Prediction of P300 BCI Aptitude in Severe Motor Impairment

Brain-computer interfaces (BCIs) provide a non-muscular communication channel for persons with severe motor impairments. Previous studies have shown that the aptitude with which a BCI can be controlled varies from person to person. A reliable predictor of performance could facilitate selection of a suitable BCI paradigm. Eleven severely motor impaired participants performed three sessions of a P300 BCI web browsing task. Before each session auditory oddball data were collected to predict the BCI aptitude of the participants exhibited in the current session. We found a strong relationship of early positive and negative potentials around 200 ms (elicited with the auditory oddball task) with performance. The amplitude of the P2 (r  =  −0.77) and of the N2 (r  =  −0.86) had the strongest correlations. Aptitude prediction using an auditory oddball was successful. The finding that the N2 amplitude is a stronger predictor of performance than P3 amplitude was reproduced after initially showing this effect with a healthy sample of BCI users. This will reduce strain on the end-users by minimizing the time needed to find suitable paradigms and inspire new approaches to improve performance.     

Mitochondrial ghost lineages blur phylogeography and taxonomy of Natrix helvetica and N. natrix in Italy and Corsica

Grass snakes are widely distributed across the Western Palearctic. Recent phylogeographic studies provided evidence that three distinct parapatric species exist. Two of these occur in Italy, Natrix helvetica and N. natrix, and a contact zone between both taxa has been suggested for north-eastern Italy. Moreover, previous investigations revealed for the Italian Peninsula a complex phylogeographic structure. Using mtDNA sequences and microsatellite loci, we examined the situation for mainland Italy, Sicily, Sardinia, and Corsica. Our study confirmed the occurrence of N. natrix in north-eastern Italy. Cline analyses revealed limited gene flow between N. helvetica and N. natrix across a narrow hybrid zone. Within N. helvetica, conflicting patterns of mitochondrial and nuclear genomic differentiation were revealed. Three nuclear genomic clusters were found; one of them corresponded to no fewer than five distinct and, in part, deeply divergent and ancient mitochondrial lineages from mainland Italy and Sicily. This cluster was paraphyletic with respect to the two remaining mitochondrial lineages, each of which matched with another nuclear genomic cluster (one from Corsica plus Sardinia and another one from western Europe north of the Alps). This unexpected pattern most likely results from mainly male-mediated gene flow and female philopatry combined with population-density-dependent processes such as ‘high-density blocking’. With respect to taxonomy, we propose to synonymize N. h. lanzai Kramer, 1970 with N. h. sicula (Cuvier, 1829), acknowledging their lacking nuclear genomic differentiation. The studied hybrid zone of N. h. helvetica and N. h. sicula in Italy is wide, with a smooth cline for nuclear markers, supporting their subspecies status. We found no evidence for the distinctiveness of the two subspecies from Corsica (N. h. corsa) and Sardinia (N. h. cetti), suggesting their synonymy, but refrain from taxonomic conclusions because of small sample sizes and the endangered status of the Sardinian taxon.     

MiR-21-5p but not miR-1-3p expression is modulated by preconditioning in a rat model of myocardial infarction

Molecular Biology Reports - Isoflurane (Iso) preconditioning (PC) is known to be cardioprotective against ischemia/reperfusion (I/R) injury. It was previously shown that microRNA-21-5p (miR-21-5p)...     

Structural analysis of the Ras-like G protein MglA and its cognate GAP MglB and implications for bacterial polarity

The bacterium Myxococcus xanthus uses a G protein cycle to dynamically regulate the leading/lagging pole polarity axis. The G protein MglA is regulated by its GTPase-activating protein (GAP) MglB, thus resembling Ras family proteins. Here, we show structurally and biochemically that MglA undergoes a dramatic, GDP-GTP-dependent conformational change involving a screw-type forward movement of the central β2-strand, never observed in any other G protein. This movement and complex formation with MglB repositions the conserved residues Arg53 and Gln82 into the active site. Residues required for catalysis are thus not provided by the GAP MglB, but by MglA itself. MglB is a Roadblock/LC7 protein and functions as a dimer to stimulate GTP hydrolysis in a 2:1 complex with MglA. In vivo analyses demonstrate that hydrolysis mutants abrogate Myxococcus' ability to regulate its polarity axis changing the reversal behaviour from stochastic to oscillatory and that both MglA GTPase activity and MglB GAP catalysis are essential for maintaining a proper polarity axis.     

Down-regulation of CK2 activity results in a decrease in the level of cdc25C phosphatase in different prostate cancer cell lines

Protein kinase CK2 is implicated in the regulation of the cell cycle. In addition to a variety of functions, CK2 has anti-apoptotic properties. So far the role of CK2 linking both pathways in the cell is not clear. Some years ago we found that CK2 phosphorylates cdc25C, one member of the cdc25 family of proteins. In this study, we showed that inhibition of CK2 activity by three different inhibitors led to a down-regulation of the level of cdc25C. Inhibition of CK2 activity by transfecting the dominant-negative CK2α subunit also resulted in a down-regulation of the level of cdc25C whereas inhibition of CK2α' had no effect on the cdc25C level. In both cases, we observed apoptosis by PARP cleavage as well as by an increase in γH2AX phosphorylation. These results show that down-regulation of the level of cdc25C is not a prerequisite for the induction of apoptosis.     

Synthesis and characterization of natural and modified antifreeze glycopeptides: glycosylated foldamers

In Arctic and Antarctic marine regions, where the temperature declines below the colligative freezing point of physiological fluids, efficient biological antifreeze agents are crucial for the survival of polar fish. One group of such agents is classified as antifreeze glycoproteins (AFGP) that usually consist of a varying number (n = 4–55) of [AAT] _n -repeating units. The threonine side chain of each unit is glycosidically linked to β-d-galactosyl-(1 → 3)-α-N-acetyl-d-galactosamine. These biopolymers can be considered as biological antifreeze foldamers. A preparative route for stepwise synthesis of AFGP allows for efficient synthesis. The diglycosylated threonine building block was introduced into the peptide using microwave-enhanced solid phase synthesis. By this versatile solid phase approach, glycosylated peptides of varying sequences and lengths could be obtained. Conformational studies of the synthetic AFGP analogs were performed by circular dichroism experiments (CD). Furthermore, the foldamers were analysed microphysically according to their inhibiting effect on ice recrystallization and influence on the crystal habit.     

Cell-based analysis of structure-function activity of threonine aspartase 1

Taspase1 is a threonine protease responsible for cleaving intracellular substrates. As such, (de)regulated Taspase1 function is expected not only to be vital for ordered development but may also be relevant for disease. However, the full repertoires of Taspase1 targets as well as the exact biochemical requirements for its efficient and substrate-specific cleavage are not yet resolved. Also, no cellular assays for this protease are currently available, hampering the exploitation of the (patho)biological relevance of Taspase1. Here, we developed highly efficient cell-based translocation biosensor assays to probe Taspase1 trans-cleavage in vivo. These modular sensors harbor variations of Taspase1 cleavage sites and localize to the cytoplasm. Expression of Taspase1 but not of inactive Taspase1 mutants or of unrelated proteases triggers proteolytic cleavage and nuclear accumulation of the biosensors. Employing our assay combined with scanning mutagenesis, we identified the sequence and spatial requirements for efficient Taspase1 processing in liquid and solid tumor cell lines. Collectively, our results defined an improved Taspase1 consensus recognition sequence, Q(3)(F/I/L/V)(2)D(1)↓G(1)'X(2)'D(3)'D(4)', allowing the first genome-wide bioinformatic identification of the human Taspase1 degradome. Among the 27 most likely Taspase1 targets are cytoplasmic but also nuclear proteins, such as the upstream stimulatory factor 2 (USF2) or the nuclear RNA export factors 2/5 (NXF2/5). Cleavage site recognition and proteolytic processing of selected targets were verified in the context of the biosensor and for the full-length proteins. We provide novel mechanistic insights into the function and bona fide targets of Taspase1 allowing for a focused investigation of the (patho)biological relevance of this type 2 asparaginase.     

SDS-facilitated in vitro formation of a transmembrane B-type cytochrome is mediated by changes in local pH

The folding and stabilization of α-helical transmembrane proteins are still not well understood. Following cofactor binding to a membrane protein provides a convenient method to monitor the formation of appropriate native structures. We have analyzed the assembly and stability of the transmembrane cytochrome b₅₅₉′, which can be efficiently assembled in vitro from a heme-binding PsbF homo-dimer by combining free heme with the apo-cytochrome b₅₅₉′. Unfolding of the protein dissolved in the mild detergent dodecyl maltoside may be induced by addition of SDS, which at high concentrations leads to dimer dissociation. Surprisingly, absorption spectroscopy reveals that heme binding and cytochrome formation at pH 8.0 are optimal at intermediate SDS concentrations. Stopped-flow kinetics revealed that genuine conformational changes are involved in heme binding at these SDS concentrations. GPS (Global Protein folding State mapping) NMR measurements showed that optimal heme binding is intimately related to a change in the degree of histidine protonation. In the absence of SDS, the pH curve for heme binding is bell-shaped with an optimum at around pH 6-7. At alkaline pH values, the negative electrostatic potential of SDS lowers the local pH sufficiently to restore efficient heme binding, provided the amount of SDS needed for this does not denature the protein. Accordingly, the higher the pH value above 6-7, the more SDS is needed to improve heme binding, and this competes with the inherent tendency of SDS to dissociate cytochrome b₅₅₉′. Our work highlights that, in addition to its denaturing properties, SDS can affect protein functions by lowering the local pH.