Biodegradation of aliphatic-aromatic copolyesters by Thermomonospora fusca and other thermophilic compost isolates

Random aliphatic-aromatic copolyesters synthesized from 1,4-butanediol, adipic acid, and terephthalic acid (BTA) have excellent thermal and mechanical properties and are biodegradable by mixed cultures (e.g., in compost). Over 20 BTA-degrading strains were isolated by using compost as a microbial source. Among these microorganisms, thermophilic actinomycetes obviously play an outstanding role and appear to dominate the initial degradation step. Two actinomycete strains exhibited about 20-fold higher BTA degradation rates than usually observed in a common compost test. These isolates were identified as Thermomonospora fusca strains. They appeared to be particularly suitable for establishment of rapid degradation tests and were used in comparative studies on the biodegradation of various polyesters.

Converging pathways in the occurrence of endoplasmic reticulum (ER) stress in Huntington's disease

A variety of neurological diseases including Huntington's disease (HD), Alzheimer's disease and Parkinson's disease share common neuropathology, primarily featuring the presence of abnormal protein inclusions containing specific misfolded proteins. Mutations leading to expansion of a poly-glutamine track in Huntingtin cause HD, and trigger its misfolding and aggregation. Recent evidence indicates that alterations in the secretory pathway, in particular the endoplasmic reticulum (ER), are emerging features of HD. Although it is not clear how cytoplasmic/nuclear located mutant Huntingtin alters the function of the ER, several reports indicate that mutant Huntingtin affects many essential processes related to the secretory pathway, including inhibition of ER-associated degradation, altered ER/Golgi vesicular trafficking and axonal transport, disrupted autophagy and abnormal ER calcium homeostasis. All these alterations are predicted to have a common pathological outcome associated to disturbance of protein folding and maturation pathways at the ER, generating chronic ER stress and neuronal dysfunction. Here, we review recent evidence involving ER stress in HD pathogenesis and discuss possible therapeutic strategies to target organelle function in the context of disease.

Structure, organization and characterization of the gene cluster involved in the production of microcin E492, a channel-forming bacteriocin

Microcin E492 is a low-molecular-weight, channel-forming bacteriocin produced and excreted by Klebsiella pneumoniae RYC492. A 13 kb chromosomal DNA fragment from K. pneumoniae RYC492 was sequenced, and it was demonstrated by random Tn5 mutagenesis that most of this segment, which has at least 10 cistrons, is needed for the production of active microcin and its immunity protein. Genes mceG and mceH correspond to an ABC exporter and its accessory protein, respectively, and they are closely related to the colicin V ABC export system. The microcin E492 system also requires the product of gene mceF as an additional factor for export. Despite the fact that this bacteriocin lacks post-translational modifications, genes mceC, mceI and mceJ are needed for the production of active microcin. Genes mceC and mceI are homologous to a glycosyl transferase and acyltransferase, respectively, whereas mceJ has no known homologue. Mutants in these three genes secrete an inactive form of microcin, able to form ion channels in a phospholipidic bilayer, indicating that the mutation of these microcin genes does not alter the process of membrane insertion. On the other hand, microcin isolated from mutants in genes mceC and mceJ has a lethal effect when incubated with spheroplasts of sensitive cells, indicating that the microcin defects in these mutants are likely to alter receptor recognition at the outer membrane. A model for synthesis and export is proposed as well as a novel maturation pathway that would involve conformational changes to explain the production of active microcin E492.

Nonselective cation channels as effectors of free radical-induced rat liver cell necrosis

Necrosis, as opposed to apoptosis, is recognized as a nonspecific cell death that induces tissue inflammation and is preceded by cell edema. In non-neuronal cells, the latter has been explained by defective outward pumping of Na(+) caused by metabolic depletion or by increased Na(+) influx via membrane transporters. Here we describe a novel mechanism of swelling and necrosis; namely the influx of Na(+) through oxidative stress-activated nonselective cation channels. Exposure of liver epithelial Clone 9 cells to the free-radical donors calphostin C or menadione induced the rapid activation of an approximately 16-pS nonselective cation channel (NSCC). Blockage of this conductance with flufenamic acid protected the cells against swelling, calcium overload, and necrosis. Protection was also achieved by Gd(3+), an inhibitor of stretch-activated cation channels, or by isosmotic replacement of extracellular Na(+) with N-methyl-D-glucamine. It is proposed that NSCCs, which are ubiquitous although largely inactive in healthy cells, become activated under severe oxidative stress. The ensuing influx of Na(+) initiates a positive feedback of metabolic and electrolytic disturbances leading cells to their necrotic demise.

Protein misfolding and disease: the case of prion disorders

Recent findings strongly support the hypothesis that diverse human disorders, including the most common neurodegenerative diseases, arise from misfolding and aggregation of an underlying protein. Despite the good evidence for the involvement of protein misfolding in disease pathogenesis, the mechanism by which protein conformational changes participate in the disease is still unclear. Among the best-studied diseases of this group are the transmissible spongiform encephalopathies or prion-related disorders, in which misfolding of the normal prion protein plays a key role in the disease. In this article we review recent data on the link between prion protein misfolding and the pathogensis of spongiform encephalopathies.

Adaptive preconditioning in neurological diseases - therapeutic insights from proteostatic perturbations

In neurological disorders, both acute and chronic neural stress can disrupt cellular proteostasis, resulting in the generation of pathological protein. However in most cases, neurons adapt to these proteostatic perturbations by activating a range of cellular protective and repair responses, thus maintaining cell function. These interconnected adaptive mechanisms comprise a 'proteostasis network' and include the unfolded protein response, the ubiquitin proteasome system and autophagy. Interestingly, several recent studies have shown that these adaptive responses can be stimulated by preconditioning treatments, which confer resistance to a subsequent toxic challenge - the phenomenon known as hormesis. In this review we discuss the impact of adaptive stress responses stimulated in diverse human neuropathologies including Parkinson׳s disease, Wolfram syndrome, brain ischemia, and brain cancer. Further, we examine how these responses and the molecular pathways they recruit might be exploited for therapeutic gain. This article is part of a Special Issue entitled SI:ER stress.

Network approach identifies Pacer as an autophagy protein involved in ALS pathogenesis

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a multifactorial fatal motoneuron disease without a cure. Ten percent of ALS cases can be pointed to a clear genetic cause, while the remaining 90% is classified as sporadic. Our study was aimed to uncover new connections within the ALS network through a bioinformatic approach, by which we identified C13orf18, recently named Pacer, as a new component of the autophagic machinery and potentially involved in ALS pathogenesis.

METHODS

Initially, we identified Pacer using a network-based bioinformatic analysis. Expression of Pacer was then investigated in vivo using spinal cord tissue from two ALS mouse models (SOD1^G93A and TDP43^A315T) and sporadic ALS patients. Mechanistic studies were performed in cell culture using the mouse motoneuron cell line NSC34. Loss of function of Pacer was achieved by knockdown using short-hairpin constructs. The effect of Pacer repression was investigated in the context of autophagy, SOD1 aggregation, and neuronal death.

RESULTS

Using an unbiased network-based approach, we integrated all available ALS data to identify new functional interactions involved in ALS pathogenesis. We found that Pacer associates to an ALS-specific subnetwork composed of components of the autophagy pathway, one of the main cellular processes affected in the disease. Interestingly, we found that Pacer levels are significantly reduced in spinal cord tissue from sporadic ALS patients and in tissues from two ALS mouse models. In vitro, Pacer deficiency lead to impaired autophagy and accumulation of ALS-associated protein aggregates, which correlated with the induction of cell death.

CONCLUSIONS

This study, therefore, identifies Pacer as a new regulator of proteostasis associated with ALS pathology.

A Molecular Reporter for Monitoring Autophagic Flux in Nervous System In Vivo

The relevance of autophagy in neuronal health has been extensively reported in a plethora of conditions affecting the nervous system, such as neurodegenerative diseases, cancer, diabetes, and tissue injury, where altered autophagic activity may contribute to the pathological process. Autophagy is a dynamic pathway involving the formation of a membrane surrounding and enclosing cargoes that are delivered to lysosomal compartments for degradation. Cargoes can include large protein aggregates, organelles, or even pathogens. Traditionally, autophagy assessment relies on the measurement of LC3-II protein levels or the visualization of LC3-positive puncta. However, these approaches represent a static measurement of autophagy markers, making difficult the dissection of the actual changes in the autophagy process (activation, inhibition, or no effects), due to the dynamic regulation of LC3 viral levels. To circumvent this limitation, we previously developed an adeno-associated vector (AAV) to deliver a molecular autophagy sensor to the neuronal compartment in vivo. Here, we describe the detailed design and methods to use an engineered AAV harboring the monomeric tandem mCherry-GFP-LC3 to determine autophagic fluxes in the nervous system. Key methodological details to succeed in the use of this reporter are provided.

Prion Function and Pathophysiology in Non-Mammalian Models

More than thirty years have passed since the discovery of the prion protein (PrP) and its causative role in transmissible spongiform encephalopathy. Since a combination of both gain- and loss-of-function mechanisms may underlay prion pathogenesis, understanding the physiological role of PrP may give important clues about disease mechanisms. Historically, the primary strategy for prion research has involved the use of human tissue, cell cultures and mammalian animal models. Nevertheless, experimental difficulties of in vivo studies and controversial observations obtained in these systems have stimulated the search for alternative animal models. PrPC is highly conserved in mammals, and PrPC-related orthologs are expressed in zebrafish, a vertebrate model organism suitable to study the mechanisms associated with human diseases. Invertebrate models, as they do not express PrPC have served to investigate the neurotoxic mechanisms of mammalian PrP. Here we overview most recent advances in the study of PrP function in normal and pathogenic conditions based on non-mammalian studies, highlighting the contribution of zebrafish, fly and worms to our current understanding of PrP biology.