EuCliD--a medical registry

OBJECTIVES

The European Clinical Database EuCliD small star, filled has been developed as a tool for supervising selected quality indicators of about 200 European dialysis centers. Major efforts had to be made to comply with local and European laws regarding data security.

METHOD

EuCliD is a Lotus Notes based flat-file database currently containing medical data of more than 14,000 dialysis patients from 10 European countries. Another 15,000 patients from 150 centers in 4 South-American countries will be added soon. Data are entered either manually or by means of interfaces to existing local data managing systems. This information is transferred to a central Lotus Notes Server. Data evaluation was performed with statistical tools like SPSS.

RESULTS

EuCliD is used as a part of the CQI (Continuous Quality Improvement) management system of Fresenius Medical Care (FMC) dialysis units. Each participating dialysis center receives (currently every half year) benchmarking reports at a regular interval. The benchmark for all quality parameters is the weighted mean of the corresponding data of all centers.

CONCLUSIONS

An obvious impact of data sampling and data evaluation on the quality of the treatments could be observed within the first one and a half years of working with EuCliD. This also concerns important outcome predictors like Kt/V and hemoglobin concentration as the outcome itself expressed in hospitalization days and survival rates. With the help of EuCliD the user is able to sample clinical data, identify problems, search for solutions with the aim of improving the dialysis treatment quality and guarantee a high-class treatment quality for all patients.

Soy milk with a high glycitein content does not reduce low-density lipoprotein cholesterolemia in type II hypercholesterolemic patients

In order to evaluate acceptability and effectiveness of a partial addition of soy protein to the daily diet in well-established type II hypercholesterolemic individuals, a double-blind study was carried out with a soy milk providing 25 g/day of protein versus an identically formulated cow's milk. Twenty patients with type II hypercholesterolemia, 4 males and 16 females, age range 38-76 years, all with cholesterol levels >7 mmol/l and low-density lipoprotein cholesterol <5.5 mmol/l, were selected. Significant triglyceride elevations (WHO Fredrickson type IIB) were present in 4 patients, and the body mass index was 24.2 +/- 3.47 kg/m(2). Different from prior studies, either with isoflavone-free products or with a moderately isoflavone-rich milk, the milk in the present study did not reduce total and low-density lipoprotein cholesterolemia. A detailed analysis of the composition showed significant differences in the isoflavone content versus products used in prior studies with a positive outcome. Soy milk isoflavones were, in fact, characterized by a high glycitein content and a low genistein/daidzein ratio. Glycitein is a minor component in most soy products, and its role in cholesterol regulation is unclear. In view of the high interest in the use of soy products for the prevention of coronary diseases, the metabolic behavior of different isoflavones in man should be better characterized, and the role of isoflavone composition of soy products given for the control of cholesterolemia needs further clarification.

Stereoselective synthesis of trifluoro- and monofluoro-analogues of frontalin and evaluation of their biological activity

The stereoselective synthesis of both enantiomers of trifluoro frontalin (-)-(1S,5R)- and (+)-(1R,5S)-8, as well as of diastereomeric monofluoro frontalines (-)-(1R,2R,5R)-18 and (-)-(1R,2S,5R)-20, analogues of the bioactive component of the aggregation pheromone of the Scolytidae insect family, has been accomplished starting from (-)-(1R)- and (+)-(1S)-menthyl (S)-toluene-4-sulfinate as a source of chirality and methyl trifluoroacetate or fluoroacetate, respectively, as sources of fluorine. The C-1 stereocenters were installed via stereoselective epoxidation of beta-sulfinyl ketones 2 and 13 with diazomethane. The bicyclic core was obtained by totally stereocontrolled and chemoselective tandem Wacker oxidation/intramolecular ketalization of the intermediate unsatured sulfinyl diols 5, 15, and 19. Axially fluorinated (-)-20 elicited a strong electroantennographic response in laboratory tests on females of Dendroctonus micans, whereas equatorially fluorinated (-)-18 and the trifluoroanalogue (-)-8 showed modest responses. Field trials using (-)-20 were not indicative owing to the locally scarce population of D. micans, but it showed some attractiveness for other Coleoptera families.

EuCliD (European Clinical Database): a database comparing different realities

Quality and variability of dialysis practice are generally gaining more and more importance. Fresenius Medical Care (FMC), as provider of dialysis, has the duty to continuously monitor and guarantee the quality of care delivered to patients treated in its European dialysis units. Accordingly, a new clinical database called EuCliD has been developed. It is a multilingual and fully codified database, using as far as possible international standard coding tables. EuCliD collects and handles sensitive medical patient data, fully assuring confidentiality. The Infrastructure: a Domino server is installed in each country connected to EuCliD. All the centres belonging to a country are connected via modem to the country server. All the Domino Servers are connected via Wide Area Network to the Head Quarter Server in Bad Homburg (Germany). Inside each country server only anonymous data related to that particular country are available. The only place where all the anonymous data are available is the Head Quarter Server. The data collection is strongly supported in each country by "key-persons" with solid relationships to their respective national dialysis units. The quality of the data in EuCliD is ensured at different levels. At the end of January 2001, more than 11,000 patients treated in 135 centres located in 7 countries are already included in the system. FMC has put the patient care at the centre of its activities for many years and now is able to provide transparency to the community (Authorities, Nephrologists, Patients.....) thus demonstrating the quality of the service.

Large-scale culture and selective maturation of human Langerhans cells from granulocyte colony-stimulating factor-mobilized CD34+ progenitors

Dendritic cells (DCs) play a critical role as APCs in the induction of the primary immune response. Their capacity for Ag processing and presentation is tightly regulated, controlled by a terminal developmental sequence accompanied by striking changes in morphology, organization, and function. The maturation process, which converts DCs from cells adapted for Ag accumulation to cells adapted for T cell stimulation, remains poorly understood due in part to difficulties in the culture and manipulation of DCs of defined lineages. To address these issues, we have devised conditions for the culture of a single DC type, Langerhans cells (LCs), using CD34+ cells from G-CSF-mobilized patients. Homogenous populations of LCs, replete with abundant immunocytochemically demonstrable Birbeck granules, could be stably maintained as immature DCs for long periods in culture. Unlike other human DC preparations, the LCs remained fully differentiated after cytokine removal. Following exposure to TNF-alpha, LPS, or CD40 ligand, the LCs could be synchronously induced to mature. Depending on the agent used, distinct types of LCs emerged differing in their capacity for T cell stimulation, IL-12 production, intracellular localization of MHC products, and overall morphology. Most interestingly, the expression of different sets of Toll family receptors is induced or down-regulated according to the maturation stimulus provided. These results strongly suggest that different proinflammatory stimuli might drive distinct developmental events.

Defective IL-12 production in mitogen-activated protein (MAP) kinase kinase 3 (Mkk3)-deficient mice

The p38 mitogen-activated protein kinase (MAPK) pathway, like the c-Jun N-terminal kinase (JNK) MAPK pathway, is activated in response to cellular stress and inflammation and is involved in many fundamental biological processes. To study the role of the p38 MAPK pathway in vivo, we have used homologous recombination in mice to inactivate the Mkk3 gene, one of the two specific MAPK kinases (MAPKKs) that activate p38 MAPK. Mkk3(-/-) mice were viable and fertile; however, they were defective in interleukin-12 (IL-12) production by macrophages and dendritic cells. Interferon-gamma production following immunization with protein antigens and in vitro differentiation of naive T cells is greatly reduced, suggesting an impaired type I cytokine immune response. The effect of the p38 MAPK pathway on IL-12 expression is at least partly transcriptional, since inhibition of this pathway blocks IL-12 p40 promoter activity in macrophage cell lines and IL-12 p40 mRNA is reduced in MKK3-deficient mice. We conclude that the p38 MAP kinase, activated through MKK3, is required for the production of inflammatory cytokines by both antigen-presenting cells and CD4(+) T cells.

Primary human mesothelioma cells express class II MHC, ICAM-1 and B7-2 and can present recall antigens to autologous blood lymphocytes

Mesothelioma cells (MMc) are considered to be weakly immunogenic and the experimental approaches attempting to induce an immune response against these cells have been disappointing. Our aim was to investigate whether MMc possess the surface accessory molecules involved in antigen presentation and whether these cells are capable of presenting recall antigens to autologous blood lymphocytes. Four primary MMc cultures were generated from malignant effusions and examined to assess whether the accessory molecules required for antigen presentation were present on their surfaces. Intercellular adhesion molecule-I (ICAM-I; CD54); class I and class II major histocompatibility complex-DR (MHCI and MHCII-DR); B7-1 (CD80.3); and B7-2 (CD86) expression by MMc was studied by immunocytochemical and/or FACScan analysis. MMc were pulsed with purified protein derivative (PPD), Tetanus toxoid (TT) and Candida albicans (CA) bodies, and incubated with autologous lymphocytes. Lymphocyte proliferation was estimated by radionucleotide incorporation. Phenotypic analysis showed the presence of MHCII-DR, ICAM-I and B7-2 on primary MMc cultures, whereas the phenotypic evaluation of 2 established MMc lines did not show the presence of the B7-1 and B7-2 molecules. In addition, MHCII-DR was detectable only after interferon gamma (IFN-gamma) stimulation. Primary MMc cultures acquired the capability to induce lymphocyte proliferation after pulse with the recall antigens. To achieve characterization of these lymphocytes, we generated a PPD-specific CD4+ T-cell clone. PPD-pulsed MMc were shown to specifically induce T-cell clone proliferation through a MHCII-DR-mediated process. We conclude that primary MMc possess the surface molecules required for antigen presentation and can present recall antigens to CD4+ lymphocytes.

High-Resolution High-Count-Rate X-ray Spectroscopy with State-of-the-Art Silicon Detectors

For the European X-ray multi-mirror (XMM) satellite mission and the German X-ray satellite ABRIXAS, fully depleted pn-CCDs have been fabricated, enabling high-speed low-noise position-resolving X-ray spectroscopy. The detector was designed and fabricated with a homogeneously sensitive area of 36 cm(2). At 150 K it has a noise of 4 e(-) r.m.s., with a readout time of the total focal plane array of 4 ms. The maximum count rate for single-photon counting was 10(5) counts s(-1) under flat-field conditions. In the integration mode more than 10(9) counts s(-1) can be detected at 6 keV. Its position resolution is of the order of 100 micro m. The quantum efficiency is higher than 90% from carbon K X-rays (277 eV) up to 10 keV. New cylindrical silicon drift detectors have been designed, fabricated and tested. They comprise an integrated on-chip amplifier system with continuous reset, on-chip voltage divider, electron accumulation layer stabilizer, large area, homogeneous radiation entrance window and a drain for surface-generated leakage current. At count rates as high as 2 x 10(6) counts cm(-2) s(-1), they still show excellent spectroscopic behaviour at room-temperature operation in single-photon detection mode. The energy resolution at room temperature is 220 eV at 6 keV X-ray energy and 140 eV at 253 K, being achieved with Peltier coolers. These systems were operated at synchrotron light sources (ESRF, HASYLAB and NLS) as X-ray fluorescence spectrometers in scanning electron microscopes and as ultra low noise photodiodes. The operation of a multi-channel silicon drift detector system is already foreseen at synchrotron light sources for X-ray holography experiments. All systems are fabricated in planar technology having the detector and amplifiers monolithically integrated on high-resistivity silicon.

Developmental regulation of MHC class II transport in mouse dendritic cells

Dendritic cells (DCs) have the unique capacity to initiate primary and secondary immune responses. They acquire antigens in peripheral tissues and migrate to lymphoid organs where they present processed peptides to T cells. DCs must therefore exist in distinct functional states, an idea that is supported by observations that they downregulate endocytosis and upregulate surface molecules of the class II major histocompatibility complex (MHC) upon maturation. Here we investigate the features of DC maturation by reconstituting the terminal differentiation of mouse DCs in vitro and in situ. We find that early DCs, corresponding to those found in peripheral tissues, exhibit a phenotype in which most class II molecules are intracellular and localized to lysosomes. Upon maturation, these cells give rise to a new intermediate phenotype in which intracellular class II molecules are found in peripheral non-lysosomal vesicles, similar to the specialized CIIV population seen in B cells. The intermediate cells then differentiate into late DCs which express almost all of their class II molecules on the plasma membrane. These variations in class II compartmentalization are accompanied by dramatic alterations in the intracellular transport of the new class II molecules and in antigen presentation. We found that although early DCs could not present antigen immediately after uptake, efficient presentation of the previously internalized antigen occurred after maturation, 24-48 hours later. By regulating class II transport and compartmentalization, DCs are able to delay antigen display, a property crucial to their role in immune surveillance.

Comprehensive case management in the private sector for patients with severe mental illness

Intensive case management for severely psychiatrically ill patients is a relatively new phenomenon in the private sector. The authors describe a comprehensive case management program designed at Blue Cross Blue Shield of Massachusetts to meet the needs of the most severely ill psychiatric patients in a private managed care environment. The case management program emphasizes involvement of patients in creating comprehensive treatment plans; development of a relationship between case managers, patients and their families, and providers; and clinical coordination between the public and private sectors to create individualized treatment plans. The program's case managers are able to flex the benefit limitations of a managed care or indemnity plan to integrate public and private services and can enlist providers outside a managed care network. The paper describes service utilization by the first 33 patients who participated in the program for one year.

Identification and characterization of homologues of the Exocyst component Sec10p

The SEC10 gene product is a member of the Exocyst complex essential for exocytosis in the budding yeast Saccharomyces cerevisiae. We report here the cloning and characterization of human Sec10p (hSec10p; GenBank accession number U85946). hSec10p is a 77-kDa protein with 23% amino acid identity to yeast Sec10p and 37% identity to a C. elegans protein found in the database. Northern and Western blot analyses indicate that hSec10 has a broad tissue distribution. Immunofluorescence staining of COS cells cotransfected with hSec10p and a mammalian Sec8p demonstrates that these two proteins have an identical distribution in the cell including a localization in the peripheral cytoplasm. These data suggest that hSec10p is a component of the mammalian counterpart of the yeast Exocyst complex essential for post-Golgi traffic.

Yeast protein translocation complex: isolation of two genes SEB1 and SEB2 encoding proteins homologous to the Sec61 beta subunit

A yeast gene (cDNA clone) was isolated in a screen for suppressors of secretion-defective sec15-1 mutation. This gene encodes a protein homologous to the beta subunit of the mammalian Sec61 protein complex functioning in protein translocation into the endoplasmic reticulum (ER). The predicted protein, Seb1p, consists of 82 amino acids and contains one potential membrane-spanning region at the C-terminus but no N-terminal signal sequence. Seb1p shows 30% identity to the mammalian Sec61 beta subunit and 34% identity to the Arabidopsis thaliana Sec61 beta subunit. Overexpression of SEB1 from a multicopy plasmid suppressed the temperature sensitivity of sec61-2 and sec61-3 mutants. Immunofluorescence and immunoelectron microscopy indicated that Seb1p resides in the ER membranes with the hydrophilic N-terminus exposed to the cytoplasm. The in vitro translated Seb1p was post-translationally inserted into microsomal membranes. As the chromosomal disruption of the SEB1 gene was not lethal, potential homologous genes were screened by heterologous hybridization. The SEB1 homologue thus isolated, SEB2, encodes a protein 53% identical to Seb1p. Disruption of the chromosomal SEB2 was not lethal whereas the double disruption of SEB1 and SEB2 resulted in a temperature-sensitive phenotype. This study further emphasizes the evolutionary conservation of the ER protein translocation apparatus and provides novel genetic tools for its functional analysis.

Blood cell redistribution in the lung after administration of recombinant human granulocyte-macrophage colony-stimulating factor

Granulocyte-macrophage colony-stimulating factor (GM-CSF), in addition to being a haematopoietic growth factor, has been shown to stimulate in vitro the production of interleukins 1, 6 and 8 (IL-1, IL-6 and IL-8), tumour necrosis factor-alpha (TNF-alpha) and GM-CSF by polymorphonuclear cells (PMNs), alveolar macrophages (AMs), fibroblasts and endothelial cells of the lung, and the growth and differentiation of resident alveolar macrophages. The aim of this study was to establish whether recombinant GM-CSF (rhGM-CSF), administered subcutaneously at a dose of 5 micrograms.kg-1 for 3 days in five patients with unresectable non-small cell lung cancer before starting chemotherapy, induces an increase in the alveolar cell count, and whether these cellular lung variations may be related to increases in the above-mentioned cytokines. In the bronchoalveolar lavage fluid (BALF) total cell count, polymorphonuclear cells, neutrophils, and alveolar macrophages increased significantly in comparison with the baseline, and the extent of variation of the BAL cell count was considerably greater than that of the circulating leucocytes. The mean levels of all the cytokines increased, but a significant difference with respect to the basal condition was observed only for IL-6 and IL-8. After rhGM-CSF treatment, significant correlations were found between neutrophil counts and the levels of IL-6 and IL-8. In conclusion, rhGM-CSF administration induces a cellular expansion in the lung, and the neutrophil increase appears to be related to increased levels of IL-8.

Blood cell redistribution in the lung after administration of recombinant human granulocyte-macrophage colony-stimulating factor

Granulocyte-macrophage colony-stimulating factor (GM-CSF), in addition to being a haematopoietic growth factor, has been shown to stimulate in vitro the production of interleukins 1, 6 and 8 (IL-1, IL-6 and IL-8), tumour necrosis factor-alpha (TNF-alpha) and GM-CSF by polymorphonuclear cells (PMNs), alveolar macrophages (AMs), fibroblasts and endothelial cells of the lung, and the growth and differentiation of resident alveolar macrophages. The aim of this study was to establish whether recombinant GM-CSF (rhGM-CSF), administered subcutaneously at a dose of 5 micrograms.kg-1 for 3 days in five patients with unresectable non-small cell lung cancer before starting chemotherapy, induces an increase in the alveolar cell count, and whether these cellular lung variations may be related to increases in the above-mentioned cytokines. In the bronchoalveolar lavage fluid (BALF) total cell count, polymorphonuclear cells, neutrophils, and alveolar macrophages increased significantly in comparison with the baseline, and the extent of variation of the BAL cell count was considerably greater than that of the circulating leucocytes. The mean levels of all the cytokines increased, but a significant difference with respect to the basal condition was observed only for IL-6 and IL-8. After rhGM-CSF treatment, significant correlations were found between neutrophil counts and the levels of IL-6 and IL-8. In conclusion, rhGM-CSF administration induces a cellular expansion in the lung, and the neutrophil increase appears to be related to increased levels of IL-8.

Co-expression of B7-1 and ICAM-1 on tumors is required for rejection and the establishment of a memory response

Although the transfection of B7-1 cDNA into a few mouse tumor cell lines can induce anti-tumor T cell immunity, its expression alone is ineffective in many other tumor cell lines tested. We were interested to study what factors limit B7-1 co-stimulatory activity, and decided to investigate whether B7-1 requires the cooperation of ICAM-1 to provide the minimal co-stimulatory signal for establishing an efficient anti-tumor immunity. We show that the transfection of B7-1 cDNA into three ICAM-1+ (plasmocytoma J558L, T lymphomas EL-4 and RMA), but not into two ICAM-1- tumors cell lines (adenocarcinoma TS/A and melanoma B16.F1), is sufficient to induce their complete rejection in syngeneic mice. The expression of ICAM-1 is necessary for the rejection of the B7 expressing tumors, since the primary response elicited by B7-1+ EL-4 and RMA clones expressing reduced levels of ICAM-1 is severely reduced. Furthermore, super-transfection of ICAM-1 cDNA into B7-1+ adenocarcinoma and melanoma clones optimizes their primary rejection. Histologic examination of transfected tumors reveals that B7-1 and ICAM-1 exert a potent pro-inflammatory activity. The intra-tumor infiltration is composed of both eosinophils and lymphomonocytes, and is already massive 5 days after the tumor challenge. The primary rejection of the B7-1+ ICAM-1+ tumors depends critically on CD8+ T cells, natural killer cells and granulocytes, but is independent of CD4+ T cells. Remarkably, in addition to its effects on the early phases of the immune response, the co-expression of ICAM-1 and B7-1 on tumors is also necessary for the efficient induction of a memory response. In fact, only the primary challenge with B7-1+, ICAM-1+ tumor cells protects the majority of the mice from a second injection of parental tumor cells. Collectively, our findings indicate that B7-1 and ICAM-1 are fundamental components for triggering the primary rejection of tumors and establishing a protective memory response. These findings may help to define new strategies for the rational application of co-stimulation in tumor immunotherapy.

In vivo effect of human granulocyte-macrophage colony-stimulating factor (GM-CSF) on neutrophil GM-CSF receptors

The effect of in vivo administration of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) on neutrophils GM-CSF receptor, was investigated in patients with neoplastic diseases and normal hematopoiesis. Patients were divided into two groups. Group A received a single dose of rhGM-CSF (5 micrograms/kg/day) and receptor studies were performed 90 min and 48 h after treatment. Group B received three doses, administered subcutaneously every 24 h and receptor studies were performed 90 min after first injection and 24 h after the last. Before treatment neutrophils only displayed high-affinity receptors (KD 85 +/- 53 pM; number of receptors/cell 1318 +/- 567). The first injection of rhGM-CSF produced a transient leucopenia and the internalization of GM-CSF receptor on neutrophils in both groups of patients: 90 min after s.c. administration receptors could not be detected with conventional binding studies. In group A patients, 48 h after a single dose of rhGM-CSF, receptors, albeit with a decreased affinity (KD = 240 +/- 131 pM; number of receptors/cell 783 +/- 494) were again expressed. In group B patients, 24 h after the last rhGM-CSF injection, low intermediate affinity receptors not present before treatment appeared (KD 720 +/- 175 pM; number of receptor/cell 1222 +/- 179). They were associated with a low number of high affinity receptors (KD = 9 +/- 4 pM; number of receptors/cell 106 +/- 44). These observations indicate that more than one type of GM-CSF receptor may exist on neutrophils. It may be suggested that in vivo the regulation of the GM-CSF receptor is different from that in vitro and is related to the presence of the cytokine in patient blood.

Soy and cholesterol reduction: clinical experience

A role of vegetable proteins in reducing coronary artery disease risk was postulated as long ago as 1909 in Russia by Ignatowski. The protein hypothesis of atherosclerosis was pursued by many investigators, who studied the possible role of animal vs. vegetable protein in modifying concentrations of plasma lipids and thus cardiovascular disease risk. Over the past 20 y, our research group has examined the potential of a diet based on vegetable protein (in most cases, textured vegetable protein, or TVP) to modify plasma lipid concentrations. Textured products allow administration of a large percentage of protein (up to 50-60% in the product) and are available in a variety of food items. We studied > 1000 patients. An extensive review of the literature indicates that similar findings have been reported by others when administering TVP or TVP-like items to subjects with well-characterized hypercholesterolemia (Fredrickson type II). Data are less consistent for treatment of patients with marginal hypercholesterolemia or hypercholesterolemia already corrected by a standard diet before administration of soy products. The TVP diet, is, however, effective when normolipidemic individuals are made hypercholesterolemic by dietary cholesterol administration. These and other findings suggest that, in man, similar to experimental animals, soy protein may in some way up-regulate LDL receptors depressed by hypercholesterolemia or by dietary cholesterol administration.

Tnp-alpha determination in serum and pleural effusion in patients with lung-cancer

The relationship between Tumor Necrosis Factor-alpha (TNF-alpha) in the serum and pleural fluid of lung cancer patients and the extent and the histological cell type was studied. TNF-(a)lpha level was determined in the serum of 68 patients with lung cancer [51 non-small cell lung cancer (NSCLC) and 17 small cell lung cancer (SCLC)] and in pleural fluid of 30 patients with lung cancer (22 NSCLC, 11 of them positive for neoplastic cells and 8 SCLC, 7 of them positive). Sera of 31 healthy subjects and the pleural fluid of 15 non-malignant pleural effusions were tested as controls. TNF-alpha serum level was increased in patients with lung cancer (healthy subjects 7.8+/-3.3 pg/ml; lung cancer 16.2+/-9.1 pg/ml), in NSCLC as well as SCLC and a relationship with the extent of the disease was found in both the histological types. In pleural fluid, no differences of TNF-alpha level were observed between neoplastic and benign inflammatory effusion, between SCLC and NSCLC or between cases positive and negative for the presence of neoplastic cells. Serum TNF-alpha may be an indicator of tumour burden; conversely, TNF-alpha in pleural fluid, was unable to discriminate between neoplastic and benign effusion.

Specific interactions of Mss4 with members of the Rab GTPase subfamily

Mss4 is a mammalian protein that was identified as a suppressor of a yeast secretory mutant harboring a mutation in the GTPase Sec4 and was found to stimulate GDP release from this protein. We have now performed a biochemical characterization of the Mss4 protein and examined the specificity of its association with mammalian GTPases. Mss4 is primarily a soluble protein with a widespread tissue distribution. Recombinant Mss4 binds GTPases present in tissue extracts, and by a gel overlay assay binds specifically Rab Rab10proteins. We further define the Mss4-GTPase interaction to a subset of Rabs belonging to the same subfamily branch which include Rab1, Rab3, Rab8, Rab10, Sec4 and Ypt1 but not Rab2, Rab4, Rab5, Rab6, Rab9 and Rab11. Accordingly, Mss4 co-precipitates from a brain extract with Rab3a but not Rab5. Mss4 only stimulates GDP release from, and the association of GTP gamma S with, this Rab subset. Recombinant Mss4 and Rab3a form a stable complex in solution that is dissociated with either GDP or GTP gamma S. Injection of Mss4 into the squid giant nerve terminal enhances neurotransmitter release. These results suggest that Mss4 behaves as a guanylnucleotide exchange factor (GEF) for a subset of Rabs to influence distinct vesicular transport steps along the secretory pathway.

O-linked oligosaccharides in yeast glycosyl phosphatidylinositol-anchored protein gp115 are clustered in a serine-rich region not essential for its function

The protein gp115 is an exocellular yeast glycoprotein modified by O- and N-glycosylation and attached to the plasma membrane through a glycosylphosphatidylinositol. The more remarkable structural feature in gp115 is the presence of a 36-amino acid serine-rich region. Similar sequences have been found in mammalian glycoproteins, such as the low density lipoprotein receptor, the decay-accelerating factor, and the mucins, where they are targets of multiple sites of O-glycosylation. The modification of these regions greatly influences their conformation and gives rise to "rodlike" structures. In this work, we have deleted or duplicated the Ser-rich region of gp115. The analysis of the size and glycosylation state of both mutant proteins indicates that about 52% of the total contribution of the O-glycosylation to the mass of the protein is concentrated in this region. The phenotype of ggp1 null mutant expressing the mutant proteins was also analyzed to understand if this region is important for gp115 function. The defects of slow growth rate and resistance to zymolyase of the ggp1 cells are completely complemented by both mutant proteins, suggesting that this region could be dispensable for gp115 function. A tentative model of gp115 structure is presented on the basis of the obtained data.