A monoclonal antibody specific for prophase phosphorylation of histone deacetylase 1: a readout for early mitotic cells

Histone deacetylases (HDACs) are modification enzymes that regulate a plethora of biological processes. HDAC1, a crucial epigenetic modifier, is deregulated in cancer and subjected to a variety of post-translational modifications. Here, we describe the generation of a new monoclonal antibody that specifically recognizes a novel highly dynamic prophase phosphorylation of serine 406-HDAC1, providing a powerful tool for detecting early mitotic cells.     

p38/NF-kB-dependent expression of COX-2 during differentiation and inflammatory response of chondrocytes

Studying cartilage differentiation, we observed the emergence of inflammation-related proteins suggesting that a common pathway was activated in cartilage differentiation and inflammation. In the present paper, we investigated the expression pathway of the inflammation-related enzyme Cyclooxygenase-2 (COX-2) during differentiation and inflammatory response of the chondrocytic cell line MC615. Cells were cultured either as (i) proliferating prechondrogenic cells expressing type I collagen or (ii) differentiated hyperconfluent cells expressing Sox9 and type II collagen. The p38 and the NF-kB pathways were investigated in standard conditions and after inflammatory agents treatment. NF-kB was constitutively activated in differentiated cells. The activation level of NF-kB in differentiated cells was comparable to the level in proliferating cells treated with the inflammatory agent LPS. In both cases, p65 was bound to the NF-kB consensus sequence of COX-2 promoter. p38, constitutively activated in differentiated cells, was activated in proliferating cells by treatment with LPS or IL-1alpha. In stimulated proliferating cells the two pathways are connected since addition of the p38-specific inhibitor SB203580 inhibited p38 activation, significantly reduced NF-kB activation and repressed COX-2 synthesis indicating that p38 is upstream NF-kB activation and COX-2 synthesis. In differentiated cells, the treatment with the inflammatory agent neither enhance NF-kB activation, nor synthesis of COX-2 while the addition of SB203580 neither repressed activation of p38, nor COX-2 synthesis, suggesting a constitutive activation of a p38/NF-kB/COX2 pathway. Our data indicate that in chondrocytes, COX-2 is expressed via p38 activation/NF-kB recruitment during both differentiation and inflammatory response.     

Synaptophysin I selectively specifies the exocytic pathway of synaptobrevin 2/VAMP2

Biogenesis and recycling of synaptic vesicles are accompanied by sorting processes that preserve the molecular composition of the compartments involved. In the present study, we have addressed the targeting of synaptobrevin 2/VAMP2 (vesicle-associated membrane protein 2), a critical component of the synaptic vesicle--fusion machinery, in a heterotypic context where its sorting is not confounded by the presence of other neuron-specific molecules. Ectopically expressed synaptophysin I interacts with VAMP2 and alters its default surface targeting to a prominent vesicular distribution, with no effect on the targeting of other membrane proteins. Protein-protein interaction is not sufficient for the control of VAMP2 sorting, which is mediated by the C-terminal domain of synaptophysin I. Synaptophysin I directs the sorting of VAMP2 to vesicles before surface delivery, without influencing VAMP2 endocytosis. Consistent with this, dynamin and alpha-SNAP (soluble N-ethylmaleimide-sensitive fusion protein-attachment protein) mutants which block trafficking at the plasma membrane do not abrogate the effect of synaptophysin I on VAMP2 sorting. These results indicate that the sorting determinants of synaptic vesicle proteins can operate independently of a neuronal context and implicate the association of VAMP2 with synaptophysin I in the specification of the pathway of synaptic vesicle biogenesis.     

Lac repressor hinge flexibility and DNA looping: single molecule kinetics by tethered particle motion

The tethered particle motion (TPM) allows the direct detection of activity of a variety of biomolecules at the single molecule level. First pioneered for RNA polymerase, it has recently been applied also to other enzymes. In this work we employ TPM for a systematic investigation of the kinetics of DNA looping by wild-type Lac repressor (wt-LacI) and by hinge mutants Q60G and Q60 + 1. We implement a novel method for TPM data analysis to reliably measure the kinetics of loop formation and disruption and to quantify the effects of the protein hinge flexibility and of DNA loop strain on such kinetics. We demonstrate that the flexibility of the protein hinge has a profound effect on the lifetime of the looped state. Our measurements also show that the DNA bending energy plays a minor role on loop disruption kinetics, while a strong effect is seen on the kinetics of loop formation. These observations substantiate the growing number of theoretical studies aimed at characterizing the effects of DNA flexibility, tension and torsion on the kinetics of protein binding and dissociation, strengthening the idea that these mechanical factors in vivo may play an important role in the modulation of gene expression regulation.     

Brain delivery of AAV9 expressing an anti-PrP monovalent antibody delays prion disease in mice

Prion diseases are caused by a conformational modification of the cellular prion protein (PrP^C) into disease-specific forms, termed PrP^Sc, that have the ability to interact with PrP^C promoting its conversion to PrP^Sc. In vitro studies demonstrated that anti-PrP antibodies inhibit this process. In particular, the single chain variable fragment D18 antibody (scFvD18) showed high efficiency in curing chronically prion-infected cells. This molecule binds the PrP^C region involved in the interaction with PrP^Sc thus halting further prion formation. These findings prompted us to test the efficiency of scFvD18 in vivo. A recombinant Adeno-Associated Viral vector serotype 9 was used to deliver scFvD18 to the brain of mice that were subsequently infected by intraperitoneal route with the mouse-adapted scrapie strain RML. We found that the treatment was safe, prolonged the incubation time of scrapie-infected animals and decreased the burden of total proteinase-resistant PrP^Sc in the brain, suggesting that scFvD18 interferes with prion replication in vivo. This approach is relevant for designing new therapeutic strategies for prion diseases and other disorders characterized by protein misfolding.     

Expression Profiling of a Genetic Animal Model of Depression Reveals Novel Molecular Pathways Underlying Depressive-Like Behaviours

Background

The Flinders model is a validated genetic rat model of depression that exhibits a number of behavioural, neurochemical and pharmacological features consistent with those observed in human depression.

Principal Findings

In this study we have used genome-wide microarray expression profiling of the hippocampus and prefrontal/frontal cortex of Flinders Depression Sensitive (FSL) and control Flinders Depression Resistant (FRL) lines to understand molecular basis for the differences between the two lines. We profiled two independent cohorts of Flinders animals derived from the same colony six months apart, each cohort statistically powered to allow independent as well as combined analysis. Using this approach, we were able to validate using real-time-PCR a core set of gene expression differences that showed statistical significance in each of the temporally distinct cohorts, representing consistently maintained features of the model. Small but statistically significant increases were confirmed for cholinergic (chrm2, chrna7) and serotonergic receptors (Htr1a, Htr2a) in FSL rats consistent with known neurochemical changes in the model. Much larger gene changes were validated in a number of novel genes as exemplified by TMEM176A, which showed 35-fold enrichment in the cortex and 30-fold enrichment in hippocampus of FRL animals relative to FSL.

Conclusions

These data provide significant insights into the molecular differences underlying the Flinders model, and have potential relevance to broader depression research.