Major vault protein (MVP) gene polymorphisms and drug resistance in mesial temporal lobe epilepsy with hippocampal sclerosis

The human major vault protein (MVP) has been implicated in the development of drug resistance in cancer cells. Over expression of MVP has also been reported in brain tissue samples from antiepileptic drug (AED)-resistant human focal epilepsies. To investigate the relationship between single nucleotide polymorphisms (SNPs) involving the MVP gene and AED-resistance, we compared the distribution of three SNPs in the MVP gene, rs4788187, rs3815824 and rs3815823, among 220 patients with mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) (prototype of AED-resistant epilepsy syndrome), 201 patients with juvenile myoclonic epilepsy (JME) (prototype of AED-responsive epilepsy syndrome) and 213 ethnically matched non-epilepsy controls. All the patients and controls were residents of the South Indian state of Kerala for more than three generations. We did not find any significant difference in allele and genotypic frequencies of the studied SNPs between AED-resistant and AED-responsive cohorts, and between AED-resistant and AED-responsive cohorts independently and pooled together when compared with the controls. We conclude that rs4788187, rs3815824, rs3815823 variants of the MVP gene are associated neither with predisposition for epilepsy nor with AED-resistance in the population that we have studied. Our results suggest the need for further research into the link between MVP and AED-resistance.     

High prevalence of cerebral venous sinus thrombosis (CVST) as presentation of cystathionine beta-synthase deficiency in childhood: Molecular and clinical findings of Turkish probands

Classical homocystinuria is the most commonly inherited disorder of sulfur metabolism, caused by the genetic alterations in human cystathionine beta-synthase (CBS) gene. In this study, we present comprehensive clinical findings and the genetic basis of homocystinuria in a cohort of Turkish patients. Excluding some CBS mutations, detailed genotype–phenotype correlation for different CBS mutations has not been established in literature. We aimed to make clinical subgroups according to main clinical symptoms and discussed these data together with mutational analysis results from our patients. Totally, 16 different mutations were identified; twelve of which had already been reported, and four are novel (p.N93Y, p.L251P, p.D281V and c.829−2A>T). The probands were classified into three major groups according to the clinical symptoms caused by these mutations. A psychomotor delay was the most common diagnostic symptom (n = 12, 46.2% neurological presentation), followed by thromboembolic events (n = 6, 23.1% vascular presentation) and lens ectopia, myopia or marfanoid features (n = 5, 19.2% connective tissue presentation). Pyridoxine responsiveness was 7.7%; however, with partial responsive probands, the ratio was 53.9%.     

A comparative study of fluorescent singlet oxygen probes in plant leaves

Four fluorescent singlet oxygen sensors: DanePy, its oxalate salt, Singlet Oxygen Sensor Green and MVP, were infiltrated into tobacco leaves and tested for toxicity, subcellular localization, light sensitivity and capacity to trap the singlet oxygen produced in photoinhibition. For reference, a broad sensitivity free radical probe, TEMPO-9-AC, was also included. Photochemical yield was approximately 15% and 10% inhibited by Singlet Oxygen Sensor Green and MVP, respectively, but was not significantly affected by the other probes. Under photoinhibitory conditions, brought about by irradiating lincomycin-treated leaves with strong photosynthetically active radiation, DanePy and Singlet Oxygen Sensor Green were responsive. Singlet Oxygen Sensor Green was also reactive to low, non-photoinhibitory light exposure of the leaf, which was not characteristic to the other probes. MVP did not respond to singlet oxygen which can partly be explained by a possible attenuation of its blue emission in the leaf, as shown by the example TEMPO-9-AC. DanePy-oxalate did not respond to photosynthetic singlet oxygen due to lack of its penetration into photosynthetic tissue and hence could be useful in detecting any singlet oxygen which escapes from a chloroplast initiation site. DanePy was localized in the chloroplasts, while Singlet Oxygen Sensor Green was mainly found in the epidermal cells preferentially associated with the nucleus.      

A chemiluminescent probe specific for singlet oxygen

We have synthesized a methoxyvinylpyrene (MVP) in order to model the mechanism for the observed microsomal chemiluminescence of benzo[a]pyrene 7,8-dihydrodiol, the proximate carcinogenic metabolite of benzo[a]pyrene. This MVP analog has been found to be a highly efficient and specific chemiluminescent probe for picomole quantities of singlet oxygen and singlet oxygen equivalents, and it produces significant chemiluminescence when reacted with cytochrome P-450 enzymes.     

Estimating Minimum Area of Suitable Habitat and Viable Population Size for the Northern Muriqui (Brachyteles hypoxanthus)

A population viability analysis (PVA) using the computer package VORTEX was conducted to assess the minimum viable population (MVP) of the Atlantic Forest endemic primate Brachyteles hypoxanthus. The objectives were: (1) to estimate demographic and genetic MVPs that could be used as quasi-extinction thresholds for future modeling, and (2) to estimate the minimum area of suitable habitat (MASH). The model predicted that populations of 40 and 700 individuals were necessary to achieve demographic and genetic stability, respectively. The model was more sensitive to changes in inbreeding depression, sex ratio and reproduction (percentage of breeding females). MASH estimated to contain genetically viable populations reached 11,570 ha. Muriquis have managed to persist despite severe habitat disturbance, but the results suggest that although most of the extant populations are not threatened by extinction, they are too small to be genetically viable in the long-run, and will loose most of their heterozygosity.     

Structural domains of vault proteins: a role for the coiled coil domain in vault assembly

Vaults consist of multiple copies of three proteins (MVP, VPARP, and TEP1) and several untranslated RNAs. The function of vaults is unknown but the typical and evolutionary conserved structure indicates a role in intracellular transport. Although all vault components have been identified and characterized, not much is known about vault protein assembly. In this study we identified and analyzed structural domains involved in vault assembly with emphasis on protein-protein interactions. Using a yeast two-hybrid system, we demonstrate within MVP an intramolecular binding site and show that MVP molecules interact with each other via their coiled coil domain. We show that purified MVP is able to bind calcium, most likely at calcium-binding EF-hands. No interactions could be detected between TEP1 and other vault proteins. However, the N-terminal half of MVP binds to a specific domain in the C-terminus of VPARP. Furthermore, VPARP contains amino acid stretches mediating intramolecular binding.     

Mechanisms and strategies to overcome multiple drug resistance in cancer

One of the major problems in chemotherapy is multidrug resistance (MDR) against anticancer drugs. ATP-binding cassette (ABC) transporters are a family of proteins that mediate MDR via ATP-dependent drug efflux pumps. Many MDR inhibitors have been identified, but none of them have been proven clinically useful without side effects. Efforts continue to discover not toxic MDR inhibitors which lack pharmacokinetic interactions with anticancer drugs. Novel approaches have also been designed to inhibit or circumvent MDR. In this review, the structure and function of ABC transporters and development of MDR inhibitors are described briefly including various approaches to suppress MDR mechanisms.     

Structure of Internalin InlK from the Human Pathogen Listeria monocytogenes

Listeria monocytogenes is a human pathogen that employs a wide variety of virulence factors in order to adhere to, invade, and replicate within target cells. Internalins play key roles in processes ranging from adhesion to receptor recognition and are thus essential for infection. Recently, InlK, a surface-associated internalin, was shown to be involved in Listeria's ability to escape from autophagy by recruitment of the major vault protein (MVP) to the bacterial surface. Here, we report the structure of InlK, which harbors four domains arranged in the shape of a “bent arm”. The structure supports a role for the “elbow” of InlK in partner recognition, as well as of two Ig-like pedestals intercalated by hinge regions in the projection of InlK away from the surface of the bacterium. The unusual fold and flexibility of InlK could be essential for MVP binding and concealment from recognition by molecules involved in the autophagic process.     

Evaluation of Minimum Viable Population Size and Conservation Status of the Long-furred Woolly Mouse Opossum Micoureus paraguayanus: An Endemic Marsupial of the Atlantic Forest

A population viability analysis (PVA) using the computer package VORTEX was conducted to assess the minimum viable population (MVP) of the Atlantic Forest endemic marsupial Micoureus paraguayanus. The objectives were: to estimate demographic and genetic MVPs that could be used as quasi-extinction thresholds for future modeling, to estimate the minimum area of suitable habitat (MASH), and to use these results to apply IUCN red list criteria so as to suggest its proper status classification. The model predicted that populations of 100 and 2000 individuals were necessary to achieve demographic and genetic stability, respectively, within a time frame of 100 years. The model was sensitive to changes in inbreeding depression, mortality and reproduction. MASH estimated to contain genetically viable populations reached 1300 ha. Fortunately, there still are quite a number of forest remnants equal to or larger than this. Isolation is suggested as the principal threat facing M. paraguayanus. Therefore, promoting conditions for dispersal together with efforts dealing with translocation, should prove to be the most appropriate management strategies for M. paraguayanus at this stage. A landscape pattern composed of large patches holding MVPs and sets of smaller patches harboring viable metapopulations that maximize probability of dispersal can provide a viable scenario for the conservation of M. paraguayanus.