Relationship between circulating FSH levels and body composition and bone health in patients with prostate cancer who undergo androgen deprivation therapy: The BLADE study

Background

Among its extragonadal effects, follicle-stimulating hormone (FSH) has an impact on body composition and bone metabolism. Since androgen deprivation therapy (ADT) has a profound impact on circulating FSH concentrations, this hormone could potentially be implicated in the changes of fat body mass (FBM), lean body mass (LBM), and bone fragility induced by ADT. The objective of this study is to correlate FSH serum levels with body composition parameters, bone mineral density (BMD), and bone turnover markers at baseline conditions and after 12 months of ADT.

Methods

Twenty-nine consecutive non-metastatic prostate cancer (PC) patients were enrolled from 2017 to 2019 in a phase IV study. All patients underwent administration of the luteinizing hormone-releasing hormone antagonist degarelix. FBM, LBM, and BMD were evaluated by dual-energy x-ray absorptiometry at baseline and after 12 months of ADT. FSH, alkaline phosphatase, and C-terminal telopeptide of type I collagen were assessed at baseline and after 6 and 12 months. For outcome measurements and statistical analysis, t-test or sign test and Pearson or Spearman tests for continuous variables were used when indicated.

Results

At baseline conditions, a weak, non-significant, direct relationship was found between FSH serum levels and FBM at arms (r = 0.36) and legs (r = 0.33). Conversely, a stronger correlation was observed between FSH and total FBM (r = 0.52, p = 0.006), fat mass at arms (r = 0.54, p = 0.004), and fat mass at trunk (r = 0.45, p = 0.018) assessed after 12 months. On the other hand, an inverse relationship between serum FSH and appendicular lean mass index/FBM ratio was observed (r = -0.64, p = 0.001). This is an ancillary study of a prospective trial and this is the main limitation.

Conclusions

FSH serum levels after ADT could have an impact on body composition, in particular on FBM. Therefore, FSH could be a promising marker to monitor the risk of sarcopenic obesity and to guide the clinicians in the tailored evaluation of body composition in PC patients undergoing ADT.

Funding

This research was partially funded by Ferring Pharmaceuticals. The funder had no role in design and conduct of the study, collection, management, analysis, and interpretation of the data and in preparation, review, or approval of the manuscript.

Clinical trial number

clinicalTrials.gov NCT03202381, EudraCT Number 2016-004210-10.

Potential Diagnostic Role of Hepcidin in Anemic Patients Affected by Inflammatory Bowel Disease: A Systematic Review

BACKGROUND

Anemia is the main extraintestinal comorbidity of Inflammatory Bowel Disease (IBD). Differentiating the type of anemia in these disorders is still a challenge. Hepcidin could be a promising biomarker to identify iron deficiency anemia (IDA), anemia of chronic disease (ACD) and the concomitant presence of both IDA and ACD.

METHODS

To evaluate the potential role of hepcidin dosage in the management of anemia in IBD patients, we performed a systematic review by a comprehensive literature analysis of original papers reporting the dosage of hepcidin in IBD patients. In all the articles reviewed, the dosage of ferritin was reported, and the correlation between hepcidin and ferritin has been used to compare these two biomarkers.

RESULTS

A total of 12 articles concerning the dosage of hepcidin in IBD were included, comprising in total of 976 patients. The results of the hepcidin values in IBD patients when compared with controls were conflicting. In fact, four articles described an increase in this biomarker, three showed a decrease and five did not find significant differences. The correlation with ferritin was positive and significant. In three studies, some differences between hepcidin dosages and ferritin levels indicate a possible role when IDA and ACD could be present at the same time.

CONCLUSIONS

Considering the contradictory data of the studies, the diagnostic role of hepcidin as a biomarker remains elusive in IBD patients. These differences could be due to the clinical characteristics of the patients enrolled that should be better defined in the future. A suitable clinical trial should be designed to outline the possible role of hepcidin in differentiating IDA, ACD and concomitant IDA and ACD in IBD patients. At the moment, ferritin still remains the best marker to diagnose these conditions, in addition to hemoglobin, transferrin saturation and CRP as recommended by the ECCO guidelines.

The D647N mutation of FGFR1 induces ligand-independent receptor activation

The activation loop (A-loop) of kinases, a key regulatory region, is recurrently mutated in several kinase proteins in cancer resulting in dysregulated kinase activity and response to kinase inhibitors. FGFR1 receptor tyrosine kinase represents an important oncogene and therapeutic target for solid and hematological tumors. Here we investigate the biochemical and molecular effects of D647N mutation lying in the A-loop of FGFR1. When expressed in normal and tumoral in vitro cell models, FGFR1D647N is phosphorylated also in the absence of ligands, and this is accompanied by the activation of intracellular signaling. The expression of FGFR1D647N significantly increases single and collective migration of cancer cells in vitro and in vivo, when compared to FGFR1WT. FGFR1D647N expression exacerbates the aggressiveness of cancer cells, increasing their invasiveness in vitro and augmenting their pro-angiogenic capacity in vivo. Remarkably, the D647N mutation significantly increases the sensitivity of FGFR1 to the ATP-competitive inhibitor Erdafitinib suggesting the possibility that this mutation could become a specific target for the development of new inhibitors. Although further efforts are warranted for an exhaustive description of the activation mechanisms, for the identification of more specific inhibitors and for confirming the clinical significance of mutated FGFR1D647N, overall our data demonstrate that the D647N substitution of FGFR1 is a novel pro-oncogenic activating mutation of the receptor that, when found in cancer patients, may anticipate good response to erdafitinib treatment.

Frequency Evaluation of the Interleukin-6 -174G>C Polymorphism and Homeostatic Iron Regulator (HFE) Mutations as Disease Modifiers in Patients Affected by Systemic Lupus Erythematosus and Rheumatoid Arthritis

Autoimmune diseases are generally characterized by a multifactorial etiology and are often associated with a genetic predisposition. Both iron metabolism and the inflammatory cytokine system have been shown to play a pivotal role in the dysregulation of the immune response in many different autoimmune conditions, rheumatologic diseases included. The purpose of this work was to analyze the frequency of mutations altering the expression of IL-6 or influencing iron metabolism in patients affected by autoimmune diseases such as Rheumatoid Arthritis (RA) and Systemic Lupus Erythematosus (SLE). In this study, 144 patients were enrolled: 77 and 67 patients were affected by RA and SLE, respectively. In these cohorts, the frequency of the IL-6 polymorphism -174G>C located in the IL-6 gene promoter was tested. Moreover, the frequencies of the three HFE gene variations associated with iron overload were analyzed: p.His63Asp, p.Ser65Cys and p.Cys282Tyr. The two mutations p.His63Asp and p.Ser65Cys in the HFE gene did not reach statistical significance in any of the comparisons, regardless of the statistical model, cohorts of patients and control populations analyzed. The frequencies of the p.Cys282Tyr mutation and the IL-6 polymorphism -174G>C were found to be overall significantly decreased in RA and SLE patients when the Dominant model and Allele contrast were adopted with both the Odds Ratio and Chi-square. Although further investigation is needed, the examination of the frequencies of the -174G>C IL-6 promoter polymorphism and HFE mutations may add some valuable information on the interplay linking iron metabolism, inflammation and immunity in autoimmune diseases such as SLE and RA.

Effect of Degarelix Administration on Bone Health in Prostate Cancer Patients Without Bone Metastases. The Blade Study

CONTEXT

As patients are now living with prostate cancer for longer, the long-term impact of hormonal treatment on bone health is an increasingly debated subject.

OBJECTIVE

To characterize the changes in bone mineral density (BMD) and bone turnover markers after degarelix administration in prostate cancer patients without bone metastases. To explore the predictive role of body composition on treatment induced bone loss.

METHODS

BMD and body composition (lean body mass, fat body mass, and appendicular mass index [ALMI]) were assessed by dual X-ray absorptiometry on study entry and after 12 months of degarelix therapy. Alkaline phosphate (ALP) and C-terminal telopeptide of type I collagen (CTX) were assessed at baseline, and 6 and 12 months.

RESULTS

Twenty-nine patients entered the study. Degarelix administration was associated with a significant decrease in BMD after 12 months (2.4% reduction from baseline at lumbar spine). Serum CTX and ALP increased significantly (median increase from baseline 99% and 19.3%, respectively). An inverse correlation was observed between ALMI and CTX, but not ALP, at both baseline (Pearson r = -0.62, P < .0001) and month 12 (Pearson r = -0.41, P = .032). Moreover, a significant inverse correlation between changes in ALMI and CTX at 12 months (Pearson r = -0.43, P = .019) and a direct relationship between changes of ALMI and ALP (Pearson r = 0.44, P = .016) during degarelix therapy were observed.

CONCLUSION

Degarelix administration is associated with a significant decrease in BMD and increase in bone turnover markers. ALMI is a promising predictor of bone loss in prostate cancer patients receiving androgen deprivation therapy, and ALMI changes during therapy are associated with bone turnover derangement favoring bone quality alterations.

Characterization of three sialidases from Danio rerio

Zebrafish encodes several sialidases belonging to the NEU3 group, the plasma membrane-associated member of the family with high specificity toward ganglioside substrates. Neu3.1, Neu3.2 and Neu 3.3 have been expressed in E. coli and purified using the pGEX-2T expression system. Although all the enzymes are expressed by bacterial cells, Neu3.1 formed insoluble aggregates that hampered its purification. Neu3.2 and Neu3.3 formed oligomers as demonstrated by gel filtration chromatography experiments. Actually, the first formed a trimer whereas the second a pentamer. Intriguingly, despite relevant degree of sequence identity and similarity, the two enzymes showed peculiar substrate specificities toward gangliosides other than GM3, two glycoproteins and two forms of sialyllactose. Using molecular modelling and the crystal structure of the human cytosolic sialidase NEU2 as a template, the 3D models of the sialidases from zebrafish have been generated. As expected, the 3D models showed the typical six blade beta-propeller typical of sialidases, with an overall highly conserved active site architecture. The differences among the three zebrafish enzymes and human NEU2 are mainly located in the loops connecting the antiparallel beta strands of the propeller core. These portions of the proteins are probably responsible for the differences observed in substrate specificities, as well as in the different subcellular localization and aggregation features observed in solution. Finally, the in silico analysis of RNA-Seq data evidenced a peculiar expression profile of the three genes during embryogenesis, suggesting different roles of these sialidases during development.

β-Galactosylceramidase Promotes Melanoma Growth via Modulation of Ceramide Metabolism

Disturbance of sphingolipid metabolism may represent a novel therapeutic target in metastatic melanoma, the most lethal form of skin cancer. β-Galactosylceramidase (GALC) removes β-galactose from galactosylceramide and other sphingolipids. In this study, we show that downregulation of galcb, a zebrafish ortholog of human GALC, affects melanoblast and melanocyte differentiation in zebrafish embryos, suggesting a possible role for GALC in melanoma. On this basis, the impact of GALC expression in murine B16-F10 and human A2058 melanoma cells was investigated following its silencing or upregulation. Galc knockdown hampered growth, motility, and invasive capacity of B16-F10 cells and their tumorigenic and metastatic activity when grafted in syngeneic mice or zebrafish embryos. Galc-silenced cells displayed altered sphingolipid metabolism and increased intracellular levels of ceramide, paralleled by a nonredundant upregulation of Smpd3, which encodes for the ceramide-generating enzyme neutral sphingomyelinase 2. Accordingly, GALC downregulation caused SMPD3 upregulation, increased ceramide levels, and inhibited the tumorigenic activity of human melanoma A2058 cells, whereas GALC upregulation exerted opposite effects. In concordance with information from melanoma database mining, RNAscope analysis demonstrated a progressive increase of GALC expression from common nevi to stage IV human melanoma samples that was paralleled by increases in microphthalmia transcription factor and tyrosinase immunoreactivity inversely related to SMPD3 and ceramide levels. Overall, these findings indicate that GALC may play an oncogenic role in melanoma by modulating the levels of intracellular ceramide, thus providing novel opportunities for melanoma therapy. SIGNIFICANCE: Data from zebrafish embryos, murine and human cell melanoma lines, and patient-derived tumor specimens indicate that β-galactosylceramidase plays an oncogenic role in melanoma and may serve as a therapeutic target.

Lack of specific T- and B-cell clonal expansions in multiple sclerosis patients with progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a rare, potentially devastating myelin-degrading disease caused by the JC virus. PML occurs preferentially in patients with compromised immune system, but has been also observed in multiple sclerosis (MS) patients treated with disease-modifying drugs. We characterized T and B cells in 5 MS patients that developed PML, 4 during natalizumab therapy and one after alemtuzumab treatment, and in treated patients who did not develop the disease. Results revealed that: i) thymic and bone marrow output was impaired in 4 out 5 patients at the time of PML development; ii) T-cell repertoire was restricted; iii) clonally expanded T cells were present in all patients. However, common usage or pairings of T-cell receptor beta variable or joining genes, specific clonotypes or obvious “public” T-cell response were not detected at the moment of PML onset. Similarly, common restrictions were not found in the immunoglobulin heavy chain repertoire. The data indicate that no JCV-related specific T- and B-cell expansions were mounted at the time of PML. The current results enhance our understanding of JC virus infection and PML, and should be taken into account when choosing targeted therapies.

Mebendazole as a Candidate for Drug Repurposing in Oncology: An Extensive Review of Current Literature

Anticancer treatment efficacy is limited by the development of refractory tumor cells characterized by increased expression and activity of mechanisms promoting survival, proliferation, and metastatic spread. The present review summarizes the current literature regarding the use of the anthelmintic mebendazole (MBZ) as a repurposed drug in oncology with a focus on cells resistant to approved therapies, including so called “cancer stem cells”. Mebendazole meets many of the characteristics desirable for a repurposed drug: good and proven toxicity profile, pharmacokinetics allowing to reach therapeutic concentrations at disease site, ease of administration and low price. Several in vitro studies suggest that MBZ inhibits a wide range of factors involved in tumor progression such as tubulin polymerization, angiogenesis, pro-survival pathways, matrix metalloproteinases, and multi-drug resistance protein transporters. Mebendazole not only exhibits direct cytotoxic activity, but also synergizes with ionizing radiations and different chemotherapeutic agents and stimulates antitumoral immune response. In vivo, MBZ treatment as a single agent or in combination with chemotherapy led to the reduction or complete arrest of tumor growth, marked decrease of metastatic spread, and improvement of survival. Further investigations are warranted to confirm the clinical anti-neoplastic activity of MBZ and its safety in combination with other drugs in a clinical setting.

Lessons learnt from a pilot study on residual dye removal by an aerated treatment wetland

Treatment wetlands (TWs) have shown good capacity in dye removal from textile wastewater. However, the high hydraulic retention times (HRTs) required by these solutions and the connected high area requirements, remain a big drawback towards the application of TWs for dye treatment at full scale. Aerated TWs are interesting intensified solutions that attempt to reduce the TW required area. Therefore, an aerated CW pilot plant, composed of a 20 m² horizontal subsurface flow TW (HF) and a 21 m² Free Water System (FWS), equipped with aeration pipelines, was built and monitored to investigate the potential reduction of required area for dye removal from the effluent wastewater of a centralized wastewater treatment plant (WWTP). During a 8 months long study, experimenting with different hydraulic retention times (HRTs - 1.2, 2.6 and 3.5 days) and aeration modes (intermittent and continuous), the pilot plant has shown a normal biological degradation for organic matter and nutrients, while the residual dye removal has been very low, as demonstrated by the absorbance measure at three wavelengths: at 426 nm (blue) the removal varies from -55% at influent absorbance of 0.010 to 41% at 0.060; at 558 nm (yellow) the removal is negative at 0.005 (-58%) and high at higher influent concentrations (72% at 0.035 of absorbance for the inlet); at 660 nm (red) -82% of removal efficiency was obtained at influent absorbance of 0.002 and 74% at 0.010. These results are a consequence of the biological oxidation processes taking place in the WWTP, so that the residual dye seems to be resistant to further aerobic degradation. Therefore, TWs enhanced by aeration can provide only a buffer effect on peak dye concentrations.

A novel homozygous mutation in GAD1 gene described in a schizophrenic patient impairs activity and dimerization of GAD67 enzyme

Recently, by whole exome sequencing of schizophrenia (SCZ) patients, we identified a subject that was homozygous for a novel missense substitution (c.391 A > G) in the glutamate acid decarboxylase 1 (GAD1) gene. GAD1 encodes for GAD67 enzyme, catalyzing the production of gamma-aminobutyric acid (GABA) from L-glutamic acid. Here, we studied the impact of this mutation on GAD67 activity, dimerization and subcellular localization. Biochemical assay revealed that c.391 A > G reduces GAD67 enzymatic activity by ~30%, probably due to the impaired homodimerization of homozygous mutants as highlighted by proximity ligation assays. The mutational screening of 120 genes of the "GABAergic system" in a cohort of 4,225 SCZ cases and 5,834 controls (dbGaP: phs000473.v1.p2), did not identify other cases that were homozygous for ultra-rare variants in GAD1, but highlighted an increased frequency of cases that were homozygous for rare variants in genes of the GABA system (SCZ: 0.14% vs. Controls: 0.00%; p-value = 0.0055). In conclusion, this study demonstrates the functional impact of c.391 A > G variant and its biological effect makes it a good candidate as risk variant for SCZ. This study also supports an involvement of ultra-rare variants in GABAergic genes in the etiopathogenesis of SCZ.

Exploring the Role of Enzalutamide in Combination with Radiation Therapy: An In Vitro Study

BACKGROUND/AIM

Androgen receptor plays a key role in prostate cancer development and is a causative agent of its radio-resistance. The present study investigated the potential radio-sensitizing effect of enzalutamide, a second-generation anti-androgen, in human prostate cancer cells.

MATERIALS AND METHODS

The radio-sensitizing effect of enzalutamide was assessed in the androgen-dependent LNCaP cells and the androgen-independent PC3 cells by clonogenic assay and γ-H2AX assay.

RESULTS

Enzalutamide-treated LNCaP cells showed a significant decrease of cell survival at all radiation doses tested. An increased number of γ-H2AX-positive nuclei was observed, suggesting a possible impairment of the DNA repair machinery. Conversely, enzalutamide did not exhibit a significant radio-sensitizing effect on PC3 cells.

CONCLUSION

The combination of enzalutamide with ionizing radiation significantly improves radio-sensitivity of hormone-dependent LNCaP cells. Translated in the clinical practice, our results may help to find additional strategies to improve effectiveness of radiotherapy.

Oligometastatic prostate cancer patients stratification: A molecular signature identified by liquid biopsy

TPS400

Background: Oligometastatic prostate cancer (OPC) may represent the initial step of an unavoidable, rapid progression to a polymetastatic state, or the expression of a real oligometastatic phenotype related to a condition of stable disease for a long time. In the last scenario, stereotactic body radiation therapy (SBRT) can be considered as a potentially curative treatment option for hormone-naïve OPC. We propose a prospective, explorative trail with the aim of identifying by liquid biopsy a molecular signature (genes or differential expression of miRNA), and related clonal evolution, underlying metastatic prostate cancer progression after a course of SBRT. Methods: Study population will be 30 adult, hormone-naïve OPC undergoing SBRT. Table 1 summarizes gene and miRNA panel for molecular analysis. For each patient, 15 ml of peripheral blood will be collected before and at the end of SBRT, every 3 months for the first year, then every 6 months until disease progression, when another blood sample will be collected in case of instrumental evidence of failure (using PET-Choline or CT-scan plus bone scintigraphy). 7.5 ml of peripheral blood will be centrifuged to separate sera and 7.5 ml of peripheral blood will be centrifuged to separate plasma from the other blood components, respectively. Sera and plasma will be stored at -20°C and centralized to CREA Laboratory at our Institution, then immediately processed for cell free DNA (cfDNA) and miRNA extraction for NGS of target genes (by Illumina platforms MiSeq and MiniSeq) and dPCR analysis. Study duration will be 36 months. This protocol has been written and will be conducted in agreement with either the Declaration of Helsinki and subsequent amendments and ICH Harmonized Tripartite Guideline for Good Clinical Practice, and has received approval of local Ethics Committee. Panel for analysis. [Table: see text]

Exosomes Secreted by HeLa Cells Shuttle on Their Surface the Plasma Membrane-Associated Sialidase NEU3

Sialidases are glycohydrolases that remove terminal sialic acid residues from oligosaccharides, glycolipids, and glycoproteins. The plasma membrane-associated sialidase NEU3 is involved in the fine-tuning of sialic acid-containing glycans directly on the cell surface and plays relevant roles in important biological phenomena such as cell differentiation, molecular recognition, and cancer transformation. Extracellular vesicles are membranous structures with a diameter of 0.03-1 μm released by cells and can be detected in blood, urine, and culture media. Among extracellular vesicles, exosomes play roles in intercellular communication and maintenance of several physiological and pathological conditions, including cancer, and could represent a useful diagnostic tool for personalized nanomedicine approaches. Using inducible expression of the murine form of NEU3 in HeLa cells, a study of the association of the enzyme with exosomes released in the culture media has been performed. Briefly, NEU3 is associated with highly purified exosomes and localizes on the external leaflet of these nanovesicles, as demonstrated by enzyme activity measurements, Western blot analysis, and dot blot analysis using specific protein markers. On the basis of these results, it is plausible that NEU3 activity on exosome glycans enhances the dynamic biological behavior of these small extracellular vesicles by modifying the negative charge and steric hindrance of their glycocalyx. The presence of NEU3 on the exosomal surface could represent a useful marker for the detection of these nanovesicles and a tool for improving our understanding of the biology of these important extracellular carriers in physiological and pathological conditions.

Upflow anaerobic sludge blanket and aerated constructed wetlands for swine wastewater treatment: a pilot study

Swine wastewater management is often affected by two main issues: a too high volume for optimal reuse as a fertilizer and a too high strength for an economically sustainable treatment by classical solutions. Hence, an innovative scheme has been tested to treat swine wastewater, combining a low cost anaerobic reactor, upflow anaerobic sludge blanket (UASB), with intensified constructed wetlands (aerated CWs) in a pilot scale experimental study. The swine wastewater described in this paper is produced by a swine production facility situated in North Italy. The scheme of the pilot plant consisted of: (i) canvas-based thickener; (ii) UASB; (iii) two intensified aerated vertical subsurface flow CWs in series; (iv) a horizontal flow subsurface CW. The influent wastewater quality has been defined for total suspended solids (TSS 25,025 ± 9,323 mg/l), organic carbon (chemical oxygen demand (COD) 29,350 ± 16,983 mg/l), total reduced nitrogen and ammonium (total Kjeldahl nitrogen (TKN) 1,783 ± 498 mg/l and N-NH₄⁺ 735 ± 251 mg/l) and total phosphorus (1,285 ± 270 mg/l), with nitrates almost absent. The overall system has shown excellent performances in terms of TSS, COD, N-NH₄⁺ and TKN removal efficiencies (99.9%, 99.6%, 99.5%, and 99.0%, respectively). Denitrification (N-NO₃^- effluent concentration equal to 614 ± 268 mg/l) did not meet the Italian quality standards for discharging in water bodies, mainly because the organic carbon was almost completely removed in the intensified CW beds.

Large scale application of French reed beds: municipal wastewater treatment for a 20,000 inhabitant's town in Moldova

A two-stage vertical flow treatment wetlands system (French reed beds) was realized in 2012-2013 for the Orhei's town in Moldova. The treatment system occupies a total area of about 5 ha and operates in cold climate conditions during winter, with air temperatures below -20 °C. The first 2 years (2013-2015) of treatment performances for this system are presented here, with a particular highlight on the analysis of the commissioning phase and the operative choices taken along this period basing on the observed results. The specific classification of this application of constructed wetlands (CWs) for the primary and secondary treatment of municipal wastewater as a medium-large size system makes this technical report a relevant reference for demonstrating the possible extension to the highest numbers of inhabitants for the common application range of this family of technologies (CWs) for municipal wastewater. The observed performances for organic carbon (both as chemical oxygen demand (COD) and biochemical oxygen demand (BOD₅)), suspended solids and ammonia removals in the whole first operational period consistently satisfied the national limits for discharge in rivers, respectively, with average values of 86%, 96% and 66%. The treated daily flow was measured in the range of 1,000-2,000 m³/d.

Pro-lymphangiogenic properties of IFN-γ-activated human dendritic cells

Dendritic cells (DCs) play a crucial role in the initiation of adaptive immune responses. In addition, through the release of pro- and anti-angiogenic mediators, DCs are key regulators of blood vessel remodeling, a process that characterizes inflammation. Less information is available on the role of DCs in lymphangiogenesis. This study reports that human DCs produce VEGF-C, a cytokine with potent pro-lymphangiogenic activity when stimulated with IFN-γ. DC-derived VEGF-C was biologically active, being able to promote tube-like structure formation in cultures of human lymphatic endothelial cells (LECs). DCs co-cultured with IL-15-activated NK cells produced high levels of VEGF-C, suggesting a role for NK-DC cross-talk in peripheral lymphoid and non-lymphoid tissues in inflammation-associated lymphangiogenesis. Induction of VEGF-C by IFN-γ was detected also in other myeloid cells, such as blood-purified CD1c(+) DCs, CD14(+) monocytes and in monocyte-derived macrophages. In all these cell types, VEGF-C was found associated with the cell membrane by low affinity, heparan sulphate-mediated, interactions. Therefore, human DCs should be considered as new players in inflammation-associated lymphangiogenesis.

In silico identification of new putative pathogenic variants in the NEU1 sialidase gene affecting enzyme function and subcellular localization

The NEU1 gene is the first identified member of the human sialidases, glycohydrolitic enzymes that remove the terminal sialic acid from oligosaccharide chains. Mutations in NEU1 gene are causative of sialidosis (MIM 256550), a severe lysosomal storage disorder showing autosomal recessive mode of inheritance. Sialidosis has been classified into two subtypes: sialidosis type I, a normomorphic, late-onset form, and sialidosis type II, a more severe neonatal or early-onset form. A total of 50 causative mutations are reported in HGMD database, most of which are missense variants. To further characterize the NEU1 gene and identify new functionally relevant protein isoforms, we decided to study its genetic variability in the human population using the data generated by two large sequencing projects: the 1000 Genomes Project (1000G) and the NHLBI GO Exome Sequencing Project (ESP). Together these two datasets comprise a cohort of 7595 sequenced individuals, making it possible to identify rare variants and dissect population specific ones. By integrating this approach with biochemical and cellular studies, we were able to identify new rare missense and frameshift alleles in NEU1 gene. Among the 9 candidate variants tested, only two resulted in significantly lower levels of sialidase activity (p<0.05), namely c.650T>C and c.700G>A. These two mutations give rise to the amino acid substitutions p.V217A and p.D234N, respectively. NEU1 variants including either of these two amino acid changes have 44% and 25% residual sialidase activity when compared to the wild-type enzyme, reduced protein levels and altered subcellular localization. Thus they may represent new, putative pathological mutations resulting in sialidosis type I. The in silico approach used in this study has enabled the identification of previously unknown NEU1 functional alleles that are widespread in the population and could be tested in future functional studies.

Sialidase NEU3 dynamically associates to different membrane domains specifically modifying their ganglioside pattern and triggering Akt phosphorylation

Lipid rafts are known to regulate several membrane functions such as signaling, trafficking and cellular adhesion. The local enrichment in sphingolipids and cholesterol together with the low protein content allows their separation by density gradient flotation after extraction with non-ionic detergent at low temperature. These structures are also referred to as detergent resistant membranes (DRM). Among sphingolipids, gangliosides play important roles in different biological events, including signal transduction and tumorigenesis. Sialidase NEU3 shows high enzymatic specificity toward gangliosides. Moreover, the enzyme is present both at the cell surface and in endosomal structures and cofractionates with caveolin. Although changes in the expression level of NEU3 have been correlated to different tumors, little is known about the precise distribution of the protein and its ability in modifying the ganglioside composition of DRM and non-DRM, thus regulating intracellular events. By means of inducible expression cell system we found that i) newly synthesized NEU3 is initially associated to non-DRM; ii) at steady state the protein is equally distributed between the two membrane subcompartments, i.e., DRM and non-DRM; iii) NEU3 is degraded via the proteasomal pathway; iv) the enzyme specifically modifies the ganglioside composition of the membrane areas where it resides; and v) NEU3 triggers phosphorylation of Akt, even in absence of exogenously administered EGF. Taken together our data demonstrate that NEU3 regulates the DRM ganglioside content and it can be considered as a modulator of Akt phosphorylation, further supporting the role of this enzyme in cancer and tumorigenesis.

Analysis of three μ1-AP1 subunits during zebrafish development

BACKGROUND

The family of AP-1 complexes mediates protein sorting in the late secretory pathway and it is essential for the development of mammals. The ubiquitously expressed AP-1A complex consists of four adaptins γ1, β1, μ1A, and σ1A. AP-1A mediates protein transport between the trans-Golgi network and early endosomes. The polarized epithelia AP-1B complex contains the μ1B-adaptin. AP-1B mediates specific transport of proteins from basolateral recycling endosomes to the basolateral plasma membrane of polarized epithelial cells.

RESULTS

Analysis of the zebrafish genome revealed the existence of three μ1-adaptin genes, encoding μ1A, μ1B, and the novel isoform μ1C, which is not found in mammals. μ1C shows 80% sequence identity with μ1A and μ1B. The μ1C expression pattern largely overlaps with that of μ1A, while μ1B is expressed in epithelial cells. By knocking-down the synthesis of μ1A, μ1B and μ1C with antisense morpholino techniques we demonstrate that each of these μ1 adaptins is essential for zebrafish development, with μ1A and μ1C being involved in central nervous system development and μ1B in kidney, gut and liver formation.

CONCLUSIONS

Zebrafish is unique in expressing three AP-1 complexes: AP-1A, AP-1B, and AP-1C. Our results demonstrate that they are not redundant and that each of them has specific functions, which cannot be fulfilled by one of the other isoforms. Each of the μ1 adaptins appears to mediate specific molecular mechanisms essential for early developmental processes, which depends on specific intracellular vesicular protein sorting pathways.

Characterization and expression analysis of mcoln1.1 and mcoln1.2, the putative zebrafish co-orthologs of the gene responsible for human mucolipidosis type IV

Mucolipidosis type IV (MLIV) is an autosomal recessive lysosomal storage disorder caused by mutations in the MCOLN1 gene coding for mucolipin-1 (TRPML1). TRPML1 belongs to a transient receptor potential channels (TRP) subfamily, which in mammals includes two other members: mucolipin-2 (TRPML2) and mucolipin-3 (TRPML3). Bioinformatic analysis of the Danio rerio (zebrafish) genome and trascriptome revealed the presence of five different genes related to human mucolipins: mcoln1.1, mcoln1.2, mcoln2, mcoln3.1 and mcoln3.2. We focused our efforts on the characterization of the two putative zebrafish MCOLN1 co-orthologs. Transient-expression experiments in human HeLa cells demonstrated that fish Mcoln1.1 and Mcoln1.2, similarly to TRPML1, localize to late endosomal/lysosomal compartments. Real-Time PCR (RT-PCR) experiments showed that both genes are maternally expressed and transcribed at different levels during embryogenesis. RT-PCR analysis in different zebrafish tissues displayed ubiquitary expression for mcoln1.1 and a more tissue-specific pattern for mcoln1.2. Spatial and temporal expression studies using whole-mount in situ hybridization confirmed that both genes are maternally expressed and ubiquitously transcribed during gastrulation and early somitogenesis. Notably, in the next developmental stages they are more expressed in neural regions and in retina layers, tissues affected in MLIV. Interestingly, mcoln1.1 is detected, from 10 somite-stage until to 36 hpf, in the yolk syncytial layer (YSL) and in the intermediate cell mass (ICM), the earliest site of hematopoiesis. Overall, the redundancy of mucolipins together with their expression profile support the biological relevance of this class of proteins in zebrafish. The data herein presented indicate that Danio rerio could be a suitable vertebrate model for the study of some aspects of MLIV pathogenesis.

New insights on the sialidase protein family revealed by a phylogenetic analysis in metazoa

Sialidases are glycohydrolytic enzymes present from virus to mammals that remove sialic acid from oligosaccharide chains. Four different sialidase forms are known in vertebrates: the lysosomal NEU1, the cytosolic NEU2 and the membrane-associated NEU3 and NEU4. These enzymes modulate the cell sialic acid content and are involved in several cellular processes and pathological conditions. Molecular defects in NEU1 are responsible for sialidosis, an inherited disease characterized by lysosomal storage disorder and neurodegeneration. The studies on the biology of sialic acids and sialyltransferases, the anabolic counterparts of sialidases, have revealed a complex picture with more than 50 sialic acid variants selectively present in the different branches of the tree of life. The gain/loss of specific sialoconjugates have been proposed as key events in the evolution of deuterostomes and Homo sapiens, as well as in the host-pathogen interactions. To date, less attention has been paid to the evolution of sialidases. Thus we have conducted a survey on the state of the sialidase family in metazoan. Using an in silico approach, we identified and characterized sialidase orthologs from 21 different organisms distributed among the evolutionary tree: Metazoa relative (Monosiga brevicollis), early Deuterostomia, precursor of Chordata and Vertebrata (teleost fishes, amphibians, reptiles, avians and early and recent mammals). We were able to reconstruct the evolution of the sialidase protein family from the ancestral sialidase NEU1 and identify a new form of the enzyme, NEU5, representing an intermediate step in the evolution leading to the modern NEU3, NEU4 and NEU2. Our study provides new insights on the mechanisms that shaped the substrate specificity and other peculiar properties of the modern mammalian sialidases. Moreover, we further confirm findings on the catalytic residues and identified enzyme loop portions that behave as rapidly diverging regions and may be involved in the evolution of specific properties of sialidases.

Gallus gallus NEU3 sialidase as model to study protein evolution mechanism based on rapid evolving loops

BACKGROUND

Large surface loops contained within compact protein structures and not involved in catalytic process have been proposed as preferred regions for protein family evolution. These loops are subjected to lower sequence constraints and can evolve rapidly in novel structural variants. A good model to study this hypothesis is represented by sialidase enzymes. Indeed, the structure of sialidases is a β-propeller composed by anti-parallel β-sheets connected by loops that suit well with the rapid evolving loop hypothesis. These features prompted us to extend our studies on this protein family in birds, to get insights on the evolution of this class of glycohydrolases.

RESULTS

Gallus gallus (Gg) genome contains one NEU3 gene encoding a protein with a unique 188 amino acid sequence mainly constituted by a peptide motif repeated six times in tandem with no homology with any other known protein sequence. The repeat region is located at the same position as the roughly 80 amino acid loop characteristic of mammalian NEU4. Based on molecular modeling, all these sequences represent a connecting loop between the first two highly conserved β-strands of the fifth blade of the sialidase β-propeller. Moreover this loop is highly variable in sequence and size in NEU3 sialidases from other vertebrates. Finally, we found that the general enzymatic properties and subcellular localization of Gg NEU3 are not influenced by the deletion of the repeat sequence.

CONCLUSION

In this study we demonstrated that sialidase protein structure contains a surface loop, highly variable both in sequence and size, connecting two conserved β-sheets and emerging on the opposite site of the catalytic crevice. These data confirm that sialidase family can serve as suitable model for the study of the evolutionary process based on rapid evolving loops, which may had occurred in sialidases. Giving the peculiar organization of the loop region identified in Gg NEU3, this protein can be considered of particular interest in such evolutionary studies and to get deeper insights in sialidase evolution.

Beneficial effects of melatonin on nicotine-induced vasculopathy

Tobacco smoking is responsible for death of many people each year and increases the risk of developing numerous disorders, particularly cardiovascular disease and cancer. Among the components of cigarette smoke, nicotine is known to excert proatherosclerotic, prothrombotic and proangiogenic effects on vascular endothelial cells. The current study was designed to investigate the mechanisms by which nicotine induces endothelial dysfunction and further to examine whether melatonin protects against nicotine-induced vasculopathy. Four groups of male rats (controls, melatonin-treated, nicotine treated [100 microg/mL in drinking water], and nicotine plus melatonin [5 mg/kg/day] treated) were used in this study. After 28 days all the animals were killed by decapitation and the aorta was removed. We evaluated the hydroxyproline content, and the different expression of proteins involved in several types of stress (ERK1/2), in fibrosis (TGF-beta1, NF-kappaB) and in recruitment of circulating leukocytes onto the vessel wall, including intercellular adhesion molecule-1 (ICAM-1) and vascular cellular adhesion molecule-1 (VCAM-1). These metabolic pathways are important in the development of nicotine-induced atherosclerosis and hypertension. Our results show that nicotine induces marked structural and functional alterations in the aorta. Nicotine receptor binding results in activation and phosphorylation of ERK 1/2. This enzyme, in turn, activates both TGF-beta1 and NF-kappaB; they stimulate respectively the synthesis of type I collagen, responsible of fibrosis, and moreover ICAM-1, VCAM-1 and reactive oxygen species. Based on these findings, melatonin is able to minimize the negative effects of nicotine by blocking the activation of ERK and the other signalling pathways in which this enzyme is involved.

Molecular cloning and biochemical characterization of sialidases from zebrafish (Danio rerio)

Sialidases remove sialic acid residues from various sialo-derivatives. To gain further insights into the biological roles of sialidases in vertebrates, we exploited zebrafish (Danio rerio) as an animal model. A zebrafish transcriptome- and genome-wide search using the sequences of the human NEU polypeptides as templates revealed the presence of seven different genes related to human sialidases. neu1 and neu4 are the putative orthologues of the mammalian sialidases NEU1 and NEU4 respectively. Interestingly, the remaining genes are organized in clusters located on chromosome 21 and are all more closely related to mammalian sialidase NEU3. They were thus named neu3.1, neu3.2, neu3.3, neu3.4 and neu3.5. Using RT-PCR (reverse transcription-PCR) we detected transcripts for all genes, apart from neu3.4, and whole-mount in situ hybridization experiments show a localized expression pattern in gut and lens for neu3.1 and neu4 respectively. Transfection experiments in COS7 (monkey kidney) cells demonstrate that Neu3.1, Neu3.2, Neu3.3 and Neu4 zebrafish proteins are sialidase enzymes. Neu3.1, Neu3.3 and Neu4 are membrane-associated and show a very acidic pH optimum below 3.0, whereas Neu3.2 is a soluble sialidase with a pH optimum of 5.6. These results were further confirmed by subcellular localization studies carried out using immunofluorescence. Moreover, expression in COS7 cells of these novel zebrafish sialidases (with the exception of Neu3.2) induces a significant modification of the ganglioside pattern, consistent with the results obtained with membrane-associated mammalian sialidases. Overall, the redundancy of sialidases together with their expression profile and their activity exerted on gangliosides of living cells indicate the biological relevance of this class of enzymes in zebrafish.

Sialidase NEU3 is a peripheral membrane protein localized on the cell surface and in endosomal structures

Sialidase NEU3 is also known as the plasma-membrane-associated form of mammalian sialidases, exhibiting a high substrate specificity towards gangliosides. In this respect, sialidase NEU3 modulates cell-surface biological events and plays a pivotal role in different cellular processes, including cell adhesion, recognition and differentiation. At the moment, no detailed studies concerning the subcellular localization of NEU3 are available, and the mechanism of its association with cellular membranes is still unknown. In the present study, we have demonstrated that sialidase NEU3, besides its localization at the plasma membrane, is present in intracellular structures at least partially represented by a subset of the endosomal compartment. Moreover, we have shown that NEU3 present at the plasma membrane is internalized and locates then to the recycling endosomal compartment. The enzyme is associated with the outer leaflet of the plasma membrane, as shown by selective cell-surface protein biotinylation. This evidence is in agreement with the ability of NEU3 to degrade gangliosides inserted into the plasma membrane of adjacent cells. Moreover, the mechanism of the protein association with the lipid bilayer was elucidated by carbonate extraction. Under these experimental conditions, we have succeeded in solubilizing NEU3, thus demonstrating that the enzyme is a peripheral membrane protein. In addition, Triton X-114 phase separation demonstrates further the hydrophilic nature of the protein. Overall, these results provide important information about the biology of NEU3, the most studied member of the mammalian sialidase family.

Expression of sialidase Neu2 in leukemic K562 cells induces apoptosis by impairing Bcr-Abl/Src kinases signaling

Chronic myeloid leukemia is a hematopoietic stem cell cancer, originated by the perpetually "switched on" activity of the tyrosine kinase Bcr-Abl, leading to uncontrolled proliferation and insensitivity to apoptotic stimuli. The genetic phenotype of myeloid leukemic K562 cells includes the suppression of cytosolic sialidase Neu2. Neu2 transfection in K562 cells induced a marked decrease (-30% and -80%) of the mRNA of the anti-apoptotic factors Bcl-XL and Bcl-2, respectively, and an almost total disappearance of Bcl-2 protein. In addition, gene expression and activity of Bcr-Abl underwent a 35% diminution, together with a marked decrease of Bcr-Abl-dependent Src and Lyn kinase activity. Thus, the antiapoptotic axis Bcr-Abl, Src, and Lyn, which stimulates the formation of Bcl-XL and Bcl-2, was remarkably weakened. The ultimate consequences of these modifications were an increased susceptibility to apoptosis of K562 cells and a marked reduction of their proliferation rate. The molecular link between Neu2 activity and Bcr-Abl signaling pathway may rely on the desialylation of some cytosolic glycoproteins. In fact, three cytosolic glycoproteins, in the range 45-66 kDa, showed a 50-70% decrease of their sialic acid content upon Neu2 expression, supporting their possible role as modulators of the Bcr-Abl complex.

Tolerance to hydraulic and organic load fluctuations in constructed wetlands

This paper describes a two-year performance evaluation of four different constructed wetland (CW) treatment systems designed by IRIDRA Srl, located in central Italy. All four CW systems were established to treat wastewater effluent from different tourist activities: (1) one single-stage CW for secondary treatment of domestic wastewater (30 p.e.) at a holiday farm site; (2) a hybrid compact system consisting of two stages, a horizontal flow (HF) system followed by a vertical flow (VF) system for the secondary treatment of effluent from a 140 p.e. tourist resort; (3) a single-stage vertical flow (VF) CW for a 100 p.e. mountain shelter; and (4) a pair of single-stage, HF CWs for the secondary treatment of segregated grey and black water produced by an 80 p.e. camping site. These tourism facilities are located in remote areas and share some common characteristics concerning their water management: they have high variability of water consumption and wastewater flow, depending on the season, weather and weekly regularities; they have no connection to a public sewer and most sites are located in a sensitive environment. Total suspended solids (TSS), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), ammonium (N-NH4+), nitrate (N-NOx), total nitrogen (Ntot), total phosphorus (Ptot), total coliform (TC), faecal coliform (FC), E. coli removal efficiencies for all four CW systems are presented. The results from this study demonstrate the potential of CWs as a suitable technology for treating wastewater from tourism facilities in remote areas. A very efficient COD reduction (83-95%) and pathogen elimination (3-5 logs) have been achieved. Furthermore, the CWs are easily maintained, robust (not sensitive to peak flows), constructed with local materials, and operate with relatively low cost.

Plasma membrane production of ceramide from ganglioside GM3 in human fibroblasts

Ceramide is a key lipid molecule necessary to regulate some cellular processes, including apoptosis and cell differentiation. In this context, its production has been shown to occur via sphingomyelin hydrolysis or sphingosine acylation. Here, we show that in human fibroblasts, plasma membrane ceramide is also produced from ganglioside GM3 by detachment of sugar units. Membrane-bound glycosylhydrolases have a role in this process. In fact, the production of ceramide from GM3 has been observed even under experimental conditions able to block endocytosis or lysosomal activity, and the overexpression of the plasma membrane ganglioside sialidase Neu3 corresponded to a higher production of ceramide in the plasma membrane. The increased activity of Neu3 was paralleled by an increase of GM3 synthase mRNA and GM3 synthase activity. Neu3-overexpressing fibroblasts were characterized by a reduced proliferation rate and higher basal number of apoptotic cells in comparison with wild-type cells. A similar behavior was observed when normal fibroblasts were treated with exogenous C2-ceramide.

Glutamatergic reinnervation through peripheral nerve graft dictates assembly of glutamatergic synapses at rat skeletal muscle

Acetylcholine is the main neurotransmitter at the mammalian neuromuscular junction (NMJ) where nicotinic acetylcholine receptors mediate the signaling between nerve terminals and muscle fibers. We show that under glutamatergic transmission, rat NMJ switches from cholinergic type synapse to glutamatergic synapse. Connecting skeletal muscle to the lateral white matter of the spinal cord by grafting the distal stump of the transected motor nerve produced functional muscle reinnervation. The restored neuromuscular activity became resistant to common curare blockers but sensitive to the glutamate alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist. Analysis of the regenerated nerve disclosed new glutamatergic axons and the disappearance of cholinergic fibers. Many axons belonged to the supraspinal neurons located in the red nucleus and the brainstem nuclei. Finally, the innervated muscle displayed high expression and clustering of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunits glutamate receptors 1 and 2. Our data suggest that supraspinal neurons can target skeletal muscle, which retains the plasticity to generate functional glutamatergic NMJ.

Cellular expression and alternative splicing of SLC25A23, a member of the mitochondrial Ca2+-dependent solute carrier gene family

The transport of metabolites across the inner mitochondrial membrane is mediated by a large superfamily of mitochondrial solute carrier (MSC) proteins. A novel human member of the MSC gene family named SLC25A23, with homologs in mammalian and non-mammalian species has been recently identified together with two close paralogs, SLC25A24 and SLC25A25. These genes encode the human isoforms of the ATP-Mg/Pi carrier described in whole mitochondria. We report here the cellular expression and alternative splicing of SLC25A23. The gene encodes a 468 amino acids polypeptide, named SCaMC-3, with a bipartite structure typical of calcium-binding mitochondrial solute carrier (CaMSC) proteins. The amino-terminal portion harbors three canonical EF-hand calcium-binding domains while the carboxyl-terminal portion of SCaMC-3 has the characteristic features of the MSC superfamily. Northern blot analysis reveals the presence of the transcript in brain, heart, skeletal muscle, liver and small intestine. The SLC25A23 gene undergoes alternative splicing suggesting a modular nature of the encoded product. Three out of four putative protein isoforms lack a significant portion of the third mitochondrial carrier signature. The most common SCaMC-3 isoform shows a mitochondrial subcellular localization when transfected in HeLa cells and is able to bind calcium by Ca(2+)-dependent mobility shift assays. We believe that our study will contribute to a better knowledge of this family of mitochondrial carriers.

Overexpression of wild-type and mutant mucolipin proteins in mammalian cells: effects on the late endocytic compartment organization

Mucolipin-1 is a 65-kDa membrane protein encoded by the MCOLN1 gene, which is mutated in patients with mucolipidosis type IV (MLIV), a rare neurodegenerative lysosomal storage disorder. We studied the subcellular localization of wild-type and three different mutant forms (T232P, F408del and F465L) of mucolipin by expressing Myc-tagged proteins in HeLa cells. The overexpressed wild-type mucolipin colocalizes to late endocytic structures and induces an aberrant distribution of these compartments. F408del and F465L MLIV mutant proteins show a distribution similar to the wild-type protein, whereas T232P is retained in the endoplasmic reticulum. Among the mutants, only F408del induces a redistribution of the late endocytic compartment. These findings suggest that the overexpression of the mucolipin cation channel influences the dynamic equilibrium of late endocytic compartments.

The Plasma Membrane-associated Sialidase MmNEU3 Modifies the Ganglioside Pattern of Adjacent Cells Supporting Its Involvement in Cell-to-Cell Interactions

We describe herein the enzyme behavior of MmNEU3, the plasma membrane-associated sialidase from mouse (Mus musculus). MmNEU3 is localized at the plasma membrane as demonstrated directly by confocal microscopy analysis. In addition, administration of the radiolabeled ganglioside GD1a to MmNEU3-transfected cells, under conditions that prevent lysosomal activity, led to its hydrolysis into ganglioside GM1, further indicating the plasma membrane topology of MmNEU3. Metabolic labeling with [1-(3)H]sphingosine allowed the characterization of the ganglioside patterns of COS-7 cells. MmNEU3 expression in COS-7 cells led to an extensive modification of the cell ganglioside pattern, i.e. GM3 and GD1a content was decreased to about one-third compared with mock-transfected cells. At the same time, a 35% increase in ganglioside GM1 content was observed. Mixed culture of MmNEU3-transfected cells with [1-(3)H]sphingosine-labeled cells demonstrates that the enzyme present at the cell surface is able to recognize gangliosides exposed on the membrane of nearby cells. Under these experimental conditions, the extent of ganglioside pattern changes was a function of MmNEU3 transient expression. Overall, the variations in GM3, GD1a, and GM1 content were very similar to those observed in the case of [1-(3)H]sphingosine-labeled MmNEU3-transfected cells, indicating that the enzyme mainly exerted its activity toward ganglioside substrates present at the surface of neighboring cells. These results indicate that the plasma membrane-associated sialidase MmNEU3 is able to hydrolyze ganglioside substrates in intact living cells at a neutral pH, mainly through cell-to-cell interactions.

Molecular cloning and characterization of NEU4, the fourth member of the human sialidase gene family

Several mammalian sialidases have been cloned so far and here we describe the identification and expression of a new member of the human sialidase gene family. The NEU4 gene, identified by searching sequence databases for entries showing homologies to the human cytosolic sialidase NEU2, maps in 2q37 and encodes a 484-residue protein. The polypeptide contains all the typical sialidase amino acid motifs and, apart from an amino acid stretch that appears unique among mammalian sialidases, shows a high degree of homology for NEU2 and the plasma membrane-associated (NEU3) sialidases. RNA dot-blot analysis showed a low but wide expression pattern, with the highest level in liver. Transient transfection in COS7 cells allowed the detection of a sialidase activity toward the artificial substrate 4MU-NeuAc in the acidic range of pH. Immunofluorescence staining and Western blot analysis demonstrated the association of NEU4 with the inner cell membranes.

Nerve growth factor induces sphingomyelin accumulation in pheochromocytoma cells

The pheochromocytoma cells are a well-known model for studying the nerve growth factor (NGF)-induced molecular changes during the differentiation process. The involvement of sphingomyelin (SM) was studied using the fluorescent analogue of ceramide, i.e. N-lissamine rhodaminyl-(12-aminododecanoyl) D-erythro-sphingosine (C12-LRh-Cer). This fluorescent analogue is metabolically active and can be used to follow the biosynthesis of SM in intact cells. NGF induces a 4-fold increase of fluorescent SM content in PC12 cells, when loaded with C12-LRh-Cer. Treatment of PC12 cells with actinomycin D or cycloheximide completely abolishes the NGF-induced elevation of SM. Inhibition of p140(trkA) receptor by AG-879 prevents extracellular signal-regulated kinase 1/2 phosphorylation and suppresses the increase of SM. Inhibition of protein kinase C (PKC), protein kinase A (PKA) and phosphatidylinositol 3-kinase does not have any effect on NGF-induced C12-LRh-SM accumulation. On the other hand, activation of PKA or PKC with simultaneous treatment with NGF has a synergistic effect on increase of SM content. The NGF-induced SM increase in PC12 cells is an effect promoted by other differentiating agents like dibutyryl cyclic AMP or fibroblast growth factor-2 but not by a mitogenic agent like epidermal growth factor.

Ganglioside GM2 is substrate for a sialidase in MDCK cells

GM1 ganglioside carrying a fluorescent fatty acid in substitution of the natural one, has been administered to cultured Madin-Darby canine kidney (MDCK) cells for different pulse times (0.5-24 h), and its metabolic fate was followed. The fluorescent GM2, asialo-GM2, asialo-GM1 and ceramide were the only detectable metabolites. The complete absence of fluorescent GM3 is consistent with the presence in these cells of a sialidase working on GM1 and GM2 gangliosides. After treatment of the cells with chloroquine the fluorescent GM1 remained essentially undegraded, indicating a catabolic processing at lysosomal level.

The 46 kDa mannose-6-phosphate receptor contains a signal for basolateral sorting within the 19 juxtamembrane cytosolic residues

The cytosolic domain of the 46 kDa mannose-6-phosphate receptor (MPR 46) contains a signal that mediates sorting of the receptor and of a reporter protein to the basolateral surface domain of Madin-Darby canine kidney cells. Progressive truncation of the 67 cytosolic residues indicated that the 19 juxtamembrane residues are sufficient for basolateral sorting. Alanine/glycine-scanning mutagenesis identified Glu-11 and Ala-17 as the critical residues between residues 7 and 19. Glu-11 is also of critical importance for the one of the three internalization signals in the cytosolic tail of the receptor [Denzer, Weber, Hille-Rehfeld, von Figura and Pohlmann (1997) Biochem. J. 326, 497-505]. Although overlapping, the signals for basolateral sorting and internalization depend on different residues. The basolateral sorting signal of MPR 46 is distinct from tyrosine- or dileucine-based basolateral sorting signals and also lacks similarity to the few other basolateral signals that do not fall into these two classes.

Dephosphorylation of the mannose-6-phosphate recognition marker is localized in later compartments of the endocytic route. Identification of purple acid phosphatase (uteroferrin) as the candidate phosphatase

The mannose-6-phosphate (Man6P) recognition marker in lysosomal proteins is known to be dephosphorylated after the delivery of lysosomal proteins to the endosome/lysosome compartment. The rate of Man6P recognition marker inactivation depends on the cell type and lysosomal protein. In the present study we show that in BHK 21 cells, which rapidly dephosphorylate lysosomal proteins, the recognition marker is stable in the endosomal compartment, to which lysosomal enzymes such as arylsulfatase A are delivered during endocytosis at 20 degrees C. Dephosphorylation depends on the transfer of internalized lysosomal enzymes from the 20 degrees C compartment to later compartments, most likely lysosomes. This transfer is sensitive to NH4C1 and nocodazole. In vitro experiments identified purple acid phosphatase (uteroferrin) as a candidate for the lysosomal phosphatase catalyzing in vivo the dephosphorylation of Man6P recognition marker.

Effect of insulin-like growth factor II on uptake of arylsulfatase A by cultured rat hepatocytes and Kupffer cells

Mannose 6-phosphate/insulin-like growth factor II receptors have been characterized in hepatocytes and Kupffer cells isolated from adult rat liver. Affinity labeling with [125I]insulin-like growth factor II revealed a protein of Mr 250,000 in both cell types. Labeling was inhibited by an antiserum against the mannose 6-phosphate/insulin-like growth factor II receptor. In Kupffer cells, [125I]insulin-like growth factor II was also cross-linked to a second protein of Mr 130,000. In both cell types, insulin-like growth factor II was 10 times more potent than insulin-like growth factor I in displacing [125I]insulin-like growth factor II from its receptor. The mannose 6-phosphate-specific uptake of [125I]arylsulfatase A via the mannose 6-phosphate/insulin-like growth factor II receptor was inhibited by insulin-like growth factor II and antibodies against the receptor, but was not affected by insulin-like growth factor I, insulin or transforming growth factor beta 1. Cell surface iodination followed by immunoprecipitation of the mannose 6-phosphate/insulin-like growth factor II receptor showed that expression of the mannose 6-phosphate/insulin-like growth factor II receptors at the plasma membrane was increased two-fold by insulin-like growth factor II. These results suggest that binding of insulin-like growth factor II to the mannose 6-phosphate/insulin-like growth factor II receptor blocks the binding and uptake of mannose 6-phosphate-containing lysosomal enzymes and may be directly involved in a co-ordinate regulation of ligand uptake from plasma into hepatocytes and Kupffer cells.

Lysosomal acid phosphatase is not involved in the dephosphorylation of mannose 6-phosphate containing lysosomal proteins

The mannose 6-phosphate (Man6P) residues that are necessary for the targeting of newly synthesized lysosomal proteins are dephosphorylated after delivery of lysosomal proteins to lysosomes. To examine the role of lysosomal acid phosphatase (LAP) for the dephosphorylation of Man6P residues in lysosomal proteins, the phosphorylation of endogenous lysosomal proteins and of internalized arylsulfatase A was analyzed in mouse L-cells that overexpress human LAP. Non-transfected L-cells dephosphorylate endogenous lysosomal proteins slowly (half time approximately 13 h) as well as internalized arylsulfatase A. A more than 100-fold overexpression of LAP in these cells did not affect the dephosphorylation rate. Control experiments showed that the internalized arylsulfatase A and overexpressed LAP partially colocalize and that under in vitro conditions purified LAP does not dephosphorylate arylsulfatase A. Taken together, these results indicate that LAP is not the mannose 6-phosphatase that dephosphorylates lysosomal proteins after their delivery to lysosomes.

Insulin-like growth factor II overexpression does not affect sorting of lysosomal enzymes in NIH-3T3 cells

The sorting of newly synthesized mannose 6-phosphate (M6P)-containing proteins and of the major excreted protein (MEP), a lysosomal thiol proteinase, was studied in NIH-3T3 cells transfected with the cDNA of human insulin-like growth factor II (IGF II) or with the vector alone. Extracts from media and cells labelled with [35S] methionine were used for chromatography on a M6P/IGF II receptor affinity matrix or for immunoprecipitation to assess the distribution of newly synthesized M6P-containing proteins and MEP, respectively. The results indicate that the overexpression of IGF II did not affect the synthesis and the sorting of M6P-containing proteins and of MEP. The binding and uptake of the lysosomal enzyme arylsulfatase A were not affected in IGF II overexpressing cells.