The extracellular release of Schistosoma mansoni HMGB1 nuclear protein is mediated by acetylation.

Schistosoma mansoni HMGB1 (SmHMGB1) was revealed to be a substrate for the parasite histone acetyltransferases SmGCN5 and SmCBP1. We found that full-length SmHMGB1, as well as its HMG-box B (but not HMG-box A) were acetylated in vitro by SmGCN5 and SmCBP1. However, SmCBP1 was able to acetylate both substrates more efficiently than SmGCN5. Interestingly, the removal of the C-terminal acidic tail of SmHMGB1 (SmHMGB1DeltaC) resulted in increased acetylation of the protein. We showed by mammalian cell transfection assays that SmHMGB1 and SmHMGB1DeltaC were transported from the nucleus to the cytoplasm after sodium butyrate (NaB) treatment. Importantly, after NaB treatment, SmHMGB1 was also present outside the cell. Together, our data suggest that acetylation of SmHMGB1 plays a role in cellular trafficking, culminating with its secretion to the extracellular milieu. The possible role of SmHMGB1 acetylation in the pathogenesis of schistosomiasis is discussed.

Protein acetylation sites mediated by Schistosoma mansoni GCN5.

The transcriptional co-activator GCN5, a histone acetyltransferase (HAT), is part of large multimeric complexes that are required for chromatin remodeling and transcription activation. As in other eukaryotes, the DNA from the parasite Schistosome mansoni is organized into nucleosomes and the genome encodes components of chromatin-remodeling complexes. Using a series of synthetic peptides we determined that Lys-14 of histone H3 was acetylated by the recombinant SmGCN5-HAT domain. SmGCN5 was also able to acetylate schistosome non-histone proteins, such as the nuclear receptors SmRXR1 and SmNR1, and the co-activator SmNCoA-62. Electron microscopy revealed the presence of SmGCN5 protein in the nuclei of vitelline cells. Within the nucleus, SmGCN5 was found to be located in interchromatin granule clusters (IGCs), which are transcriptionally active structures. The data suggest that SmGCN5 is involved in transcription activation.

Cloning of SmNCoA-62, a novel nuclear receptor co-activator from Schistosoma mansoni: assembly of a complex with a SmRXR1/SmNR1 heterodimer, SmGCN5 and SmCBP1.

The Schistosoma mansoni nuclear receptors (NR) SmRXR1 and SmNR1 have recently been shown to form a heterodimer and to bind to canonic hormone response DNA elements. Recruitment of co-regulatory proteins to NRs is required for their transcriptional and biological activities. Here, we cloned a novel S. mansoni NR co-activator, SmNCoA-62. SmNCoA-62 is highly homologous to the human Vitamin D receptor co-activator NCoA62/SKIP. SmNCoA-62 contains the SNW nuclear receptor interaction domain and a putative C-terminus transactivation domain. By using in vitro pull-down assays, we fully mapped the interaction domains of S. mansoni NR co-activators, SmNCoA-62, SmGCN5 and SmCBP1 with SmRXR1 and SmNR1, as well as the domains that mediate interactions amongst the co-activators themselves. By mutagenesis analysis, we showed that SmCBP1 LxxLL motif 2 and LxxLL motif 3, but not LxxLL motif 1, were essential to mediate the interactions of SmCBP1 with the EF domains of SmRXR1 and SmNR1. Histone acetyltransferases SmGCN5 and SmCBP1 specifically acetylated the C/D domains of SmRXR1 and SmNR1. In addition, two acetylation sites of SmNR1 were identified. SmGCN5 and SmCBP1 also acetylated SmNCoA-62 but with significant differences in their acetylation activities. Using gel shift analysis, we were able to demonstrate, in vitro, the assembly of the co-activators on the SmRXR1/SmNR1 heterodimer bound to DNA. LxxLL motifs 2 and 3 of SmCBP1 seemed to play a crucial role for the assembly of the co-activators to the DNA-bound SmRXR1/SmNR1 heterodimer.

Analysis of Myelinating Schwann Cells in Human Skin Biopsies.

The human skin is richly innervated by nerve fibers of different calibers and functions, including thickly myelinated large fibers that act as afferents for mechanoreceptors in the dermal papillae. Skin biopsies offer minimally invasive access to these myelinated fibers, in which each internode represents an individual myelinating Schwann cell. Using this approach, human myelinated nerve fibers can be analyzed by several methods, including immunostaining, morphometric and ultrastructural analysis, and molecular biology techniques. This analysis can reveal important aspects of human Schwann cell biology in health and disease, such as in the case of demyelinating neuropathies. This technique has revealed Schwann cell phenotypes in Charcot-Marie-Tooth disease type 1 and acquired inflammatory neuropathies.

Altered oxygen metabolism associated to neurogenesis of induced pluripotent stem cells derived from a schizophrenic patient.

Schizophrenia has been defined as a neurodevelopmental disease that causes changes in the process of thoughts, perceptions, and emotions, usually leading to a mental deterioration and affective blunting. Studies have shown altered cell respiration and oxidative stress response in schizophrenia; however, most of the knowledge has been acquired from postmortem brain analyses or from nonneural cells. Here we describe that neural cells, derived from induced pluripotent stem cells generated from skin fibroblasts of a schizophrenic patient, presented a twofold increase in extramitochondrial oxygen consumption as well as elevated levels of reactive oxygen species (ROS), when compared to controls. This difference in ROS levels was reverted by the mood stabilizer valproic acid. Our model shows evidence that metabolic changes occurring during neurogenesis are associated with schizophrenia, contributing to a better understanding of the development of the disease and highlighting potential targets for treatment and drug screening.

The dengue vector Aedes aegypti contains a functional high mobility group box 1 (HMGB1) protein with a unique regulatory C-terminus.

The mosquito Aedes aegypti can spread the dengue, chikungunya and yellow fever viruses. Thus, the search for key molecules involved in the mosquito survival represents today a promising vector control strategy. High Mobility Group Box (HMGB) proteins are essential nuclear factors that maintain the high-order structure of chromatin, keeping eukaryotic cells viable. Outside the nucleus, secreted HMGB proteins could alert the innate immune system to foreign antigens and trigger the initiation of host defenses. In this work, we cloned and functionally characterized the HMGB1 protein from Aedes aegypti (AaHMGB1). The AaHMGB1 protein typically consists of two HMG-box DNA binding domains and an acidic C-terminus. Interestingly, AaHMGB1 contains a unique alanine/glutamine-rich (AQ-rich) C-terminal region that seems to be exclusive of dipteran HMGB proteins. AaHMGB1 is localized to the cell nucleus, mainly associated with heterochromatin. Circular dichroism analyses of AaHMGB1 or the C-terminal truncated proteins revealed α-helical structures. We showed that AaHMGB1 can effectively bind and change the topology of DNA, and that the AQ-rich and the C-terminal acidic regions can modulate its ability to promote DNA supercoiling, as well as its preference to bind supercoiled DNA. AaHMGB1 is phosphorylated by PKA and PKC, but not by CK2. Importantly, phosphorylation of AaHMGB1 by PKA or PKC completely abolishes its DNA bending activity. Thus, our study shows that a functional HMGB1 protein occurs in Aedes aegypt and we provide the first description of a HMGB1 protein containing an AQ-rich regulatory C-terminus.