Autophagic turnover of intracellular constituents is critical for cellular housekeeping, nutrient recycling, and various aspects of growth and development in eukaryotes. Here we show that autophagy ...impacts the other major degradative route involving the ubiquitin-proteasome system by eliminating 26S proteasomes, a process we termed proteaphagy. Using Arabidopsis proteasomes tagged with GFP, we observed their deposition into vacuoles via a route requiring components of the autophagy machinery. This transport can be initiated separately by nitrogen starvation and chemical or genetic inhibition of the proteasome, implying distinct induction mechanisms. Proteasome inhibition stimulates comprehensive ubiquitylation of the complex, with the ensuing proteaphagy requiring the proteasome subunit RPN10, which can simultaneously bind both ATG8 and ubiquitin. Collectively, we propose that Arabidopsis RPN10 acts as a selective autophagy receptor that targets inactive 26S proteasomes by concurrent interactions with ubiquitylated proteasome subunits/targets and lipidated ATG8 lining the enveloping autophagic membranes.
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•The Arabidopsis 26S proteasome is degraded by ATG8-mediated autophagy•This degradation is induced by nitrogen starvation and proteasome inhibition•Proteasome inhibition stimulates extensive ubiquitylation of the complex•RPN10 acts as a proteaphagy receptor by binding ubiquitylated proteasomes and ATG8
Marshall et al. have revealed that the 26S proteasome is degraded by ATG8-mediated autophagy in Arabidopsis, a process stimulated separately by nitrogen starvation and chemical or genetic proteasome inhibition. Additionally, they showed that inhibited proteasomes become extensively ubiquitylated and that subsequent autophagic turnover is mediated by the ubiquitin receptor RPN10.
Although transplantation of c-kit+ cardiac stem cells (CSCs) has been shown to alleviate left ventricular (LV) dysfunction induced by myocardial infarction (MI), the number of exogenous CSCs ...remaining in the recipient heart following transplantation and their mechanism of action remain unclear. We have previously developed a highly sensitive and accurate method to quantify the absolute number of male murine CSCs in female recipient organs after transplantation. In the present study, we used this method to monitor the number of donor CSCs in the recipient heart after intracoronary infusion. Female mice underwent a 60-min coronary occlusion followed by reperfusion; 2 days later, 100,000 c-kit+/lin- syngeneic male mouse CSCs were infused intracoronarily. Only 12.7% of the male CSCs present in the heart immediately (5 min) after infusion were still present in the heart at 24 h, and their number declined rapidly thereafter. By 35 days after infusion, only ∼ 1,000 male CSCs were found in the heart. Significant numbers of male CSCs were found in the lungs and kidneys, but only in the first 24 h. The number of CSCs in the lungs increased between 5 min and 24 h after infusion, indicating recirculation of CSCs initially retained in other organs. Despite the low retention and rapid disappearance of CSCs from the recipient heart, intracoronary delivery of CSCs significantly improved LV function at 35 days (Millar catheter). These results suggest that direct differentiation of CSCs alone cannot account for the beneficial effects of CSCs on LV function; therefore, paracrine effects must be the major mechanism. The demonstration that functional improvement is dissociated from survival of transplanted cells has major implications for our understanding of cell therapy. In addition, this new quantitative method of stem cell measurement will be useful in testing approaches of enhancing CSC engraftment and survival after transplantation.
Streptomyces are best known for producing antimicrobial secondary metabolites, but they are also recognized for their contributions to biomass utilization. Despite their importance to carbon cycling ...in terrestrial ecosystems, our understanding of the cellulolytic ability of Streptomyces is currently limited to a few soil-isolates. Here, we demonstrate the biomass-deconstructing capability of Streptomyces sp. SirexAA-E (ActE), an aerobic bacterium associated with the invasive pine-boring woodwasp Sirex noctilio. When grown on plant biomass, ActE secretes a suite of enzymes including endo- and exo-cellulases, CBM33 polysaccharide-monooxygenases, and hemicellulases. Genome-wide transcriptomic and proteomic analyses, and biochemical assays have revealed the key enzymes used to deconstruct crystalline cellulose, other pure polysaccharides, and biomass. The mixture of enzymes obtained from growth on biomass has biomass-degrading activity comparable to a cellulolytic enzyme cocktail from the fungus Trichoderma reesei, and thus provides a compelling example of high cellulolytic capacity in an aerobic bacterium.
The evolution of cellulose degradation was a defining event in the history of life. Without efficient decomposition and recycling, dead plant biomass would quickly accumulate and become inaccessible ...to terrestrial food webs and the global carbon cycle. On land, the primary drivers of plant biomass deconstruction are fungi and bacteria in the soil or associated with herbivorous eukaryotes. While the ecological importance of plant-decomposing microbes is well established, little is known about the distribution or evolution of cellulolytic activity in any bacterial genus. Here we show that in Streptomyces, a genus of Actinobacteria abundant in soil and symbiotic niches, the ability to rapidly degrade cellulose is largely restricted to two clades of host-associated strains and is not a conserved characteristic of the Streptomyces genus or host-associated strains. Our comparative genomics identify that while plant biomass degrading genes (CAZy) are widespread in Streptomyces, key enzyme families are enriched in highly cellulolytic strains. Transcriptomic analyses demonstrate that cellulolytic strains express a suite of multi-domain CAZy enzymes that are coregulated by the CebR transcriptional regulator. Using targeted gene deletions, we verify the importance of a highly expressed cellulase (GH6 family cellobiohydrolase) and the CebR transcriptional repressor to the cellulolytic phenotype. Evolutionary analyses identify complex genomic modifications that drive plant biomass deconstruction in Streptomyces, including acquisition and selective retention of CAZy genes and transcriptional regulators. Our results suggest that host-associated niches have selected some symbiotic Streptomyces for increased cellulose degrading activity and that symbiotic bacteria are a rich biochemical and enzymatic resource for biotechnology.
We report on a flux-integrated multi-differential measurement of charged-current muon neutrino scattering on argon with one muon and one proton in the final state using the Booster Neutrino Beam and ...MicroBooNE detector at Fermi National Accelerator Laboratory. The data are studied as a function of various kinematic imbalance variables and of a neutrino energy estimator, and are compared to a number of event generator predictions. We find that the measured cross sections in different phase-space regions are sensitive to nuclear effects. Our results provide precision data to test and improve the neutrino-nucleus interaction models needed to perform high-accuracy oscillation analyses. Specific regions of phase-space are identified where further model refinements are most needed.
Applying construal level theory, this study examined how social distance (thinking of self/children), front-of-package (FOP) claim type (nutrient/health/control), and perceived importance of eating ...healthily (low/high) impact consumer responses (attitudes/purchase intent) to healthier food products through an online experiment with 171 U.S. parents from low-to-mid socio-economic households. Participants were randomly assigned to view controlled images of healthier foods with packaging that bore different claim types for real and fictitious brands. Results revealed that when choosing for themselves, consumer attitudes were more positive when the healthier food package carried a nutrient (vs. health) claim, however, control claims received the most positive evaluations. When choosing for children, attitudes were more positive when the package carried a health (vs. nutrient/control) claim. Attitudes toward healthier foods were higher for consumers with high (vs. low) perceived importance of eating healthily when the package bore a nutrient claim, however, their attitudes did not significantly differ when the package bore a health/control claim. Purchase intent for healthier foods was higher for consumers with high (vs. low) perceived importance of healthy eating when shopping for self; whereas, when shopping for children, purchase intent did not significantly differ between consumers who varied in perceived importance of eating healthily.
Wave-based teleoperation has been previously attempted over the Internet, however, performance rapidly deteriorates with increasing delay. This paper focuses on the use of a modified Smith predictor, ...a Kalman filter and an energy regulator to improve the performance of a wave-based teleoperator. This technique is further extended for use over the Internet, where the time delay is varying and unpredictable. It is shown that the resulting system is stable even if there are large uncertainties in the model of the remote system (used in prediction). Successful experimental results using this technique for teleoperation in a master-slave arrangement over the Internet, where the control signal is streamed between Atlanta (Georgia) and Tokyo (Japan), are also given.
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