ProNGF induces p75-mediated death of oligodendrocytes following spinal cord injury

The neurotrophin receptor p75 is induced by various injuries to the nervous system, but its role after injury has remained unclear. Here, we report that p75 is required for the death of oligodendrocytes following spinal cord injury, and its action is mediated mainly by proNGF. Oligodendrocytes undergoing apoptosis expressed p75, and the absence of p75 resulted in a decrease in the number of apoptotic oligodendrocytes and increased survival of oligodendrocytes. ProNGF is likely responsible for activating p75 in vivo, since the proNGF from the injured spinal cord induced apoptosis among p75(+/+), but not among p75(-/-), oligodendrocytes in culture, and its action was blocked by proNGF-specific antibody. Together, these data suggest that the role of proNGF is to eliminate damaged cells by activating the apoptotic machinery of p75 after injury.     

Parkin reverses TDP‐43‐induced cell death and failure of amino acid homeostasis

The E3 ubiquitin ligase Parkin plays a central role in the pathogenesis of many neurodegenerative diseases. Parkin promotes specific ubiquitination and affects the localization of transactivation response DNA‐binding protein 43 (TDP‐43), which controls the translation of thousands of mRNAs. Here we tested the effects of lentiviral Parkin and TDP‐43 expression on amino acid metabolism in the rat motor cortex using high frequency ¹³C NMR spectroscopy. TDP‐43 expression increased glutamate levels, decreased the levels of other amino acids, including glutamine, aspartate, leucine and isoleucine, and impaired mitochondrial tricarboxylic acid cycle. TDP‐43 induced lactate accumulation and altered the balance between excitatory (glutamate) and inhibitory (GABA) neurotransmitters. Parkin restored amino acid levels, neurotransmitter balance and tricarboxylic acid cycle metabolism, rescuing neurons from TDP‐43‐induced apoptotic death. Furthermore, TDP‐43 expression led to an increase in 4E‐BP levels, perhaps altering translational control and deregulating amino acid synthesis; while Parkin reversed the effects of TDP‐43 on the 4E‐BP signaling pathway. Taken together, these data suggest that Parkin may affect TDP‐43 localization and mitigate its effects on 4E‐BP signaling and loss of amino acid homeostasis.

     

Solutions in microbiome engineering: prioritizing barriers to organism establishment

Microbiome engineering is increasingly being employed as a solution to challenges in health, agriculture, and climate. Often manipulation involves inoculation of new microbes designed to improve function into a preexisting microbial community. Despite, increased efforts in microbiome engineering inoculants frequently fail to establish and/or confer long-lasting modifications on ecosystem function. We posit that one underlying cause of these shortfalls is the failure to consider barriers to organism establishment. This is a key challenge and focus of macroecology research, specifically invasion biology and restoration ecology. We adopt a framework from invasion biology that summarizes establishment barriers in three categories: (1) propagule pressure, (2) environmental filtering, and (3) biotic interactions factors. We suggest that biotic interactions is the most neglected factor in microbiome engineering research, and we recommend a number of actions to accelerate engineering solutions.Subject terms: Community ecology, Microbial ecology

Microbiome engineering is a rapidly evolving frontier for solutions to improve human health, agricultural productivity, and climate management. Microbiome engineering seeks to improve the function of an ecosystem by manipulating the composition of microbes. Two major challenges for successful microbiome engineering are (1) the design of a microbiome with improved function and (2) the establishment of an improved microbiome in a recipient system of interest. While multiple articles and reviews have addressed functional design [1–3], microbiome establishment has received less attention. Here, we propose a strategy to improve microbiome engineering by focusing on microbial establishment and leveraging insights from macrobial ecology.Two general engineering strategies are to manipulate indigenous microbes [4] or to introduce new members [5]. The latter involves the design and delivery of inoculants (a.k.a., probiotics in medical and agricultural arenas) and is a rapidly growing biotechnology sector. In their most general form, both strategies have been practiced crudely for thousands of years in human health [6] and agriculture [7]. However, despite current technical advances, inoculants frequently still fail to establish or confer long-lasting (months to years) modifications to ecosystem function [8]. We argue that this repeated failure is in part driven by lack of emphasis on establishment of inoculants.The problem of organism establishment in recipient ecosystems is not unique to microbiome engineering; it has roots in macrobiology, particularly invasion biology and restoration ecology. We propose that adopting a cross-disciplinary conceptual framework to identify barriers to organism establishment, and then prioritizing these barriers through targeted research will accelerate successful microbiome engineering. In addition, recognizing differences in terminology and experimental design within and across disciplines will facilitate research integration across diverse ecosystems and scales. The components of a more holistic strategy are discussed below.     

Ubiquitination Increases Parkin Activity to Promote Autophagic α-Synuclein Clearance

Parkinson’s disease (PD) is a movement disorder associated with genetic and age related causes. Although autosomal recessive early onset PD linked to parkin mutations does not exhibit α-Synuclein accumulation, while autosomal dominant and sporadic PD manifest with α-Synuclein inclusions, loss of dopaminergic substantia nigra neurons is a common denominator in PD. Here we show that decreased parkin ubiquitination and loss of parkin stability impair interaction with Beclin-1 and alter α-Synuclein degradation, leading to death of dopaminergic neurons. Tyrosine kinase inhibition increases parkin ubiquitination and interaction with Beclin-1, promoting autophagic α-Synuclein clearance and nigral neuron survival. However, loss of parkin via deletion increases α-Synuclein in the blood compared to the brain, suggesting that functional parkin prevents α-Synuclein release into the blood. These studies demonstrate that parkin ubiquitination affects its protein stability and E3 ligase activity, possibly leading to α-Synuclein sequestration and subsequent clearance.     

Evaluation of density gradient separation methods

A new method for evaluating the effectiveness of isooynic separation processes is developed and explored. This technique is designed to measure the ability of a separation technique to attain the goals of a sorting process. The performance of a separation process is expressed in terms of an inconsistency number, I, whose values ranges from zero to unity. Processes which function perfectly are characterized by an I value of zero. Separation processes which subdivide a sample are characterized by an I value of unity. The validity of using I to measure the performance of separation processes was established by demonstrating that alterations in the performance of a well characterized separation technique were fully reflected by changes in the I value for the process. The capacity of four different techniques for ordering red cells with respect to their density was then shown to lie in a definite hierarchy. This hierarchy can be expressed as: Murphy technique (I = 0.21) > albumin density gradient (I = 0.43) > Stractan density gradient I = 0.53) > Percoll density gradient (I = 0.73). The performance of these techniques was found to be dependent on the exact operating conditions employed and the specific fraction of red cells isolated.     

Interaction between the human cytomegalovirus UL82 gene product (pp71) and hDaxx regulates immediate-early gene expression and viral replication

The human cytomegalovirus UL82-encoded pp71 protein is required for efficient virus replication and immediate-early gene expression when cells are infected at a low multiplicity. Functions attributed to pp71 include the ability to enhance the infectivity of viral DNA, bind to and target hypophosphorylated Rb family member proteins for degradation, drive quiescent cells into the cell cycle, and bind to the cellular protein hDaxx. Using UL82 mutant viruses, we demonstrate that the LXCXD motif within pp71 is not necessary for efficient virus replication in fibroblasts, suggesting that pp71's ability to degrade hypophosphorylated Rb family members and induce quiescent cells into the cell cycle is not responsible for the growth defect associated with a UL82 deletion mutant. However, UL82 mutants that cannot bind to hDaxx are unable to induce immediate-early gene expression and are severely attenuated for viral replication. These results indicate that the interaction between the human cytomegalovirus UL82 gene product (pp71) and hDaxx regulates immediate-early gene expression and viral replication.     

Effect of human cytomegalovirus on expression of MHC class I-related chains A

The MHC-encoded MHC class I-related chains A (MICA) glycoproteins are known to enhance the functions of NK and T cells by ligating the stimulating receptor NKG2D and appear to play an important role in host defense. Human CMV (HCMV) evades the immune response in many different ways, but has not previously been found to down-regulate MICA. We have found that a common form of MICA, which has a nucleotide insertion in exon 5 corresponding to the transmembrane region and no cytoplasmic tail, was increased on the surface of fibroblasts HFS-13 compared with the mock-infected sample of the same cells that had been cultured to confluence. However, an astrocytoma cell line, U373, which has a full-length variant of MICA, showed that the expression of MICA was decreased after HCMV infection. Retroviral transduction of different MICA alleles into fibroblasts HFF-D, which express no MICA of their own, established that full-length MICA was down-regulated by HCMV, and the truncated form was not. Fibroblasts with decreased MICA due to HCMV infection were found to be protected from NK cell killing, whereas in the presence of the truncated form of MICA, the virus-infected cells were destroyed. Thus, the truncated form of MICA, which is the most common, has a mutation that allows it to persist on the surface and hinder efforts of the virus to evade the immune response.