The motif of SPARC that inhibits DNA synthesis is not a nuclear localization signal

SPARC (secreted protein acidic and rich in cysteine), although primarily known as a secreted, matricellular protein, has also been identified in urothelial cell nuclei. Many biological activities, including inhibition of cell adhesion and repression of DNA synthesis, have been ascribed to SPARC, but the influence of its intracellular localization on each of these activities is unknown. When exposed by epitope retrieval and nuclear matrix unmasking techniques, endogenous SPARC was found to localize strongly to the nuclei and the nuclear matrix of cultured urothelial cells. Live-cell time-lapse imaging revealed that exogenous fluorescently labeled recombinant (r) SPARC was taken up from medium over a 16 h period and accumulated inside cells. Two variants of rSPARC with alterations in its putative nuclear localization signal (NLS) were generated to investigate the existence and effects of the NLS. These variants demonstrated similar biophysical characteristics as the wild-type protein. Visualization by a variety of techniques, including live-cell imaging, deconvolution microscopy, and cell fractionation, all concurred that exogenous rSPARC was not able to localize to cell nuclei, but instead accumulated as perinuclear clusters. Localization of the rSPARC NLS variants was no different than wild-type, arguing against the presence of an active NLS in rSPARC. Imaging experiments showed that only permeabilized, dead cells avidly took up rSPARC into their nuclei. The rSPARC(no NLS) variant proved ineffective at inhibiting DNA synthesis, whereas the rSPARC(strong NLS) variant was a more potent inhibitor of DNA synthesis than was wild-type rSPARC. The motif of SPARC that inhibits the synthesis of urothelial cell DNA is therefore not a nuclear localization signal, but its manipulation holds therapeutic potential to generate a "Super-SPARC" that can quiesce proliferative tissues.     

Sts1 can overcome the loss of Rad23 and Rpn10 and represents a novel regulator of the ubiquitin/proteasome pathway

A rad23Delta rpn10Delta double mutant accumulates multi-Ub proteins, is deficient in proteolysis, and displays sensitivity to drugs that generate damaged proteins. Overexpression of Sts1 restored normal growth in rad23Delta rpn10Delta but did not overcome the DNA repair defect of rad23Delta. To understand the nature of Sts1 suppression, we characterized sts1-2, a temperature-sensitive mutant. We determined that sts1-2 was sensitive to translation inhibitors, accumulated high levels of multi-Ub proteins, and caused stabilization of proteolytic substrates. Additionally, ubiquitinated proteins that were detected in proteasomes were inefficiently cleared in sts1-2. Despite these proteolytic defects, overall proteasome activity was increased in sts1-2. We propose that Sts1 is a new regulatory factor in the ubiquitin/proteasome pathway that controls the turnover of proteasome substrates.     

Epstein-barr virus-induced resistance to drugs that activate the mitotic spindle assembly checkpoint in Burkitt's lymphoma cells

Epstein-Barr virus (EBV) is associated with a number of human cancers, and latent EBV gene expression has been reported to interfere with cell cycle checkpoints and cell death pathways. Here we show that latent EBV can compromise the mitotic spindle assembly checkpoint and rescue Burkitt's lymphoma (BL)-derived cells from caspase-dependent cell death initiated in aberrant mitosis. This leads to unscheduled mitotic progression, resulting in polyploidy and multi- and/or micronucleation. The EBV latent genes responsible for this phenotype are expressed from the P3HR1 strain of virus and several viruses with similar genomic deletions that remove the EBNA2 gene. Although EBNA2 and the latent membrane proteins are not expressed, the EBNA3 proteins are present in these BL cells. Survival of the EBV-positive cells is not consistently associated with EBV lytic gene expression or with the genes that are expressed in EBV latency I BL cells (i.e., EBNA1, EBERs, and BARTs) but correlates with reduced expression of the cellular proapoptotic BH3-only protein Bim. These data suggest that a subset of latent EBV gene products may increase the likelihood of damaged DNA being inherited because of the impaired checkpoint and enhanced survival capacity. This could lead to greater genetic diversity in progeny cells and contribute to tumorigenesis. Furthermore, since it appears that this restricted latent EBV expression interferes with the responses of Burkitt's lymphoma-derived cells to cytotoxic drugs, the results of this study may have important therapeutic implications in the treatment of some BL.     

Rare coexistence of keratinizing squamous metaplasia with xanthogranulomatous pyelonephritis. Report of a case with the role of immunocytochemistry in the differential diagnosis

BACKGROUND: Xanthogranulomatous pyelonephritis (XPN), a rare form ofchronicpyelonephritis, is commonly associated with lithiasis and rarely leads to keratinizing squamous metaplasia. Its manifestations closely mimic those of a renal neoplasm, leading to misdiagnosis of malignancy, often resulting in radical nephrectomy. The role of immunocytochemistry in the preoperative cytologic diagnosis is assessed in the present case report. CASE: A 20-year-old male presented with fever and an enlarging mass in the right renal angle. Ultrasonography revealed a heterogeneous mass in the renal pelvis. Fine needle aspiration cytology was advised to rule out malignancy. Aspiration smears from the mass showed many dissociated cells and clusters of them with abundant vacuolated cytoplasm, vesicular nuclei and prominent nucleoli in some cells. Many desquamated metaplastic squamous cells were also seen. The background was predominantly necrotic, with inflammatory cells. The cytologic possibility of XPN with squamous metaplasia vs. renal cell carcinoma was considered. Immunocytochemical markers, epithelial membrane antigen (EMA) and CD68 (histiocytic marker) were used to determine the nature of the suspicious vacuolated cells; these cells were immunoreactive for CD68 and negative for EMA, thus confirming the cytologic diagnosis of XPN with keratinizing squamous metaplasia. CONCLUSION: The case highlights the presence of metaplastic squamous cells in XPN in smears for the first time. Immunocytochemistry is an essential tool in the preoperative cytologic diagnosis of XPN. The patient can be managed conservatively with antibiotics.     

The structural topology of wild-type phospholamban in oriented lipid bilayers using 15N solid-state NMR spectroscopy

For the first time, 15N solid-state NMR experiments were conducted on wild-type phospholamban (WT-PLB) embedded inside mechanically oriented phospholipid bilayers to investigate the topology of its cytoplasmic and transmembrane domains. 15N solid-state NMR spectra of site-specific 15N-labeled WT-PLB indicate that the transmembrane domain has a tilt angle of 13 degrees+/-6 degrees with respect to the POPC (1-palmitoyl-2-oleoyl-sn-glycero-phosphocholine) bilayer normal and that the cytoplasmic domain of WT-PLB lies on the surface of the phospholipid bilayers. Comparable results were obtained from site-specific 15N-labeled WT-PLB embedded inside DOPC/DOPE (1,2-dioleoyl-sn-glycero-3-phosphocholine/1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) mechanically oriented phospholipids' bilayers. The new NMR data support a pinwheel geometry of WT-PLB, but disagree with a bellflower structure in micelles, and indicate that the orientation of the cytoplasmic domain of the WT-PLB is similar to that reported for the monomeric AFA-PLB mutant.     

Synthesis and evaluation of antifungal properties of a series of the novel 2-amino-5-oxo-4-phenyl-5,6,7,8-tetrahydroquinoline-3-carbonitrile and its analogues

A series of 2-amino-5-oxo-4-phenyl-5,6,7,8-tetrahydroquinoline-3-carbonitrile and various analogues have been synthesized in excellent isolated yields starting from various arylidenemalononitrile and 3-amino-2-cyclohexen-1-one in 1-propanol as solvent at reflux temperature in the absence of any added catalyst. All the synthesized compounds were evaluated for their antifungal activity. The relationship between functional group variation and biological activity of the evaluated compounds is discussed in the article.     

Application of response surface methodology to cell immobilization for the production of palatinose

Response surface methodology (RSM), based on multivariate non-linear model, was applied to study the interactions and optimization of the immobilization parameters for cell entrapment, namely alginate concentration, cell loading and bead diameter using Erwinia rhapontici NCPPB 1578 that produced palatinose. ANOVA analysis and statistical parameters calculations showed that RSM could be used effectively to model and improve a complex system like cell immobilization. Palatinose yield was increased by 40%. The maximum yield of 140 mg/ml was achieved in a batch of 1h at alginate concentration of 5% w/v, cell loading of 5 g l(-1) and 2.25 mm bead diameter. Thus, the E. rhapontici NCPPB 1578 immobilization in alginate bead and subsequent palatinose yield was successfully improved by application of RSM technique.