Acid-induced conformational changes in phosphoglucose isomerase result in its increased cell surface association and deposition on fibronectin fibrils

Phosphoglucose isomerase (PGI) is a glycolytic enzyme that exhibits extracellular cytokine activity as autocrine motility factor, neuroleukin, and maturation factor and that has been recently implicated as an autoantigen in rheumatoid arthritis. In contrast to its receptor-mediated endocytosis at neutral pH, addition of 25 microg/ml of either Alexa 568- or FITC-conjugated PGI to NIH-3T3 cells at progressively acid pH results in its quantitatively increased association with cell surface fibrillar structures that is particularly evident at pH 5. A similar pH-dependent cell surface association of PGI is observed for first passage human chondrocytes obtained from osteoarthritic joints. At acid pH, PGI colocalizes with fibronectin fibrils, and this association occurs directly upon addition of PGI to the cells. In contrast to the receptor-mediated endocytosis of PGI, fibril association of 25 microg/ml PGI at pH 5 is not competed with an excess (2 mg/ml) of unlabeled PGI. PGI binding at acid pH is therefore neither saturable nor mediated by its receptor. PGI is enzymatically active as a dimer and we show here by non-denaturing gel electrophoresis as well as by glutaraldehyde cross-linking that it exists at neutral pH in a tetrameric form. Increasingly acid pH results in the appearance of PGI monomers that correlates directly with its enhanced cell surface association. However, glutaraldehyde cross-linked PGI is endocytosed at neutral pH and still exhibits enhanced cell surface binding at pH 5. Circular dichroism analysis revealed pH-dependent changes in the near but not the far UV spectra indicating that the tertiary structure of the protein is specifically altered at pH 5. Conformational changes of PGI and exposure of the monomer-monomer interface under acidic conditions, such as those encountered in the synovial fluid of arthritic joints, could therefore result in its deposition on the surface of joints and the induction of an autoimmune response.     

CoA Synthase is in complex with p85αPI3K and affects PI3K signaling pathway

The complex interplay between cellular signaling and metabolism in eukaryotic cells just start to emerge. Coenzyme A (CoA) and its derivatives play a key role in cell metabolism and also participate in regulatory processes. CoA Synthase (CoASy) is a mitochondria-associated enzyme which mediates two final stages of de novo CoA biosynthesis. Here, we report that CoASy is involved in signaling events in the cell and forms a functional complex with p85αPI3K in vivo. Importantly, observed interaction of endogenous CoASy and p85αPI3K is regulated in a growth factor dependent manner. Surprisingly, both catalytic p110α and regulatory p85α subunits of PI3K were detected in mitochondrial fraction where mitochondria-localized p85αPI3K was found in complex with CoASy. Unexpectedly, significant changes of PI3K signaling pathway activity were observed in experiments with siRNA-mediated CoASy knockdown pointing on the role of CoA biosynthetic pathway in signal transduction.     

Symbols are not uniquely human

Modern semiotics is a branch of logics that formally defines symbol-based communication. In recent years, the semiotic classification of signs has been invoked to support the notion that symbols are uniquely human. Here we show that alarm-calls such as those used by African vervet monkeys (Cercopithecus aethiops), logically satisfy the semiotic definition of symbol. We also show that the acquisition of vocal symbols in vervet monkeys can be successfully simulated by a computer program based on minimal semiotic and neurobiological constraints. The simulations indicate that learning depends on the tutor-predator ratio, and that apprentice-generated auditory mistakes in vocal symbol interpretation have little effect on the learning rates of apprentices (up to 80% of mistakes are tolerated). In contrast, just 10% of apprentice-generated visual mistakes in predator identification will prevent any vocal symbol to be correctly associated with a predator call in a stable manner. Tutor unreliability was also deleterious to vocal symbol learning: a mere 5% of "lying" tutors were able to completely disrupt symbol learning, invariably leading to the acquisition of incorrect associations by apprentices. Our investigation corroborates the existence of vocal symbols in a non-human species, and indicates that symbolic competence emerges spontaneously from classical associative learning mechanisms when the conditioned stimuli are self-generated, arbitrary and socially efficacious. We propose that more exclusive properties of human language, such as syntax, may derive from the evolution of higher-order domains for neural association, more removed from both the sensory input and the motor output, able to support the gradual complexification of grammatical categories into syntax.     

Detection of Anaplasma bovis in an undescribed tick species collected from the eastern rock sengi Elephantulus myurus

Ticks are important vectors of numerous pathogens causing illness, fatalities, and economic loss worldwide. Infectious disease episodes are increasing, and novel tick-borne pathogens are described frequently. Identification of novel reservoir hosts and vectors of tick-borne pathogens is essential if control measures are to be successful. In South Africa, the eastern rock sengi, Elephantulus myurus , hosts a number of tick species of veterinary importance. Despite this, there remains a paucity of information regarding the tick fauna of this species, the pathogen associations of ticks that it hosts, and its role as a reservoir host of tick-borne pathogens. The current study documents the tick fauna of E. myurus and sympatric small mammal species in Limpopo Province, South Africa. The pathogen associations of ticks hosted by elephant shrews were also investigated by PCR screening of engorged nymphs for a broad range of bacterial and protozoan tick-borne infections, including Borrelia burgdorferi sensu lato and members of Apicomplexa and the order Rickettsiales. There were marked differences in tick species and abundance among host species. Elephantulus myurus was heavily, and predominantly, parasitized by an as-yet undescribed tick species that we identify as Rhipicephalus sp. near warburtoni. PCR and sequence analysis revealed the presence of Anaplasma bovis in this tick species, which may have consequences for livestock production and conservation efforts in the area where this tick species occurs.     

Generation of dendritic Ca2+ oscillations as a consequence of altered ryanodine receptor function in AD neurons

Ryanodine receptor (RyR)-mediated Ca(2+) dysregulation is associated with Alzheimer's disease (AD) neuropathology. Using 2-photon Ca(2+) imaging and patch clamp recordings in brain slice preparations from young 3xTg-AD and NonTg control mice, we recently demonstrated that RyR-mediated Ca(2+) -induced Ca(2+) release (CICR) is substantially increased within dendrites from AD neurons, such that synaptic stimulation alone is sufficient to generate aberrant CICR. We also observed supra-additive Ca(2+) release upon coincident RyR activation with synaptic stimulation in 3xTg-AD mice. Here, we describe an additional observed phenomenon: generation of patterned Ca(2+) oscillations in the spines and dendrites from AD neurons upon coincident RyR and synaptic stimulation. As the temporal entrainment of Ca(2+) signals influences many downstream cellular and synaptic functions, these abnormal oscillatory patterns may be associated with the structural and functional breakdown of synapses in AD.     

Azido analogs of neuroactive steroids

Analogs of pregnanolone (3α-hydroxy-5β-pregnan-20-one), modified in position 17 were prepared. Compounds with 20-keto pregnane side chain replaced completely by azide (17α- and 17β-azido-5β-androstan-3α-ol), compounds with its part replaced (20-azido-21-nor-5β-pregnan-3α-ol), and compounds with keto group only replaced ((20R)- and (20S)-20-azido-5β-pregnan-3α-ol) were synthesized using tosylate displacements with sodium azide or Mitsunobu reaction with azoimide. All five azido steroids were converted into corresponding sulfates. Subsequent tests for inhibition of glutamate induced response on NMDA receptors revealed that modification of pregnanolone sulfate side chain with azide did not disturb the activity and some of sulfates tested were more active than parent compound.     

Alloimmune response results in expansion of autoreactive donor CD4+ T cells in transplants that can mediate chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) is considered an autoimmune-like disease mediated by donor CD4(+) T cells, but the origin of the autoreactive T cells is still controversial. In this article, we report that the transplantation of DBA/2 donor spleen cells into thymectomized MHC-matched allogeneic BALB/c recipients induced autoimmune-like cGVHD, although not in control syngeneic DBA/2 recipients. The donor-type CD4(+) T cells from the former but not the latter recipients induced autoimmune-like manifestations in secondary allogeneic BALB/c as well as syngeneic DBA/2 recipients. Transfer of donor-type CD4(+) T cells from secondary DBA/2 recipients with disease into syngeneic donor-type or allogeneic host-type tertiary recipients propagated autoimmune-like manifestations in both. Furthermore, TCR spectratyping revealed that the clonal expansion of the autoreactive CD4(+) T cells in cGVHD recipients was initiated by an alloimmune response. Finally, hybridoma CD4(+) T clones derived from DBA/2 recipients with disease proliferated similarly in response to stimulation by syngeneic donor-type or allogeneic host-type dendritic cells. These results demonstrate that the autoimmune-like manifestations in cGVHD can be mediated by a population of donor CD4(+) T cells in transplants that simultaneously recognize Ags presented by both donor and host APCs.