SPG20 Protein Spartin Associates with Cardiolipin via Its Plant-Related Senescence Domain and Regulates Mitochondrial Ca2+ Homeostasis

Hereditary spastic paraplegias (HSPs) are a group of neurological disorders characterized clinically by spasticity of lower limbs and pathologically by degeneration of the corticospinal tract. Troyer syndrome is an autosomal recessive HSP caused by a frameshift mutation in the spartin (SPG20) gene. Previously, we established that this mutation results in a lack of expression of the truncated mutant spartin protein. Spartin is involved in many cellular processes and associates with several intracellular organelles, including mitochondria. Spartin contains a conserved plant-related senescence domain at its C-terminus. However, neither the function of this domain nor the roles of spartin in mitochondrial physiology are currently known. In this study, we determined that the plant-related senescence domain of spartin interacts with cardiolipin but not with two other major mitochondrial phospholipids, phosphatidylcholine and phosphatidylethanolamine. We also found that knockdown of spartin by small interfering RNA in a human neuroblastoma cell line resulted in depolarization of the mitochondrial membrane. In addition, depletion of spartin resulted in a significant decrease in both mitochondrial calcium uptake and mitochondrial membrane potential in cells treated with thapsigargin. Our results suggest that impairment of mitochondrial calcium uptake might contribute to the neurodegeneration of long corticospinal axons and the pathophysiology of Troyer syndrome

Molecular Determinants of Survival Motor Neuron (SMN) Protein Cleavage by the Calcium-Activated Protease, Calpain

Spinal muscular atrophy (SMA) is a leading genetic cause of childhood mortality, caused by reduced levels of survival motor neuron (SMN) protein. SMN functions as part of a large complex in the biogenesis of small nuclear ribonucleoproteins (snRNPs). It is not clear if defects in snRNP biogenesis cause SMA or if loss of some tissue-specific function causes disease. We recently demonstrated that the SMN complex localizes to the Z-discs of skeletal and cardiac muscle sarcomeres, and that SMN is a proteolytic target of calpain. Calpains are implicated in muscle and neurodegenerative disorders, although their relationship to SMA is unclear. Using mass spectrometry, we identified two adjacent calpain cleavage sites in SMN, S192 and F193. Deletion of small motifs in the region surrounding these sites inhibited cleavage. Patient-derived SMA mutations within SMN reduced calpain cleavage. SMN(D44V), reported to impair Gemin2 binding and amino-terminal SMN association, drastically inhibited cleavage, suggesting a role for these interactions in regulating calpain cleavage. Deletion of A188, a residue mutated in SMA type I (A188S), abrogated calpain cleavage, highlighting the importance of this region. Conversely, SMA mutations that interfere with self-oligomerization of SMN, Y272C and SMNΔ7, had no effect on cleavage. Removal of the recently-identified SMN degron (Δ268-294) resulted in increased calpain sensitivity, suggesting that the C-terminus of SMN is important in dictating availability of the cleavage site. Investigation into the spatial determinants of SMN cleavage revealed that endogenous calpains can cleave cytosolic, but not nuclear, SMN. Collectively, the results provide insight into a novel aspect of the post-translation regulation of SMN

Dermacentor reticulatus: a vector on the rise

Dermacentor reticulatus is a hard tick species with extraordinary biological features. It has a high reproduction rate, a rapid developmental cycle, and is also able to overcome years of unfavourable conditions. Dermacentor reticulatus can survive under water for several months and is cold-hardy even compared to other tick species. It has a wide host range: over 60 different wild and domesticated hosts are known for the three active developmental stages. Its high adaptiveness gives an edge to this tick species as shown by new data on the emergence and establishment of D. reticulatus populations throughout Europe. The tick has been the research focus of a growing number of scientists, physicians and veterinarians. Within the Web of Science database, more than a fifth of the over 700 items published on this species between 1897 and 2015 appeared in the last three years (2013–2015). Here we attempt to synthesize current knowledge on the systematics, ecology, geographical distribution and recent spread of the species and to highlight the great spectrum of possible veterinary and public health threats it poses. Canine babesiosis caused by Babesia canis is a severe leading canine vector-borne disease in many endemic areas. Although less frequently than Ixodes ricinus, D. reticulatus adults bite humans and transmit several Rickettsia spp., Omsk haemorrhagic fever virus or Tick-borne encephalitis virus. We have not solely collected and reviewed the latest and fundamental scientific papers available in primary databases but also widened our scope to books, theses, conference papers and specialists colleagues’ experience where needed. Besides the dominant literature available in English, we also tried to access scientific literature in German, Russian and eastern European languages as well. We hope to inspire future research projects that are necessary to understand the basic life-cycle and ecology of this vector in order to understand and prevent disease threats. We conclude that although great strides have been made in our knowledge of the eco-epidemiology of this species, several gaps still need to be filled with basic research, targeting possible reservoir and vector roles and the key factors resulting in the observed geographical spread of D. reticulatus. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13071-016-1599-x) contains supplementary material, which is available to authorized users

Combination of bioanode and biocathode for the conversion of wastes into biocommodities using microbial electrosynthesis

PosterBioelectrochemical systems (BES) as microbial fuel cells take advantages of microorganisms to convert the chemical energy of organic waste into electricity. Recently, the discovery that BES can also be used for the synthesis of biocommoditiesvia microbial electrosynthesis (MES) has greatly expanded the horizons for their applications. Indeed, some microbes are able to use electrons and molecules such as CO2 to synthesize reduced products: volatile fatty acids, alcohols etc... By combining both these processes, it should thus theoretically be possible to use the electrons of organic waste to synthesize bio-based chemicals in a clean and controlled compartment. However, these technologies are only few years old and required scientific data before they can be practically applied. In this context, we developed a dual-chamber reactor with both biotic anode (carbon cloth) and cathode (stainless steel) separated by a cation-exchange membrane. Bioanode was inoculated using an anodic biofilm sample formed in biological wastes and biocathode by injecting a suspension of a homoacetogen-enriched culture. Acetate (600mg/l) was used as electron donor in the anodic compartment. Chronoamperometry experiments were carried out with a multi-channel potentiostat in order to monitor electroactivity of the microbial communities. Anode potential was poised at +0.158 volts versus saturated calomel electrode (SCE) for startup. Chemical analyses (volatile fatty acids (VFAs), cations/anions, chemical oxygen demand, and total organic carbon) were performed to evaluate the metabolic pathways. Microbial community diversity was investigated by 16S rDNA pyrosequencing (MiSeq sequencer, Illumina®). After the total consumption of acetate at anode (run 1), a second run (run 2) was launched by re-injecting 600 mg/L of acetate in anodic compartment and also 2-bromo-ethane sulfonate (2-BES) at the cathode to inhibit methanogenesis. Current density of 5 A/m² was reached after 24h of experiment. During run 1 and 2 78% and 89% of electrons from acetate were respectively transferred in the system revealing satisfying coulombic efficiency at the bioanode. During run 1, incoming electrons at biocathode were mainly used to produce methane (53% of total incoming electrons) and only traces of VFAs were detected. However, at the end of the second run, VFAs accumulated with a production rate of acetate reaching 11 g.m².d-1 and corresponding to 29% of the electrons coming from the anode. Using gas chromatography coupled with mass spectrometry, caprylate (C8H16O2) was also detected in reactors showing the ability of the MES system to produce molecules with an elongated carbon chain. Microbial diversity profiles showed a switch of archaeal and bacterial populations in cathodic compartment between run 1 and run 2 suggesting that VFAs production resulted from microbial adaptation to the addition of BES in the cathodic compartment. Overall this work constitutes a first step toward the utilization of MES systems for the conversion of organic wastes into biofuels and chemicals using coupled bioanode and biocathode