Diabetic nephropathy (DN) represents a major burden to public health cost. Tight glycemic and blood pressure control can dramatically slow but not halt the progression of the disease, and a large number of patients progress towards end-stage renal disease despite the currently available multifactorial interventions. An early and key event in the development of DN is the loss of podocyte function (or glomerular visceral epithelial cells) from the kidney glomerulus, where they contribute to the integrity of the glomerular filtration barrier. The recent evidence that podocyte can be the direct target of circulating hormones, lipids and adipokynes that are affected in diabetes, has prompted us to review the clinical and experimental evidence supporting novel endocrine and metabolic pathways in the pathogenesis of podocyte malfunction and in the development of DN.
Hepatitis C virus (HCV) infection is a major global health burden and is associated with an increased risk of liver cirrhosis and hepatocellular carcinoma. There remains an unmet medical need for efficacious and safe direct antivirals with complementary modes of action for combination in treatment regimens to deliver a high cure rate with a short duration of treatment for HCV patients. Here we report the in vitro inhibitory activity, mode of action, binding kinetics, and resistance profile of TMC647055, a novel and potent nonnucleoside inhibitor of the HCV NS5B RNA-dependent RNA polymerase. In vitro combination studies with an HCV NS3/4A protease inhibitor demonstrated potent suppression of HCV RNA replication, confirming the potential for combination of these two classes in the treatment of chronic HCV infection. TMC647055 is a potent nonnucleoside NS5B polymerase inhibitor of HCV replication with a promising in vitro biochemical, kinetic, and virological profile that is currently undergoing clinical evaluation.
Tumor lysis syndrome (TLS) is characterized by hyperuricemia, hyperkalemia, hyperphosphatemia, and secondary hypocalcemia in patients with a malignancy. When these laboratory abnormalities develop rapidly, clinical complications such as cardiac arrhythmias, acute renal failure, seizures, or death may occur. TLS is caused by rapid release of intracellular contents by dying tumor cells, a condition that is expected to be common in hematologic malignancies. However, TLS rarely occurs with solid tumors, and here we present the second chemotherapy-induced TLS in a patient with advanced gastric adenocarcinoma to be reported in the literature. We also provide information regarding the total cases of TLS in solid tumors reported from 1977 to present day. Our methodology involved identifying key articles from existing reviews of the literature and then using search terms from these citations in MEDLINE to find additional publications. We relied on a literature review published in 2003 by Baeksgaard et al., where they gathered all total 45 cases reported from 1977 to 2003. Then, we looked for new reported cases from 2004 to present day. All reports (case reports, brief reports, letters to editor, correspondence, reviews, journals, and short communications) identified through these searches were reviewed and included.
Sodium gradients in cyanobacteria play an important role in energy storage under photoautotrophic conditions but have not been well studied during autofermentative metabolism under the dark, anoxic conditions widely used to produce precursors to fuels. Here we demonstrate significant stress-induced acceleration of autofermentation of photosynthetically generated carbohydrates (glycogen and sugars) to form excreted organic acids, alcohols, and hydrogen gas by the halophilic, alkalophilic cyanobacterium Arthrospira (Spirulina) maxima CS-328. When suspended in potassium versus sodium phosphate buffers at the start of autofermentation to remove the sodium ion gradient, photoautotrophically grown cells catabolized more intracellular carbohydrates while producing 67% higher yields of hydrogen, acetate, and ethanol (and significant amounts of lactate) as fermentative products. A comparable acceleration of fermentative carbohydrate catabolism occurred upon dissipating the sodium gradient via addition of the sodium-channel blocker quinidine or the sodium-ionophore monensin but not upon dissipating the proton gradient with the proton-ionophore dinitrophenol (DNP). The data demonstrate that intracellular energy is stored via a sodium gradient during autofermentative metabolism and that, when this gradient is blocked, the blockage is compensated by increased energy conversion via carbohydrate catabolism.
The membrane-bound [NiFe] hydrogenase (MBH) of Ralstonia eutropha H16 undergoes a complex maturation process comprising cofactor assembly and incorporation, subunit oligomerization, and finally twin-arginine-dependent membrane translocation. Due to its outstanding O2 and CO tolerance, the MBH is of biotechnological interest and serves as a molecular model for a robust hydrogen catalyst. Adaptation of the enzyme to oxygen exposure has to take into account not only the catalytic reaction but also biosynthesis of the intricate redox cofactors. Here, we report on the role of the MBH-specific accessory proteins HoxR and HoxT, which are key components in MBH maturation at ambient O2 levels. MBH-driven growth on H2 is inhibited or retarded at high O2 partial pressure (pO2) in mutants inactivated in the hoxR and hoxT genes. The ratio of mature and nonmature forms of the MBH small subunit is shifted toward the precursor form in extracts derived from the mutant cells grown at high pO2. Lack of hoxR and hoxT can phenotypically be restored by providing O2-limited growth conditions. Analysis of copurified maturation intermediates leads to the conclusion that the HoxR protein is a constituent of a large transient protein complex, whereas the HoxT protein appears to function at a final stage of MBH maturation. UV-visible spectroscopy of heterodimeric MBH purified from hoxR mutant cells points to alterations of the Fe-S cluster composition. Thus, HoxR may play a role in establishing a specific Fe-S cluster profile, whereas the HoxT protein seems to be beneficial for cofactor stability under aerobic conditions.
The NAD+-reducing soluble hydrogenase (SH) from Ralstonia eutropha H16 catalyzes the H2-driven reduction of NAD+, as well as reverse electron transfer from NADH to H+, in the presence of O2. It comprises six subunits, HoxHYFUI2, and incorporates a [NiFe] H+/H2 cycling catalytic centre, two non-covalently bound flavin mononucleotide (FMN) groups and an iron-sulfur cluster relay for electron transfer. This study provides the first characterization of the diaphorase sub-complex made up of HoxF and HoxU. Sequence comparisons with the closely related peripheral subunits of Complex I in combination with UV/Vis spectroscopy and the quantification of the metal and FMN content revealed that HoxFU accommodates a [2Fe2S] cluster, FMN and a series of [4Fe4S] clusters. Protein film electrochemistry (PFE) experiments show clear electrocatalytic activity for both NAD+ reduction and NADH oxidation with minimal overpotential relative to the potential of the NAD+/NADH couple. Michaelis-Menten constants of 56 µM and 197 µM were determined for NADH and NAD+, respectively. Catalysis in both directions is product inhibited with KI values of around 0.2 mM. In PFE experiments, the electrocatalytic current was unaffected by O2, however in aerobic solution assays, a moderate superoxide production rate of 54 nmol per mg of protein was observed, meaning that the formation of reactive oxygen species (ROS) observed for the native SH can be attributed mainly to HoxFU. The results are discussed in terms of their implications for aerobic functioning of the SH and possible control mechanism for the direction of catalysis.
Resistance to hepatitis C virus (HCV) inhibitors targeting viral enzymes has been observed in in vitro replicon studies and during clinical trials. The factors determining the emergence of resistance and the changes in the viral quasispecies population under selective pressure are not fully understood. To assess the dynamics of variants emerging in vitro under various selective pressures with TMC380765, a potent macrocyclic HCV NS3/4A protease inhibitor, HCV genotype 1b replicon-containing cells were cultured in the presence of a low, high, or stepwise-increasing TMC380765 concentration(s). HCV replicon RNA from representative samples thus obtained was analyzed using (i) population, (ii) clonal, and (iii) 454 deep sequencing technologies. Depending on the concentration of TMC380765, distinct mutational patterns emerged. In particular, culturing with low concentrations resulted in the selection of low-level resistance mutations (F43S and A156G), whereas high concentrations resulted in the selection of high-level resistance mutations (A156V, D168V, and D168A). Clonal and 454 deep sequencing analysis of the replicon RNA allowed the identification of low-frequency preexisting mutations possibly contributing to the mutational pattern that emerged. Stepwise-increasing TMC380765 concentrations resulted in the emergence and disappearance of multiple replicon variants in response to the changing selection pressure. Moreover, two different codons for the wild-type amino acids were observed at certain NS3 positions within one population of replicons, which may contribute to the emerging mutational patterns. Deep sequencing technologies enabled the study of minority variants present in the HCV quasispecies population present at baseline and during antiviral drug pressure, giving new insights into the dynamics of resistance acquisition by HCV.
Sodium concentration cycling was examined as a new strategy for redistributing carbon storage products and increasing autofermentative product yields following photosynthetic carbon fixation in the cyanobacterium Arthrospira (Spirulina) maxima. The salt-tolerant hypercarbonate strain CS-328 was grown in a medium containing 0.24 to 1.24 M sodium, resulting in increased biosynthesis of soluble carbohydrates to up to 50% of the dry weight at 1.24 M sodium. Hypoionic stress during dark anaerobic metabolism (autofermentation) was induced by resuspending filaments in low-sodium (bi)carbonate buffer (0.21 M), which resulted in accelerated autofermentation rates. For cells grown in 1.24 M NaCl, the fermentative yields of acetate, ethanol, and formate increase substantially to 1.56, 0.75, and 1.54 mmol/(g [dry weight] of cells·day), respectively (36-, 121-, and 6-fold increases in rates relative to cells grown in 0.24 M NaCl). Catabolism of endogenous carbohydrate increased by approximately 2-fold upon hypoionic stress. For cultures grown at all salt concentrations, hydrogen was produced, but its yield did not correlate with increased catabolism of soluble carbohydrates. Instead, ethanol excretion becomes a preferred route for fermentative NADH reoxidation, together with intracellular accumulation of reduced products of acetyl coenzyme A (acetyl-CoA) formation when cells are hypoionically stressed. In the absence of hypoionic stress, hydrogen production is a major beneficial pathway for NAD+ regeneration without wasting carbon intermediates such as ethanol derived from acetyl-CoA. This switch presumably improves the overall cellular economy by retaining carbon within the cell until aerobic conditions return and the acetyl unit can be used for biosynthesis or oxidized via respiration for a much greater energy return.
Type 4 renal tubular acidosis is an uncommon clinical manifestation of systemic lupus erythematosus and has been reported to portend a poor prognosis. To the best of our knowledge, this is the first case report which highlights the successful management of a patient with systemic lupus erythematosus complicated by type 4 renal tubular acidosis who did not do poorly.
A 44-year-old Hispanic woman developed a non-anion gap hyperkalemic metabolic acidosis consistent with type 4 renal tubular acidosis while being treated in the hospital for recently diagnosed systemic lupus erythematosus with multi-organ involvement. She responded well to treatment with corticosteroids, hydroxychloroquine and mycophenolate mofetil. Normal renal function was achieved prior to discharge and remained normal at the patient's one-month follow-up examination.
This case increases awareness of an uncommon association between systemic lupus erythematosus and type 4 renal tubular acidosis and suggests a positive impact of early diagnosis and appropriate immunosuppressive treatment on the patient's outcome.
TMC435 is a small-molecule inhibitor of the NS3/4A serine protease of hepatitis C virus (HCV) currently in phase 2 development. The in vitro resistance profile of TMC435 was characterized by selection experiments with HCV genotype 1 replicon cells and the genotype 2a JFH-1 system. In 80% (86/109) of the sequences from genotype 1 replicon cells analyzed, a mutation at NS3 residue D168 was observed, with changes to V or A being the most frequent. Mutations at NS3 positions 43, 80, 155, and 156, alone or in combination, were also identified. A transient replicon assay confirmed the relevance of these positions for TMC435 inhibitory activity. The change in the 50% effective concentrations (EC50s) observed for replicons with mutations at position 168 ranged from <10-fold for those with the D168G or D168N mutation to ∼2,000-fold for those with the D168V or D168I mutation, compared to the EC50 for the wild type. Of the positions identified, mutations at residue Q80 had the least impact on the activity of TMC435 (<10-fold change in EC50s), while greater effects were observed for some replicons with mutations at positions 43, 155, and 156. TMC435 remained active against replicons with the specific mutations observed after in vitro or in vivo exposure to telaprevir or boceprevir, including most replicons with changes at positions 36, 54, and 170 (<3-fold change in EC50s). Replicons carrying mutations affecting the activity of TMC435 remained fully susceptible to alpha interferon and NS5A and NS5B inhibitors. Finally, combinations of TMC435 with alpha interferon and NS5B polymerase inhibitors prevented the formation of drug-resistant replicon colonies.
The development of cellular systems in which the enzyme hydrogenase is efficiently coupled to the oxygenic photosynthesis apparatus represents an attractive avenue to produce H2 sustainably from light and water. Here we describe the molecular design of the individual components required for the direct coupling of the O2-tolerant membrane-bound hydrogenase (MBH) from Ralstonia eutropha H16 to the acceptor site of photosystem I (PS I) from Synechocystis sp. PCC 6803. By genetic engineering, the peripheral subunit PsaE of PS I was fused to the MBH, and the resulting hybrid protein was purified from R. eutropha to apparent homogeneity via two independent affinity chromatographical steps. The catalytically active MBH-PsaE (MBHPsaE) hybrid protein could be isolated only from the cytoplasmic fraction. This was surprising, since the MBH is a substrate of the twin-arginine translocation system and was expected to reside in the periplasm. We conclude that the attachment of the additional PsaE domain to the small, electron-transferring subunit of the MBH completely abolished the export competence of the protein. Activity measurements revealed that the H2 production capacity of the purified MBHPsaE fusion protein was very similar to that of wild-type MBH. In order to analyze the specific interaction of MBHPsaE with PS I, His-tagged PS I lacking the PsaE subunit was purified via Ni-nitrilotriacetic acid affinity and subsequent hydrophobic interaction chromatography. Formation of PS I-hydrogenase supercomplexes was demonstrated by blue native gel electrophoresis. The results indicate a vital prerequisite for the quantitative analysis of the MBHPsaE-PS I complex formation and its light-driven H2 production capacity by means of spectroelectrochemistry.
The RNA-dependent RNA polymerase (NS5B) of hepatitis C virus (HCV) is an unusually attractive target for drug discovery since it contains five distinct drugable sites. The success of novel antiviral therapies will require nonnucleoside inhibitors to be active in at least patients infected with HCV of subtypes 1a and 1b. Therefore, the genotypic assessment of these agents against clinical isolates derived from genotype 1-infected patients is an important prerequisite for the selection of suitable candidates for clinical development. Here we report the 1a/1b subtype profiling of polymerase inhibitors that bind at each of the four known nonnucleoside binding sites. We show that inhibition of all of the clinical isolates tested is maintained, except for inhibitors that bind at the palm-1 binding site. Subtype coverage varies across chemotypes within this class of inhibitors, and inhibition of genotype 1a improves when hydrophobic contact with the polymerase is increased. We investigated if the polymorphism of the palm-1 binding site is the sole cause of the reduced susceptibility of subtype 1a to inhibition by 1,5-benzodiazepines by using reverse genetics, X-ray crystallography, and surface plasmon resonance studies. We showed Y415F to be a key determinant in conferring resistance on subtype 1a, with this effect being mediated through an inhibitor- and enzyme-bound water molecule. Binding studies revealed that the mechanism of subtype 1a resistance is faster dissociation of the inhibitor from the enzyme.
The medical management of secondary hyperparathyroidism in patients with end-stage renal disease involves a combination of dietary restrictions, phosphate binders, active vitamin D analogs, and calcimimetics.
We report the case of a 36-year-old Hispanic dialysis patient, originally from Cuba and now residing in the USA, who developed severe bone pain and muscle twitching after starting low dose cinacalcet, despite normal pre-dialysis ionized calcium and elevated parathyroid hormone. The clinical symptoms correlated with increased symmetrical uptake on bone scan that resolved rapidly upon discontinuation of cinacalcet.
Cinacalcet may induce severe bone pain and a unique bone scan uptake pattern in hemodialysis patients.
Proteinuria development and decrease in glomerular filtration rate (GFR) has been observed after successful islet transplantation. The aim of this study was to determine clinical, laboratory and immunosuppressant-related factors associated with kidney dysfunction in islet transplant recipients.
A retrospective cohort study was conducted in 35 subjects submitted to pancreatic islet transplantation as treatment for unstable type 1 diabetes mellitus. Demographic, anthropometrical and laboratory data, as well as immunosuppressive and anti-hypertensive therapy were recorded. Kidney function was assessed by albuminuria and estimated GFR (eGFR), calculated by Modification of Diet in Renal Disease formula.
Age was the only independent risk factor for low eGFR (<60 ml/min/1.73 m2) [OR=1.78 (1.22–2.61)]. LDL-cholesterol [OR=2.90 (1.37–6.12)] and previous microalbuminuria [OR=6.42 (1.42–29.11)] were risk factors for transient macroalbuminuria. Interestingly, tacrolimus was a protective factor for macroalbuminuria [OR=0.12 (0.06–0.26)]. Six-out-of-thirty (20%) normoalbuminuric subjects at baseline progressed to microalbuminuria. No subject developed sustained macroalbuminuria. Surprisingly, overall eGFR remained stable during follow-up (before transplant: 74.0±2.0, during immunosuppressive therapy: 75.4±2.8, after withdrawal: 76.3±5.3 ml/min/1.73 m2; P>0.05). Even subjects with low eGFR and/or microalbuminuria at baseline (n=10) maintained stable values post-transplantation (61.13±3.25 vs. 63.32±4.36 ml/min/1.73 m2, P=0.500).
Kidney function remained stable after islet transplantation alone. The unchanged kidney function found in this sample may be attributed to healthier kidney status at baseline and possibly to prompt treatment of modifiable risk factors. Aggressive treatment of risk factors for nephropathy, such as blood pressure, LDL-cholesterol and careful tacrolimus levels monitorization, should be part of islet transplant recipient care.
islet transplantation; kidney function; albuminuria; lipids; blood pressure
The hepatitis C virus (HCV) NS3/4A serine protease has been explored as a target for the inhibition of viral replication in preclinical models and in HCV-infected patients. TMC435350 is a highly specific and potent inhibitor of NS3/4A protease selected from a series of novel macrocyclic inhibitors. In biochemical assays using NS3/4A proteases of genotypes 1a and 1b, inhibition constants of 0.5 and 0.4 nM, respectively, were determined. TMC435350 inhibited HCV replication in a cellular assay (subgenomic 1b replicon) with a half-maximal effective concentration (EC50) of 8 nM and a selectivity index of 5,875. The compound was synergistic with alpha interferon and an NS5B inhibitor in the replicon model and additive with ribavirin. In rats, TMC435350 was extensively distributed to the liver and intestinal tract (tissue/plasma area under the concentration-time curve ratios of >35), and the absolute bioavailability was 44% after a single oral administration. Compound concentrations detected in both plasma and liver at 8 h postdosing were above the EC99 value measured in the replicon. In conclusion, given the selective and potent in vitro anti-HCV activity, the potential for combination with other anti-HCV agents, and the favorable pharmacokinetic profile, TMC435350 has been selected for clinical development.
Unlike the quite frequent renal involvement seen in cases of Multiple Myeloma, the kidney is hardly ever compromised in patients with Waldenström's Macroglobulinemia. Nephrotic range proteinuria is a very unusual manifestation of renal injury in these patients and when present it is due to amyloid light-chain deposition most of the times.
A 60-year-old male patient presented to the hospital with nephrotic syndrome, renal insufficiency, hypertension and lymphadenopathy. The investigations led to the diagnosis of Waldenström's Macroglobulinemia with associated nephrotic syndrome and chronic kidney disease due to an unusual form of hypocomplementemic glomerulopathy with histopathological features similar to those seen in mesangiocapillary glomerulonephritis type III, but lacking proliferative changes.
We present an unusual case of immunologically-mediated renal damage in a patient with Waldenström's Macroglobulinemia, leading to non-amyloid nephrotic syndrome and chronic renal insufficiency.
Complications of chronic kidney disease (CKD) contribute to morbidity and mortality. Consequently, treatment guidelines have been developed to facilitate early detection and treatment. However, given the high prevalence of CKD, many patients with early CKD are seen by non-nephrologists, who need to be aware of CKD complications, screening methods and treatment goals in order to initiate timely therapy and referral.
We performed a web-based survey to assess perceptions and practice patterns in CKD care among 376 family medicine and internal medicine trainees in the United States. Questions were focused on the identification of CKD risk factors, screening for CKD and associated co-morbidities, as well as management of anemia and secondary hyperparathyroidism in patients with CKD.
Our data show that CKD risk factors are not universally recognized, screening for CKD complications is not generally taken into consideration, and that the management of anemia and secondary hyperparathyroidism poses major diagnostic and therapeutic difficulties for trainees.
Educational efforts are needed to raise awareness of clinical practice guidelines and recommendations for patients with CKD among future practitioners.
The Z protein is the matrix protein of arenaviruses and has been identified as the main driving force for budding. Both LCMV and Lassa virus Z proteins bud from cells in the absence of other viral proteins as enveloped virus-like particles. Z accumulates near the inner surface of the plasma membrane where budding takes place. Furthermore, biochemical data have shown that Z is strongly membrane associated. The primary sequence of Z lacks a typical transmembrane domain and until now it is not understood by which mechanism Z is able to interact with cellular membranes. In this report, we analyzed the role of N-terminal myristoylation for the membrane binding of Lassa virus Z. We show that disruption of the N-terminal myristoylation signal by substituting the N-terminal glycine with alanine (Z-G2A mutant) resulted in a significant reduction of Z protein association with cellular membranes. Furthermore, removal of the myristoylation site resulted in a relocalization of Z from a punctuate distribution to a more diffuse cellular distribution pattern. Finally, treatment of Lassa virus-infected cells with various myristoylation inhibitors drastically reduced efficient Lassa virus replication. Our data indicate that myristoylation of Z is critical for its binding ability to lipid membranes and thus, for effective virus budding.
About 5 million Americans suffer from heart failure. Given the correlation of heart failure with age and the rising life expectancy, the prevalence of heart failure continues to increase in the general population. Sympathetic stimulation intensifies with progressive heart failure. The rationale to use β-blockers in individuals with impaired myocardial function is based on experimental evidence supporting the notion that prolonged α- and β-adrenergic stimulation leads to worsening heart failure. Until recently, safety concerns have precluded the use of β-blockers in patients with diabetes and heart failure. However, several large, randomized, placebo-controlled clinical trials such as Metoprolol Randomized Intervention Trial in Congestive Heart Failure (MERIT-HF) have shown that β-blockers can be safely used in patients with diabetes and heart failure. Moreover, β-blockers significantly improved morbidity and mortality in this population. Based on this evidence, it is now recommended to add β-blockers such as metoprolol CR/XL with an escalating dosage regimen to the treatment of patients with symptomatic heart failure who already are receiving a stable medical regimen including angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, diuretics, vasodilators, or digitalis.
metoprolol; heart failure; diabetes mellitus; β-adrenergic blocking agents; MERIT-HF
Lassa virus glycoprotein is synthesised as a precursor (preGP-C) into the lumen of the endoplasmic reticulum. After cotranslational cleavage of the signal peptide, the immature GP-C is posttranslationally processed into the N-terminal subunit GP-1 and the C-terminal subunit GP-2 by the host cell subtilase SKI-1/S1P. The glycoprotein precursor contains eleven potential N-glycosylation sites. In this report, we investigated the effect of each N-glycan on proteolytic cleavage and cell surface transport by disrupting the consensus sequences of eleven potential N-glycan attachment sites individually. Five glycoprotein mutants with disrupted N-glycosylation sites were still proteolytically processed, whereas the remaining N-glycosylation sites are necessary for GP-C cleavage. Despite the lack of proteolytic processing, all cleavage-defective mutants were transported to the cell surface and remained completely endo H-sensitive. The findings indicate that N-glycans are needed for correct conformation of GP-C in order to be cleaved by SKI-1/S1P.
The National Kidney Foundation has formulated clinical practice guidelines for patients with chronic kidney disease (K/DOQI). However, little is know about how many patients actually achieve these goals in a dedicated clinic for chronic kidney disease.
We performed a cross-sectional analysis of 198 patients with an estimated glomerular filtration rate of less than 30 ml/min/1.73 m2 and determined whether K/DOQI goals were met for calcium, phosphate, calcium-phosphate product, parathyroid hormone, albumin, bicarbonate, hemoglobin, lipids, and blood pressure.
We found that only a small number of patients achieved K/DOQI targets. Recent referral to the nephrologist, failure to attend scheduled clinic appointments, African American ethnicity, diabetes, and advanced renal failure were significant predictors of low achievement of K/DOQI goals.
We conclude that raising awareness of chronic kidney disease and K/DOQI goals among primary care providers, early referral to a nephrologist, the exploration of socioeconomic barriers and cultural differences, and both patient and physician education are critical to improve CKD care in patients with Stage 4 and 5 CKD.
By taking advantage of the tightly clustered genes for the membrane-bound [NiFe] hydrogenase of Ralstonia eutropha H16, broad-host-range recombinant plasmids were constructed carrying the entire membrane-bound hydrogenase (MBH) operon encompassing 21 genes. We demonstrate that the complex MBH biosynthetic apparatus is actively produced in hydrogenase-free hosts yielding fully assembled and functional MBH protein.
Lassa virus is an enveloped virus with glycoprotein spikes on its surface. It contains an RNA ambisense genome that encodes the glycoprotein precursor GP-C, the nucleoprotein NP, the polymerase L, and the Z protein. Here we demonstrate that the Lassa virus Z protein (i) is abundant in viral particles, (ii) is strongly membrane associated, (iii) is sufficient in the absence of all other viral proteins to release enveloped particles, and (iv) contains two late domains, PTAP and PPXY, necessary for the release of virus-like particles. Our data provide evidence that Z is the Lassa virus matrix protein that is the driving force for virus particle release.
The envelope glycoprotein (GP) of lymphocytic choriomeningitis virus (LCMV) is posttranslationally cleaved into two subunits. We show here that this endoproteolytic processing is not required for transport to the cell surface but is essential for LCMV GP to mediate infectivity of pseudotyped retroviral vectors. By systematic mutational analysis of the LCMV GP cleavage site, we determined that the consensus motif R-(R/K/H)-L-(A/L/S/T/F)265 is essential for the endoproteolytic processing. In agreement with the identified consensus motif, we show that the cellular subtilase SKI-1/S1P cleaves LCMV GP.