Chaperone domains convert prolyl isomerases into generic catalysts of protein folding

The cis/trans isomerization of peptide bonds before proline (prolyl bonds) is a rate-limiting step in many protein folding reactions, and it is used to switch between alternate functional states of folded proteins. Several prolyl isomerases of the FK506-binding protein family, such as trigger factor, SlyD, and FkpA, contain chaperone domains and are assumed to assist protein folding in vivo. The prolyl isomerase activity of FK506-binding proteins strongly depends on the nature of residue Xaa of the Xaa-Pro bond. We confirmed this in assays with a library of tetrapeptides in which position Xaa was occupied by all 20 aa. A high sequence specificity seems inconsistent with a generic function of prolyl isomerases in protein folding. Accordingly, we constructed a library of protein variants with all 20 aa at position Xaa before a rate-limiting cis proline and used it to investigate the performance of trigger factor and SlyD as catalysts of proline-limited folding. The efficiencies of both prolyl isomerases were higher than in the tetrapeptide assays, and, intriguingly, this high activity was almost independent of the nature of the residue before the proline. Apparently, the almost indiscriminate binding of the chaperone domain to the refolding protein chain overrides the inherently high sequence specificity of the prolyl isomerase site. The catalytic performance of these folding enzymes is thus determined by generic substrate recognition at the chaperone domain and efficient transfer to the active site in the prolyl isomerase domain.     

Combination treatment of IFNalpha2b and ribavirin in patients with chronic hepatitis C and persistently normal ALTs

Combination therapy of interferon-_2b and ribavirin was prospectively evaluated in 20 patients with chronic replicative hepatitis and persistently normal ALTs. Patients with normal ALTs on three or more occasions within 6 months received interferon-_2b 3 MU three times a week with ribavirin 1000–1200 mg everyday for 12 months and had a follow-up of 6 months. HCV genotype 1 was found in 16, and HCV genotype 2 or 3 in 4 patients. No patient experienced an ALT elevation during therapy. Ten of 20 patients (50%) cleared virus at the end of treatment. In an intent-to-treat analysis, a sustained virological response (SR) was achieved in 8 of 20 patients (40%). Nonresponse occurred in 5 patients. Relapse and breakthrough were seen in 2 patients each. Treatment was discontinued in 3 patients due to side effects. Interferon (IFN) ribavirin combination therapy is effective in patients with normal ALTs and appears superior to IFN monotherapy.     

The endophytic fungus Piriformospora indica reprograms barley to salt-stress tolerance, disease resistance, and higher yield

Disease resistance strategies are powerful approaches to sustainable agriculture because they reduce chemical input into the environment. Recently, Piriformospora indica, a plant-root-colonizing basidiomycete fungus, has been discovered in the Indian Thar desert and was shown to provide strong growth-promoting activity during its symbiosis with a broad spectrum of plants. Here, we report on the potential of P. indica to induce resistance to fungal diseases and tolerance to salt stress in the monocotyledonous plant barley. The beneficial effect on the defense status is detected in distal leaves, demonstrating a systemic induction of resistance by a root-endophytic fungus. The systemically altered "defense readiness" is associated with an elevated antioxidative capacity due to an activation of the glutathione-ascorbate cycle and results in an overall increase in grain yield. Because P. indica can be easily propagated in the absence of a host plant, we conclude that the fungus could be exploited to increase disease resistance and yield in crop plants.     

Therapeutic choices in convulsive status epilepticus

Introduction: Convulsive status epilepticus (SE) is one of the most frequent and severe neurological emergencies in both adults and children. A timely administration of appropriate antiepileptic drugs (AEDs) can stop seizures early and markedly improve outcome.

Areas covered: The main treatment strategies for SE are reviewed with an emphasis on initial treatments. The established first-line treatment consists of benzodiazepines, most frequently intravenous lorazepam. Benzodiazepines that do not require intravenous administration like intranasal midazolam or intramuscular midazolam are becoming more popular because of easier administration in the field. Other benzodiazepines may also be effective. After treatment with benzodiazepines, treatment with fosphenytoin and phenobarbital is usually recommended. Other intravenously available AEDs, such as valproate and levetiracetam, may be as effective and safe as fosphenytoin and phenobarbital, have a faster infusion time and better pharmacokinetic profile. The rationale behind the need for an early treatment of SE is discussed. The real-time delays of AED administration in clinical practice are described.

Expert opinion: There is limited evidence to support what the best initial benzodiazepine or the best non-benzodiazepine AED is. Recent and developing multicenter trials are evaluating the best treatment options and will likely modify the recommended treatment choices in SE in the near future. Additionally, more research is needed to understand how different treatment options modify prognosis in SE. Timely implementation of care protocols to minimize treatment delays is crucial.     

A truncating PET100 variant causing fatal infantile lactic acidosis and isolated cytochrome c oxidase deficiency

Isolated mitochondrial complex IV (cytochrome c oxidase) deficiency is an important cause of mitochondrial disease in children and adults. It is genetically heterogeneous, given that both mtDNA-encoded and nuclear-encoded gene products contribute to structural components and assembly factors. Pathogenic variants within these proteins are associated with clinical variability ranging from isolated organ involvement to multisystem disease presentations. Defects in more than 10 complex IV assembly factors have been described including a recent Lebanese founder mutation in PET100 in patients presenting with Leigh syndrome. We report the clinical and molecular investigation of a patient with a fatal, neonatal-onset isolated complex IV deficiency associated with multiorgan involvement born to consanguineous, first-cousin British Asian parents. Exome sequencing revealed a homozygous truncating variant (c.142C>T, p.(Gln48*)) in the PET100 gene that results in a complete loss of enzyme activity and assembly of the holocomplex. Our report confirms PET100 mutation as an important cause of isolated complex IV deficiency outside of the Lebanese population, extending the phenotypic spectrum associated with abnormalities within this gene.     

Allelic loss in clinically and screening-detected primary hyperparathyroidism

OBJECTIVE: Parathyroid adenomas frequently harbour deletions of genomic DNA at chromosome regions 1p, 6q and 11q. In this study we related clinical characteristics in 56 patients with primary hyperparathyroidism (pHPT) to loss of heterozygosity (LOH) in these chromosome regions. DESIGN: LOH analysis was performed on 56 sporadic parathyroid tumours using a total of 18 microsatellite markers for chromosome regions 1p, 6q and 11q. LOH was identified, for either radioactive or fluorescent labelled markers, as total absence or reduction of > or = 50% of the signal intensity of an allele in the tumour DNA vs. constitutional DNA. PATIENTS: Twenty-one of the patients were recruited by a population-based screening for pHPT and the remaining pHPT patients were gathered from routine clinical practice. RESULTS: In total, 27%, 23% and 23% of the tumours showed LOH at 1p, 6q and 11q, respectively. LOH at both 1p and 11q was more common in the screening-detected pHPT patients compared to those recruited from clinical practice (38% vs. 20%; P = 0.02 and 43% vs. 11%; P = 0.001, respectively), while allelic loss at 6q was more prevalent in the latter group (11% vs. 31%; P = 0.001). No apparent relationships between LOH at 1p, 6q, and 11q and clinical characteristics, such as glandular weight, serum levels of PTH or calcium, were demonstrated. Moreover, additional LOH analysis of chromosome 1p suggested a putative parathyroid tumour suppressor gene(s) in the region between markers DS214 and D1S503, spanning approximately 6 cM. CONCLUSION: A high frequency of LOH at 1p and 11q in tumours of screening-detected pHPT patients is intriguing, and may suggest that inactivation of known (the MEN1 gene) and putative tumour suppressor genes at these chromosomal regions is associated with a more benign disease.     

Interface connections of a transmembrane voltage sensor

Voltage-sensitive ion channels open and close in response to changes in transmembrane (TM) potential caused by the motion of the S4 voltage sensors. These sensors are alpha-helices that include four or more positively charged amino acids, most commonly arginine. The so-called paddle model, based on the high-resolution structure of the KvAP K+ channel [Jiang, et al. (2003) Nature 423, 33-41], posits that the S4 sensors move within the membrane bilayer in response to TM voltage changes. Direct exposure of S4 sensors to lipid is contrary to the classical expectation that the dielectric contrast between the membrane hydrocarbon core and water presents an insurmountable energetic penalty to burial of electric charges. Nevertheless, recent experiments have shown that a helix with the sequence of KvAP S4 can be inserted across the endoplasmic reticulum membrane. To reconcile this result with the classical energetics argument, we have carried out a molecular dynamics simulation of an isolated TM S4 helix in a lipid bilayer. The simulation reveals a stabilizing hydrogen-bonded network of water and lipid phosphates around the arginines that reduces the effective thickness of the bilayer hydrocarbon core to approximately 10 A in the vicinity of the helix. It suggests that bilayer phospholipids can adapt locally to strongly perturbing protein elements, causing the phospholipids to become a structural extension of the protein.     

Does dystocia during labor pose a risk factor for another non-progressive labor during the subsequent delivery?

Objective: To establish whether failure to progress during labor poses a risk factor for another non-progressive labor (NPL) during the subsequent delivery.

Methods: A retrospective cohort study including singleton pregnancies that failed to progress during the previous labor and resulted in a cesarean section (CS) was conducted. Parturients were classified into three groups for both previous and subsequent labors: CS due to NPL stage I, stage II and an elective CS as a comparison group.

Results: Of 202?462 deliveries, 10?654 women met the inclusion criteria: 3068 women were operated due to NPL stage I and 1218 due to NPL stage II. The comparison group included 6368 women. Using a multivariable logistic regression models, NPL stage I during the previous delivery was found as an independent risk factor for another NPL stage I in the subsequent labor (adjusted odds ratio [OR]?=?2.9; 95% confidence interval [CI]?=?2.4–3.7; p?p?=?0.033; adjusted OR?=?5.3; 95% CI?=?3.7–7.5; p?Conclusion: A previous CS due to a NPL is an independent risk factor for another NPL in the subsequent pregnancy and for recurrent cesarean delivery.