species. Hsp30 genes, which are not found in mammals, are transcribed in response to heat shock or other stresses by means of the heat shock factor that is activated in response to an accumulation of unfolded protein.

Expression and localization of the Xenopus laevis small heat shock protein, HSPB6 (HSP20), in A6 kidney epithelial cells.

Small heat shock proteins (sHSPs) are molecular chaperones that bind to unfolded protein, inhibit the formation of toxic aggregates and facilitate their refolding and/or degradation. Previously, the only sHSPs that have been studied in detail in the model frog system, Xenopus laevis, were members of the HSP30 family and HSPB1 (HSP27). We now report the analysis of X.

The small heat shock protein, HSP30, is associated with aggresome-like inclusion bodies in proteasomal inhibitor-, arsenite-, and cadmium-treated Xenopus kidney cells.

In the present study, treatment of Xenopus laevis A6 kidney epithelial cells with the proteasomal inhibitor, MG132, or the environmental toxicants, sodium arsenite or cadmium chloride, induced the accumulation of the small heat shock protein, HSP30, in total and in both soluble and insoluble protein fractions. Immunocytochemical analysis revealed the presence of relatively large HSP30 structures primarily in the perinuclear region of the cytoplasm. All three of the stressors promoted the formation of aggresome-like inclusion bodies as determined by immunocytochemistry and laser scanning confocal microscopy using a ProteoStat aggresome dye and additional aggresomal markers, namely, anti-γ-tubulin and anti-vimentin antibodies.

Fluoxetine-induced transactivation of the platelet-derived growth factor type β receptor reveals a novel heterologous desensitization process.

Many G protein-coupled receptors (GPCRs), including serotonin (5-HT) receptors promote the activity of receptor tyrosine kinases (RTKs) via intracellular signaling pathways in a process termed transactivation. Although transactivation pathways are commonly initiated by a GPCR, a recent report demonstrated that serotonin-selective reuptake inhibitors (SSRIs) were able to block 5-HT-induced transactivation of the platelet-derived growth factor (PDGF) type β receptor. We show that a 45 min pretreatment of SH-SY5Y cells with the SSRI fluoxetine indeed blocked 5-HT-induced transactivation of the PDGFβ receptor.

Differential expression of the seven rRNA operon promoters from the plant growth-promoting bacterium Pseudomonas sp. UW4.

Bacteria often have multiple copies of ribosomal RNA (rrn) genes in their genomes. The presence of multiple rrn operons suggests an advantage to the organism, perhaps through adjustable control of protein expression in response to altered environmental conditions. In the work described here, the strengths of the seven rRNA promoters of Pseudomonas sp.

Accumulation of heme oxygenase-1 (HSP32) in Xenopus laevis A6 kidney epithelial cells treated with sodium arsenite, cadmium chloride or proteasomal inhibitors.

The present study examined the effect of sodium arsenite, cadmium chloride, heat shock and the proteasomal inhibitors MG132, withaferin A and celastrol on heme oxygenase-1 (HO-1; also known as HSP32) accumulation in Xenopus laevis A6 kidney epithelial cells. Immunoblot analysis revealed that HO-1 accumulation was not induced by heat shock but was enhanced by sodium arsenite and cadmium chloride in a dose- and time-dependent fashion. Immunocytochemistry revealed that these metals induced HO-1 accumulation in a granular pattern primarily in the cytoplasm.

Distinct patterns of HSP30 and HSP70 degradation in Xenopus laevis A6 cells recovering from thermal stress.

Heat shock proteins (HSPs) are molecular chaperones that assist in protein synthesis, folding and degradation and prevent stress-induced protein aggregation. In this study, we examined the pattern of accumulation of HSP30 and HSP70 in Xenopus laevis A6 kidney epithelial cells recovering from heat shock. Immunoblot analysis revealed the presence of elevated levels of HSP30 after 72h of recovery.

Reactive oxygen species are required for 5-HT-induced transactivation of neuronal platelet-derived growth factor and TrkB receptors, but not for ERK1/2 activation.

High concentrations of reactive oxygen species (ROS) induce cellular damage, however at lower concentrations ROS act as intracellular second messengers. In this study, we demonstrate that serotonin (5-HT) transactivates the platelet-derived growth factor (PDGF) type β receptor as well as the TrkB receptor in neuronal cultures and SH-SY5Y cells, and that the transactivation of both receptors is ROS-dependent. Exogenous application of H₂O₂ induced the phosphorylation of these receptors in a dose-dependent fashion, similar to that observed with 5-HT.

Enhanced HSP30 and HSP70 accumulation in Xenopus cells subjected to concurrent sodium arsenite and cadmium chloride stress.

Heat shock proteins (HSPs) are molecular chaperones that aid in protein folding, translocation and in preventing stress-induced protein aggregation. The present study examined the effect of simultaneous sodium arsenite and cadmium chloride treatment on the pattern of HSP30 and HSP70 accumulation in A6 kidney epithelial cells of the frog, Xenopus laevis. Immunoblot analysis revealed that HSP30 and HSP70 accumulation in concurrent stressor treatments were significantly higher than the sum of HSP30 or HSP70 accumulation in individual treatments.

Acute 5-HT7 receptor activation increases NMDA-evoked currents and differentially alters NMDA receptor subunit phosphorylation and trafficking in hippocampal neurons.

Background: N-methyl-D-aspartate (NMDA) receptors are regulated by several G protein-coupled receptors (GPCRs) as well as receptor tyrosine kinases. Serotonin (5-HT) type 7 receptors are expressed throughout the brain including the thalamus and hippocampus. Long-term (2-24 h) activation of 5-HT7 receptors promotes the expression of neuroprotective growth factor receptors, including the platelet-derived growth factor (PDGF) β receptors which can protect neurons against NMDA-induced neurotoxicity.

The complete genome sequence of the plant growth-promoting bacterium Pseudomonas sp. UW4.

The plant growth-promoting bacterium (PGPB) Pseudomonas sp. UW4, previously isolated from the rhizosphere of common reeds growing on the campus of the University of Waterloo, promotes plant growth in the presence of different environmental stresses, such as flooding, high concentrations of salt, cold, heavy metals, drought and phytopathogens. In this work, the genome sequence of UW4 was obtained by pyrosequencing and the gaps between the contigs were closed by directed PCR.

5-Hydroxytryptamine type 7 receptor neuroprotection against NMDA-induced excitotoxicity is PDGFβ receptor dependent.

The serotonin (5-HT) type 7 receptor is expressed throughout the CNS including the hippocampus. Long-term (2-24 h) activation of 5-HT7 receptors regulates growth factor receptor expression, including the expression of platelet-derived growth factor (PDGF) β receptors. Direct activation of PDGFβ receptors in primary hippocampal and cortical neurons inhibits NMDA receptor activity and attenuates NMDA receptor-induced neurotoxicity.

Withaferin A induces proteasome inhibition, endoplasmic reticulum stress, the heat shock response and acquisition of thermotolerance.

In the present study, withaferin A (WA), a steroidal lactone with anti-inflammatory and anti-tumor properties, inhibited proteasome activity and induced endoplasmic reticulum (ER) and cytoplasmic HSP accumulation in Xenopus laevis A6 kidney epithelial cells. Proteasomal inhibition by WA was indicated by an accumulation of ubiquitinated protein and a decrease in chymotrypsin-like activity. Additionally, immunoblot analysis revealed that treatment of cells with WA induced the accumulation of HSPs including ER chaperones, BiP and GRP94, as well as cytoplasmic/nuclear HSPs, HSP70 and HSP30.

5-HT(1A) receptors transactivate the platelet-derived growth factor receptor type beta in neuronal cells.

In the absence of ligand, certain growth factor receptors can be activated via G-protein coupled receptor (GPCR) activation in a process termed transactivation. Serotonin (5-HT) receptors can transactivate platelet-derived growth factor (PDGF) β receptors in smooth muscle cells, but it is not known if similar pathways occur in neuronal cells. Here we show that 5-HT can transiently increase the phosphorylation of PDGFβ receptors through 5-HT(1A) receptors in a time- and dose-dependent manner in SH-SY5Y neuroblastoma cells.

Activation of 5-HT7 receptors increases neuronal platelet-derived growth factor β receptor expression.

Several antipsychotics have a high affinity for 5-HT7 receptors yet despite intense interest in the 5-HT7 receptor as a potential drug target to treat psychosis, the function and signaling properties of 5-HT7 receptors in neurons remain largely uncharacterized. In primary mouse hippocampal and cortical neurons, as well as in the SH-SY5Y cell line, incubation with 5-HT, 5-carboxamidotryptamine (5-CT), or 5-HT7 receptor-selective agonists increases the expression of platelet-derived growth factor (PDGF)β receptors. The increased PDGFβ receptor expression is cyclic AMP-dependent protein kinase (PKA)-dependent, suggesting that 5-HT7 receptors couple to Gα(s) in primary neurons.

Sodium arsenite and cadmium chloride induction of proteasomal inhibition and HSP accumulation in Xenopus laevis A6 kidney epithelial cells.

Sodium arsenite (NA) and cadmium chloride (CdCl(2)) are relatively abundant environmental toxicants that have multiple toxic effects including carcinogenesis, dysfunction of gene regulation and DNA and protein damage. In the present study, treatment of Xenopus laevis A6 kidney epithelial cells with concentrations of NA (20-30 μM) or CdCl(2) (100-200 μM) that induced HSP30 and HSP70 accumulation also produced an increase in the relative levels of ubiquitinated protein. Actin protein levels were unchanged in these experiments.

Curcumin-induced inhibition of proteasomal activity, enhanced HSP accumulation and the acquisition of thermotolerance in Xenopus laevis A6 cells.

In the present study, curcumin, a phenolic compound with anti-inflammatory, anti-tumor and anti-amyloid properties, inhibited proteasomal activity and induced the accumulation of HSPs in the frog model system, Xenopus laevis. Treatment of A6 kidney epithelial cells with curcumin enhanced ubiquitinated protein levels and inhibited chymotrypsin-like activity. Furthermore, exposure of cells to 10-50 μM curcumin for 24h induced HSP30 and HSP70 accumulation.

Celastrol can inhibit proteasome activity and upregulate the expression of heat shock protein genes, hsp30 and hsp70, in Xenopus laevis A6 cells.

In eukaryotes, the ubiquitin-proteasome system (UPS) is responsible for the degradation of most proteins. Proteasome inhibition, which has been associated with various diseases, can cause alterations in various intracellular processes including the expression of heat shock protein (hsp) genes. In this study, we show that celastrol, a quinone methide triterpene and anti-inflammatory agent, inhibited proteasome activity and enhanced HSP accumulation in Xenopus laevis A6 kidney epithelial cells.

Heat shock protein gene expression and function in amphibian model systems.

Heat shock proteins (HSPs) are molecular chaperones that are involved in protein folding and translocation. During heat shock, both constitutive and stress-inducible HSPs bind to and inhibit irreversible aggregation of denatured protein and facilitate their refolding once normal cellular conditions are re-established. Recent interest in HSPs has been propelled by their association with various human diseases.

Proteasome inhibition induces hsp30 and hsp70 gene expression as well as the acquisition of thermotolerance in Xenopus laevis A6 cells.

Previous studies have shown that inhibiting the activity of the proteasome leads to the accumulation of damaged or unfolded proteins within the cell. In this study, we report that proteasome inhibitors, lactacystin and carbobenzoxy-L-leucyl-L-leucyl-L-leucinal (MG132), induced the accumulation of ubiquitinated proteins as well as a dose- and time-dependent increase in the relative levels of heat shock protein (HSP)30 and HSP70 and their respective mRNAs in Xenopus laevis A6 kidney epithelial cells. In A6 cells recovering from MG132 exposure, HSP30 and HSP70 levels were still elevated after 24 h but decreased substantially after 48 h.

Simultaneous exposure of Xenopus A6 kidney epithelial cells to concurrent mild sodium arsenite and heat stress results in enhanced hsp30 and hsp70 gene expression and the acquisition of thermotolerance.

In this study, we examined the effect of concurrent low concentrations of sodium arsenite and mild heat shock temperatures on hsp30 and hsp70 gene expression in Xenopus A6 kidney epithelial cells. RNA blot hybridization and immunoblot analysis revealed that exposure of A6 cells to 1-10 microM sodium arsenite at a mild heat shock temperature of 30 degrees C enhanced hsp30 and hsp70 gene expression to a much greater extent than found with either stress individually. In cells treated simultaneously with 10 microM sodium arsenite and different heat shock temperatures, enhanced accumulation of HSP30 and HSP70 protein was first detected at 26 degrees C with larger responses at 28 and 30 degrees C.

Examination of cadmium-induced expression of the small heat shock protein gene, hsp30, in Xenopus laevis A6 kidney epithelial cells.

Cadmium is a highly toxic environmental pollutant that has been classified as a human carcinogen. Toxicological responses to cadmium exposure include respiratory diseases, neurological disorders and kidney damage. In the present study, we have characterized the effect of cadmium on the accumulation of the small heat shock protein (HSP), HSP30, in Xenopus laevis A6 kidney epithelial cells.