Ubiquitin-Specific Protease 25 Functions in Endoplasmic Reticulum-Associated Degradation

Endoplasmic Reticulum (ER)-associated degradation (ERAD) discards abnormal proteins synthesized in the ER. Through coordinated actions of ERAD components, misfolded/anomalous proteins are recognized, ubiquitinated, extracted from the ER and ultimately delivered to the proteasome for degradation. It is not well understood how ubiquitination of ERAD substrates is regulated. Here, we present evidence that the deubiquitinating enzyme Ubiquitin-Specific Protease 25 (USP25) is involved in ERAD. Our data support a model where USP25 counteracts ubiquitination of ERAD substrates by the ubiquitin ligase HRD1, rescuing them from degradation by the proteasome

Single-Turnover RING/U-Box E3-Mediated Lysine Discharge Assays

RING and U-box ubiquitin ligases promote ubiquitin (Ub) transfer by priming Ub-conjugated E2 in a closed conformation to optimize the thioester bond for nucleophilic attack by substrate lysine. Here, we describe a single-turnover lysine discharge assay for direct assessment of the activity of any RING/U-box E3-E2~Ub complex

Loss of ubiquitin E2 Ube2w rescues hypersensitivity of Rnf4 mutant cells to DNA damage

SUMO and ubiquitin play important roles in the response of cells to DNA damage. These pathways are linked by the SUMO Targeted ubiquitin Ligase Rnf4 that catalyses transfer of ubiquitin from a ubiquitin loaded E2 conjugating enzyme to a polySUMO modified substrate. Rnf4 can functionally interact with multiple E2s, including Ube2w, in vitro. Chicken cells lacking Rnf4 are hypersensitive to hyroxyurea, DNA alkylating drugs and DNA crosslinking agents, but this sensitivity is suppressed by simultaneous depletion of Ube2w. Cells depleted of Ube2w alone are not hypersensitive to the same DNA damaging agents. Similar results were also obtained in human cells. These data indicate that Ube2w does not have an essential role in the DNA damage response, but is deleterious in the absence of Rnf4. Thus, although Rnf4 and Ube2w functionally interact in vitro, our genetic experiments indicate that in response to DNA damage Ube2w and Rnf4 function in distinct pathways

Osteoinduction of Human Mesenchymal Stem Cells by Bioactive Composite Scaffolds without Supplemental Osteogenic Growth Factors

The development of a new family of implantable bioinspired materials is a focal point of bone tissue engineering. Implant surfaces that better mimic the natural bone extracellular matrix, a naturally nano-composite tissue, can stimulate stem cell differentiation towards osteogenic lineages in the absence of specific chemical treatments. Herein we describe a bioactive composite nanofibrous scaffold, composed of poly-caprolactone (PCL) and nano-sized hydroxyapatite (HA) or beta-tricalcium phosphate (TCP), which was able to support the growth of human bone marrow mesenchymal stem cells (hMSCs) and guide their osteogenic differentiation at the same time. Morphological and physical/chemical investigations were carried out by scanning, transmission electron microscopy, Fourier-transform infrared (FTIR) spectroscopy, mechanical and wettability analysis. Upon culturing hMSCs on composite nanofibers, we found that the incorporation of either HA or TCP into the PCL nanofibers did not affect cell viability, meanwhile the presence of the mineral phase increases the activity of alkaline phosphatase (ALP), an early marker of bone formation, and mRNA expression levels of osteoblast-related genes, such as the Runt-related transcription factor 2 (Runx-2) and bone sialoprotein (BSP), in total absence of osteogenic supplements. These results suggest that both the nanofibrous structure and the chemical composition of the scaffolds play a role in regulating the osteogenic differentiation of hMSCs

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1.

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field

A comparison of national estimates of obesity prevalence from the behavioral risk factor surveillance system and the national health and nutrition examination survey

Background: Obesity interventions are implemented at state or sub-state level in the United States (US), where only self-reported weight and height data for adults are available from the Behavioral Risk Factor Surveillance System (BRFSS). The prevalence estimates of overweight and obesity generated from self-reported weight and height from BRFSS are known to underestimate the true prevalence. However, whether this underestimation is consistent across different demographic groups has not been fully investigated. Methods: In this study, we compared the prevalence estimates of obesity (body mass index (BMI) 30 kg/m2) and overweight (BMI 25 kg/m2) in different demographic groups in the US from the National Health and Nutrition Examination Survey (NHANES) and BRFSS during 1999–2000. We also compared the rank orders of the obesity and overweight prevalence across different demographic groups from the two data sources. Results: Compared to NHANES, BRFSS underestimated the overall prevalence of obesity and overweight by 9.5 and 5.7 percentage points, respectively. The underestimation differed across different demographic groups: the underestimation of obesity and overweight prevalence was higher among women (13.1 and 12.2 percentage points, respectively) than among men (5.8 and -0.6 percentage points, respectively). The variation of underestimation was higher among men. A clear inverse association between educational attainment and obesity prevalence among non-Hispanic African American women was observed from BRFSS data. However, no such association was found from NHANES. While BRFSS can identify correctly the population with the highest obesity and overweight burden, it did not accurately rank the obesity and overweight prevalence across different demographic groups. Conclusion: Compared to NHANES, BRFSS disproportionately underestimates the prevalence of obesity and overweight across different gender, race, age, and education subgroups