SOD1-related ALS with anticipation in a large family from Martinique

Amyotrophic Lateral Sclerosis (ALS) is a rare neurological disorder that causes degeneration of upper and lower motor neurons and their axons. ALS is mostly sporadic, but there are familial forms. In more than half of the familial forms, a pathogenic variant is found in one of the following genes: C9ORF72, SOD1, TDP-43, FUS, and VCP. SOD1 is the 2nd most common gene involved in genetic forms of ALS. Genotype-phenotype relationships are occasionally established in genetic forms of ALS associated with SOD1 mutations pathogenic variants. The c.281G > T (p.[G93V]) variant in SOD1 is associated with a rarely described and unexplained anticipation phenomenon. We report a large family from Martinique in whom ALS is associated with a c.281G > T (p.[G93V]) pathogenic variant in SOD1 and a statistically suggested anticipation. A whole-exome study and detection of CNVs (CoDESeq) from 3 affected members of this family revealed the presence of variants of uncertain signification (VUS) in other ALS genes. VUS in DCTN1 and NEFH were present in patients of the 2nd generation, and CNVs involving UBQLN2 and C21orf2 were found in the youngest case of the family.

Proteomic characterization of phagosomal membrane microdomains during phagolysosome biogenesis and evolution

After their formation at the cell surface, phagosomes become fully functional through a complex maturation process involving sequential interactions with various intracellular organelles. In the last decade, series of data indicated that some of the phagosome functional properties occur in specialized membrane microdomains. The molecules associated with membrane microdomains, as well as the organization of these structures during phagolysosome biogenesis are largely unknown. In this study, we combined proteomics and bioinformatics analyses to characterize the dynamic association of proteins to maturing phagosomes. Our data indicate that groups of proteins shuffle from detergent-soluble to detergent-resistant membrane microdomains during maturation, supporting a model in which the modulation of the phagosome functional properties involves an important reorganization of the phagosome proteome by the coordinated spatial segregation of proteins.

Quantitative proteomics reveals that only a subset of the endoplasmic reticulum contributes to the phagosome

Phagosomes, by killing and degrading pathogens for antigen presentation, are organelles implicated in key aspects of innate and adaptive immunity. Although it has been well established that phagosomes consist of membranes from the plasma membrane, endosomes, and lysosomes, the notion that the endoplasmic reticulum (ER) membrane could play an important role in the formation of the phagosome is debated. However, a method to accurately estimate the contribution of potential source organelles and contaminants to the phagosome proteome has been lacking. Herein, we have developed a proteomic approach for objectively quantifying the contribution of various organelles to the early and late phagosomes by comparing these fractions to their total membrane and postnuclear supernatant of origin in the J774A.1 murine macrophage cell line. Using quantitative label-free mass spectrometry, the abundance of peptides corresponding to hundreds of proteins was estimated and attributed to one of five organelles (e.g. plasma membrane, endosomes/lysosomes, ER, Golgi, and mitochondria). These data in combination with a stable isotope labeling in cell culture method designed to detect potential contaminant sources revealed that the ER is part of the phagosomal membrane and contributes ≈ 20% of the early phagosome proteome. In addition, only a subset of ER proteins is recruited to the phagosome, suggesting that a specific subdomain(s) of the ER might be involved in phagocytosis. Western blotting and immunofluorescence substantially validated this conclusion; we were able to demonstrate that the fraction of the ER in which the ER marker GFP-KDEL accumulates is excluded from the phagosomes, whereas that containing the mVenus-Syntaxin 18 is recruited. These results highlight promising new avenues for the description of the pathogenic mechanisms used by Leishmania, Brucella, and Legionella spp., which thrive in ER-rich phagosomes.

The endosomal proteome of macrophage and dendritic cells

The essential roles of the endovacuolar system in health and disease call for the development of new tools allowing a better understanding of the complex molecular machinery involved in endocytic processes. We took advantage of the floating properties of small latex beads (sLB) on a discontinuous sucrose gradient to isolate highly purified endosomes following internalization of small latex beads in J774 macrophages and bone marrow-derived dendritic cells (DC). We particularly focused on the isolation of macrophages early endosomes and late endosomes/lysosomes (LE/LYS) as well as the isolation of LE/LYS from immature and lipopolysaccharide-activated (mature) DC. We subsequently performed a comparative analysis of their respective protein contents by MS. As expected, proteins already known to localize to the early endosomes were enriched in the earliest fraction of J774 endosomes, while proteins known to accumulate later in the process, such as hydrolases, were significantly enriched in the LE/LYS preparations. We next compared the LE/LYS protein contents of immature DC and mature DC, which are known to undergo massive reorganization leading to potent immune activation. The differences between the protein contents of endocytic organelles from macrophages and DC were underlined by focusing on previously poorly characterized biochemical pathways, which could have an unexpected but important role in the endosomal functions of these highly relevant immune cell types.

Modulation of the phagosome proteome by interferon-gamma

Macrophages are immune cells that function in the clearance of infectious particles. This process involves the engulfment of microbes into phagosomes where these particles are lysed and degraded. In the current study, we used a large scale quantitative proteomics approach to analyze the changes in protein abundance induced on phagosomes by interferon-gamma (IFN-gamma), an inflammatory cytokine that activates macrophages. Our analysis identified 167 IFN-gamma-modulated proteins on phagosomes of which more than 90% were up-regulated. The list of phagosomal proteins regulated by IFN-gamma includes proteins expected to alter phagosome maturation, enhance microbe degradation, trigger the macrophage immune response, and promote antigen loading on major histocompatibility complex (MHC) class I molecules. A dynamic analysis of IFN-gamma-sensitive proteins by Western blot indicated that newly formed phagosomes display a delayed proteolytic activity coupled to an increased recruitment of the MHC class I peptide-loading complex. These phagosomal conditions may favor antigen presentation by MHC class I molecules on IFN-gamma-activated macrophages.

Remodeling of endosomes during lysosome biogenesis involves 'kiss and run' fusion events regulated by rab5

The small GTPase rab5 has been shown to play key roles in the function of both endocytic and phagocytic organelles. Although these organelles share several additional common features, different processes have been proposed to explain their biogenesis. In the present study, we provide evidence that lysosome biogenesis involves mechanisms similar to those previously described for the formation of phagolysosomes. Transient interactions ('kiss and run') between endocytic organelles are shown to occur during lysosome biogenesis. These interactions are regulated initially by the GTPase activity of rab5, as demonstrated by the loss of size-selective fusion between endosomes in cells expressing a GTPase-deficient mutant of rab5. Endocytic compartments in these cells sequentially display properties of early and late endosomes. However, the formation of lysosomes and the sorting of endocytic solute materials to small electron dense vacuoles are not affected by the rab5 mutation. Together, our results indicate that endosome maturation occurs during the early part of lysosome biogenesis. This process involves transient fusion events regulated, in part, by the small GTPase rab5.

Endoplasmic reticulum-mediated phagocytosis is a mechanism of entry into macrophages

Phagocytosis is a key aspect of our innate ability to fight infectious diseases. In this study, we have found that fusion of the endoplasmic reticulum (ER) with the macrophage plasmalemma, underneath phagocytic cups, is a source of membrane for phagosome formation in macrophages. Successive waves of ER become associated with maturing phagosomes during phagolysosome biogenesis. Thus, the ER appears to possess unexpectedly pluripotent fusion properties. ER-mediated phagocytosis is regulated in part by phosphatidylinositol 3-kinase and used for the internalization of inert particles and intracellular pathogens, regardless of their final trafficking in the host. In neutrophils, where pathogens are rapidly killed, the ER is not used as a major source of membrane for phagocytosis. We propose that intracellular pathogens have evolved to adapt and exploit ER-mediated phagocytosis to avoid destruction in host cells.

Flotillin-1-enriched lipid raft domains accumulate on maturing phagosomes

Flotillin-1 was recently shown to be enriched on detergent-resistant domains of the plasma membrane called lipid rafts. These rafts, enriched in sphingolipids and cholesterol, sequester certain proteins while excluding others. Lipid rafts have been implicated in numerous cellular processes including signal transduction, membrane trafficking, and molecular sorting. In this study, we demonstrate both morphologically and biochemically that lipid rafts are present on phagosomes. These structures are enriched in flotillin-1 and devoid of the main phagosomes membrane protein lysosomal-associated membrane protein (LAMP1). The flotillin-1 present on phagosomes does not originate from the plasma membrane during phagocytosis but accumulates gradually on maturing phagosomes. Treatment with bafilomycin A1, a compound that inhibits the proton pump ATPase and prevents the fusion of phagosomes with late endocytic organelles, prevents the acquisition of flotillin-1 by phagosomes, indicating that this protein might be recruited on phagosomes from endosomal organelles. A proteomic characterization of the lipid rafts of phagosomes indicates that actin, the alpha- and beta-subunits of heterotrimeric G proteins, as well as subunits of the proton pump V-ATPase are among the constituents of these domains. Remarkably, the intracellular parasite Leishmania donovani can actively inhibit the acquisition of flotillin-1-enriched lipid rafts by phagosomes and the maturation of these organelles. These results indicate that specialized functions required for phagolysosome biogenesis may occur at focal points on the phagosome membrane, and therefore represent a potential target of intracellular pathogens.

The phagosome proteome: insight into phagosome functions

Phagosomes are key organelles for the innate ability of macrophages to participate in tissue remodeling, clear apoptotic cells, and restrict the spread of intracellular pathogens. To understand the functions of phagosomes, we initiated the systematic identification of their proteins. Using a proteomic approach, we identified >140 proteins associated with latex bead-containing phagosomes. Among these were hydrolases, proton pump ATPase subunits, and proteins of the fusion machinery, validating our approach. A series of unexpected proteins not previously described along the endocytic/phagocytic pathways were also identified, including the apoptotic proteins galectin3, Alix, and TRAIL, the anti-apoptotic protein 14-3-3, the lipid raft-enriched flotillin-1, the anti-microbial molecule lactadherin, and the small GTPase rab14. In addition, 24 spots from which the peptide masses could not be matched to entries in any database potentially represent new phagosomal proteins. The elaboration of a two-dimensional gel database of >160 identified spots allowed us to analyze how phagosome composition is modulated during phagolysosome biogenesis. Remarkably, during this process, hydrolases are not delivered in bulk to phagosomes, but are instead acquired sequentially. The systematic characterization of phagosome proteins provided new insights into phagosome functions and the protein or groups of proteins involved in and regulating these functions.

Rab5 regulates the kiss and run fusion between phagosomes and endosomes and the acquisition of phagosome leishmanicidal properties in RAW 264.7 macrophages

Phagolysosome biogenesis is essential for the killing and degradation of intracellular pathogens. It involves the fusion of phagosomes with various endocytic organelles, a process known to be regulated in part by Rab proteins. We generated RAW 264.7 macrophages expressing an active mutant of Rab5 (Rab5(Q79L)) to determine the role of Rab5 in phagocytosis and phagolysosome biogenesis. Our results indicate that Rab5 stimulates phagocytosis of latex beads but not Fc or C3 receptor-mediated phagocytosis. Rab5 also acts to restrict the complete fusion of phagosomes with endosomes, a phenomenon allowing exchange of solutes from the two compartments without complete intermixing of their membrane (kiss and run). In Rab5(Q79L)-expressing macrophages, uncontrolled fusion events occurred, leading to the appearance of giant phagosomes. These phagosomes could initiate their maturation and acquire LAMP1, but failed to generate the microbicidal conditions needed to kill intracellular parasites. These results identify Rab5 as a key molecule regulating phagosome-endosome fusion and as an essential component in the innate ability of macrophages to restrict the growth of intracellular parasites.

Simple epithelium keratins are required for maintenance of hepatocyte integrity

Keratin 8 (K8)-deficient adult mice develop a severe disease of the gastrointestinal tract characterized mainly by colorectal hyperplasia and inflammation. Given that hepatocytes contain K8/K18 heteropolymers only, this animal model was used to assess the contribution of these simple epithelium keratins to hepatocyte structural and functional integrity. Homozygous mutant (HMZ), heterozygous, and wild-type (WT) mice were examined for hepatocyte structural and metabolic features and their survival to partial hepatectomy. Except for the presence of few necrotic foci, no other tissular or cellular alterations were observed in nonhepatectomized HMZ mouse livers; glycogen and lipid peroxidation levels were essentially normal, but a small reduction in bile flow was observed. In response to a single pentobarbital injection, HMZ mice had longer sleeping times than heterozygous and WT mice. After a two-thirds partial hepatectomy under pentobarbital anesthesia, all HMZ mice died within a few hours, whereas those anesthetized with ether survived for 1 to 2 days. One hour after hepatectomy after pentobarbital anesthesia, many hepatocytes contained erythrocytes and large vacuoles in the cytoplasm, which suggests damage at the plasma membrane level in response to a sudden increase in portal blood flow. In line with these findings, an uptake of trypan blue by HMZ but not WT mouse hepatocytes was observed during a 10 ml/minute perfusion via the portal vein with a dye-supplemented buffer. Subsequent cellular dispersion led to viable WT mouse hepatocytes but largely nonviable HMZ mouse hepatocytes. Better viability was obtained at lower perfusion rates. Partially hepatectomized heterozygous mice developed liver steatosis, a condition that was not associated with a change in K8 content but perhaps linked to the presence of the neo gene. Transgenic HMZ mouse rescue experiments with a full-length K8 gene confirmed that the phenotypic alterations observed in partially hepatectomized HMZ mice were caused by the disruption of the K8 gene. Taken together, these findings demonstrate that simple epithelium keratins are essential for the maintenance of hepatocyte structural and functional integrity.

Peroxisome proliferation and beta-oxidation in Fao and MH1C1 rat hepatoma cells, HepG2 human hepatoblastoma cells and cultured human hepatocytes: effect of ciprofibrate

Human HepG2, rat Fao and MH1C1 hepatoma cell lines have been examined for their response to ciprofibrate, a potent peroxisome proliferator. Changes in the morphological characteristics of peroxisomes, the inductibility of their proliferation and of their beta-oxidation enzymes, palmitoyl-CoA oxidase and bifunctional enzyme, were studied in control and treated cells. In Fao cells, peroxisomes are less numerous and smaller than in rat liver, but they increase in size and number under the effect of ciprofibrate, similarly to those of treated rat liver. The high peroxisome proliferation is accompanied by a strong induction of beta-oxidation enzymes as in vivo. In MH1C1 cells, peroxisomes are seen in irregular clusters in the cytoplasm, small with rounded to tubular forms, suggesting rapid peroxisomal growth. A striking observation is the particularly elongated, worm-like form of many of the peroxisomes. Under the effect of ciprofibrate, the proliferation is low, as is the induction of beta-oxidation enzymes. HepG2 cells contain few, small peroxisomes with a heterogeneity of forms, from spherical to elongated. The only peroxisomal response to ciprofibrate in these cells seemed to be a morphological reorganization. There is little or no induction of beta-oxidation enzymes by ciprofibrate in HepG2 cells, as in cultured human hepatocytes. Therefore, on the one hand, Fao and MH1C1 cells are complementary tools in the investigation of the regulation of the hepatic response to peroxisome proliferators in the rat, on the other hand, HepG2 and Fao cells are useful in the study of the species specificity of the response.

Preparation of a dansylated fibrate, a new fluorescent tool to study peroxisome proliferation. Effect on hepatic-derived cell lines

The synthesis of a dansylated fibrate (DNS-X) has been performed in order to identify the cellular affinity sites of peroxisome proliferators and to establish the subcellular localization of such molecules. DNS-X has been obtained by coupling the dansy1 chloride with the amine resulting from the bezafibrate alkaline hydrolysis. The purified DNS-X has been further characterized by spectrum analysis (UV-Vis, fluorescence, [1H]/[13C]-NMR and mass). At 250 microM and incubated for 48 h with the rat hepatic derived cells (Fao cells), DNS-X stimulates 12-fold the palmitoyl-CoA oxidase, a peroxisome proliferation marker enzyme. This increase is comparable to the one obtained with well known peroxisome proliferators such as bezafibrate or ciprofibrate. The stimulation by DNS-X is specific for the overall molecule since neither the dansyl chloride, the amine, nor the precursors of DNS-X are active. The increase of palmitoyl-CoA oxidase activity is correlated with the increase of the enzyme amount as shown by immunoblotting. In agreement with the species-specificity of the fibrate neither DNS-X, bezafibrate nor ciprofibrate significantly increase palmitoyl-CoA oxidase activity and the enzyme amount in human hepatic-derived cells, HepG2. This work shows that the dansylated fibrate is a new fluorescent tool to study the subcellular localization and identification of high affinity binding sites, then further on, to elucidate the peroxisome proliferation mechanism and the action of hypolipidaemic agents of the fibrate family.

In vitro glucuronidation of peroxisomal proliferators: 2-ethylhexanoic acid enantiomers and their structural analogs

In order to investigate the glucuronidation of 2-ethylhexanoic acid (2-EHA), a metabolite of the plasticizer di-(2-ethylhexyl) adipate, by liver microsomes of several mammalian species including man, a gas chromatography method for the quantification of the corresponding glucuronides was developed. The variation coefficients for intra- and interassay repeatability were less than 3 and 7%, respectively. The rat liver UDP-glucuronosyl-transferase (UGT) presented similar Km and Vmax toward the two enantiomers. The glucuronidation of the racemate 2-EHA or its enantiomers was strongly increased up to six times by treatment of the rats with phenobarbital and, to a lesser extent, by 3-methylcholanthrene. In contrast, the treatment of the rats clofibrate did not modify the activity. The induction was not stereoselective. The Gunn rats, which present a genetic defect in the bilirubin UGT isoforms, were able to glucuronidate the drug as well as the congenic strain. Moreover, the UGT-2B1 isoform, stably expressed in V79 cells, glucuronidated 2-EHA in an appreciable amount. Interspecies comparison indicated that the most active glucuronidation of 2-EHA occurred in the dog and the rat. The lowest activities were observed in the man and the rabbit. In all species considered, except rabbit and guinea pig which glucuronidated the R isomer faster, the R and S enantiomers were glucuronidated to a similar extent. The glucuronidation activity toward compounds chemically related to 2-EHA increased as a function of molecular weight, but was not affected by the position of the methyl or the ethyl moiety on the hydrocarbon chain. A correlation between the glucuronidation rate of 2-EHA and analogs and the activity of PCoA oxidase was observed.

Stability of drinking prior to alcoholism treatment

This study assessed how many months of pretreatment drinking data would represent a stable baseline. Fifty-one couples were interviewed using the time-line follow-back interviewing procedure to obtain 365 days of pretreatment drinking data. The pattern (binge, episodic, steady) and frequency of drinking did not differ when comparing 30 days prior to treatment with the rest of the year. However, there were significantly more abstinent days in the last 3 months than in the remainder of the pretreatment year. Implications for baseline data collection in alcoholism treatment research are discussed.