The glycosylphosphatidylinositol anchor: a complex membrane-anchoring structure for proteins

IDH mutant gliomas escape natural killer cell immune surveillance by downregulation of NKG2D ligand expression

BACKGROUND

Diffuse gliomas are poorly immunogenic, fatal brain tumors. The basis for insufficient antitumor immunity in diffuse gliomas is unknown. Gain-of-function mutations in isocitrate dehydrogenases (IDH1 and IDH2) promote diffuse glioma formation through epigenetic reprogramming of a number of genes, including immune-related genes. Here, we identify epigenetic dysregulation of natural killer (NK) cell ligand genes as significant contributors to immune escape in glioma.

METHODS

We analyzed the database of The Cancer Genome Atlas for immune gene expression patterns in IDH mutant or wild-type gliomas and identified differentially expressed immune genes. NKG2D ligand expression levels and NK cell-mediated lysis were measured in IDH mutant and wild-type patient-derived glioma stem cells and genetically engineered astrocytes. Finally, we assessed the impact of hypomethylating agent 5-aza-2'deoxycytodine (decitabine) as a potential NK cell sensitizing agent in IDH mutant cells.

RESULTS

IDH mutant glioma stemlike cell lines exhibited significantly lower expression of NKG2D ligands compared with IDH wild-type cells. Consistent with these findings, IDH mutant glioma cells and astrocytes are resistant to NK cell-mediated lysis. Decitabine increases NKG2D ligand expression and restores NK-mediated lysis of IDH mutant cells in an NKG2D-dependent manner.

CONCLUSIONS

IDH mutant glioma cells acquire resistance to NK cells through epigenetic silencing of NKG2D ligands ULBP1 and ULBP3. Decitabine-mediated hypomethylation restores ULBP1 and ULBP3 expression in IDH mutant glioma cells and may provide a clinically useful method to sensitize IDH mutant gliomas to NK cell-mediated immune surveillance in patients with IDH mutated diffuse gliomas.

Glypican-1 nanoliposomes for potentiating growth factor activity in therapeutic angiogenesis

Therapeutic angiogenesis is a highly appealing concept for treating tissues that become ischemic due to vascular disease. A major barrier to the clinical translation of angiogenic therapies is that the patients that are in the greatest need of these treatments often have long term disease states and co-morbidities, such as diabetes and obesity, that make them resistant to angiogenic stimuli. In this study, we identified that human patients with type 2 diabetes have reduced levels of glypican-1 in the blood vessels of their skin. The lack of this key co-receptor in the tissue may make the application of exogenous angiogenic growth factors or cell therapies ineffective. We created a novel therapeutic enhancer for growth factor activity consisting of glypican-1 delivered in a nanoliposomal carrier (a "glypisome"). Here, we demonstrate that glypisomes enhance FGF-2 mediated endothelial cell proliferation, migration and tube formation. In addition, glypisomes enhance FGF-2 trafficking by increasing both uptake and endosomal processing. We encapsulated FGF-2 or FGF-2 with glypisomes in alginate beads and used these to deliver localized growth factor therapy in a murine hind limb ischemia model. Co-delivery of glypisomes with FGF-2 markedly increased the recovery of perfusion and vessel formation in ischemic hind limbs of wild type and diabetic mice in comparison to mice treated with FGF-2 alone. Together, our findings support that glypisomes are effective means for enhancing growth factor activity and may improve the response to local angiogenic growth factor therapies for ischemia.

Evaluation of Fluorescently Labeled Aerolysin as a New Kind of Reagent for Flow Cytometry Tests: Optimization of Use of FLAER, Hints, and Limits

OBJECTIVES

Diagnostic tests for paroxysmal nocturnal hemoglobinuria (PNH) are currently based on flow cytometry techniques. Typically, these tests use antibodies against glycosylphosphatidylinositol (GPI)-anchored proteins, but a new approach has been described recently, using a novel reagent named FLAER (fluorescently labeled aerolysin). In this work, we evaluate the performance and highlight the peculiarities of using this new reagent.

RESULTS

We investigated the general conditions of staining and explored optimal labeling settings. We found that the kinetics of the FLAER labeling is slightly different from that of antibodies. Our results led us to select a 30-minute incubation period at room temperature using 50 nmol/L as a final concentration of FLAER. As the nonspecific binding was dependent on the balance between FLAER and its ligand, the number of target cells was also found critical. In addition, sample preparation affected FLAER staining, and the lyse-before-stain preparation was preferred. Interestingly, FLAER affinity seems restricted to certain types of GPI anchors, making it unsuitable for exploration of RBCs. Finally, we aimed to evaluate FLAER as a possible single diagnostic tool; we studied cellular background in non-PNH samples and found a limit of detection close to 0.01% in optimal conditions.

CONCLUSIONS

The performance of the FLAER labeling on leukocytes proves that this reagent is a valuable tool for PNH diagnosis and particularly appropriate for high-sensitivity tests in laboratories aiming to detect minor PNH clones.

Cargo-selective apical exocytosis in epithelial cells is conducted by Myo5B, Slp4a, Vamp7, and Syntaxin 3

The motor protein Myo5B and t-SNARE Stx3 drive cargo-selective apical exocytosis in polarized epithelial cells in a pathway dependent on v-SNARE–like Slp4a, v-SNARE Vamp7, Sec1/Munc18-like protein Munc18-2, and the Rab11/8 cascade.

Mutations in the motor protein Myosin Vb (Myo5B) or the soluble NSF attachment protein receptor Syntaxin 3 (Stx3) disturb epithelial polarity and cause microvillus inclusion disease (MVID), a lethal hereditary enteropathy affecting neonates. To understand the molecular mechanism of Myo5B and Stx3 interplay, we used genome editing to introduce a defined Myo5B patient mutation in a human epithelial cell line. Our results demonstrate a selective role of Myo5B and Stx3 for apical cargo exocytosis in polarized epithelial cells. Apical exocytosis of NHE3, CFTR (cystic fibrosis transmembrane conductance regulator), and GLUT5 required an interaction cascade of Rab11, Myo5B, Slp4a, Munc18-2, and Vamp7 with Stx3, which cooperate in the final steps of this selective apical traffic pathway. The brush border enzymes DPPIV and sucrase-isomaltase still correctly localize at the apical plasma membrane independent of this pathway. Hence, our work demonstrates how Myo5B, Stx3, Slp4a, Vamp7, Munc18-2, and Rab8/11 cooperate during selective apical cargo trafficking and exocytosis in epithelial cells and thereby provides further insight into MVID pathophysiology.

Structural analysis and immunostimulatory activity of glycopeptides from Paecilomyces sinensis

The parasitic fungus, Paecilomyces sinensis, is used to produce Cordyceps materials as a succedaneum of natural Cordyceps sinensis (C. sinensis) in China.

Synthesis of glycosylphosphatidylinositol (GPI)-anchor glycolipids bearing unsaturated lipids

A new strategy involving 2-naphthyl-methyl ethers as permanent protecting groups and their easy removal under acidic conditions is the key to the synthesis of complex glycosylphosphatidylinositol glycolipids containing unsaturated lipids.

Characterization of Plasmodium phosphatidylserine decarboxylase expressed in yeast and application for inhibitor screening

Phospholipid biosynthesis is critical for the development, differentiation and pathogenesis of several eukaryotic pathogens. Genetic studies have validated the pathway for phosphatidylethanolamine synthesis from phosphatidylserine catalyzed by phosphatidylserine decarboxylase enzymes (PSD) as a suitable target for development of antimicrobials; however no inhibitors of this class of enzymes have been discovered. We show that the Plasmodium falciparum PSD can restore the essential function of the yeast gene in strains requiring PSD for growth. Genetic, biochemical and metabolic analyses demonstrate that amino acids between positions 40 and 70 of the parasite enzyme are critical for proenzyme processing and decarboxylase activity. We used the essential role of Plasmodium PSD in yeast as a tool for screening a library of anti-malarials. One of these compounds is 7-chloro-N-(4-ethoxyphenyl)-4-quinolinamine, an inhibitor with potent activity against P. falciparum, and low toxicity toward mammalian cells. We synthesized an analog of this compound and showed that it inhibits PfPSD activity and eliminates Plasmodium yoelii infection in mice. These results highlight the importance of 4-quinolinamines as a novel class of drugs targeting membrane biogenesis via inhibition of PSD activity.

With or without rafts? Alternative views on cell membranes

The fundamental mechanisms of protein and lipid organization at the plasma membrane have continued to engage researchers for decades. Among proposed models, one idea has been particularly successful which assumes that sterol-dependent nanoscopic phases of different lipid chain order compartmentalize proteins, thereby modulating protein functionality. This model of membrane rafts has sustainably sparked the fields of membrane biophysics and biology, and shifted membrane lipids into the spotlight of research; by now, rafts have become an integral part of our terminology to describe a variety of cell biological processes. But is the evidence clear enough to continue supporting a theoretical concept which has resisted direct proof by observation for nearly twenty years? In this essay, we revisit findings that gave rise to and substantiated the raft hypothesis, discuss its impact on recent studies, and present alternative mechanisms to account for plasma membrane heterogeneity.

Both PIGA and PIGL mutations cause GPI-a deficient isolates in the Tk6 cell line

Molecular analysis of proaerolysin selected glycosylphosphatidylinositol anchor (GPI-a) deficient isolates in the TK6 cell line was performed. Initial studies found that the expected X-linked PIGA mutations were rare among the spontaneous isolates but did increase modestly after ethyl methane sulfate (EMS) treatment (but to only 50% of isolates). To determine the molecular bases of the remaining GPI-a deficient isolates, real-time analysis for all the 25 autosomal GPI-a pathway genes was performed on the isolates without PIGA mutations, determining that PIGL mRNA was absent for many. Further analysis determined these isolates had several different homozygous deletions of the 5' region of PIGL (17p12-p22) extending 5' (telomeric) through NCOR1 and some into the TTC19 gene (total deletion >250,000 bp). It was determined that the TK6 parent had a hemizygous deletion in 17p12-p22 (275,712 bp) extending from PIGL intron 2 into TTC19 intron 7. Second hit deletions in the other allele in the GPI-a deficient isolates led to the detected homozygous deletions. Several of the deletion breakpoints including the original first hit deletion were sequenced. As strong support for TK6 having a deletion, a number of the isolates without PIGA mutations nor homozygous PIGL deletions had point mutations in the PIGL gene. These studies show that the GPI-a mutation studies using TK6 cell line could be a valuable assay detecting point and deletion mutations in two genes simultaneously.

Revisiting Apoplastic Auxin Signaling Mediated by AUXIN BINDING PROTEIN 1

It has been suggested that AUXIN BINDING PROTEIN 1 (ABP1) functions as an apoplastic auxin receptor, and is known to be involved in the post-transcriptional process, and largely independent of the already well-known SKP-cullin-F-box-transport inhibitor response (TIR1) /auxin signaling F-box (AFB) (SCF(TIR1/AFB)) pathway. In the past 10 years, several key components downstream of ABP1 have been reported. After perceiving the auxin signal, ABP1 interacts, directly or indirectly, with plasma membrane (PM)-localized transmembrane proteins, transmembrane kinase (TMK) or SPIKE1 (SPK1), or other unidentified proteins, which transfer the signal into the cell to the Rho of plants (ROP). ROPs interact with their effectors, such as the ROP interactive CRIB motif-containing protein (RIC), to regulate the endocytosis/exocytosis of the auxin efflux carrier PIN-FORMED (PIN) proteins to mediate polar auxin transport across the PM. Additionally, ABP1 is a negative regulator of the traditional SCF(TIR1/AFB) auxin signaling pathway. However, Gao et al. (2015) very recently reported that ABP1 is not a key component in auxin signaling, and the famous abp1-1 and abp1-5 mutant Arabidopsis lines are being called into question because of possible additional mutantion sites, making it necessary to reevaluate ABP1. In this review, we will provide a brief overview of the history of ABP1 research.

A novel PIGN mutation and prenatal diagnosis of inherited glycosylphosphatidylinositol deficiency

Glycosylphosphatidylinositol (GPI) anchors tether proteins to the extracellular face of eukaryotic plasma membranes. Defects in the human GPI anchor biosynthetic pathway cause inherited GPI deficiencies (IGDs) characterized by multiple congenital anomalies: dysmorphic faces, developmental delay, hypotonia, and epilepsy. We report the case of a 6-year-old boy with severe psychomotor developmental delay, epilepsy, and decreased granulocyte surface expression of GPI-anchored protein that suggested autosomal recessive GPI deficiency. The case underwent target exome sequencing to screen for IGDs. Target exome sequencing of the proband identified an apparently homozygous c.808T > C (p.Ser270Pro) mutation in PIGN, a gene involved in the GPI anchor biosynthetic pathway. As his parents were expecting another child, genetic carrier screening was conducted for the parents. Direct sequencing of the parents identified a heterozygous c.808T > C PIGN mutation in the father but none in the mother. To identify the mother's mutation, we performed semi-quantitative real-time PCR of the PIGN exons and long PCR, identifying a microdeletion in PIGN (del exons 2-14). The proband had inherited this microdeletion from his mother. Prenatal diagnosis of the fetus revealed that it was a heterozygous carrier of the mother's pathogenic allele. Here, we report a sporadic case of inherited GPI deficiency with a PIGN mutation and the first case of prenatal diagnosis for GPI deficiency.

GPI-anchored protein organization and dynamics at the cell surface

The surface of eukaryotic cells is a multi-component fluid bilayer in which glycosylphosphatidylinositol (GPI)-anchored proteins are an abundant constituent. In this review, we discuss the complex nature of the organization and dynamics of GPI-anchored proteins at multiple spatial and temporal scales. Different biophysical techniques have been utilized for understanding this organization, including fluorescence correlation spectroscopy, fluorescence recovery after photobleaching, single particle tracking, and a number of super resolution methods. Major insights into the organization and dynamics have also come from exploring the short-range interactions of GPI-anchored proteins by fluorescence (or Förster) resonance energy transfer microscopy. Based on the nanometer to micron scale organization, at the microsecond to the second time scale dynamics, a picture of the membrane bilayer emerges where the lipid bilayer appears inextricably intertwined with the underlying dynamic cytoskeleton. These observations have prompted a revision of the current models of plasma membrane organization, and suggest an active actin-membrane composite.

Labeling Cell Surface GPIs and GPI-Anchored Proteins through Metabolic Engineering with Artificial Inositol Derivatives

Glycosylphosphatidylinositol (GPI) anchoring of proteins to the cell surface is important for various biological processes, but GPI-anchored proteins are difficult to study. An effective strategy was developed for the metabolic engineering of cell-surface GPIs and GPI-anchored proteins by using inositol derivatives carrying an azido group. The azide-labeled GPIs and GPI-anchored proteins were then tagged with biotin on live cells through a click reaction, which allows further elaboration with streptavidin-conjugated dyes or other molecules. The strategy can be used to label GPI-anchored proteins with various tags for biological studies.

Met Signaling Cascade Is Amplified by the Recruitment of Phosphorylated Met to Lipid Rafts via CD24 and Leads to Drug Resistance in Endometrial Cancer Cell Lines

Endometrial cancer is the most prevalent gynecologic cancer in the Western world, and the number of advanced chemotherapy-resistant cancers is increasing with the absolute increase in patients. The development of resistance to chemotherapeutic drugs by cancer cells represents a major challenge in the clinical cure of advanced and metastatic cancers. CD24 has been reported to be a marker for a poor prognosis in several tumors, and we herein examined the functions of CD24 in human endometrioid adenocarcinoma cell lines and evaluated how it contributes to cancer drug resistance. We demonstrated that CD24 was responsible for the recruitment of phosphorylated Met to the lipid raft domain of the cell membrane, resulting in amplification of the Met signaling cascade, ultimately leading endometrial cancer cells to express higher levels of ATP-binding cassette (ABC) transporters. Our findings suggest that CD24-mediated amplification of the Met cascade may contribute to the drug resistance of endometrial cancer.

Significance of the detection of paroxysmal nocturnal hemoglobinuria clones in patients with multiple myeloma undergoing autologous stem cell transplantation

OBJECTIVE/BACKGROUND

There are reports about the presence of paroxysmal nocturnal hemoglobinuria (PNH) clones in multiple myeloma (MM), but these have been demonstrated only in red blood cells (RBCs) and the previous reports utilized an obsolete diagnostic method. We carried out a study to identify the clones by flow cytometry (FC) and to understand their clinical significance.

METHODS

A prospective study on consecutive patients with newly diagnosed MM who were candidates for autologous stem cell transplantation (ASCT) from 2008 to 2012. We screened peripheral blood samples by FC for CD55- and/or CD59-deficient RBC, neutrophils, and monocytes. PNH testing was carried out at diagnosis, before ASCT and 3 months after ASCT, as well as sporadically during MM remission and at disease relapse.

RESULTS

A total of 31 patients were included in the study. PNH clones reaching a median size of 10.8% (range 4.0-18.7%) were found in 10 patients (32.3%). Clones were detected at diagnosis in nine patients and 3 months after ASCT in one patient. A correlation between the presence of the clones and subclinical hemolysis was observed. Nevertheless, the presence of the clones did not influence the overall management and prognosis of the patients.

CONCLUSION

We confirmed findings of previous reports with current diagnostic guidelines and showed that although the size of the clones may be relatively large, their presence is probably not detrimental. The clinical significance of these clones and the possible mechanisms underlying their expansion in MM must be a subject of further investigation.

Post-translational modifications in regulation of pathogen surveillance and signaling in plants: The inside- (and perturbations from) outside story

In its lifetime a plant is exposed to pathogens of diverse types. Although methods of surveillance are broadly pathogen-individualized, immune signaling ultimately connect to common core networks maintained by key protein hubs. Defense elicitations modulate these hubs to re-allocate energy from central metabolic pathway into processes that execute immunity. Because unregulated defenses severely decrease growth and productivity of the host, signaling regulators within the networks function to achieve cellular equilibrium once the threat is minimized. Protein modifications by post-translational processes regulate the molecular switches and crosstalks between interconnected pathways spatially and temporally. Covalent modification of host targets connected to hubs are strategies used by most virulent effectors and result in re-routing signals to suppress host defenses. Resistance is a result of activation of specialized classes of receptors that short-circuit effector activities by co-localizing via post-translational modifications (PTMs) with effector targets. Despite advancement in proteome methodologies, our understanding of how PTMs regulate plant defenses remains elusive. This review presents protein-modifications as forefront regulators of plant innate immunity.

Identification of genes associated with blood feeding in the cat flea, Ctenocephalides felis

Background

The cat flea (Ctenocephalides felis) is a blood-feeding ectoparasitic insect and particular nuisance pest of companion animals worldwide. Identification of genes that are differentially expressed in response to feeding is important for understanding flea biology and discovering targets for their control.

Methods

C. felis fleas were maintained and fed for 24 h using an artificial rearing system. The technique of suppression subtractive hybridization was employed to screen for mRNAs specifically expressed in fed fleas.

Results

We characterized nine distinct full-length flea transcripts that exhibited modulated or de novo expression during feeding. Among the predicted protein sequences were two serine proteases, a serine protease inhibitor, two mucin-like molecules, a DNA topoisomerase, an enzyme associated with GPI-mediated cell membrane attachment of proteins and a component of the insect innate immune response.

Conclusions

Our results provide a molecular insight into the physiology of flea feeding. The protein products of the genes identified may play important roles during flea feeding in terms of blood meal digestion, cellular growth/repair and protection from feeding-associated stresses.

Comparative Haploid Genetic Screens Reveal Divergent Pathways in the Biogenesis and Trafficking of Glycophosphatidylinositol-Anchored Proteins

Glycophosphatidylinositol-anchored proteins (GPI-APs) play essential roles in physiology, but their biogenesis and trafficking have not been systematically characterized. Here, we took advantage of the recently available haploid genetics approach to dissect GPI-AP pathways in human cells using prion protein (PrP) and CD59 as model molecules. Our screens recovered a large number of common and unexpectedly specialized factors in the GPI-AP pathways. PIGN, PGAP2, and PIGF, which encode GPI anchor-modifying enzymes, were selectively isolated in the CD59 screen, suggesting that GPI anchor composition significantly influences the biogenesis of GPI-APs in a substrate-dependent manner. SEC62 and SEC63, which encode components of the ER-targeting machinery, were selectively recovered in the PrP screen, indicating that they do not constitute a universal route for the biogenesis of mammalian GPI-APs. Together, these comparative haploid genetic screens demonstrate that, despite their similarity in overall architecture and subcellular localization, GPI-APs follow markedly distinct biosynthetic and trafficking pathways.

Expanding the clinical and molecular characteristics of PIGT-CDG, a disorder of glycosylphosphatidylinositol anchors

PIGT-CDG, an autosomal recessive syndromic intellectual disability disorder of glycosylphosphatidylinositol (GPI) anchors, was recently described in two independent kindreds [Multiple Congenital Anomalies-Hypotonia-Seizures Syndrome 3 (OMIM, #615398)]. PIGT encodes phosphatidylinositol-glycan biosynthesis class T, a subunit of the heteropentameric transamidase complex that facilitates the transfer of GPI to proteins. GPI facilitates attachment (anchoring) of proteins to cell membranes. We describe, at ages 7 and 6 years, two children of non-consanguineous parents; they had hypotonia, severe global developmental delay, and intractable seizures along with endocrine, ophthalmologic, skeletal, hearing, and cardiac anomalies. Exome sequencing revealed that both siblings had compound heterozygous variants in PIGT (NM_015937.5), i.e., c.918dupC, a novel duplication leading to a frameshift, and c.1342C > T encoding a previously described missense variant. Flow cytometry studies showed decreased surface expression of GPI-anchored proteins on granulocytes, consistent with findings in previous cases. These siblings further delineate the clinical spectrum of PIGT-CDG, reemphasize the neuro-ophthalmologic presentation, clarify the endocrine features, and add hypermobility, low CSF albumin quotient, and hearing loss to the phenotypic spectrum. Our results emphasize that GPI anchor-related congenital disorders of glycosylation (CDGs) should be considered in subjects with early onset severe seizure disorders and dysmorphic facial features, even in the presence of a normal carbohydrate-deficient transferrin pattern and N-glycan profiling. Currently available screening for CDGs will not reliably detect this family of disorders, and our case reaffirms that the use of flow cytometry and genetic testing is essential for diagnosis in this group of disorders.

Glycan variation and evolution in the eukaryotes

In this review, we document the evolution of common glycan structures in the eukaryotes, and illustrate the considerable variety of oligosaccharides existing in these organisms. We focus on the families of N- and O-glycans, glycosphingolipids, glycosaminoglycans, glycosylphosphatidylinositol (GPI) anchors, sialic acids (Sias), and cytoplasmic and nuclear glycans. We also outline similar and divergent aspects of the glycans during evolution within the groups, which include inter- and intraspecies differences, molecular mimicry, viral glycosylation adaptations, glycosyltransferase specificity relating to function, and the natural dynamism powering these events. Finally, we present an overview of the patterns of glycosylation found within the groups comprising the Eukaryota, namely the Deuterostomia, Fungi, Viridiplantae, Nematoda, and Arthropoda.

The Repellent DEET Potentiates Carbamate Effects via Insect Muscarinic Receptor Interactions: An Alternative Strategy to Control Insect Vector-Borne Diseases

Insect vector-borne diseases remain one of the principal causes of human mortality. In addition to conventional measures of insect control, repellents continue to be the mainstay for personal protection. Because of the increasing pyrethroid-resistant mosquito populations, alternative strategies to reconstitute pyrethroid repellency and knock-down effects have been proposed by mixing the repellent DEET (N,N-Diethyl-3-methylbenzamide) with non-pyrethroid insecticide to better control resistant insect vector-borne diseases. By using electrophysiological, biochemichal, in vivo toxicological techniques together with calcium imaging, binding studies and in silico docking, we have shown that DEET, at low concentrations, interacts with high affinity with insect M1/M3 mAChR allosteric site potentiating agonist effects on mAChRs coupled to phospholipase C second messenger pathway. This increases the anticholinesterase activity of the carbamate propoxur through calcium-dependent regulation of acetylcholinesterase. At high concentrations, DEET interacts with low affinity on distinct M1/M3 mAChR site, counteracting the potentiation. Similar dose-dependent dual effects of DEET have also been observed at synaptic mAChR level. Additionally, binding and in silico docking studies performed on human M1 and M3 mAChR subtypes indicate that DEET only displays a low affinity antagonist profile on these M1/M3 mAChRs. These results reveal a selective high affinity positive allosteric site for DEET in insect mAChRs. Finally, bioassays conducted on Aedes aegypti confirm the synergistic interaction between DEET and propoxur observed in vitro, resulting in a higher mortality of mosquitoes. Our findings reveal an unusual allosterically potentiating action of the repellent DEET, which involves a selective site in insect. These results open exciting research areas in public health particularly in the control of the pyrethroid-resistant insect-vector borne diseases. Mixing low doses of DEET and a non-pyrethroid insecticide will lead to improvement in the efficiency treatments thus reducing both the concentration of active ingredients and side effects for non-target organisms. The discovery of this insect specific site may pave the way for the development of new strategies essential in the management of chemical use against resistant mosquitoes.

Collagenase as a useful tool for the analysis of plant cellular peripheries

A technique for the selective loosening of the cell wall structure and the isolation of proteins permanently knotted in the cell walls was elaborated. Following treatment with collagenase, some proteins, such as calreticulin (CRT) and auxin binding protein 1 (ABP1) were released from purified cell walls, most probably through destruction of respective interacting proteins. The results were confirmed by the immunolocalization of the ABP1 and CRT with confocal and electron microscopy. On the other hand, potential substrates of collagenase, among them annexin 1 have been recognized. Mass spectra of annexin 1 obtained after collagenase digestion and results from analysis of potential cleavage sites suggested that the mechanism of enzyme cleavage might not depend on the amino acid sequence. Summarizing, collagenase was found to be a very useful tool for exploring molecules involved in the functioning of cellular peripheries.

Glycosyl phosphatidylinositol anchor biosynthesis is essential for maintaining epithelial integrity during Caenorhabditis elegans embryogenesis

Glycosylphosphatidylinositol (GPI) is a post-translational modification resulting in the attachment of modified proteins to the outer leaflet of the plasma membrane. Tissue culture experiments have shown GPI-anchored proteins (GPI-APs) to be targeted to the apical membrane of epithelial cells. However, the in vivo importance of this targeting has not been investigated since null mutations in GPI biosynthesis enzymes in mice result in very early embryonic lethality. Missense mutations in the human GPI biosynthesis enzyme pigv are associated with a multiple congenital malformation syndrome with a high frequency of Hirschsprung disease and renal anomalies. However, it is currently unknown how these phenotypes are linked to PIGV function. Here, we identify a temperature-sensitive hypomorphic allele of PIGV in Caenorhabditis elegans, pigv-1(qm34), enabling us to study the role of GPI-APs in development. At the restrictive temperature we found a 75% reduction in GPI-APs at the surface of embryonic cells. Consequently, ~80% of pigv-1(qm34) embryos arrested development during the elongation phase of morphogenesis, exhibiting internal cysts and/or surface ruptures. Closer examination of the defects revealed them all to be the result of breaches in epithelial tissues: cysts formed in the intestine and excretory canal, and ruptures occurred through epidermal cells, suggesting weakening of the epithelial membrane or membrane-cortex connection. Knockdown of piga-1, another GPI biosynthesis enzymes resulted in similar phenotypes. Importantly, fortifying the link between the apical membrane and actin cortex by overexpression of the ezrin/radixin/moesin ortholog ERM-1, significantly rescued cyst formation and ruptures in the pigv-1(qm34) mutant. In conclusion, we discovered GPI-APs play a critical role in maintaining the integrity of the epithelial tissues, allowing them to withstand the pressure and stresses of morphogenesis. Our findings may help to explain some of the phenotypes observed in human syndromes associated with pigv mutations.

Cell surface proteins, such as receptors, either integrate into the plasma membrane through a transmembrane domain or are tethered to it by an accessory glycosylated phospholipid (GPI) anchor that is attached to them after they are made. The GPI-anchor biosynthesis pathway is highly conserved from yeast to humans and null mutations in any of the key enzymes are lethal at early developmental stages. Point mutations in several genes encoding for GPI-anchor biosynthesis enzymes have been linked to human disease. Specifically, mutations in PIGV are associated with multiple congenital malformations, including renal and anorectal malformation and mental retardation. It is currently not known how the mutations in PIGV lead to these diseases. Here we describe a point mutation in the PIGV ortholog of the nematode Caenorhabditis elegans, pigv-1, which is found to cause a high degree of embryonic lethality. We documented a substantial reduction in the level of GPI-anchors in the mutant. Importantly, following its development using 4D microscopy and employing tissue-specific rescue, we identified loss of epithelial integrity as the primary cause of developmental arrest. Our results highlight the importance of GPI-anchored proteins for epithelial integrity in vivo and suggest a possible etiology for human diseases associated with PIGV mutations.

The GPI-anchoring of PrP: implications in sorting and pathogenesis

The cellular prion protein (PrP(C)) is an N-glycosylated GPI-anchored protein usually present in lipid rafts with numerous putative functions. When it changes its conformation to a pathological isoform (then referred to as PrP(Sc)), it is an essential part of the prion, the agent causing fatal and transmissible neurodegenerative prion diseases. There is growing evidence that toxicity and neuronal damage on the one hand and propagation/infectivity on the other hand are two distinct processes of the disease and that the GPI-anchor attachment of PrP(C) and PrP(Sc) plays an important role in protein localization and in neurotoxicity. Here we review how the signal sequence of the GPI-anchor matters in PrP(C) localization, how an altered cellular localization of PrP(C) or differences in GPI-anchor composition can affect prion infection, and we discuss through which mechanisms changes on the anchorage of PrP(C) can modify the disease process.

Computational survey of sequence specificity for protein terminal tags covering nine organisms and its application to protein identification

In 1998, Wilkins et al. (J. Mol. Biol. 1998, 278, 599-608) reported high specificity in terminal regions (terminal tags) of 15 519 proteins from five organisms and proposed a methodology for identifying proteins by terminal tags. However, their examined sequence data were not based on complete genome sequences. Here, we examined current proteome data (217 249 entries from UniProt 2013_6 complete/reference proteome for nine organisms including human) in terms of the specificity of terminal tags and their computational annotation. One example from the results indicated that the specificity of N-terminal tags plateaued at 28% at a length of six residues for human; even when using both N- and C-terminal tags, specificity was merely 66%. In order to determine the cause of these low specificities, the annotation of proteins sharing terminal tags with other proteins was examined. The results suggested that a large majority were phylogenetically or functionally related, whereas nonrelated proteins sharing terminal tags made up less than 1% of human proteome data. On the basis of these findings, we constructed the terminal tag sequence database ProteinCarta (http://ms3d.jp/software/proteincarta/), which includes all terminal tags of proteomes from the nine organisms analyzed here, in order to confirm the specificity of terminal tags and to identify the parent protein.

Chemical biology approaches to designing defined carbohydrate vaccines

Carbohydrate antigens have shown promise as important targets for developing effective vaccines and pathogen detection strategies. Modifying purified microbial glycans through synthetic routes or completely synthesizing antigenic motifs are attractive options to advance carbohydrate vaccine development. However, limited knowledge on structure-property correlates hampers the discovery of immunoprotective carbohydrate epitopes. Recent advancements in tools for glycan modification, high-throughput screening of biological samples, and 3D structural analysis may facilitate antigen discovery process. This review focuses on advances that accelerate carbohydrate-based vaccine development and various technologies that are driving these efforts. Herein we provide a critical overview of approaches and resources available for rational design of better carbohydrate antigens. Structurally defined and fully synthetic oligosaccharides, designed based on molecular understanding of antigen-antibody interactions, offer a promising alternative for developing future carbohydrate vaccines.

Neurogenetic Aspects of Hyperphosphatasia in Mabry Syndrome

An autosomal recessive syndrome of hyperphosphatasia (elevated circulating alkaline phosphatase (AP), seizures and neurologic deficits) was first described by Mabry and colleagues in 1970. Over the ensuing four decades, few cases were reported. In 2010, however, new families were identified and the syndromic nature of the disorder confirmed. Shortly thereafter, next generation sequencing was used to characterize causative defects in the glycosyl phosphatidylinositol (GPI) biosynthetic pathway, based partly on our understanding of how AP is anchored by GPI to the plasma membrane. Whether the seizures and cognitive defects seen in Mabry syndrome patients are attributable in part to the constant hyperphosphatasia is not known, as there are more than 250 other proteins dependent on GPI for their anchoring to the plasma membrane. However, Mabry syndrome may provide a new window on AP function in growth and development.

Insights into the apoptotic death of immune cells in sepsis

Sepsis with subsequent multiple-organ dysfunction is a distinct systemic inflammatory response to concealed or obvious infection, and it is a leading cause of death in intensive care units. Thus, one of the key goals in critical care medicine is to develop novel therapeutic strategies that will affect favorably on outcome of septic patients. In addition to systemic response to infection, apoptosis is implicated to be an important mechanism of the death of immune cells, including neutrophils, macrophages, T lymphocytes, and dendritic cells, and it is usually followed by the development of multiple-organ failure in sepsis. The implication of apoptosis of immune cells is now highlighted by multiple studies that demonstrate that prevention of cell apoptosis can improve survival in relevant animal models of severe sepsis. In this review, we focus on major apoptotic death pathways and molecular mechanisms that regulate apoptosis of different immune cells, and advances in these areas that may be translated into more promising therapies for the prevention and treatment of severe sepsis.

An overview of inborn errors of complex lipid biosynthesis and remodelling

In a review published in 2012, we delineated 14 inborn errors of metabolism (IEM) related to defects in biosynthesis of complex lipids, particularly phospholipids and sphingolipids (Lamari et al 2013). Given the numerous roles played by these molecules in membrane integrity, cell structure and function, this group of diseases is rapidly expanding as predicted. Almost 40 new diseases related to genetic defects in enzymes involved in the biosynthesis and remodelling of phospholipids, sphingolipids and complex fatty acids are now reported. While the clinical phenotype associated with these defects is currently difficult to outline, with only a few patients identified to date, it appears that all organs and systems may be affected - central and peripheral nervous system, eye, muscle, skin, bone, liver, immune system, etc. This chapter presents an introductive overview of this new group of IEM. More broadly, this special issue provides an update on other IEM involving complex lipids, namely dolichol and isoprenoids, glycolipids and congenital disorders of glycosylation, very long chain fatty acids and plasmalogens. Likewise, more than 100 IEM may actually lead to primary or secondary defects of complex lipids synthesis and remodelling. Because of the implication of several cellular compartments, this new group of disorders affecting the synthesis and remodelling of complex molecules challenges our current classification of IEM still largely based on cellular organelles--i.e. mitochondrial, lysosomal, peroxisomal disorders. While most of these new disorders have been identified by next generation sequencing, we wish to emphasize the promising role of lipidomics in deciphering their pathophysiology and identifying therapeutic targets.

Chemoselective per-O-trimethylsilylation and homogeneous N-functionalisation of amino sugars

HomogeneousN-functionalisation of amino sugars can be achievedviaefficient CH₃CN-promoted hexamethyldisilazane per-O-trimethylsilylation.

Emerging roles for microtubules in angiosperm pollen tube growth highlight new research cues

In plants, actin filaments have an important role in organelle movement and cytoplasmic streaming. Otherwise microtubules (MTs) have a role in restricting organelles to specific areas of the cell and in maintaining organelle morphology. In somatic plant cells, MTs also participate in cell division and morphogenesis, allowing cells to take their definitive shape in order to perform specific functions. In the latter case, MTs influence assembly of the cell wall, controlling the delivery of enzymes involved in cellulose synthesis and of wall modulation material to the proper sites. In angiosperm pollen tubes, organelle movement is generally attributed to the acto-myosin system, the main role of which is in distributing organelles in the cytoplasm and in carrying secretory vesicles to the apex for polarized growth. Recent data on membrane trafficking suggests a role of MTs in fine delivery and repositioning of vesicles to sustain pollen tube growth. This review examines the role of MTs in secretion and endocytosis, highlighting new research cues regarding cell wall construction and pollen tube-pistil crosstalk, that help unravel the role of MTs in polarized growth.

C-terminomics: Targeted analysis of natural and posttranslationally modified protein and peptide C-termini

The C-terminus (where C is carboxyl) of a protein can serve as a recognition signature for a variety of biological processes, including protein trafficking and protein complex formation. Hence, the identity of the in vivo protein C-termini provides valuable information about biological processes. Analysis of protein C-termini is also crucial for the study of C-terminal PTMs, particularly for monitoring proteolytic processing by endopeptidases and carboxypeptidases. Although technical difficulties have limited the study of C-termini, a range of technologies have been proposed in the last couple of years. Here, we review the current proteomics technologies for C-terminal analysis, with a focus on the biological information that can be derived from C-terminomics studies.

Mannose metabolism: more than meets the eye

Mannose is a simple sugar with a complex life. It is a welcome therapy for genetic and acquired human diseases, but it kills honeybees and blinds baby mice. It could cause diabetic complications. Mannose chemistry, metabolism, and metabolomics in cells, tissues and mammals can help explain these multiple systemic effects. Mannose has good, bad or ugly outcomes depending on its steady state levels and metabolic flux. This review describes the role of mannose at cellular level and its impact on organisms.

Microwave-assisted one-pot synthesis of 1,6-anhydrosugars and orthogonally protected thioglycosides

Living organisms employ glycans as recognition elements because of their large structural information density. Well-defined sugar structures are needed to fully understand and take advantage of glycan functions, but sufficient quantities of these compounds cannot be readily obtained from natural sources and have to be synthesized. Among the bottlenecks in the chemical synthesis of complex glycans is the preparation of suitably protected monosaccharide building blocks. Thus, easy, rapid, and efficient methods for building-block acquisition are desirable. Herein, we describe routes directly starting from the free sugars toward notable monosaccharide derivatives through microwave-assisted one-pot synthesis. The procedure followed the in situ generation of per-O-trimethylsilylated monosaccharide intermediates, which provided 1,6-anhydrosugars or thioglycosides upon treatment with either trimethylsilyl trifluoromethanesulfonate or trimethyl(4-methylphenylthio)silane and ZnI2, respectively, under microwave irradiation. We successfully extended the methodology to regioselective protecting group installation and manipulation toward a number of thioglucosides and the glycosylation of persilylated derivatives, all of which were conducted in a single vessel. These developed approaches open the possibility for generating arrays of suitably protected building blocks for oligosaccharide assembly in a short period with minimal number of purification stages.

Phosphatidylethanolamine deficiency disrupts α-synuclein homeostasis in yeast and worm models of Parkinson disease

Phosphatidylserine decarboxylase, which is embedded in the inner mitochondrial membrane, synthesizes phosphatidylethanolamine (PE) and, in some cells, synthesizes the majority of this important phospholipid. Normal levels of PE can decline with age in the brain. Here we used yeast and worms to test the hypothesis that low levels of PE alter the homeostasis of the Parkinson disease-associated protein α-synuclein (α-syn). In yeast, low levels of PE in the phosphatidylserine decarboxylase deletion mutant (psd1Δ) cause decreased respiration, endoplasmic reticulum (ER) stress, a defect in the trafficking of the uracil permease, α-syn accumulation and foci, and a slow growth phenotype. Supplemental ethanolamine (ETA), which can be converted to PE via the Kennedy pathway enzymes in the ER, had no effect on respiration, whereas, in contrast, this metabolite partially eliminated ER stress, decreased α-syn foci formation, and restored growth close to that of wild-type cells. In Caenorhabditis elegans, RNAi depletion of phosphatidylserine decarboxylase in dopaminergic neurons expressing α-syn accelerates neurodegeneration, which supplemental ETA rescues. ETA fails to rescue this degeneration in worms that undergo double RNAi depletion of phosphatidylserine decarboxylase (psd-1) and choline/ETA phosphotransferase (cept-1), which encodes the last enzyme in the CDP-ETA Kennedy pathway. This finding suggests that ETA exerts its protective effect by boosting PE through the Kennedy pathway. Overall, a low level of PE causes ER stress, disrupts vesicle trafficking, and causes α-syn to accumulate; such cells likely die from a combination of ER stress and excessive accumulation of α-syn.

Extension and validation of the GROMOS 53A6(GLYC) parameter set for glycoproteins

An extension of the GROMOS 53A6GLYC force field for carbohydrates to encompass glycoprotein linkages is presented. The set includes new atomic charges and incorporates adequate torsional potential parameters for N-, S-, C-, P-, and O-glycosydic linkages, offering compatibility with the GROMOS force field family for proteins. Validation included the description of glycosydic linkage geometries between amino acid and monosaccharide residues, comparison of NMR-derived protein-carbohydrate and carbohydrate-carbohydrate nuclear overhauser effect (NOE) signals for glycoproteins and the effects of glycosylation on protein flexibility and dynamics.

Exploring developmental and physiological functions of fatty acid and lipid variants through worm and fly genetics

Lipids are more than biomolecules for energy storage and membrane structure. With ample structural variation, lipids critically participate in nearly all aspects of cellular function. Lipid homeostasis and metabolism are closely related to major human diseases and health problems. However, lipid functional studies have been significantly underdeveloped, partly because of the difficulty in applying genetics and common molecular approaches to tackle the complexity associated with lipid biosynthesis, metabolism, and function. In the past decade, a number of laboratories began to analyze the roles of lipid metabolism in development and other physiological functions using animal models and combining genetics, genomics, and biochemical approaches. These pioneering efforts have not only provided valuable insights regarding lipid functions in vivo but have also established feasible methodology for future studies. Here, we review a subset of these studies using Caenorhabditis elegans and Drosophila melanogaster.

Residual cancer lymphocytes in patients with chronic lymphocytic leukemia after therapy show increased expression of surface antigen CD52 detected using quantitative fluorescence cytometry

BACKGROUND

Rituximab and alemtuzumab, mAbs used in recent years to treat CLL, are directed against antigens CD20 and CD52. CD20 is not highly expressed by CLL tumor cells, and rituximab does not have significant effectiveness in CLL unless combined with chemotherapy. Alemtuzumab targets CD52, which is much more highly expressed, and is currently the most effective agent used alone for CLL. Variability in expression of both antigens among these patients might be related to different individual therapeutic responses to mAb therapy.

PATIENTS AND METHODS

A total 95 patients diagnosed with CLL and/or SLL were divided into 4 groups: (1) untreated; (2) in complete or partial remission; (3) disease in progression; and (4) diagnosed with SLL. Flow cytometry of peripheral blood cells included gating of the CD5(+)CD19(+) tumor population, within which mean fluorescence intensity of fluorescein isothiocyanate (FITC) conjugated with anti-CD20 or anti-CD52 antibody was measured. The resulting expression of the 2 antigens was deduced from the calibration curve using Quantum FITC particles.

RESULTS

Expression of CD20 showed no significant differences among the 4 groups of patients. However, significantly greater expression of surface antigen CD52 was recorded in patient group 2 in complete or partial remission (P < .001).

CONCLUSION

The residual population of CLL cells after therapy is characterized by increased surface detection of CD52. Although the exact cause of this phenomenon is unknown, our results provide a basis to consider the potential for CLL consolidation therapy using alemtuzumab.

Molecular dynamics simulations of the auxin-binding protein 1 in complex with indole-3-acetic acid and naphthalen-1-acetic acid

Auxin-binding protein 1 (ABP1) is suggested to be an auxin receptor which plays an important role in several processes in green plants. Maize ABP1 was simulated with the natural auxin indole-3-acetic acid (IAA) and the synthetic analog naphthalen-1-acetic acid (NAA), to elucidate the role of the KDEL sequence and the helix at the C-terminus. The KDEL sequence weakens the intermolecular interactions between the monomers but stabilizes the C-terminal helix. Conformational changes at the C-terminus occur within the KDEL sequence and are influenced by the binding of the simulated ligands. This observation helps to explain experimental findings on ABP1 interactions with antibodies that are modulated by the presence of auxin, and supports the hypothesis that ABP1 acts as an auxin receptor. Stable hydrogen bonds between the monomers are formed between Glu40 and Glu62, Arg10 and Thr97, Lys39, and Glu62 in all simulations. The amino acids Ile22, Leu25, Trp44, Pro55, Ile130, and Phe149 are located in the binding pocket and are involved in hydrophobic interactions with the ring system of the ligand. Trp151 is stably involved in a face to end interaction with the ligand. The calculated free energy of binding using the linear interaction energy approach showed a higher binding affinity for NAA as compared to IAA. Our simulations confirm the asymmetric behavior of the two monomers, the stronger interaction of NAA than IAA and offers insight into the possible mechanism of ABP1 as an auxin receptor.

Bitter-sweet symphony: glycan-lectin interactions in virus biology

Glycans are carbohydrate modifications typically found on proteins or lipids, and can act as ligands for glycan-binding proteins called lectins. Glycans and lectins play crucial roles in the function of cells and organs, and in the immune system of animals and humans. Viral pathogens use glycans and lectins that are encoded by their own or the host genome for their replication and spread. Recent advances in glycobiological research indicate that glycans and lectins mediate key interactions at the virus-host interface, controlling viral spread and/or activation of the immune system. This review reflects on glycan-lectin interactions in the context of viral infection and antiviral immunity. A short introduction illustrates the nature of glycans and lectins, and conveys the basic principles of their interactions. Subsequently, examples are discussed highlighting specific glycan-lectin interactions and how they affect the progress of viral infections, either benefiting the host or the virus. Moreover, glycan and lectin variability and their potential biological consequences are discussed. Finally, the review outlines how recent advances in the glycan-lectin field might be transformed into promising new approaches to antiviral therapy.

Hooked on fat: the role of lipid synthesis in cancer metabolism and tumour development

An increased rate of lipid synthesis in cancerous tissues has long been recognised as an important aspect of the rewired metabolism of transformed cells. However, the contribution of lipids to cellular transformation, tumour development and tumour progression, as well as their potential role in facilitating the spread of cancerous cells to secondary sites, are not yet fully understood. In this article, we review the recent findings that support the importance of lipid synthesis and metabolism in tumorigenesis. Specifically, we explore the role of aberrant lipid biosynthesis in cancer cell migration and invasion, and in the induction of tumour angiogenesis. These processes are crucial for the dissemination of tumour cells and formation of metastases, which constitute the main cause of cancer mortality.

Versatility of a glycosylphosphatidylinositol fragment in forming highly ordered polymorphs

Glycosylphosphatidylinositols (GPIs) are often attributed with the ability to associate with the organized membrane microdomains. GPI fragment 1 forms a highly ordered subgel-phase structure characterized by ordering of both headgroups and alkyl chains in thin layers. While investigating the driving forces behind the formation of these ordered monolayers, we have studied polymorphism of 1 under different conditions employing surface-sensitive X-ray diffraction methods. Three distinct polymorphs of 1 (I, II, and III) were identified and characterized by grazing incidence X-ray diffraction. Polymorphs II (a condensed monolayer structure) and III (highly ordered subgel phase) coexist on an 8 M urea solution subphase allowing for a detailed thermodynamic and kinetic analysis of the processes leading to the formation of these polymorphs. They are enantiotropic and can be directly interconverted by changes in temperature or lateral surface pressure. As a consequence, polymorph III nuclei of critical size (or larger) could be formed by density fluctuations in a multicomponent system, and they could continue to exist for a period of time even under conditions that would normally not allow for the nucleation of polymorph III. The processes described here could also lead to the formation of patches of highly ordered structures in a disordered environment of a cell membrane suggesting that GPIs may play a role in the formation of such domains.

Transamidase subunit GAA1/GPAA1 is a M28 family metallo-peptide-synthetase that catalyzes the peptide bond formation between the substrate protein's omega-site and the GPI lipid anchor's phosphoethanolamine

The transamidase subunit GAA1/GPAA1 is predicted to be the enzyme that catalyzes the attachment of the glycosylphosphatidyl (GPI) lipid anchor to the carbonyl intermediate of the substrate protein at the ω-site. Its ~300-amino acid residue lumenal domain is a M28 family metallo-peptide-synthetase with an α/β hydrolase fold, including a central 8-strand β-sheet and a single metal (most likely zinc) ion coordinated by 3 conserved polar residues. Phosphoethanolamine is used as an adaptor to make the non-peptide GPI lipid anchor look chemically similar to the N terminus of a peptide.

Construction of a highly active xylanase displaying oleaginous yeast: comparison of anchoring systems

Three Yarrowia lipolytica cell wall proteins (YlPir, YlCWP1 and YlCBM) were evaluated for their ability to display the xylanase TxXYN from Thermobacillus xylanilyticus on the cell surface of Y. lipolytica. The fusion proteins were produced in Y. lipolytica JMY1212, a strain engineered for mono-copy chromosomal insertion, and enabling accurate comparison of anchoring systems. The construction using YlPir enabled cell bound xylanase activity to be maximised (71.6 U/g). Although 48% of the activity was released in the supernatant, probably due to proteolysis at the fusion zone, this system is three times more efficient for the anchoring of TxXYN than the YlCWP1 system formerly developed for Y. lipolytica. As far as we know it represents the best displayed xylanase activity ever published. It could be an attractive alternative anchoring system to display enzymes in Y. lipolytica.

The lipid raft-bound alkaline phosphatase activity increases and the level of transcripts remains unaffected in liver of merosin-deficient LAMA2dy mouse

Alkaline phosphatase (AP) and other proteins add glycosylphosphatidylinositol (GPI) before addressing to raft domains of the cell membrane. Our previous report showing an increased density of lipid rafts in muscle of dystrophic Lama2dy mice prompted us to compare livers of normal (NL) and dystrophic mice (DL) for their levels of rafts. With this aim, hepatic rafts were isolated as Triton X-100 resistant membranes, and identified by their abundance of flotillin-2, alkaline phosphatase (AP) and other raft markers. The comparable abundance of cholesterol and flotillin-2 in rafts of NL and DL contrasted with the double AP activity both in rafts of DL and whole DL. The AP mRNA level was the same in NL and DL. Sedimentation analysis profiles revealed AP activity of NL distributed between dimeric (dAP) and monomeric AP (mAP), whose proportions and lectin-binding extent changed in DL. The increased AP activity and changed AP glycosylation in DL, the prevalence of mAP in NL and the enhanced stability of dAP in DL demonstrated the critical role that glycosylation and oligomerization play for AP catalysis. The higher AP activity of DL probably arises from dystrophy-associated changes in glycosyl transferases, which alter AP glycosylation and subunit folding with profitable effects for AP stability and catalysis.